Scapholunate Ligament Injury & DISI

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Topic updated on 08/07/13 7:38am
Introduction
  • DISI (dorsal intercalated segmental instability) is an instability pattern of the scapholunate joint caused by
    • scapholunate ligament injury
      • dorsal scapholunate ligament is stronger than volar
      • most common cause of DISI
      • most common ligament injury in wrist
      • mechanism of injury is hyperextension of a pronated wrist (often caused by a fall)
    • scaphoid fractures
    • kienbock's disease
  • If left untreated DISI deformity can progress into a SLAC wrist topic
  • DISI is a form of carpal instability dissociative 



Anatomy
  • Wrist ligaments and biomechanics 
Presentation
  • Physical exam
    • snuffbox tenderness
    • Watson test post
      • when deviating from ulnar to radial, pressure over volar aspect of scaphoid produces a clunk secondary to dorsal subluxation of the scaphoid over the doral rim of the radius
        • dorsal wrist pain or a clunk during this maneuver may indicate instability of scapholunate ligament
Imaging
  • AP radiographs
    • SL gap > 3mm with clenched fist view (Terry Thomas sign)  
    • cortical ring sign (caused by scaphoid malalignment)  
    • humback deformity with DISI associated with an unstable scaphoid fracture
  • Lateral radiographs
    • dorsal tilt of lunate leads to SL angle > 70° on neutral rotation lateral 
    • radiolunate angle > 15°
  • Arthogram
    • high specificity but low sensitivity
  • MRI
    • high specificity and medium sensitivity
  • Arthroscopy
    • gold standard for diagnosis
Treatment
  • Nonoperative
    • most people feel casting alone is insufficient
  • Operative
    • scapholunate ligament repair or SL reconstruction (if repair not possible)
      • indications
        • acute scapholunate ligament injury
        • chronic but reducible scapholunate ligament injuries
      • technique
        • primary repair can be done up to 17 months after injury
        • Blatt dorsal capsulodesis is often added to a ligament repair and remains a viable alternative for a chronic instability when ligament repair is not feasible
        • tendon reconstruction with weave not recommended due to high incidence of late failure
        • if pathoanatomy is scaphoid fx than ORIF vs. CRPP (+/- arthroscopic assistance)
    • stabilization with wrist fusion (STT or SLC)
      • indications
        • rigid and unreducible DISI deformity
        • DISI with severe DJD
      • technique
        • scaphotrapezialtrapezoidal (STT) fusion
        • scapholunocapitate (SLC) fusion
        • scapholunate fusion alone has highest nonunion rate 

 

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(SBQ07.38) A 32-year-old professional baseball player presents with wrist pain after a fall on his outstretched wrist 10 days ago. He initially thought it was a sprain, but presents due to continued pain worsened by push-ups. His physical exam shows dorsal wrist tenderness and is positive for the provocative test shown in Figure V. Standard PA radiograph of the wrist is normal. Which of the following radiographic views shown in Figures A to E would be most helpful in establishing the diagnosis? Topic Review Topic
FIGURES: V A   B   C   D   E  

1. A
2. B
3. C
4. D
5. E

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