Comparison of in-vivo wear between polyethylene inserts articulating against ceramic and cobalt-chrome femoral components in total knee prostheses

Abstract

In the late 1970s, the use of a combination of alumina ceramics and ultra-high molecular weight polyethylene (UHMWPE) was started for total knee prostheses (TKPs) to reduce UHMWPE wear and suppress bone resorption, based on good clinical results in total hip prostheses. In this study, to examine the in vivo efficacy of alumina ceramic bearing surface of TKP, we compared retrieved alumina ceramic TKPs with cobalt-chrome (Co-Cr) alloy TKPs by surface observation and linear wear measurement. In the scanning electron microscopic observations, many scratches due to clinical use were observed only on the retrieved Co-Cr alloy femoral component. The damage in the form of scratches on the articulating surface was linear and produced by rubbing of microscopic asperities against the Co-Cr alloy surface. The linear wear rate of the retrieved Co-Cr alloy TKPs was 0.027-0.358 mm/year. In contrast, the wear of the retrieved alumina ceramic TKPs was stably low and linear; the linear wear rate was estimated to be 0.026 mm/year. The lower wear rate and milder nature of wear observed in TKP with UHMWPE insert and alumina ceramic femoral component combination suggest the possibility of retention of high performance of this TKP even during prolonged clinical use.