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Fracture Dislocations of the Spine



- Discussion:
    - fracture dislocation injuries involve disruption of all three columns by a combination of compression, tension, rotation, and/or shear;
    - posteror to anterior shear type:
         - occurs w/ direct load to back, superior vertebral body segments are displaced anteriorly with respect to those below;
         - vertebral bodies usually remain intact;
         - orientation of facet joint prohibits anterior displacement of posterior arch, resulting in multiple frx thru post. arch;
         - lamina become detached from anteriorly displaced vertebral body segment, resulting in a free floating lamina;
         - dural tears are common;
    - anterior to posterior shear type:
         - posterior arch can be displaced posteriorly w/o inferior facet limiting displacement;
         - as result, AP shear injuries rarely have assoc dural tears;
    - flexion and rotation mechanism:
         - anterior columns fails by compression & rotation;
         - middle column fails primarily by rotation;
         - failure may occur thru the disk or vertebral body;
    - flexion distraction type:
         - this is distinguished from the simple flexion distraction Chance type injury by the presence of significant translation;
         - this is a highly unstable injury often assoc w/ neurologic deficit, dural tears, & intra-abdominal injuries;

- Associated Injuries:
    - intra abdominal injury;

- Thoracic Frx Dislocations:
    - if frx dislocation is above T7 or above and there has been no frx of ribs bilaterally or sternum, the spinal cord will be stable and only 
           conservative treatment is needed;
    - if there is a similar injury below T7, the frx will be unstable;
    - posterior instrumentation and fusion is indicated;

- Lumbar Spine Fracture Dislocation:
    - flexion injury w/ axial compression;
    - posterior ligaments ruptures & drives upper vertebral body into one below;
    - w/ rupture of posterior ligaments & loss of vertebral body (anterior column) support, upper spine will sublux or dislocate anteriorly;
          - w/ loss of both anterior and posterior stability, frx dislocations frequently present with rotational deformity as well;
    - radiographs:
          - more than 50% anterior collapse of the vertebral body;
          - widening of the spinous processes,
          - anterior translation, & displaced frx of posterior vertebral wall;

- Treatment:
    - frx dislocations are usually assoc w/ severe neurologic impairment;
    - goal of treatment is to realign spinal column and provide adequate posterior stabilization so as to allow for early mobilization