Simulated normal gait wear testing of a highly cross-linked polyethylene tibial insert.

Polyethylene wear can compromise long-term performance of total knees. We investigated articular and backside wear rate of tibial inserts made from conventional vs highly cross-linked polyethylenes. The inserts were tested on a knee simulator at a frequency of 1.1 Hz using normal gait kinematics with a 7 degrees posterior slope for 7 million cycles. Gravimetrically, the combined articular and backside wear rate was 23 +/- 6 and 4.6 +/- 2 mm(3) per million cycles for the conventional and cross-linked inserts, respectively. We independently measured articular surface wear rates, which were 15 +/- 4 and 5 +/- 2 mm(3) per million cycles for conventional and cross-linked inserts, respectively. Electron beam cross-linked and subsequently melted polyethylene reduced the wear rate of polyethylene on articular and backside surfaces in a cruciate-retaining total knee design when tested on a knee simulator under simulated normal gait.