Imaging Case of the Week 161 Answer

The elbow x-rays show a large haemarthrosis; there is elevation of both the anterior and posterior fat pads. The radiocapitellar line is disrupted as a result of radial head dislocation. There is no fracture seen in the distal humerus, radius or ulna.


Radial head dislocation AP


Radial head dislocation lateral

The radiocapitellar line is drawn through the long axis of the radial head/neck and should bisect the capitellum in both flexion and extension of the elbow. If not, suspect a radial head dislocation, which is usually treated with a closed reduction.

Isolated radial head dislocation is rare. Hence, it is important to look for associated ulnar fracture which, if present, results in a Monteggia fracture dislocation; this injury needs operative management.