Examination of bone structures in the craniovertebral junction on cone beam computed tomography

The craniovertebral junction (CVJ) is an anatomical transition site between the skull and the cervical spine. Several craniometric measurements have been described for the evaluation of CVJ pathologies such as basilar invagination, atlantoaxial dislocation and platybasia. Therefore, it is important to determine the normal range of craniometric measurements. The aim of this study is to contribute to the literature by determining the morphometric reference values of the bone structures of the CVJ on the Cone beam computed tomography (CBCT) images of healthy individuals aged 18-65 years living in Anatolia. For this purpose, CBCT images of 300 healthy individuals were evaluated retrospectively. Sixteen parameters in midsagittal section and 2 parameters in coronal section were examined on these images. Data were compared by gender and age. The distance of apex dentis to McGregor, Chamberlain, McRae, Fischgold digastric, Fischgold bimastoid and McRae lines was 0.31±3.22, 1.06±3.22, 5.30±1.59, 8.70±4.12, -5.15±4.86 and 35.58±2.52 mm respectively. Clivus-channel angle was 157.62 ± 11.85°, atlantodental interval was 1.28 ± 0.48 mm, posterior atlantodental interval was 19.54 ± 2.24 mm, Welcher basal angle was 130.83 ± 6.29°, basion-axial interval was 4.01 ± 1.83 mm, basion-dental interval was 4.92 ± 1.77 mm, Powers ratio was 0.72 ± 0.06, distance measured by modified Ranawat method was 28.66 ± 2.38 mm, distance measured by the Redlund-Johnell method was 35.11 ± 4.09 mm, and the craniocervical tilt angle was 126.98 ± 12.24°. Apex dentis was according to McGregor and Chamberlain lines, 102 (36%) and 86 (26%) at the upper level, 129 (46%) and 170 (57%) at the lower level, 52 (18%) and 42 (14%) at the same level respectively. Apex dentis was observed under the McRae line in all cases. It was below the Fischgold digastric line in 284 of cases and was found to be at the same level this line in 7 (2%) of the cases. Thirty five (12%) of the cases were below the Fischgold bimastoid line, 233 (82%) were above, 17 (6%) at the same level as this line. There is no consensus about the craniometric values of CVJ pathologies in the literature. It is thought that the results of this study will contribute to the literature. Further studies on different populations are recommended to determine the normal range.