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

---

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:

Critical Management Points

1. Reduce immediately - tented skin and diminished pulses are emergencies
2. Document neurovascular status - before AND after reduction
3. Respect soft tissues - delay surgery for swelling/blisters
4. Fix posterior malleolus - if >25% articular surface or step >2mm
5. Assess syndesmosis - stress test intraoperatively
6. Anatomic reduction - 1mm shift = 42% contact area loss

---

Common Examiner Follow-ups

Q: "How do you assess syndesmotic stability intraoperatively?"

Syndesmotic assessment:

1. External rotation stress test - apply external rotation force to foot while holding leg fixed; observe tibiofibular widening on fluoroscopy
2. Cotton test - lateral translation of fibula with bone hook; >2mm translation suggests instability
3. 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?"

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