A cadaveric study exploring the distance of atlantal segment of vertebral artery from the various clinically relevant landmarks

Background: The vertebral artery (VA), a branch of the subclavian artery, passes through the transverse foramina of upper six cervical vertebra. The third segment, V3, lies at craniovertebral junction, commencing from C2 transverse foramen and extending to the foramen magnum. The present study highlights the distance of the various segments of V3/atlantal segment of VA from the surgically important bony landmarks. Methods: The study was conducted at the Department of Anatomy and included 40 VA of twenty embalmed South Indian cadavers. The V3 segment is subdivided into vertical, horizontal, and exit parts. The distance of each part of VA from different landmarks was measured using a digital Vernier caliper. Results: Two rare variations in the course and branching pattern were noticed. Most of the mean distance of all the parts [V, H, E parts] of VA from various landmarks was almost similar. Using paired t-test, 3 significant values resulted, among which the distance from the ganglion to horizontal part of VA (p value 0.030) was found with a higher t-value. The mean distance between two posterior tubercles in the transverse processes of the C1 and C2 vertebrae was found to be greater on the left side (23.200 mm) than on the right side (22.350 mm). B2TR and B2TL were correlated, and Pearson's r value was 0.789, which indicates a strongly positive correlation. Conclusion: This study gives the safe limits to the neurosurgeons who intend to operate on a limited part of V3 segment of VA during occipital condyle screw technique, C1 laminectomy, etc.