Prevalence and Morphologic Features of Ponticulus Posticus in Koreans: Analysis of 312 Radiographs and 225 Three-dimensional CT Scans

STUDY DESIGN: A retrospective review of three-dimensional CT scan images and radiographs. PURPOSE: To investigate the prevalence and morphologic features of ponticulus posticus in Koreans. OVERVIEW OF LITERATURE: There has been little reported on the prevalence or morphologic characteristics of ponticulus posticus in Asians, predisposing them to vertebral artery injury during screw placement in the lateral mass of the atlas. METHODS: The presence and types of ponticulus posticus were investigated on 225 consecutive cervical three-dimensional CT scans and 312 consecutive digital lateral cephalometric head radiographs. RESULTS: Various spectra of ponticulus posticus were found in 26% of the CT scans and 14% of the radiographs. CONCLUSIONS: Ponticulus posticus is a relatively common anomaly in Koreans. Therefore, the presence of this anomaly should be carefully examined for on radiographs before lateral mass screw placement. If ponticulus posticus is suspected or confirmed on radiographs, three-dimensional CT scanning should be considered before placement of lateral mass screws into the posterior arch, especially given its wide variation of size and shape.