Sonographic detection of radiographically occult fractures in paediatric ankle injuries

Background: In some paediatric ankle injuries, the clinical picture is suggestive of a fracture despite negative three-view radiographs. Objective: To determine the effectiveness of high-resolution US to differentiate radiographically occult fractures from sprains. Materials and methods: During a 12-month period, children aged 5–13 years who had sustained an acute ankle injury suspicious of a fracture on clinical examination, but with negative radiography, were referred for high-resolution US. Follow-up radiographs were obtained after 2–3 weeks. Results: A total of 20 children were examined. In 13, US did not reveal a fracture; small fractures were detected in 7. All patients with negative US studies had negative follow-up radiographs. In six patients with positive US the follow-up radiographs demonstrated a periosteal reaction. In one child in whom a fracture line identified by US was in the depth of the lateral malleolus, the follow-up radiograph demonstrated an area of increased bone density. Conclusions: US is effective for the detection of radiographically silent fractures of the paediatric ankle. It may be used as an adjunct to radiography in clinically suspicious, but radiographically negative ankle injuries.