What X-ray views are recommended to rule out an ankle fracture?

X-ray Views to Rule Out Ankle Fracture

The standard radiographic protocol to rule out ankle fracture should include three views: anteroposterior (AP), lateral, and mortise views, with images extending to include the base of the fifth metatarsal bone. 1, 2

Standard Protocol for Ankle Fracture Evaluation

When to Order X-rays

X-rays should be ordered when any of the Ottawa Ankle Rules criteria are met:

• Inability to bear weight immediately after the injury
• Point tenderness over the medial malleolus
• Point tenderness over the posterior edge or inferior tip of the lateral malleolus
• Point tenderness over the talus or calcaneus
• Inability to take four steps in the emergency department

These criteria have 92-99% sensitivity for detecting ankle fractures 1, 2.

Required Views

1. Anteroposterior (AP) view
2. Lateral view
3. Mortise view (AP view with 15-20° internal rotation)

All three views should include the base of the fifth metatarsal bone distal to the tuberosity 1.

Clinical Considerations

Weight-bearing Views

• When possible, weight-bearing radiographs provide critical information about fracture stability
• A medial clear space of <4 mm confirms stability
• Particularly important for fractures of uncertain stability 1, 2

Special Scenarios Requiring Additional Views

1. Suspected calcaneal fractures

   • Add Axial Harris-Beath view to determine intra-articular extent 1, 2

2. Suspected lateral talar process fracture (snowboarder's fracture)

   • Add Broden view (supine flexed knee with 30-45° internal rotation)
   • These fractures are overlooked 40-50% of the time on routine radiographs 1, 2

3. Children with suspected distal fibular avulsion fractures

   • Consider anterior talofibular ligament view
   • Can identify occult fibular fractures in 26% of lateral ankle sprain patients 1

4. Suspected deltoid ligament disruption

   • Use gravity stress view (more reliable than manual stress view) 1

Controversies in Imaging Protocol

While some research suggests that two views (lateral and mortise) might be sufficient for ankle fracture diagnosis 3, more recent and comprehensive guidelines from the American College of Radiology maintain that all three standard views are necessary 1, 2. A study by Vangsness et al. found that reducing the ankle radiographic series from three to two views would result in a small but significant decrease in fracture detection 4.

Pitfalls to Avoid

1. Failing to include the base of the fifth metatarsal in the radiographic field
2. Missing lateral talar process fractures which are commonly misdiagnosed as simple ankle sprains
3. Not obtaining weight-bearing views when evaluating fracture stability
4. Overlooking signs of instability such as medial tenderness, bruising, swelling, or fibular fracture above the syndesmosis

Advanced Imaging

If initial radiographs are negative but clinical suspicion remains high or pain persists for more than a week, consider:

• CT scan: For complex fractures or occult fractures
• MRI: Gold standard for soft tissue evaluation and detection of occult fractures

However, these are not first-line imaging studies for acute ankle trauma evaluation 1, 2.