Computed tomographic analysis of pes cavus.

Patterns of muscle degeneration in patients with peripheral neuropathies exhibiting pes cavus deformity were studied by computed tomography (CT). Twenty-six patients attending the muscle disease clinic at Newington Children's Hospital with hereditary sensory motor neuropathies (HSMN) I, II, or III had clinical and radiographic assessment in addition to CT scans of the feet and legs at designated levels. The pattern of muscle degeneration was analyzed with other variables, including age, sex, tibial torsion, cavus, heel varus, and claw toes. Multiple regression/correlation analysis clearly demonstrated earlier and more severe involvement of the intrinsic muscles of the foot as compared with the extrinsic muscles. The most consistent early degeneration occurred in the pedal lumbricals and interossei, which have the most distal innervation. The order of muscle degeneration is a centripetal pattern, with two types of degeneration occurring in the leg muscles: type P patients had earlier degeneration of the leg muscles innervated by the peroneal nerve, and type T patients showed earlier degeneration of those extrinsics innervated by the posterior tibial nerve.