The widened interspinous distance: a useful sign of anterior cervical dislocation in the supine frontal projection.

Anterior dislocation of the cervical spine may be detected reliably in the supine frontal projection by evaluating the cervical spinous processes. A widened interspinous distance (ISD) which measures more than one and one-half times the ISD above and more than one and one-half times the ISD below indicates the presence of an anterior cervical dislocation at the level of abnormal widening. Measurements of the interspinous distances from the C3-C4 interval through the C7-T1 interval in 500 patients with normal cervical spines and in 14 patients with documented anterior cervical dislocations revealed neither false positive nor false negative diagnoses by these criteria.