Biomechanical analysis of functional adaptation of metatarsal bones in statically deformed feet.

We analysed the functional adaptation of the first and second metatarsal bones to altered strain in flexible flatfoot. Fifty consecutive women (20-40 years of age) were enrolled: 31 patients with a flexible flatfoot and metatarsalgia (59 feet) and 19 controls with asymptomatic feet (37 feet). They were compared for cortical thickness (medial, lateral, dorsal and plantar) of the two bones. The null hypothesis of no overall difference between the deformed and healthy feet with regard to cortical thicknesses of the two bones was rejected in a multivariate test (p = 0.046). The groups differed significantly only regarding dorsal cortical thickness of the second metatarsal, which was around 18.1% greater in the deformed feet (95% confidence interval: 7.7-28.4%, p < 0.001). Hypertrophy of the dorsal corticalis of the second metatarsal bone appears to be the main metatarsal adaptive reaction to altered strain in the flexible flatfoot.