What is tarsal tunnel syndrome? Symptoms and treatment.

What is tarsal tunnel syndrome?

Tarsal tunnel syndrome is a fairly rare form of neuropathy that results from compression of the tibial nerve in the inner ankle area. Anterior tarsal tunnel syndrome refers to compression of the deep peroneal nerve under the extensors of the posterior surface of the leg. Posterior tarsal tunnel syndrome is the compression of the tibial nerve beneath the flexors at the inner ankle.

Anatomical structure

The tibial nerve, which is an extension of one of the two branches of the sciatic nerve, extends along the posterior surface of the leg along with the posterior tibial vessels. The neurovascular bundle, which extends between the muscles in the proximal part of the leg, passes to the surface in the distal part of the leg. The tibial nerve, after separating from the sciatic nerve in the hamstring, goes deeper beneath the surface of the tibialis and cambal muscles. In the area of the ankle joint it is superficially located and runs along the posterior surface of the inner ankle, together with the posterior tibial artery and vein passing through the tarsal tunnel, which is located between the inner ankle and the Achilles tendon. The inner surface of this canal is formed by the flexor muscle sheath, the outer surface is formed by the heel bone and the posterior surface of the talus, and the anterior surface is formed by the inner ankle. The tarsal canal is divided into two floors: the upper zone, which extends to the beginning of the sheath of the extensor muscles; the lower zone, which begins with the fibrous part of the muscles.

When examining the canal from the front back, we can see structures such as: the tibialis muscle, the long toe flexor muscle and the long toe flexor, the posterior tibial vessels, and the tibial nerve. The tendons of the muscles are located between the fibers that extend between the sheaths of the flexor muscles and the periosteum of the heel bone.

The tibial nerve is usually subdivided into superficial and deep metatarsal branches, and a heel branch within the tarsal tunnel in the medial ankle region. The heel area is innervated 60-90% by the tibial nerve and the other part by the lateral tarsal nerve. The other two branches enter two canals in the lower area below the dorsiflexion muscle. The heel plexus consists entirely of sensory nerves and provides sensory innervation of the ankle joint. The lateral and medial tarsal branches provide motor innervation of the deep muscles and sensory innervation of the heel area.

Etiology (What is the cause of tarsal tunnel syndrome?)

There are many known causes of tibial nerve compression within the tarsal tunnel. The etiologic causes of the syndrome include: 60-80% trauma, abnormalities within the canal, systemic disease, biomechanical and primary causes. With the exception of primary causes, this syndrome is relatively more common in women than in men. Unilateral involvement is most common, but bilateral involvement is seen after biomechanical and systemic diseases.

Trauma

In the etiology of the disease, traumatism has the main advantage. These causes include: fracture of the distal tibial toe and tarsal bones; fracture of the heel bone with displacement; tarsal injuries; spinal trauma/state after surgery; inflammation (tenosynovitis) of the posterior tibialis tendon; the long flexor toe muscle long toe flexor muscle; epineural thickening of the tibial nerve due to bleeding in the tarsal tunnel; Achilles tendon inflammation; sudden strain in people running a marathon; compression syndrome in athletes due to certain exercises and repetitive extensor movements.

Tarsal tunnel syndrome can also occur after surgical procedures performed in this area for other reasons. Causes such as: tight plaster/elastic bandages, tight shoes are not as common.

Anomalies in the canal lumen

Anomalies occupying the canal lumen or located in the canal entrance area include: gangliomas compressing the tibial nerve; dilations of the canal; exostoses; schwannomas; lipomas; osteochondromas; neurofibromas. Congenital hypertrophied and accessory muscles (e.g., thumb detachment muscle) and tendons (e.g., long toe flexor tendon), inner heel-toe line, and hypertrophied flexor muscle sheath can cause tibial compression.

Systemic diseases

The etiology of tarsal tunnel syndrome includes diseases: Cardiovascular (heart and venous insufficiency, thrombophlebitis, varicose veins, embolism, vasospasm, atherosclerosis, hypertension); endocrine (diabetes, hypothyroidism, pituitary adenoma); rheumatic (rheumatoid arthritis, ankylosing spondylitis); metabolic (alcoholic dystrophy, blood clotting disorders, mucopolysaccharidosis, amyloidosis resulting from dialysis).

Biomechanical causes

In the etiology of tarsal tunnel syndrome, foot curvature to the outside and inside, flatfoot deformities, instability of the first row of tarsal bones, and congenital adhesion of the metatarsal bones play a role.

What are the signs of tarsal tunnel syndrome?

The diffuse and nonspecific nature of the complaints of tarsal tunnel syndrome, as well as the varying results of the physical examination, make it impossible to make a correct diagnosis or to make an incorrect diagnosis. Depending on the degree of damage to the tibial nerve branches, pain is characterized by spreading to the lower edge of the toes and decreased sensitivity. If only the metatarsal branch is injured, lower tarsal tunnel syndrome occurs. It may manifest as a feeling of pain, burning, crawling goose bumps, electric shock, or numbness. The pain may spread to the upper regions (valleix fenomeni). This sign occurs when the nerve is compressed at a more proximal level, the so-called double crush. The patient’s complaints increase with standing still and taking a long walk.

The degree of pain decreases during rest and massage. Symptoms that previously occurred at certain intervals occur more frequently over time. Some patients note that they wake up in the middle of the night with unbearable pain, and the degree of pain decreases while walking. Pain occurring at night during rest is related to venous stasis in the dilated veins or to double nerve compression. In severe cases, the pain occurs first in the thumb muscle and then in the short toe flexors. Atrophy and trophic disorders are among the late signs.

The figure shows the signs observed in tarsal tunnel syndrome

Treatment of tarsal tunnel syndrome

Treatment methods for tarsal tunnel syndrome are divided into conservative and surgical. With the exception of acute cases of the disease, surgical treatment should be used if conservative methods are ineffective.

Conservative treatment is planned depending on the underlying cause of the syndrome.

The most effective method of treatment in case of biomechanical cause of tarsal tunnel syndrome is selection of comfortable footwear and use of orthoses that support a neutral position of the leg. And in case of tenosynovitis a local corticosteroid injection should be performed. During conservative treatment, stabilization of the leg, bandages and varicose stockings, ice bandages, special exercises to reduce pressure inside the canal and relax the nerve, and exercise programs to strengthen the muscles are important.

This figure shows the site of numbness and point of compression of the tibial nerve in tarsal tunnel syndrome.

Surgical treatment

Surgical treatment is recommended when a lump or foreign body is detected that is compressing the tibial nerve in the tarsal tunnel cavity. Only after three months of unsuccessful conservative treatment may surgical treatment is considered. Some authors argue that this period may be extended to six months. During the operation, the Lamin technique is most commonly used. During this technique, an oblique incision is made that passes through the posterior surface of the inner ankle to its center. Using this incision, the deep fascia located over the flexor muscles is opened. The goal of this surgery is to release the upper and lower areas of the tarsal tunnel. In the lower zone, you need to loosen the canals over the first toe flexor muscle by about 3 cm, because the lateral and metatarsal branches of the tibial nerve pass through them. It is also necessary to cut the fibrous ligaments, if they exist, while protecting the inner heel area. Lack of attention to the anatomy of this area may cause unsatisfactory decompression and recurrence of complaints.

The figure shows an incision of the flexor muscle sheath, which is located on the tibial nerve

The operation can be performed under general or local anesthesia, as well as under mild anesthesia. The tourniquet, which is used during the operation to reduce bleeding, is not recommended in this case. In idiopathic cases, various surgical techniques have been described with: incision of the flexor muscle sheath only and release of the canal; dissection of the posterior tibial nerve; relaxation of the arteries and veins.

Magnetic resonance imaging is the most valuable diagnostic method for unsatisfactory surgical findings. Literature sources recommend a repeat tarsal tunnel relaxation if the first attempt is unsuccessful. The result of repeated surgery is much better if there is no epineural thickening of the nerve. During the reoperation according to the Campbell method, the application of the surface auricular vein graft indicates the presence of epineural thickening and reduction of reoperations.