Morphometric Anatomy of Atlas (C1) and Axis (C2) on Dry Bones Versus CT Scan Images: A Cross-sectional Study from Southern India

Abstract

Introduction: The uniqueness of the atlas (C1) and axis (C2) cervical vertebrae helps in transmitting weight from the cranial cavity to the rest of the vertebral column. A detailed understanding of the C1 and C2 morphometric dimensions is essential for evaluating treatment protocols such as screw placement and intralaminar fixations to provide stability for the occipitocervical complex. Computerised Tomography (CT) scan images are best for demonstrating the osseous margins. Aim: To assess the relationship between the linear morphometric measurements of the CT images and dry C1 and C2 vertebrae. Materials and Methods: A descriptive, cross-sectional study was conducted using 35 atlas (C1) and 35 axis (C2) dry bones from the Department of Anatomy, Karuna Institute of Medical Sciences, Palakkad, Kerala, India, from August 2023 to October 2023. A total of 35 CT scan images were also taken for the study. Siemens Syngo software tool was utilised to assess the C1 and C2 vertebrae. Measurements of the vertebral canal, foramen transversarium, superior articular facets, vertebral artery groove, dens, and body were performed on dry C1, C2, and CT images. Descriptive statistics were evaluated using mean, standard deviation, percentage difference, and mean deviation. The unpaired t-test was used to test significance, with p-value <0.05 considered statistically significant. Results: Concerning the anatomical parameters, between the dry C1 and CT scan images, all linear parameters were statistically significant (p-value <0.05), except for the vertebral artery groove-inner and outer distances, which were not statistically significant. Regarding C2, when comparing anatomical parameters between dry vertebrae and CT scan images, the width of the body and the length of the vertebral canal were not statistically significant, while all other C2 parameters were statistically significant (p-value <0.05). Conclusion: The results obtained from the study on the atlas and axis may be valuable for operating surgeons during surgical procedures in the craniovertebral region. The present study also aids in preventing iatrogenic complications, including vertebral neurovascular injuries, and provides a roadmap for skilled surgical access.