Letter to the Editor Concerning “Feasibility of C2 Pedicle Screw Fixation with the “in-out-in” Technique for Patients with Basilar Invagination”

aDepartment of Orthopedics and Spine Surgery, the First Affiliated Hospital of Anhui Medical University, Hefei, Anhui 230022, China bLaboratory of Spinal and Spinal Cord Injury Regeneration and Repair, the First Affiliated Hospital of Anhui Medical University, Hefei, Anhui 230022, China Lu-Ping Zhou, Ren-Jie Zhang: These authors contributed equally to the work and should be regarded as co-first authors. Funding: No funding was obtained for this study. Authors' contributions: Lu-Ping Zhou and Ren-Jie Zhang are co-first authors of this manuscript. Cai-Liang Shen proposed the points and Lu-Ping Zhou wrote the manuscript. Lu-Ping Zhou and Ren-Jie Zhang revised the manuscript and decided to submit the manuscript for publication. All authors read and approved the final manuscript. All authors agreed to be accountable for all aspects of the work. Abbreviations: BI, basilar invagination; LPD, the distance from the lateral cortex of the C2 pedicle to the dura; LPSC, the distance from the lateral cortex of the C2 pedicle to the spinal cord; LPTF, the sum of LPVA and the transverse foramen; LPVA, the distance from the lateral cortex of the C2 pedicle to the vertebral artery; MPD, the distance from the medial cortex of the C2 pedicle to the dura; MPSC, the distance from the medial cortex of the C2 pedicle to the spinal cord; MPTF, the sum of MPVA and the transverse foramen; MPVA, the distance from the medial cortex of the C2 pedicle to the vertebral artery; PW, pedicle width. Competing interests: All authors read and approved the final manuscript and declare that they have no competing interests. Address correspondence and reprint requests to Cai-Liang Shen, PhD, Department of Orthopedics and Spine Surgery, the First Affiliated Hospital of Anhui Medical University, 218 Jixi Road, Hefei, Anhui 230022, China. Laboratory of Spinal and Spinal Cord Injury Regeneration and Repair, the First Affiliated Hospital of Anhui Medical University, 218 Jixi Road, Hefei, Anhui 230022, China; E-mail: [email protected]