Lateral ray polydactyly: a case of duplicated metatarsal with normal phalanges.

Lateral ray polydactyly of the foot is morphologically classified on the basis of the external appearance and the anatomic patterns of bony structures. Classification is difficult when the level of duplication is not apparent. We encountered a case of a duplicated metatarsal with no duplication of phalanges. The anomaly was considered to be a case of polydactyly because there were supernumerous metatarsals. On the basis of embryological failure, limb malformations are classified into several categories, and polydactyly belongs to that of duplication. There are, however, some malformations that are difficult to classify clearly. We considered our case to be a result of duplication followed by fusion of the digits.