In Vivo Analysis of Polyethylene Wear Particles After Total Knee Arthroplasty: The Influence of Improved Materials and Designs

Abstract

Polyethylene wear particles induce macrophages to release cytokines, which can lead to osteolysis and aseptic loosening of total joint prostheses1. The generation of polyethylene wear particles is one of the most important factors that affects the midterm and long-term clinical results associated with total knee arthroplasty2,3. The generation of polyethylene wear particles is correlated with the activity level of the patient4, and greater demands are placed on a total knee prosthesis when it is implanted in a younger, more active patient5. Therefore, to achieve better long-term results for patients who have higher activity levels, modifications of materials (i.e., highly cross-linked polyethylene and alumina ceramic) and design (i.e., mobile bearing and medial pivot) have been developed to reduce polyethylene wear after total knee arthroplasty. It takes decades to evaluate the long-term results of newly introduced total knee prostheses. Thus, it is particularly important to examine in vivo polyethylene wear generation in new prostheses before they come into widespread use. It is difficult to determine the in vivo polyethylene wear of total joint prostheses (with the exception of total hips) with use of postoperative radiographs. To measure polyethylene wear in vivo, we developed and employed a method in which we isolated and analyzed polyethylene wear particles in the synovial fluid of knees that had a well-functioning total knee prosthesis6-9. The number, size, and shape of polyethylene wear particles have been reported to be critical factors in the development of osteolysis. Greater volume, submicrometer size, and an elongated shape of polyethylene wear particles all stimulate an increased macrophage response10-12. Our hypothesis was that modification of total knee arthroplasty materials and designs can influence the generation of polyethylene wear particles in vivo. In the present study, …