Clinical wear measurement on low contact stress rotating platform knee bearings

Whereas fixed-bearing total knee arthroplasty (TKA) designs secure the polyethylene bearing to the tibial tray, mobile-bearing TKAs allow the bearing to move relative to the tray. This study evaluated wear performance of the rotational articulation of the Low Contact Stress Rotating Platform mobile-bearing TKA (DePuy, Warsaw, Ind) by analyzing 100 retrievals. All retrieved bearings showed rotation surface damage, but severity of the damage did not correlate with duration. Rotation surface damage appeared to be caused by contaminant particles, which produced curvilinear scratches that were longer than the normal rotational excursion of the knee. Wear measurement indicated that wear was relatively uniform, long-term wear rates were low (mean, 54 mm(3)/y for durations >2 years) and decreased with longer duration, and damaged appearance did not correspond to high wear.