Ankle Fractures

Essentials

• The physician should be able to differentiate between stable and unstable ankle fractures and plan the treatment accordingly.

Definitions

• In this text, the term ”ankle fracture” refers to fractures of the malleolus (also high fibular fractures) caused by a twisting motion.
• Three ”malleolar” sites: lateral, medial and the posterior triangle (avulsion fracture of the posterior tibiofibular [TFP] ligament)
• Stable ankle fractures are fractures of the malleolus where the talus has not dislocated from the tibial articular surface.

Anatomy

• The weight of the body is transmitted to the talus, which wedges tightly into the ankle mortise situated between the medial and lateral malleoli.
• Syndesmosis ligaments: the anterior (TFA) and posterior (TFP) tibiofibular ligaments, the syndesmosis ligament, the interosseous membrane
• The most important structure in the prevention of external rotation of the talus is the deep portion of the deltoid ligament
• Lateral collateral ligaments prevent the inversion of the ankle.

Classification and mechanism of injury

• Weber classification
  • A. Transverse fracture of the lateral malleolus below the talocrural joint (rare)
    • The mechanism of injury involves supination of the foot (ankle inversion).
    • Small ligament avulsion fracture on the tip of the malleolus associated with ligament injuries of the ankle is not a Weber type A fracture as such; iinstead, it is treated like a ligament injury of the ankle.
  • B. Spiral fracture of the lateral malleolus, which begins at the ankle joint and travels upwards towards the posterior aspect (the most common type: 70-80%)
    • Supination of the foot and external rotation of the talus
  • C. ”High fibular fracture” (15-20%): fracture of the fibula, which starts above the ankle joint
    • Pronation of the foot (ankle abduction) and usually external rotation of the talus
• Types A, B and C are further divided into subcategories according to the extent of medial involvement.

Diagnosis

Clinical diagnosis

• Clarify the mechanism of injury
  • Twisting of the ankle, for example when slipping
  • The patient is not always able to give an exact account of the mechanism of injury.
• Visual inspection
  • Is the ankle dislocated? Deformity
  • Swelling and haematomas and their location
• Palpation
  • Is there tenderness both on the lateral and medial sides?
  • Testing the stability: does the talus stay within the ankle mortise?
  • Palpate the entire lower leg in order to locate all areas of tenderness.
    • Remember the possibility of high fibular fracture and syndesmosis injury.
    • A syndesmosis injury may occur without a simultaneous fracture.

Radiological diagnosis

• Indications for radiography: see Ottawa ankle rules Ankle Sprain
• If an ankle fracture is suspected, a mortise projection and a lateral projection will almost always suffice.
  • The entire lower leg should be x-rayed if a high fibular fracture is suspected clinically.
• A mortise projection is taken with the foot in 10-15 degrees of internal rotation in order to obtain a true anteroposterior view of the ankle mortise.
• In a normal ankle, the articular surfaces of the tibia and the talus are parallel to each other.
• In a mortise projection, the radiological joint space is equally wide between the tibia and the talus and between the lateral malleolus and the talus.
• The width of the syndesmosis is dependent on the projection (difficult to estimate from plain x-rays).

Stability assessment

• If instability is suspected, the patient should be referred to a health care facility where the stability can be tested using fluoroscopy.
• In a Weber A fracture, the ankle fork is practically always stable.
• Weber B fractures of the lateral malleolus
  • Findings suggesting an unstable fracture
    • Pain, swelling and haematoma formation on the medial side of the ankle (injury to the deep portion of the deltoid ligament)
    • The talus shows pathological posterolateral movement during stability testing.
    • The fracture of the lateral malleolus associated with marked dislocation
    • An x-ray shows joint incongruence.
      • Tilting of the articular surface of the talus in relation to the articular surface of the tibia (talar tilt)
      • Posterolateral displacement of the talus (talar shift)
      • Medial joint space > 5 mm is clearly suggestive of an unstable fracture.
• High fibular fractures
  • If the fracture is caused by a twisting injury, the fracture begins at the medial side.
    • The ankle is unstable in almost all cases.
  • If the fracture is caused by a direct blow, the treatment is conservative. Immobilization is usually not required.

Treatment

Stable ankle fractures

• Fractures of the lateral malleolus without medial injury (fracture or injury to the deltoid ligament), Weber A and B
  • Conservative treatment
    • A short leg cast worn for 2-4 weeks provides good pain relief.
    • The patient may bear weight as tolerated.
    • Treatment may also consist of wearing an orthosis.
    • Repeat x-rays as considered necessary; usually not needed.
• Fractures of the medial malleolus without lateral injury may be treated conservatively but the decision is made in specialized care.

Unstable ankle fractures

• Treatment of unstable ankle fractures is surgical: emergency referral to specialized health care.

Reduction of a dislocated ankle

• The reduction must be carried out as soon as possible.
  1. Provide analgesia.
  2. Grasp the patient's foot by the heel with one hand whilst holding the lower leg tightly with the other.
  3. Reduce the dislocation by correcting the shortening and posterolateral displacement of the limb by applying downward and anteromedial traction to the heel.
  4. Apply a padded plaster cast or a supporting splint, and refer the patient for further treatment without delay.
• After surgery, the ankle is usually immobilised with a short plaster cast for 4-6 weeks. Weight bearing is decided individually.

Treatment of ankle fractures in special populations

• Ankle fractures in elderly patients are treated according to the same principles as those in younger patients.
• Ankle fractures in patients with diabetes, comorbidities, alcoholism, arteriosclerosis obliterans (ASO)
  • Surgery is associated with more complications if
    • the patient has neuropathy
    • the peripheral pulses cannot be palpated.
  • Decisions regarding treatment should be reserved for specialist health care.