The Synovial Response to Intraarticular Injection in Rats of Polyethylene Wear Particles

To study the effect on tissues of wear particles commonly released from the articulating surfaces of joint prostheses, ultra-high-molecular-weight polyethylene particles were prepared in a joint simulator and injected into rat knees. The particles caused synovial proliferation and induced a macro-phage and multinucleate giant-cell response in the subsynovium. Of particular interest was the macro-phage response to particles ranging from 5 pm in maximum dimension to the limits of resolution of the light microscope; the multinucleate giant-cell response occurred 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 polyethylene 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 articulating surfaces of a prosthesis will determine the type of cellular response.