The scapholunate ligament is a critical stabilizer of the wrist. Its rupture most commonly leads to:

• A VISI (volar intercalated segment instability) with both scaphoid and lunate flexing volarly
• B DISI (dorsal intercalated segment instability) with scaphoid flexed and lunate extended ✓
• C Perilunate dislocation with the capitate displaced dorsally
• D Triquetrolunate dissociation causing VISI pattern

Explanation

The scapholunate (SL) ligament normally couples the scaphoid and lunate. When torn, the scaphoid tends to flex (rotate volarly) while the lunate extends (rotates dorsally) due to their unbalanced ligamentous constraints — this produces DISI (Dorsal Intercalated Segment Instability), seen on lateral wrist X-ray as a scapholunate angle >70° and a capitolunate angle >30°. VISI results from lunotriquetral ligament injury. The Terry Thomas sign (widened SL space on AP view >3mm) suggests SL ligament tear.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.