Compressive Flexion

Initially, as force is progressively applied, there is blunting of the anterosuperior aspect of the vertebral body, with the subsequent development of oblique fracture lines through the centrum of the body. Eventually, there is fragmentation of the centrum with peripheral displacement of the bony fragments.

This biomechanical mechanism reinforces the three-column theory of spinal stability. The anterior column extends from the anterior longitudinal ligament to the midpoint of the vertebral body. The middle column includes the posterior half of the vertebral body and the posterior longitudinal ligament. The posterior column includes pedicles, lamina, facets, and spinous processes along with all supporting ligaments. Any injury involving two of the three columns is generally unstable.

Compressive failure of the anterior aspect of the vertebral body rarely leads to neurologic injury. However, with ligamentous failure and posterior movement of the vertebral body, the incidence of complete spinal cord injury significantly increases (see Plates 2-16 to 2-20). Approximately one third of spine injuries result from compressive flexion, with a high occurrence at the midcervical levels.

Traction is rarely indicated, unless there is an associated facet dislocation or other injury that might be amenable to realignment. Magnetic resonance imaging (MRI) scan will clearly show the degree and extent of spinal canal compromise as well as blood and/or edema within the spinal cord.

Compressive flexion injuries comprise approximately one third of cervical spine injuries and most commonly occur at the C4-5 and C5-6 levels.

Anterior vertebral body compression and minor burst fractures may be treated with external orthoses such as the halo. These types of fractures will heal stably in more than 70% of patients. Burst fractures with greater than 3 mm retropulsion and significant canal compromise usually require anterior and, on occasion, posterior operative decompression and stabilization as well. Such is also the case if there has been significant associated ligamentous disruption.

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