An observational study in Arcuate Foramen, Anatomical Variations and Spine Surgery Complications, sponsored by Ondokuz Mayıs University. Completed at 1 site in Turkey (Türkiye). Open to participants aged 18 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-08-19.
Sponsored by Ondokuz Mayıs University · Observational
This study aims to determine the prevalence and types of the arcuate foramen (AF), an anatomical variation of the first cervical vertebra (atlas), using three-dimensional computed tomography (3D CT). The arcuate foramen is formed when a bony bridge develops over the groove for the vertebral artery. Although often asymptomatic, it may increase the risk of vascular or nerve injury during surgery in the craniovertebral junction region.
In this retrospective observational study, 3D CT scans of 200 adult patients obtained between January 2023 and July 2025 at Giresun University Faculty of Medicine were reviewed. The presence of AF was classified as complete or incomplete, and also categorized according to its location (right, left, or bilateral). Associations with demographic variables (age, sex) were analyzed.
The results will help improve awareness of AF in preoperative planning for neurosurgical and spinal procedures, potentially reducing the risk of complications involving the vertebral artery and surrounding neurovascular structures.
The arcuate foramen (AF) is an anatomical variation of the atlas (C1 vertebra) that occurs when a bony bridge forms over the groove for the vertebral artery, creating a complete or partial tunnel. While frequently asymptomatic, its presence has been associated with conditions such as vertebrobasilar insufficiency, cervicogenic headache, and chronic neck pain. Importantly, AF may alter the course of the vertebral artery and suboccipital nerve, increasing the risk of injury during craniovertebral junction surgery, C1-C2 instrumentation, and posterior fossa approaches.
This retrospective cross-sectional study reviewed 3D computed tomography (CT) images of 200 adult patients obtained between January 2023 and July 2025 at Giresun University Faculty of Medicine. Images were reconstructed and analyzed using OsiriX MD software with a 3D volume rendering technique. AF was classified as complete or incomplete and further categorized by side (right, left, or bilateral). Associations with demographic variables, including age and sex, were examined.
Prevalence estimates were calculated with 95% confidence intervals. Interobserver agreement between two experienced neurosurgeons was assessed using Cohen's Kappa statistic. The findings aim to provide a clearer understanding of AF prevalence in the Turkish population and its potential surgical relevance. By identifying these variations preoperatively, surgeons can better plan instrumentation trajectories and minimize neurovascular complications in craniovertebral and upper cervical procedures.
Ondokuz Mayıs University is the lead sponsor of 262 studies on the registry; 68 are open to participants now.
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Adult patients (≥18 years) who underwent head computed tomography (CT) or computed tomography angiography (CTA) at Giresun University Faculty of Medicine between January 2023 and July 2025, whose images included the atlas (C1) vertebra and met quality criteria for three-dimensional reconstruction.
Exclusion Criteria:
Consecutive adult patients (≥18 years) whose high-quality 3D CT or CTA images included the atlas (C1) vertebra. Images were evaluated retrospectively for the presence, type (complete/incomplete), and laterality (right/left/bilateral) of the arcuate foramen.
Prevalence of Arcuate Foramen Variants
Proportion of participants with complete arcuate foramen identified on 3D computed tomography (CT). Unit of Measure: Percentage (%) of participants. Measurement Tool: High-resolution 3D reconstructed craniovertebral junction CT images, evaluated independently by two neuroradiologists. Analysis: Proportion calculated with 95% confidence intervals (CI).
Time frame: Baseline (single review of existing imaging data)
Association between Arcuate Foramen Type and Demographic Characteristics (Age and Sex)
Description: Relationship between arcuate foramen type (complete vs. incomplete) and patient demographics, including age and sex distribution. Unit of Measure: Age: Mean ± standard deviation (years) Sex: Percentage (%) of male and female participants Measurement Tool: Demographic data (age and sex) recorded from electronic medical records. Analysis: Age: Independent t-test or Mann-Whitney U test; effect size with 95% confidence interval (CI). Sex: Chi-square test or Fisher's exact test; odds ratio (OR) with 95% CI. Unit of Measure: Mean ± standard deviation (years). Measurement Tool: Age recorded from electronic medical records. Analysis: Independent t-test or Mann-Whitney U test; effect size with 95% CI.
Time frame: Baseline.
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Plan to share: No — This study involves retrospective analysis of de-identified radiological images. Individual participant data will not be shared to protect patient confidentiality.
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Ondokuz Mayıs University