Normal anatomical variations of the V-3 segment of the vertebral artery: surgical implications

作者：Ulm Arthur J^*; Quiroga Monica; Russo Antonino; Russo Vittorio M; Graziano Francesca; Velasquez Angel; Albanese Erminia

来源：Journal of Neurosurgery-Spine, 2010, 13(4): 451-460.

DOI：10.3171/2010.4.SPINE09824

• vertebral artery
• V-3 segment
• microsurgical anatomy
• atlantoaxial complex
• craniovertebral junction
• vertebral artery injury

Object. The authors undertook this cadaveric and angiographic study to examine the microsurgical anatomy of the V-3 segment of the vertebral artery (VA) and its relationship to osseous landmarks. A detailed knowledge of these variations is important when performing common neurosurgical procedures such as the suboccipital craniotomy and the far-lateral approach and when placing atlantoaxial instrumentation.
Methods. A total of 30 adult cadaveric specimens (59 sides) were studied using magnification x 3 to x 40 after perfusion of the arteries and veins with colored silicone. Seventy-three vertebral angiograms were also analyzed. The morphological detail of the V-3 segment was described and measured in both the cadavers and angiograms. Transarticular screws were placed into 2 cadavers and the relationship of the trajectory to the V-3 segment was analyzed.
Results. The authors identified 4 sites along the V-3 segment that are anatomically the most likely to be injured during surgical approaches to the craniovertebral junction. In 35% of the cadaveric specimens the vertical portion of V-3 formed a posteriorly oriented loop that could be injured during surgical exposures of the dorsal surface of C-2. The mean distance from the midline to the most posteromedial edge of the loop was 25.6 +/- 3.5 mm (range 20-35 mm) on the left side and 30.4 +/- 3.8 mm (range 23-36 mm) on the right side. On lateral angiograms, this loop projected posteriorly, with a mean distance of 9.8 +/- 3.5 mm (range 0-15.7 mm) on the right side and 11.7 +/- 1.2 mm (range 10-13.6 mm) on the left side. The horizontal segment of V-3 can be injured when exposing the lower lateral occipital bone and when the C-I arch is exposed. The mean distance from the inferior border of the occipital bone to the superior surface of the horizontal segment of V-3 was 6 +/- 2.8 mm on the right side and 5.6 +/- 2.3 mm on the left. In 12% of cases the authors found no space between the horizontal portion of V-3 and the occipital bone. The medial edge of the horizontal segment of V-3 was located 23 +/- 5.5 mm (range 10-30 mm) from the midline on the right side and 24 +/- 5.7 mm (range 15-32 mm) on the left side. The transition between the V-2-V-3 segments after exiting the C-2 vertebral foramen is the most likely site of injury when placing C1-2 transarticular screws or C-2 pars screws.
Conclusions. The normal variation of the V-3 segment of the VA has been described with quantitative measurements. An awareness of the anatomical variations and the relationships to the surrounding bony anatomy will aid in reducing VA injury during suboccipital approaches, exposure of the dorsal surfaces of C-1 and C-2, and when placing atlantoaxial spinal instrumentation. (DOI: 10.3171/2010.4.SPINE09824)

• 出版日期2010-10