Ankle Arthrodesis Associated With Risk of Progression to Subtalar Arthrodesis Compared to Total Ankle Arthroplasty.

Background: It is unknown how the increased range of motion and improved gait mechanics provided by total ankle arthroplasty (TAA) affects the progression of subtalar arthritis compared with ankle arthrodesis (AA). We hypothesized that patients treated with TAA would have a lower incidence of postoperative subtalar arthrodesis (SA) compared to AA. Methods: We retrospectively reviewed a matched cohort of 2105 AA and 2105 TAA surgeries performed between January 1, 2016, and December 31, 2022, using a commercial claims database. Patients with a history of preoperative ipsilateral SA were excluded. Patients were matched 1:1 for gender, age, indication for ankle surgery, and obesity at time of ankle surgery. The primary endpoint was the cumulative incidence of subtalar arthrodesis following the index ankle procedure. Univariate and multivariate regression analyses were performed. Significance was set at Results: Demographics were similar between cohorts, including age, gender, presence of obesity, and length of follow-up. At the 5-year time point, the cumulative incidence of subtalar arthrodesis was 42 SAs for every 1000 AAs (4.2%, absolute risk [AR] = 1.425%), compared with 14 SAs for every 1000 TAAs (1.4%, Conclusion: In this study, we found a significantly higher incidence of subtalar arthrodesis following AA compared with TAA. Surgeons may consider the risk of progression to SA when deciding between TAA and AA for patients with advanced ankle arthritis, particularly in preoperative counseling for patients without existing subtalar arthritis, as TAA may offer an opportunity to mitigate this risk. Level of Evidence: Level III, retrospective comparative study.