Volar Dislocation of the Lunate with 270° Rotation
Updated: Jul 26, 2021
Pain and Deformity Following Wrist Trauma
This patient fell off his bicycle, landing on his hyperextended ulnar-deviated wrist. There is anterior dislocation of the lunate, and the lunate is rotated 270 degrees such that the concavity of the lunate is directed dorsally rather than distally. The lunate is also displaced inferiorly, resulting in a fracture of the anterior articular surface of the distal radius with a small fracture fragment noted anteriorly.
The lunate is the most frequently dislocated carpal bone. The most common type of dislocation is volar, rotated 90 degrees. In this case the lunate has flipped over and rotated an additional 180 degrees, for a total rotation of 270 degrees. This is a rare form of lunate dislocation, comprising less than 5% of cases. Dislocation of 270 degrees should be treated as a surgical emergency due to the risk of acute carpal tunnel syndrome, which manifests as decreased sensation in the median nerve distribution and excruciating pain. Operative stabilization is required to maintain the reduction.
Figure 2. The most common type of lunate dislocation with the lunate volar, rotated 90 degrees. The distal radius is abnormally articulating with the capitate, rather than the lunate.
A. PA radiograph of lunate dislocation with triangular, “piece of pie” lunate appearance (green arrows), disruption of carpal arcs, increased radiolunate space, and overlap of lunate with other carpals.
B. Lateral radiograph showing the “spilled teacup” appearance of lunate dislocation (yellow arrows), with the concavity of the lunate facing anteriorly. The lunate has volar displacement and angulation, and has lost articulation with the radius and capitate.
Kevin M. Rice, MD is the president of Global Radiology CME
Dr. Rice is a radiologist with Renaissance Imaging Medical Associates. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015 Dr. Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" award for the Most Effective Radiology Educator.
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