Denis Three-Column Model of Spinal Stability, Which Involves Anterior (Anterior Half of Vertebra/Disc and Anterior Longitudinal Ligament), Middle (Posterior Half of Vertebra/Disc and Posterior Longitudinal Ligament), and Posterior (Posterior Elements, Including the Pedicles and Facet Joints and the Remaining Ligaments) Columns. According to This Paradigm, Any Injury Extending into the Middle Column is Largely Considered to Be Unstable.

(From KeplerCK, VaccaroAR. Thoracolumbar spine fractures and dislocations. In: Court-BrownCM, KeckmanJD, McQueenMM, et al., eds. Rockwood and Green’s Fractures in Adults. Vol 2. 8th ed. Philadelphia: Wolters Kluwer; 2015:1757–1793.)