54 Int. J. Morphol., 32(1):54-60, 2014. Frequency of Ponticulus Posticus in Lateral Cephalometric Radiography of Peruvian Patients Frecuencia de Ponticulus Posticus en Radiografías Cefalométricas Laterales de Peruanos Iván E. Pérez * ; Allison K. Chávez ** & Darío Ponce *** PÉREZ, I. E.; CHÁVEZ, A. K. & PONCE, D. Frequency of ponticulus posticus in lateral cephalometric radiography of Peruvian patients. Int. J. Morphol., 32(1):54-60, 2014. SUMMARY: The Ponticulus posticus is an anomalous ossification of unknown origin that arches backward from the superior articular process to the posterior arch of the Atlas vertebra, it can be complete or partial and houses vascular and nervous elements; it is diagnosed by lateral cervical radiography, cephalometric radiography or CT scans. The purpose for the present study was to determine the frequency of partial and complete Ponticulus posticus in lateral cephalometric radiography of Peruvian patients and identify any possible genre or age group associations. The study consisted in reviewing 1056 lateral cephalometric radiography of patients between 3–56 years old in search of partial or complete Ponticulus posticus. The mean age of subjects studied was 14.05±7.43 years old. The Ponticulus posticus frequency was 19.79%, the partial Ponticulus posticus frequency was 11.08% and the complete Ponticulus posticus frequency was 8.71%; Cramer´s V and ETA statistics found not significant association between the PP and the genre or the age groups (p>0.05). The Ponticulus posticus is not an infrequent radiographic finding, our results are similar to those reported in the Americas and similar to different for other ethnic groups, we confirm that the Ponticulus posticus is not associated with genre or age and we reviewed the importance of the Ponticulus posticus in the prognosis of the Atlas-Axis surgical stabilization. KEY WORDS: Cervical Vertebrae/radiography; Heterotopic Ossification/radiography; Cervical Atlas/abnormalities; Cervical Atlas/radiography; Atlanto-Axial Joint/radiography. INTRODUCTION The vertebrae of the cervical part of the vertebral column demonstrate the greatest variability and these are the smallest and the most delicate among the true vertebrae. The first cervical vertebra, the Atlas, differs in structure from all the other cervical vertebrae because it is devoid of body and spine (Sylvia et al., 2011) and it is, also, the most varia- ble human vertebra (Wysocki et al., 2003). The upper part of the vertebral artery (VA) groove is bridged by the oblique ligament of the Atlas (Sylvia et al.) and sometimes this ligament becomes partially or completely calcified, by an anomalous ossification (Sylvia et al.; Hasan et al., 2001; Cho, 2009; Senoglu et al., 2006; Young et al., 2005), in the form of a bony arch (Sharma et al.) that extends from the lateral mass to the posteromedial margin of the VA groove (Paraskevas et al., 2005) and delineates a foramen for the passage of vascular and nervous elements (Tubbs et al., 2007). This bony arch/bridge has been termed differently in the literature: Ponticulus posticus (Hasan et al.; Tubbs et al.; Senoglu et al.; Young et al.; Miki et al., 1979; Krishnamurthy et al., 2007; Schilling et al., 2010; Koutsouraki et al., 2010), Ponticulus posterior of the atlas, Pons posticus, Atlas bridging, Kimmerle anomaly/variant/deformity of the atlas (Crowe, 1986), Posterior glenoid process, Posticus ponticularis (Crowe), Spiculum and Ponticulus Atlantis Pos- terior (Prescher et al., 1996); however, it most accepted name is Ponticulus posticus (Latin of little posterior bridge). The foramen below the ponticulus posticus (PP) has been termed differently too: Arcuate foramen, Foramen arcuale (Wysocki et al.; Crowe), Foramen sagittale (Crowe), Foramen atlantoideum posterior, Foramen retroarticulare su- perior or Upper retroarticular foramen, Canalis arteriae vertebralis (Crowe), Retroarticular vertebral artery ring, Retroarticular canal and Retrocondilar vertebral artery ring, * Radiología Oral, Centro para la Investigación de las Disarmonías Dentofaciales (CIDDENT), Lima Perú. ** Universidad Peruana Cayetano Heredia. Facultad de Estomatología. Departamento de Clínica Estomatológica, Lima Perú. *** Estadística, Centro para la investigación de las Disarmonías Dentofaciales (CIDDENT), Lima Perú.