Radiography in acute ankle injuries: The Ottawa Ankle Rules versus local diagnostic decision rules

Abstract

Study Objective: We validate the Ottawa Ankle Rules and 2 Dutch ankle rules in distinguishing clinically significant fractures from insignificant fractures and other injuries in patients with a painful ankle presenting to the emergency department. Methods: This prospective comparison of 3 ankle rules was conducted in the ED of a 580-bed community teaching hospital in Amsterdam from January 1998 to April 1999. Participants included 647 consecutive patients aged 18 years or older presenting with a painful ankle after trauma. All physicians received extensive and pictorial training on how to correctly score the respective items of the rules. The physician on call recorded these items derived from history and physical examination on a standardized data sheet. All patients subsequently underwent standard radiographic assessment. A radiologist and a trauma surgeon evaluated the radiographs blinded from the results of the data sheet form and the treatment given. The diagnostic performance of the 3 rules was measured in terms of sensitivity, specificity, and the reduction of radiographs. Receiver operating characteristic (ROC) curves were constructed, and the area under the ROC curves was calculated and compared. Results: Seventy-four fractures were seen, of which 41 were clinically significant. The Ottawa Ankle Rules had a sensitivity of 98% for identifying clinically significant fractures; the local rules scored 88% and 59%, respectively. The potential savings in radiographs for the 3 decision rules were 24%, 54%, and 82%, respectively. The area under the ROC curve was better for both the local rules (0.84 and 0.83) compared with the Ottawa Ankle Rules (0.76). Conclusion: Because the identification of all relevant fractures is more important than a reduction in radiographs, the higher sensitivity of the Ottawa Ankle Rules makes these most suitable for implementation in The Netherlands. [Pijnenburg ACM, Glas AS, de Roos MAJ, Bogaard K, Lijmer JG, Bossuyt PMM, Butzelaar RMJM, Keeman JN. Radiography in acute ankle injuries: the Ottawa Ankle Rules versus local diagnostic decision rules. Ann Emerg Med. June 2002;39:599-604.]

Introduction

Ankle traumas are among the most common injuries of patients seen in emergency departments. They involve about 25% of all injuries of the musculoskeletal system.1, 2 In the United States, approximately 23,000 people present to the ED with an injury each day. In The Netherlands, this number is 1,200.3, 4 Patients with ankle injury constitute approximately 5% of all patients who visit EDs.⁵ Fewer than 15% of these patients have clinically significant fractures.⁶ To prevent unnecessary radiographic examination in patients with low risk of fracture, diagnostic decision rules have been developed to assist clinicians in deciding when radiographic evaluation of the injured extremity is necessary. The Ottawa Ankle Rules (Figure 1) are the best known of these decision rules.⁷

Previous studies have demonstrated good results of the application of the Ottawa Ankle Rules.8, 9

Transportability of a decision rule is the ability to produce accurate predictions among patients drawn from different but related populations.¹⁰ There is some concern that, in general, decision rules do not transport easily between countries and settings.10, 11 Newly developed rules may be better suited to local circumstances. In The Netherlands, the 2 rules that are currently used have been developed in Leiden¹² and Utrecht,¹³ both university clinics. In this prospective, blinded, comparative study, we evaluated the validation and accuracy of the Ottawa Ankle Rules. We also performed a direct comparison between the Ottawa Ankle Rules, which were developed in a Canadian population, and the 2 local decision rules in patients from a community teaching hospital.