Ankle Arthrodesis Increases Risk of Progression to Subtalar Arthrodesis Compared to Total Ankle Arthroplasty

Category: Ankle Arthritis; Hindfoot Introduction/Purpose: There is a known association between ankle arthritis and ipsilateral subtalar arthritis. It is unknown how the increased range of motion and improved gait mechanics provided by total ankle arthroplasty (TAA) effects the progression of subtalar arthritis compared to 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 2564 AA and 3014 TAA performed between 1/1/2016 and 12/31/2022 using a commercial claims database. Patients with a history of an ipsilateral subtalar arthrodesis preoperatively were excluded. Records were reviewed for demographics, medical history, and postoperative subtalar arthrodesis up to 5 years after AA or TAA. Patients who underwent a TAA tended to be older (mean=58.62 versus 53.80 years, p< 0.001), but gender (p=0.098) and obesity (p=0.225) were similar between cohorts). TAAs were more likely to be diagnosed with osteoarthritis (53.32% versus 41.38%), posttraumatic arthritis (41.80% versus 38.53%), rheumatoid arthritis (1.53% versus 0.98%), or psoriatic arthritis (0.07% versus 0.00%) and less likely to be indicated due to another diagnosis (19.11% versus 3.28%, p< 0.001). Mean follow-up was 2 years in both cohorts. Results: Cumulative incidence of an ipsilateral subtalar arthrodesis was higher at 5 years with an AA (4.20%, 95% confidence interval (CI)=2.60%-5.80%) than a TAA (1.30%, CI=0.60%-2.00%, p=0.004). A multivariate analysis showed that AA increased the risk of progressing to subtalar arthrodesis compared to TAA (OR=1.95, CI=1.08-3.52, p=0.027), but not age (OR=0.98, CI=0.96-1.01, p=0.183), female gender (OR=1.16, CI=0.68-1.99, p=0.587), obesity (OR=1.74, CI=0.93-3.26, p=0.083), posttraumatic arthritis (OR=1.04, CI=0.57-1.90, p=0.896), inflammatory arthritis (p=1.000), or another diagnosis (OR=1.60, CI=0.75-3.40, p=0.224) compared to osteoarthritis. For those patients who underwent an ipsilateral subtalar arthrodesis, patients in the TAA cohort tended to wait longer before proceeding with the subtalar arthrodesis (mean=1.78 years (range=0.002-4.62 years) than the AA cohort (mean=1.11, range=0.10-3.62 years, p=0.049). Conclusion: There is a significantly higher incidence of patients undergoing subtalar arthrodesis after AA compared to TAA. For those patients who required a subtalar arthrodesis, patients with a TAA tended to wait longer before undergoing the subtalar arthrodesis compared to those with an AA. We recommend that surgeons consider TAA over AA, especially in patients with minimal subtalar arthritis as a strategy to help delay the progression of subtalar arthritis. Cumulative incidence of an ipsilateral subtalar arthrodesis was higher at 5 years with an AA (4.20%, 95% confidence interval (CI)=2.60%-5.80%) than a TAA (1.30%, CI=0.60%-2.00%, p=0.004).