Tarsal tunnel syndrome refers to compression of the posterior tibial nerve. Compression of the posterior tibial nerve has many etiologies, but in most cases the cause is unknown. Tenderness of the tarsal tunnel is a sign of tarsal tunnel syndrome.
Structure and function
The tarsal tunnel is the space located posterior and inferior to the medial malleolus, lateral to the calcaneus and talus, and medial to the flexor retinaculum. Many structures run through the tarsal tunnel, including, from anterior to posterior, the tibialis posterior tendon, the flexor digitorum longus tendon, the posterior tibial artery, tibial nerve, and flexor hallucis longus.
Post-traumatic swelling is one possible explanation for the neuropathy. A space occupying lesion, such as a ganglion cyst, swollen tendon, varicosity, or bone spur, could also compress the posterior tibial nerve in the confined space of the tarsal tunnel. Ankle deformities and pes planus can contribute to tarsal tunnel syndrome as well. Complex regional pain syndrome should be considered if there is regional discoloration, swelling, temperature changes, allodynia, or hyperesthesia present. If the pain has a stocking distribution, a diabetic or peripheral neuropathy may be the cause. Also, if there is leg and thigh pain accompanying the tarsal tunnel symptoms, a herniated lumbar disk should be considered.
Treatment options and outcomes
The vast majority of patients with tarsal tunnel syndrome can (and should) be treated nonoperatively. The primary approach to treating this condition is to attempt to decrease the repetitive traction injury across the nerve and the other structures in this area of the foot. In this regard, treatment is quite similar to that for acquired adult flatfoot deformity and plantar fasciitis. In fact, these three conditions (tarsal tunnel, acquired adult flatfoot, and plantar fasciitis) together have been labeled as the terrible triad and it is not uncommon to see them all together in one patient. This patient is typically someone with a flattened arch of the foot who is overweight.
- Comfort shoes designed to disperse the force more evenly across the foot can be very helpful.
- A prefabricated orthotic with a supportive arch will help to disperse the force more evenly across the foot may also be helpful.
- Stretching exercises designed to stretch the calf muscle and thereby indirectly decrease the load through this area of the foot may also be helpful.
- Weight loss will often end up being a critically important component of non-operative treatment, as this will serve to decrease the repetitive forces through this area of the foot.
- Activity modification to limit the amount of standing and walking and thereby the amount of repetitive injury to this area is also an important component of nonoperative management. Physical therapy to establish exercise program characterized by appropriate fitness and stretching exercises, as well as some localized massage to help desensitize the area and perhaps breakdown scar may be of some benefit.
- Corticosteroid injections may help to decrease the swelling around the nerve in the short and intermediate term. However, it is unclear what effect they have in the long term. In addition it is possible to injure the nerve during the injection process.
Tarsal tunnel release has been proposed as a surgical option for treating tarsal tunnel syndrome. This involves a neurolysis of the tibial nerve, which requires identifying and freeing up the tibial nerve as it passes the inside of the ankle and hindfoot. This is done by releasing any tight structures and removing any obvious scar on the outer aspect of the nerve. It has been suggested that tarsal tunnel syndrome in conjunction with a mass effect, such as a bone spur or ganglion cyst, may do better. In theory, removing the mass should help the patient’s symptoms. In practice, this is not always proven to be the case, because scarring can occur around the nerve during surgery, which may unfortunately also cause compression. Furthermore, by operating around the nerve, any postoperative bleeding will have a tendency to scar the nerve further. Thus the main potential surgical complication specific to tarsal tunnel release is hypersensitivity in the area of surgery, due to failure to eradicate the symptoms and in some cases, making the symptoms worse. Other potential complications that are not specific to tarsal tunnel surgery include wound healing problems, infection, deep vein thrombosis (DVT), pulmonary embolism (PE), and complex regional pain syndrome.
Risk factors and prevention
posterior tibial nerve, terrible triad, adult acquired flatfoot deformity, pes planus, plantar fasciitis,