{
    "abstract": "The vertebral artery (VA) usually enters the transverse foramen at the C6 level. Thus, surgeons prefer to insert pedicle screws (PSs) at C7, but this does not eliminate the risk of VA injury. We aimed to clarify anatomical features of the VA V1 segment at the C7 pedicle level, based on computed tomographic angiography (CTA) of 81 consecutive patients.\nWe examined the course of the VA V1 segment on axial CTA images. VA position was classified according to its alignment with the anterior (A), middle (M), or posterior (P) third of the C7 vertebral body at the pedicle level. We also assessed the prevalence of hypoplastic VA (HVA). We measured the distance (VED) from the optimum C7 PS entry point (Ep) to the center of the VA. We also measured the angles formed by the vertebral midline and a line from the inner edge of the VA to the Ep (the VEA), and by the vertebral midline and a line from the inner edge of the pedicle to the Ep (the PEA).\nThe variant location of the VA to the C7 vertebra was A in 13 courses (8.1%), M in 123 (76.9%), and P in 20 (12.5%). HVA was present in the contralateral side in 7 of 20 courses (35%) in the P group, and in 8 of 127 courses (6.3%) in the M group (p\u00a0<\u00a00.05). The mean VED was 20.2\u00a0mm, the mean VEA 6.9\u00b0, and the mean PEA angle was 36.3\u00b0.\nThe 20 VA courses in the P group (12.5% of the total VA courses) were relatively close to the C7 Ep. HVA was present contralateral to the VA in 7 of 20 courses in the P group. CTA should be considered before proceeding with, even if, C7 PS instrumentation, to avoid unexpected pitfall.",
    "authors": [
        {
            "affiliation": "Department of Orthopaedic Surgery, The Jikei University School of Medicine Kashiwa Hospital, Kashiwashita 163-1, Kashiwa, Chiba, 2778567, Japan; Department of Orthopaedic Surgery, The Jikei University School of Medicine, Nishishimbashi 3-19-18, Minatoku, Tokyo, 1058471, Japan. Electronic address: chikara.u@gmail.com.",
            "firstname": "Chikara",
            "initials": "C",
            "lastname": "Ushiku"
        },
        {
            "affiliation": "Department of Orthopaedic Surgery, The Jikei University School of Medicine Kashiwa Hospital, Kashiwashita 163-1, Kashiwa, Chiba, 2778567, Japan; Department of Orthopaedic Surgery, The Jikei University School of Medicine, Nishishimbashi 3-19-18, Minatoku, Tokyo, 1058471, Japan.",
            "firstname": "Shigeru",
            "initials": "S",
            "lastname": "Soshi"
        },
        {
            "affiliation": "Department of Orthopaedic Surgery, The Jikei University School of Medicine, Nishishimbashi 3-19-18, Minatoku, Tokyo, 1058471, Japan.",
            "firstname": "Takeshi",
            "initials": "T",
            "lastname": "Inoue"
        },
        {
            "affiliation": "Department of Orthopaedic Surgery, The Jikei University School of Medicine, Nishishimbashi 3-19-18, Minatoku, Tokyo, 1058471, Japan.",
            "firstname": "Akira",
            "initials": "A",
            "lastname": "Shinohara"
        },
        {
            "affiliation": "Department of Orthopaedic Surgery, The Jikei University School of Medicine, Nishishimbashi 3-19-18, Minatoku, Tokyo, 1058471, Japan.",
            "firstname": "Kei",
            "initials": "K",
            "lastname": "Shinohara"
        },
        {
            "affiliation": "Department of Orthopaedic Surgery, The Jikei University School of Medicine, Nishishimbashi 3-19-18, Minatoku, Tokyo, 1058471, Japan.",
            "firstname": "Anri",
            "initials": "A",
            "lastname": "Ohkawa"
        },
        {
            "affiliation": "Department of Orthopaedic Surgery, The Jikei University School of Medicine, Nishishimbashi 3-19-18, Minatoku, Tokyo, 1058471, Japan.",
            "firstname": "Keishi",
            "initials": "K",
            "lastname": "Marumo"
        }
    ],
    "conclusions": "The 20 VA courses in the P group (12.5% of the total VA courses) were relatively close to the C7 Ep. HVA was present contralateral to the VA in 7 of 20 courses in the P group. CTA should be considered before proceeding with, even if, C7 PS instrumentation, to avoid unexpected pitfall.",
    "copyrights": "Copyright \u00a9 2020 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.",
    "doi": "10.1016/j.jos.2020.03.020",
    "journal": "Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association",
    "keywords": [],
    "methods": null,
    "publication_date": "2020-05-04",
    "pubmed_id": "32360078",
    "results": "The variant location of the VA to the C7 vertebra was A in 13 courses (8.1%), M in 123 (76.9%), and P in 20 (12.5%). HVA was present in the contralateral side in 7 of 20 courses (35%) in the P group, and in 8 of 127 courses (6.3%) in the M group (p\u00a0<\u00a00.05). The mean VED was 20.2\u00a0mm, the mean VEA 6.9\u00b0, and the mean PEA angle was 36.3\u00b0.",
    "title": "The position of the vertebral artery V1 segment relative to the C7 vertebra.",
    "xml": "<Element 'PubmedArticle' at 0x788504046750>"
}