THR cemented vs uncementd
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Transcript of THR cemented vs uncementd
Primary Total Hip ReplacementCemented vs Un cemented
Total Hip ReplacementTypes ( based on fixation technique )
• Cemented• Un cemented• Hybrid• Reverse hybrid
Implant selection
• Patients age• Underlying bone pathology• Type of medullary canal
DORR classification
Cemented stems
• Elderly patients , particularly females• Inflammatory and metabolic bone disease• Cylindrical morphology of proximal femur ( DORR C )
Cement less stems
• Younger and relatively younger patients• AVN, osteoarthritis, Post traumatic arthritis• Funnel shaped proximal femur ( DORR A )
Cemented stem designs
• Taper slip• Composite beam
Taper slip design
• Collar less, tapered• Subsidence results in tighter wedging• Shear converted into compressive stresses
Composite beam design
• Collared• Rough surface• Co-Chrome (stiff ) stem• Strain on cement mantle reduced
Cementing technique
• Broach only technique• Antibiotic cement• Third generation cementing• Uniform cement mantle 2 to 3 mm thick
Cement less ( Press fit ) designs
• Tapered• Cylindrical• Anatomic
Tapered stem design
First generation• Load femur proximally only• Proximally coated• Tapered AP and ML• No collarSecond generation• Rotational ridges and polished tip
Cylindrical stem design
First generation• Cylindrical distally and distal press fit• Extensively porous coated• Usually collaredSecond generation• Better proximal fit• Distal flutes and coronal slots• Polished tip
Anatomic stem design
First generation• Better proximal fill and fit• Anteverted necks ( right and left )• Significant thigh pain and osteolysis
Second generation• Bowed tip eliminated• Flattened posterior and lateral sides
Types of porous coatingSecondary stability
• Sintering• Diffusion bonding• Plasma spraying
Optimal pore size 100 to 400 µm
Interphase dynamics
• Gap should be < 0.5 mm• Micro motion should be < 50 µm
Ceramic coating
• Hydroxyapatite • Tri calcium phosphate
• Fills Bone Implant gaps• Bioactive and bio-absorbable
• Particulate disease• Heterotopic bone
Cemented acetabular component
All poly cup
• Hypotensive anaesthesia• Good cancellous bed• Proper cement pressurization
Cement less acetabular component
• Hemispheric cups with porous coating• Fixation with press fit or screws
Cement less acetabular component
• Screw holes eliminated or reduced• Polished inner surface• Improved socket liner conformity and locking
Out comes
• Medium and long time Survival rates are good for both types of femoral components
• Pelvic osteolysis is still a problem with both types of cups
• Loosening is a problem with cemented acetabular components after the first decade
Technique and time
Cemented THR is technically more demanding
• Blood less field• Cement pressurization• Uniform and homogenous cement mantle
Post op. weight bearing
Cemented immediate
Un cemented 4 to 6 weeks immediate if fill and fit is good
Peri-prosthetic fractures
• More common with un cemented• More on the femoral side and in elderly
females
• Intra op. fractures 0.3 % ( cemented ) 5.4 % ( un cemented ) ( Mayo clinic registry )
Deep infections
No difference between the types-
when Cemented THR is done with antibiotic impregnated cement
Dislocations
More common with un cemented due to imperfect version and soft tissue balancing
Cost
• Manufacturing cost of un cemented implants is more
• With cemented THR - cement , related equipment, increased operating room time
• Cost difference is $ 300
Recent Trends
Swedish Hip Registry 2008 Australian Jt Registry 2009
Summary Cemented or un cemented
Elderly patients , particularly females with poor bone quality ----- cemented hip.
Otherwise ------ un cemented hip
SummaryUn cemented hips
Implants
Femur Tapered, proximally coated Acetabulum Hemispheric cup without holes
SummaryUn cemented hips
• Appropriate implant size• Careful insertion• Primary implant stability with press fit For adequate osseous integration• Literature does not support routine usage of
ceramic coated implants
SummaryCemented hips
Implants
Femur tapered, collar less, smooth surface Acetabulum Highly cross linked all poly
SummaryCemented hips
• Blood less cancellous acetabular bed• Cement pressurization
• Third generation cementing technique• Uniform, homogenous cement mantle
• Be ware of embolic manifestations in cardio-pulmonary compromised patients
Thank you