Standard Ankle X-Ray Protocol
A standard ankle X-ray consists of 3 views: anteroposterior (AP), lateral, and mortise projections. 1
The Three-View Standard
The ACR Appropriateness Criteria explicitly references "traditional three-view radiographs" as the standard imaging protocol for ankle trauma evaluation. 1 While the guidelines discuss various specialized views for specific clinical scenarios, the baseline expectation is a three-view series. 1
Evidence Supporting Three Views vs. Two Views
The three-view combination detects significantly more fractures than two-view combinations, with a statistically significant cost in diagnostic accuracy when eliminating either the AP or mortise view. 2
Key Research Findings:
Fracture detection: Reducing from three to two views results in a small but statistically significant decrease in fracture detection of the ankle and foot. 2
Pediatric population: In skeletally immature patients, two-view protocols (particularly mortise/lateral) showed statistically significant decreases in both accuracy and sensitivity compared to the standard three views. 3
Classification reliability: While fracture classification systems (Lauge-Hansen and Danis-Weber) can be applied with similar reliability using two views versus three, this addresses classification of known fractures, not initial fracture detection. 4
Missed pathologies: Approximately 40% of pathologies may be overlooked with standard X-ray evaluation alone (though this study compared X-ray to CT, not comparing view numbers). 5
Clinical Context
The mortise view is particularly critical because it provides optimal visualization of the ankle mortise joint space and syndesmosis, which cannot be adequately assessed on AP or lateral views alone. 1 The ACR guidelines reference the importance of assessing the medial clear space (<4 mm confirms stability), which requires proper mortise visualization. 1
Common Pitfall
Do not order only "ankle films" without specifying three views, as some facilities may default to two views to reduce radiation exposure and cost. 6 While two-view protocols (AP/lateral or mortise/lateral) have been studied for cost and radiation reduction, they compromise diagnostic sensitivity. 2, 3