The document discusses factors that influence wear in knee replacements, including prosthesis design and kinematics. It finds that rotating platform mobile bearing knee replacements significantly reduce wear and osteolytic potential compared to fixed bearing knees, but some of these benefits can be lost if lift-off of the femoral condyle occurs, increasing medial/lateral wear in both designs. Careful surgery and soft tissue management are important to wear performance. Rotating platform mobile bearing knees showed a four-fold reduction in wear rate compared to fixed bearing knees in simulated tests.

5. Leeds ProSim Knee Simulator

9. Fixed Bearing Knees PFC  - IR in air PFC Sigma  - IR under vacuum and foil packed PFC Sigma Marathon

10. Effect of Kinematics on Wear Fixed Bearing Knees

11. Effect of Kinematics Fixed Bearing Knees - PFC Sigma 1020 GVF

12. Fixed Bearing Knees PFC Sigma 1020 GVF High Kinematics PFC Sigma 1020 GVF Intermediate Kinematics PFC Sigma 1020 GVF Low Kinematics McEwen et al J Biomechanics 2005

16. Effect of Prosthesis Design

18. Fixed Bearing Knee PFC Sigma Mobile Bearing Knee PFC Sigma RP Engineering Comparison: Matched Intermediate Kinematics McEwen et al, J Biomechanics 2005

19. Fixed Bearing Knee PFC Sigma Mobile Bearing Knee PFC Sigma RP Clinical Comparison High Kinematics McEwen et al, J Biomechanics 2005

22. Wear Debris Volumetric Concentration

23. Biological Activity and Osteolytic Potential Tipper et al, Soc Biomaterials 2005 17.6 0.69 25.6 ± 5.3 Hip 1.8 0.36 5.2 ± 3.8 PFC Sigma RP 6.8 0.3 22.75 ± 5.95 PFC Sigma FBA Functional Osteolytic Potential SBA Specific Biological Activity Mean Wear Rate (mm 3 /10 6 cycles) Implant Type

26. Effect of Lift Off Fixed Bearing PFC Sigma Mobile Bearing PFC Sigma Rotating Platform p < 0.05 p < 0.05 p > 0.05

29. Thank you Co authors Hannah McEwen, Petra Barnett, Carol Bell, Amir Kamali, Dan Auger, Richard Farrar, Joanne Tipper, Alison Galvin, Mark Taylor, Martin Stone, Eileen Ingham Research supported by EPSRC, ARC, DePuy