Tag Archives: Perilunate dislocation

Lunate dislocation

March 28, 2013

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This is an image provided by one of our UC Davis resident physicians:

Lunate dislocation

Great example of a lunate dislocation!

The key portion of the film above is the half-moon shaped bone (Lunate) which is dislocated in the palmar direction and has a “spilled teacup” appearance (it is rotated from its normal position with the concave portion of the bone facing the distal fingers).

Lunate dislocation

The AP view on this patient is also interesting.  It shows a “Piece of pie” sign, also frequently found with lunate dislocation.  This is an abnormal triangular hyperdensity seen in the lunate on the AP projection (can also be seen in perilunate dislocation).

Lunate dislocation 2

The distinguishing feature of this radiograph to differentiate between perilunate and lunate dislocation is the alignment on the lateral projection.  The capitate and distal radius are still aligned, the lunate is dislocated.  In a perilunate dislocation the lunate will not have a “spilled teacup” rotation and the capitate will be dorsally displaced off the alignment of the distal radius.  An example of a perilunate dislocation:

PL Dislocation 2

Tip:  on lateral wrist xrays, always draw a line through the distal radius, lunate, and capitate.  It should look like an apple sitting in a teacup on a saucer.

Author:  Russell Jones, M.D.

Image Contributor:  Dane Stevenson, M.D.

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