Sensitization to implant components is associated withjoint replacement failure; Identification and revision to non-allergenic hardware improves outcomes.

Abstract Background Over 90% of 1 million yearly US joint replacements are highly successful. Nonetheless, 10% do poorly, attributed to infection or mechanical issues. Many implant components are sensitizers, and sensitization could also contribute to implant failure. Objective Determine the prevalence of implant sensitization in joint failure patients, their clinical characteristics, and implant revision outcomes. We hypothesized that sensitized patients should improve when revised with non-‘allergenic’ materials. Methods We prospectively enrolled n=105 joint failure patients referred by their orthopedic surgeon who had already excluded infection or mechanical causes. Patients provided informed consent, completed a history & physical exam, patch testing to metals and bone cement, and a Nickel lymphocyte proliferation test (Ni-LPT). A study coordinator was able to contact 64% (n=67) 9–12 months later to evaluate outcomes. Results 59% were sensitized to an implant component: 32% to metal and 37% to bone cement. The Ni-LPT was 60% sensitive and 96% specific in diagnosing nickel sensitization. Most sensitized subjects reported no or uncertain histories of reactions to the specific material(s). Implant sensitized patients were younger, reported previous eczema, joint itching, and implant loosening. 9-12 months later, most patients with a revised implant (‘revised’) described significant improvement (16/22 revised for sensitization, p=0.0003, vs. 9/13 revised without sensitization, p=0.047) compared to patients without implant revision). All revised patients with sensitization used components to which they were not sensitized. Pain (p=0.001), swelling (p=0.035), and instability (p=0.006) were significantly reduced in the revised sensitized group. Conclusions Sensitization to implant components is an important cause of unexplained joint replacement failure. Joint revisions based on sensitization information resulted in significant improvements.