Triplane Fracture of the Ankle

Etiology

  • Definition: Distal tibia epiphyseal fracture involving three planes: coronal, sagittal, and axial.

  • Demographics:

    • More common in boys than girls due to later physeal closure.
    • Girls present younger because their physis closes earlier.

  • Physeal Closure Order:

    1. Central (first)
    2. Anteromedial
    3. Posteromedial
    4. Posterolateral
    5. Anterolateral (last)
    • Rough sequence: Posteromedial to anterolateral closure.

  • Cause: External rotational injury.

  • Age Group: Adolescents (rare in children <10 years or >16 years).

  • Associated Injuries: 50% of cases have an associated fibula fracture.

Diagnosis

  • Imaging:
    • X-rays: AP, lateral, and mortise views.
    • CT Scan: Essential for surgical planning, especially to decide if surgery is required.

Surgical Anatomy

  • Fracture Types:
    • 2-part fracture: Most common (70%), with medial or lateral fractures. Lateral fractures are more common.
    • 3-part fracture: Classic “Mercedes Benz” configuration on axial CT, where a fracture line disconnects the Tillaux fragment from the posterior fragment.
    • 4-part fracture: Very rare.
  • Variants:
    • Extra-articular or intramalleolar: The articular surface is unaffected, and the sagittal fracture line exits in the medial malleolus.

Management

Non-Operative:

  • Indications:
    • Extra-articular fractures.
    • Displacement <2mm.
  • Treatment:
    • Long leg plaster, converted to below knee after a few weeks.

Operative:

  • Indications:
    • Displacement >2mm.
    • Joint instability.
    • If there is >2 years of growth left, consider surgery with a lower threshold.
  • Surgical Planning:
    • CT Scan Evaluation:
      • Assess fragment locations.
      • Determine if it’s a 2-part or 3-part fracture.
      • Identify whether the anterior sagittal fracture is medial or lateral.
      • Evaluate the Tibialis anterior tendon.
    • Surgical Approach:
      • Anteromedial or anterolateral, depending on where the fracture exits.
      • Allows for periosteum removal, anatomical reduction, and joint assessment.
  • Fixation:

    • Avoid crossing the physis unless the patient is near skeletal maturity.

    • Screws: Cancellous screws, either cannulated 4mm or solid 3.5mm.

    • Steps:

      1. Address the anterior coronal fracture first (anterolateral approach).
      2. Remove periosteum, clear fracture site.
      3. Reduce the posterior fragment by dorsiflexing and internally rotating the foot.
      4. Fix the posterior fragment with an AP screw.
      5. Anatomically reduce the anterior epiphysis to the posterior fragment and stabilize with a screw.
      • Screw Orientation:
        • Typically anterolateral to posteromedial.
        • Medial to lateral in medial 2-part fractures.
      • Pre-op CT scan is essential for planning screw placement.

Outcome

  • Best results: Achieved with anatomical reduction.
  • Complications:
    • Post-traumatic arthrosis.
    • Premature physeal arrest.
  • Long-term Follow-up: Required to monitor complications.

Key Visuals:

  • Mercedes Benz Sign: Seen in 3-part triplane fractures where the coronal split separates the Tillaux and posterior fragments.
  • Variants: Extra-articular and intramalleolar types.
Back to top