The High Arch (Cavus) Foot (Charcot Marie Tooth Disorder)

There are many causes for a high arch foot. In the United States, the most common cause for a high arch foot is a form of muscular dystrophy called hereditary sensorimotor neuropathy. Most people recognize this by the more commonly used name of Charcot Marie Tooth disease (CMT). This is a disease of the muscles and the nerves of the legs and occasionally of the hands, in which certain muscles weaken, while others retain their strength. The condition is transmitted as an autosomal dominant condition. This means that 50% of the offspring will statistically inherit the disorder. This is, however, just a statistic. In some families, all the children develop the condition while in others, none inherit it.

The muscle imbalance around the foot and ankle gives rise to a typical pattern of deformity in addition to the high arch (known as cavus). The bone under the big toe (called the first metatarsal) can become very prominent and the toes can curl or clench like a fist (called claw toes). Excessive amount of weight may be placed on the ball and heel of the foot, which can lead to the ankle weakening and giving way (this is referred to as ankle instability) and soreness. Calluses and sometimes stress fractures may occur where the foot is exposed to extra friction or pressure, such as on the outer (or lateral) border of the foot.

The deformity of the high arch foot develops because the muscles that pull the foot inward (inversion) remain strong, while those that pull the foot outward (eversion) are weak or absent. The muscle that remains very strong is called the posterior tibial muscle, and the muscle that gets weak is the peroneus brevis muscle. Another common problem in CMT is the presence of a foot drop. This means that the muscle that pulls the foot (the anterior tibial muscle) upward is weak or paralyzed, leading to an abnormal dropping of the foot when walking.

The diagnosis of cavus foot deformity or CMT can be made by an orthopedic surgeon in the office. Evaluation includes a thorough history and physical examination as well as imaging studies such as X-rays. The orthopedic surgeon will look at the overall shape, flexibility, and strength of a patient’s foot and ankle to help determine the best treatment. Nerve tests may occasionally need to be performed to help confirm the diagnosis.

Treatment for this condition depends on the extent of deformity and the amount of disability experienced by the patient. The condition occurs in both children and adults. Once the deformity is present in a child it is going to be progressive. This means that the deformity will slowly get worse as a result of the muscle imbalance and weakness. Although the pattern of muscle and nerve damage may be similar through the generations in a family, this is not always the case. Every cavus foot is unique. Depending upon the symptoms, treatment may include changing the shoes, special orthotic supports (devices that support, adjust, or accommodate the foot deformity), cushioning pads, foot and ankle braces, or surgery.

Surgery may be necessary in situations where the symptoms are likely to get worse over time, or when pain and instability cannot be corrected with external orthopedic devices. The main goals of surgery are:

1. Correcting all the existing deformity of the toes, the high arch, the ankle and the muscle imbalance
2. Preserving as much motion as possible
3. Rebalancing the deforming muscle forces around the foot and ankle
4. Adding stability to the ankle
5. Preventing ankle arthritis from occurring as a result of the chronic deformity of the foot and the instability of the ankle

These are the appearance of the feet from behind in two patients with a high arch, with the heel twisted inwards. The foot on the left in both patients has already undergone surgical correction and is straight.

There are really many types of surgical procedures that can be performed to correct the foot and the ankle and restore function and muscle balance. The decision as to which surgery is done depends upon the underlying deformity and the pattern of muscle loss and weakness. There is always a combination of many procedures that is done all at the same time to correct the various deformities. Occasionally, the surgery has to be staged in two sessions so that the hindfoot and ankle are first corrected followed by the toes. The surgeries can be tendon transfers to correct muscle weakness, bone cuts (called osteotomies) to correct bone deformity, and soft tissue releases to reposition the arch of the foot. As a rule, we try to avoid performing a fusion (called an arthrodesis) of the foot if at all possible. I study each patient individually and develop a specific plan based on the parts of the foot and ankle that are involved.

The foot can be divided into four main areas: the forefoot (including the toes), the midfoot (including the arch), the hindfoot (including the heel) and the ankle. Any and all of these areas can be affected by cavus deformity or CMT. Generally, a combination of a calcaneal (hindfoot) osteotomy, a first metatarsal (forefoot) osteotomy, and a plantar fascia (the thick connective tissue on the bottom of the foot that helps support the arch) release is performed. Occasionally, additional bone cuts (including midfoot osteotomies) and soft tissue procedures (including ankle ligament reconstruction and tendon transfers) are necessary to complete the correction.

In some severe deformities or in cases that involve significant arthritis, we may need to fuse certain joints using plates, screws, or pins to help decrease pain and correct the deformity. Unfortunately, this means that some motion in the foot and ankle will be lost permanently. Yet this does not necessarily compromise the patient’s ultimate function. Examples of joint fusion (called arthrodesis) procedures include ankle arthrodesis (which limits up and down motion of the foot) and triple arthrodesis (meaning that three separate joints of the hindfoot are fused together, limiting side to side motion).

The correction of cavus feet and CMT can be challenging. However, with appropriate care and management, the foot can usually be well corrected and balanced, with as much motion as possible maintained.

X-rays of a patient with CMT. The hindfoot and forefoot were very stiff (rigid), and pain was present along the outer (lateral) part of the foot. This was corrected with a triple arthrodesis, a midfoot fusion, fusion procedures of the toes, and a tendon transfer. You can see that the arch has been nicely flattened.

This patient had a very high arch with a loose and unstable ankle, and the ankle was giving way repeatedly. This patient was a 37 year old with CMT. The goal here was to correct the deformity and balance the foot with tendon transfers. You can see the before and after of the XR as well as the foot looking from the back. You can see that the right foot has been nicely corrected with a calcaneal (hindfoot) osteotomy, a first metatarsal (forefoot) osteotomy, a plantar fascia release, multiple tendon transfers, and an ankle ligament reconstruction.

This patient was a 53 year old who had suffered mild polio as a child and who had a high arch. She had a mild cavus deformity which you can see on the XR on the left and the photo at the bottom of the left foot. The right foot was corrected very simply with a tendon transfer, a plantar fascia release, and a calcaneal (hindfoot) osteotomy. You can see by looking at the feet what the difference is between the right foot which had been corrected and the left foot which still required correction.

This was a younger patient with severe cavus deformity involving the hindfoot, midfoot, and forefoot. If you look carefully, you will see how badly the toes are deformed (we call this cock up toe deformity). One cannot correct deformity of this type using bone cuts only. The principle of correcting deformity is to balance the foot. Remember that there is always severe muscle imbalance in the foot like this, so that the powerful muscle on the inside of the leg (the posterior tibial muscle) which pulls the foot inwards, must be moved or transferred. A tendon transfer was performed in addition to multiple bone cuts or osteotomies which were fixed with screws. The toes have not yet been corrected in the XR on the right but you can see how nicely the arch has flattened.

This patient has obvious very severe deformity of the feet. The left foot was first operated on with the same type of surgeries that have been described above. This patient with CMT had a foot drop (the muscle of the front of the leg was paralyzed and the foot slaps when walking). You can see very nice correction of the left foot following tendon transfers, and a fusion of the joints of the back of the hindfoot. This patient eventually became completely brace free and was able to return to daily exercise and lock walks without any support.

This was a 20 year old patient with CMT and a very stiff and rigid hindfoot and forefoot deformity and was treated with a triple arthrodesis, tendon transfer, first metatarsal osteotomy, and toe fusion.

There are many different causes of a high arch foot, some of which are quite rare. Here in this adolescent female the deformity of the foot developed as a result of a lack of circulation to the foot following injury called a compartment syndrome. You can note the severe contracture of the foot and the toes. This is a very difficult problem to treat, and requires multiple tendon transfers, removal of severe scarring in the foot and leg as well as fusion of the joints of the back of the hindfoot.

This patient had been operated on previously in another institution to try and correct the high arch associated with CMT. Staples were used to correct the foot with a fusion. One of the principles of correction of this deformity is that you cannot expect the foot to stay corrected with a fusion unless the muscle balance is simultaneously corrected. It is not surprising then that the deformity recurred in this patient. You will also note the crack on the small bone under the sode of the foot (called the 5th metatarsal). This is a stress fracture which results from chronically walking on the outside of the foot. You  can see the before and after photo and XR of the foot, which was correctly balanced by revising the triple arthrodesis, adding a tendon transfer, tightening the ankle ligaments, and using a screw to fix the fifth metatarsal fracture..