Congenital tibial aplasia with preaxial polydactyly. A case report

An anatomical study of a left lower limb with congenital tibial aplasia and preaxial polydactyly amputated at 10 months of age was carried out. The tibia was replaced by a fibrous band (a band of connective tissue) and there were four cuneiforms, six metatarsal bones and seven toes. The second metatarsal bone showed characteristics of the hallux. An intermuscular septum which showed an orifice for the anterior tibial artery was found on the medial side of the leg and foot. All the muscles of the leg and foot were present except for the tibialis posterior muscle, which was replaced by two atypical muscles. No muscular attachments reached the fibrous band. Several intertendinous connection bands were found. Also, an accessory muscular belly split from the tibialis anterior tendon and attached to the common flexor tendinous sheet of the foot. An unusual motor branch of the deep peroneal nerve ran together with this belly to supply the intrinsic muscles of the hallux. We also observed other minor anomalies of the nerve pattern. The arterial pattern was complete, except for some arteries which showed both an anomalous origin and course. The findings of this study suggest that the development of the skeletal elements plays an important role in the differentiation of the muscles, tendons, arteries and nerves. We postulate that a dysmorphogenic event involving the development of the tibial field of the limb could give rise to both defective histodifferentiation of the tibia and defective programmed cell death in the pre-hallucial anlage. These anomalies would determine secondary adaptations of muscles, tendons, vessels and nerves of the limb.