Secondary Arthrodesis After Total Ankle Arthroplasty.

BACKGROUND: While it is thought that stresses through the subtalar and talonavicular joints will be decreased after total ankle replacement (TAR) relative to ankle fusion, progressive arthritis or deformity of these joints may require a fusion after a successful TAR. However, after ankle replacement, it is unknown how hindfoot biomechanics and blood supply may be affected. Consequently, subsequent hindfoot joint fusion may be adversely affected.

METHODS: We retrospectively identified a consecutive series of 1001 primary TARs performed between January 1998 and December 2014. We identified patients who underwent a secondary triple, subtalar or talonavicular arthrodesis to treat progressive arthritis or pes planus deformity. Clinical outcomes including pain and functional outcome scores, revision procedures, delayed union, nonunion, complications, and failure rates were recorded. Twenty-six patients (2.6%) required a subtalar (18), talonavicular (3), talonavicular and subtalar (3), or triple arthrodesis (2). Of these patients, 14 (54%) were males with an average age of 63.2 years and a mean 70.9 months follow-up. We then compared these patients to 13 patients who had a subtalar fusion after an ankle arthrodesis.

RESULTS: The most common type of fixation used was 2 variable-pitch screws across each joint. Fresh-frozen allograft cancellous chips were the most common supplement to the fusion construct (80.8%). The mean time between TAR and secondary fusion procedure was 37.5 months. Overall, 92.3% of the patients went on to fusion. Two patients (7.7%) had a delayed union and 2 patients had a nonunion (7.7%) and were considered operative failures. There were 3 repeat procedures related to the arthrodesis procedure: 1 conversion of a subtalar to a triple arthrodesis, 1 revision talonavicular fusion, and 1 revision subtalar fusion. The average time to weight bearing after arthrodesis was 8.7 weeks; the mean time to radiographic and clinical fusion was 26.5 weeks. There were no secondary complications associated with the arthrodesis. Pain and functional outcome scores improved significantly. There were no differences in the rates of subsequent fusions among implant choices, though the time to fusion in the mobile-bearing prosthesis was significantly longer than the 2 fixed-bearing prostheses. Compared with the data of 13 patients with prior ipsilateral ankle arthrodeses and subtalar fusions, patients who had an ankle replacement had a higher fusion rate (P = .03) and had a similar time to fusion.

CONCLUSION: Hindfoot arthrodesis following a TAR was safe and effective in improving function and pain. Additionally, a hindfoot arthrodesis following a TAR had a higher fusion rate than a subtalar fusion following an ankle arthrodesis. Although the time to healing was relatively long, various hindfoot fusions were used to treat progressive arthritis and deformity with high fusion rates.

LEVEL OF EVIDENCE: Level III, comparative case series.