Post electron-beam irradiation oxidation of orthopaedic UHMWPE stabilized with Vitamin E

Ultra-High Molecular Weight PolyEthylene (UHMWPE) has been the material of choice for load-bearing articular components used in total joint arthroplasty in the past 30 years. However, the durability of the whole implant has often been compromised by oxidation of UHMWPE components. Since the use of a suitable, biocompatible stabilizer would minimize this inconvenience, it has been introduced the possibility to use Vitamin E. In the present work, medical grade UHMWPE was blended with 1.1, 2.3 and 11 mmol/l of Vitamin E and consolidated by compression moulding. Small block of reference and of Vitamin E-blended UHMWPE where then electron beam irradiated at 30, 60 and 90 kGy, both in vacuum and in air. FTIR spectroscopy was used to monitor changes in both the polymer. Thin sections of virgin and Vitamin E-blended UHMWPE irradiated were aged in air, at room temperature and in the dark and the kinetic of oxidation was followed by FTIR. The reaction between Vitamin E and macro alkyl radicals or unlikely with peroxy radicals has been demonstrated and a correlation between the decrease of macro radicals and the stabilization effect of Vitamin E has been shown.