The Ankle, Talus and Calcaneum

Ottawa rules | Projections | Accessory ossicles | Mortise fractures
Weber classification | Salter-Harris classification | Toddler's fracture
Talus | Calcaneum

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Learning outcomes
  • Understand Ottowa rules for ankle imaging
  • Assess skeletal radiographs using a systematic approach
  • Understand the importance of good radiographic positioning
  • Describe ankle anatomy
  • Understand mechanisms of injury and the likely fractures/dislocations which may result
  • Recognise less common fractures to the individual bones around the ankle
  • Understand the Weber classification
  • Accurately describe dislocations and associated fractures
  • Understand common eponyms
  • Recognise potential ligament injuries
  • Understand the paediatric Salter-Harris classification
  • Recognise normal variants and their significance (eg, accessory ossicles)
Ottawa rules(1)

These describe the requirements for plain x-rays within the clinical context of an ankle injury. They state that:


AP mortise
This is obtained with internal rotation so that the fibula does not overlap the talus. This is important so that any joint space widening can be demonstrated. It also serves to clear the lateral joint space so that lateral talar dome fractures can be identified. Assess for any soft tissue swelling medially and laterally.

Lateral soft tissue swelling, no fracture

Open collimation to include the calcaneum, 5th metatarsal base and dorsal surfaces of the talus and navicular (all common sites for avulsion fractures). Look for an anterior joint effusion, as this can be significant. An effusion is seen as an area of increased density that pushes out the adjacent fat plane.

Joint effusion, no fracture

Suboptimal positioning AP mortise
?Talar dome fracture. However, appearance is due to inadequate mortise view, and the lateral joint space not being clearly demonstrated:

Lateral mortise not demonstrated

Suboptimal positioning lateral
?Fracture lateral malleolus. However, appearance is due to inadequate lateral view and the medial and lateral malleoli not being superimposed:

Off lateral
Accessory ossicles - Normal variants
Mortise fractures
Widening of medial mortise
Wide syndesmosis
Maisonneuve fracture   Maisonneuve fracture
Fracture posterior malleolus, fracture fibula   Fracture posterior malleolus, fracture fibula
Weber Classification
A = Lateral malleolar fracture below the level of the syndesmosis.
Medial malleolar fracture; oblique (if present).
B = Lateral malleolar fracture at the level of the syndesmosis, running proximally.
Medial malleolar fracture; transverse. Or a tear of the ligament.
C = Lateral malleolar fracture originating proximal to the joint line.
Medial malleolar fracture; transverse. Or a tear of the ligament.

Additional to B or C may be a posterior malleolus fracture.

Salter-Harris Classification
Salter-Harris I fibular growth plate

Salter-Harris II fibular metaphysis     Salter-Harris II fibular metaphysis
Salter-Harris III (Tillaux fracture) tibial epiphysis   Salter-Harris III (Tillaux fracture) tibial epiphysis
Salter-Harris IV tibial epiphysis and metaphysis   Salter-Harris IV tibial epiphysis and metaphysis
Toddler's Fracture
Toddler's fracture   Toddler's fracture
Talar dome fracture   Talar dome fracture
Osteochondritis dissecans
Avulsion dorsal aspect talus
Subtalar fracture-dislocation   Subtalar fracture-dislocation
Avulsion anterior process calcaneum
Avulsion anterolateral calcaneum
Normal Boehler's angle Abnormal Boehler's angle Compression fracture calcaneum

self test


(1) "Decision rules for the use of radiography in acute ankle injuries" Stiell IG et al, JAMA (1993) 269:1127-1132 (click for full text download)

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