The Ottawa Ankle Rules in Asia: validating a clinical decision rule for requesting X-rays in twisting ankle and foot injuries

Abstract

This was a study to determine if the Ottawa Ankle Rules (OAR) for requesting x-ray studies in twisting ankle and foot injuries are applicable in our Asian population. Four hundred ninety-four consecutive eligible patients presenting to the emergency department with twisting injuries about the ankle were examined by emergency physicians for clinical criteria requiring ankle and foot x-ray studies according to the OAR. Four hundred eighty-eight of these patients underwent x-ray studies that were interpreted by a radiologist. The sensitivity and specificity of the OAR for predicting the presence of fracture were calculated to be 0.9 and 0.34, respectively. When the rules were modified to cast a wider screening net, sensitivity improved to 0.99. We conclude that the OAR are not applicable to our population because of inadequate sensitivity, but when modified become acceptable and can reduce the number of x-ray studies requested by 28%.

Introduction

Clinical decision rules for requesting x-ray studies in twisting ankle injuries have been described by various authors. In 1993, Stiell et al. developed and refined a set of such decision rules, the Ottawa Ankle Rules (OAR) (1), which have met with varying levels of success in validation around the world 2, 3, 4, 5, 6, 7. To our knowledge, this has not been done for an Asian population, as a check with the Medline database from the year 1995 onward shows. We wanted to find out if the OAR are applicable to our predominantly Asian patient population. Our local practice also tends to encourage the requesting of x-ray studies “to exclude fracture” in twisting ankle injuries. The potential benefit to us would thus be a decrease in the number of x-ray studies requested, shorter turnaround times, less radiation for patients, and cost reduction for the hospital.