A NEW HIGHLY CROSSLINKED ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE (UHMWPE) DOPED WITH HINDERED AMINE LIGHT STABILIZER (HALS) FOR APPLICATIONS IN LARGE JOINT REPLACEMENTS.

Since its introduction in total hip replacements in the 1960's, Ultra High Molecular Weight Polyethylene (UHMWPE) has played a major role as a bearing component material for joint arthroplasty. Concerns were raised when issues of wear resistance became apparent, and therefore Highly Crosslinked Polyethylenes were introduced. Such materials undergo a thermal treatment to quench the free radicals and reduce progressive oxidation.However, said thermal treatment weakens the material mechanical properties and hence the use of antioxidants has been proposed and implemented in clinical use, mainly Vitamin-E. This can be added to the material before or after irradiation. If it is done before, part of the anti-oxydant is consumed during irradiation and so will not be available for its main purpose, and part reacts before irradiation with the free radicals thus reducing the crosslinking effect. If it is added after irradiation, high temperatures are required in order to diffuse it in the bulk material, and anyway t...