Ballooning osteolysis in 71 failed total ankle arthroplasties

Background and purpose — Aseptic loosening is a major cause of failure in total ankle arthroplasty (TAA). In contrast to other total joint replacements, large periarticular cysts (ballooning osteoly- sis) have frequently been observed in this context. We investigated periprosthetic tissue responses in failed TAA, and performed an element analysis of retrieved tissues in failed TAA. Patients and methods — The study cohort consisted of 71 patients undergoing revision surgery for failed TAA, all with hydroxyapatite-coated implants. In addition, 5 patients under- going primary TAA served as a control group. Radiologically, patients were classifi ed into those with ballooning osteolysis and those without, according to defi ned criteria. Histomorphomet- ric, immunohistochemical, and elemental analysis of tissues was performed. Von Kossa staining and digital microscopy was per- formed on all tissue samples. Results — Patients without ballooning osteolysis showed a generally higher expression of lymphocytes, and CD3+, CD11c+, CD20+, and CD68+ cells in a perivascular distribution, compared to diffuse expression. The odds of having ballooning osteolysis was 300 times higher in patients with calcium content > 0.5 mg/g in periprosthetic tissue than in patients with calcium content ≤ 0.5 mg/g (p < 0.001). Interpretation — There have been very few studies investi- gating the pathomechanisms of failed TAA and the cause-effect nature of ballooning osteolysis in this context. Our data suggest that the hydroxyapatite coating of the implant may be a contribu- tory factor.