A safe approach to explore/identify the V2 segment of the vertebral artery during anterior approaches to cervical spine and/or arterial repairs: anatomical study

Laboratory investigation

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Object

The purpose of this study was to find a landmark according to which the surgeon can dissect the cervical spine safely, with the lowest possibility of damaging the vertebral artery (VA) during anterior approaches to the cervical spine or the VA.

Methods

The “safe zone” for each level of the cervical spine was described as an area where the surgeon can start from the midline in that zone and dissect the soft tissue laterally to end up on the transverse process and cross the VA while still on the transverse process. In other words, safe zone signifies the narrowest width of the transverse process at each level. In such an approach, the VA is protected from the inadvertent deep penetration of the instruments by the transverse process. The surgical safe zone for each level was the common area among at least 95% of the safe zones for that level. For the purpose of defining the upper and lower borders of the safe zone for each level, the line passing from the upper vertebral border perpendicular to the midline (upper vertebral border line) was used as a reference.

Cervical spines of 64 formalin-fixed cadavers were dissected. The soft tissue in front of the transverse process and intertransverse space was removed. Digital pictures of the specimens were taken before and after removal of the transverse processes, and the distance to the upper and lower border of the safe zone from the upper vertebral border line was measured on the digital pictures with Image J software. The VA diameter and distance from the midline at each level were also measured. To compare the means, the authors used t-test and ANOVA.

Results

The surgical safe zone lies between 1 mm above and 1 mm below the upper vertebral border at the fourth vertebra, 2 mm above and 1 mm below the upper vertebral border at the fifth vertebra, and 1 mm above and 2 mm below the upper vertebral border of the sixth vertebra. The VA was observed to be tortuous in 13% of the intertransverse spaces. There is a positive association between disc degeneration and tortuosity of the VA at each level (p < 0.001). The artery becomes closer to the midline (p < 0.001) and moves posteriorly during its ascent.

Conclusions

Dissection of the soft tissue off the bone along the surgical safe zone and removal of the transverse process afterward can be a practical and safe approach to avoid artery lacerations. The findings in the present study can be used in anterior approaches to the cervical spine, especially when the tortuosity of the artery mandates exposure of the VA prior to uncinate process resection, tumor excision, or VA repair.

Abbreviations used in this paper: LCM = longus colli muscle; VA = vertebral artery; VB = vertebral body.

Article Information

Address correspondence to: Kim Garges, M.D., NASA Spine Institute, 18100 St. John Drive, Nassau Bay, Texas 77058. email: kjgarges@earthlink.net.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    a: Digital image of the dissected cervical spine and VAs. The vertical black line identifies the midline of the cervical spine. Each horizontal black line passes from the upper vertebral border at different levels. Lines “a” and “b” show the distance of the upper and lower edges of the transverse process from the upper vertebral border at the level of the fourth vertebra. The surgical safe zone is the area between lines “d” and “e” at the level of the fifth vertebra. b: Digital image of the dissected cervical spine and VAs at the third and fourth vertebrae. The vertical red line identifies the midline of the cervical spine. Labels “a” and “d” are at the middle of the upper and lower vertebral borders. The diameter of the VA can be measured along the lines “c” and “e” at the level of the center of the vertebrae. These 2 lines are perpendicular to the axis of the VA at each level. c: Digital image of the dissected cervical spine depicting the intertransverse ligament. In all figures, the rulers show the scale of only the panels in which they appear.

  • View in gallery

    a: Digital image of the dissected cervical spine showing inward looping of the VA inside the vertebrae. b: Digital image of the dissected cervical spine showing tortuosity of the VA.

  • View in gallery

    Digital image of the dissected cervical spine showing VA tortuosity (a) and the encroachment of the osteophytes from the lateral border of the vertebrae over the intertransverse space and VA (b) (arrow).

  • View in gallery

    Box plot showing the distance in millimeters from the medial border of the VA to the midline at different levels of the cervical spine. Circles and asterisks indicate the outliers.

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