Obtain an Ankle X-ray, Not a Foot X-ray
For a 45-year-old healthy female with pain over the dorsum of the talus after a low-energy twist injury, you should obtain ankle radiographs (anteroposterior, lateral, and mortise views), not a dedicated foot series. 1
Reasoning Based on ACR Guidelines and Ottawa Ankle Rules
Apply the Ottawa Ankle Rules First
This patient meets criteria for ankle imaging based on the Ottawa Ankle Rules (OAR), which have 92-99% sensitivity for detecting ankle fractures 1. The key criterion here is point tenderness over the talus, which specifically triggers the need for ankle radiographs, not foot films 1.
The OAR specify imaging is indicated when there is:
- Point tenderness over the medial malleolus, posterior edge or inferior tip of the lateral malleolus, talus, or calcaneus
- Inability to bear weight immediately after injury
- Inability to ambulate 4 steps in the emergency department
Why Ankle Films, Not Foot Films
The ACR Appropriateness Criteria explicitly state that foot radiographs should not be performed in the presence of ankle inversion injury or ankle fracture due to low yield 1. A retrospective study of 243 patients who had both ankle and foot radiographs demonstrated that no foot fractures were found except at the base of the fifth metatarsal—and all fifth metatarsal fractures were visible on properly performed ankle series 1, 2.
Proper Ankle Radiographic Protocol
Order a standard three-view ankle series that includes 1:
- Anteroposterior view
- Lateral view
- Mortise view (15-20 degree internal rotation of the leg)
Critical technical point: The ankle series must extend distally to include the base of the fifth metatarsal bone distal to the tuberosity 1. This single modification eliminates the need for separate foot films in ankle trauma.
Special Consideration for Talar Injuries
Since your patient has pain specifically over the dorsum of the talus, be alert for:
Lateral talar process fractures (snowboarder's fracture): These are missed on routine radiographs 40-50% of the time 1. Look carefully for swelling inferior to the lateral malleolus and scrutinize the lateral talar process on all views 1.
If the initial ankle radiographs are negative but clinical suspicion remains high for talar injury, consider a Broden view (supine flexed knee with 30-45 degree internal rotation) for better visualization of the lateral talar process 1.
Common Pitfall to Avoid
Do not reflexively order both ankle and foot radiographs together—this was common practice historically but represents unnecessary radiation exposure and cost 1, 2. The evidence clearly demonstrates that properly performed ankle radiographs capture all clinically significant injuries in patients with isolated ankle trauma 2.
If Initial Radiographs Are Negative
Should ankle radiographs be negative but pain persists beyond 1 week, then MRI or CT of the ankle (not foot) would be the appropriate next step to evaluate for occult fractures, osteochondral lesions, or ligamentous injuries 1.