Ankle radiograph utilization after learning a decision rule: a 12-month follow-up

To test whether the reduction in ankle radiograph ordering was sustained during a 12-month period after a formal trial to introduce the Ottawa ankle rules.

A before-after clinical trial of ankle radiograph ordering practice was performed in a university-based ED. All 1,884 (947 "during intervention," 937 "postintervention") adults seen with acute ankle injuries during 2 12-month trial periods were evaluated. The behavioral intervention was the teaching of the Ottawa ankle rules and feedback of compliance with the rules during the intervention period. No further education about the ankle rules or feedback regarding compliance occurred during the postintervention year. Physicians were unaware of any postintervention surveillance. The primary outcome was the proportion of eligible patients referred for an ankle radiograph during the intervention and postintervention periods.

During the intervention period (January 1-December 31, 1993), the proportion of patients who received an ankle radiograph [609 x-rayed of 947 patients seen (64.3%; 95% CI 61.2-67.4%)] did not differ from the proportion who received an x-ray in the postintervention period (January 1-December 31, 1994) [583 x-rayed of 937 patients seen (62.2%; 95% CI 59.1-65.3%), p = 0.65, power > 0.80 to detect a 10% increase in the radiograph ordering rate]. There was also no difference in the radiograph ordering rate in the first 3 months of the postintervention period compared with the last 3 months of the postintervention period (68.8% vs 64.7%, respectively, p > 0.30).

Compliance with the Ottawa ankle rules was sustained during a 12-month postintervention surveillance period when physicians did not know they were being observed. Physicians will continue to use a simple clinical guideline once it has been learned.