Charcot Marie Tooth disease (CMT) is a hereditary motor and sensory neuropathy affecting the upper and lower extremities. Currently there are over 50 known types covered under the CMT umbrella. The varying degree to which one is affected is can be widespread by the type of CMT. Typically there are associated foot abnormalities that affect the shape and function of the foot. These abnormalities can range from a severely flat foot to a severely high arch foot with a high arch being much more common.
This common pathology shown in CMT is caused from varying degrees of distal muscle weakness leading to a cavus foot deformity. The cavus foot deformity is caused from muscle imbalances across joint lines in the forefoot, midfoot, and hindfoot. Simply stated, the characteristic foot has a high arch, claw toes, and lateral (inversion) instability in the heel.
The driving forces of the hindfoot instability begin with forefoot equines associated with a plantar flexed first ray and a resultant contracture of the plantar fascia. The forefoot valgus drives the hindfoot into a calcaneal varus position. In addition, the forefoot is adducted at the mid-tarsal joint and the whole extremity becomes externally rotated at the hip.
Many of the feet in CMT require encouragement from varying degrees of orthotic management. The goals of orthotic management include supporting and aligning skeletal structures; preventing or influencing joint motion; supporting and enhancing muscular imbalances; and improving overall balance. Of course, all of this orthotic management is predicated with a good foundation from footwear.
By: David Misener, BSc, CPO, MBA
Clinical Prosthetics & Orthotics, LLC
Also see CMT - Foot Condition.