Radiographic changes in midfoot alignment after hallux valgus correction with and without concomitant second tarsometatarsal arthrodesis: a comparative study.

INTRODUCTION: Second tarsometatarsal (TMT) joint osteoarthritis occurs in a subset of patients with hallux valgus (HV). While second TMT arthrodesis is performed to address symptomatic arthritis, its association with midfoot alignment changes during HV correction remains unclear. This study aimed to compare changes in radiographic arch parameters between patients undergoing HV correction with and without concomitant second TMT arthrodesis. MATERIALS AND METHODS: This retrospective comparative study included 73 feet with HV and medial column malalignment (lateral Meary's angle > 10°). The TMT group (n = 37) underwent HV correction combined with second TMT arthrodesis for symptomatic osteoarthritis, while the control group (n = 36) underwent isolated HV correction. These patients were matched to achieve comparable baseline characteristics. Radiographic parameters of the transverse arch (M2-M5 angle, C1-M2 distance) and medial column alignment (lateral Meary's angle) were evaluated preoperatively and at a minimum 1-year follow-up. Functional outcomes were assessed as a secondary measure. RESULTS: The TMT group demonstrated greater changes in transverse arch parameters compared with the control group. The M2-M5 angle decreased by 2.1° (95% CI, 1.4° to 2.7°) in the TMT group, whereas no significant change was observed in controls (-0.2°; 95% CI, -0.7° to 0.4°). The C1-M2 distance changed by 0.7 mm (95% CI, 0.5 to 0.9) in the TMT group and -0.2 mm (95% CI, - 0.3 to -0.1) in controls. Medial column alignment also changed to a greater extent in the TMT group, with a reduction in lateral Meary's angle of 6.4° (95% CI, 5.0° to 7.9°), compared with 0.7° (95% CI, -0.7° to 2.1°) in controls, demonstrating a significant between-group difference. Both groups showed improvement in functional outcomes, with largely comparable postoperative scores. CONCLUSION: Second TMT arthrodesis performed during HV correction was associated with greater changes in transverse and medial arch parameters compared with HV correction alone. Functional outcomes were generally comparable between groups, although the clinical significance of the radiographic differences remains uncertain. LEVEL OF EVIDENCE: Level III, Therapeutic Study.