Presentation
Fell from a ladder with outstretched hand.
Patient Data
Rx left wrist
Widening of distance between scaphoid and lunate to greater than 3 mm "Terry-Thomas sign". There's also the "ring sign" on the scaphoid.
Scapholunate angle 73.78°: intersection of a line drawn parallel to the long axis of the scaphoid and a line drawn perpendicular to the AP axis of the lunate. Normal range between 30-60º.
Capitolunate angle 10.92°: intersection of a line drawn parallel to the long axis of the capitate and a line drawn perpendicular to the AP axis of the lunate. It should measure less than 30º in resting position.
MRI Arthrography left wrist
Fat suppressed T1-weighted coronal image demonstrate failure of the ligaments at both ends of the scaphoid, with an increased scapholunate space, measuring more than 3.5 mm. T2-weighted coronal image demonstrates slightly ulnar translocation of only the lunate. The scaphoid bone remains in its native position. Sagittal T1-weighted fat-suppressed showing DISI deformity with exaggerated dorsal tilting of lunate.
The lunocapitate angle is 38° (normal <30°). Normal the triangular fibrocartilage complex (TFCC).
Case Discussion
When there is rotation of the scaphoid as can occur with scapholunate dissociation (widening of distance between scaphoid and lunate to greater than 3 mm), a ring-shaped density can appear as a sign of foreshortening (scaphoid cortical ring sign). If untreated, scapholunate instability progresses to degeneration and collapse of the carpus, known as scapholunate advanced collapse (SLAC).
Radiographer: TSRM Fabio Imola
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