Microanatomy of relationship of vertebral artery and C1～2vertebrae

Objective To study the anatomical relationship between C1-2 and Vertebral artery.Methods Ten adult cadaveric specimens were studied.The veins and arteries were injected with silicon pigments.We followed the nomenclature clarified by Cacciola.The artery during its course from the transverse process of C3 to the transverse process of axis was named after V1 segment,the artery during its course from the axis transverse process to the atlas transverse process was named after V2 segment and the segment of the artery after its exit from the transverse foramen of atlas to the point of its dural entry was named after V3 segment.The relationship of the artery to the atlanto-axial joint and facets,distance of the location of the artery from the midline,from the C2 ganglion and from the other surgical landmarks were researched.The extent of occupancy of the artery into the vertebral artery groove on the inferior surface of the superior facet of the axis,and over the posterior arch of the atlas were studied.Results The V1 segment of the vertebral artery took a varying degree of loop inside the vertebral artery foramen on the inferior aspect of the superior facet of the axis.The loop extended towards the midline and was at an average distance of 14.6 mm from the midline of the vertebral body.The V2 segment of the artery took an initial lateral loop after its exit from the transverse process of the axis.The average distance of the artery from the lateral end of the C2 ganglion was 7.7 mm and from the dural tube was 15.6 mm.The vertebral artery groove in the superior facet of axis and the groove over the posterior arch of the atlas were completely occupied by the vertebral artery only in six sides and in none respectively,suggesting the possibility of the dynamic nature of the relationship of the artery to the bone.Conclusions The vertebral artery adopts a serpentine course in relationship to the axis,making it susceptible to be injured during the surgical procedures in this region.The foundation of reducing the possibility of vertebral artery injury is to be familiar with its anatomy characteristic. Key words: Vertebral artery ;  Atlas ;  Axis;  Craniovertebral junction