Biomechanical evaluation of the first ray in pre-/post-operative hallux valgus: A comparative study

Background: Deformity of the first ray in hallux valgus patient has been deemed to mainly contribute to instability of the metatarsophalangeal joint. However, it is not clear whether the fixation of the distal osteotomy fragment and transposition of the sesamoid represent the best method for hallux valgus treatment. The aim of this study was to examine how postoperative hallux valgus osteotomy affects the stability of the first ray. Methods: To accurately investigate the biomechanical behavior of the first ray in pre-/postoperative hallux valgus patients, we described the relative displacement and stress distribution of the first metatarsal bone and sesamoid by imageology, test measurement and foot finite element model. Findings: Compared with the preoperative hallux valgus, the plantar pressure decreased by 47.8% and was redistributed on second metatarsal region. The peak stress and relative displacement of the distal osteotomy fragment increased by +55.7% and −59.9%, respectively. The movement of this component shifted toward the positive sagittal axis direction. In addition, the relative displacement of sesamoid decreased by 87.4% (0.18 mm) in vertical axis direction and the stress was also redistributed on medial and lateral region. Moreover, the strain of the medial main ligament was more favorable to reconstruct function of the first ray. Interpretation: The findings showed that the osteotomy method was helpful for stability of the first ray. This would provide the stability suggestions for postoperative hallux valgus fixation and guide further rehabilitation.