Although the spine is protected by discs, ligaments and muscles it is just as vulnerable to traumatic injury as the rest of the skeletal system. However, the pattern of spinal fractures is unique and related to the three ‘columns’ of the spine – anterior (front), middle, and posterior (back). The front column consists of the anterior longitudinal ligament and the front half of the body, disc, and annulus. The middle column consists of the rear half of the body, disc, and annulus, and the posterior longitudinal ligament. The posterior column consists of the facet joints, ligamentum flavum, the posterior elements, and the interconnecting ligaments.
In the thoracic spine the sternum-rib complex is also regarded as a fourth column. Fractures can be classified as:
Compression fractures - the anterior portion of the vertebral body is wedged, most often as a result of vertical force but the middle column remains intact.
Burst fractures - are comminuted fractures of the vertebral bodies often associated with bone fragments in the canal and involving the anterior and middle columns. These usually result from high energy impact putting a vertical loading on the spine and are also frequently associated with neurological deficit.
Fracture-dislocation - these injuries include any combination of fractures with dislocation and involve all three columns. Usually the result of compression, tension, shear or rotation.
Flexion-distraction - these usually result from forceful forward flexion of the spine, typically in motor vehicle crashes where the victim is restrained by a lap belt only and tensional forces disrupt the back and middle columns. A variant of flexion-distraction injury is the Chance fracture, resulting from hyper-flexion of the spine. All three columns fail under tensile forces in a Chance fracture. The fracture extends through the vertebral body, pedicle, lamina, and spinous process, the posterior ligaments are disrupted, and the intervertebral disc and facet joints may also be distracted.