CT is the most sensitive initial study for diagnosing spine fractures, and should be ordered if a fracture is suspected or has been demonstrated on plain films. 

    While the cross-table lateral cervical spine film is often the most useful x-ray for imaging the cervical spine, the open mouth odontoid view is the best for evaluating C1, the dens, the body and superior facets of C2, and atlantoaxial articulation.  This is the most technically challenging film of the cervical spine series because it requires an alert patient to open the mouth as wide as possible.  The beam is directed perpendicular to the midpoint of the open mouth of the supine patient and the tongue is depressed by saying, “ah”.

     The lateral masses of C1 should align perfectly with the lateral masses of C2 (blue lines).  The medial aspect of the C1 lateral masses should be equidistant to the odontoid (letter A - in this case asymmetrically widened on the right).  A distance of  >7mm from a C1 lateral mass to the dens indicates transverse ligament rupture or C1 burst (Jefferson) fracture.   There are rare normal variants of the dens that can be misinterpreted as fractures, and overlapping lateral masses can be a normal variant in children.