Congenital paralytic vertical talus. An anatomical study

Abstract

Dissections of the feet of a three-month-old infant with paralytic congenital vertical talus secondary to lumbar myelomeningocele were compared with a dissection of a normal foot. The major differences appeared to be absence of the plantar intrinsic muscles and dorsal dislocation of the talonavicular joint. It is postulated that the pathological process begins as a failure of the intrinsic muscles to oppose the unbalanced, active dorsiflexion forces of the anterior crural muscles. This imbalance then allows disruption of the talonavicular joint, mechanically the least stable joint in the mid-part of the foot. All dorsiflexion forces acting on the ankle then become ineffective and plantar flexion forces serve only to pull the calcaneus and talus into equinus, causing a "vertical" talus. Treatment must be directed at reducing the talonavicular dislocation, correcting the equinus deformity of the hind part of the foot, and substituting for the undeveloped plantar intrinsic muscles.