- See:
Ligamentous Instability:
- Discussion:
- compressive forces are transmitted thru the posterior vertebral body
wall onto the two
Uncovertebral joints;
- there is no significant disk material in this middle column;
- tensile forces are w/ stood by posterior longitudinal ligament
and the posterior
Annulus fibrosus;
- middle column is critical to maintaining stability;
- comprimise of the middle column is indicated by widening of the
pedicles, loss of more than 25% of the posterior vertebral ht.,
and the presence of fracture lines thru the posterior vertebral
body cortex (usually seen on CT);
- that middle column ligaments are also critical for stability against
distractive forces; (post. long. lig. &
annulus fibrosis);
- sectioning of the middle
ligamentous complex (the posterior
longitudinal ligament and annulus) creates segment angulation
of 11 deg & 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;
- isolated failure of the posterior wall (middle colum) w/o posterior
ligament failure is an unusual lesion;
- 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 greater than 3.5 mm occurs in
conjuction with a facet dislocation, then the middle ligamentous
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 the middle column (seen as widening of interpedicular
distances on
AP view or change in ht of posterior
cortex of the body) results in an unstable injury that may require
operative fixation;
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The three column spine and its significance in the classification of acute
thoracolumbar spinal injuries.
Spinal instability as defined by the three-column spine concept in acute
spinal trauma.
Complications in three-column cervical spine injuries requiring anterior
-posterior stabilization.
Axial loading injuries to the middle cervical spine segment. An analysis
and classification of twenty-five cases.
