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Tarsal Tunnel Syndrome
Tarsal Tunnel Syndrome is due to compression of a nerve called the Posterior Tibial Nerve.The
nerve passes into the foot from around the inside of the ankle just
below the ankle bone. Just beyond this point, the nerve enters the foot
by passing between a muscle and a bone in the foot. This area is called
the Tarsal Tunnel. The Posterior Tibial Nerve is the largest nerve that
enters the foot. At the level of the ankle, the nerve branches out like
the branches of a tree as it goes out toward the toes. This nerve
supplies most of the sensation to the bottom of the foot and the
muscles in the bottom of the foot. When pressure is placed on this nerve, a burning or numbness will be experienced on the bottom of the foot.
The area of the bottom of the foot that is affected can be variable.
Most commonly, it affects the outside portion of the bottom of the
foot. It can also affect the toes, mimicking a neuroma.
The most common cause of Tarsal Tunnel Syndrome is a flat foot or a
foot in which the arch flattens excessively while walking. This is
aggravated by excessive tightness of the clf muscles which restricts
ankle joint motion. Over time, this causes the nerve to stretch or
become compressed in the area of the tarsal tunnel. The condition is
slowly progressive and occurs more commonly after 30 - 40 years of age.
Other causes of Tarsal Tunnel Syndrome are the formation of soft tissue
masses such as ganglions, fibromas, or lipomas
that may occur in the Tarsal Tunnel and cause compression of the nerve.
Also, small varicose veins may form around the nerve that can also
cause compression of the nerve. Flattening of the arch of the foot is due to an abnormal function of a joint complex called the Subtalar Joint.
This joint complex is located just below the ankle joint. When this
joint allows the foot to flatten excessively, the foot becomes over
pronated. Pronation is a normal movement of the foot, but when it
occurs too much of the time, it causes several different problems to
occur in the foot, one of them being Tarsal Tunnel Syndrome. Diagnoses Diagnosis of Tarsal Tunnel Syndrome is made by physical exam and the patient's history of their complaint. A history of gradual and progressive burning on the bottom of the foot should alert the doctor to the possible diagnoses.
Physical exam will often reveal a flat foot or over-pronation of the
foot that is observed when the patient walks. Observation of the area
just below the ankle bone on the inside of the ankle may reveal a
slight swelling. Tapping with the tips of the fingers or a neurological
hammer in this area may reveal a tingling sensation in the bottom of
the foot. Quite oftern there is also associated calf muscle tightness.
X-rays may be of little value, because they will not show the nerve or
reveal any evidence of soft tissue masses. X-rays may be useful in
determining the extent of pronation of the foot but only if the x-ray
is taken with the patient bearing full weight on the foot. An MRI may reveal the existence of a soft tissue mass, but will not demonstrate any damage to the nerve. Nerve conduction studies will reveal if there is damage to the Posterior Tibial Nerve, but will be negative in the early stages of the condition. Other conditions that may cause similar symptoms are diabetic neuropathy, alcoholic neuropathy, or nerve compression at a level higher than the ankle. Poor circulation can also cause burning of the feet. If you experience these symptoms, you should consult your doctor at the earliest possible time. Treatment Treatment of Tarsal Tunnel Syndrome is directed at correcting the abnormal pronation of the foot. This is accomplished with functional foot orthotics,
calf muscle stretching and the use of a dorsal night splint. Orthotics
are custom-made inserts for the shoes that correct abnormal function of
the foot. Treatment with oral anti-inflammatory medications, vitamin B
supplements, or steroids may provide some benefit, but are rarely
curative. Calf muscle stretching
can be useful, because it eases the tension and strain about the ankle
joint. If the Tarsal Tunnel Syndrome is caused by a soft tissue mass,
then surgical removal of the mass may be necessary. Surgical correction
of Tarsal Tunnel Syndrome in the absence of a soft tissue mass has a
very low success rate. This surgery, called nerve decompression, is
intended to release the pressure on the nerve by freeing the soft
tissue structures about the nerve as it passes through the tarsal
tunnel. (See surgical Exploration for Tarsal Tunnel Syndrome) This surgery does not correct the over-pronation of the foot, however, and functional foot orthotics should be worn following the surgery. When
there has been significant damage to the nerve, permanent nerve damage
may be present. In this case, a complete cure is very unlikely, and
treatment is directed at easing the symptoms. Certain medications
available, by prescription from your doctor, may be beneficial for the
burning pain that may be experienced at night. Magnetic insole therapy and Galvanic Nerve Stimulation are alternative forms of treatment that may provide relief. A referral to a pain medicine specialist may also be necessary.
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