Anatomy of a duplicated human foot from a limb with fibular dimelia

At birth, a patient presented with a right tower limb featuring preaxial po lydactyly and fibular dimelia with a complete absence of the tibia. Radiogr aphic studies of the patient's foot revealed a duplicated tarsus with eight metatarsals and toes. The three preaxial toes were surgically removed at 1 year of age. A hallux and four normal-appearing postaxial toes remained. T he foot was amputated when the patient was 3 years old. Dissection of the a mputated foot revealed that the muscles of the dorsum were normal, except t hat the tendon of the extensor hallucis brevis muscle inserted into both th e hallux and toe 2, rather than only into the hallux. The few abnormalities observed among the muscles on the plantar surface of the foot included abs ence of the insertions of the tibialis posterior and the abductor hallucis muscles. in addition, the two heads of the adductor hallucis muscle inserte d abnormally into the medial (tibial) side of metatarsal 1, rather than int o the lateral side. These various muscular anomalies, in addition to the mi rror duplication of the foot with the presence of only a single metatarsal 1, leads us to propose that this metatarsal probably represents two lateral (fibular) halves that form a laterally duplicated bone. Although the dorsa lis pedis artery was present on the dorsal surface of the foot, most of its derivatives were absent. This artery did give rise to a supernumerary medi al branch that ended abruptly in the connective tissue (presumably postsurg ical scar) at the medial border of the foot. This branch may have represent ed a duplicated dorsalis pedis artery associated with the duplicated preaxi al portion of the foot. The arteries on the plantar surface of the foot wer e normal. Even though some anomalies in the pattern of the cutaneous innerv ation were observed, the nerves of the foot were largely normal. The gross and radiographic anatomy of this specimen and the radiographic anatomy of t he leg suggest that some teratogenic event occurred when developmental spec ification reached the level of the future knee. The teratogenic event, whic h probably occurred early in the fifth week of development, may have caused damage that led to a lateral duplication of both the leg and the foot with the absence of some of the mast medial structures. (C) 1999 Wiley Liss, In c.