WEAR PARTICULATE SPECIES AND BONE LOSS IN FAILED TOTAL JOINT ARTHROPLASTIES

The aim of this study was to evaluate the relative contribution of pol yethylene, metal, and polymethylmethacrylate (cement) particles to the overall bone loss in aseptic loosening. Twenty-four interface tissues with adjacent bone were obtained during 17 revision total joint arthr oplasties (11 hips and six knees). Osteoclasts and macrophages were id entified immunohistochemically on the bone surface. The length of the bone surface in contact with these cell types was measured and analyze d with reference to the particulate species present within the fibrous interface. The presence of abundant polyethylene particles significan tly increased the proportion of the bone surface in contact with macro phages but did not have a significant influence on that of osteoclasts . Osteoclastic bone resorption was significantly more extensive in the presence of metal particles. In contrast, the presence of cement part icles did not have a significant influence on macrophage or osteoclast coverage of the bone surface. These results highlight the significanc e of polyethylene particles in macrophage recruitment and subsequent o steolysis and suggest a different mechanism of bone loss related to me tal, namely mediation through osteoclastic activities. The relative co ntribution of cement particles was negligible and needs reevaluation i n light of evidence provided by others.