Tarsal Tunnel Syndrome

Epidemiology

  • Uncommon
  • More common in diabetics
  • Twice as common in those with carpal tunnel syndrome

Aetiology

  • Compression of the tibial nerve or its branches within the tarsal tunnel
  • Often an underlying cause

Traumatic

  • Sustentaculum fracture
  • Medial process calcaneus fracture
  • Direct blow

Space-Occupying Lesion

  • Lipoma
  • Varicosities
  • Ganglion
  • Synovitis of tendons in Rheumatoid Arthritis (RA)

Idiopathic

  • Likely related to diabetes

Pathoanatomy

Tarsal Tunnel Boundaries

  • Medial Malleolus
  • Medial aspect of talus and calcaneus
  • Flexor Retinaculum
  • Abductor Hallucis

Tarsal Tunnel Contents

  • Tibialis Posterior (TP)
  • Flexor Digitorum Longus (FDL)
  • Posterior Tibial Artery
  • Venae Comitantes
  • Tibial Nerve
  • Flexor Hallucis Longus (FHL)

Histology

  • Nerve narrowing and perineural fibrosis
  • Same histologic changes as any compression neuropathy
  • These findings may be present in asymptomatic individuals

Clinical Features

  • Often vague symptoms
  • Pain and paresthesias in the whole sole of the foot
  • May be isolated to medial or lateral plantar nerve distribution
  • Can be confused with Plantar Fasciitis or Baxter’s Nerve Compression
    • Baxter’s Nerve: 1st branch of lateral plantar nerve to abductor digiti quinti

Diagnosis

  • Clinical Diagnosis – requires:
    • Typical pain and paresthesia in correct distribution
    • Positive Tinel’s test
    • Positive provocation test – dorsiflexion and eversion
  • Must rule out pes planus or other contributory deformities

Supplementary Investigations

  • Nerve Conduction Studies (NCS) – sensory more sensitive than motor
  • MRI – useful if space-occupying lesion is suspected

Management

Non-Operative

  • Identify and correct deformity first
  • Insoles to correct foot posture if present

Surgical

  • Correct deformity if likely contributory
  • Otherwise, decompression of:
    • Flexor Retinaculum (risk of bowstringing)
    • Abductor Hallucis
    • Excision of space-occupying lesions

Results

  • 80% success rate in best-selected patients – warn patients

Complications

  • Damage to other tarsal tunnel structures
  • Recurrence – due to incomplete release
  • Bowstringing – over-zealous flexor retinaculum release
  • Poor revision success rate – some surgeons do not attempt revision

Anterior Tarsal Tunnel Syndrome

Definition

  • Compression of Deep Peroneal (DP) nerve beneath inferior part of the extensor retinaculum

Causes

  • Osteophytes from ankle or talonavicular joint (TNJ)
  • Tightly laced shoes
  • Synovitis of tendons
  • Space-occupying lesion (e.g., ganglion, lipoma)

Symptoms & Signs

  • Pain and paresthesias over the 1st web space
  • Positive Tinel’s sign
  • Provoked by plantarflexion (worse at night)

Management

Non-Operative

  • First-line treatment

Surgical

  • Decompression by release of inferior extensor retinaculum
  • Care to avoid damage to dorsalis pedis artery

Results

  • Unpredictable outcomes
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