A survey of ponticulus posticus: Radiological analysis of atlas in an orthodontic population based on cone-beam computed tomography

Background: The ponticulus posticus (PP; Latin for little posterior bridge) has become an important anomaly of the atlas, as the use of the C1 lateral mass screw has become common in treating atlantoaxial instability.Aim: The purpose of this study was to retrospectively determine the prevalence and morphologic characteristics of PP in an orthodontic patient population using cervical three-dimensional (3-D) cone beam computed tomography (CBCT) images.Material and Methods: A retrospective study was conducted by selecting cervical 3-D CBCT images of 374 adolescent population and examining them for the presence and type of PP.Results: 161 patients with 298 complete or partial or bilateral or unilateral PPs were identified based on the 374 cervical 3-D CBCT scans. The prevalence of posticulus ponticus was founded 43.04% in adolescent population.Conclusion: Our results show that the presence of this anomaly should be carefully examined using preoperative lateral radiographs before lateral mass screw placement. If a PP is suspected or confirmed on radiographs, 3-D CBCT scanning should be considered before lateral mass screw placement into the posterior arch because of the variation in the size and shape of PPs and the possibility of injury.Keywords: Cone‑beam computed tomography, lateral mass screw, ponticulus posticu