45940402 R3 Design Rationale US - Smith+Nephe · 4 0 0.5 1 1.5 2 2.5 3 Wear factor x10-6 (mm 3 /Nm)...

R3™Acetabular System

*smith&nephewDesign Rationale

Contents

Introduction 2

Advanced bearing capabilities Modular resurfacing 4

Ceramic-on-ceramic 6

OXINIUM™ alloy-on-XLPE 10

Stability Larger head sizes 12

Locking mechanism 14

STIKTITE™ Porous Coating 16

Instrumentation 18

Modular resurfacing available after FDA approval.

We would like to thank the following surgeons for their participation as part of the R3™ Acetabular System design team:

Robert Barrack, MDSt. Louis, Missouri

Robert Bourne, MDLondon Health Sciences CenterLondon, Ontario, Canada

Jonathan Garino, MDUniversity of Pennsylvania School of MedicinePhiladelphia, Pennsylvania

Wayne M. Goldstein, MDClinical Professor of OrthopaedicsUniversity of Illinois at ChicagoIllinois Bone and Joint InstituteChicago, Illinois

Richard Kyle, MDMinneapolis, Minnesota

Stephen J. McMahon MB BS,FRACS(Orth), FA(Orth)ASenior Lecturer Monash UniversityMalabar Orthopaedic ClinicMelbourne, Australia

John L. Masonis, MDOrthoCarolinaHip & Knee CenterCharlotte, North Carolina

Henrik Malchau, MDAssociate Professor Harvard Medical SchoolCodirector The Harris Orthopaedic Biomechanics and Biomaterials LaboratoryMassachusetts General HospitalBoston, Massachusetts

Michael Ries, MDUniversity of CaliforniaSan Francisco, California

Cecil Rorabeck, MD Professor of Orthopaedic Surgery University of Western OntarioLondon, Ontario, Canada

Van Paul Stamos, MDIllinois Bone and Joint InstituteGlenview, IllinoisClinical Instructor of Orthopaedic SurgeryNorthwestern University Medical SchoolChicago, Illinois

2

Polished inner surface to minimize backside wear

NO HOLE & THREE HOLE hemispherical shell offering

STIKTITE™ Porous Coating for enhanced scratch-fit feel and enhanced initial fixation

Modular resurfacing*offered with the clinically proven BHR™ hip metallurgy and clearances*available after FDA approval

General features

R3volution in motion

The R3™ Acetabular System combined with the Smith & Nephew portfolio of hip stems provides the most advanced hip replacement system with:

•Widest range of advanced bearing options

• Excellent primary stability

• Flexible instrumentation

3

Ceramic-on-ceramic*offered in BIOLOX® Forte*available after FDA approval

XLPE offered in 0 & 20 degree and in 0 & 20 degree +4mm lateralized options

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As-cast (high carbide) Low carbide

Advanced bearing surfaces: modular resurfacing

R3™ modular resurfacing advantage

Superior metallurgy and optimal clearances, also used in the clinically proven, highly successful, world-leading BIRMINGHAM HIP™ Resurfacing System, provide the Smith & Nephew R3 modular resurfacing system superior performance compared to similar competitive systems.

The R3 modular resurfacing and the BHR system utilize high-carbide cobalt chrome in the as-cast micro-structural condition, providing superior wear resistance.1,2,3

Recent publications have highlighted the difference in wear rates of heat-treated casting versus as-cast. The cumulative linear wear rate data showed substantially more wear with the heat-treated metallurgy than with as-cast devices.3

As-cast CoCr has performed significantly better than the thermally treated CoCr by generating a lower wear factor. Additional heat treatments of the as-cast metal deteriorates the metallurgy by depleting the carbide content. This leads to a less durable bearing surface and increased wear.

Microabrasive pin-on-disc wear test using as-cast and heat-treated cobalt chrome alloy

Typical microstructure of As-cast modular resurfacing

Typical microstructure of a heat-treated modular resurfacing device


5

Advanced bearing surfaces: modular resurfacing

The importance of modular resurfacing clearances

Studies have shown that the modular resurfacing design of the BIRMINGHAM HIP™ implant offers improved wear properties.4 An essential part of that design is a smaller femoral head within a larger acetabular cup, with an optimized radial clearance. This clearance provides a space in which viscous fluids – blood and synovial fluid – can lubricate the movement of the head within the cup.

The system’s optimized radial clearance draws lubricating fluids (viscous entrainment) extremely well – dramatically reducing bearing friction and inhibiting long-term wear properties.

The significance of radial clearanceRadial clearance is the space defined by the difference between the radius of the femoral head and the radius of the cup. This dynamic space (a converging wedge) between the cup and the head draws and transports fluid between the components, lubricating the system. When fluid is present, there is less friction between the metallic head and consequently, far less wear.

Generation of fluid film

At rest

Radial clearance = R2-R1

R2

R1

In motion

Viscous entrainment

Radial clearance


6

R3™ ceramic-on-ceramic bearing couple

Ceramic-on-ceramic bearing surfaces have been used worldwide in total hip replacement for more than 30 years. Renewed interest in ceramics as an alternate bearing surface has been driven by the following:

• New technology

• Improved manufacturing processes and standards

• New designs

This translates into improvements in the following:

• Mechanical and physical properties

• Wear characteristics

• Optimized biocompatibility

• Reliability expected by today’s more active patients

Due to the reduced grain size, ceramic components are harder than before. That has led to wear rates as low as 0.001mm/year.5,6

Impingement in ceramic bearing systems increases wear and decreases implant longevity. The improved design of R3 ceramic acetabular components:

• Reduces the effects of impingement

• Enhances wear and durability by utilizing liners that sit flush with the shell face

Advanced bearing surfaces: ceramic-on-ceramic

Ceramic-on-ceramic available after FDA approval.

7

The R3™ system’s ceramic design is an assembled combination of:

• A ceramic component made from orthopaedic industry standard material, BIOLOX® Forte

• A precision-machined support ring made of a Titanium alloy (Ti6A1AV) that is commonly used in orthopaedic implants.

BIOLOX® ForteBurst strength has improved from BIOLOX® (400 MPa) to BIOLOX® Forte (580 MPa).5,6 The R3 system’s design of BIOLOX® Forte with the titanium band has a burst load of over 91KN.7

BIOLOX® Forte, introduced in 1995, is the only ceramic material currently approved in the US for ceramic-on-ceramic articulation.



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Titanium support ring for added strengthThe unique feature about R3 ceramic liners is that they come with a titanium support ring around the periphery of the liner. The support ring and ceramic liner are precisely assembled utilizing a cold pressing process, which assures that the material properties of the ceramic and titanium are not altered.

The support ring offers greater protection against chipped edges and tensile forces for the ceramic insert that result in high fatigue and burst performance for insert assembly. Lab tests have shown that the burst strength of these liners is significantly higher than that of traditional ceramic liners with no band.7 Based on these test results, it can be hypothesized that these liners with titanium band would reduce the incidence of fracture of the ceramic liners.

Burs

t str

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N)

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BIOLOX® Forte without ring BIOLOX® Forte with ring

R3™ ceramic-on-ceramic bearing couple (cont.)



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Titanium band


101101001001101010111011011111111111

Advanced bearing surfaces: OXINIUM™ alloy-on-XLPE

R3™ system with OXINIUM alloy is the most advanced bearing option available

OXINIUM alloy with 10 Mrad XLPE shows superior wear characteristics for bearing couples with polyethylene.8,10

Wear reduction of standard bearing vs. advanced bearings

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Non-detectable

28mm CoCr/non-crosslinkpoly

28mm CoCr/XLPE (5Mrad)

28mm CoCr/XLPE (10Mrad)

32mm OxZr/XLPE (10Mrad)

Line

r pen

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/yr)

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CoCr-on-Poly97%9 wear reduction

modular resurfacing

OXINIUM is an Oxidized Zirconium alloy (97.5% Zirconium and 2.5% Niobium) with a transformed ceramic surface providing the wear performance of ceramics and the strength of metals. This provides all of the benefits of ceramic and metal bearing technology. OXINIUM material is especially useful for nickel-sensitive patients. OXINIUM material is an award winning, clinically proven advanced bearing material that is designed for active patients.

OXINIUM material along with 10 Mrad XLPE provides the wear performance of hard bearings along with the intraoperative options of hard-on-soft bearing.

OXINIUM material has a clinical history of more than 10 years. Over 190,000 components have been implanted successfully to date. Impressive clinical wear performance of OXINIUM heads was supported by an RSA clinical study from Dr. Bo Nivbrant.8

98%10,11 wear reductionOXINIUM™-on-XLPE

99%9 wear reductionceramic-on-ceramic

Ceramic-on-ceramic and modular resurfacing available after FDA approval.

11

Advanced bearing surfaces: OXINIUM™ alloy-on-XLPE

R3™ system with OXINIUM alloy-on-XLPE

The Smith & Nephew 10 Mrad, fully annealed XLPE is the only crosslinked polyethylene proven to produce less volume of wear debris particles in all size ranges.11,12 Less wear debris provides a reduced chance for osteolysis.

All currently marketed crosslinked poly indicates a significant improvement in the volume of wear debris, which would lead one to assume all crosslinked poly is the same. However, Smith & Nephew investigated more closely and found that not all crosslinked poly minimizes the amount of particles generated. Because the wear particles of crosslinked poly can be smaller in size than with UHMWPE, it is possible to reduce the volume but actually increase the number of particles.11,12 Even though there are questions about some crosslinked poly increasing the number of particles, many surgeons are adopting the use of these materials in most of their more active patients.

The Smith & Nephew crosslinked polyethylene significantly reduces the number of particles generated. The gravimetric wear rate of R3 XLPE is not measurable in a hip simulator, but the number of particles generated is reduced by 80% compared to traditional CoCr on conventional poly bearing.13

Standard unirradiated polyethylene

5 Mrad irradiated crosslinked poly, showing an increase in the number of particles in conjunction with a decrease in average size

High magnification images of captured particles

10 Mrad irradiated R3 XLPE showing a reduction in total number of particles

12

Stability: head/shell ratios

Optimized head/shell ratios

Use of larger diameter femoral heads has been clinically reported to decrease the probability of dislocation in patients.14,15,16,17

• Large heads increase the ROM of the joint

• Large heads reduce the incidence of neck impingement with soft tissue or the edge of the shell

13

With the R3™ Acetabular System, surgeons have the option of using larger head sizes in smaller acetabular shells:

• R3 ceramic-on-ceramic acetabular system: 36mm ceramic head with a 52mm cup size

• R3 modular resurfacing acetabular system: 38mm metal head with a 50mm cup size

• R3 OXINIUM™ alloy-on-XLPE acetabular system: 36mm head in a 52mm cup size

R3 liner offering chart

XLPE Ceramic Metal

Cup size 22 28 32 36 32 36 38 40 42 44 46 48 50 52 54

40

42

44

46

48

50

52

54

56

58

60

62

64

66/68

Greater jump distance equals greater stability

Larger diameter heads increase the jump distance and reduce the dislocation risk.

Stability: head/shell ratios

Ceramic-on-ceramic and modular resurfacing available after FDA approval.

14

R3™ locking mechanism for secure liner stability

R3 locking mechanism design features:

• Locking taper that supports metal and ceramic liners

• Double-channel lock design that provides axial stability for poly liners

• 12 large anti-rotational tabs on the poly liner that provide rotational stability

Intraoperative adjustments to the liner position may be performed with true confidence. Independent researchers confirm that in some competitive locking designs, the liner can be significantly damaged by extraction, which prohibits liner repositioning.18 Laboratory tests of the R3 locking mechanism have shown it withstands consecutive insertions of the same liner without damaging its locking integrity.

Anti-rotation tabs

Constrained liner* locking mechanism

*available after FDA cleared

XLPE locking mechanism

Hard-bearing taper locking mechanism

Stability: locking mechanism


15

Push-out and torque-to-failure tests of the R3™ locking mechanism demonstrate that it offers the benefit of a secure and stable liner. The R3 lock can withstand over 1112N of push-out force in any of its liner options and over 40 N-m of torque.

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REFLECTION™R3

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REFLECTIONR3

Maximum predicted in-vivo torque = 2.4 N-m

Stability: locking mechanism

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Enhanced stability and fixation with STIKTITE Porous Coating

Utilizing STIKTITE coating on the R3™ Acetabular Shells allows for a true scratch-fit feel during the shell seating and a clinically proven in-growth surface for long-term implant success.20

Stability: STIKTITE™ Porous Coating

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0.0

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1.5Cancellous bone

Cortical bone

Fric

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ffic

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Trabecular metal, EDM-shaped

Trabecular metal, net-shaped

STIKTITE coating

STIKTITE coating is a sintered three-dimensional asymmetric titanium powder that has a porosity of about 60%. Increased porosity allows for potentially greater bone ingrowth, which can enhance long-term fixation and implant stability. STIKTITE coating provides enhanced initial mechanical stability, which is particularly important in damaged or less biologically active bone. The average pore size of STIKTITE coating (200 μm) is within the 100– to 500–μm range for optimal bone ingrowth.

Frictional coefficients of bone ingrowth structures against cancellous and cortical bone (n=96 to 100)21

STIKTITE Porous Coating demonstrated a higher coefficient of friction compared to trabecular metal when tested by the same method.16 The mean coefficient of friction for STIKTITE coating was higher than that of trabecular metal against both cancellous and cortical bone. These results indicate that STIKTITE coating should have superior friction, scratch-fit feel and initial fixation stability as compared to trabecular metal.

Stability: STIKTITE™ Porous Coating

18

Instrumentation

Preassembled alignment ring on all hard bearing liners.

Alignment ring allows for easy placement of the hard bearing liner in the shell. The liner impactor can then be inserted through an opening in the alignment ring and the liner can be seated with an impaction force.

Upon impaction the ring will disengage and remain on the liner impactor for later disposal.

The hard bearing liner is now perfectly seated in the shell.

Streamlined instrumentation improves surgical efficiency

This seemingly simple technique is a very effective way of precisely placing the hard bearing liners inside the shell without the issue of improper seating due to misalignment as seen in other competitive systems.22,23 Cocking of a ceramic liner, in particular, during impaction can lead to a fracture of the liner.


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References

1 Ahier S, Ginsburg K. Influence of carbide distribution on the wear and friction Vitallim. Poc Inst Mech Eng. 1966;181:127–129.

2 Clemow AJT, Daniell BL. The influence of microstructure on the adhesive wear resistance of a Co-Cr-Mo alloy. Wear. 1980;61:219–232.

3 Wang KK, Wang A, Gustavson LJ. Metal-on-metal wear testing of chrome cobalt alloys. In: Digesi JA, Kennedy RL, Pillar R, eds. Cobalt-base alloys for biomechanical applications. ASTM STP 1365: Wear Characterization. West Conshohocken, PA: ASTM; 1999:135–144.

4 McMinn D. Development of metal/metal hip resurfacing. Hip International. 2003;13(1) suppl 2.

5 Biolox-ceramics for his arthroplasty. CeramTec AG, MT 060003: GB.5.000-0612. Germany.

6 CeramTec Technical Monograph. Current perspective on the use of ceramics in total hip arthroplasty. CeramTec AG, 060003: GB.5.000-0612, 2007.

7 Internal Smith & Nephew testing on file.

8 Li MG, Zhou ZK, Wood DJ, et al. Low wear with high-cross linked polyethylene especially in combination with OXINIUM heads. A RSA evaluation. Poster no. 643 presented at: Orthopaedic Research Society Annual Meeting; March 19–22, 2006; Chicago, IL.

9 Clarke IC, Good P, Williams P, et al. Ultra-low wear rates for rigid-on-rigid bearings in total hip replacements. Poc Inst Mech Eng. [H] 2000;214(4):331–347.

10 Good V, Ries m, Barrack RL, Widding K, Hunter G, Heuer D. Reduced wear with oxidized zirconium femoral heads. J Bone Joint Surg Am. 2003;85-A Suppl 4:105–110.

11 Scott M, Morrison M, Mishra SR, Jani S. A method to quantify wear particle volume using atomic force microscopy. ORS Transactions. 2002:27:132.

12 Ries MD, Scott ML. Realationship between gravimetric wear and particle generation in hip simulators: conventional versus crosslinked polyethylene. Scientific exhibit at American Academy of Orthopaedic Surgeons; Feb 27–March 4, 2001; San Francisco, CA.

13 Good V, Widding K, Heuer D, Hunter G. Reduced wear using the ceramic surface on oxidized zirconium heads. In: Lazennec JY, Dietrich M, eds. Bioceramics in Joint Arthroplasty. Darmstadt, Germany: Steinkopff; 2004:93–98.

14 Berry DJ, von Knoch M, Schleck CD, Harmsen WS. Effect of femoral head diameter and operative approach on risk of dislocation after primary total hip arthroplasty. J Bone Joint Surg Am. 2005 Nov;87(11):2456–2463.

15 Barrack RL, Butler RA, Laster DR, Andrews P. Stem design and dislocation after revision total hip arthroplasty: clinical results and computer modeling. J Arthroplasty. 2001 Dec;16(8 Suppl 1):8–12.

16 Barrack RL. Dislocation after total hip arthroplasty: implant design and orientation. J Am Acad Orthop Surg. 2003 Mar-Apr;11(2):89–99.

17 Barrack RL, Lavernia C, Ries M, Thornberry R, Tozakoglou E. Virtual reality computer animation of the effect of component position and design on stability after total hip arthroplasty. Orthop Clin North Am. 2001 Oct;32(4):569–577, vii.

18 Tradonsky S, Postak P, Frimson A, Greenwald A. Performance characteristics of two piece acetabular cups. Cleveland, OH: The Orthopaedic Research Laboratory, Mt. Sinai Medical Center. 1992.

19 FDA guidance document for testing acetabular cup prosthesis. US Food and Drug Administration. May 1995.

20 Bourne R. Randomized controlled trial to compare acetabular component fixation of two porous ingrowth surfaces using RSA analysis. London, Ontario, Canada: London Health Science Center. 2007. Internal report on file at Smith & Nephew, Memphis, TN.

21 Heiner AD, Brown TD. Frictional coefficients of a new bone ingrowth structure. Poster no. 1623 presented at: Orthopaedic Research Society Annual Meeting; Feb 11–14, 2007; San Diego, CA.

22 Padgett DE, Miller AN, Su EP, Bostrom MPG, Nestor BJ. Ceramic liner malseating in total hip arthroplasty. Poster PO97 at American Academy of Orthopaedic Surgeons; Feb 14–18, 2007; San Diego, CA.

23 Langdown AJ, Pickard RJ, Hobbs CM, Clarke HJ, Dalton DJ, Grover ML. Incomplete seating of the liner with the Trident acetabular system: a cause for concern? J Bone Joint Surg Br. 2007 Mar;89(3):291–295.

45940402 01/08

Orthopaedic ReconstructionSmith & Nephew Inc.1450 Brooks RoadMemphis, TN 38116USA

Telephone: 1-901-396-2121Information: 1-800-821-5700Orders and Inquiries: 1-800-238-7538

www.smith-nephew.com

™Trademark of Smith & Nephew. Certain marks Reg. US Pat. & TM Off. All Trademarks acknowledged.

45940402 R3 Design Rationale US - Smith+Nephe · 4 0 0.5 1 1.5 2 2.5 3 Wear factor x10-6 (mm 3 /Nm)...

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