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Tarsal Tunnel Syndrome: Carpal
Tunnel Syndrome of the Foot?
by Nathan Wei
Tarsal tunnel syndrome is condition where the posterior tibial
nerve in the ankle is compressed. In many ways, this condition
is analogous to carpal tunnel syndrome in the hand where the
median nerve is compressed.
With tarsal tunnel syndrome, compression
of the tibial nerve occurs within a tunnel created by a floor
consisting of the calcaneus (heel bone) and bounded by the medial
malleolus- the bump on the inside part of the ankle- and the
far corner of the heel bone. The roof of the tarsal tunnel is
formed by a retinaculum- a tough piece of fibrous tissue.
Within the tarsal tunnel run a number of tendons (posterior tibial
tendon flexor digitorum tendon, and flexor hallucis tendon) as
well as the posterior tibial nerve, and the posterior tibial
artery.
Many people with tarsal tunnel syndrome may have compression
of nerves elsewhere. An example would be a patient who has a
pinched nerve in the low back along with tarsal tunnel syndrome.
This condition, where there is compression at least two locations,
is termed “double-crush” syndrome.
Another problem is that many people who have tarsal tunnel syndrome
may have peripheral neuropathy. This is a condition where there
is damage to the small nerves in the feet. Numbness and tingling
are common symptoms. Among the diseases associated with peripheral
neuropathy are diabetes and hypothyroidism. |
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Medications can also cause a
peripheral neuropathy. These include colchicine given for gout,
nitrous oxide (an anesthetic), metronidazole (Flagyl- an antibiotic),
phenytoin (Dilantin- an anti-seizure medicine), lithium (given
for manic depression), disulfiram (Antabuse- given for alcohol
addiction), cimetidine (Tagamet- given for peptic ulcer disease),
hydroxychloroquine (Plaquenil- given for autoimmune disorders),
amitriptyline (Elavil- an antidepressant), and various chemotherapy
agents given for cancer.
Excessive alcohol and tobacco use as well as nutritional deficiencies
can cause peripheral neuropathy as can exposure to heavy metals.
Infectious diseases such as Lyme disease, leprosy, and HIV infection
can also lead to peripheral neuropathy.
The most common symptom of tarsal tunnel syndrome is foot pain,
which can also be accompanied by numbness and tingling.
Tapping on the tibial nerve at the tarsal tunnel may cause pain
and tingling to occur. This is called a positive Tinel’s
sign and is clinical evidence of tarsal tunnel syndrome.
The clinical impression can be confirmed with electrical testing
(electromyography and nerve conduction). Electrical testing is
important to evaluate the patient for other nerve entrapment
problems such as a pinched nerve in the back. Peripheral neuropathy
can also be diagnosed.
The posterior tibial nerve divides into three branches that include
the calcaneal, medial plantar, and lateral plantar nerve branches,
all of which innervate different parts of the foot and ankle.
Magnetic resonance imaging (MRI) and ultrasonography may be useful
in evaluating a patient for underlying reasons for tarsal tunnel
syndrome.
Medical therapy for tarsal tunnel syndrome may start with local
injection of steroids into the tarsal tunnel. Physical therapy
may be of some value in reducing soft-tissue edema which can
ease pressure on the compartment.
Splints and braces may be helpful for patients who have anatomic
abnormalities in the hindfoot and ankle.
When conservative therapy fails to help the patient's symptoms,
surgical intervention may be warranted.
More recently, the use of a percutaneous ultrasound guided needle
release technique has been found to be effective. With this procedure,
which is done using local anesthetic, the retinaculum is pierced
several times with a small needle while injecting small amounts
of fluid at the same time. In essence, the retinaculum is shredded
to relieve pressure in the tarsal tunnel. Recovery time is limited
to about one day compared with the weeks to months that can accompany
open surgery.
When a patient doesn’t improve and has persistent pain,
associated plantar fasciitis may be a cause of persistent pain
in the medial heel region after surgery or percutaneous needle
release.
Complete relief of symptoms may not be possible because tarsal
tunnel syndrome has many causes and because the likelihood of
irreversible nerve damage exists. An increase in pain after decompression
either by needle release or by open surgery is extremely rare. |
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