Incidence of Congenital Posterior Arch Defects of the Atlas in Chinese Population.

Objective: To study the incidence of congenital posterior arch defects of the atlas and in combination with other congenital variations in the Chinese population.

Methods: We retrospectively reviewed 1405 images of cervical 3-dimensional computed tomography (3D CT) and 1284 images of head and cervical 3-dimensional computed tomography angiography (3D CTA), including images of 1539 male and 1150 female individuals. These images of cervical 3D CT and head and cervical 3D CTA were obtained in the Department of Radiology of 2 hospitals, Second and Third People's Hospital of Jingzhou, China, from January 2020 to October 2023. Congenital posterior arch defects of the atlas were classified according to the criteria of Currarino and colleagues. Congenital posterior arch defects of the atlas combined with other congenital variations including occipitalization of the atlas, the ponticulus posticus variation of the vertebral artery groove of the atlas, cervical fusion, and the transversal foramen of the atlas variant were also observed.

Results: A total of 2689 patients were included in this study. The overall prevalence of congenital posterior arch defects of the atlas was 0.74% (20 of 2689). There was no statistically significant difference in incidence between male (0.78%, 12 of 1539) and female patients (0.70%, 8 of 1150) (P > 0.05). Among all posterior defects, type A and B defects were found in 0.6% (16 of 2689) and 0.15% (4 of 2689) cases, respectively. There were no type C, D, and E defects and no anterior arch defects. However, in 20 cases of congenital posterior arch defects of atlas, 40% (8 of 20) combined with other congenital variations including occipitalization of atlas in 4 type A cases, bilateral complete ponticulus posticus variation of atlas vertebral groove in 1 type A case, C2-C3 fusion in 1 type A case, coexistence of unilateral complete ponticulus posticus variation of the vertebral artery groove of the atlas and unilateral unclosed transverse foramen in 1 type B case, and coexistence of unilateral unclosed transverse foramen in 1 type A case.

Conclusions: The incidence of congenital posterior arch defects of the atlas was low in a Chinese population. There was no difference between male and female individuals. Types A and B were the 2 major defects in this Chinese population, and the prevalence of type A and B combined with other congenital cervical variations were higher than those of types C, D, and E.