Fracture of the Radial Head with Effusion on Plain Films

Findings
-Frontal view: There is a subtle vertical fracture through the radial head.
-Lateral view: The anterior fat pad is displaced anteriorly. The posterior fat pad is visible. These indicate a joint effusion.

Discussion
The anterior fat pad is normally visualized hugging the anterior cortex of the distal humerus. The posterior fat pad is not seen on normal views. Anterior displacement of the anterior fat pad and visualization of the posterior fat pad are compatible with a joint effusion. Radial head fractures may be extremely difficult to detect on plain film. In the setting of acute trauma, if an elbow joint effusion is present, the presumption should be that a radial head fracture is present, even if the fracture line is not visible.


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