Study of fatigue resistance of chemical and radiation crosslinked medical grade ultrahigh molecular weight polyethylene

The aim of this work is to understand the role of chemical and radiation in duced crosslinking on the fatigue crack propagation resistance of medical g rade ultrahigh molecular weight polyethylene (UHMWPE). In recent years, the need to improve the tribological performance of UHMWPE used in total joint replacements has resulted in the widespread utilization of crosslinking as a method to improve wear resistance. Although crosslinking has been shown to drastically improve the wear resistance of the polymer, the potential tr ade-off in fatigue properties has yet to be addressed. Fatigue crack propag ation resistance is a concern in tibial inserts where large cyclic stresses are sufficient to drive the growth of subsurface cracks that potentially c ontribute to delamination wear mechanisms. For clinical relevance, the comb ined effects of sterilization and aging are examined in two commercially av ailable crosslinked resins. Nonsterile and unaged resins serve as a control . To evaluate the effect of crosslinking, a comparison is made to uncrossli nked resins. Scanning electron microscopy is used to provide an understandi ng of fatigue fracture mechanisms in the crosslinked polymers. The results of this study show that the current level of crosslinking used in orthopedi c resins for enhanced wear resistance is not beneficial for fatigue crack p ropagation resistance. (C) 1999 John Wiley & Sons, Inc.