Biomaterials in orthopaedics & trauma

70
Biomaterials in Orthopaedics & Trauma Zahid Askar FCPS(Ortho), FRCS (Ortho) Prof of Orthopaedics & Trauma Khyber Medical College, Peshawer

description

about the biomaterials used in orthopaedics and trauma and their biomechanics

Transcript of Biomaterials in orthopaedics & trauma

Page 1: Biomaterials  in orthopaedics & trauma

Biomaterials in Orthopaedics amp Trauma

Zahid Askar FCPS(Ortho) FRCS (Ortho)

Prof of Orthopaedics amp TraumaKhyber Medical College Peshawer

Study of Biomaterials

The physical and biological study of materials and their interactions with the biological environment

Increase use of biomaterials -Their interactions-Increasing Duration and stresses

Biomechanics

bull The science of movement of a living body including how muscles bones tendons and ligaments work together to produce movement

Response to Load

bull Force applied will lead to deformation and if continued beyond a certain point will lead to ultimate failure

bull The force ----- STRESS and Deformation is known as

STRAIN

Stress amp Strain

Stress- Force per unit areaUnits NMSq M or Pascal

Strain- Change in length per unit original length

Stress

Strain

Elastic Plastic

Yield Stress

Ultimate Stress

Breaking Stress

The path to failure

TENSILE STRENGTH ULTIMATE TENSILE STRENGTH - The maximum stress on the curve before breakage (NM2)

YIELD STRESS-

Point at which elastic behaviour changes to plastic behaviour

BREAKING STRESS

Point at which the substance failsbrakes

Youngrsquos modulus E

bull Stress Strain For elastic part of curve or the

slope of the elastic part of the curve SI unit = pascal (Pa or Nm2 or mminus1middotkgmiddotsminus2) megapascals (MPa or Nmm2) or

gigapascals (GPa or kNmm2)

bull DUCTILITY BRITTLENESS- The amount by which a material deforms (ie the strain that occurs) before it breaks

Represented by age elongation or reduction in cross section

bull HARDNESS- The ability of the surface of a material to withstand forces

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 2: Biomaterials  in orthopaedics & trauma

Study of Biomaterials

The physical and biological study of materials and their interactions with the biological environment

Increase use of biomaterials -Their interactions-Increasing Duration and stresses

Biomechanics

bull The science of movement of a living body including how muscles bones tendons and ligaments work together to produce movement

Response to Load

bull Force applied will lead to deformation and if continued beyond a certain point will lead to ultimate failure

bull The force ----- STRESS and Deformation is known as

STRAIN

Stress amp Strain

Stress- Force per unit areaUnits NMSq M or Pascal

Strain- Change in length per unit original length

Stress

Strain

Elastic Plastic

Yield Stress

Ultimate Stress

Breaking Stress

The path to failure

TENSILE STRENGTH ULTIMATE TENSILE STRENGTH - The maximum stress on the curve before breakage (NM2)

YIELD STRESS-

Point at which elastic behaviour changes to plastic behaviour

BREAKING STRESS

Point at which the substance failsbrakes

Youngrsquos modulus E

bull Stress Strain For elastic part of curve or the

slope of the elastic part of the curve SI unit = pascal (Pa or Nm2 or mminus1middotkgmiddotsminus2) megapascals (MPa or Nmm2) or

gigapascals (GPa or kNmm2)

bull DUCTILITY BRITTLENESS- The amount by which a material deforms (ie the strain that occurs) before it breaks

Represented by age elongation or reduction in cross section

bull HARDNESS- The ability of the surface of a material to withstand forces

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 3: Biomaterials  in orthopaedics & trauma

Biomechanics

bull The science of movement of a living body including how muscles bones tendons and ligaments work together to produce movement

Response to Load

bull Force applied will lead to deformation and if continued beyond a certain point will lead to ultimate failure

bull The force ----- STRESS and Deformation is known as

STRAIN

Stress amp Strain

Stress- Force per unit areaUnits NMSq M or Pascal

Strain- Change in length per unit original length

Stress

Strain

Elastic Plastic

Yield Stress

Ultimate Stress

Breaking Stress

The path to failure

TENSILE STRENGTH ULTIMATE TENSILE STRENGTH - The maximum stress on the curve before breakage (NM2)

YIELD STRESS-

Point at which elastic behaviour changes to plastic behaviour

BREAKING STRESS

Point at which the substance failsbrakes

Youngrsquos modulus E

bull Stress Strain For elastic part of curve or the

slope of the elastic part of the curve SI unit = pascal (Pa or Nm2 or mminus1middotkgmiddotsminus2) megapascals (MPa or Nmm2) or

gigapascals (GPa or kNmm2)

bull DUCTILITY BRITTLENESS- The amount by which a material deforms (ie the strain that occurs) before it breaks

Represented by age elongation or reduction in cross section

bull HARDNESS- The ability of the surface of a material to withstand forces

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 4: Biomaterials  in orthopaedics & trauma

Response to Load

bull Force applied will lead to deformation and if continued beyond a certain point will lead to ultimate failure

bull The force ----- STRESS and Deformation is known as

STRAIN

Stress amp Strain

Stress- Force per unit areaUnits NMSq M or Pascal

Strain- Change in length per unit original length

Stress

Strain

Elastic Plastic

Yield Stress

Ultimate Stress

Breaking Stress

The path to failure

TENSILE STRENGTH ULTIMATE TENSILE STRENGTH - The maximum stress on the curve before breakage (NM2)

YIELD STRESS-

Point at which elastic behaviour changes to plastic behaviour

BREAKING STRESS

Point at which the substance failsbrakes

Youngrsquos modulus E

bull Stress Strain For elastic part of curve or the

slope of the elastic part of the curve SI unit = pascal (Pa or Nm2 or mminus1middotkgmiddotsminus2) megapascals (MPa or Nmm2) or

gigapascals (GPa or kNmm2)

bull DUCTILITY BRITTLENESS- The amount by which a material deforms (ie the strain that occurs) before it breaks

Represented by age elongation or reduction in cross section

bull HARDNESS- The ability of the surface of a material to withstand forces

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 5: Biomaterials  in orthopaedics & trauma

bull Force applied will lead to deformation and if continued beyond a certain point will lead to ultimate failure

bull The force ----- STRESS and Deformation is known as

STRAIN

Stress amp Strain

Stress- Force per unit areaUnits NMSq M or Pascal

Strain- Change in length per unit original length

Stress

Strain

Elastic Plastic

Yield Stress

Ultimate Stress

Breaking Stress

The path to failure

TENSILE STRENGTH ULTIMATE TENSILE STRENGTH - The maximum stress on the curve before breakage (NM2)

YIELD STRESS-

Point at which elastic behaviour changes to plastic behaviour

BREAKING STRESS

Point at which the substance failsbrakes

Youngrsquos modulus E

bull Stress Strain For elastic part of curve or the

slope of the elastic part of the curve SI unit = pascal (Pa or Nm2 or mminus1middotkgmiddotsminus2) megapascals (MPa or Nmm2) or

gigapascals (GPa or kNmm2)

bull DUCTILITY BRITTLENESS- The amount by which a material deforms (ie the strain that occurs) before it breaks

Represented by age elongation or reduction in cross section

bull HARDNESS- The ability of the surface of a material to withstand forces

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 6: Biomaterials  in orthopaedics & trauma

Stress amp Strain

Stress- Force per unit areaUnits NMSq M or Pascal

Strain- Change in length per unit original length

Stress

Strain

Elastic Plastic

Yield Stress

Ultimate Stress

Breaking Stress

The path to failure

TENSILE STRENGTH ULTIMATE TENSILE STRENGTH - The maximum stress on the curve before breakage (NM2)

YIELD STRESS-

Point at which elastic behaviour changes to plastic behaviour

BREAKING STRESS

Point at which the substance failsbrakes

Youngrsquos modulus E

bull Stress Strain For elastic part of curve or the

slope of the elastic part of the curve SI unit = pascal (Pa or Nm2 or mminus1middotkgmiddotsminus2) megapascals (MPa or Nmm2) or

gigapascals (GPa or kNmm2)

bull DUCTILITY BRITTLENESS- The amount by which a material deforms (ie the strain that occurs) before it breaks

Represented by age elongation or reduction in cross section

bull HARDNESS- The ability of the surface of a material to withstand forces

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 7: Biomaterials  in orthopaedics & trauma

Stress

Strain

Elastic Plastic

Yield Stress

Ultimate Stress

Breaking Stress

The path to failure

TENSILE STRENGTH ULTIMATE TENSILE STRENGTH - The maximum stress on the curve before breakage (NM2)

YIELD STRESS-

Point at which elastic behaviour changes to plastic behaviour

BREAKING STRESS

Point at which the substance failsbrakes

Youngrsquos modulus E

bull Stress Strain For elastic part of curve or the

slope of the elastic part of the curve SI unit = pascal (Pa or Nm2 or mminus1middotkgmiddotsminus2) megapascals (MPa or Nmm2) or

gigapascals (GPa or kNmm2)

bull DUCTILITY BRITTLENESS- The amount by which a material deforms (ie the strain that occurs) before it breaks

Represented by age elongation or reduction in cross section

bull HARDNESS- The ability of the surface of a material to withstand forces

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 8: Biomaterials  in orthopaedics & trauma

The path to failure

TENSILE STRENGTH ULTIMATE TENSILE STRENGTH - The maximum stress on the curve before breakage (NM2)

YIELD STRESS-

Point at which elastic behaviour changes to plastic behaviour

BREAKING STRESS

Point at which the substance failsbrakes

Youngrsquos modulus E

bull Stress Strain For elastic part of curve or the

slope of the elastic part of the curve SI unit = pascal (Pa or Nm2 or mminus1middotkgmiddotsminus2) megapascals (MPa or Nmm2) or

gigapascals (GPa or kNmm2)

bull DUCTILITY BRITTLENESS- The amount by which a material deforms (ie the strain that occurs) before it breaks

Represented by age elongation or reduction in cross section

bull HARDNESS- The ability of the surface of a material to withstand forces

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 9: Biomaterials  in orthopaedics & trauma

TENSILE STRENGTH ULTIMATE TENSILE STRENGTH - The maximum stress on the curve before breakage (NM2)

YIELD STRESS-

Point at which elastic behaviour changes to plastic behaviour

BREAKING STRESS

Point at which the substance failsbrakes

Youngrsquos modulus E

bull Stress Strain For elastic part of curve or the

slope of the elastic part of the curve SI unit = pascal (Pa or Nm2 or mminus1middotkgmiddotsminus2) megapascals (MPa or Nmm2) or

gigapascals (GPa or kNmm2)

bull DUCTILITY BRITTLENESS- The amount by which a material deforms (ie the strain that occurs) before it breaks

Represented by age elongation or reduction in cross section

bull HARDNESS- The ability of the surface of a material to withstand forces

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 10: Biomaterials  in orthopaedics & trauma

Youngrsquos modulus E

bull Stress Strain For elastic part of curve or the

slope of the elastic part of the curve SI unit = pascal (Pa or Nm2 or mminus1middotkgmiddotsminus2) megapascals (MPa or Nmm2) or

gigapascals (GPa or kNmm2)

bull DUCTILITY BRITTLENESS- The amount by which a material deforms (ie the strain that occurs) before it breaks

Represented by age elongation or reduction in cross section

bull HARDNESS- The ability of the surface of a material to withstand forces

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 11: Biomaterials  in orthopaedics & trauma

bull DUCTILITY BRITTLENESS- The amount by which a material deforms (ie the strain that occurs) before it breaks

Represented by age elongation or reduction in cross section

bull HARDNESS- The ability of the surface of a material to withstand forces

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 12: Biomaterials  in orthopaedics & trauma

bull The Yield Point = marks the onset of plastic deformation

bull Plastic Region = Beyond the yield point irreversible (plastic) deformation takes place

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 13: Biomaterials  in orthopaedics & trauma

Elastic Modulus of Common Materials in Orthopaedics

bull Stainless Steel 200bull Titanium 100bull Cortical Bone 7-21bull Bone Cement 25-35bull Cancellous Bone 07-49bull UHMWPE 14-42

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 14: Biomaterials  in orthopaedics & trauma

Relative values of Youngs modulus of elasticity (numbers correspond to numbers on illustration to right)1Ceramic (Al2O3)2Alloy (Co-Cr-Mo)3Stainless steel4Titanium 5Cortical bone6Matrix polymers7PMMA8Polyethylene9Cancellous bone10Tendon ligament11Cartilage

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 15: Biomaterials  in orthopaedics & trauma

Bone Mechanicsbull Bone Density

ndash Subtle density changes greatly changes strength and elastic modulus

bull Density changesndash Normal agingDiseaseUseDisuse

Figure from Browner et al Skeletal Trauma 2nd Ed Saunders 1998

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 16: Biomaterials  in orthopaedics & trauma

Bone Biomechanics

bull Bone is anisotropic - its modulus is dependent upon the direction of loadingBone Type Load Type

Elastic Modulus

(times10 E9 Nm2)

Ultimate Stress

(times 10 E6 Nm2)Cortical Tension 114-191 107-146

Compression 151-197 156-212Shear 73-82

Cancellous Tension ~02-50 ~3-20Compression 01-3 15-50Shear 66 +- 17

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 17: Biomaterials  in orthopaedics & trauma

Material UltimateStrength

Tensile (MPa)

UltimateStrength

Compressive(MPa)

YieldStrength

02 Offset(MPa)

ElasticModulus

(MPa)

Cortical bone 100 175 80 15000

Cancellous bone 2 3 1000

Polyethylene 40 20 20 1000

PTFE Teflon 25 500

Acrylic bone cement 40 80 2000

Stainless steel (316 L) (annealed)

gt500 gt200 200000

Titanium (Al-4V) (alloy F 136)

900 800 100000

Cobalt chrome (wrought cold work)

1500 1000 230000

Super alloys (CoNiMo)

1800 1600 230000

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 18: Biomaterials  in orthopaedics & trauma

ORTHOPAEDIC BIOMATERIALS

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 19: Biomaterials  in orthopaedics & trauma

BIOMATERIAL -A non-viable material used in a medical device intended to interact with biological systems

State of Mutual Coexistance between a Biomaterial and the Physiological Environment Such as Neither has an Undesirable Effect on the Other

BIOCOMPATIBILITY

No host response to the materialBIOINERT

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 20: Biomaterials  in orthopaedics & trauma

Ideal Biomaterial

bull Suitable mechanical properties to fulfil its intended function

bull Must not corrode in biologic environmentbull Must not release potentially harmful

degradation by-products locally and systemically

bull To permit fabrication in the optimum design configuration

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 21: Biomaterials  in orthopaedics & trauma

Ideal Biomaterial

bull Be like the natural and mimic its biomechanical properties

bull Not elicit a response- Bioinertbull Elicit a favourable response- Biocompatiblebull Economical and Reproducible

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 22: Biomaterials  in orthopaedics & trauma

Implants- Uses

bull Helpbull Substitution

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 23: Biomaterials  in orthopaedics & trauma

1048698

Mechanical Properties of Bone

bull Youngrsquos Modulus(E) 170 GNm2bull Ultimate Tensile Strength (UTS)

0132GNm2bull Compressive Strength(σc) 0192 GNm2bull Shear Modulus(K) 201 GNm2bull Poissonrsquos Ratio(ν) 03

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 24: Biomaterials  in orthopaedics & trauma

Materials used in Orthopaedicsbull Metals -Stainless Steel 316L -Co-Cr-Mo -Ti-6AL-4VCeramics- AluminaZirconiumPolymers- UHWPE PMMA SiliconesPEEK

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 25: Biomaterials  in orthopaedics & trauma

Stainless steel-(316L)

bull Iron- 60 bull Chromium- 20 bull Nickel- 14 bull Molybdenum- 3bull Carbon- 003 bull Manganese SiliconPS- 3

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 26: Biomaterials  in orthopaedics & trauma

Functions

bull Ironbull ChromiumNickel

Molybdenum-bull Carbon-bull Manganese Silicon -

bull Strengthbull Corrosionbull Strengthbull Manufacturing

Problems

The chromium forms an oxide layer when dipped in nitric acid to reduce corrosion and the molybdenum increases this protection when compared to other steels

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 27: Biomaterials  in orthopaedics & trauma

Stainless Steel

bull Strong bull Cheap bull Relatively ductile bull Relatively biocompatible

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 28: Biomaterials  in orthopaedics & trauma

bull High Youngrsquos modulus ndash 200 GPascals (10 that of bone)

bull Leads to stress shielding of surrounding bone which can cause bone resorption

bull susceptible to corrosion

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 29: Biomaterials  in orthopaedics & trauma

Titanium and its alloys

bull Ti 6AL-4V ELI (Grade 23) bull Ti 6Al-4V (Grade 5) bull Excellent resistance to corrosion bull Youngrsquos modulusbull Stronger than stainless steels bull MRI complaint

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 30: Biomaterials  in orthopaedics & trauma

Disadvantagesopoor resistance to

wear o Can be brittle ie less

ductilegenerates more

metal debris than cobalt chrome

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 31: Biomaterials  in orthopaedics & trauma

Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)

bull COBALT-BASED ALLOYSTwo main types of cobalt-based alloys

bull A cast alloy bull A wrought alloy bull Also known as Vitallium (or in Britain Stellite) is

often applied to both alloys

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 32: Biomaterials  in orthopaedics & trauma

Advantagesstrength and corrosion resistance

high abrasion resistance Superior to stainless steel

DisadvantagesMore expensive to

manufacturecannot be

contoured at the time of surgery

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 33: Biomaterials  in orthopaedics & trauma

USES

bull Usually for bearing surfacesbull THRbull Metal-on-metal devices

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 34: Biomaterials  in orthopaedics & trauma

Material Elastic Yield UTensile Modulus Strength Strength

(GNm2) (MNm2) (MNm2)

316L 200 795 965 Co-Cr-Mo 210 950 1450Ti-6Al-4V 105 895 1173

Mechanical Properties of Orthopaedic Alloys

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 35: Biomaterials  in orthopaedics & trauma

POLYMETHYLMETHACRYLATE (PMMA)

bull Prepolymerized methylmethacrylate( powder)bull Liquid monomer bull Exothermic Reactionbull 10 min at 23 0 C bull 60 0 C in the center of the material and 40 0 C

at the surfacebull A grouting agentbull Good in compressionbull Hard but brittle

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 36: Biomaterials  in orthopaedics & trauma

bull 2 component materialbull Powder

bull polymerbull benzoyl peroxide (initiator)bull barium sulfate (radio-opacifier)

bull Liquidbull monomerbull DMPT (accelerator) NN-Dimethyl

-p-toluidinebull hydroquinone (stabilizer)

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 37: Biomaterials  in orthopaedics & trauma

The curing process is divided into 4 stages a) mixing

The mixing can be done by hand or with the aid of centrifugation or vacuum technologiesb) stickywaitingc) working and d) hardening

It is recommended that the unopened cement components are stored at 73 degF (23 degC) for a minimum of 24 h before use

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 38: Biomaterials  in orthopaedics & trauma

First generation cementing technique1)- Hand mixing 2)-Minimal preparation of the femoral canal 2)-Digital application of cement

Second generation cementing techniques1)-Preparation packing and drying of the femoral canal 2)-Distal cement restrictor 3)-Pulsatile irrigation 4)-Retrograde insertion of cement with a cement gun

Third generation cementing techniques1)-Cement is prepared using a vacuum-centrifugation( reduces porosity) 2)-The femoral canal is irrigated with pulsatile lavage and then packed with adrenaline soaked swabs 3)-Insertion and pressurisation of the cement in a retrograde fashion

Fourth generation cementing techniques Insertion using distal and proximal centralizers to ensure an even cement mantle (4th generation)

Generations of Cementing Technique

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 39: Biomaterials  in orthopaedics & trauma

First Second Third FourthHand Mix with Spatula Hand mix with cement

gunVacuum centrifuge Mixing

Third with

Leave Cancellous Bone

Remove bone from the endoesteal surface

Remove bone from the endoesteal surface

PROXIMAL amp DISTAL CENTRALISER

Vent Femoral canal Distal Cement restrictor

Distal Cement restrictor

Minimal canal Preparation

Brush Pulsatile irrigation

Brush Pulsatile irrigation

Irrigate amp Suck femoral canal

Irrigation Pack and dry

Irrigation Pack with adrenaline gauze and dry

Manual Insertion of the Dough

Cement Gun Insertion Cement Gun Insertion amp pressuriation

Manual Insertion of the stem

Manual Position of the Stem

Manual Position of the Stem

FEmoral stem shapes Improved Femur Design

Surface texturing and contouring

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 40: Biomaterials  in orthopaedics & trauma

USESused for fixation and load distribution in conjunction with orthopeadic implantsFunctions by interlocking with bone

bull May be used to fill tumor defects and minimize local recurrence

Advantages1)-Reaches ultimate strength at 24 hours2)-Strongest in compression3)-Youngs modulus between cortical and cancellous bone

Disadvantagesbull poor tensile and shear strengthbull insertion can lead to

dangerous drop in blood pressure

bull failure often caused by microfracture and fragmentation

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 41: Biomaterials  in orthopaedics & trauma

Ceramic

bull A ceramic material may be defined as any inorganic crystalline material compounded of a metal and a non-metal

bull Aluminabull Zirconia

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 42: Biomaterials  in orthopaedics & trauma

Advantages1)-best wear characteristics with PE2)-high compressive strength

Disadvantages1)-typically brittle low fracture toughness 2)-high Youngs modulus3)-Low tensile strength4)-Poor crack resistance characteristics

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 43: Biomaterials  in orthopaedics & trauma

Ultra-high-molecular-weight polyethylene ( UHMWPE)

bull Sterilised by Gamma irradiation bull Increases polymer chain cross-linking

which improves wear characteristicsbull Decreases fatigue and fracture resistance

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 44: Biomaterials  in orthopaedics & trauma

Advantages1)-Tough2)-Ductile3)-Resilient4)-Resistant to wear

Disadvantages1)-Susceptible to abrasion2)-Wear usually caused by third body inclusions3)-Thermoplastic (may be altered by extreme temperatures)weaker than bone in tension

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 45: Biomaterials  in orthopaedics & trauma

Silicones

ndash Polymers that are often used for replacement in non-weight bearing joints

ndash Disadvantagesbull poor strength and wear capability responsible for

frequent synovitis

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 46: Biomaterials  in orthopaedics & trauma

Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family used in engineering applications

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger) such as temperature change

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 47: Biomaterials  in orthopaedics & trauma

Polyetheretherketone or PEEK was originally developed in the late 1970s by the US aerospace industry which was taken by its properties of stability at high temperatures and thus its potential for high-load high-temperature applications In the late 1990s a highly pure and implantable grade of PEEK known as PEEK-OPTIMA was commercialised by Invibio Biomaterial Solutions and subsequently embraced by the medical device industry

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 48: Biomaterials  in orthopaedics & trauma

Angle stable interlocking screws which have a sleeve that expands to fit tightly within the nail interlock to improve construct stability of intramedullary nailing of distal tibia fractures

Angle stable interlocking screws

Horn J Linke B Houmlntzsch D Gueorguiev B Schwieger K Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures A biomechanical studyInjury 200940[7]767-771)

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 49: Biomaterials  in orthopaedics & trauma

How do Materials fail

bull Corrosionbull Fatiguebull Wear

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 50: Biomaterials  in orthopaedics & trauma

Corrosion

bull A chemical reaction in which material is removed from an object

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 51: Biomaterials  in orthopaedics & trauma

Galvanic corrosion- due to two different metals being used eg stainless steel screws and titanium plate

Stress corrosion- The presence of a crack due to stress

Crevice corrosion fretting occurs where components have a relative movement against one another

Pit corrosion- A local form of crevice corrosion due to abrasion produces a pit

Types Of Corrosion

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 52: Biomaterials  in orthopaedics & trauma

Fatigue-

bull Progressive failure of a material due to the application of cyclical stresses below the ultimate stress of the material causing failure

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 53: Biomaterials  in orthopaedics & trauma

bull All implants will eventually break if the fracture does not heal

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 54: Biomaterials  in orthopaedics & trauma

Basic Biomechanics

bull Load to Failurendash Continuous application

of force until the material breaks (failure point at the ultimate load)

ndash Common mode of failure of bone and reported in the implant literature

bull Fatigue Failurendash Cyclical sub-

threshold loading may result in failure due to fatigue

ndash Common mode of failure of orthopaedic implants and fracture fixation constructs

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 55: Biomaterials  in orthopaedics & trauma

Wear

bull The removal of material from solid surfaces by mechanical action

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70
Page 56: Biomaterials  in orthopaedics & trauma

Interfacial wear - when bearing surfaces come into direct contact can occur in 2 ways 1 Adhesive wear when surface fragments adhere to each other and are torn from the surface during sliding 2 Abrasive wear when a soft material is scraped by a harder material

Third Body Wear

Corrosion Wear

Fatigue Wear due to accumulation of microscopic damage within the bearing material due to repetitive cyclical stressing

Types Of Wear

  • Biomaterials in Orthopaedics amp Trauma
  • Study of Biomaterials
  • Biomechanics
  • Response to Load
  • Slide 5
  • Stress amp Strain
  • Slide 7
  • The path to failure
  • Slide 9
  • Youngrsquos modulus E
  • Slide 11
  • Slide 12
  • Slide 13
  • Elastic Modulus of Common Materials in Orthopaedics
  • Slide 15
  • Slide 16
  • Slide 17
  • Bone Mechanics
  • Slide 19
  • Bone Biomechanics
  • Slide 21
  • ORTHOPAEDIC BIOMATERIALS
  • Slide 23
  • Ideal Biomaterial
  • Ideal Biomaterial
  • Implants- Uses
  • 1048698 Mechanical Properties of Bone
  • Materials used in Orthopaedics
  • Stainless steel-(316L)
  • Functions
  • Stainless Steel
  • Slide 32
  • Titanium and its alloys
  • Slide 34
  • Slide 35
  • Cobalt-Chromium-Molybdenum alloy (Co-Cr-Mo)
  • Slide 37
  • Slide 38
  • USES
  • Slide 40
  • Mechanical Properties of Orthopaedic Alloys
  • POLYMETHYLMETHACRYLATE (PMMA)
  • Slide 43
  • Slide 44
  • Slide 45
  • Slide 46
  • Slide 47
  • Slide 48
  • Slide 49
  • Ceramic
  • Slide 51
  • Slide 52
  • Ultra-high-molecular-weight polyethylene ( UHMWPE)
  • Slide 54
  • Silicones
  • Slide 56
  • Slide 57
  • Slide 58
  • Slide 59
  • Slide 60
  • Slide 61
  • Slide 62
  • How do Materials fail
  • Corrosion
  • Slide 65
  • Fatigue-
  • Slide 67
  • Basic Biomechanics
  • Wear
  • Slide 70