The tarsal tunnel is a space in the foot formed between bones and overlying fibrous tissue. Within the tarsal tunnel lies a nerve called the posterior tibial nerve, as well as arteries, veins, and tendons. The tarsal tunnel is walled on one side by sturdy bones, and on the other by tough fibrous tissue of the flexor retinaculum ligament. This tunnel has very limited space, and the hard surfaces aren't flexible to allow more.
Tarsal tunnel syndrome results when the posterior tibial nerve is compressed within the tarsal tunnel. This condition is very similar, in the mechanism, to carpal tunnel syndrome in the wrist. Both of these conditions result when a nerve is pinched within a confined space.
When the posterior tibial nerve is compressed in the tarsal tunnel, patients commonly complain of numbness over the bottom of the foot, as well as complaints of pain, burning, and tingling over the base of the foot and heel. Some people complain of shooting pain. The pain may be in one spot, or it may occur over a larger area of the foot, ankle, and calf. Occasionally, tarsal tunnel syndrome is confused with plantar fasciitis or heel spurs.1
The cause of tarsal tunnel syndrome is unknown in most cases but can be the result of fractures, arthritic bone spurs, ganglions, and other benign tumors, muscle impingement, or foot deformities. If you have fallen arches and your heel tilts outward, that can cause strain in the tarsal tunnel area. If you have swelling or inflammation in the ankle from a sprained ankle, diabetes, or arthritis, it may narrow the tunnel. A varicose vein or swollen tendon might also be a cause.1
Because of the symptoms of tarsal tunnel syndrome, most patients describe a similar history of symptoms. However, as mentioned previously, the diagnosis of tarsal tunnel syndrome can be confusing. Tapping on the nerve as it passes through the tarsal tunnel, the so-called "Tinel's Test," may create the symptoms and indicate tarsal tunnel syndrome as the cause of the problem. Electrodiagnostic studies that detect how well a pulse of electricity conducts through a nerve may also help with the diagnosis if there is any reason for confusion.1
Treatment begins with anti-inflammatory medications, and possibly an injection of cortisone into the area around the nerve. Orthotics and changes in footwear may also help to relieve the symptoms.
If none of these measures helps, then a procedure called a tarsal tunnel release may be necessary. This is a surgical procedure performed in the operating room, and it lasts about 30 to 45 minutes. When a tarsal tunnel release is performed, an incision is made to open up the tarsal tunnel and decrease pressure on the posterior tibial nerve. This surgery is also very similar to a carpal tunnel release in the wrist.