62

Lateral radiographs demonstrate dorsal displacement of the capitate (Fig. 62–1). The proximal pole of the scaphoid is rotated dorsally as the scaphoid palmar flexes (Fig. 62–2). Anteroposterior radiographs will verify the distal carpal row overlapping the proximal carpal row (Fig. 62–3). The scapholunate interval should be greater than 2 mm (Fig. 62–4).

Figure 62–1. (A). Artwork of the typical appearance of the lateral radiograph in a scapholunate ligament tear. (B). Lateral radiograph that demonstrates a dorsal periluate dislocation (note the capitate and scaphoid are dorsal to the lunate with the lunate displaced volarly).

PEARLS

• An acute perilunate dislocation should be treated by operative intervention.
  
• Posttraumatic arthritis has been reported as high as 56% in surgically treated perilunate dislocations.
  
• Intraoperative radiographs facilitate avoiding poor reductions at surgery.
  
• Patient expectations must be discussed, including loss of use and permanent stiffness after a perilunate dislocation.

PITFALLS

• Delayed treatment may be due to missed diagnosis and will lead to adverse outcomes.
  
• Reduction of the joint surfaces is important to allow for normal wear of the cartilage.
  
• Scaphoid fractures associated with a perilunate dislocation must be treated to avoid a possible complication of nonunion.

Figure 62–2. (A). Artwork that demonstrates the normal colinearity between the radius, lunate, and capitate. (B). In a scapholunate dissociation the scaphoid will palmar flex and the colinear relationship will be lost.

Perilunate and lunate dislocations often result from a fall on an outstretched hand (Fig. 62–5

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