Can We Safely Apply the Ottawa Ankle Rules to Children?

The Ottawa Ankle Rules (OAR) were derived, refined, validated, and implemented in the early 1990s by Stiell et al.1–3 to guide the clinical assessment of patients after blunt ankle trauma. The original rules were intended to identify all clinically significant ankle and midfoot fractures, while maintaining sufficient specificity to allow a safe reduction in x-ray utilization with its attendant ionizing radiation exposure, increased health care costs, and diminished efficiency in already overcrowded emergency departments (EDs). The validated rules state that an ankle x-ray series is only indicated after an acute blunt injury when there is pain in the malleolar zone and bony tenderness to palpation over the posterior edge or tip of either the medial or lateral malleolus or if the patient is unable to bear weight both immediately and in the ED. Likewise, a foot x-ray series is indicated only when there is pain in the midfoot and bony tenderness to palpation of either the navicular or the base of the fifth metatarsal or if the patient is unable to bear weight both immediately and in the ED. The authors define weight bearing in the ED as the ability to transfer weight twice (a total of four steps), regardless of limping. Subsequent multicenter implementation of the OAR demonstrated decreases in radiography, waiting times, and costs, without an increased rate of missed fractures.4 In international surveys, large numbers of emergency physicians (EPs) report familiarity with and routine use of the OAR.5,6 While the original investigations specifically excluded patients under 18 years of age, the rules have been subsequently studied in various adult and pediatric populations. A meta-analysis of 15,581 patients (adults and children) from 27 studies demonstrated an overall sensitivity and specificity for the OAR of 97.6 and 31.5%, respectively.7 In this issue of Academic Emergency Medicine, Dowling et al.8 present a well-designed and executed meta-analysis of the Ottawa Ankle Rules for the identification of ankle and midfoot fractures in children. In a pooled analysis of 12 studies representing 3,130 children with 671 fractures, the authors report a pooled sensitivity of 98.5% (95% confidence interval = 97.3% to 99.2%) and a negative likelihood ratio of 0.11. When these diagnostic indices are applied to the average fracture prevalence among the included studies (21.4%), the authors estimate a missed fracture rate of 1.2%. Furthermore, the pooled data suggest that application of the rules in children could potentially result in a 24.8% reduction in x-ray utilization. It is important to consider the lower age range of those to whom the rules may be safely applied. As the authors point out, weight bearing is a requirement of the rule; therefore, it can only be applied to those children able to walk independently prior to the injury. A preplanned subgroup analysis of patients less than 6 years of age was not possible due to insufficient data, and thus the authors appropriately recommend caution when applying the OAR to this age group. So, what types of fractures do the OAR miss in children? Further characterization was available for 4 of the 10 missed fractures. Of these, one was a Salter-Harris (SH)-I fracture, 1 was a SH-IV fracture, and 2 were deemed “insignificant,” defined by the authors of the original study as either SH-I or avulsion fractures less than 3 mm. Of note, the latter injuries were also deemed clinically insignificant in the original work by Stiell et al., and the OAR were never intended to identify them. The issue of the clinical significance of SH-I fractures remains a source of debate, and while the authors of the present work note this fact, their final analyses and calculations included all reported fractures. Some clinicians may be understandably reluctant to rely on a clinical decision rule (CDR) that misses even a small number of pediatric ankle fractures; however, routine radiographs are likewise imperfect at diagnosing these injuries.9,10 In fact, the yield of initial x-ray studies is likely lowest in patients with a low-risk clinical examination, such as those in whom the OAR are “negative.” This is in contrast to delayed radiographs, obtained 7–10 days after the injury, which may be helpful in visualizing occult injuries by showing evidence of bone remodeling and fracture healing. While no CDR should be used indiscriminately to supplant clinical judgment, the current work provides evidence that it is reasonable to apply the OAR to help guide clinical decision-making in children 6 years or older with blunt ankle trauma and that doing so may decrease the rate of unnecessary radiographs. Certainly, it is important to involve the patient and family in the clinical decision-making process, clearly explain that a small percentage of fractures will be missed by both the OAR and initial x-rays, and reinforce the need for follow-up evaluation and consideration of delayed radiographs if symptoms persist despite conservative management. This is analogous to what many EPs currently do in cases of suspected radiographically occult fractures in children. As with all good systematic reviews, the main strengths of the present work lie in the study methodology. The authors devised a protocol that asked clinically important questions and defined their intended subgroup analyses a priori. They used a comprehensive search strategy with no language restriction. In addition to querying the large electronic databases of published studies, they examined meeting abstracts, conference proceedings, and trial registries; reviewed the references lists of identified studies; and contacted the first authors of select investigations. This search of the so-called “gray literature” yielded an additional 15 studies for review that were not identified by other means. Two reviewers independently screened all works utilizing a standardized inclusion and exclusion form, and study quality was independently assessed in a structured manner. The authors performed an appropriate statistical analysis, presented their data clearly, and were careful not to overstate their conclusions. McGinn et al.11 have published guidelines on the use of CDRs. In their work they describe four strata that illustrate the hierarchy of evidence for such rules. The current work is consistent with Level 2 evidence for the use of the OAR in children in that it presents data demonstrating accuracy of the rules across several different settings. By definition, this level of evidence heralds a rule that may be used with confidence in various settings. To achieve Level 1 evidence requires an impact analysis demonstrating that the CDR is effective in altering clinician behavior and improving patient care. Toward this end, successful and widespread implementation of the OAR in children hinges on whether clinicians will be comfortable with a CDR that misses a small number of injuries and whether the projected benefits of decreased radiation exposure and improved resource utilization can be realized without compromising patient care. Another important consideration in evaluating the impact and performance of a CDR is whether clinicians can accurately recall the elements of the rule and apply it in a consistent and reproducible fashion in their daily practice. In one survey on the use and recall of the OAR among Canadian EPs, a majority of respondents reported routine use of the rules and rated them as easy to learn and remember.6 While the survey data suggested that the majority of physicians apply the rules from memory, less than one-third demonstrated perfect recall of the specific elements of the rules. Whether these results translate into routine misapplication of the rules is uncertain, but similar findings were demonstrated in another survey on the use and spontaneous recall of other CDRs.12 Given these findings and the exponential increase in the proliferation of CDRs in recent years, this is an area richly deserving of future investigation. In summary, the OAR appear to be an excellent alternative to routine radiographs for detecting ankle and midfoot fractures in children 6 years or older after blunt trauma. Clinicians can confidently assure patients and their families that the sensitivity of this CDR is comparable to that of initial x-ray studies (which also miss a small percentage of bony injuries) and that conservative management and delayed radiographs for continued pain is a safe and effective alternative. It remains to be seen whether the rules will enjoy the same widespread acceptance for use in pediatric patients, with a resultant decrease in radiographic utilization and favorable cost–benefit profile, as they have in the adult population.

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