Characteristics of Wear Particles and Osteolysis

Abstract

In view of the mechanism and the prevention of osteolysis, the relationship between characteristics of wear particles and osteolysis was focused on in our studies. First, interface tissues with adjacent bone were retrieved and histopathologically investigated with reference to the cells on the bone surface. Macrophages were the most common cells in osteolytic lesions, and polyethylene particles were shown to play a significant role in macrophage recruitment. Second, polyethylene particles were extracted by a tissue digestion method and characterized with scanning electron microscopy. The shape and the size of the particles were similar between osteolysis-positive and -negative lesions, while the number of particles was significantly greater in osteolysis-positive lesions. The critical number of particles for osteolysis was estimated to be around 10 billion per gram of wet interface tissue. Finally, an animal model for osteolysis was created, and various interface conditions and particles were compared concerning the prevention of osteolysis. The polyethylene particles increased the amount of interposed fibrous tissue between bone and implant only when a great amount of fibrous tissue interposition had already existed. In contrast to the polyethylene particles, the alumina particles showed no adverse effect.