Tarsal Tunnel Syndrome
ART Literature Review:
by Everett Johnson, DC, ART
Review of anatomy, causes and treatments.
Tarsal tunnel syndrome is a compression neuropathy of the tibial nerve and its branches as it courses through the fibro-osseous tunnel located at the posterior aspect of the medial malleolus of the ankle. The prevalence and incidence of tarsal tunnel syndrome is unknown in the literature, but appears to be high in the female population and in the population of runners. The most common cause of tarsal tunnel syndrome is trauma with heel deformities, varicosities and fibrosis affecting the region as well. Hyperpronation of the foot may be a contributing factor in the development of tarsal tunnel syndrome. Many other conditions may affect the foot and present with similar symptoms, such as plantar fasciitis, hallux valgus, posterior tibial tendonitis, diabetic neuropathy and metatarsalgia.
The tarsal tunnel is considered a fibro-osseous tunnel on the medial ankle that starts just proximal to the medial malleolus and extends into the medial foot. The floor of the tunnel is made up of the medial aspects of the talus and calcaneous. The roof of the tunnel is bound by the fibrous flexor retinaculum. The retinaculum extends from the medial malleolus into the crural fascia, with its distal portion typically being stronger than the proximal portion. Like the carpal tunnel at the wrist, the tarsal tunnel too has many structures passing through it. They include the tibial nerve, posterior tibial artery and vein, and the deep flexors from the posterior compartment of the leg (tibialis posterior. flexor digitorum longus and flexor hallucis longus). At the posterior aspect of the medial malleolus the tibial nerve can be found between the tendons of the flexor digitorum longus and the flexor hallucis longus with the posterior tibial artery.
Typically inside the tarsal tunnel, just behind the medial malleolus, the tibial nerve and posterior tibial artery will give off their terminal branches. The tibial nerve gives rise to the medial and lateral plantar nerves and the medial calcaneal nerve. Medial calcaneal nerve may also arise from the lateral plantar nerve. They lie deep to the fascia of the abductor hallucis muscle as they descend toward the medial foot. These nerves supply sensory and motor innervation to the bottom of the foot and play a role in the distribution of symptoms related to tarsal tunnel syndrome. The posterior tibial artery gives rise to medial and lateral plantar arteries and branches going to the calcaneous.
Branches of the tibial nerve with their pathway and their innervation includes the following:
• Medial plantar: Descends deep to the fascia of the abductor hallucis muscle. Upon reaching the inferior border of abductor hallicus muscle it travels anteriorly between it and the flexor digitorum brevis to provide sensory innervation to the medial plantar aspect of the foot and medial three digits and intrinsic muscles of the foot, the first lumbricals, abductor hallucis, flexor digitorum brevis and flexor hallucis brevis.
• Lateral plantar: Descends deep to the fascia of the abductor hallucis muscle. It travels laterally across the plantar aspect of the foot in the fascial layer between the flexor digitorum brevis and quadratus plantae muscles, anterior to the calcaneal tuberosity. The lateral plantar nerve terminates into superficial and deep branches where the superficial branch supplies sensory innervation to the lateral two digits and the superficial and deep branches supply motor innervation to all muscles not supplied by the medial plantar nerve.
• Calcaneal: Calcaneal branch descends with the sural nerve to supply cutaneous innervation to the heel.
The most typical characteristics of tarsal tunnel syndrome include irritation of the peripheral nerves of the ankle and foot. The patient may complain of parasthesia, shooting or burning sensations in the distribution of the distal branches of the tibial nerve. The pain may radiate into the calf region of the leg. Patients may also complain of pain when the foot is placed in extreme dorsiflexion due to increased tension on the nerve. If only one of the terminal branches is involved or symptomatic it may be referred to as a distal tarsal tunnel syndrome. Tinel sign performed behind the medial malleolus may be positive, and compression of the area for approximately 30 seconds may reproduce the patients symptoms. Other disorders that present with similar presenting signs must be ruled out.
There are many factors that may contribute to the development of tarsal tunnel syndrome. Of the more common causes of the syndrome are soft tissue masses located within the tunnel. These masses include lipomas, swelling of the tendon sheaths, nerve sheath and nerve tumors, accessory muscles and bony protrusions. Valgus deformity of the rear foot may also increase the tension and pressure placed on the tibial nerve in the tunnel and cause symptoms.
The double crush phenomenon may also affect the tibial nerve. The double crush phenomenon says that if there is a lesion of the (tibial) nerve at a more proximal location, axonal flow will be interrupted and the nerve will be more susceptible to a compression or tension trauma at a distal location. This theory is supported by a report that found 75% of patients with a singular nerve lesion also had a second lesion distally. Both lesions were found to be contributing to the patient’s symptoms.
Most literature on the topic advises surgical decompression of the tunnel when conservative measures fail. Some reports indicate operative decompression of the tibial nerve reaches success rates of up to 90%.
There exists long lists of conservative treatment methods on the internet that include rest, manipulation, hot wax baths. The literature shows support for stretching and strengthening the posterior tibial muscles and short flexors of the foot, corticosteroid injections, compression bandaging of the ankle and foot orthotics.
Only one report was found during a literature search for conservative treatment for tarsal tunnel syndrome that included mobilization of the tibial nerve. This study added mobilization of the tibial nerve to another conservative treatment for tarsal tunnel syndrome. 28 patients were divided into 2 groups. They were evaluated for muscle strength, range of motion of the ankle joint, pain in the foot, sensory deprivation of the foot and were observed for clinical manifestations of the syndrome. The control group was subjected to physiotherapy and supportive shoe inserts. The study group was given the same physiotherapy and inserts, with the addition of nerve mobilization exercises. Both groups were followed for 6 weeks and the initial evaluations were repeated. Both groups showed significant improvement in ROM, muscle strength and pain. The study group (nerve mobilization group) however, showed greater results regarding 2-point discrimination, light touch and Tinel sign.
Tarsal tunnel syndrome symptoms are typically felt on the inside of the foot with symptoms radiating to the toes in some cases. Others may have pain on the whole bottom of the foot or radiate up into the posterior aspect of the leg. It may appear suddenly or as a result of an accumulation of injuries or abnormal postures or deformities of the foot. It is important to seek a proper evaluation of leg, heel or foot pain to determine the cause of the problem and to start the proper treatment program for the condition.
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