Tarsal Tunnel Syndrome
Tarsal tunnel syndrome is an entrapment neuropathy of the posterior tibial nerve as it passes through the tarsal tunnel (a fibro-osseous tunnel). The tarsal tunnel is located in the medial ankle posterior and inferior to the medial malleolus and deep to the flexor retinaculum (laciniate ligament).
- Women are slightly more affected than men (56%).
- All postpubescent ages are affected.
Etiology and Pathophysiology
- Contents within the tarsal tunnel from the anterior to the posterior side include the following: the posterior tibial tendon, the flexor digitorum longus tendon, the posterior tibial artery and veins, the posterior tibial nerve, and the flexor hallucis tendon.
- The posterior tibial nerve passes through the tarsal tunnel, which is formed by three osseus structures—sustentaculum tali, medial calcaneus, and medial malleolus—covered by the laciniate ligament.
- Chronic compression of the posterior tibial nerve within the tarsal tunnel can destroy the endoneurial microvasculature, leading to edema and (eventually) fibrosis and demyelination, which results in symptoms (1),(2).
- Increased pressure in the tarsal tunnel is caused by a variety of mechanical and biochemical mechanisms. The specific cause for compression is identifiable in only 60–80% of cases (1).
- Three general categories: trauma, space-occupying lesions, deformity (1)
- Trauma including displaced fractures, deltoid ligament sprains, or tenosynovitis
- Hindfoot varus or valgus
- Fibrosis of the perineurium
- Other causes:
- Osseous prominences; osteophytes
- Ganglia; lipoma; neurilemmoma
- Inflammatory synovitis
- Pigmented villonodular synovitis
- Tarsal coalition
- Accessory musculature
- In patients with systemic disease (e.g., diabetes), the “double crush” syndrome refers to the development of a second compression along the same nerve at a site of anatomic narrowing in patients with previous proximal nerve damage (3).
- Tarsal tunnel syndrome is associated with certain occupations and activities involving repetitive and prolonged weight-bearing on the foot and ankle (walking, running, dancing).
- Other possible risk factors include (4):
- Heel varus or valgus
- Bifurcation of the posterior tibial nerve into medial and lateral plantar nerves proximal to the tarsal tunnel
Commonly Associated Conditions
Diabetes, systemic inflammatory arthritis, connective tissue disorders, obesity
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