Nanoindentation of Polyethylene Tibial Components

Delamination is a common failure mechanism in ultra-high molecular weight polyethylene (UHMWPE) tibial inserts [Wright and Rimmnac, 1988]. Changes in polyethylene mechanical properties, such as subsurface embrittlement due to oxidation, may promote crack propagation. The assessment of through-thickness properties may, therefore, provide insight into delamination mechanisms. Using the small punch test [Kurtz et al., 1997], researchers have studied changes in subsurface mechanical properties in aged and unaged tibial components [Edidin et al., 1999; Ely et al., 2000]. In this present study, we used nanoindentation to measure stiffness and hardness profiles in cross sections of unused polyethylene tibial components. Nanoindentation has previously been used to characterize surface properties of UHMWPE [Schmidt et al., 2000].