Pes cavus (cavus foot deformity) is an equinus deformity of the forefoot relative to the hindfoot, producing a high medial longitudinal arch (Figure 183-10). It is referred to as clawfoot when associated with flexion deformities of the toes.

Figure 183-10 Pes cavus, viewed from the outer side. The height of the medial and lateral longitudinal arch is abnormal. (Sharrard WJW. Paediatric Orthopaedics and Fractures. 2nd ed. Oxford, NY: Blackwell Scientific; 1979. Reprinted by permission of Blackwell Publishing Ltd.)

Pes cavus is seen in muscular dystrophy, peripheral neuropathies, and disease of the spinal cord, brainstem, and cerebral cortex. Cerebral palsy, meningomyelocele, poliomyelitis, Charcot-Marie-Tooth disease, and Friedreich ataxia are examples of conditions of neurologic origin that produce pes cavus as a late manifestation. Because of the variety of conditions in which pes cavus is seen and its variability as a manifestation of some of these, incidence in the general population is not known. A family history of pes cavus should be sought because many of the conditions producing this deformity are inherited.[8]

The primary pathological condition is neuromuscular rather than bony, with weakness or paralysis of the intrinsic muscles of the foot and its dorsiflexors, leading to the deformity over time. Pes cavus is therefore not seen at birth and usually does not develop clinically until late childhood or adulthood, depending on the underlying neuromuscular disease. A high-arched foot characterizes the deformity. Pes cavus takes one of two forms: (1) cavovarus, in which the calcaneus is inverted with tightness of the heel cord; and (2) calcaneocavus, in which a high arch with normal heel alignment is present, usually from weakness of the calf muscles resulting in increased ankle dorsiflexion and increased plantar flexion of the forefoot.

Radiographic examination may be necessary, especially if surgical management is under consideration.

Early treatment includes exercises designed to strengthen the affected muscles and application of metatarsal pads to the innersoles of the shoes or metatarsal bars to the outer soles. Surgical correction of the fixed deformities, including plantar fasciotomy, tendon transplants, osteotomies, and arthrodeses, may be required later.