Tarsal Coalition

Aetiology

• Prevalence: Found in ~1% of the population, potentially more.
• Inheritance: Autosomal dominant.
• Pathogenesis: Failure of mesenchymal differentiation in peritalar joints.
  • Results in a fibro-osseus bar instead of a joint.
  • 20% have multiple coalitions in the same foot.
  • 50% are bilateral.

Associations

• Multiple Coalitions: Linked to Apert’s syndrome and fibula hemimelia.

Pathoanatomy

• Common Locations:
  • Calcaneonavicular: Most common site.
  • Talocalcaneal: Second most common, often in the medial facet.
  • Other Coalitions: Rare, can occur between any peritalar joints.

Clinical Presentation

• Symptoms typically appear once the coalition ossifies and becomes painful.
  • Calcaneonavicular coalitions present earlier than talocalcaneal (age 8-15 years).
  • Symptoms: Recurrent ankle sprains, difficulty on uneven terrain.

Examination

Classification

• By Anatomy of Coalition:
  • Based on location and involved joints.
• By Nature of Bar:
  • Fibrous, Cartilaginous, or Osseous bar types.

Imaging

• X-Ray Findings:
  • Negative Meary’s Angle: Indicates planovalgus deformity.
  • Anteater Sign: Suggestive of calcaneonavicular coalition.
  • C-Sign: Seen in talocalcaneal coalitions; forms a “C” shape between talus and calcaneus.
  • Dorsal Talar Beaking: Non-specific finding, common with coalition.
• Advanced Imaging:
  • CT Scan: Gold standard for evaluating osseous coalitions.
  • MRI: Confirms fibrous or cartilaginous coalitions.

Management

Non-Operative

• Indications: Early presentation with flexible deformity.
• Treatment: Activity modification and orthotic support.

Surgical Intervention

• Indications: Failed non-operative management, arthritis, rigid deformity.
  • Resection: Preferred for calcaneonavicular and <50% talocalcaneal coalitions.
    • Advantages: Preserves motion but may have recurrence.
  • Fusion: Recommended if >50% of the medial facet is involved.
    • Types: Subtalar fusion preferred; may require triple fusion in severe cases.
    • Indications: Late presentation with osteoarthritis.
  • Additional Procedures: Corrective osteotomies for fixed valgus deformity.