Prospective evaluation of the Ottawa Ankle Rules in a university sports medicine center. With a modification to increase specificity for identifying malleolar fractures.

In a sports medicine center, we prospectively evaluated the Ottawa Ankle Rules over 1 year for their ability to identify clinically significant ankle and midfoot fractures and to reduce the need for radiography. We also developed a modification to improve specificity for malleolar fracture identification. Patients with acute ankle injuries (< or = 10 days old) had the rules applied and then had radiographs taken. Sensitivity, specificity, and the potential reduction in the use of radiography were calculated for the Ottawa Ankle Rules in 132 patients and for the new "Buffalo" rule in 78 of these patients. There were 11 clinically significant fractures (fracture rate, 8.3% per year). In these 132 patients, the Ottawa Ankle Rules would have reduced the need for radiography by 34%, without any fractures being missed (sensitivity 100%, specificity 37%). In 78 patients, the specificity for malleolar fracture for the new rule was significantly greater than that of the Ottawa Ankle Rules malleolar rule (59% versus 42%), sensitivity remained 100%, and the potential reduction in the need for radiography (54%) was significantly greater. The Ottawa Ankle Rules could significantly reduce the need for radiography in patients with acute ankle and midfoot injuries in this setting without missing clinically significant fractures. The Buffalo modification could improve specificity for malleolar fractures without sacrificing sensitivity and could significantly reduce the need for radiography.