Atlantoaxial subluxation on odontoid view

Anteroposterior projections of the atlantoaxial joint taken through the open mouth.
(A) Normal atlantoaxial joint. Note the symmetrical relationship of the lateral masses of the atlas (C1) to the odontoid process as well as to the lateral masses of the axis (C2).
(B) Rotatory subluxation of the atlantoaxial joint. Note the asymmetrical relationship of the lateral masses of the atlas to the odontoid process as well as to the lateral masses of the axis.