Learning curve of total ankle replacement from the lateral approach

Abstract

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.

Keywords: Arthroplasty replacement ankle; Osteoarthritis; Ankle joint; Surgical procedures operative methods; Surgical approach; Lateral approach; Learning curve; Patient-reported outcome measures

Core Tip: This study provided a multidimensional evaluation of the learning curve in lateral-approach total ankle replacement using the Zimmer™ system. Significant improvements in pain and function were observed as measured by patient-reported outcome measures and remained consistent from the earliest cases, indicating early stabilization of outcomes. Operative time and complication rates improved with surgical experience, plateauing after approximately 25-30 cases. A simultaneous anteromedial approach during the primary procedure may help reduce the need for secondary interventions. Most infection-related complications occurred in patients with rheumatoid arthritis, underscoring the importance of careful preoperative optimization.