Introduction: The atlas, or first cervical vertebra (C1), plays a crucial role in the craniovertebral junction. Unlike typical vertebrae, it lacks a vertebral body and is instead made up of two lateral masses connected by the anterior and posterior arches. Additionally, C1 is often associated with various congenital abnormalities, including defects in the posterior arch (PAD). The goal of our study is to characterize the defects of the C1 posterior arch, to identify the prevalence of this developmental anomaly in the population of north-eastern Romania and to objectivise the association with other C1 malformations. Materials and Methods: Our retrospective study encompassed 715 patients who underwent cranio-cerebral CT scans between May 2022 and August 2024. Two experienced radiologists reviewed the DICOM files. Results: In our cohort, we identified posterior arch defects (PADs) of the atlas in 1.95% of patients (14 out of 715). Our analysis revealed no significant differences related to sex, with the cases being equally distributed between seven women and seven men. The age group distribution was also similar, further supporting the notion that PADs are incidental findings. Although 4 out of 14 cases of PADs were associated with other malformations, statistical significance was not achieved. Conclusions: Posterior arch defects of the atlas are relatively common congenital malformations in the population of north-eastern Romania. The most frequent morphological form is median dehiscence, which aligns with Type A. These defects do not show a sex or age predominance, consistent with their classification as congenital malformations.
Nedelcu et al. (Wed,) studied this question.