The laminar space in the diagnosis of rotational flexion injuries of the cervical spine.

We measured the distance between the spinolaminar line and the articular pillars of the cervical spine (the laminar space), identified on lateral radiograph, to determine the diagnostic value of changes in this measurement in cases of unilateral facet dislocation. Twenty-seven cases of unilateral facet dislocation were compared with 70 normal spines and with 29 cases of hyperflexion injuries without unilateral facet dislocation. Abrupt alteration of the laminar space between two adjacent levels was found to be an accurate measure of rotation of the spine at the levels concerned; on the basis of this alteration, we were able to correctly diagnose 23 of 27 cases of unilateral facet dislocation and 22 of 23 cases of unilateral facet dislocation between C2 and C6. In only two of the 70 normal cases was a similar alteration of the laminar space seen, and one of these was due to a previous fracture. In none of the 29 cases of hyperflexion injury without unilateral facet dislocation was there abrupt alteration of the laminar space. We conclude that abrupt alteration of the laminar space is an accurate determinant for rotational anomalies of the cervical spine and, in particular, for unilateral facet dislocation.