From the Guidelines
According to McGee (2022), the Ottawa ankle rule is most helpful in determining who does NOT have an ankle fracture. The Ottawa ankle rule is a clinical decision tool designed to help healthcare providers identify patients who are unlikely to have a fracture, thus reducing unnecessary X-rays. The rule uses specific criteria to assess ankle injuries, including the ability to bear weight and the presence of bone tenderness in particular locations. When a patient does not meet any of these criteria, they have a very low probability of having a fracture, allowing clinicians to confidently rule out fractures without imaging. This makes the rule particularly valuable as a "rule-out" tool rather than a diagnostic tool for identifying fractures. The high sensitivity of the Ottawa ankle rule (around 95-100%) means it rarely misses actual fractures, but its specificity is lower, meaning it sometimes suggests X-rays for patients who ultimately don't have fractures 1.
The evidence from the Journal of the American College of Radiology supports the use of the Ottawa ankle rule as a tool to exclude fractures, with studies demonstrating between 92% and 99% sensitivity for detecting ankle fracture using these guidelines, with <2% of those who are negative for fracture using the OAR actually having a fracture 1. This characteristic makes it most useful for determining who does not need radiographic imaging rather than for positively identifying who has a fracture.
Some key points to consider when using the Ottawa ankle rule include:
- The rule is validated for adults and children >5 years of age 1
- The rule uses specific criteria, including the ability to bear weight and the presence of bone tenderness in particular locations 1
- The high sensitivity of the Ottawa ankle rule means it rarely misses actual fractures, but its specificity is lower, meaning it sometimes suggests X-rays for patients who ultimately don't have fractures 1
- The rule is most useful for determining who does not need radiographic imaging rather than for positively identifying who has a fracture 1
From the Research
Ottawa Ankle Rule
The Ottawa ankle rule is a clinical decision tool used to exclude ankle fractures and determine the need for radiographic imaging in patients with acute ankle injuries.
Diagnostic Accuracy
- The sensitivity of the Ottawa ankle rule for detecting fractures is high, ranging from 88% to 100% 2, 3, 4, 5.
- The specificity of the Ottawa ankle rule is lower, ranging from 0% to 45.8% 2, 3, 4, 5.
- The negative predictive value of the Ottawa ankle rule is high, indicating that a negative finding can rule out the need for radiographs 2, 3, 4, 5.
Clinical Application
- The Ottawa ankle rule can be used to reduce unnecessary radiographic referrals and decrease medical costs 6, 3.
- The rule is highly sensitive and can correctly predict the likelihood of ankle fractures when present, but lower specificity rates increase the likelihood of false positives 3.
- The Ottawa ankle rule should be safely used in emergency departments to prevent patients from unnecessary radiation exposure 5.
Answer to the Question
Based on the studies, the correct answer is: The Ottawa ankle rule is most helpful in determining who does NOT have an ankle fracture. This is because the rule has a high sensitivity and negative predictive value, making it useful for ruling out fractures in patients with acute ankle injuries 2, 3, 4, 5.