Several classification systems have been proposed to define thoracolumbar fractures. In 1983, Francis Denis described a novel classification system to facilitate the communication of these fractures and their treatments among different medical professionals. In his study, he retrospectively analyzed 412 thoracolumbar injuries and developed a three-column theory, replacing the previous two-column theory popularized by Sir Frank Holdsworth. This newly-defined three-column theory would become the foundation for a classification system that would be widely adopted by spine surgeons to formulate treatment algorithms of thoracolumbar injuries.
Under the Denis classification system, the spine gets subdivided into three columns with the included elements:
The impetus in creating this third column was to describe the inherent instability of this middle column. Fractures involving the middle column were considered unstable with injury to the posterior longitudinal ligament in addition to the posterior annulus fibrosis, while isolated complete disruption of the posterior ligamentous complex was insufficient to prompt frank instability.
Based on the findings in his study, Denis went on to classify thoracolumbar injuries into four major types, based on column involvement and mechanisms of injury:
Anterior flexion & axial loading
3. Flexion-Distraction (Seatbelt-Type)
Flexion injuries to the middle and posterior columns with distraction posteriorly from tensile forces. The ALL serves as the axis of rotation, and the anterior column may fail secondary to compression.
Variable mechanisms: shear, rotation, compression, and tension
The classification systems for thoracolumbar injuries have evolved over time. However, there is no universally accepted system yet at this time. As such, there is not a current standardized treatment algorithm explicitly designed for the Denis classification. Instead, general treatment principles may be applied to the following fractures, although significant controversy still exists in operative indications:
Posterior instrumentation and fusion
Anterior/posterior decompression and instrumented fusion
Posterior instrumentation, with or without fusion
Fracture Dislocation Injuries
All require open reduction with instrumented fusion
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