Spilled Teacup

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    Spilled Teacup

    A 28 yoM comes in with hand pain after falling on an outstretched hand.

    His xray is as follows.

    Lunate Pic

     

    What is the diagnosis?

     

     

    The diagnosis is it is abnormal and the patient will need an orthopedist.

    Is it a perilunate or lunate dislocation? Does it matter?!

    Radiology Night Hawk service is down!  Will you be the laughing stock of the ortho service if you misdiagnosis this? Will misdiagnosis result in clinically adverse outcomes? Will missed diagnosis cost you a point on the inservice exam?

    It’s a lunate dislocation.

    From stage 1 to stage 4, disruption of various perilunate ligamentous structures results in progressive instability of the lunate and surrounding carpals.  Stage one is a perilunate dislocation, progressing to the most unstable lunate dislocations, stage 4.  In perilunate dislocation the lunate remains articulated on the radius, with the capitate dislocated volarly or rarely, dorsally.  In lunate dislocation, the dorsal radiocarpal ligament fails, and the lunate is dislocated volarly into the carpal tunnel.  The capitate, though dislocated, often remains grossly linear with the radius, and may sit directly over it.   The loss of ligamentous support in lunate dislocation often results in a “spilled teacup” sign, the lunate tipped over.

    These dislocations require prompt closed reduction, and literature supports open reduction and ligamentous/bony repair in 3-5 days after swelling improves (versus casting after closed reduction), because reduction is often not maintained with conservative management due to ligamentous injury . Post-reduction MRI or CT would be helpful for the surgeon to identify ligamentous injury or occult fracture.

    Median nerve injury is a possible sequela, as is osteoarthritis, carpal tunnel syndrome, joint stiffness, etc.

     

    Diagram: Top: perilunate dislocation.  Bottom: lunate dislocation. (In white are less common alignments of the dislocations).

     

    Lunate Diagram

     

     

    Below: perilunate dislocation.

     

    Perilunate

     

     

     

    REFERENCES:

    Stanbury SJ, Elfar JC. Perilunate dislocation and perilunate fracture-dislocation. J Am Acad Orthop Surg. 2011 Sep;19(9):554-62.

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