Back to Basics: Lunate vs Perilunate Dislocation

By: Angela Ugorets, MD

Case:  A 30 year old female comes to the ED with severe right wrist pain and swelling  after a FOOSH injury down a flight of stairs. Her wrist was extended at the time of the fall.   Her imaging is below.

Source: James Heilman, MD, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

What is the diagnosis?

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Diagnosis:

LUNATE DISLOCATION

• Rare injury – less common than peri-lunate injury
• Often from high force or high velocity injury on dorsiflexed wrist
• Will  see swelling on volar side  of wrist with associated pain
• Causes acute carpal tunnel and compresses median  nerve. 
• Can test the medial nerve  by asking patient to make an "ok" sign with their finger and thumb and by giving a thumbs up.
• Lunate dislocations are easily overlooked on AP Xray
• On lateral Xray, will see the lunate displaced in volar direction, it classically  no longer articulates with capitate or the radius.   While the radius and rest of the carpal bones remain aligned. The appearance of the lunate is often referred to as a  "spilled teacup." 
• This injury requires emergent orthopedic consultation
• Patient needs immediate closed reduction, almost always followed by  open reduction, ligament repair, fixation, and carpal tunnel release.
• Lunate dislocations that are left untreated for extended period of time have poor functional outcomes and increased rates of arthritis, however unfortunately usually have poor outcomes even when treated appropriately.

Peri-lunate dislocation is a similar injury, except in that case, the lunate does articulate with the radius, and it is the capitate and rest of the carpal bones that are not aligned.   Peri-lunate dislocations are often associated with scaphoid fractures.   Management and outcomes are similar between these two injuries.

References

Murphy A, Dixon A, et al. Lunate dislocation. Radiopaedia. Accessed June 3, 2021. https://radiopaedia.org/articles/lunate-dislocation?lang=us

Rasuli B, Dixon A, et al. Perilunate dislocation. Radiopaedia. Accessed June 3, 2021. https://radiopaedia.org/articles/perilunate-dislocation?lang=us Karadsheh M.

Lunate dislocation (perilunate dissociation). Orthobullets. May 13, 2021. Accessed June 3, 2021. https://www.orthobullets.com/hand/6045/lunate-dislocation-perilunate-dis...