Ottawa Ankle Rules accurately assess injuries and reduce reliance on radiographs

In the United States, most ankle injuries are evaluated radiographically, ^1,2 even though only about 15% are found to involve fractures. ³ An estimated 6 million ankle radiographs are performed annually in the US and Canada, costing approximately $300 million dollars (US). The Ottawa Ankle Rules can significantly decrease the number of unnecessary ankle radiographs.

The rules are not a substitute for sound clinical judgment, but augment findings in the history and physical examination to help the clinician determine the appropriateness of ankle films. If the rules are met and radiographs are avoided, it is unlikely, especially with good communication and follow-up, that a patient will turn out to have a significant fracture. Moreover, discussing physical examination findings and the reasons for doing or not doing radiographs will enhance patient-physician communication. As we report in this article, patients’ satisfaction with care seems not to depend on whether x-ray films are ordered.

Applying the Ottawa Ankle Rules

To address the problem of low positive predictive value of ankle radiographs, Stiell and colleagues⁴ at the University of Ottawa and the Ontario Health Ministry developed a set of clinical parameters in the early 1990s to evaluate the need for ankle and midfoot radiographs. Their criteria were based on a multivariable data analysis involving a large number of clinical variables associated with ankle injuries. The resulting rules (Figure) have been shown to decrease the need for films by about 30%.⁴ If a patient does not exhibit any of the criteria, radiographs of the foot or ankle are not needed after trauma (strength of recommendation [SOR]: A).

FIGURE
Ottawa Ankle Rules for determining the need for radiographs Indications for ankle radiographs

Validation of the rules in different settings

A number of studies have tested the negative predictive value of the Ottawa Ankle Rules. A high negative predictive value implies that if the rules are followed, a fracture will not be missed. Most of these studies were conducted in emergency medicine, sports medicine, and orthopedic settings. In a follow-up study, Stiell and colleagues found a sensitivity of 1.0 (95% confidence interval, 0.95–1.0) for ankle fractures and mid-foot fractures. A positive result is a clinically significant fracture, described as one greater than 3 mm. Such avulsion type injuries are treated clinically like a sprain. In the Stiell study, all films were evaluated by radiologists. The authors estimated a decrease in ankle radiographs by 28% if the rules were followed.⁴

Emergency medicine. The sensitivity in this setting was also found to be 1.0, with a negative predictive value of 1.0 when used by physicians. This means that no fractures would be missed by using the rules. Specificity was only 0.19.³ In a multicenter Canadian trial, the results were similar. Over 12,000 adults were evaluated with the ankle rule at 8 teaching and community hospital emergency departments. This study found a significant decrease in the number of ankle radiographs ordered without an increase in the rate of fractures missed.⁵

Orthopedic surgery. In a study involving 153 military cadets at West Point, orthopedic surgeons also showed the sensitivity of these rules was 1.0, with no false negatives. The investigators estimated they could safely forego 40% of all ankle films and 79% of all midfoot films. In the 4 years of training at the Military Academy, an estimated 33% of all cadets suffer an ankle sprain, which speaks to the prevalence of this condition among young, active persons.⁴

Sports medicine. A prospective study in a university sports medicine clinic validated the use of the ankle rules in a population of 94 athletes. The investigators found a sensitivity of 1.0 for both ankle and midfoot injuries, and a reduction by 34% in the number of films ordered.⁷ In that study the authors comment on the value of these rules in the sports medicine venue, where the rate of ankle and midfoot fractures is low (less than 3%, as opposed to up to 20% in the emergency setting).⁸

Family medicine. Little research in family medicine discusses office use of the Ottawa Ankle Rules, but there is a need for a set of evidence-based protocols in evaluating acute ankle injuries. Before establishment of the ankle rules, family physicians used the clinical findings of (1) absence of tenderness on the dorsum of the foot, (2) lack of impaired weight bearing, (3) recentness of injury (more than 12 hours earlier), and (4) absence of additional injuries. Each of these findings had a negative predictive value of least 94%. While family physician researchers involved in one study did not establish a set of decision “rules,” they estimated that using these criteria could reduce unnecessary films by about 30%.⁹