Congenital absence of the lateral metatarso-phalangeal sesamoid bone of the human hallux: a case report.

A case of congenital absence of the lateral metatarsophalangeal sesamoid bone of the hallux is reported, in a 47-year-old woman. The lateral sesamoid bone was absent on the right hallux, and extremely reduced on the left hallux. The normal intersesamoidean crest and both sesamoidean grooves of the metatarsal head were absent. Physical examination was normal, and no functional disturbance resulted from this variant. Only two previous cases have been found in the literature. It must be distinguished from a total resorption due to an infectious process, or from an absence due to surgical excision. This absence can be related to the general tendency of disappearance of the sesamoid bones within hominoid primates.