Presentation
Right wrist pain following fall from steps. Additional history of remote trauma.
Patient Data
The wrist radiographs show marked volar tilt of the lunate on the lateral view. However, no volar displacement of the lunate bone, which would suggest a lunate dislocation. The angle between the lunate and scaphoid is decreased (almost collinear) while the angle between the distal radius and lunate is increased (no longer collinear). These findings are compatible with a VISI deformity. This appears chronic. There is no acute fracture or dislocation.
Case Discussion
The wrist consists of two carpal rows, the proximal row is considered the intercalated segment and can experience instability from disturbance or laxity of the scapholunate and lunotriquetral ligaments. These ligaments stabilize the carpal bones and distribute force across the wrist to balance the palmar flexion tendency of the scaphoid and the dorsiflexion tendency of the triquetrum. A volar intercalated segment instability (VISI) deformity features a volar rotation of the lunate mainly after disruption of the lunotriquetral ligament.
On lateral imaging, volar flexion of the lunate with a scapholunate angle, measuring <30 degrees and an increased capitolunate angle measuring >30 degrees 1 has been used in the diagnosis. Recently a lower capitolunate cut-off angle of >15 degrees has been suggested 2.
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