A prospective study of modified Ottawa ankle rules in a military population. Interobserver agreement between physical therapists and orthopaedic surgeons.

To determine the necessity of ankle and foot radiographs, we used modified Ottawa Ankle Rules to evaluate all cadets seen with an acute ankle or midfoot injury at the United States Military Academy. This scoring system determines the need for radiographs. Each patient was independently examined and the decision rules were applied by a physical therapist and an orthopaedic surgeon. Ankle and foot radiographs were obtained for all subjects. Sensitivity, specificity, and the positive predictive value were calculated in 153 patients. There were six clinically significant ankle fractures and three midfoot fractures, for a total incidence of 5.8%. For physical therapists, the sensitivity was 100%, the specificity for ankle injuries was 40%, and the specificity for foot injuries was 79%. For orthopaedic surgeons, the sensitivity was also 100%, the specificity for ankle injuries was 46%, and the specificity for foot injuries was 79%. Interobserver agreement between the orthopaedic surgeons and physical therapists regarding the overall decision to obtain radiographs was high, with a kappa coefficient value of 0.82 for ankle injuries and 0.88 for foot injuries. There were no false-negative results. Use of the modified Ottawa Ankle Rules would have reduced the necessity for ankle and foot radiographs by 46% and 79%, respectively.