Scapholunate Ligament Injury and Dorsal Intercalated Segment Stability



Scapholunate Ligament Injury and Dorsal Intercalated Segment Stability


Mark Henry



INTRODUCTION



  • Pathoanatomy



    • Intrinsic scapholunate interosseous ligament (SLIL) begins to fail volarly (1 mm thick, 117 N load to failure), as scaphoid and lunate separate under load, injury propagates around proximal portion of C-shaped ligament to dorsal fibers (3-4 mm thick, 260 N load to failure), completing full disruption.1,2


    • Complete rupture of SLIL only will acutely produce normal appearing radiograph when unloaded but loss of carpal relationships when axially loaded (dynamic instability).


    • Scaphoid (and contact area of radioscaphoid interface) translates dorsal and radial, also flexion and pronation; lunate extends and supinates; distal row translates dorsally


    • Additional injury to extrinsic capsular ligaments—secondary stabilizers (radioscaphocapitate, dorsal radiocarpal, dorsal intercarpal) acutely produce abnormal carpal relationships on unloaded radiograph (static instability).


    • Dorsal intercalary segment instability (DISI) can be dynamic or static, measured in sagittal plane on standard radiograph, using lateral SL angle (normal 30°-60°, average 47°) and lateral capitolunate angle >15°


  • Mechanism of injury3



    • Sudden forceful impact to palm with wrist extended, ulnarly deviated, hand supinated relative to a pronated forearm (particularly if point of impact is over thenar eminence)


    • Low to moderate force and slower rate of application will not cause complete scapholunate disruption (SLD)


  • Epidemiology



    • Younger to middle-aged active patients, strong male predominance


    • High-energy falls


    • Collision sports



EVALUATION

May 7, 2019 | Posted by in ORTHOPEDIC | Comments Off on Scapholunate Ligament Injury and Dorsal Intercalated Segment Stability
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