Problems with the feet are often the earliest symptoms of Charcot-Marie-Tooth disorder. Beginning as curled toes and high arches, CMT foot problems usually progress. There are three foot deformities typical of CMT, all of which may be present to some degree. These include the cavus foot, the varus heel and claw toes. They usually begin as flexible deformities and progress to fixed deformities. These foot deformities are caused by growth of bone during a state of muscle imbalance. The progression of the deformities can be seen in Figures 1 - 3.
The cavus foot, also called pes cavus or high arches, results from a muscle imbalance between the extrinsic and intrinsic muscles of the foot. The plantar fascia (soft tissue on the sole of the foot) and the plantar ligaments (tissue connecting the bones of the feet) tighten, somewhat like a rubber band, pulling the ends of the foot closer together. This results in the high arch.
Heel varus, also referred to as hindfoot varus, is a condition in which the heel
turns in. When viewed from behind it appears that the person is walking on the outside edge of the foot. Heel varus creates instability and balance problems.
Claw toes, or hammer toes, is a condition where the toes cock up. Initially claw toes are seen during walking due to muscle imbalance. Later, this condition becomes rigid and the toes stay cocked. Claw toes cause irritation to the top of the toes as they rub against the shoe. This condition also makes it difficult to find shoes that fit properly.
In addition to these three deformities, painful calluses often develop on the bottoms of the feet and the feet become somewhat rigid. Ankles may become weak and unstable and the "forefoot equinus" (foot-drop) may set in. Foot drop results from the wasting of the peroneal muscles ( located on the outside of the leg below the knee) and is the cause of high steppage gait.
Surgery's aim is to enable the CMT patient to walk with the entire lower surface of the foot on the ground (plantigrade), to decrease pain, to
improve balance and agility, and to halt progression of the deformity.
The progressive nature of CMT makes early assessment and long-term treatment planning prudent. A careful evaluation of the foot is the first step. Distinguishing between fixed and flexible components of each deformity is essential to the proper management of CMT and formulation of an individualized treatment plan.
If the assessment concludes that surgery is indicated, things become more complicated. Several types of surgery may be performed on the CMT foot depending on the level of involvement. Tendon transfers, lengthenings and sometimes tenotomy (surgical division of a tendon) may be used to eliminate deforming forces (to slow or stop progression of the deformity) and to balance the foot. Osteotomies (surgical division or sectioning of bones) and arthrodesis (fusing joints) are often necessary to correct alignment and to alleviate symptoms, especially in the case of rigid or fixed deformities.
The three foot deformities and respective surgical options will be discussed separately, but the foot is treated as a whole and surgeries, if necessary, are often done at the same time. Specific surgical procedures will not be discussed in detail in this article.
Where there is no bony deformity, the goal is to release the tightened tissues and ligaments to relax the bottom of the foot and the cock up tendencies of the toes. Surgical procedures include plantar fasciotomy/fasciotomies, also called plantar release.
When bony deformities are present, some form of osteotomy (removal or cutting of bone) may be performed. Essentially these remove a section or wedge of bone, then "close" the foot to reposition the foot to plantigrade (walking with the entire bottom of the foot on the floor.) Surgical procedures may include "closing wedge greenstick dorsal proximal metatarsal osteotomies", "closed wedge dorsal osteotomy", "the Japas-V-tarsal osteotomy", the "Cole osteotomy" and the "tarsometatarsal truncated wedge osteotomy". A variety of muscle transfers in various combinations (such as moving the long peroneal muscle to the short; or moving the posterior tibialis to the dorsum of the foot) may also be done to eliminate the deforming force and improve the position of the foot.
If the heel is flexible, correction of the cavus component should correct the flexible varus heel.
If the varus heel is rigid, an osteotomy may be perfomed on the heel bones. A wedge of bone is removed from the heel bone to correct it to the straight position. Technically (and with more details) this is a Dwyer osteotomy, closing lateral wedge osteotomy of the calcaneus, or hindfoot osteotomy.
If the claw toes are still flexible and have not become rigid, cavus correction should fix the claw toes.
Surgical procedures to fix rigid claw toes include transferring the tendons connected to the toes to the bones of the foot, fusing interphalangeal joints (the ones in the middle of the toes) and fusing bones. Procedures include the Jones procedure, modified Jones transfer and the Girdlestone-Taylor Transfer.
Triple Arthrodesis is a procedure which stabilizes the hind foot by fusing three joints. There are several types of triple arthrodeses; the condition of the foot dictates which might be appropriate. The basic triple arthrodesis involves fusing three joints in the hind foot (the talonavicular joint, the subtalar joint and the calcanocuboid joint). This eliminates side-to-side movement of the foot, but the ankle joint is still free so you retain up and down movement of the foot. In the Pantaylor Triple Arthrodesis, the ankle joint is also fused. The Lambrinudi Triple Arthrodesis "tricks" the ankle into thinking that the foot is completely flexed, or pointing down when it has been surgically moved to a position parallel with the ground/floor. The ankle can still move the foot up but not down.
A triple arthrodesis is not done before the foot stops growing - usually age 12 in girls and age 14 in boys. The goal is to prevent progression of the deformity. There is some controversy over whether or not triple arthrodesis offers better long-term stability than combined midfoot and hind-foot osteotomies.
The progression of the development of the cavus foot needs to be closely monitored. By identifying progressive pes cavus in the early stages before rigid defomities have occurred, muscle-balancing procedures may suffice. Once deformitics have become rigid, surgery becomes even more complex. Most surgeries will require casts for at least six weeks, followed by several months of frequent elevation of the leg and foot to control swelling.
CMT is a progressive disorder. Following foot surgery it is recommended that the patient receive intensive physical therapy under the guidance of a therapist well versed in the CMT foot. This is especially imperative following muscle balancing operations, tissue release, tendon transfers and muscle lenghthening operations.
Conditions are dynamic- ever changing. In situations where a second opinion is required, it is not unusual for the opinions to conflict. Surgery may not solve all problems, and there is always the potential for deterioration of the foot correction with time. However, when indicated, foot surgery can drastically improve the quality of life for the CMT patient.
Bibliography available upon request.
