The rotational component in the dynamics of the C2-3 spinal segment.

The technique of the PA axial projection of the arches of the upper cervical vertebrae into the occipital foramen and the normal findings, are described. The influence of maximum forced anteflexion at the craniocervical junction and rotation of the head on the relations of atlas and axis is demonstrated. It seems that in this position rotation at atlas-axis level is restricted and partly transmitted to the C2-3 segment. Thus, selective clinical examination of the rotational component of the dynamics at C2-3 can be achieved and the pathological restrictions of movement can be assessed.