Congenital metatarsus adductus in early human fetal development: a histologic study.

Two feet with congenital metatarsus adductus from fetuses at early development (16 and 19 weeks of gestation) were studied by making serial histologic sections in the horizontal plane of the foot. It was observed that the shape of the medial cuneiform was altered and the first cuneometatarsal joint tilted toward the medial and dorsal directions. The first metatarsal appeared normal, whereas the other metatarsals were deformed in slight adduction at the metaphyseal level. Subluxation at the other cuneometatarsal joints and naviculocuneiform joint was not observed, and the navicular showed no signs of medial or lateral displacement in relation to the head of the talus. No histologic abnormalities of the joint capsules, ligaments, or tendons were observed. On the basis of these pathologic findings, the possibility of a developmental abnormality of the medial cuneiform as a pathogenic factor for the congenital metatarsus adductus deformity should be considered.