Knee-simulator testing of conventional and cross-linked polyethylene tibial inserts

We compared the resistance to delamination and to adhesive/abrasive wear of conventional and highly cross-linked polyethylene tibial inserts of a cruciate-retaining total knee design using a knee simulator. Both groups were tested after aggressive, accelerated aging, and I set of conventional inserts was studied without aging. Aging oxidized the conventional, but riot the highly cross-linked, inserts. The simulated normal gait testing lasted for 5 and 10 million cycles for the conventional and highly cross-linked inserts, respectively. Aged conventional inserts showed delaminations, whereas none were observed in the unaged conventional and aged cross-linked inserts. Wear rates measured by the gravimetric method were 9 +/- 2 mm(3), 10 +/- 4 mm(3), and 1 +/- 0 mm(3) per million cycles; by the metrologic method, they were 8 +/- 1 mm(3), 9 +/- 2 mm(3), and 3 +/- 0 mm(3) for the unaged conventional, aged conventional, and aged highly crosslinked inserts, respectively. in the test model used, oxidation led to delamination, whereas increased cross-link density resulted in reduced adhesive/abrasive wear of tibial inserts. (C) 2004 Elsevier Inc. All rights reserved.