The incidence of cervical spine injury in blunt trauma patients varies according to the criteria used to select patients for screening, the manner in which patients are screened, and the criteria used to define injury relative to a given imaging modality. The National Emergency X-radiography Utilization Study (NEXUS) reported an incidence of 2.8% among patients evaluated in emergency departments following blunt trauma. Gross man and colleagues reported an incidence of 4.3% in more than 100,000 patients admitted to trauma centers. It has been shown that the incidence of cervical spine injury increases with injury severity, severe closed head injury, severe facial fractures, associated spinal column injury, and the use of computed tomography (CT) scanning as a screening tool. The overall clinical relevance of routine use of CT as a screening tool for cervical spine injury is not known with respect to adequate three-view cervical spine x-rays. Sensitivity for detection of bony injury is clearly better. However, treatment mandated by detection of injury that may be clinically silent has increased the use of rigid cervical collars with an unknown effect on outcomes.

It is important to note that exclusion of bony injury does not “clear” the cervical spine in every case. There is a possibility that patients without bony injury may sustain clinically significant ligamentous injury that could result in subluxation and neurologic sequelae if unrecognized. The incidence of such injuries is difficult to estimate based on considerations outlined earlier, but is most likely less than 1% in most trauma centers. Similarly the incidence of spinal cord injury without radiographic abnormality (SCIWORA) is difficult to estimate and most likely represents operational terminology prior to the widespread use of magnetic resonance imaging (MRI) to image patients with any degree of neurologic dysfunction following injury. Dysfunction includes but is not limited to anatomic syndromes (central cord, anterior cord), dysesthesias, transient symptoms (spinal “concussion”), and disc herniations. MRI has high sensitivity in detecting anatomic lesions, particularly in the presence of acquired chronic spinal stenosis or spondylolisthesis.