Polyethylene synovitis following canine total hip arthroplasty. Histomorphometric analysis

The synovial membrane response to polyethylene wear debris was analyzed in canine total hip arthroplasties (THA). Fifty-four THAs were performed in healthy, mature dogs. None of the arthroplasties demonstrated clinical or radiographic signs of loosening. Synovial membrane biopsies were harvested 4 (n = 13), 6 (n = 5), 8 (n = 8), 12 (n = 15), and 24 (n = 6) months after surgery and were scored for inflammation, polyethylene (PE) wear debris, histiocyte density, and membrane thickness. The amount of PE wear debris tended to increase with time. However, the inflammatory changes within the joint capsule and synovial membrane did not progress, and the total thickness of the alveolar and surface layers decreased (P = .008). It appears that the amount of wear debris at 2 years in canine hip arthroplasties, without evidence of loosening, is well tolerated by the joint capsule.