Midterm Outcomes Following Conversion of Failed Ankle Arthrodesis to Total Ankle Arthroplasty, Including Patients With a Deficient Fibula.

Background: Previous studies of conversion of failed ankle arthrodesis to total ankle arthroplasty showed failure in patients with an absent distal fibula, and more recently that has been considered a contraindication. However, these conclusions were based on limited case series with older prosthetic designs, and the potential for successful conversion in this challenging patient population remains unclear. This retrospective study examines the midterm follow-up of 21 patients treated for a conversion of failed ankle arthrodesis by a single surgeon using a standard technique with a single prosthesis, with a focus on the treatment of 5 patients with a deficient distal fibula. Methods: Between May 2010 and August 2019, 27 patients underwent conversion using a prosthesis with an intramedullary tibial component, 21 of which were available for the study. Six patients had a deficient distal fibula, and 5 were available for follow-up. Our primary outcome measure was having a total ankle arthroplasty in place. Secondary outcomes were evaluated postoperatively with a visual analog scale, the American Orthopaedic Foot & Ankle Society (AOFAS) ankle and hindfoot score, a satisfaction survey, and radiographic assessment of the arthroplasty and any concomitant hindfoot fusions. Results: Mean follow-up for all patients was 7.6 (2.6-11.8) years, with follow-up of the deficient fibula group of 8.2 (4.9-11.8) years. Complications included malleolar fracture with or without subsequent surgery (n = 5), varus deformity (n = 1), and wound dehiscence or infection (n = 2). At final follow-up, all patients, including the 5 with a deficient distal fibula, had an intact ankle arthroplasty, although 3 with intact fibulas had undergone prosthetic revision. Postoperative dorsiflexion was 4.5 ± 5.1 degrees and plantarflexion 20.9 ± 13.37 degrees. There were no pseudarthroses in the 11 patients with concomitant hindfoot arthrodesis. Mean (±SD) VAS score was 4.4 ± 3.0 and AOFAS score was 71.2 ± 21.7. Sixty-seven percent reported that they were satisfied or very satisfied, with 16% dissatisfied or very dissatisfied. One of the deficient fibula patients was very dissatisfied. Seventy-six percent had no limitations with activities of daily living and two-thirds of those had no limitations at all. Conclusion: Consistent with previous studies, we find that total ankle arthroplasty can be a satisfactory salvage procedure for patients with a failed ankle arthrodesis. Unlike previous reports, we observed high prosthetic retention in patients with a deficient fibula, although pain relief and range of motion outcomes were mixed, and some patients required revision surgery. These findings should be interpreted in light of the intrinsic limitations of a small sample size, lack of preoperative comparison data, and incomplete follow-up in the deficient fibula group. Level of Evidence: Level IV, clinical research.