EVALUATION OF THE OTTAWA KNEE RULE IN A PEDIATRIC E. D. AND UNIVERSITY SPORTS MEDICINE CENTER

Abstract

The Ottawa Knee Rule (OKR) is a clinical decision rule to screen for the use of radiography to identify fractures in adults. It has reduced radiography and costs in emergency departments (E.D.) without missing clinically significant fractures (Stiell et al. 1997) but has not been evaluated in other settings. We prospectively evaluated the OKR for its ability to identify knee fractures and to reduce radiography in pediatric and adult patients in a university sports medicine center and a pediatric E. D. All patients with acute knee injury (≤ 7 days old) had the rule applied and underwent radiography. Exclusion criteria included: age < 5 y, multiple trauma, altered consciousness, metabolic bone disease, fever, limp without injury, pregnancy, or previous evaluation of same injury. 129 patients (mean age 17.7 ± 10.2y, range 5–73y, 70% ≤ age 17y) had radiography after application of the rule. There were 4 fractures (all pediatric) for a fracture prevalence of 3%. Sensitivity was 1.0 (95% confidence interval {0.79, 1.0}), specificity 0.42 {0.41, 0.44}, positive predictive value 0.05, negative predictive value 1.0. OKR successfully identified all patients with fractures. Low fracture prevalence limited positive predictive value, but radiography could have been reduced by 41% (53/129) with a subsequent cost saving of > $6000. We conclude that the OKR could significantly reduce knee radiography in sports medicine centers and pediatric E. D. s without missing fractures. Prospective implementation in these clinical settings will determine how cost effective these rules will be.