tarsal tunnel syndromeTarsal Tunnel or Tarsal Tunnel Syndrome is the compression of the main nerve (posterior tibial nerve) that passes under the medial or inside part of the ankle. Peripheral nerves such as the nerves in the feet are richly endowed with their own blood supply and have the ability to stretch or shorten along with the movement of the accompanying joint; in this case the ankle joint. When the nerve is entrapped in its tunnel the swelling that occurs around the nerve and the ensuing scarring of the nerve inhibit blood flow to the nerve. As the ankle joint continues to move the nerve is further compressed and the ability of the nerve to properly function is diminished.
Below is a anatomical diagram of the tarsal tunnel band represented by the white arrow, while the yellow arrow is pointing to the nerve.
Causes of tarsal tunnel syndrome include trauma such as a fall, acute or chronic pronation of the foot that creates excessive pressure on the inside of the ankle. Additionally, a tendonitis of the tendon that passes through the tunnel can create similar symptoms because as the tendon swells it creates excessive pressure within the confined area putting pressure on the nerve. A soft tissue tumor such as a ganglion cyst in the canal will also put excessive pressure on the nerve, again creating similar symptoms. Below is an example of pronation. See how the arch has collapsed. This creates excessive tension on the inside of the ankle thus causing pressure on the nerve.
Diagnosis is made by the history of the pain or numbness in the area of the distribution of the nerves on the bottom of the foot. Tenderness may be noted over the nerve just behind the ankle joint. Your foot specialist should be able to determine the distribution of numbness with simple tests. There may also be muscle weakness particularly in the inability to bend your toes in a downward fashion. Your foot specialist may also order an electromyogram (EMG) which may reveal decreased nerve conduction across the tarsal tunnel. If your doctor feels there may be a soft tissue mass, he may order an MRI. Treatments include the use of orthotics when the origin of the problem appears to be excessive pronation. An orthotic will prevent the foot from over pronating and thus relieve the pressure on the nerve. Click here for a discussion of tarsal tunnel and orthotics. If the origin of the problem is traumatic in nature, a short leg walking cast may be indicated as the cast will prevent the ankle from moving at all and will allow the inflammation in the tarsal tunnel to subside. Along with the above treatments your foot specialist may also prescribe oral anti-inflammatory medicine to help reduce the inflammation. Oral or injectable steroids may also be of benefit. Transcutaneous nerve stimulation may be helpful as a supplemental treatment as long as the underlying cause of the tarsal tunnel is being addressed. If none of the conservative avenues work then you must consider surgical intervention. Aside from the existing symptoms, if the pressure is not removed from the nerve, the nerve will eventually fail all together making it almost impossible to walk. The surgery itself is a soft tissue procedure whereby the ligament band pressing on the nerve is incised; the posterior tibial nerve is freed from all constricting bands. This is an out-patient procedure. You will usually require a walking cast. However, prior to consenting to surgery other causes of these symptoms should be ruled out. These include diabetic neuropathy, a pinched nerve in the lower spine, alcoholism, rheumatoid arthritis and heavy metal neuritis just to name a few.
|
