A 30-year-old man falls on an outstretched hand and presents with severe wrist pain and median nerve paraesthesia. Lateral radiograph shows the capitate sitting out of the lunate fossa while the lunate remains aligned with the radius, and the lunate appears triangular on the anteroposterior view. What is the diagnosis?

• A Perilunate dislocation
• B Transscaphoid perilunate fracture dislocation
• C Scapholunate dissociation
• D Lunate dislocation ✓

Explanation

In lunate dislocation the lunate is extruded, typically volarly into the carpal tunnel compressing the median nerve, while the capitate stays colinear with the radius. On the lateral film the lunate looks like a tipped cup, the spilled teacup sign, and appears triangular on the anteroposterior view. In perilunate dislocation the opposite holds: the lunate remains aligned with the radius and the capitate displaces dorsally.

Reference: Miller's Review of Orthopaedics, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.