Purpose Medial opening wedge supramalleolar osteotomy (MOWSMO) is a widely used joint-preserving surgical option for treating varus ankle osteoarthritis. Although recognized as effective, long-term data remain limited, particularly for Takakura–Tanaka stage IIIB. This study evaluated the clinical and radiographic outcomes of MOWSMO after a minimum seven year follow-up, focusing on stage IIIB case durability and stability. Methods This retrospective study included 42 ankles (39 patients) with varus ankle osteoarthritis who underwent MOWSMO between 2009 and 2019 with a minimum follow-up of seven years. Demographic factors, surgery-related data, clinical outcomes (AOFAS and FAAM scores), and radiographic parameters, including tibial plafond inclination (TPI), talar inclination (TI), and talar tilt (TT), were evaluated. Subgroup analysis was performed for stage IIIB patients to compare those with and without radiographic stage improvement. Results The mean follow-up was 106.2 months. Radiographic improvement was observed in 71.4% and 85.0% of the stage II and IIIA ankles, respectively. In cases of failure, a “paradoxical increase” in TT occurred owing to excessive valgus TPI, whereas TI remained in varus. Among stage IIIB ankles, 26.7% showed radiographic stage improvement, whereas 73.3% remained unchanged. Patients with stage IIIB who improved had a significantly lower body mass index (BMI, 22.9 vs. 26.9 kg/m2; P = .012) and a smaller medial opening length (11.3 vs. 7.4 mm; P = .015). Postoperative TT significantly increased in the non-improvement group (2.8 degrees increase) compared to the stage-improvement group (3.1 degrees decrease, P = .01). At the final follow-up, clinical scores improved significantly across the entire cohort; notably, the stage improvement group in stage IIIB achieved significantly higher clinical scores than the non-improvement group (mean AOFAS: 82.4 vs. 73.2; FAAM-ADL: 82.1 vs. 68.1; FAAM-sports: 76.9 vs. 64.3; P = .001, all). Conclusions MOWSMO is a reliable joint-preserving procedure for Takakura stage II and IIIA varus ankle osteoarthritis with high success rates over seven years. Clinically, surgical success depends on avoiding overcorrection, as excessive distal tibial valgization causes a mechanical discrepancy that paradoxically increases the TT. Our finding emphasizes that precise control of the medial opening width is a crucial practical criterion to prevent long-term joint degeneration, especially in stage IIIB cases.

Mid- to long-term outcomes of medial opening wedge supramalleolar osteotomy for varus ankle osteoarthritis: a minimum seven-year follow-up study

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发表日期：

2026年7月4日

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Jun Young Choi,
Sun Oh Jung,
Ji Yong Yun,
Jin Soo Suh

摘要

Purpose

Medial opening wedge supramalleolar osteotomy (MOWSMO) is a widely used joint-preserving surgical option for treating varus ankle osteoarthritis. Although recognized as effective, long-term data remain limited, particularly for Takakura–Tanaka stage IIIB. This study evaluated the clinical and radiographic outcomes of MOWSMO after a minimum seven year follow-up, focusing on stage IIIB case durability and stability.

Methods

This retrospective study included 42 ankles (39 patients) with varus ankle osteoarthritis who underwent MOWSMO between 2009 and 2019 with a minimum follow-up of seven years. Demographic factors, surgery-related data, clinical outcomes (AOFAS and FAAM scores), and radiographic parameters, including tibial plafond inclination (TPI), talar inclination (TI), and talar tilt (TT), were evaluated. Subgroup analysis was performed for stage IIIB patients to compare those with and without radiographic stage improvement.

Results

The mean follow-up was 106.2 months. Radiographic improvement was observed in 71.4% and 85.0% of the stage II and IIIA ankles, respectively. In cases of failure, a “paradoxical increase” in TT occurred owing to excessive valgus TPI, whereas TI remained in varus. Among stage IIIB ankles, 26.7% showed radiographic stage improvement, whereas 73.3% remained unchanged. Patients with stage IIIB who improved had a significantly lower body mass index (BMI, 22.9 vs. 26.9 kg/m²; P = .012) and a smaller medial opening length (11.3 vs. 7.4 mm; P = .015). Postoperative TT significantly increased in the non-improvement group (2.8 degrees increase) compared to the stage-improvement group (3.1 degrees decrease, P = .01). At the final follow-up, clinical scores improved significantly across the entire cohort; notably, the stage improvement group in stage IIIB achieved significantly higher clinical scores than the non-improvement group (mean AOFAS: 82.4 vs. 73.2; FAAM-ADL: 82.1 vs. 68.1; FAAM-sports: 76.9 vs. 64.3; P = .001, all).

Conclusions

MOWSMO is a reliable joint-preserving procedure for Takakura stage II and IIIA varus ankle osteoarthritis with high success rates over seven years. Clinically, surgical success depends on avoiding overcorrection, as excessive distal tibial valgization causes a mechanical discrepancy that paradoxically increases the TT. Our finding emphasizes that precise control of the medial opening width is a crucial practical criterion to prevent long-term joint degeneration, especially in stage IIIB cases.