The growth of the first metatarsal bone.

This study presents a common finding in the first metatarsal bone of a distal epiphyseal cartilage which is considered as a physis. This growth center is omitted in the classic anatomical descriptions of the bone. Analyses of the growth of this physis relates to the metatarsal formula of the adult foot. It may result in a first metatarsal "index-plus," where the first metatarsal is longer than the second, depending upon the duration of the activity of the physis. The presence of this physis may be related, in some cases, to: 1) Hallux rigidus. The conformation of index-plus anatomically predisposes the development of such degeneration. 2) Kohler's metatarsal disease. Disturbance in the arterial vascularity of the epiphyseal-metaphyseal type may, in theory, cause osteonecrosis of the first metatarsal head, although no cases have been reported in the literature. 3) Osteochondritis dissecans. Our finding that disorders of epiphyseal ossification may lead to the development of osteochondritis dissecans.