The effect of lipid absorption on the mechanical properties of crosslinked and conventional UHMWPE

The purpose of the current study was to explore how the mechanical properties of conventional and highly crosslinked UHMWPE are affected by diffusion of cholesterol into the material. We hypothesized that diffusion of cholesterol in the bulk of conventional and highly crosslinked UHMWPE would serve as a plasticizer, resulting in a reduction in its mechanical properties. Soaking in cholesteryl acetate had a slight, but significant, effect on the elastic and ultimate properties of highly crosslinked, but not the conventional UHMWPE materials. Thus, the large degradative changes in ultimate properties previously measured in conventional long-term retrievals do not appear to be consistent with soaking in a lipid, such as cholesteryl acetate. However, the decreases in mechanical properties observed for the immersed crosslinked materials suggest that biological factors may play a larger role than previously expected for highly crosslinked materials currently used in hip and knee replacements.