Investigation on the structure, cross-link, and oxidation index of ultra high molecular weight polyethylene acetabular liners

Abstract

In this work, we proposed a set of techniques and respective methodologies to investigate the physicochemical properties of six models of ultra high molecular weight polyethylene (UHMWPE) acetabular liners commercially available. The correlation between chemical properties, sterilization techniques, and potential performance of material were proposed. Optical microscopy, density, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and swell test were employed to evaluate the medical product and manufacturing process safety characteristics. Microscopy demonstrated that all samples went through a satisfactory consolidation process. FTIR revealed that only three models were not exposed to gamma irradiation, and consequently were not cross-linked. On the other hand, three other samples were exposed to gamma irradiation in which on presented an elevated oxidation index. This result was further investigated through the packaging evaluation where it was found that the sample with higher IOX was exposed to an oxygen atmosphere during sterilization and/or shelf life. Samples exposed to sterilization technique in atmosphere with oxygen were observed to have higher oxidation indexes, which are associated with material degradation in vivo. This work demonstrated the relevance of combining specific physicochemical techniques for process mapping and to characterize UHMWPE acetabular liners.