Sprained Ankle - 3
Important The Ottowa Ankle Rules can save time, money and radiation - learn them.
Does the patient need an X-ray ?
This question was analysed by a group of Canadian emergency physicians, who found a set of common factors which seemed to predict the presence of fracture in retrospective cases.
They then validated these rules prospectively over several thousand patients.
This provided good evidence of their robustness and generalisability.
Research design - the ideal test
The research was designed to find a rule set that maintained 100% sensitivity (picked up all significant fractures), but significantly reduced (by about 30%) the number of X-rays that were done.
The number of fractures 'missed' (0.5%) was about the same in both groups.
Why not just X-ray everyone ?
This is what used to happen, but the large number of negative X-rays done by (mainly) junior medical staff made the process expensive, time consuming, and exposed patients to unnecessary radiation.
The rules were developed to give junior doctors a safe way of saying 'No, you do not need an X-ray'.
The Ottowa Ankle Rules
The rules are best summarised in this picture.
Validity of these rules in different age groups
These rules have been extensively validated in adults (the age range in the validation trial was 16-101), but have not been validated in children. However sprained ankles are relatively uncommon in children.
A lower threshold for X-rays should exist in patients:
- who are difficult to assess reliably, e.g. language barriers.
- are more liable to fracture e.g. likely to be very osteoporitic.