Denis Three Column System
Divisions:
• Anterior column: anterior longitudinal ligament (ALL), anterior 2/3 of vertebral body and annulus
• Middle column: posterior 1/3 of vertebral body and annulus, posterior longitudinal ligament (PLL)
• Posterior column: pedicles, facets, ligamentum flavum, spinous process, posterior ligament complex (PLC)
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Significance:
Used to determine stability of spinal fracture
Definition of unstable fracture:
• Injury to middle column: widening of interpedicular distance on AP radiograph; loss of height of posterior cortex of vertebral body
• Disruption of posterior ligament complex combined with anterior and middle column involvement