Imaging Studies
Plain x-rays of the wrist, both anteroposterior (AP) and lateral views, are essential to diagnose wrist dislocations (as well as other carpal instabilities).
On an AP view (shown below), 2 arcs should be identified. The first arc consists of the radiocarpal row, which should be smooth and continuous. Disruption is suggestive of a lunate dislocation.
The second arc consists of the midcarpal row, which also should be smooth and continuous. Disruption of this arc is suggestive of a perilunate dislocation.
The appearance of the lunate is important on the AP view. Normally, the lunate is quadrangular. With lunate dislocations, it becomes triangular. This may be an additional clue to dislocation.
On the lateral view (shown below), visualize the column, which consists of the radius, lunate, and capitate. The lunate should lie within the radius cup and the capitate should rest within the lunate cup. Loss of this normal column implies lunate or perilunate dislocation.
Dislocations, wrist. Lateral view of a lunate dislocation, with the classic teacup sign.
Stress x-rays of the wrist may be necessary to demonstrate intercarpal ligamentous instability when no evidence of wrist dislocation is apparent on plain films.
Stress x-rays obtained with radial and ulnar deviation of the hand may demonstrate scapholunate dissociation.
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Dislocations, wrist. Lateral view of a lunate dislocation, with the classic teacup sign.
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Dislocations, wrist. Anteroposterior (AP) view of a lunate dislocation.
