Screws, Facets, and Atlantoaxial Instability

The aim of this study was to calculate the prevalence of ponticulus posticus (a small bony bridge on the dorsal aspect of the atlas on lateral digital cephalometric radiographs) and classify it into a complete ring or an incomplete ring. The study also investigated its association with the presence or absence of cervicogenic headache in the examined population; a literature review of ponticulus posticus is also presented.The presence and types of ponticuli posticus were investigated on 500 digital lateral cephalograms and the same patients were questioned for a history of cervicogenic headache.In 500 patients, 79 ponticulus posticus (34 complete and 45 incomplete) were identified on the lateral cephalograms; therefore, the prevalence was 15.8%. The distribution of the type of ponticulus posticus was 13.1% in males and 17.9% in females in the studied sample. The overall prevalence of cervicogenic headache was 6% in the studied sample with a significant association between cervicogenic headache and type of ponticulus posticus.The study shows that ponticulus posticus is not a rare finding and its association with unexplainable headache, neck pain, and other symptoms as well as its importance and implications during management of cervical spine surgical procedures, especially those requiring lateral mass screw placements in the atlas, imply that radiologists and dentists in general should closely inspect the vertebral region on a lateral cephalogram.