The purpose of this study was to evaluate diagnostic criteria using plain lateral radiography, the incidence of traumatic disc herniation and the degree of neurologic deficit in extension injury of the lower cervical spine.

We analyzed 28 patients with extension injury of the lower cervical spine, by measuring the retropharyngeal, retrotracheal space and the intervertebral space at the injured level in plain lateral radiography. We selected 40 patients as a control group for the prevertebral soft tissue space measurement.

Widening was found in the retropharyngeal space (6.8 ±2.9 mm) and in the retrotracheal space (15.2 ±3.8 mm) compared with the control group (4.2 ±0.7 mm, 12.6 ±1.9 mm, p<0.05). No significant increase in the injured intervertebral space was observed with respect to the normal upper and lower disc space. Neurologic deficit occurred in 25 cases (89%); with root injury in 11 cases and cord injury in 14 cases. There were 19 posterior disc herniations (68%), which were associated with neurologic deficits in all cases.

Extension injuries should be suspected in the presence of soft tissue injury of the anterior column without fracture or dislocation by the radiologic study of the lower cervical spine. Magnetic resonance imaging study is believed to be an essential diagnostic modality for the accurate evaluation and proper management of the lower cervical spine injuries.