[Congenital absence of the anterior compartment muscle of both legs--a case report].

A case of the congenital defect of the anterior compartment of the legs is reported, and is the first one in the literature. This case presented bilateral talipes equinovarus deformity at birth on a sister of identical twins. The abnormalities of the leg muscles were found from lack of active dorsiflexion of the ankle and the toes after initial walking. In the surgical finding, the deep peroneal nerve was normal, but the anterior compartment muscles of the leg were completely replaced by the fatty tissue. Microscopically, the normal muscle fibers were scattered in the fatty tissue with the small vessels and the nerve fibers. The etiology of the congenital muscle defect has been in controversy, but as yet there have been few case reports of lower leg muscle defect. In the treatment of congenital club foot, one should consider the congenital defect of the anterior compartment muscles.