Review Question - QID 1248

Total knee arthroplasties continue to be performed in patients who are younger and more active. As a result of this trend, better wear performance is imperative for long-term durability. Research continues to be done to determine optimal wear characteristics of different polyethylene and metal surfaces. Mobile-bearing knee systems are distinguished from conventional, fixed-bearing systems in that they allow dual-surface articulation between an ultra-high molecular weight polyethylene insert and metallic femoral and tibial tray components. This results in increased sagittal femorotibial conformity of most mobile-bearing implants, which reduces polyethylene shear stresses and should lessen polyethylene wear rates. By allowing more contact area, the surface and subsurface stresses in the poly bearing are significantly reduced (recall that pressure = force / area).

The ICL by Callaghan et al review the early findings of studies of fixed versus mobile bearing implants. Research is progressing as long term data continues to be collected and analyzed. Despite theoretical advantages, there has been no documented improvement in survivorship between mobile and fixed bearing TKA's in short and intermediate term studies.