Quantitative morphological evaluation of the first metatarsal head in juvenile hallux valgus

Hallux valgus, a common deformity of the forefoot, is characterized by lateral deviation of the hallux at the metatarsophalangeal joint, often requiring surgery. Juvenile hallux valgus, defined by its development during childhood or adolescence, has a high postoperative recurrence rate. However, its etiology remains unclear. Several studies have found that the radius of curvature of the first metatarsal head is smaller in individuals with adult hallux valgus than in healthy controls, possibly contributing to progression of deformity or recurrence. However, to our knowledge, no detailed morphological analysis focused on juvenile hallux valgus has been published. In the present study, we aimed to characterize juvenile hallux valgus morphology, emphasizing radius of curvature.

The cohort of this retrospective, single-center study comprised patients aged ≤20 years who were allocated to juvenile hallux valgus (53 feet, 32 patients) and typically developing group (56 feet, 56 patients). An adult hallux valgus group (102 feet, 63 patients) was also analyzed. Both juvenile and adult hallux valgus were defined by a hallux valgus angle ≥20°. Radius of curvature was measured on weight-bearing radiographs using ImageJ software and normalized by metatarsal length. Additional parameters investigated included hallux valgus angle, M1-M2A, M1-M5A, distal metatarsal articular angle, sesamoid position, round sign, 1:2 metatarsal ratio, epiphyseal line status, cuneiform obliquity, calcaneal pitch, and Meary's angle.

Radius of curvature was significantly smaller in the juvenile hallux valgus group than in both typically developing and adult hallux valgus groups (p < 0.001). Logistic regression identified radius of curvature (p = 0.02), distal metatarsal articular angle (p = 0.002), and female sex (p = 0.002) as independent predictors of juvenile hallux valgus.

A smaller first metatarsal head radius of curvature may contribute to metatarsophalangeal joint instability and the pathogenesis of juvenile hallux valgus.

Level III, comparative study.