Analysis of Retrieved Agility™ Total Ankle Arthroplasty Systems

Background. First generation total ankle arthroplasty (TAA) systems showed high rates of failure. The Agility (TM) (DePuy, Warsaw, IN) TAA system, a second generation design, had improved outcomes; however, implant failure due to loosening of the metallic components persisted. The purpose of this study was to analyze the damage modes and radiographic mode(s) of failure observed in retrieved Agility (TM) TAA. Materials and Methods: Ten devices were collected and each component was analyzed for common damage modes using microscopy. Clinical damage was analyzed with postoperative implant and preoperative revision procedure radiographs. Results: Analyses revealed damage/wear to retrieved components, including abrasion, dishing, and pitting. These third-body wear particles may be a precursor to wear debris induced osteolysis which could cause component loosening. Seven TAA systems were removed due to loosening or subsidence, suggesting component damage/wear may lead to clinically observed component loosening. Retrieval analysis indicated the polyethylene experiences edge loading, resulting in increased contact stresses to polyethylene in the primary articulation region and wear. Conclusion: Since poor clinical outcomes have been associated with component instability and osteolysis, analyzing retrieved components wear and damage may be an important step toward improving implant design, thereby decreasing wear debris induced osteolysis and improving clinical outcomes.