Wear testing of UHMWPE tibial components: Influence of oxidation

An AMTI knee stimulator was used to evaluate the wear of UHMWPE tibial inse rts which were gamma sterilized in air and displayed a high or low level of oxidation. After 5 million cycles, four out of five samples from the high oxidation group displayed subsurface cracking and/or delamination. The five specimens in the low oxidation group experienced burnishing only. These re sults indicate that gamma irradiation in air together with high oxidation d ue to shelf aging can increase susceptibility to wear. The appearance of th e wear scars indicates that knee simulator testing is a valid method of pro ducing burnishing, cracking, and delamination similar to that seen in-vivo.