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The Ottawa ankle rules (OAR) are a set of guidelines to help the physician as to decision making regarding need for x ray examination after ankle and mid-foot injury. A previous best evidence topic report examined whether these rules could be applied to children.1 At that time there was insufficient evidence to make a determination. This appraisal updates that topic.
Structured clinical question
In a child with history of ankle injury [patient] are the Ottawa ankle rules [test] reliable in eliminating the need for x ray examination in some patients without the risk of missing fractures [outcome]?
Search strategy and outcome
Cochrane—two trials that involved children were found in Central.
PubMed—(Clinical Queries) Ottawa ankle rules AND child.
One systematic review was found that included 27 studies, six of which were pertaining to children, two of which were the trials found in Central. Eight total prospective studies were found; six were those included in the systematic review plus two subsequent publications.
Eight relevant papers found. See table 1.
The physical examination findings for the Ottawa ankle rules are as follows: tenderness over the lateral malleoli, inability to bear weight, and tenderness over the posterior distal tibia and fibula. A patient that exhibits one of these characteristics is deemed in need of x ray examination. The OAR have been validated for use as a screening tool in adults who have sustained ankle or mid-foot injuries.1 Three considerations render the applicability of OAR to children less certain. Children may not be as reliable with regard to verbal history. Because Salter-Harris type I fractures, defined as a separation of bone >3 mm through the physis, more commonly accompany trauma in infants and children, point tenderness will generally be present. Further, a child must be able to walk freely prior to injury, in order for the OAR to be applied. Thus the OAR criteria will be positive and unnecessary radiographs may be obtained for an injury that will ultimately be treated the same as a sprain.
We computed a random effects meta-analysis model directly on the proportions with weights based on the variance of a binomial distribution. We used a pooled estimate of sensitivity/specificity, instead of individual sensitivities/specificities for each study. Statistical calculations were made using the meta library, version 0.5, with the R software package, version 2.01 (R Foundation for Statistical Computing, Vienna, Austria).
Formulas from Evidence-Based Medicine text by Sackett were used to calculate prevalence, likelihood ratios, post-test odds, PPV, and NPV.
The overall sensitivity was calculated to be 97% with confidence limits of 93%–100%. The overall specificity was calculated to be 29% with confidence limits of 18%–40%.
An estimated prevalence of 12% was calculated based on the number of fractures in the studies divided by the total number of patients. The prevalence and likelihood ratio were then used to derive the PPV and NPV.
There was one article4 that showed five patients with negative results when applying the rules who ultimately had a fracture. All other articles had zero or 1 in this category. Using the Ottawa ankle rules has relevance in the clinical setting; as it is a tool that can be used to aid the clinician in decreasing unnecessary x ray examinations. This may very well decrease patient care costs, as well as patient time spent in the acute care setting.
A small percentage of patients that are excluded from receiving x ray evaluation based on the Ottawa ankle rules, will actually have a fracture. It is a low percentage of patients at 1.4%. These missed fractures will often be of little clinical significance, as many of them will represent the Salter-Harris I classification. While there may be no long term consequences to these missed fractures, each clinician must decide their comfort level in applying the rules to individual patients.
CLINICAL BOTTOM LINE
These rules are meant to be applied to those patients who have the ability to walk prior to their injury, and can localise pain with verbal communication. (grade A)
Negative results when applying the rules should help the physician to decrease x ray usage without an increase in missed fractures. (grade A)
For every 1000 patients that exhibit negative Ottawa ankle rules, 14 will actually have fractures. (grade A)
Edited by Bob Phillips