Tarsal Tunnel Syndrome
If we examine the anatomy of the foot, we see that the bone of the heel called the calcaneus has a deep concavity on its inner surface. Through this concavity, pass the nerves and blood supply to the foot, along with a few tendons (fibrous extension of muscles that insert into the bones). On the inside, these structures are protected by the bone surface and on the outside a sheath of tough fibrous tissue called the flexor retinaculum covers them. This outer sheath, along with the bony concavity, form a small tunnel referred to as the tarsal tunnel.
This small tunnel, located just below the inner bump of the ankle, is an enclosed space. Therefore, any swelling or structural enlargement can easily compress the nerves and vessels passing through it and this is what tarsal tunnel syndrome is. This syndrome refers to compression of the nerve called the posterior tibial nerve, which comes from behind the tibia (bone of the lower leg) and passes through the tarsal tunnel, dividing into three branches. One of the branches supplies the heel of the foot while the other two supply the remainder of the foot.
Compression of the tibial nerve may lead to an abnormal sensation in the area supplied by the nerve.
Any condition that causes pressure in the tunnel and compresses the nerve results in tarsal tunnel syndrome. This includes:
- A space-occupying lesion such as a cyst or tumour or a bony projection such as a bone spur
- Enlargement of any structure passing through the tunnel, e.g. swelling of a tendon or varicose veins (the veins become large and tortuous)
- An ankle twist or injury leading to inflammation and swelling
- Flat feet or fallen arches; as the arch of the foot collapses and the foot is placed flat on the ground, the ankle is twisted inwards, pressing upon the nerve.
Compression of the tibial nerve would lead to altered sensation in any of the areas supplied by the nerve.
- This includes pain, tingling, numbness or burning, which is usually limited to the inner side of the ankle or the sole of the foot; however, any area can be involved.
- In some individuals, a specific area is involved, while in others the heel, arch and toes may also be affected
- Pain aggravates with activity or with prolonged standing, while it gets better with rest
- There is an electric shock-like sensation when the area over the affected nerve is pressed (Tinel’s sign). This feeling may radiate towards the leg or the toes.
The symptoms are very important in diagnosing the condition. Tinel’s sign also helps to differentiate the condition. X-rays or an MRI scan is helpful to locate any abnormal lesion or mass in the area.
Treatment involves supportive therapy and eliminating the cause of the problem.
Supportive therapy includes:
- Proper rest and avoidance of any stressful activity
- Ice application and use of anti-inflammatory painkillers
- Restricting movement at the ankle joint and use of supportive shoes or braces to help relieve the pressure and speed up healing
- Use of steroids to help relieve inflammation in the area, if that is the cause
- For flat feet or fallen arches, use of appropriate insole devices such as an arch support helps to reduce the pressure on the nerve
- Massage and exercise may also help to reduce the symptoms
Surgery is advised for cases not responding to conservative measures. The aim of surgery is to decompress the nerve by:
– Removing any space-occupying lesion
– Cutting the outer fibrous sheath (flexor retinaculum) and leaving it open (the gap later heals with scar formation).
Surgery has been reported to improve symptoms in the majority of cases.
Tarsal tunnel syndrome can very adversely affect an individual’s life quality; therefore, it needs to be treated properly.