Podcast#3: To X-ray or not to X-ray (Ottawa Ankle Rules)
The Skeptics Guide to Emergency Medicine
Date: September 3, 2012
Title: To X-ray or not to X-ray: kids with ankle injuries, that is the question?
8 year old girl brought into ED by mother after twisting her ankle on a trampoline. She was able to walk on it but has become very swollen. The mother wants to know if she should get an xray to see if her daughter broke the ankle.
The Ottawa Ankle Rules (OAR):
These were developed by Dr. Ian Stiell. He is one of the most famous Canadian emergency physicians.
The OAR represent one of the best known clinical decision instruments. The rule says xrays are only required if the patient is tender:
- distal 6cm posterior edge of the tibia to the tip of the medial malleolus
- distal 6cm posterior edge of the fibula to the tip of the lateral malleolus
- base of the 5th metatarsal
- navicular bone of the mid foot
- or patient unable to weight bear immediately in the ED for 4 steps
(Does not apply to pregnant, drunk or head injured patients)
Dr. Stiell’s article on the OAR was published in the Ann Emerg Med 1992. There were 150 patients in the pilot stage and 750 in the main study. It showed the OAR was 100% sensitive and 40% specific. So it picked up all of the true positives or fractures. Applying the OAR would have decreased xrays by over one-third.
Can the Ottawa ankle rules safely exclude ankle and foot fractures in children?
Dowling et al. Accuracy of Ottawa Ankle Rules to Exclude Fractures of the Ankle and Midfoot in Children: A Meta-analysis Acad Emerg Med. 2009 Apr;16(4):277-87. Epub 2009 Feb 2. PMID: 19187397
3,130 Children ≤18 yo presenting to the ED with blunt ankle and/or midfoot injury. The
prevalence of fracture in this group was 21.4%.
Application of the Ottawa Ankle Rule.
Any fracture of the ankle or midfoot using an x-ray or a proxy measure (phone follow up) as the criterion standard.
Study Author Conclusions:
“The OAR appear to be a reliable tool to exclude fractures in children greater than 5 years of age presenting with ankle and/or midfoot injuries. Employing the OAR would significantly decrease x-ray use with a low likelihood of missing a fracture.”
The OAR have been well validated in the adult population but its use in children has remained unclear. Children ose special challenges in the application of this clinical decision instrument due to various age related issues (ability to ambulate, difficulty in assessing pain, presence of growth plates). The authors of the SR rigorously test this decision instrument in children and appropriately conclude that it can be safely applied in children aged five and older. Only 10 fractures were missed in the pooled analysis of 3,130 children. 4 of these 10 were described of which 2 were deemed insignificant (SH-I or avulsion fracture <3mm). If these were excluded, the decision instrument would have even better performance characteristics than the authors’ conservative measures.
The BEEM Bottom Line:
Application of the OAR in children 5 and older can be safely used to guide x-ray utilization.