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DISI (Dorsal Intercalated Segment Instability) and VISI (Volar Intercalated Segment Instability)

DISI (Dorsal Intercalated Segment Instability) and VISI (Volar Intercalated Segment Instability) are patterns of carpal instability caused by abnormal alignment of the lunate relative to the radius and adjacent carpal bones. DISI is most commonly associated with scapholunate ligament injury and produces dorsal tilting of the lunate, while VISI is classically associated with lunotriquetral ligament injury and produces volar tilting of the lunate.

DISI and VISI are forms of carpal instability resulting from disruption of the normal ligamentous balance between the scaphoid, lunate, and triquetrum. They are identified primarily by the position of the lunate on lateral wrist radiographs and by changes in carpal angles. DISI (Dorsal Intercalated Segment Instability) usually occurs following injury to the scapholunate ligament. The scaphoid tends to flex while the lunate extends dorsally with the triquetrum, producing an increased scapholunate angle, typically greater than about 60–70°. Chronic DISI may lead to progressive carpal collapse and eventually scapholunate advanced collapse (SLAC wrist). VISI (Volar Intercalated Segment Instability) is commonly associated with disruption of the lunotriquetral ligament. In this pattern, the lunate flexes volarly along with the scaphoid, producing a reduced scapholunate angle, often less than about 30°. Patients may present with wrist pain, clicking, weakness, or instability following trauma. Diagnosis is based on clinical examination and standard and stress radiographs, with CT, MRI, or wrist arthroscopy used when necessary. Management depends on whether the instability is acute or chronic, reducible or fixed, and whether arthritis is present. Treatment may range from immobilization and ligament repair or reconstruction to corrective procedures or salvage surgery in advanced degenerative cases.

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DISI (Dorsal Intercalated Segment Instability) and VISI (Volar Intercalated Segment Instability)

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DISI (Dorsal Intercalated Segment Instability) and VISI (Volar Intercalated Segment Instability)

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