Dynamical mechanical analysis as an assay of cross-link density of orthopaedic ultra high molecular weight polyethylene

Abstract The established gravimetric gel swell technique for measuring cross-link density in orthopaedic ultra-high molecular weight polyethylene (UHMWPE) is unable to detect local distributions of cross-link density that may be expected after in vivo degradation. Dynamic mechanical analysis (DMA) offers better spatial resolution of cross-linking. The ability to measure cross-link density in thin specimens using DMA would enable depth dependent analysis of cross-link density, opening the door to future studies on the effects of oxidation, antioxidants, and other factors on cross-linking. Thus, the aim of this study was to compare the performance of gel swell and DMA in the measurement of cross-link density in a range of highly cross-linked UHMWPE materials and to determine the relationship between the results of the two techniques. The results suggest that DMA and gel swell each offer advantages, and that both may have applications in the study of explanted orthopaedic UHMWPE bearings.