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° posterior slope for 7 million cycles. Gravimetrically, the combined articular and backside wear rate was 23 ± 6 and 4.6 ± 2 mm3 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 mm3 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.