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  • Using Superficial Landmarks to Locate the Third Segment of the Vertebral Artery: The Atlanto-mastoid Line

    Final Number:

    Ali Tayebi Meybodi MD; Jordina Rincon-Torroella; Xuequan Feng MD, PhD; Michael T. Lawton MD; Arnau Benet M.D.

    Study Design:
    Laboratory Investigation

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2015 Annual Meeting

    Introduction: Exposure of the third segment of the vertebral artery (V3) is an essential step of several surgical approaches to the posterolateral craniovertebral junction. This exposure is challenging and entails risk of uncontrolled bleeding. The most common landmark used to locate the artery is the C1 lamina. However, the landmark is only useful if exposed, while risk of V3 injury exists from the stage of skin incision. We have proposed a guide to locate the vertebral artery that is applicable throughout surgery.

    Methods: The suboccipital region was studied in 8 cadaveric heads (16 sides). The distances between three points were measured: (1) the most superficial point of V3 (V), (2) mastoid tip (M), and (3) posterior atlantal tubercle (A). The relative location of the projected V point on the atlanto-mastoid (A-M) line was calculated using trigonometric equations.

    Results: Point V was found within 12 millimeters, in any direction, of the A-M line. When projected on the A-M line, this point lied within 0.45 ± 0.04 (mean ± standard deviation) of the length of the A-M line measured from the mastoid tip.

    Conclusions: The A-M line is a useful guide to find the third segment of the vertebral artery. It uses two readily available bony structures (mastoid tip and posterior atlantal tubercle) and can be used before the skin incision is made. Because of minimal rotation of C1 vertebra relative to the skull, the A-M line may be applicable regardless of the patient positioning. However, the clinical applicability and reliability of this guide despite positioning maneuvers should be confirmed in clinical studies.

    Patient Care: Using the guide presented in this study to locate the third segment of the vertebral artery, can help the surgeon reduce the time of exposure and also avoid problems with inadvertent injury of the artery during posterolateral approaches to the craniovertebral junction.

    Learning Objectives: 1/ safe identification of VA during the muscular stage of the far lateral approach 2/identification and use of surgical landmarks for efficient suboccipital dissection, 3/Prevention of massive and potentially devastating bleeding by understanding the regional anatomy of V3.


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