Tarsal Tunnel Syndrome | Diagnosis & Treatment for Physios

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Tarsal Tunnel Syndrome | Diagnosis & Treatment

Introduction & Pathophysiology

Tarsal tunnel syndrome is also known as tibial nerve dysfunction and posterior tibial nerve neuralgia. It is an entrapment neuropathy caused by the compression of tissues within the tarsal tunnel. The tarsal tunnel is a thin fibro-osseous cavity behind and beneath the medial malleolus. It is formed by the medial malleolus anterosuperiorly, by the posterior talus and calcaneus laterally, and is held against the bone by the flexor retinaculum. Post-traumatic, biomechanical, inflammatory, and morphological disorders are the most common intrinsic and extrinsic aetiologies of tarsal tunnel syndrome.

Pathomechanism

An entrapment or impingement issue of the posterior tibial nerve or the continuation into the medial and lateral plantar nerve is thought to be causing the symptoms. The entrapment is characterized by increased pressure at the boundaries of the tarsal tunnel. Anything that reduces the space within this passage can cause the pressure to increase. Symptoms may thus also emerge as a result of the development of space-occupying lesions within the tarsal tunnel.

The tarsal tunnel forms a passage for the posterior tibialis tendon, the flexor digitorum longus (FDL) tendon, and the flexor hallucis longus (FHL) tendon. Accompanying these tendons, the posterior tibial artery and vein, and the posterior tibial nerve (L4-S3), also pass through it. The posterior tibial nerve bifurcates into the medial and lateral plantar nerve. In some people, this intersection occurs before the passage through the tarsal tunnel, in some the posterior tibial nerve splits in the tarsal tunnel. The medial calcaneal branch comes from the posterior tibial nerve just proximal from the flexor retinaculum.

Multiple causative factors have been described, which can be divided into intrinsic and extrinsic mechanisms. Among the intrinsic causes is the presence of anatomical muscle variants. One of the extrinsic causes is external pressure which restricts blood flow in the arteries that supply the tibial nerve, resulting in local ischemia. Ankle trauma or inflammation is also described.

Epidemiology

Yammine et al., (2022) found that the prevalence of tarsal tunnel syndrome was 9% in people with anatomical muscle variants or accessory muscles. Tarsal tunnel syndrome is more frequently reported in women and occurs more in adults. The exact incidence is unknown. Tarsal tunnel syndrome is more common among athletes and persons who are prone to lengthy weight-bearing periods inclusive of standing, walking, or strenuous physical activity.

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Clinical Presentation & Examination

The typical symptoms are dysesthesia, paresthesia, and sometimes hyperesthesia along the course of the posterior tibial nerve in the tarsal tunnel or at the borders of the tarsal tunnel. However, the symptoms can be vague and difficult to localize. The symptoms often progress throughout the day and may also lead to cramping of the medial plantar fascia. In some cases, pain may also extend proximally to the mid-calf region with the percussion of the nerve at the site of entrapment, a finding known as Valleix phenomenon. Sometimes, night pain may be present.

Depending on the location of the bifurcation of the posterior tibial nerve, the location of the symptoms can be limited to the medial ankle region or can extend more posterior to the calcaneus or more distally to the plantar aspects of the foot.

Examination

There is no definite diagnostic standard but a thorough history and clinical examination may increase the suspicion for the presence of tarsal tunnel syndrome. During the inspection and the active examination, you may see a flatfoot deformity or a pronated foot. Atrophy, weakening of the intrinsic foot muscles, and toe contractures may be observed in chronic situations. Abnormalities in gait should be evaluated, such as excessive pronation or supination, toe eversion, excessive foot inversion or eversion, and antalgic gait.

The following clinical tests can be conducted to determine the possibility of the presence of tarsal tunnel syndrome.

A positive Tinel sign and objective sensory loss along the distribution of the tibial nerve can give a clue for the presence of tarsal tunnel syndrome.

The Dorsiflexion-Eversion test for an increase in tenderness has good diagnostic accuracy. This test could be of value when your patient indicates the presence of pain or paresthesia when they are in the toe-off phase of the gait cycle.

The Triple Compression Stress test was reported with high specificity. The foot position is thought to put the posterior tibial nerve under stress.

As with any neuropathy, quantitative sensory testing can be performed. The primary goal of qualitative sensory testing is to determine pain mechanisms by assessing the functionality of large and tiny sensory nerve fibers. By using heat, vibratory, and painful stimuli you could objectify sensory disturbances.

Differential Diagnosis

Diabetic (poly)neuropathy
Mass-occupying lesions within the tarsal tunnel
L3-S1 nerve root syndrome
Proximal tibial nerve injury/entrapment
Radiculopathy
Posterior Tibialis Tendon Dysfunction
Plantar Fasciitis and bursitis
Calcaneal stress fracture
Compartment syndrome of the deep flexor compartment
Tenosynovitis of the FHL and FDL

Treatment

Conservative therapy and outcome differ depending on the cause of tarsal tunnel syndrome. The objective is to reduce pain, inflammation, and tissue stress. It is possible to use ice and analgesics and nonsteroidal anti-inflammatory medications (NSAIDs) can be useful. Activity modification is also useful in symptom management.

Calf stretching and nerve gliding can aid in alleviating symptoms. Tibialis posterior strengthening and a medial heel wedge or heel seat may lessen traction on the nerve by inverting the heel. Targeting the intrinsic foot muscles to improve navicular drop and strengthen the longitudinal foot arch is necessary and an appropriate shoe supporting the arch provides passive support. Kinesiology tape can be used to support the arch and reduce biomechanical stress.

In case a ganglion cyst is causing compression of the posterior tibial nerve, it can be aspirated under ultrasound guidance. Injections of corticosteroids into the tarsal tunnel may help when edema is the causative factor. If conservative treatment fails to relieve the patient’s symptoms or a specific cause of entrapment is found, surgery is recommended. Slow EMG posterior tibial nerve conduction is a sign that conservative treatment will not be successful. Patients suffering from symptoms caused by a space-occupying lesion usually react successfully to surgical treatment. Then the flexor retinaculum is released from its proximal attachment near the medial malleolus down to the sustentaculum tali.

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