Investigators for the pediatric specific Low Risk Ankle Rule posited that many pediatric patients with mild ankle injury refuse to bear weight on the extremity. Also, the most common fracture among preadolescent patients is a Salter-Harris type I fracture of the distal fibular epiphysis, which the investigators felt was commonly a clinical diagnosis with little to be gained from X-ray.32 These factors would prompt clinicians using the Ottawa rule to order imaging that may not be necessary in pediatric patients.
The Low Risk Ankle Rule states that if a patient has a low-risk examination, which is defined as tenderness and swelling isolated to the distal fibula and/or adjacent lateral ligaments distal to the tibial anterior joint line, then X-rays may not be necessary to exclude a high-risk ankle injury.
Figure 4.
The anatomic landmarks are shown in Figure 4.
High-risk injuries were defined as any injury leading to an unstable ankle, and do not include avulsion, buckle, and nondisplaced Salter-Harris types I and II fractures of the distal fibula. In the validation study of nearly 600 children, the sensitivity for detecting a high risk fracture was 100% and X-rays could have been reduced in 62.8% of children with low-risk examinations compared to only 12% with the Ottawa Ankle Rule.
Comment:Although the Low Risk Ankle Rule was shown to reduce radiographic imaging by almost 63%, it omits many patients who would require splinting or subspecialty follow-up. Even the Salter-Harris type I fractures in the pediatric validation of the Ottawa rule were treated with splinting, though they were not regarded as “significant” injuries. Clinicians applying these rules, especially to a pediatric population, should have a good sense of what type of injuries these rules are designed to detect.
Conclusion
In the midst of a busy shift, clinical decision rules can help save time and expense. However, few of the rules described are meant to be applied to “all-comers,” and practitioners should be careful to not apply these rules to populations that were excluded in the validation cohorts. While clinical decision rules can help identify high-risk features, they are not a substitute for performing a thorough history and physical examination. Further studies should focus on whether these rules truly outperform unaided clinical decision-making.
Part 2 of “Playing by the Rules” will examine the use of clinician decision rules for nontraumatic conditions.
