What is the tarsal tunnel
The tarsal canal is located behind and below the medial malleolus. Its bottom is formed by bones, and its roof is formed by a dense ligament. Inside there are muscle tendons, an artery, veins and the tibial nerve, which divides here into branches to the sole and heel. The space in the canal is limited, so any increase in the volume of contents - edema, dilated veins, cyst, growth after a fracture - leads to compression of the nerve. Additionally, the nerve is stretched when the foot falls inward with flat feet, as well as during prolonged standing.
- Narrow tunnel behind the inner malleolus
- Contains tendons, blood vessels and tibial nerve
- Compression is possible with edema and space-occupying formations
- Flat feet increase tension on the nerve
- The branches go to the sole and heel - hence the localization of complaints
Causes and risk factors
In about half of the patients, it is possible to find a specific cause: a fracture or dislocation in the ankle in the past, a ganglion cyst, varicose veins inside the canal, an accessory muscle, inflammation of the tendon sheaths. For others, compression is associated with the structural features of the foot and the load. Common diseases - diabetes, rheumatoid arthritis, hypothyroidism, obesity - make the nerve more vulnerable and increase tissue swelling, so they must be taken into account during the examination.
- Flat feet and hallux valgus
- Consequences of ankle fractures and dislocations
- Ganglion cysts and space-occupying formations in the canal
- Varicose veins
- Tenosynovitis and rheumatoid arthritis
- Diabetes mellitus and hypothyroidism
- Prolonged standing and excess weight
Symptoms
Typical burning, tingling and numbness of the sole and toes, sometimes only part of the foot if a separate branch is compressed. The pain is often described as electric shocks that radiate to the fingers or, conversely, up the shin. It typically gets worse in the evening, after prolonged walking or standing, as well as at night - because of this, sleep is disturbed, and people get up to walk or massage the foot. With a long course, weakness of the small muscles of the foot, changes in the shape of the toes and dry skin of the sole occur.
- Burning and tingling in the sole
- Numbness of the toes and arch of the foot
- Night pain and discomfort
- Increased after walking and standing
- Shooting when tapping behind the inner ankle
- Weakness of the small muscles of the foot over a long period of time
How to make a diagnosis
The doctor checks the sensitivity of the foot and performs a tapping test on the canal area: the appearance of lumbago in the sole confirms nerve irritation. Electroneuromyography remains the main confirmatory method, although in case of damage to individual branches it is not always informative. Magnetic resonance imaging of the ankle shows cysts, masses and tendon changes, and ultrasound shows the nerve and dilated veins. Be sure to exclude polyneuropathy, plantar fasciitis and damage to the lumbar roots.
- Examination by a neurologist and orthopedist
- Tapping test behind the inner ankle
- Electroneuromyography
- MRI of the ankle
- Ultrasound of soft tissues and nerves
- Glucose, thyroid hormones if a metabolic cause is suspected
- X-ray of the foot for deformities
Treatment
Treatment begins with unloading: orthopedic insoles are selected to correct the inward roll of the foot, comfortable shoes with a hard back are recommended, and prolonged standing is limited. Short course anti-inflammatory drugs and drugs for neuropathic pain are used, physical therapy and stretching of the calf muscles are useful. For persistent symptoms, a glucocorticoid injection into the canal area may be performed by a doctor. If a cyst is found, a space-occupying lesion, or conservative treatment for several months has not helped, an operation is performed to cut the ligament and free the nerve.
- Orthopedic insoles and proper shoes
- Limiting prolonged standing and walking on hard surfaces
- Short course anti-inflammatory drugs
- Drugs for the treatment of neuropathic pain
- Exercise therapy and stretching
- Glucocorticoid injection as prescribed by a doctor
- Surgical decompression if ineffective or mass formation