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)

Deformity-Related

• Pes planus & Tibialis Posterior Insufficiency (most common)
• Cavus foot (less common)
• Talocalcaneal Tarsal Coalition

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