Approach to ANKLE radiograph

1. Standard Projections

A complete ankle series typically consists of three views, often referred to as the ankle series:

• AP View: 

  • Shows the ankle in the coronal plane.

  • Best for evaluating the medial and lateral malleoli, and the joint space.

    
    

• Mortise View: 

  • This is an AP view taken with the foot internally rotated approximately 15-20 degrees.

  • This rotation is crucial as it projects the lateral malleolus more anteriorly, "opening up" the tibio-talar joint space symmetrically, allowing clear visualization of the superior aspects of the talus, medial malleolus, and lateral malleolus.

    
    

• Lateral View: 

  • Essential for assessing the posterior malleolus, the calcaneus, and the tibial-talar alignment.

Normal AP view	Ankle Mortise view
Overlapping of lateral malleolus and Talar dome	Internal rotation of foot reduces the overlap

2. Systematic Assessment (The ABCS Approach)

A structured, systematic approach to ankle x-ray ensures no pathology is overlooked.

A - Alignment and Anatomy

• Tibiotalar Alignment:

  • On the Lateral View, the long axis of the tibia should align centrally with the long axis of the talus. Check for anterior or posterior talar subluxation.

  • On the Mortise View, the talus should be centered in the mortise.

• Tibia-Fibula Overlap (Distal Syndesmosis):

  • On the AP and Mortise Views, measure the overlap between the distal tibia and fibula.

  • Normal overlap is typically >6 mm on the AP view and ≥1 mm on the Mortise view.

  • Loss of overlap suggests syndesmotic disruption.

• Medial Clear Space (MCS):

  • On the Mortise View, this is the distance between the lateral aspect of the medial malleolus and the medial aspect of the talus.

  • It should be equal to or less than the superior clear space (usually ≤4 mm).

  • Widening suggests a deltoid ligament tear or lateral displacement of the talus.

• Tibiofibular Clear Space (TFCS):

  • On the AP and Mortise Views, this is the distance between the lateral border of the distal tibia and the medial border of the distal fibula.

  • It should be <6 mm.

  • Increased space suggests syndesmotic injury.

B - Bone

• Cortical Integrity: Trace the cortex of the distal tibia, fibula, and talus, looking for any breaks, step-offs indicative of a fracture.

  
  

  • Specifically check the lateral malleolus, medial malleolus, and posterior malleolus (seen best on the lateral view).

  • Look for talar dome fractures (osteochondral lesions), especially on the mortise view.

  • Ensure the calcaneus and proximal fifth metatarsal are incidentally assessed, as these are common associated injury sites (e.g., Jones fracture, Calcaneal fracture).

    
    

• Bone Density: Note any generalized demineralization (osteopenia) or localized changes (e.g., reactive sclerosis).

C - Cartilage and Joints

• Joint Space: Evaluate the uniformity of the superior tibiotalar joint space on all views.

  
  

  • Mortise View: Should show a uniform joint space superiorly, medially, and laterally (the mortise).

  • Narrowing suggests degenerative change (arthritis).

  • Widening of the mortise or specific clear spaces suggests ligamentous injury (e.g., deltoid or syndesmotic injury).

S - Soft Tissues

• Swelling: 

  • Look for general soft tissue swelling, or displacement of normal fat pads.

  • Anterior and Posterior Fat Pads: Note any displacement or obliteration, which can be a subtle sign of an effusion or capsular injury.

    
    

• Foreign Bodies or Air (e.g., subcutaneous emphysema).