Changes in foot and ankle offset between minimally invasive distal first metatarsal osteotomy and modified Lapidus procedures in hallux valgus.

BACKGROUND: Hindfoot malalignment is common in hallux valgus (HV), but its correction after HV surgery remains unknown. This study evaluated a distal first metatarsal osteotomy versus modified Lapidus on hindfoot alignment. METHODS: This retrospective study identified HV patients following a Lapidus arthrodesis or distal first metatarsal bunionectomy and compared radiographic outcomes. Using preoperative and postoperative weight-bearing CT, hindfoot alignment was measured according to the Foot and Ankle Offset (FAO), calcaneus offset, and hindfoot angle. Linear regressions assessed the association between procedure type and FAO change. RESULTS: Seventy-three patients were included. Baseline and postoperative forefoot radiographic measures were similar. Lapidus procedure demonstrated a greater magnitude change in hindfoot alignment, including FAO (2.02% vs 0.94%), calcaneus offset (3.6 mm vs 1.64 mm), and hindfoot angle (6.14° vs 3.10°) (p < 0.001). The distal osteotomy had a smaller FAO change after adjustment (p < 0.001). CONCLUSION: Although Lapidus statistically shifted the FAO, neither forefoot procedure demonstrated a clinically meaningful change in hindfoot alignment. LEVEL OF EVIDENCE: III, Retrospective cohort study.