The effects of degree of crosslinking on the @entity1295 and propagation resistance of orthopedic-grade XXXX .

@entity691 @entity16 @entity1295 @entity174
Crosslinked ultrahigh molecular weight @entity691 (UHMWPE) has been recently approved by the Food and Drug Administration for use in orthopedic implants. The majority of commercially available UHMWPE orthopedic components are crosslinked using e-beam or gamma radiation. The level of crosslinking is controlled with radiation dose and free radicals are eliminated through heat treatments to prevent long-term degradation associated with chain scission or oxidation mechanisms. Laboratory studies have demonstrated a substantial improvement in the wear resistance of crosslinked UHMWPE. However, a concern about the resistance to @entity16 remains in the clinical community, especially for tibial components that sustain high cyclic contact stresses. The objective of this study was to investigate both the initiation and propagation aspects of fatigue cracks in radiation crosslinked medical-grade UHMWPE. This work evaluated three levels of radiation, which induced three crosslink densities, on the @entity1295 and total fatigue life behavior. Both as-received UHMWPE, as well as those that underwent an identical thermal history as the crosslinked UHMWPE were used as controls. @entity174 crack propagation specimens were examined using scanning electron microscopy to elucidate fatigue @entity174 mechanisms. The results of this work indicated that a low crosslink density may optimize the fatigue resistance from both a crack initiation and propagation standpoint.
