Determination of Clark station for diagnosis of basilar invagination of the cervical spine

The station of the first cervical vertebra is determined by dividing the odontoid process into three equal parts in the sagittal plane. If the anterior ring of the atlas is level with the middle third (station II) or caudal third (station III) of the odontoid process, basilar invagination is diagnosed.
(A) Line diagram.
(B) Radiographic representation.