Prevalence and radiological characteristics of the dislocation of the second metatarsophalangeal joint in patients undergoing hallux valgus surgery; a matched control study.

BACKGROUND: Hallux valgus (HV) is occasionally associated with chronic subluxation or dislocation (CS/D) of the second metatarsophalangeal joint (2MTPj). The present study aimed to radiographically investigate the prevalence and characteristics of HV with CS/D of the 2MTPj compared with matched controls. METHODS: Dorsoplantar and lateral weight-bearing radiographs of 79 female patients (79 feet) who had HV with an age of 50 years or more were reviewed. All feet were treated with a proximal supination osteotomy for correction of HV. CS/D of the 2MTPj was evaluated on preoperative dorsoplantar and lateral radiographs. HV and intermetatarsal (IM) angles were measured. Seventy-nine feet were divided into two groups: Group CD (16 feet) had HV with CS/D of the 2MTPj, and Group non-CD had HV without the CS/D of the 2MTPj (63 feet). The severity of HV was divided into two grades according to the HV angle: moderate deformity (Group M, 36 feet, HV angle of less than 40°) and severe deformity (Group S, 43 feet, HV angle of 40° or greater). Group CD and non-CD, and Group M and S were matched by age, gender, and BMI. RESULTS: The prevalence of CS/D of the 2MTPj was 20.3%. Group CD had a significantly higher HV angle (p = 0.0001) and a significantly higher IM angle (p = 0.042) than Group non-CD. The prevalence of CS/D of the 2MTPj in Group S (34.9%) were significantly higher than that in Group M (2.8%) (p < 0.001). CONCLUSIONS: CS/D of the 2MTPj was significantly associated with greater HV and IM angles compared with matched controls. The prevalence of CS/D of the 2MTPj (34.9%) in Group S was significantly higher than that in Group M. Severe HV can be at higher risk of acquiring CS/D of the 2MTPj in middle-aged and older females.