Wear of orthopaedic implants — A scanning electron microscope study

Three metallic implants were removed from patients after episodes of pain and the observation of bony radiolucency was indicative of loosening. Gross observation of the implants revealed areas of wear. Sections of the granulation tissue around the implants revealed finely divided metallic debris in the size range 1–60 μm. A technique was devised to isolate these particles for examination in the scanning electron microscope (SEM). Particulate morphologies were observed and were shown to be consistent with the degree of inflammatory response adjacent to the implant in vivo. SEM studies of particles generated in in vitro experiments and of Xantopren replicas of the surfaces of the implants were also performed. The particles generated in the laboratory and the roughness on the surfaces of the implants were remarkably similar to those particles that had accumulated in the living tissue, both in size and in morphology. These observations are consistent with a brittle abrasive wear phenomenon operating on the implants in vivo. Minimal corrosion of the debris appears likely. The importance of proper stabilization of the implants against loosening is emphasized.