Hallux Valgus: The Influence of Intersesamoid Crista's Osteoarthritis on Frontal Plane Pronation.

A frontal plane metatarsal rotational (pronation) has been documented in a high percentage of hallux valgus patients. Pathoanatomical concepts leading to pronation are still debated. Nevertheless, there is no consensus on how to measure this component of the deformity. The aim of the present study was to find potential associations between sesamoid's crista osteoarthritis and the frontal plane deformity in HV cases. Our study showed a moderate correlation between the crista's OA and the intermetatarsal angle (IMA), the hallux valgus angle (HVA) and the alpha angle. In severe hallux vulgus deformed specimens, with an eroded intersesamoid crista, frontal plane pronation was not as prevalent nor severe as in those without osteoarthritic degeneration. Severe hallux valgus cases with a completely eroded crista, showed lower pronation, and higher IMA, when compared to specimens with a preserved anatomy. This brings to light the intersesamoid crista's unique function in retaining the IMA. Understanding the role the frontal plane plays in hallux valgus' biomechanics and in its radiographic appearance is vital to change the current paradigm.