These views are obtained with the patient performing maximal flexion and extension of the cervical spine. They are used to assess alignment of the spine, and to look for ligamentous instability. Note that the vertebral bodies remain aligned normally with movement, as is shown by the smooth, continuous posterior spinal line. Note the uniform widening of the interspinous spaces with flexion.

Identify the following:

1. posterior spinal line

2. interspinous space