A study to develop clinical decision rules for the use of radiography in acute ankle injuries.

STUDY OBJECTIVE: To develop decision rules that will predict fractures in patients with ankle injuries, thereby assisting clinicians in being more selective in their use of radiography.

DESIGN: Prospective survey of emergency department patients over a five-month period.

SETTING: Two university hospital EDs.

PARTICIPANTS: One hundred fifty-five adults in a pilot stage and 750 in the main study; all presented with acute blunt ankle injuries.

INTERVENTIONS: Thirty-two standardized clinical variables were assessed and recorded on data sheets by staff emergency physicians before radiography.

MEASUREMENTS: Variables were assessed for reliability by the kappa coefficient and for association with significant fracture on both ankle and foot radiographic series by univariate analysis. The data then were analyzed by logistic regression and recursive partitioning techniques to develop decision rules for predicting fractures in each radiographic series.

MAIN RESULTS: All 70 significant malleolar fractures found in the 689 ankle radiographic series performed were identified among people who had pain near the malleoli and were age 55 years or more, had localized bone tenderness of the posterior edge or tip of either malleolus, or were unable to bear weight both immediately after the injury and in the ED. This rule was 100% sensitive and 40.1% specific for detecting malleolar fractures and would allow a reduction of 36.0% of ankle radiographic series ordered. Similarly, all 32 significant midfoot fractures on the 230 foot radiographic series performed were found among patients with pain in the midfoot and bone tenderness at the base of the fifth metatarsal, the cuboid, or the navicular.

CONCLUSION: Highly sensitive decision rules have been developed and will now be validated; these may permit clinicians to confidently reduce the number of radiographs ordered in patients with ankle injuries.