Distractive Extension

In its more severe forms, the forces producing distractive flexion result in progressive anterior to posterior ligament failure in one or more cervical motion segments. With complete ligamentous failure, the upper vertebrae displace posteriorly, creating significant spinal canal narrowing. When there is no significant bony injury, the ligamentous disruption may be very difficult to detect. With patients in the neutral position, there may very well be no subluxation. Thus magnetic resonance imaging (MRI) is strongly indicated when this mechanism of injury is suspected.

This type of injury pattern occurs in only 1% to 5% of all spine injuries.

COMPRESSIVE EXTENSION

Compressive extension involves axial loading in association with hyperextension. This may produce injuries as minor as a laminar fracture or as severe as the highly unstable “teardrop” fracture. In the latter, the anterior longitudinal ligament is ruptured, avulsing a small bone fragment from the superior aspect of a vertebral body and causing fractures of the lateral masses, pedicles, and lamina.

As force progressively increases, there may be a linear fracture through the facet in association with a pedicle and laminar fracture; bilateral posterior arch fractures and ultimately ligamentous injury. The majority of the most unstable fractures occur at the C6-7 level and account for less than 5% of spine injury.

A comparative study was undertaken of patients with distractive flexion and compressive extension cervical spine injuries. There was no significant difference with respect to severity of injury, level of injury, or neurologic sequelae. Sixteen percent of patients with either type of injury suffered complete spinal cord injury.

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