Fracture-Dislocation¶

Definition¶

Fracture-dislocation of the thoracolumbar spine is the most severe category of spinal injury, characterized by translational displacement of one vertebral segment relative to another. All three spinal columns are disrupted, resulting in complete mechanical instability. These injuries carry the highest rate of neurological deficit among all thoracolumbar injuries.

Mechanism of Injury¶

Fracture-dislocations result from high-energy mechanisms with combinations of flexion, rotation, shear, and distraction forces:

High-speed motor vehicle collisions
Falls from significant height
Crush injuries
Pedestrian-vehicle impacts

The most common location is the thoracolumbar junction, where the rigid thoracic spine meets the flexible lumbar spine.

Classification¶

In the AO Spine system, fracture-dislocations are classified as Type C — Translation/Rotation injuries. They represent displacement of one vertebral body relative to the adjacent vertebra in any plane (sagittal, coronal, or axial). Type C injuries are often combined with Type A (compression) or Type B (distraction) components.

In the Denis system, fracture-dislocations represent failure of all three columns and are subdivided by mechanism: flexion-rotation, shear, and flexion-distraction variants.

Imaging Findings¶

CT¶

Sagittal images — Anterior, posterior, or lateral translation of one vertebral segment relative to the adjacent segment. Disruption of all normal alignment lines.
Axial images — Rotation of the vertebral body (asymmetric positioning relative to the posterior elements), "naked facet" sign, facet fractures or dislocations
Coronal images — Lateral translation, scoliotic deformity at the injury level
Comminuted vertebral body fractures are common
Fractures through the posterior elements (laminae, pedicles, facets)

MRI¶

Spinal cord transection, edema, or hemorrhage (complete cord injury is common)
Complete disruption of the posterior ligamentous complex
Disc disruption
Epidural hematoma
Paravertebral soft tissue hemorrhage

Clinical Pearl

Fracture-dislocations can be subtle on axial CT images if the translational displacement is small. Always trace the posterior vertebral body line and spinolaminar line on sagittal reformats — any step-off indicates translational displacement. On axial images, misalignment between the vertebral body and posterior elements at the same level (the "offset" appearance) indicates rotation.

Neurological Injury¶

Complete spinal cord injury occurs in a majority of thoracolumbar fracture-dislocations due to the severe displacement and canal compromise. In the thoracic spine, the canal-to-cord ratio is smallest, and even modest displacement can result in cord transection. At the conus medullaris (L1–L2) or cauda equina level, the injury pattern may be variable.

Management¶

Fracture-dislocations are uniformly treated surgically with urgent decompression and stabilization. Posterior pedicle screw fixation is the most common approach, often supplemented by anterior column reconstruction in cases of severe vertebral body comminution. Long-segment fixation (two or more levels above and below the injury) is typically required due to the severity of instability.

Key Points¶

Fracture-dislocations are the most severe thoracolumbar injuries with failure of all three columns
Classified as AO Type C (translation/rotation)
Translational displacement in any plane is the hallmark — trace alignment lines on sagittal CT
The majority result in complete neurological deficit
Treatment is always surgical with urgent decompression and stabilization
The thoracolumbar junction is the most common location

References¶

Vaccaro AR, Oner C, Kepler CK, et al. AOSpine thoracolumbar spine injury classification system: fracture description, neurological status, and key modifiers. Spine (Phila Pa 1976). 2013;38(23):2028-2037. https://pubmed.ncbi.nlm.nih.gov/23970107/
Vu C, Gendelberg D. Classifications in Brief: AO Thoracolumbar Classification System. Clin Orthop Relat Res. 2020;478(2):434-440. https://pmc.ncbi.nlm.nih.gov/articles/PMC7438146/
Denis F. Spinal instability as defined by the three-column spine concept in acute spinal trauma. Clin Orthop Relat Res. 1984;(189):65-76. https://pubmed.ncbi.nlm.nih.gov/6478705/
Gamanagatti S, Rathinam D, Rangarajan K, Kumar A, Farooque K, Sharma V. Imaging evaluation of traumatic thoracolumbar spine injuries: Radiological review. World J Radiol. 2015;7(9):253-265. https://pmc.ncbi.nlm.nih.gov/articles/PMC4585949/
Zhang A, Chauvin BJ. Denis Classification. In: StatPearls. StatPearls Publishing; 2023. https://www.ncbi.nlm.nih.gov/books/NBK544310/
Muijs SPJ, Foppen W, Smithuis F, Smithuis R. AO Spine Classification of Thoracolumbar Fractures. The Radiology Assistant. 2024. https://radiologyassistant.nl/musculoskeletal/spine/ao-classification
Thoracic spine fracture-dislocation. Radiopaedia.org. https://radiopaedia.org/articles/thoracic-spine-fracture-dislocation