CIM Case: Triplane Fracture

Clinical Scenario

Patient: 12-year-old girl Presentation: Fall from trampoline 4 hours ago, landed awkwardly on right ankle, immediate pain and swelling, unable to weight-bear Relevant history: External rotation mechanism, no previous ankle injuries, healthy otherwise, started menarche 6 months ago (approaching skeletal maturity) Examination findings:

• Swelling and bruising around right ankle (lateral and medial)
• Tenderness over lateral and posterior ankle
• Unable to range ankle due to pain
• No open wounds
• No bony deformity visible externally
• Toes warm, pink, moving, sensation intact
• Dorsalis pedis and posterior tibial pulses palpable

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Investigations Provided

Laboratory Results

Imaging

Image 1: AP, Lateral, and Mortise Ankle Radiographs

Radiological features:

• AP view: Vertical fracture line through lateral distal tibial epiphysis (Salter-Harris IV component)
• Lateral view: Posterior metaphyseal fragment (Salter-Harris II component)
• Mortise view: 3mm articular step visible at tibial plafond
• Physis partially closed centrally, open peripherally (transitional physis)
• Fibula intact
• No talar shift or widening of mortise

Image 2: CT Scan with 3D Reconstruction

CT findings:

• Three-part triplane fracture confirmed
• Epiphyseal fragment (anterolateral) with 4mm displacement
• Metaphyseal fragment (posterior) with 3mm displacement
• Intact central tibial portion
• Articular step 3.5mm at tibial plafond
• No fibula fracture
• No additional fragments

Questions & Model Answers

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Key Teaching Points

Pattern Recognition

This pattern suggests Triplane Fracture:

• Adolescent (12-15 years) with ankle injury
• External rotation mechanism
• Different fracture patterns on AP vs lateral X-rays
• Salter-Harris III appearance on AP, SH II on lateral
• Partially closed physis on imaging

Distinguish from Tillaux Fracture:

Key Imaging Clue: If AP looks like SH III and lateral looks like SH II → think TRIPLANE

Critical Management Points

1. Always get CT - X-rays underestimate displacement and miss complexity
2. <2mm articular step = non-operative - cast for 6 weeks
3. ≥2mm articular step = ORIF - anatomic reduction essential
4. Periosteum may block reduction - open if closed reduction fails
5. Physeal arrest rare - physis nearly closed, minimal growth remaining
6. Excellent prognosis - >90% good/excellent outcomes with anatomic reduction

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Common Examiner Follow-ups

Q: "What is the sequence of distal tibial physeal closure?"

The distal tibial physis closes asymmetrically over 18 months:

1. Central (Kump's bump) - first to close
2. Medial
3. Posterolateral
4. Anterolateral - last to close

This creates the "transitional" period where only part of the physis is open, predisposing to Tillaux and triplane fractures. The anterolateral fragment in a Tillaux is the "last to close" region.

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Q: "What is the difference between a 2-part and 3-part triplane fracture?"

Fixation principles are the same - restore articular congruity and stabilise fragments. 3-part may need more screws.

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Q: "Can you treat a 3mm step non-operatively?"

Traditional teaching is ≥2mm requires ORIF due to risk of post-traumatic arthritis. However:

• Some argue 2-3mm may be acceptable in weight-bearing tolerant ankle
• Long-term studies show poor outcomes with >2mm step
• Standard of care remains operative for ≥2mm
• Document discussion with family if considering conservative for borderline cases

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Q: "This child has a triplane with a fibula fracture. How does that change things?"

A fibula fracture with triplane is unusual but can occur:

• Suggests higher energy mechanism
• May have syndesmotic component
• Assess syndesmosis on CT and clinically
• Fix fibula if unstable or displaced
• May need syndesmotic fixation if disrupted
• Otherwise, same principles apply for tibial fixation

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Related Topics

• Tillaux Fracture
• Salter-Harris Classification
• Adolescent Ankle Fractures
• Physeal Injuries
• Ankle ORIF Techniques
• Paediatric Trauma Principles