Portable posteroanterior (PA) radiograph of the left wrist (Fig. 32A) shows a triangular lunate with abnormal overlap of the lunate and capitate (“piece of pie” sign). The middle carpal arc (distal concave curve of the scaphoid, lunate, and triquetrum) is disrupted. Subtle contour abnormality of the proximal carpal arc (proximal convex curve of the scaphoid, lunate, and triquetrum) at the scapholunate joint is also noted. The portable lateral radiograph of the wrist (Fig. 32B) shows, with the exception of the lunate, dislocation of the entire carpus dorsal to the radius; only the lunate maintains its normal relationship with the radius. PA (Fig. 32C) and lateral (Fig. 32D) radiographs of the wrist from a different patient show similar findings with additional scaphoid waist and triquetral fractures (arrows).

Lunate dislocation, perilunate dislocation, lunate fracture-dislocation, perilunate fracture-dislocation.