The Denis three-column concept of spinal stability defines the middle column as:

• A The posterior longitudinal ligament, posterior half of the vertebral body and disc, posterior annulus fibrosus ✓
• B The anterior longitudinal ligament and anterior half of the vertebral body and disc
• C The ligamentum flavum, facet joint capsules, and posterior bony arch
• D The supraspinous and interspinous ligaments and posterior longitudinal ligament

Explanation

Denis's three-column model (based on CT studies of burst fractures): Anterior column = anterior longitudinal ligament + anterior half of vertebral body/disc; Middle column = posterior half of the vertebral body/disc + posterior annulus fibrosus + posterior longitudinal ligament; Posterior column = posterior bony arch (pedicles, laminae, facets, spinous processes) + posterior ligamentous complex (ligamentum flavum, facet capsules, interspinous and supraspinous ligaments). Injury to the middle column is the critical determinant of spinal instability — a fracture involving the middle column (e.g. burst fracture) implies potential instability. The PLC (posterior column integrity) determines surgical intervention in thoracolumbar injuries per TLICS scoring.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.