Thermal stabilization of highly crosslinked UHMWPE:A comparative study between annealed and remelted resins

Purpose: An important issue related to the use of highly crosslinked ultra-high molecular weight polyethylene (HXLPE) in arthroplasty concerns the long-term oxidation of the polymer and related degradation of its end-user properties. Although in very recent years several procedures have been introduced into the manufacturing of prosthetic components to overcome this problem, the risk of long-term oxidation has not been completely eliminated. The aim of this study is to compare the effects on the physical and mechanical properties of HXLPE from two different thermal treatments used to promote oxidative stabilization. It also gives a description of the effects of oxidative degradation on the mechanical performance of HXLPE. Materials and Methods: Virgin medical grade UHMWPE GUR 1020 was irradiated at 100 kGy and submitted to heat treatments at either 110°C (annealing) or 150°C (remelting). Oxidation analysis, Wear tests, Tensile tests and Charpy impact tests were carried out. Results: The temperature of the thermal treatment affects both oxidation resistance and impact strength of HXLPE, whereas wear resistance is not affected. Conclusion: The study provides a confirmation that oxidative degradation is a serious issue for the long-term performance of HXLPE prostheses.