EXTENSIVELY CROSS-LINKING OF UHMWPE TO IMPROVE WEAR PERFORMANCE IN TOTAL HIP REPLACEMENT

Abstract

A method to extensively cross-link polyethylene for total hip application has been developed and tested in hip wear simulation. Extensively cross-linked polyethylene was prepared by exposing GUR 1050 polyethylene resin to 90 kg to 110 kg of e-beam radiation. For total hip application, the material was evaluated in an AMTI joint simulator in normal debris-free conditions and in a Shorewestern simulator for the adverse condition of added bone cement and aluminum oxide debris. The normal condition testing was conducted to 30 million cycles, while the adverse condition tests were conducted to 5 million cycles. Femoral head sizes from 22 mm to 46 mm were evaluated. The wear performance of extensively cross-linked material was compared to control material (GUR 1050 gamma sterilized in nitrogen). The results demonstrate a significant improvement in wear (greater than 80 percent reduction) of extensively cross-linked GUR 1050 acetabular components compared to the control acetabular components. The adverse condition wear of both materials was greater than the normal wear; however, when compared to the controls, the extensively cross-linked material had improved wear performance in both normal and adverse conditions. The wear of femoral heads larger than normal 32 mm sizes showed accelerated wear in the control material and desirable low wear in the extensively cross-linked condition. The polyethylene particles generated in the wear simulation were of similar size and shape between the extensively cross-linked and controlled polyethylene. As demonstrated in the laboratory simulation, this extensively cross-linked polyethylene has the potential to substantially reduce particular debris generation in total hip applications. A multicenter randomized controlled clinical study of extensively cross-linked and control acetabular components is ongoing.