“Low risk ankle rule” rules

Using the Low Risk Ankle Rule in an emergency setting effectively reduces the number of unnecessary radiographs performed on children presenting with ankle injuries without increasing the number of missed clinically important fractures, increasing length of stay, increasing the number of follow-up radiographs, or negatively affecting patient or physician satisfaction, according to a recent study.

The Low Risk Ankle Rule states that if a child on examination has tenderness and swelling that is isolated to the distal fibula and/or adjacent lateral ligaments distal to the tibial anterior joint line, then ankle radiography is probably not necessary to rule out a high-risk injury.

High-risk injuries include any fracture of the foot, distal tibia, and fibula proximal to the distal physis; tibiofibular syndesmosis injury; and ankle dislocations. Low-risk ankle injuries include lateral ankle sprains; nondisplaced Salter-Harris types I and II fractures of the distal fibula; and avulsion fractures of the distal fibula or lateral talus.

Researches conducted an 18-month, 3-phase study at 6 Canadian emergency departments. The study involved over 2,100 children between the ages of 3 and 16 years.

The investigators found that implementing the rule reduced the frequency of pediatric ankle radiography by almost 22%. In addition, they calculated a sensitivity of 98% and a specificity of about 50%.

If the physicians in the study had fully complied with the rule, half of the radiographs performed would have been avoided. Reasons provided for not adhering to the rule included fear of missing a significant fracture (31.3%); preferring the Ottawa Ankle Rules (13.8%); the family wanted a radiograph (10.0%); the patient was difficult to examine (7.5%); and no reason provided (37.5%). 

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