Синдром тарзального канала: причины, диагностика и лечение.

Tarsal tunnel syndrome (TTS) is a nerve entrapment syndrome causing a painful foot condition in which the tibial nerve is compressed as it travels through the tarsal tunnel. This tunnel is found along the inner leg behind the medial malleolus (bump on the inside of the ankle). The posterior tibial artery, tibial nerve, and tendons of the tibialis posterior, flexor digitorum longus, and flexor hallucis longus muscles travel in a bundle through the tarsal tunnel. Inside the tunnel, the nerve splits into three segments. One nerve (calcaneal) continues to the heel, the other two (medial and lateral plantar nerves) continue on to the bottom of the foot. The tarsal tunnel is delineated by bone on the inside and the flexor retinaculum on the outside. Patients with TTS typically complain of numbness in the foot radiating to the big toe and the first three toes, pain, burning, electrical sensations, and tingling over the base of the foot and the heel. Neurofibromatosis can also cause TTS. This is a disease that results in the formation of pigmented, cutaneous neurofibromas. These masses, in a specific case, were shown to have the ability to invade the tarsal tunnel causing pressure, therefore resulting in TTS. Diabetes makes the peripheral nerve susceptible to nerve compression, as part of the double crush hypothesis. In contrast to carpal tunnel syndrome due to one tunnel at the wrist for the median nerve, there are four tunnels in the medial ankle for tarsal tunnels syndrome. If there is a positive Tinel sign when you tap over the inside of the ankle, such that tingling is felt into the foot, then there is an 80% chance that decompressing the tarsal tunnel will relieve the symptoms of pain and numbness in a diabetic with tarsal tunnel syndrome.

Anything compromising the tunnel of the posterior tibial nerve proves significant in the risk of causing TTS. Neuropathy can occur in the lower limb through many modalities, some of which include obesity and inflammation around the joints. By association, this includes risk factors such as RA, compressed shoes, pregnancy, diabetes and thyroid diseases

Diagnosis is based upon physical examination findings. Patients' pain history and a positive Tinel's sign are the first steps in evaluating the possibility of tarsal tunnel syndrome. X ray can rule out fracture. MRI can assess for space occupying lesions or other causes of nerve compression. Ultrasound can assess for synovitis or ganglia. Nerve conduction studies alone are not, but they may be used to confirm the suspected clinical diagnosis. Common causes include trauma, varicose veins, neuropathy and space occupying anomalies within the tarsal tunnel. Tarsal tunnel syndrome is also known to affect both athletes and individuals that stand a lot. Tarsal tunnel syndrome (TTS) is most closely related to carpal tunnel syndrome (CTS), but is much less common. Studies have found that patients with rheumatoid arthritis (RA) show signs of distal limb neuropathy. The posterior tibial nerve serves victim to peripheral neuropathy and often show signs of TTS amongst RA patients. Therefore, TTS is a common discovery found in the autoimmune disorder of rheumatoid arthritis

The exact cause of tarsal tunnel syndrome (TTS) can vary from patient to patient. However the same result is true for all patients, the compression of the posterior tibial nerve and its branches as it travels around the medial malleolus causes pain and irritation for the patient. There are many possible causes for compression of the tibial nerve therefore there are a variety of prevention strategies. One being immobilization, by placing the foot in a neutral position with a brace, pressure is relieved from the tibial nerve thus reducing patients pain. Eversion, inversion, and plantarflexion all can cause compression of the tibial nerve therefore in the neutral position the tibial nerve is less agitated. Typically this is recommended for the patient to do while sleeping. Another common problem is improper footwear, having shoes deforming the foot due to being too tight can lead to increased pressure on the tibial nerve. The medial calcaneal, medial plantar and lateral plantar nerve areas all had a reduction in pain after successful nonoperative or conservative treatment. There is also the option of localized steroid or cortisone injection that may reduce the inflammation in the area, therefore relieving pain. Or just a simple reduction in the patient's weight to reduce the pressure in the area.

If non invasive treatment measures fail, tarsal tunnel release surgery may be recommended to decompress the area. The incision is made behind the ankle bone and then down towards but not as far as the bottom of foot. The posterior tibial nerve is identified above the ankle. It is separated from the accompanying artery and vein and then followed into the tunnel. The nerves are released. Cysts or other space occupying problems may be corrected at this time. If there is scarring within the nerve or branches, this is relieved by internal neurolysis. Neurolysis is when the outer layer of nerve wrapping is opened and the scar tissue is removed from within nerve. Following surgery, a large bulky cotton wrapping immobilizes the ankle joint without plaster. The dressing may be removed at the one week point and sutures at about three weeks. Complications may include bleeding, infection, and unpredictable healing. The incision may open from swelling. There may be considerable pain and cramping. Regenerating nerve fibers may create shooting pains. Patients may have hot or cold sensations and may feel worse than before surgery. Crutches are usually recommended for the first two weeks, as well as elevation to minimize swelling. The nerve will grow at about one inch per month. One can expect to continue the healing process over the course of about one year. Many patients report good results. Some, however, experience no improvement or a worsening of symptoms. In the Pfeiffer article (Los Angeles, 1996), fewer than 50% of the patients reported improvement, and there was a 13% complication rate. Tarsal tunnel can greatly impact patients' quality of life. Depending on the severity, the ability to walk distances people normally take for granted (such as grocery shopping) may become compromised. Proper pain management and counseling is often required. Results of surgery can be maximized if all four of the medial ankle tunnels are released and you walk with a walker the day after surgery. Success can be improved to 80%.

Though TTS is rare, its cause can be determined in 70% of reported cases. In the workplace TTS is considered a musculoskeletal disorder and accounts for 1.8 million cases a year, which accumulates to about $15–$20 billion a year New studies indicate an occurrence of TTS in sports placing high loads on the ankle joint (3). This can be seen in figure 1. TTS occurs more dominantly in active adults, with a higher pervasiveness among women. Active adults that experience more jumping and landing on the ankle joint are more susceptible (see figure 2). Though athletics and sport are correlations, cases are individualistically assessed because of the oddity.

The athletic population tends to put themselves at greater risk of TTS due to the participation in sports that involve the lower extremities. Strenuous activities involved in athletic activities put extra strain on the ankle and therefore can lead to the compression of the tibial nerve. Activities that especially involve sprinting and jumping have a greater risk of developing TTS. This is due to the ankle being put in eversion, inversion, and plantarflexion at high velocities. Examples of sports that can lead to TTS include basketball, track, soccer, lacrosse, snowboarding, and volleyball. Participation in these sports should be done cautiously due to the high risk of developing TTS. However athletes will tend to continue to participate in these activities therefore proper stretching, especially in lower extremities, prior to participation can assist in the prevention of developing TTS.

According to South Korea's National Intelligence Service, North Korean leader Kim Jong Un had surgery to correct TTS in his right ankle, the source of a pronounced limp. Kim's disappearance from public for six weeks around the suspected surgery created worldwide speculation about the future of Kim and North Korea.

As stated earlier, musculoskeletal disorders can cost up to $15–$20 billion in direct costs or $45–$55 billion in indirect expenses. This is about $135 million a day. Since surgery is the most common form of TTS treatment, high financial burden is placed upon those diagnosed with the rare syndrome.