Study demonstrates that gamma radiation alters molecular structure, impacting fatigue resistance in UHMWPE.
Medical grade ultra high molecular weight polyethylene (UHMWPE) remains the best material choice for the articulating surface in total joint replacements. The primary complication with hip and knee joint replacements is fatigue related damage and wear debris of the UHMWPE. As with any biomaterial to be implanted in the body, the polyethylene components must be sterilized prior to implantation. In the medical community, the standard method for polyethylene sterilization is gamma radiation, usually 2.5 Mrad from a 60Co source. The gamma irradiation is known to alter the molecular structure of the polymer through chain scission, cross linking and oxidative degradation. This ultimately affects the mechanical integrity of the polymer. Limited work has been done to systematically characterize the effect of sterilization on the structural evolution of the polymer and its affect on the fatigue resistance of the UHMWPE. In this study, we investigate the fatigue behavior for aged, compression molded, medical grade UHMWPE in sterile and nonsterile form. With the aid of transmission electron microscopy (TEM), small-angle x-ray scattering (SAXS) and differential scanning calorimetry (DSC), the structural evolution due to gamma irradiation is characterized.
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Ranganathan et al. (1995) studied this question.
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