On review, popular imaging decision aid earns 1 thumbs-up—with caveats
A new literature review and meta-analysis has shown the Ottawa Ankle Rules top 90% sensitivity, supporting the clinical decision aid’s utility for helping to rule out fractures and thus averting unnecessary X-rays.
However, with only 25% specificity, the OAR tool is prone to also running up counts of false positives, sending patients with no fractures for unneeded imaging.
The research was conducted at the University of South Australia and is described in a study published Sept. 23 by BMC Musculoskeletal Disorders [1].
Corresponding author Ryan Causby, MD, and colleagues scrutinized the OAR to update the evidence by focusing exclusively on adult patient populations—prior research included pediatrics—and on acute ankle injuries (excluding the mid-foot).
After identifying 254 relevant articles published between 1992 and 2020, the team zeroed in on 15 qualified studies spanning 13 countries.
Along with the previously mentioned figures on sensitivity and specificity, podiatrist Causby and co-authors report that a positive OAR finding ups the odds of ankle fracture 1.5 times.
However, the low specificity rates serve to warn that, while a negative OAR result “is a relatively good predictor in ruling out a fracture, it is not clinically reliable in ruling out a fracture,” the authors write.
“These findings add to a growing body of knowledge that supports the use of the OAR as a cost-effective tool to reduce unnecessary radiographic referral, when used in conjunction with the emergency clinician’s clinical reasoning and judgement,” Causby and colleagues comment. “Implementation and uptake of the tool will improve efficiency, lower medical costs and reduce waiting times for those attending health services following ankle trauma.”
As currently conceived, the Ottawa Ankle Rules hold that ankle X-rays are only indicated if the patient has either:
- pain or bone tenderness in the posterior distal tibia or tip of medial malleolus, or
- pain or bone tenderness in the posterior distal fibula or tip of lateral malleolus, or
- inability to weight bear immediately after the injury or for four steps in the emergency department.
In their discussion, Causby et al. remark that the OAR system has been used around the world for three decades. The rules “comprise a core component of guidelines incorporated in many countries,” they point out, “and have been researched “across many sites in many countries.”
And yet only 15 papers met the team’s inclusion criteria. More:
This is surprising given OAR’s utilization worldwide and the proliferation of research generally. This may be reflective of a much lower uptake than anticipated or a publication bias or other, unknown reasons. It does suggest, however, that further high-quality research in ongoing use of this tool is warranted.”
The study is available in full for free.
Dave P. has worked in journalism, marketing and public relations for more than 30 years, frequently concentrating on hospitals, healthcare technology and Catholic communications. He has also specialized in fundraising communications, ghostwriting for CEOs of local, national and global charities, nonprofits and foundations.