Periprosthetic osteolysis is considered the main problem limiting the longevity and clinical success of artificial hip joints. Aiming at the reduction of the wear particles and the elimination of periprosthetic osteolysis, we have recently developed a novel articular cartilage-inspired technology for surface modification (Aquala® technology) with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) grafting (100–150 nm in thickness) for an acetabular liner in an artificial hip joint. Our previous study on the mechanical and biological effects of PMPC revealed that the grafting decreased the production of wear particles and the bone resorptive responses. However, as well as wear-resistance, oxidation is an important indicator of the clinical performance of acetabular liners. The incorporation of the antioxidant vitamin E has been proposed recently as an alternative to post melting treatment after gamma-ray irradiation to avoid oxidation. The purpose of this study is to investigate the effects of substrate materials, vitamin E-blended cross-linked polyethylene (CLPE), on the oxidative stability and wear resistance of the PMPC-grafted CLPE liner for artificial hip joints. Vitamin E-blended (0.1 mass%) PE sheet stock was irradiated with a high dose of gamma-rays (100–150 kGy) and annealed for cross-linking (HD–CLPE+E). PMPC grafting onto the HD–CLPE+E liners was performed by a photoinduced polymerization technique. Then, the PMPC-grafted HD-CLPE+E was sterilized by gamma-ray with a dose of 25 kGy. A CLPE with 50 kGy gamma-ray irradiation and 25 kGy gamma-ray sterilization was used as control. Surface properties and oxidative properties of the liners were examined. The wear test was performed using a 12-station hip joint simulator according to the ISO 14242-3. A 26-mm Co-Cr-Mo alloy femoral head component was used for the tests.Introduction
Materials & Methods
