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FEMORAL COMPONENT Prosthetic design

Learn about the design features of cemented and cementless femoral components in prosthetics, including head, neck, collar, and stem characteristics. Explore the advantages and controversies surrounding different design elements and materials.

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FEMORAL COMPONENT Prosthetic design

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  1. FEMORAL COMPONENTProsthetic design M. E. Cabanela, M.D. Professor of Orthopedic Surgery Mayo Clinic College of Medicine Rochester, MN

  2. FEMORAL COMPONENTProsthetic design Ideas learned over the years Most are simple Most are acepted today No pretenses of being a prosthetid designer Always keep an open mind

  3. CEMENTED FEMORAL COMPONENTDesign features • Head • Neck • Collar • Stem

  4. CEMENTED FEMORAL COMPONENTHead • DiameterChanged over yrsWear vs stability vs. loosening • MaterialCo-Cr vs. Ti vs. Ceramic • Surface finishIon-bombarded

  5. CEMENTED FEMORAL COMPONENTNeck • ModularityPros: optimize lenght, stability and offset biomechanicsCons: corrosion, skirts undesirable • Cross sectionMaximize ROM before impingement

  6. CEMENTED FEMORAL COMPONENTCollar • Controversial • Facilitates load transfer to cement • Difficult to achieve and maintain calcar-collar contact • Eliminates ability of stem to subside • Collar may be good for some stems and deleterious for others

  7. CEMENTED FEMORAL COMPONENTStem • Geometric properties- Length- - Shape- Cross section • Material properties • Surface finish

  8. CEMENTED FEMORAL COMPONENTGeometry • Length-Medium (too long-stress shielding, too short-increased cement stresses) • ShapeStraight, not curved • Cross sectionRotationally stable (rectangular, not rounded) No sharp corners (stress concentration on cement)

  9. CEMENTED FEMORAL COMPONENTMaterial properties • Stiff material to minimize stress transmision to the proximal bone and cement: Stainless steel or Co-Cr • Titanium produced bad track record in the USA

  10. CEMENTED FEMORAL COMPONENTSurface finish • Controversial, but more and more information in favor of polished surfaces, that would allow subsidence and minimize fretting if debonding occurs

  11. CEMENTLESS STEMPrerequisites • Attain immediate stable fixation • Attain long-term biologic fixation • Provide favorable biologic compatibility • Allow long-term bone remodeling

  12. INITIAL FIXATIONAlternatives • Metaphyseal straight anatomic-curved • Diaphyseal

  13. TORSIONAL STABILITY • Slightly better in anatomic stem Callaghan et al JBJS 74A:839, 1992 • Better in straight stem Schneider et al Clin Orthop 248:200, 1989

  14. STRAIGHT STEMAdvantages Metaphyseal fill (proximal fixation) • Better adaptation to anatomic variation of proximal femur • Simple instrumentation needed to machine proximal canal • Easier insertion and better fit than curved stem

  15. STRAIGHT STEMAdvantages Diaphyseal fixation • Bypass variable proximal femur • Achieve consistent fixation in cortical bone of medullary canal

  16. CEMENTLESS STEMMetaphyseal vs. diaphyseal • Both work clinically • Both have good long term track record • Both cause some stress shielding • Choice for the long term is unclear

  17. Je vous remercie

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