Complex Ankle Fracture-Dislocation
CIM Case: Complex Ankle Fracture-Dislocation
Clinical Scenario
Patient: 45-year-old woman Presentation: Fall down stairs, immediate right ankle pain, unable to weight-bear, witnessed "popping" sound at time of injury Relevant history: Previously healthy, non-smoker, no diabetes, no prior ankle injuries, works as a nurse (standing job) Examination findings:
- Obvious deformity at right ankle
- Foot displaced posterolaterally relative to leg
- Tented skin over medial malleolus (blanching, at risk)
- Moderate swelling, no open wound
- Dorsalis pedis pulse weak but palpable (compare to contralateral)
- Capillary refill 4 seconds in toes
- Sensation diminished over dorsum of foot
- Unable to dorsiflex or plantarflex ankle
- Significant tenderness over lateral and medial malleoli
- Ecchymosis developing
Investigations Provided
Imaging
Image 1: AP and Lateral Radiographs of Right Ankle
Radiological features:
- Trimalleolar fracture-dislocation
- Fibula fracture at level of syndesmosis (Weber B equivalent)
- Spiral/oblique fracture pattern of fibula
- Medial malleolus fracture (transverse)
- Posterior malleolar fragment visible on lateral (approximately 25-30% of articular surface)
- Talus dislocated posterolaterally
- Complete disruption of ankle mortise
- No talar dome fracture visible
- Tibiofibular clear space widened
Image 2: Post-Reduction AP and Lateral
Post-reduction findings:
- Talus relocated into mortise
- Fibula length and rotation improved
- Medial clear space still widened (2mm asymmetry)
- Residual posterior subluxation on lateral view
- Mortise congruity improved but not perfect
Questions & Model Answers
What is the diagnosis and what is the urgency of this injury?
Describe your emergency department management.
What are the soft tissue considerations and when would you delay surgery?
Describe your operative technique for fixing the posterior malleolus.
What are the expected outcomes and complications of trimalleolar fractures?
Key Teaching Points
Pattern Recognition
This pattern suggests Ankle Fracture-Dislocation Emergency:
- Fall mechanism with immediate deformity
- Visible displacement of foot relative to leg
- Tented or blanching skin (especially medially)
- Diminished or absent pulses
- Progressive swelling and ecchymosis
Lauge-Hansen Classification Overview:
| Mechanism | Foot Position | Force Direction | Pattern |
|---|---|---|---|
| SER (Supination-External Rotation) | Supinated | External rotation | Most common (60-70%), spiral fibula |
| SAD (Supination-Adduction) | Supinated | Adduction | Transverse fibula below syndesmosis |
| PER (Pronation-External Rotation) | Pronated | External rotation | High fibula fracture, syndesmosis injury |
| PAB (Pronation-Abduction) | Pronated | Abduction | Bending fibula fracture |
Critical Management Points
- Reduce immediately - tented skin and diminished pulses are emergencies
- Document neurovascular status - before AND after reduction
- Respect soft tissues - delay surgery for swelling/blisters
- Fix posterior malleolus - if >25% articular surface or step >2mm
- Assess syndesmosis - stress test intraoperatively
- Anatomic reduction - 1mm shift = 42% contact area loss
Common Examiner Follow-ups
Q: "How do you assess syndesmotic stability intraoperatively?"
Syndesmotic assessment:
- External rotation stress test - apply external rotation force to foot while holding leg fixed; observe tibiofibular widening on fluoroscopy
- Cotton test - lateral translation of fibula with bone hook; >2mm translation suggests instability
- Compare to contralateral - if available
Fix syndesmosis if:
- Medial clear space >4mm
- Tibiofibular clear space >5mm on mortise view
- Cotton test positive
- Residual instability despite anatomic fracture fixation
Q: "What are the options for syndesmotic fixation?"
| Method | Advantages | Disadvantages |
|---|---|---|
| Screws (3.5-4.5mm) | Familiar, strong | May need removal, may break |
| Suture button | Preserves physiologic motion, no removal needed | Learning curve, more expensive |
| Multiple screws | More stable | More hardware complications |
Current evidence (SynFix trial) suggests equivalent outcomes between screws and suture buttons. Suture buttons may have lower reoperation rate.
Q: "When would you consider non-operative management of an ankle fracture?"
Non-operative indications:
- Stable, undisplaced fracture
- Weber A (below syndesmosis) without medial injury
- Isolated medial malleolus with no lateral or syndesmotic instability
- Non-ambulatory patient
- Severe medical comorbidities precluding surgery
Weight-bearing in boot or cast with serial X-rays to confirm no displacement.
Q: "What is the significance of fibula length and rotation?"
Fibula length and rotation are critical because:
- Fibula is key to mortise stability
- Shortening allows lateral talar shift
- Malrotation (usually external) widens mortise posteriorly
- 1mm lateral talar shift = 42% reduction in tibiotalar contact area
- Even small malreduction leads to eccentric loading and arthritis
Assess on post-op X-ray and CT if concerned.
Related Topics
- Ankle Fractures (Weber Classification)
- Syndesmotic Injuries
- Open Fractures
- External Fixation Techniques
- Post-Traumatic Ankle Arthritis
- Ankle Arthrodesis