Description

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).

Epidemiology

• 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
  • Varicosities
  • 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).

Risk Factors

• 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):
  • Varicosities
  • 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