Electrical worker, fall from pole
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PA view demonstrates malalignment of the lunate creating an abnormal triangular morphology superimposed on the scaphoid and capitate. The superimposition of the triangular lunate bone on the capitate is known as the piece of pie sign. There is no fracture.
Lateral view clearly demonstrates dislocated lunate, volar to the carpus.
Perilunate disruptions are sustained in backward falls onto an outstretched hand. Lunate dislocation is the most severe form (stage IV) of perilunate disruptions. There is extensive rupture of the carpal ligaments, especially the dorsal radiolunate ligament, associated with these injuries.
There is volar dislocation of the lunate relative to the radius, with 90-degrees palmar rotation.