Muscular Pronation in First Metatarsal After Hallux Valgus Osteotomies: A Biomechanical Simulation Study

Metatarsal pronation has been reported to be a significant recurrence factor for hallux valgus after corrective osteotomies. However, the extent of pronation correction with distal metatarsal I osteotomies varies greatly from patient to patient without the reason being known. The objective of this study was to describe the effect of the metatarsal I osteotomy angle on muscular torque, acting on the first metatarsal. The primary hypothesis was that a varying angle for the transversal cut affects the muscular pronating torque in the first metatarsal. Therefore, three different 3‐dimensional foot models have been created, and a distal metatarsal I corrective osteotomy was simulated. The transverse cut of the osteotomy was varied from three different angles (−10°, 0°, 10°). Torque and the pro‐/supinating component of eight muscles acting on the first metatarsal have been calculated. No significant difference in pro‐/supinating torque acting on the first metatarsal was found between different osteotomy angles. Nevertheless, the lateral shift of the osteotomized metatarsal‐I‐head in ReveL osteotomy increased supinating torque in almost all analysed muscles, regardless of the angle of the osteotomy. Hence, a tendency ( p  = 0.082) towards less muscular pronating torque could be shown for all ReveL osteotomies compared to the non‐osteotomized status quo. This increased supination was significant especially for the analysed flexors and adductor hallucis caput obliquus.