Carpal instability

Classification of Carpal Instability

1. Dissociative (CID): Instability within the same row.
   • DISI: Scapholunate dissociation.
   • VISI: Lunotriquetral dissociation.
2. Nondissociative (CIND): Instability between rows.
   • Radiocarpal, Midcarpal, or Combined instability.
3. Complex (CIC): Combination of dissociative and nondissociative instability.
   • Examples: Perilunate dislocation, Transscaphoid-perilunate dislocation.
4. Longitudinal (Axial): Disruption along the longitudinal axis.
   • Axial ulnar or radial disruption.
5. Adaptive: Instability secondary to structural changes.
   • Examples: Distal radius malunion, Scaphoid nonunion, Lunate malunion, Madelung deformity.

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Patterns of Instability

DISI (Dorsal Intercalated Segment Instability) Mcq ❓️

• Injury: Scapholunate ligament or scaphoid fracture.
• Lunate Position: Extended with the triquetrum (dorsal concavity).
• Scapholunate Angle: >60° (normal: 30–60°).

VISI (Volar Intercalated Segment Instability)

• Injury: Lunotriquetral ligament.
• Lunate Position: Flexed with the scaphoid (volar concavity).
• Scapholunate Angle: <30°.

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Diagnosis

1. Imaging Studies:
   • X-rays: Measure scapholunate angle and observe carpal alignment.
   • Arthrogram: Detects abnormal dye flow through disrupted compartments.
2. Classification Based on Motion:
   • CID: Abnormal motion within the same row.
   • CIND: Abnormal motion between rows.
3. Direction of Instability:
   • VISI, DISI, Ulnar or Radial translation, Volar or Dorsal translation.

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Management

• Acute (<6 weeks):
  • Closed reduction and immobilization.
  • Arthroscopic or open repair of injured ligaments.
• Chronic (>6 weeks):
  • Ligament reconstruction.
  • Carpal realignment procedures (e.g., scapholunate reconstruction).
  • Salvage procedures for advanced instability (e.g., proximal row carpectomy or wrist arthrodesis).

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