What happens as the polyethylene interface ages?
UHMW PE cup inserts for hip implants have proven themselves in practice and are now state-of-the-art. The results of studies of their use over a period of more than 25 years have been published, and standards have since been issued that lay down the material specification and sterilisation procedures to be followed. Providing these standards are observed, one can assume that the material qualities will change only within known limits, even over a very long period. This calculable change, or embrittlement, of the polyethylene has been taken into consideration in the design. Furthermore, with “sandwich” inserts the hardening of the polyethylene is of less importance than with pure polyethylene shells since direct articulation and wear do not bring about a reduction in wall thickness.
