Relationship Between Plantar Callosity and Foot Deformity in Hallux Valgus Using Weightbearing Computed Tomography

Plantar callosities under lesser metatarsals are often accompanied by the hallux valgus, and the cause of callosity is thought to be associated with the foot deformity, such as the metatarsal length discrepancy, the abnormal metatarsal head height, cavus, flat foot, and rheumatoid conditions. However, it is unclear which variable is most involved in the cause of callosity in hallux valgus deformity. To clarify the factors associated with the callosity with hallux valgus deformity, we conducted multiple image assessments based on weightbearing radiography and computed tomography. A retrospective review was performed based on the collection of clinical records from all patients with hallux valgus treated from 2010 to 2019 in our institution. We measured the hallux valgus angle, intermetatarsal angles, calcaneal pitch angles, talo-first metatarsal angles, metatarsal length, metatarsal head height, first metatarsal pronation angles, and sesamoid position with weightbearing radiography and computed tomography. We analyzed the relation between callosity formation and imaging assessments using univariate and multivariate logistic regression models. Fifty feet were retrospectively evaluated, and multiple logistic analyses by the stepwise method revealed that the first metatarsal-lateral-sesamoid distance was the only radiographical variable associated with callosity formation among all the tested variables (p < .001). As the grade of the callosity became more severe, the lateral shift of the lateral sesamoid increased. The position of the sesamoid bone appears to have a critical role in the assessment and choice of treatment protocols and further research needs to be conducted on the relationship with the position of sesamoid bone to elucidate the mechanism of callus formation.