1. Are all MB knees the same? Is MB really better than FB? Jean-Louis Briard
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3. #1 Maximum Conformity Can be achieved through: Multi-radius sagittal femoral geometry with a distal sphere Constant radius sagittal FT geometry with a posterior sphere A - SPHERICAL DESIGNS B -OVOID DESIGNS Never spherical Coronal & sagittal radius are different
4. Multi-radius sagittal femoral geometry: J curve with a distal sphere: S2 Extensive area contact near to extension (R: 50mm ) But circular line contact in Flexion LCS & Generics, Interax ISA, Genesis II/ Profix, Innex, Link TACK, Cinétique A 1 SPHERICAL DESIGNS S2
5. Constant radius sagittal FT geometry with a posterior sphere Contact area more limited in extension (R: 25mm ) Larger contact in flexion Rotaglide, SAL, TRAC, MBK, Oxford TMK A 2 - SPHERICAL DESIGNS
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9. But in face of V/V tilting and subsequent lift-off which divides the area by 2, 900 mm 2 seems safer Remember with LCS and poor PE, wear is exceptional !
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11. Multidirectional Unidirectional Study conducted at Leeds University by Hannah McEwen, J.Fisher Has proven the value of the LCS concept designed 30 y ago !
12. UHMWPE Kinematics UHMWPE orientates in principle direction of sliding (Pooley & Tabor 1972, Proc.Roy.Soc.Lon.A, 329, 251) Strength increased parallel to sliding but reduced strength transverse to sliding (Wang et al. 1996, Proc.IMechE, 210H, 141) + Multidirectional works as a file ! : Consequence : # 1
14. Fixed vs RP Fixed bearing Multidirectional motion of femoral component relative to bearing RP Mobile bearing Bearing rotation decoupled: Linear rotation at tibial counterface with reduced rotation at femoral counterface Not to speak of Backside wear !
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17. LCS spinout but very exceptional (4/2000) Stability is an issue
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