THE SYNOVIAL RESPONSE TO INTRAARTICULAR INJECTION IN RATS OF POLYETHYLENE WEAR PARTICLES

To study the effect on tissues of wear particles commonly released fro m the articulating surfaces of joint prostheses, ultra-high-molecular- weight polyethylene particles were prepared in a joint simulator and i njected into rat knees. The particles caused synovial proliferation an d induced a macrophage and multinucleate giant-cell response in the su bsynovium. Of particular interest was the macrophage response to parti cles ranging from 5 mum in maximum dimension to the limits of resoluti on of the light microscope, the multinucleate giant-cell response occu rred in response to larger particles and aggregates of small particles . These findings emphasize the importance of wear particles in causing an adverse tissue response around joint replacements having a polyeth ylene component. The difference in cellular response to wear particles of different size suggests that not only the prosthesis material but also the pattern of wear and size of wear particles produced at the ar ticulating surfaces of a prosthesis will determine the type of cellula r response.