Post-treatment of gamma-sterilized UHMWPE.

摘要

The majority of UHMWPE implants undergo gamma-sterilization before implantation in the human body. One of the side effects of this process is crosslinking reactions, which are desirable in their ability to improve material wear resistance. However, the accompanying chain scission reactions act to degrade the mechanical properties of UHMWPE. Concern over UHMWPE wear in total joint replacements arises from increasing clinical and laboratory evidence of adverse biological responses to wear debris particles. Wear particles are treated as foreign bodies, initiating a sequence of reactions that lead to implant loosening and overall prosthetic failure.;This study investigates the ability of a post-sterilization treatment of time, temperature and pressure to promote reactions which maximize crosslinking and minimize the susceptibility of UHMWPE to oxidative chain scission. Samples with doses of 40, 80, and 120 kilograys were exposed to temperatures ranging from 50 to 110°C, and pressures ranging from 15 to 1500 psi, for time periods ranging from 4 to 168 hours. Analysis of crosslink density, oxidative chain scission, percent crystallinity, and mechanical properties were carried out. Potential in-vivo wear was studied through the measurements of crosslink density as measured through swelling measurements.;A post-treatment at 110°C for 4 hours at a pressure of 15 psi applied to a 40 kGy sample resulted in a swelling ratio only previously achievable with an 80 kGy exposure. This treatment also resulted in a lowering of the oxidative chain scission to below that of an 80 kGy sample. This scenario also holds true between 80 kGy and 120 kGy.