Multiplanar Interactions in the Cavovarus Foot

Charcot-Marie-Tooth (CMT) disease is the most common cause of neurogenic cavus foot. This study aimed to identify key morphologic differences between pes cavus in individuals with CMT, idiopathic cavus, and healthy controls.

This single-site, case-control study included individuals 18-65 years old without prior foot and ankle surgery. Participants were grouped based on disease state; all patients with CMT had clinical or genetic confirmation of the diagnosis. Morphologic assessment was completed using HiRise weightbearing computed tomography (WBCT). Statistical analysis involved using generalized linear models for repeated measures and pairwise comparisons between groups or Wilcoxon rank sum tests.

120 total WBCT scans (n = 40 each of CMT, idiopathic cavovarus, controls) from 73 participants were analyzed. Six measurements evaluating medial column height were assessed: Meary angle, calcaneal pitch, cuneiform to floor and skin distances, and navicular to skin and floor distances. Forefoot adduction/midfoot supination was assessed (axial talar-first metatarsal angle and forefoot arch angle). The transverse tarsal arch was assessed using the transverse arch plantar (TAP) angle. All measures of medial longitudinal height were greater in CMT vs controls (P < .05). Forefoot adduction was 3 times greater in CMT cavus compared with controls. The TAP angle differed significantly between CMT (94.2 ± 13.4), idiopathic (100.5 ± 9.4; P = .02), and controls (102.7 ± 7.8; P < .001).

Our results indicate that forefoot adduction/midfoot supination are more pronounced in CMT pes cavus compared with idiopathic and controls, reflecting the severity of muscular imbalances characterizing the progression of CMT. The transverse and medial longitudinal arch are more severely affected in CMT compared with controls. Prior flatfoot studies have identified maximal collapse between the plantar medial cuneiform and the second and third metatarsals; our TAP angle findings demonstrate the opposite in CMT-associated cavus with significant exaggeration of transverse tarsal arch curvature. This exaggerated curvature likely contributes to the intrinsic stiffness characteristic of this foot morphology.