Scapholunate Dissociation

Posted in Musculoskeletal on July 22, 2014 by m.khodeer

Case A:

30 year old male, wrist pain
Findings? Dx?

MRI Correlation
Final Dx?

Case B:
29 year old Female, wrist pain
Findings, Dx?

Case C:
28 year old male, wrist pain
Findings, Dx?

Case D:
27 year old Female, wrist pain
Findings, Dx?

Answers
Carpal Dislocations

Cases 7A-D show the spectrum of lesser-arc injuries:
7A / Grade 1: Scapholunate dissociation ( = rotatory subluxation)
7B / Grade 2: Perilunate dislocation
7C / Grade 3: Midcarpal Dislocation (disruption of lunate/triquetrum)
7D / Grade 4: Lunate dislocation
Typical mechanism is severe dorsiflexion (e.g., fall on outstretched hand)

27A – Scapholunate Dissociation

Initial case (7A) showed only widening (> 2mm) between the scaphoid and the lunate; this is the “Terry Thomas” (aka “David Letterman”) sign
The lateral film is not especially helpful for diagnosing this injury
These findings represent scapholunate dissociation (rotatory subluxation of the scaphoid), and is the mildest form of this injury

Case B-D

Case 7B showed a transcaphoid perilunate dislocation; note that the lunate and radius remain normally aligned. This injury is 2-3x more common than a lunate dislocation

accompanied by a scaphoid fracture in 75%

Midcarpal and lunate dislocations, as shown in cases 7C and 7D, represent progressively more severe injuries

Scapholunate Dissociation

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