A NOVEL METHOD OF CROSSLINKING UHMWPE TO IMPROVE WEAR, REDUCE OXIDATION AND RETAIN MECHANICAL PROPERTIES

Abstract

Increasing crosslinking has been shown in vitro and in vivo to markedly improve the wear resistance of ultra-high molecular weight polyethylene (UHMWPE). However, the reduction in the mechanical properties of polyethylene under certain methods used to produce crosslinking has been a concern. These reductions are known to result from the processes used to increase the crosslink density and could affect the device performance in vivo. We present a novel method of increasing the crosslink density of UHMWPE in which UHMWPE is irradiated in air at an elevated temperature with a high dose rate electron beam and is subsequently melt-annealed. This treatment markedly improves the wear resistance of the polymer as tested in a hip simulator while maintaining the mechanical properties of the material within national and international standards. This method also leads to the absence of detectable free radicals in the polymer and, as a result, excellent resistance to oxidation of the polymer.