Polyethylene in Knee Arthroplasty

Abstract

Ultra-high molecular weight polyethylene remains the gold standard as a bearing surface for total knee arthroplasty. But problems of oxidative degradation and wear have prompted new sterilization techniques and new forms of more highly cross-linked polyethylene. The value of these solutions can be shown initially from laboratory data, but in the end their usefulness will be confirmed through clinical performance. The significance of new polyethylenes cannot be established on the basis of a single type of test or even on a single goal such as improved wear resistance. Rather, a range of requirements dictated by design goals (function, fixation, and wear) must be considered. The requirements can be competing, so that matching one compromises matching another that, if not taken into account, can lead to failure in clinical use. Previous improvements to polyethylene ultimately failed because not all the requirements were met. The same concern exists with highly cross-linked polyethylenes; improvements in wear resistance are tempered by a decrease in toughness. A case can be made for and against these polyethylenes, but early clinical results in hip arthroplasty show significantly improved wear, raising the possibility of also improving wear performance in knee arthroplasties.