Learning curve of total ankle replacement from the lateral approach

BACKGROUND According to recent systematic reviews and meta-analyses, the long-term results of total ankle replacement (TAR) are equivalent or superior to ankle arthrodesis with an average 10-year survival approaching 90%. Almost all fourth-generation TAR implants are inserted from the anterior approach except for Zimmer™, which is implanted laterally and with lateral malleolus osteotomy. AIM To evaluate the clinical outcomes and complication rates and to define a multifactorial learning curve of lateral approach TAR. METHODS This single-center retrospective cohort study included 85 Zimmer™ lateral-approach TARs performed by one surgeon from 2019 to 2024. Patient-reported outcome measures were evaluated in 65 patients using the Manchester-Oxford Foot Questionnaire (MOXFQ) and European Foot and Ankle Society (EFAS) scores. Underlying diagnoses, functional outcomes, operative time trends, secondary procedures, and complications rates were analyzed to define a learning curve considering the first 60 consecutive cases. RESULTS The mean follow-up was 30.8 months. Post-traumatic arthritis was the most common underlying diagnosis accounting for 53.5% of cases. Mean EFAS improved by 13.0 points (P < 0.001), and MOXFQ decreased by 58.5 points (P < 0.001). Quartile analysis showed no significant change in ΔEFAS or ΔMOXFQ (P > 0.4), indicating that proficiency is readily achieved due to the short learning curve of this technique. Operative time decreased from approximately 175 min to 125 min after about 25-30 cases. Complication rates declined with experience. In the first 30 cases, there were 19 reoperations in 13 patients (43%) with an additional 5 being managed conservatively compared with 10 reoperations in 7 patients (23%) with 2 conservatively treated complications in the subsequent 30 cases (relative risk = 1.86, P > 0.05). Infection-related revisions also decreased markedly from 5 (16.7%) to 1 (3.3%) (relative risk = 5.00, P > 0.05) between these cohort. Two cases of deep infection occurred in patients with rheumatoid arthritis. One was successfully managed with debridement, and the other required implant removal with cement spacer implantation. CONCLUSION Lateral-approach TAR achieved early patient-reported outcome measure benefits with efficiency and safety improving with experience, requiring 30 cases. This rapid learning curve integrates functional outcomes, operative timing, and complication rates.