Ottawa ankle rules - meta-analysis

[ychdrpan]

BMJ 2003;326:417 ( 22 February )

Accuracy of Ottawa ankle rules to exclude fractures of the ankle and mid-foot: systematic review

Lucas M Bachmann, senior research fellow, a Esther Kolb, research fellow, Michael T Koller, research fellow, a Johann Steurer, professor, a Gerben ter Riet, clinical epidemiologist.

Horten Centre, Zurich University, Postfach Nord, CH-8091 Zurich, Switzerland,

Academic Medical Center, Department of General Practice, Meibergdreef 15, 1105 AZ Amsterdam, Netherlands

Correspondence to: L M Bachmann lucas.bachmann@evimed.ch

Objective: To summarise the evidence on accuracy of the Ottawa ankle rules, a decision aid for excluding fractures of the ankle and mid-foot.

Design: Systematic review.

Data sources: Electronic databases, reference lists of included studies, and experts.

Review methods: Data were extracted on the study population, the type of Ottawa ankle rules used, and methods.
Sensitivities, but not specificities, were pooled using the bootstrap after inspection of the receiver operating characteristics plot.
Negative likelihood ratios were pooled for several subgroups, correcting for four main methodological threats to validity.

Results: 32 studies met the inclusion criteria and 27 studies reporting on 15 581 patients were used for meta-analysis.
The pooled negative likelihood ratios for the ankle and mid-foot were 0.08 (95% confidence interval 0.03 to 0.18) and 0.08 (0.03 to 0.20), respectively.
The pooled negative likelihood ratio for both regions in children was 0.07 (0.03 to 0.18).
Applying these ratios to a 15% prevalence of fracture gave a less than 1.4% probability of actual fracture in these subgroups.

Conclusion:
Evidence supports the Ottawa ankle rules as an accurate instrument for excluding fractures of the ankle and mid-foot.
The instrument has a sensitivity of almost 100% and a modest specificity, and
its use should reduce the number of unnecessary radiographs by 30-40%.

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Acad Emerg Med. 2009 Feb 2.

Accuracy of Ottawa Ankle Rules to Exclude Fractures of the Ankle and Midfoot in Children: A Meta-analysis.

Dowling S, Spooner CH, Liang Y, Dryden DM, Friesen C, Klassen TP, Wright RB.

From the Department of Emergency Medicine, Calgary Health Region, University of Calgary (SD), Calgary, Alberta, Canada; the Alberta Research Centre for Health Evidence (CHS, YL, DMD, CF, TPK) and Pediatric Emergency (RBW), Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.

Abstract

Objectives:
The objectives were to conduct a systematic review to determine the diagnostic accuracy of the Ottawa Ankle Rules (OAR) to exclude ankle and midfoot fractures in children and the extent to which x-ray use could be reduced without missing significant fractures.

Methods:
The authors conducted comprehensive searches of electronic databases and gray literature sources.
Independent reviewers applied standard inclusion and exclusion criteria.
The criterion standard diagnostic test was an ankle and/or foot x-ray or proxy measure to ensure no missed fractures.
Standard 2 x 2 tables were constructed.

Sensitivities and specificities were pooled using an approximation of the inverse variance; 95% confidence intervals (95% CIs) were calculated using the exact method.
Likelihood ratios (LR +/-) and diagnostic odds ratios were combined under DerSimonian and Laird random effects model.

Results:
A pooled analysis of 12 studies (N = 3,130) identified 671 fractures (prevalence = 21.4%).
Ten studies reported Salter-Harris Type I (SH-I) fractures.
The pooled sensitivity was 98.5% (95% CI = 97.3 to 99.2), suggesting that the OAR can be used to rule out a fracture.
Four of 10 missed fractures were characterized: 1 SH-I, 1 SH-IV, and 2 "insignificant fractures" (either SH-I or avulsion fractures <3 mm).
The pooled estimate for rate of x-ray reduction was 24.8% (95% CI = 23.3% to 26.3%; range = 5% to 44%).

Conclusions:
The OAR appear to be a reliable tool to exclude fractures in children greater than 5 years of age presenting with ankle and midfoot injuries.
Employing the OAR would significantly decrease x-ray use with a low likelihood of missing a fracture.

ACADEMIC EMERGENCY MEDICINE 2009; 16:1-11 (c) 2009 by the Society for Academic Emergency Medicine.