The Problem
The numbness and tingling, burning or cramping you are feeling in your toes or your foot or heel is due to nerve compression, and called tarsal tunnel syndrome. A large nerve, the posterior tibial nerve, crosses behind your ankle, on the inside of your foot. Where the nerve crosses behind the inside of the ankle there is a tunnel with bone on the deep side and a fibrous roof above. Within this tunnel the nerve divides into three branches, one to your heel, the calcaneal nerve, and two to your toes and small muscles of the foot, the plantar nerves. Each of the two plantar nerves, the medial and lateral plantar nerves have separate smaller tunnels just under the foot where compression may also occur. Even the smallest branch, the calcaneal to your heel, goes through a very tight fibrous tunnel and can become compressed.

Pressure on these nerves can come from either swelling within the tunnel, such as occurs after a broken or badly sprained ankle, or from swelling within the nerve, such as occurs in association with medical problems like diabetes. Sometimes there may be arthritis of the ankle joint, a cyst or ganglion associated with the toe tendons or the ankle joint that causes the pressure upon the nerve. There are times when it is just not clear what has caused the problem.

When the nerves in these tunnels receive increased pressure, their blood flow decreases. When this happens, the nerve responds with altered sensations such as tingling and numbness. Sometimes this is so severe that it feels as if the whole foot is asleep. Often the symptoms are worse after standing or walking, when the fluid begins to collect in the foot. The small muscles may give you a cramping feeling as they begin to lose their nerve supply. If just the calcaneal (heel) branch is affected, the symptoms may seem such the same as a heel spur or plantar fasciitis, an inflammation along the bottom of the foot.

Non-Operative Treatment
The goal of treatment is to take pressure off the posterior tibial nerve and its branches. While there is no splint that can be prepared for the foot, as it can for the hand in carpal tunnel syndrome, it may be appropriate to try orthotics, or small inserts for your shoes. The function of these nerves can be followed over time with non-painful quantitative sensory testing performed in the office. There is a great likelihood that either your sport activities or your work activities may need to be altered to give you more time off your feet. You may need to wear support stockings to help keep the swelling controlled in your feet. However, this may also increase the pressure on your nerves. Thus, a trial of this type of treatment must be watched closely.

Any medical condition that you have that is known to affect the nerves must be given the best possible care. This includes disorders such as rheumatoid arthritis, lupus, alcoholism, thyroid gland dysfunction, and diabetes. Both heart and kidney conditions can cause your legs to swell and contribute to tarsal tunnel syndrome symptoms. It will be necessary to be sure that you do not have any back problems, such as lumbar disc disease that may be the cause of your foot symptoms. Often, tarsal tunnel syndrome and these other medical conditions or injuries are both present at the same time.

There is a place for a trial of anti-inflammatory medication if overuse or tendonitis is suspected. However, since no tendons actually pass through the tarsal or plantar tunnels, injecting steroids is not done frequently. Still, in selected cases, and with care not to inject the nerves themselves or the adjacent blood vessels, a cortisone injection may be tried. If the overwhelming sensory symptom is pain in the foot, and you have diabetes, a trial of medication useful for treating “neuropathic pain” is indicated. Such medications include Elavil, Dilantin, Neurontin and Tegretol.

The Operation
When all that can be done, by either medication or changing your activities or by orthotics, proves to be ineffective in relieving your symptoms, the last possible technique to help you is an operation to relieve the pressure upon the posterior tibial nerve and its branches. The operation requires an incision behind, but not too close to, the ankle bone, or medial malleolus. This incision will continue down to, but usually not onto, the bottom or plantar aspect of your foot. Very small sensory nerve branches to the skin close to the ankle bone (from the saphenous nerve), and to the skin of the arch/heel (from the calcaneal nerve) need to be protected during surgery to prevent a painful scar.

The posterior tibial nerve is identified above the ankle, separated from its accompanying artery and vein and followed into the tarsal tunnel. Here the varying patterns for the origin of the calcaneal branches are observed and the calcaneal nerve or nerves are decompressed. The posterior tibial nerve sometimes has split into the plantar nerves before it enters the tarsal tunnel, in which case the nerves occupy more space than usual in the tunnel and make it more likely for the tarsal tunnel syndrome to occur. The branching pattern of the plantar nerves is observed and followed into the bottom of the foot, releasing the medial and lateral plantar tunnels just past the tarsal tunnel.

Any cysts or arthritic problems with the ankle joint may be corrected at this time. If there is scarring within the posterior tibial nerve or its branches, this is relieved by the technique of internal neurolysis. During internal neurolysis, the outer layer of the nerve wrapping is opened and the scar tissue is removed from within the nerve. In those patients with symptoms of neuropathy due to multiple sites of nerve compression along multiple peripheral nerves, such as can occur with diabetes, other nerves in the foot may be decompressed at the same time as the posterior tibial nerve and its branches.

The dressing is a large, bulky cotton wrapping that is designed to immobilize the ankle joints usually without the use of plaster. This bulky dressing is removed about 5 days after surgery so the foot can be washed and gentle ankle movements begun. Sutures remain for about three weeks.

Complications
The risks and complications from the operation include a permanent scar. The scar may become painful. Bleeding may occur as well as infection. Wound healing may be unpredictable in the foot and ankle area, especially if you have medical problems such as steroids that slow down the healing process. Even if your stitches have been left in for three weeks, your incision may open up as you begin walking or if your foot swells. This open wound may heal but may take two to eight weeks, during which time you will need dressing changes to prevent infection and dressing changes to promote healing. Rarely the wound will not close and a skin graft may be required.

Post-operative Management
For the first three weeks after surgery you will be using a walker or crutches. The majority of the time you will be seated or lying with your foot elevated to minimize swelling. If you need to stand and bear weight on your foot, you may. It is excessive ankle movement that will cause the sutures to tear through the skin, causing the wound to open and increase the risk of infection. At one week after surgery the large bulky dressing is removed and replaced with a smaller sterile dressing. Usually at about three weeks the sutures are removed. You will begin weight bearing by standing in one place for increasing lengths of time. Attempt to walk by lifting your leg at the hip rather than by bending your ankle. You can wear slippers or large sneakers. At about three to six weeks if the healing is going smoothly but the scar is either thickening or becoming painful, you may begin to massage a steroid cream into your scar.

If you have persistent swelling in your foot, you may be asked to wear support stockings or panty hose. If your foot remains swollen, it will be necessary to resume your activities more slowly.

Recovery Phase
The recovery process occurs generally in two stages. The operation causes release of pressure on the nerve and blood flow improves in the nerve. Therefore, by the time the sutures are removed you may already have had relief of your symptoms. The parts of your symptoms that were due to scarring inside the nerve, such as persistent numbness in the toes or muscle wasting will recover much more slowly. The nerve fibers must regenerate or grow into the muscle and into the tips of the toes. The nerves grow at about one inch per month. This process may be associated with some pain, as described under complications. You will continue to improve for at least one year.

• This information should be reviewed and any information not understood brought up and discussed with Dr. Ferragamo. It is hoped that this information may make you better aware of the operation, its potential benefits, risks and complications, and help you in the recovery period following surgery.

Copyright © 2007 Tracy Ferragamo, D.P.M., DavisPodiatryCenter.com