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

Investigations Provided

Laboratory Results

Test	Result	Normal Range	Interpretation
N/A	-	-	Bloods not routinely required for isolated fracture

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

What is a triplane fracture and why does it occur at this age?

What imaging would you order and what are you looking for?

What is your non-operative management for a minimally displaced fracture?

Describe your operative technique for this displaced fracture.

What if the fracture won't reduce? What could be blocking reduction?

What are the potential complications and how would you follow up this patient?

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:

Feature	Triplane	Tillaux
Planes	3 (sagittal, axial, coronal)	2 (sagittal, axial)
Metaphyseal fragment	Yes	No
SH classification	SH IV equivalent	SH III
X-ray appearance	Different AP vs lateral	Similar AP and lateral

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

Critical Management Points

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

Common Examiner Follow-ups

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

The distal tibial physis closes asymmetrically over 18 months:

Central (Kump's bump) - first to close
Medial
Posterolateral
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.

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

Type	Description	Fragments
2-part	Epiphyseal and metaphyseal fragments connected	1 large lateral fragment + medial tibial shaft
3-part	Epiphyseal and metaphyseal fragments separate	Anterolateral epiphysis + posterior metaphysis + medial shaft
4-part	Additional fragment(s)	Variable

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

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

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

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

Triplane Fracture