When is an ankle x-ray recommended for patients with acute ankle injury?

When to Order Ankle X-rays for Acute Ankle Injury

Ankle radiographs are indicated when patients meet any of the Ottawa Ankle Rules criteria: inability to bear weight immediately after injury, point tenderness over the malleoli/talus/calcaneus, or inability to walk 4 steps in the emergency department. 1

Apply the Ottawa Ankle Rules (OAR) Algorithm

The OAR are validated for patients ≥5 years old and should guide all imaging decisions in acute ankle trauma. 1

Order ankle X-rays if ANY of the following are present:

• Inability to bear weight immediately after the injury 1
• Point tenderness over:
  • Posterior edge or tip of the lateral malleolus 1
  • Posterior edge or tip of the medial malleolus 1
  • Talus 1
  • Calcaneus 1
• Inability to ambulate 4 steps in the emergency department 1

Do NOT order ankle X-rays if:

• Patient can walk without difficulty 1
• No point tenderness over the malleoli, talus, or calcaneus 1
• No exclusionary criteria present (see below) 1

The OAR demonstrate 92-100% sensitivity for detecting ankle fractures, meaning they miss fewer than 2% of fractures. 1

Important Exclusionary Criteria

Order ankle X-rays regardless of OAR if the patient has: 1

• Neurologic disorder or peripheral neuropathy 1
• Intoxication or altered mental status 1
• Distracting painful injuries 1
• Age <5 years 1

These patients cannot be reliably assessed using the OAR and require radiographic evaluation. 1

Standard Radiographic Protocol

When X-rays are indicated, order three standard views: 1

• Anteroposterior view 1
• Lateral view 1
• Mortise view (must include base of fifth metatarsal distal to tuberosity) 1

Weight-bearing radiographs should be obtained if possible, as they provide critical information about fracture stability, particularly for malleolar fractures. 1

Critical Timing Consideration

Avoid manipulating the ankle before obtaining radiographs unless there is neurovascular deficit or critical skin injury. 1, 2 Manipulation before X-ray significantly increases the risk of requiring re-manipulation (44% vs 18%, p=0.03) and exposes patients to unnecessary sedation risks. 2

When Initial X-rays Are Negative But Pain Persists

If ankle pain persists for >1 week but <3 weeks after negative initial radiographs: 1, 3

• Order MRI ankle without IV contrast as the next imaging study 1, 3
• MRI is superior to CT for detecting occult fractures, bone marrow edema, and ligamentous injuries 1, 3, 4
• Up to 50% of hairline fractures (especially lateral talar process) may be radiographically occult 4

Common Pitfalls to Avoid

• Do not order foot radiographs routinely with ankle X-rays unless there is specific midfoot tenderness at the navicular or base of fifth metatarsal. 1 Studies show no additional foot fractures beyond the fifth metatarsal base when ankle fractures are present. 1

• Do not skip radiographs in patients with "just a sprain" if they meet OAR criteria. 5 Clinical examination alone has only 97.5% accuracy, which is insufficient to safely exclude fractures. 6

• Do not use CT or MRI as first-line imaging for acute ankle trauma when OAR are positive. 1 Radiographs remain the appropriate initial study. 1, 4

• Pay special attention to snowboarder's fractures (lateral talar process), which are missed on routine radiographs 40-50% of the time. 1 Consider Broden view if clinical suspicion is high with swelling below the lateral malleolus. 1