Reduction of polyethylene in a congruent meniscal knee prosthesis. Experimental and clinical studies.

Abstract

Polyethylene wear was assessed in the Rotaglide congruent meniscal bearing total knee prosthesis and a partial congruent total knee prosthesis with fixed bearing polyethylene tibial platform and a posterior stabilizer mechanism. A special wear test rig was used to test the 2 prostheses under compression load of 2960 N/mm2 (about 4 times the average body weight) and continuous 0 degree-70 degrees flexion-extension motion at the rate of 1 cycle per second. The most remarkable finding was the lack of measurable wear on the Rotaglide meniscal bearing up to 3.5 million cycles, while the other prosthesis began to show wear from the first million cycles and progressed to 0.38 mm at about 3.5 million cycles. At 11 million cycles (about 20 years of life), the Rotaglide showed penetration wear of 0.35 mm compared to 2.1 mm in the other prosthesis. In 7 meniscal bearings, retrieved either at postmortem (2) or at reoperation (5), no measurable penetration wear was observed after 3 years of implantation. Only 1 prosthesis obtained 5 years after implantation showed 0.23 mm penetration wear or about 0.05 mm per year. These findings strongly suggest that the use of congruent meniscal bearing prosthesis can reduce the polyethylene wear in total knee replacement.