Anatomical Risk Factors Associated with Rapid Progression of Hallux Valgus Deformity

CATEGORY: Bunion; Other INTRODUCTION/PURPOSE: Hallux valgus (HV) deformity generally progresses gradually over the long term. However, the deformity progresses rapidly in some patients. Information on the future progression of the deformity helps treatment decision-making of both surgeons and patients. However, few studies have reported the natural progression of HV deformity. The purposes of this study were to clarify 1) the incidence and 2) anatomical risk factors of the rapid progression of HV deformity. METHODS: Patients who visited the foot and ankle clinic of our hospital between 2013 and 2019 were retrospectively analyzed. Inclusion criteria were patients who underwent repeated foot radiographs with an interval of >=2 years. Exclusion criteria were patients <18 years old, history of first ray surgery, deformity or destruction of the first metatarsal head, and unable to stand plantigrade. The increase in HV angle between the baseline and the last follow-up was calculated. Then, patients were dichotomized into two groups: those with an increase in HV angle >=5°(Group P) and those with an increase of <5°(Group S). Radiographic measurements, including HV angle, Hardy’s sesamoid position, distal metatarsal articular angle, rounded metatarsal head, first metatarsal protrusion distance, were performed on the dorsoplantar and lateral foot radiographs at the baseline. The association between the baseline radiographic measurements and progression of HV deformity was assessed using the univariate and multivariate analyses. RESULTS: A total of 268 feet of 268 patients (217 women and 51 men, mean age 61 years) were analyzed. The mean HV angle was 28°, and the mean interval between radiography was 49 months. Forty-five (17%) and 223 (83%) feet were categorized into groups P and S, respectively. The baseline Hardy’s sesamoid position was independently associated with the future progression of the deformity: 6/115 (5%) feet with normal sesamoid (grade <4) were in group P. On the other hand, 39/183 (21%) feet with laterally deviated sesamoid (grade>=4), 39 were in group P (p<0.001). The HV angle at baseline was not associated with the deformity progression (p=0.09). Other measurements, such as rounded metatarsal head, were also not associated with the progression. CONCLUSION: The rapid progression of HV deformity occurred in 1 out of 6 patients. Furthermore, the lateral deviation of the sesamoid on the dorsoplantar radiograph of the foot may be the risk factor of the rapid progression. For patients with mild deformity but deviated sesamoid, early corrective surgery may be justified to prevent the rapid progression of HV deformity.