X-Ray Left Ankle and Foot: Evidence-Based Imaging Algorithm
Initial Clinical Decision Making
Apply the Ottawa Ankle Rules (OAR) first to determine if radiography is necessary—these rules have 99% sensitivity for detecting fractures and can safely reduce unnecessary imaging by 30-34%. 1, 2
When Radiographs ARE Indicated (Positive Ottawa Ankle Rules)
Order ankle radiographs if ANY of the following are present: 1, 2
- Bone tenderness at the posterior edge or tip of either malleolus (within 6 cm)
- Bone tenderness over the navicular bone
- Inability to bear weight immediately after injury and for four steps in the emergency department
Order foot radiographs if ANY of the following are present: 1, 2
- Bone tenderness at the base of the fifth metatarsal
- Bone tenderness over the navicular bone
- Inability to bear weight immediately after injury and for four steps
When Radiographs Are NOT Routinely Indicated (Negative Ottawa Rules)
No imaging is required when Ottawa Rules are negative in patients without exclusionary criteria—the probability of fracture is 0% (95% CI: 0-0.8%). 1, 2
Critical Exclusion Criteria (Ottawa Rules Cannot Be Applied)
Always obtain radiographs regardless of Ottawa Rules if the patient has: 1
- Peripheral neuropathy or diabetic neuropathy (cannot reliably report pain)
- Neurologic impairment affecting the lower extremity
- Intoxication or altered mental status
- Distracting painful injuries elsewhere
- Age less than 5 years
- Pregnancy
- Injury more than 10 days old
Imaging Protocol Recommendations
Standard Initial Radiographs
Ankle series: Three standard views (AP, lateral, mortise) 1
Foot series: Three standard views (AP, oblique, lateral) 1
Important Pitfall to Avoid
Do NOT routinely order both ankle AND foot radiographs together when clinical findings are limited to the ankle alone—this represents overuse, as adequately performed ankle series will detect base of fifth metatarsal fractures. 3 Studies show that when 243 patients had both ankle and foot X-rays for ankle-only trauma, all nine fifth metatarsal fractures were visible on the ankle series alone. 3
Advanced Imaging When Radiographs Are Positive
If Fracture Is Detected on Initial Radiographs
CT ankle without IV contrast is the mandatory next imaging study to fully characterize fracture extent, displacement, comminution, and intra-articular involvement for surgical planning. 1, 4
CT is particularly critical for: 1, 5
- Talar fractures (radiographs detect only 78% compared to CT; any displacement >2mm requires surgical fixation) 4, 5
- Posterior malleolar fractures (missed in 50% of cases on radiographs alone) 1
- Calcaneal fractures (radiograph sensitivity only 87%) 5
- Osteochondral lesions (to quantify cortical involvement and intra-articular bodies) 1
- Complex pilon fractures
- Suspected Lisfranc injuries (24% missed on radiographs) 5
If Radiographs Are Negative But Clinical Suspicion Remains High
MRI ankle without IV contrast is the reference standard for detecting occult fractures with bone marrow edema, ligamentous injuries, and soft tissue pathology. 1
MRI is specifically indicated for: 1
- Persistent lateral ankle pain after inversion injury (15% have ligamentous injuries without radiographic fracture)
- Suspected high-grade ligament tears (anterior talofibular, syndesmotic, deltoid ligaments)
- Athletes requiring precise grading of injuries for return-to-sport decisions
- Suspected Salter-Harris type I fractures in children
- Occult stress fractures
Special Clinical Scenarios
Suspected Lisfranc Injury
Obtain weight-bearing radiographs when possible, as non-weight-bearing films are unreliable for detecting ligamentous instability. 1 Add an AP view with 20-degree craniocaudal angulation to the standard three views. 1
Snowboarder's Fracture (Lateral Talar Process)
These fractures are overlooked 40-50% of the time on routine radiographs—pay special attention to patients with swelling inferior to the lateral malleolus. 1 Consider lateral inversion stress views if initial radiographs are negative. 1
High-Energy Trauma or Polytrauma
In neurologically impaired or polytrauma patients, consider CT as the primary imaging modality rather than radiographs, as fractures may be difficult to identify clinically. 1, 5 MDCT sensitivity is superior to radiography in high-energy mechanisms (falls from height, motor vehicle accidents). 5
Modalities That Are NOT Routinely Indicated
- Ultrasound: Only 90.9% sensitivity for fractures; reserved for focused tendon/ligament evaluation 1
- Bone scan: Only for rare polytrauma cases with multiple suspected fractures 1
- Stress radiographs: Only when clinical instability is demonstrated on physical examination 1
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