Investigation of long-lived free radicals in shelf-aged UHMWPE tibial liners

UHMWPE used in total joint arthroplasty has commonly been sterilized by gamma radiation. Irradiation and subsequent aging in air reportedly cause extensive oxidation and, thus, adversely affect this material. Long-lived free radicals in gamma-sterilized/shelf-aged UHMWPE tibial inserts were investigated in this study. Significant concentrations of peroxy and primary radicals were found in the surface layer and the core region, respectively. Based on this study, it is expected that ir radiation of UHMWPE in an inert environment would result in long-lived primary radicals, which could be a potential cause of long-term oxidation.