Sail sign (elbow)
Citation, DOI and article data
The sail sign on an elbow radiograph, also known as the anterior fat pad sign, describes the elevation of the anterior fat pad to create a silhouette similar to a billowing spinnaker sail from a boat. It indicates the presence of an elbow joint effusion.
The anterior fat pad is usually concealed within the coronoid fossa or seen paralleling the anterior humeral line. When there is a joint effusion, the anterior fat pad (which is intra-articular, but extrasynovial) becomes elevated.
Elevation of the anterior fat pad usually heralds the presence of an intra-articular fracture. In adults, this is usually a radial head fracture whereas in children, the commonest cause of a raised elbow fat pad is a supracondylar fracture.
Where a fat pad is raised and no fracture is demonstrated, an occult fracture should be suspected.
- sail sign: the raised anterior fat pad on an elbow radiograph
- thymic sail sign: normal thymus on a pediatric chest radiograph
- spinnaker-sail sign (angel wing sign): thymus outlined in pneumomediastinum
- retrocardiac sail sign: left lower lobe collapse on a chest radiograph
- laryngeal sail sign: unilateral dilated laryngeal ventricle in vocal cord paralysis
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