Ligamentous Instability

- See:
   - Flexion and Extension Views
   - SCIWORA Syndrome:

- Anterior Ligamentous Disruption:
    - detected by presence of small anteroinferior avulsions and segmental disc widening;
    - ligaments include: anterior longitudinal ligament & Annulus fibrosus;
    - w/ complete cervical dislocation from anterior ligament failure, more stable internal fixation (posterior plate stabilization) should be
          considered to permit early patient mobilization;
    - note: failure of the anterior vertebral body should always suggest posterior ligament failure;
    - if posterior ligament failure is ruled out, then treat patient w/ hard collar;
    - w/ post. lig. disruption (or with middle column collapse)
         - treat w/ gradual traction, reduction, & posterior stabilization and then fusion;
- Middle Column Ligamentous Disruption:
    - note: that the Middle column ligaments are also critical for stability against distractive forces; (post. long. lig. & annulus fibrosis)
        - sectioning of middle ligamentous complex (posterior longitudinal ligament and annulus) creates segment angulation of 11 deg and
             translation of 3.5 mm;
        - hence, evidence of middle ligamentous complex disrupton
             - interspinous or intervertebral angulation 11 deg greater than the adjacent spinal segment (normally 2-4 deg)
             - horizontal translation greater than 3.5 mm;
             - intervetebral disk space separation > 1.7 mm;
- Posterior Ligamentous Disruption:
    - failure of posterior ligamentous complex may occur in conjunction w/middle complex disruption or with other instability patterns;
    - radiographic signs of posterior ligamentous disruption include dislocation or subluxation of facets, Facet Joint widening, &
         malalignment of the spinous processes on the AP view;
    - if vertebral body translation of > 3.5 mm occurs in conjuction w/facet dislocation, then middle ligament complex is disrupted as well;
         - this is a highly unstable injury w/ neurologic deficits
         - decompression of vertebral fragments may be necessary
         - reconstruction of the spinal segment with neural decompression then requires strut graft placement & either prolonged halo
              immobilization or internal fixation thru a posterior approach;
         - anterior plating alone may not be rigid enough to restore stability to the spine;
    - disruption of posterior ligamentous complex in face of anaterior frx or dislocation is a strong indication of instability and of
         potential necessity for surgical stabilization;
    - exceptions may include the upper thoracic spine, which is inherently more stable, and with bony Chance Fracture;
    - compression frx of 3 sequential vertebrae leads to increase in risk of posttraumatic kyphosis;
- Flexion Instability:
    - there are two types of flexion instability patterns in which posterior and middle ligamentous complexes are ruptured but the anterior
         complex is intact;
         - in one of these patterns there may be posterior element widening w/subtle compression frx of vertebral body;
         - other pattern is bilateral facet dislocation

Hyperextension-dislocation of the cervical spine. Ligament injuries demonstrated by magnetic resonance imaging.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Wednesday, April 11, 2012 4:25 pm