Tarsal Tunnel Syndrome

• Tarsal tunnel syndrome is entrapment of the tibial nerve or its distal branches caused by compression or traction as the nerve courses through the tarsal tunnel.
• Anatomy :
  • Proximal tarsal tunnel:
    • Fibro-osseous space that contains (from anterior to posterior) the PTT, flexor digitorum longus tendon, posterior tibial artery and vein, tibial nerve, and flexor hallucis longus tendon.
    • The tarsal tunnel is a continuation of the deep posterior compartment of the leg.
    • The floor is composed of the medial surface of talus, the sustentaculum tali, and the medial wall of the calcaneus.
    • The roof is composed of the flexor retinaculum, which begins up to 10 cm proximal to the medial malleolus; each tendon and the neurovascular bundle is contained by separate fibro-osseous compartments that connect with the retinaculum.
  • The tibial nerve gives rise to the MCN, MPN, and LPN; nerve anatomy can be variable.
    • MCN:
      • 69-90% of the time, arises directly from the tibial nerve
      • Also can arise from the LPN
      • Single nerve branch in 79%, but can be multiple branches
      • Provides sensation to medial heel
    • MPN and LPN:
      • Formed by terminal bifurcation of tibial nerve
      • 93-96% of the time, bifurcation takes place within the tarsal tunnel.
      • Remainder occurs proximal to tarsal tunnel, in the leg.
    • MPN:
      • Provides sensation to plantar foot, big toe, 2nd toe, 3rd toe, and medial border of the 4th toe
      • Provides motor innervation to the abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, and 1st lumbrical
    • LPN:
      • Provides sensation to lateral border of the 4th toe and to the 5th toe
      • Provides motor innervation to the quadratus plantae, abductor digiti minimi, flexor digiti minimi brevis, lateral 3 lumbricals, adductor hallucis, and the interossei
      • Most common nerve involved in tarsal tunnel syndrome
      • The distal tarsal tunnel begins as the MPN and LPN pass through separate fibrous tunnels deep to abductor hallucis.
    • MPN may be trapped between the navicular and the abductor hallucis, or at the knot of Henry.
    • The 1st branch of the LPN may be trapped in fascia of abductor hallucis as it travels to abductor digiti quinti, causing heel pain.

• In a literature review of 186 cases, patients ranged from 14-80 years old .
• Slightly more common in females (56%) than in males

• No clear risk factors have been proven, but several authors have associated tarsal tunnel syndrome with certain occupations and activities.
  • Jogger’s foot: Excessive hindfoot valgus is theorized to stretch the tibial nerve during repetitive activity such as running .
  • Activities that consist of repetitive squatting or crouching, such as in race jockeys

• Tarsal tunnel syndrome is caused by compression or tension on the tibial nerve, resulting in damage .
• Unyielding structure of tarsal tunnel places nerve at risk for injury from local volume changes.
• Compressive etiologies: Sensory abnormalities are hypothesized to result from nerve ischemia, whereas late motor dysfunction may be the result of direct nerve compression injury.
• Chronic traction injuries produce fibrosis of the epineurium and stiffness, which makes the nerve less able to compensate for other insults.

• The specific cause is identifiable in only 60-80% of patients ; causes can be grouped into 3 categories: Trauma, space-occupying lesion, and deformity.
• Most common causes:
  • Trauma: 17%
  • Varicosities: 13%
  • Hindfoot varus: 11%
  • Fibrosis: 9%
  • Hindfoot valgus: 8%
• Other causes of compression include ganglia, lipoma, neurilemmoma, inflammatory synovitis, PVNS, tarsal coalition, and accessory musculature.

Tests

• Peripheral neuropathy (diabetes)
• Peripheral neuritis
• Peripheral vascular disease
• Morton neuroma
• Metatarsalgia
• Subtalar joint arthritis
• Tibialis posterior tendinitis/dysfunction
• Plantar fasciitis
• Complex regional pain syndrome
• Proximal injury or compression of the tibial branch of the sciatic nerve
• Lumbar radiculopathy

• Initially, nonoperative management is recommended except for acute tarsal tunnel syndrome or in the setting of a known space-occupying lesion (excluding synovitis) .
  • Rest/immobilization
  • Orthotics
  • Anti-inflammatories, including steroid injections and nonsteroidal drugs
  • Medications that alter neurogenic pain (tricyclic antidepressants, antiepileptic drugs, nerve blocks)
  • Physical therapy (desensitization)
  • Compression stockings
  • Weight loss

• Surgery is indicated:
  • If nonoperative measures fail after a 3-6-month trial
  • In the setting of acute tarsal tunnel syndrome
  • If the cause is a space-occupying lesion
• Use a curved posteromedial incision, following the course of the tibial nerve.
• Release the entire flexor retinaculum.
• Release the MPN and LPN distally as they pass deep to the abductor hallucis and into the plantar foot.
• Excise space-occupying lesions and address underlying pathology such as tendon dysfunction and tarsal coalition.
• Minimize surgical dissection to help limit scar formation.

• Best results are seen in young patients, when surgery is performed early in the disease process (before motor abnormalities occur) or when a discrete lesion is found.
• In a review of 25 articles, 91% of 110 patients had improvement or resolution of symptoms with surgery.
• A more recent study with longer patient follow-up and more stringent criteria has shown poorer outcomes, with deteriorating results over time .

• The main adverse outcome is unsuccessful surgical intervention: No improvement, partial/incomplete improvement, or temporary improvement with recurrence of symptoms .
• 5 causes of failed tarsal tunnel release:
  • Incorrect diagnosis
  • Incomplete release
  • Adhesive neuritis (external scar formation)
  • Intraneural damage (systemic disease, direct nerve injury)
  • Failure to treat all sources of nerve compression in a double-crush phenomenon
• Examination of the incision length is the most important part of the physical examination in determining whether an adequate release was done initially.
• Electrodiagnostic studies are not helpful for diagnosing tarsal tunnel syndrome after a failed release.
• Repeat surgical release, combined with a barrier procedure (vein or synthetic graft wrapping around the nerve), is the operative treatment of choice for adhesive neuritis.
• Results for revision surgery are poorer than those for primary surgical release.

FAQ