When should radiographs be obtained in patients with an ankle or foot injury?
The Ottawa Ankle and Foot Rules1 are validated clinical decision rules. The process by which the Ottawa rules were developed and validated serves as a model for researchers in developing decision support tools for other clinical problems.1 Use of these rules can save time and money by helping physicians and their patients avoid unnecessary radiographs of the ankle or foot.
The Ottawa rules have a parallel structure. Each begins with a question to assess the site of the patient’s pain followed by an evaluation of function (based on the ability to bear weight for at least four steps immediately after the injury and again in the emergency department), and a focused physical assessment for the presence of localized bone tenderness. Radiographs should be obtained in patients who have pain in the relevant site accompanied by inability to walk four steps or bone tenderness as described above.
How accurate are the Ottawa rules for ankle and foot injuries? A recent meta-analysis2 identified 32 validation studies (27 were included in the analysis) involving 15,581 adult patients. With use of the Ottawa rules, the probability of a false negative (presence of fracture but no recommendation for radiographs) was extremely low (0.3 percent). The rules also have been validated in children. In a study3 of 670 children who presented with acute ankle injury, the Ottawa rules were 100 percent sensitive for fracture (no false negatives).
One drawback to the Ottawa rules is the fairly low specificity, which generally is around 30 to 40 percent.2,3 Consequently, radiographs will be recommended for many patients who do not have a fracture. Although not ideal, the rules are still considerably more selective than the typical practice of obtaining radiographs in every patient with acute ankle or foot pain after an injury.
All validation studies on the Ottawa rules for ankle and foot injuries have been conducted in emergency departments. Therefore, there has been some question about whether these rules can be used in the outpatient setting. One small study4 examined the performance of family physicians working part-time in a community hospital emergency department and found good sensitivity (97 percent) for use of the Ottawa rules by these physicians. With proper training and use of a decision support tool ( see accompanying patient encounter form), family physicians can achieve similar sensitivity results in the outpatient setting.
Applying the Evidence
A 24-year-old man presents with a twisted ankle that occurred while he was playing basketball. He cannot recall if he everted or inverted his ankle. He was able to bear weight in the gym and limped while bearing weight as he walked to his friend’s car. He ambulates with difficulty but is able to bear weight in the physician’s office as he walks to the examination room. On examination, he complains of pain in the ankle and has tenderness to percussion of the lateral malleolus. Does he need a radiograph of the ankle?
Answer: Because the patient has ankle pain and tenderness to percussion of a malleolus, a radiograph should be obtained even though the patient is able to bear weight.