This is part of a recurring series examining landmark articles in Emergency Medicine, in the style of ALiEM’s 52 Articles.
Discussing: Stiell IG, et al. Decision Rules for the Use of Radiography in Acute Ankle Injuries. JAMA 1993; 269 (9): 1127 – 1132.
X-Rays for ankle fractures? Is trouble a foot?
With a such a refined Canadian tool you can’t act like a fool.
- The Ottawa ankle rule is an excellent screening tool for patients with ankle and foot injuries. In this study, it was found to have a sensitivity of 100 percent and is therefore unlikely to miss clinically significant ankle and midfoot injuries.
- These simple rules allowed physicians to safely reduce the number of radiographs ordered in patients with ankle and foot injuries by nearly a third.
- Based on the combined 1485 patients seen in the two stages the negative likelihood ratio for a fracture is estimated to be 0 for both the ankle and foot series rules!
Acute ankle injuries are one of the most common presenting complaints seen in the Emergency Department. Ankle radiographs are typically the second most commonly performed musculoskeletal examination, after the cervical spine. It was estimated that more than 5 million ankle radiographs are ordered annually in Canada and the USA with a cost of $500 creating a massive burden on the healthcare systems. Out of all of these images, treatable fractures are present in less than 15 percent of cases.
In 1992, Ian Stiell and his colleagues derived a clinical decision tool for the use of radiography in acute ankle and foot injuries. In the original study, thirty-two clinical variables were assessed for association with fractures seen on x-ray. Using these results, a set of rules were derived to determine if imaging was necessary for patients with ankle and foot injuries who met certain criteria. The goal of the study being reviewed here was to prospectively validate and potentially refine the decision rules to have the highest sensitivity possible, 100 percent, for identifying malleoli and midfoot fractures.
The study was set up as a convenience survey and was prospectively administered in two stages: validation and refinement of the original rules, followed by validation of the refined rules in a new group of patients. For the study, injuries were subdivided into malleolar and midfoot zones. Patients who presented to the emergency department with pain or tenderness secondary to blunt ankle trauma due to any mechanism of injury were included. Patients were excluded if they were less than 18 years old, pregnant, has isolated skin injuries, were referred from outside facility with X-rays already completed, if injuries occurred more than 10 days ago, or if the patient had returned for reassessment of the injury.
Participants were evaluated by emergency medicine physicians who recorded their findings and interpretation of the decision rules on a standardized data collection sheet. All patients were then referred for radiography. Images were interpreted by radiologists who were blinded to the findings of the physician in the ED. Clinically significant fractures were defined as bone fragments greater than 3 mm in breadth, as avulsion fractures of 3 mm or less are not treated with plaster immobilization in the institutions involved in the study.
Data collected from the first stage was analyzed in order to refine the decision rules towards the objective of a sensitivity of 1.0. Each of the clinical variables were assessed for association with significant fractures in the ankle and foot radiographs. In the second stage, the sensitivity and specificity of the refined decision rules (see image above) was calculated and the accuracy and reliability of the physicians’ interpretation of the rules was determined. Continue reading