Radial neck fracture
Radial neck fracture. Fractures of the radial head and neck are notoriously difficult to identify on radiographs, as they are often undisplaced – this case is unusual in that the fracture line is clearly visible (yellow arrow). When the fracture line is not visible, we have to rely on two additional radiographic signs, which occur because of haemorrhage into the joint. This haemarthrosis may be visible anteriorly as a triangular shaped density in front of the distal humerus, the sail sign (white arrows). Posteriorly, the haemarthrosis can displace a normally-hidden lucent fat pad away from the humerus (orange arrow).