The use of Flexion-Extension (FE) radiographs in evaluating alert trauma patients remains controversial. The FE views are imaging techniques that are used to delineate the endpoints of the patient's active neck flexion and extension that would radiographically identify any ligamentous injury. (See Figure 3.) The concern with FE views is that the patient will injure his or her spinal cord during performance of the test. Therefore, the utility of and indications for FE views are not clear. Data by two authors demonstrate that static radiography is adequate to diagnose CSI in 95% of patients. (12,22) (See Figure 4.) Three retrospective series suggest that FE films do not identify injuries in patients with normal static radiographic series. (48,54,55) In patients with subtle spine abnormalities, there was some diagnostic value to performing FE radiographs. In the only study of injury caused during FE studies, one patient of 129 had transient tingling in the upper extremities during positioning that resolved spontaneously after relaxation. (48)
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When ordering FE radiographs in the trauma patient, it is important to clarify whether the patient demonstrated adequate neck motion (FE) during the study. (56) In case of an inadequate study, a patient should be immobilized pending repeat radiographic evaluation in five days. Providing time for pain and muscle spasm to resolve should allow for a repeat, adequate radiographic study. However, it is unclear how often an FE study is inadequate. Up to one-third of FE radiographs ordered in adults acutely after trauma may be inadequate. (57) These data note that angular motion of approximately 40[degrees] is necessary between [C.sub.2] and [C.sub.7] for an adequate study. There is no clear definition of adequate motion on pediatric FE films. Specifically, the normal degree of tilting and relative motion between vertebral bodies changes throughout childhood. One author has demonstrated that tilting angles during flexion decrease with age at the [C.sub.2-3] and [C.sub.3-4] junctions. (2) Extension tilting increases with age at the [C.sub.4-5] and [C.sub.5-6] joints. These tilting changes are changes of approximately 3-5[degrees] throughout childhood. Sliding motion during flexion decreases with age at the [C.sub.2-3], [C.sub.3-4], and [C.sub.4-5] joints. This motion decreases from 18-25% down to 5-10% of vertebral width.
Acute FE magnetic resonance imaging (MRI) may have a role in identifying pediatric operative candidates sustaining ligamentous injury. (58)
Specific Injuries that Occur in Children
Occipitoatlantal Dislocation. The outcome of children with occipitoatlantal dislocation is uniformly poor. (12) This injury usually results from a high-energy impact, as seen in Motor vehicle crashes. Examination of the Cervical spine radiographs must include assurance of an appropriate relationship between the occiput and the atlas. The distance between the basion and the dens should not exceed 10 mm in children and 5 mm in adults. (59) It is not uncommon for normal patients to exceed these criteria. (60) The Powers ratio can be calculated. The ratio of the distance from the basion to the Anterior edge of the Posterior arch of the atlas divided by the distance from the opisthion to the posterior portion of the anterior arch of the atlas should be less than 0.9. A ratio greater than 1.0 is abnormal. The Wackenheim clivis line is another technique to inspect for integrity of the atlanto-occipital joint. In this test, a line drawn along the posterior clivus should intersect or be tangential to the odontoid. (61-63) (See Figures 5 and 6.)
