There are several decision rules for ankle injury X-Rays in children. Ankle fractures occur most commonly in 10-15 year olds, and usually result from an inversion injury mechanism. Sprains are far more common and usually involve the anterior talofibular ligament. Let’s briefly review some of the existing rules that we use to (hopefully) help us order fewer ankle X-Rays.
Ottawa Ankle Rules (in children)
The original ankle rules do apply to skeletally immature children under 16. The rules consist of the following criteria:
- Pain/tenderness in the malleolar zone AND
- Tenderness along the the distal 6 cm of the posterior edge of the medial malleolus OR
- Tenderness along the the distal 6 cm of the posterior edge of the lateral malleolus OR
- Inability to bear weight both immediately and in the emergency department (for four steps)
If a child meets these criteria, X-Ray is recommended to rule out a significant fracture. If the child does not meet either of these criteria, imaging is generally not necessary. The sensitivity of this rule is in the high 90%s but the specificity is much lower (low 20%s).
The low-risk ankle rules
Developed in a pediatric population and specify the following criteria
- The injury is acute (<3 days old)
- The child is not at risk for pathological fractures (eg, osteogenesis imperfecta or known focal bone lesion such as an osteoid osteoma)
- The child has no congenital anomaly of the feet or ankles
- The child can reliably express pain or tenderness
- Physical examination demonstrates tenderness or swelling confined to the distal fibula and/or adjacent lateral ligaments distal to the anterior tibial joint line
- No gross deformity, neurovascular compromise, or other serious and potentially distracting injury are present
- Tenderness and/or swelling isolated to the distal fibula
- Tenderness adjacent to lateral ligaments distal to the tibial joint line
This rule allows low-risk fractures including avulsion, buckle, and nondisplaced Salter-Harris I and II fractures of the distal fibula to forgo imaging. These low-risk fractures have excellent outcomes with nonoperative management and splinting alone – so not getting the X-Ray is (actually) okay, but admittedly this is a tough sell to parents. The sensitivity of the initial study was nigh on 100%.
Malleolar zone algorithm
This one’s goal is to maximize the sensitivity for identifying children with significant fractures and came from a prospective study of children with ankle and mid foot injuries in a single tertiary center. There is low risk of an ankle fracture if:
- There is no bone tenderness at either malleolus or just proximal to the fibular malleolus OR
- They are able to walk 4 steps in the ED and have no swelling at either malleolus, even if there is bone tenderness
The initial study’s sensitivity is 100% and specificity 19.1%. This has not been validated yet.
How do they stack up?
Interestingly, the Low Risk Ankle Rules ask you to forgo X-Rays even if there might be a fracture because the risk of just splinting is so low that the kid will do well whether you know there is a fracture or not. One could see this being applied differently in an outpatient office without easy access to X-rays versus an ED or Urgent care where X-Rays are easy to get. However, the cumulative cost (for individuals and for us all) is important to consider. In general the Ottawa Ankle Rules are the most sensitive (rule out) for clinically important fractures, whereas the Low Risk Ankle Rules are the most specific (rule in) for clinically important fractures. Deploying the Low Risk Ankle Rules also allow you to reduce the ordering of X-Rays the most. A comparison of the test characteristics from a 2009 validation study by Gravel et al is as follows:
Radiography was performed for 245 of the 272 participants. All patients with no radiograph were reached by telephone. Forty-seven participants had a clinically important fracture. The sensitivity and specificity of the rules were 1.00 (95% confidence interval [CI] 0.93 to 1.00) and 0.27 (95% CI 0.21 to 0.33) for the Ottawa Ankle Rules, 0.87 (95% CI 0.75 to 0.94) and 0.54 (95% CI 0.47 to 0.60) for the Low-Risk Exam, and 0.94 (95% CI 0.83 to 0.98) and 0.24 (95% CI 0.19 to 0.31) for the Malleolar Zone Algorithm.
How to I talk to parents if you decide not to order X-Rays?
Regardless of which rule you use it’s a good idea to have a good discussion with families. Here is an example of how I might do this:
Your child has an ankle injury that typically heals very well with the immobilization that we are providing, limits on weight-bearing until the pain improves, and treatment of the pain and swelling by using ice, compression, elevation and ibuprofen as needed. At this time, X-Ray would not truly help us in deciding the best way to treat your child’s ankle injury. It is highly likely that they have a sprain or, in the worst case, a very tiny fracture to the fibula, a bone on the outside of the ankle. Even if there’s a small fracture, this heals very well with the treatment we are recommending and children don’t need further X-Rays, or follow-up from an orthopedic specialist. However, if you find that your child’s injury is not feeling better within a week, please follow up with your doctor. X-Rays may be necessary at that time.
Brad Sobolewski, MD, MEd – talking to parents about not getting an X-Ray for ankle injuries
References
Boutis K, Grootendorst P, Willan A, Plint AC, Babyn P, Brison RJ, Sayal A, Parker M, Mamen N, Schuh S, Grimshaw J, Johnson D, Narayanan U. Effect of the Low Risk Ankle Rule on the frequency of radiography in children with ankle injuries. CMAJ. 2013 Oct 15;185(15):E731-8. PMID: 23939215.
Johnson, S. T., & Lynch, M. (2018). Acute Ankle Injuries. Pediatrics in Review, 39(9), 453-465. doi: 10.1542/pir.2017-0116
Stiell, I. G., Wells, G. A., Hoag, R. H., Sivilotti, M. L., Cacciotti, T., & Verbeek, P. R. (1995). Implementation of the Ottawa ankle rules. Journal of the American Medical Association, 273(16), 1281-1284. doi: 10.1001/jama.1995.03520400025030
Hess, E. P., Homme, J. H., Kharbanda, A. B., & Mayo-Smith, W. W. (2013). Low risk of ankle fractures in children with isolated ankle bruises. Archives of Pediatrics and Adolescent Medicine, 167(6), 539-543. doi: 10.1001/archpediatrics.2013.236
