Low-voltage scanning electron microscopic imaging of ultrahigh-molecular-weight polyethylene.

Submicron ultrahigh-molecular-weight polyethylene (UHMWPE) wear particles from total joint prostheses may contribute to implant failure through particle-mediated aseptic loosening. The purpose of this study was to examine the microstructure of virgin UHMWPE powder to determine its morphology for future comparison with wear debris. A new method of low-voltage scanning electron microscopy (LVSEM) in an oil-free vacuum was applied, which produced high-resolution images of UHMWPE micromorphology, while minimizing specimen damage and obviating the need for image processing. GUR 415 UHMWPE virgin powder particles were examined by using routine high-voltage SEM, LVSEM, and image analyses. LVSEM showed that UHMWPE particles were composed of submicron-size spherical subparticles connected by numerous nanometer-size fibrils. These spherical subparticles had a highly textured surface morphology seen only by LVSEM. Fracture of the nanometer-size fibrils was observed. Routine high-voltage SEM obfuscates the intricate and delicate UHMWPE micromorphology as well as the damage done by the accompanying high-voltage electrons. This study suggests that the micromorphology of wear particles previously studied with routine high-voltage SEM was overlooked or damaged, justifies the need for LVSEM in future studies, and raises the question of what is the true morphology of polyethylene wear debris retrieved from human tissues.