Influence of Cross-linking and Oxidation on the Microstructural Mechanical Properties of UHMWPE

摘要

Ultra-high molecular weight polyethylene (UHMWPE) is commonly used as a bearing surface in total joint replacements. This study examined the effects of cross-linking and oxidation on the mechanical properties of UHMWPE at the microstructural level, rather than at the bulk level. Nanoindentation tests were performed on the articulating surfaces of two freshly machined UHMWPE acetabular inserts, one of which was cross-linked, and also performed along a freshly cut cross-section of a UHMWPE tibial insert that had been sealed in its original packaging and shelf-aged for at least five years. The reduced modulus of cross-linked UHMWPE was significantly lower than native UHMWPE. Tests on the cross-section of the shelf-aged specimen revealed a reduced modulus profile with a subsurface peak that was similar to the oxidation profiles of aged UHMWPE observed by others. Future work should examine the microstructural mechanical properties of UHMWPE using methods that more accurately account for its viscoelastic nature, and should directly correlate microstructural properties with oxidation.