Tarsal Tunnel Syndrome is a condition of the foot and ankle in which the tibial nerve becomes entrapped along its course. The tibial nerve is a branch of the sciatic nerve, which begins in the distal one-third of the thigh, and courses through the back of the leg underneath the deep muscles. It courses slightly medially through the deep posterior compartment of leg muscles, and enters the foot through the tarsal tunnel. The tarsal tunnel is an organized strip of fascia that has separate canals for the arteries, nerves, veins, and muscles that pass through the area. The tibial nerve divides into three branches; the medial plantar nerve, the lateral plantar nerve, and the medial calcaneal nerve. These divisions are typically found proximal to the tarsal tunnel.
In tarsal tunnel syndrome, there is an entrapment of one or more of the branches of the nerve. The entrapment can be of the tibial nerve before it divides into the three branches, which may lead to more diffuse symptoms through the foot. Tibial nerve entrapment is one of the most common nerve entrapments of the foot and ankle, along with Morton’s Neuroma and an anterior entrapment of the superficial peroneal nerve.
The etiology of tarsal tunnel syndrome is most commonly attributed to repetitive microtrauma of the fascia surrounding the nerve, secondary to a hyper-pronation syndrome. The tissue becomes inflamed, which can entrap the nerve. There may also be varicosities of the posterior tibial veins which also pass through the tarsal tunnel, causing engorgement of the veins through the tunnel, leading to increased pressure on the tibial nerve. Other causes of tarsal tunnel syndrome include direct trauma to the nerve, systemic disease that effects the nerve or the surrounding components, a space-occupying lesion such as a benign tunor of the nerve or nerve sheath, and hypertrophy of the abductor hallucis muscle, which can put additional pressure on the nerve as it enters the foot.
Symptoms of tarsal tunnel syndrome include a burning or tingling sensation in the ball of the foot or the heel, as well as numbness or paresthesia. As the condition progresses, there may be some associated muscle weakness of the intrinsic muscles of the foot. Pain that travels towards the foot or up towards the leg is characteristic of tarsal tunnel syndrome.
Diagnosis is made with clinical symptoms as well as reproducing the symptoms by tapping along the course of the nerve. This may send reproducible pain travelling towards the toes (Tinnel’s sign) or upwards towards the leg (Valleix sign). The pain may also be reproduced by everting the foot in the clinic. Nerve conduction studies may be helpful in the diagnosis and in locating the exact area of impingement, but are not always necessary.
Conservative treatment of tarsal tunnel syndrome includes removing the force that recreates pain. This may involve limiting pronation of the foot through the use of orthotics. These may offer some relief, but will only work when in use. In the case of varicosities being the cause of the problem, some may find relief with the use of compression stockings.
Tarsal tunnel syndrome is more commonly dealt with surgically. A small incision is made in the medial side of the foot, and the nerve is identified. The entrapments of the nerve may be obvious to the surgeon performing the procedure, but in many cases the entrapments are not so apparent. The nerve is freed from any sites that may be entrapped. Most commonly the two sites that are released are the flexor retinaculum and the tarsal canal of the nerves. Additionally, the nerve may become entrapped under the soleus muscle’s retinaculum, the fascia of the abductor hallucis muscle, the intermuscular septum in the foot that the nerve courses under, and the medial band of the plantar fascia. These areas may additionally freed and left open. Post-operatively, a patient undergoing nerve decompression will be non-weight bearing for two-three weeks while the skin and deep tissues heal. During this time they will be able to freely move the foot and ankle when sitting or lying down, but will require an offloading boot when walking.
Tarsal tunnel syndrome can be associated with other conditions of the foot and ankle, and can often mimic other forms of heel pain such as plantar fasciitis. If you feel as though you are experiencing symptoms of tarsal tunnel syndrome, talk to your podiatrist. They will be able to investigate and diagnose the problem.
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