[Scanning electron microscopy studies of morphologic changes in ultra-high molecular weight polyethylene materials after various processing steps].

UNLABELLED: Scanning electron microscopic (SEM) studies were carried out on various orthopaedic implants made of ultra-high molecular weight polyethylene (UHMWPE). Both non-sterilized and gamma-sterilized machined (milled) implants were used. Milled implants showed significant surface irregularities, and cross-sections also revealed irregularities in deeper layers of the polyethylene. In gamma-sterilized implants, cracks measuring 10-30 microns in length were found at a depth of 1.5 to 2.5 mm. Crater-like defects were also occasionally seen. CLINICAL RELEVANCE: On the basis of these findings, direct compression moulding and a sterilization process in which oxygen is eliminated can be recommended as ways of improving the quality of UHMWPE used for orthopaedic implants.