Analysis of retrieved acetabular components of three polyethylene types

The polyethylene used in total hip arthroplasty has gone through many changes over the past several decades, including consolidation processes, resin types, method of sterilization, packaging, and the extent of crosslinking. To isolate the in vivo performance of material changes from implant system design changes, we assessed the postretrieval surface wear and damage of components made from three different polyethylene types used in a single implant system. The polyethylene types investigated are representative of the sequentially available bearing materials that have dominated use in total hip arthroplasty over the last several decades. Forty-six components with implantation durations of 12 to 96 months were assessed for surface wear and damage and for socket wear and creep volume change. Acetabular components made from highly crosslinked polyethylene had a 50% lower total damage score than components made from polyethylene that was either gamma-sterilized in air or in nitrogen. The wear and creep socket volume change was 80% and 90% lower for the highly crosslinked components compared with the gamma-sterilized in air and nitrogen groups, respectively. These data of direct component measurement are consistent with earlier predictions that recent changes in polyethylene material processing can lead to clinically improved bearing performance.