COMPARISON OF THE EFFECTS OF GAMMA-RADIATION AND LOW-TEMPERATURE HYDROGEN-PEROXIDE GAS PLASMA STERILIZATION ON THE MOLECULAR-STRUCTURE, FATIGUE RESISTANCE, AND WEAR BEHAVIOR OF UHMWPE

The effects of gamma radiation and low temperature hydrogen peroxide g as plasma (HPGP) sterilization on structure and cyclic mechanical prop erties were examined for orthopedic grade ultra-high-molecular-weight polyethylene (UHMWPE) and compared to each other as well as to no ster ilization (control). Density was monitored with a density gradient col umn and was found to be directly influenced by the sterilization metho d employed: Gamma radiation led to an increase, while plasma did not. Oxidation of the polymer was studied by observing changes in the carbo nyl peak with Fourier transform infrared spectrometry and was found to be strongly affected by both gamma radiation and subsequent aging, aw hile plasma sterilization had little effect. Gamma radiation resulted in embrittlement of the polymer and a decreased resistance to fatigue crack propagation. This mechanical degradation was a direct consequenc e of postradiation oxidation and molecular evolution of the polymer an d was not observed in the plasma-sterilized polymer. Both gamma radiat ion and plasma sterilization led to improved wear performance of the U HMWPE compared to the nonsterile control material. (C) 1998 John Wiley & Sons, Inc.