History: 30 year old man with wrist swelling and pain.
This is a case of a perilunate dislocation. A perilunate dislocation is a carpal instability pattern that usually results from hyperdorsiflexion of the wrist. In the perilunate dislocation pattern the capitate dislocates dorsally and moves proximally and rotates the lunate in a volar direction while the radiolunate articulation is maintained.
This must be distinguished from a lunate dislocation, in which the capitate drops completely into the space occupied by the lunate and the lunate is dislocated from the radius. This classically produces what has been referred to as the “spilled tea cup” appearance of the lunate on the lateral radiograph of the wrist.