Distractive Flexion

In the first phase of injury, the posterior ligaments fail, allowing the facets to displace anteriorly. In the second phase, there is unilateral facet dislocation as the interspinous ligament, facet capsule, and posterior longitudinal ligaments give way. With further force, the second facet capsule ruptures and bilateral facet dislocation occurs.

Approximately one third of spinal cord injuries occur as a result of distractive flexion forces, and the injuries are typically complete, especially with bilateral facet dislocation (see Plates 2-16 to 2-20).

Radiographically, unilateral or bilateral facet dislocations are typical, with associated vertebral body subluxation. The difference between these injuries is readily distinguishable radiographically. With a unilateral facet dislocation, there is approximately 25% anterior subluxation of one vertebral body on another. With bilateral facet dislocation, there is greater than 50% anterior subluxation. These injuries are generally highly unstable, are associated with significant neurologic deficits and commonly require internal reduction and stabilization.

Traction will usually reduce a unilateral facet dislocation. If there are fractures of the facet, once realignment has been accomplished, treatment with a halo may allow for stable healing. Bilateral locked facets are rarely reduced with traction and can be treated through an anterior or posterior surgical approach. On occasion, both anterior and posterior surgical approaches are required to achieve reduction and stabilization.

There is, however, one significant caveat in the use of traction with facet dislocations. It has been reported that up to 25% of these patients will have an associated traumatic herniated disk at the level of injury. Realigning the spine in the face of an anterior compressive mass, such as a traumatic herniated disk, could potentially result in additional spinal cord compression and further spinal cord injury. It has thus been recommended that patients with facet dislocations and an incomplete spinal cord injury syndrome undergo magnetic resonance imaging (MRI) to look for a traumatic herniated disk before realignment is attempted.

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