title: Novel Landmark for Cervical Pedicle Screw Insertion Point from Computed Tomography-Based Study.
abstract: METHODS
  Cross-sectional study.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate a novel landmark for the cervical pedicle screw insertion point.
  
  
  BACKGROUND
  To improve the accuracy of pedicle screw placement, several studies have employed the lateral mass, lateral vertical notch, and/or inferior articular process as landmarks; however, we often encounter patients in whom we cannot identify accurate insertion points for pedicle screws using these landmarks because of degenerative changes in the facet joints. The superomedial edge of the lamina is less affected by degenerative changes, and we hypothesized that it could be a new landmark for identifying an accurate cervical pedicle screw insertion point.
  
  
  METHODS
  A total of 327 consecutive patients, who had undergone neck computed tomographic scanning for determination of neck disease in our institute, were included in the study. At first, the line was drawn parallel to the superior border of the pedicle in the sagittal plane and parallel to the vertical body in the coronal plane. The line was moved downward in 1-mm increments to the inferior border of the pedicle. We determined whether the line passing through the superomedial edge of the lamina (termed the "N-line") was located between the superior and inferior borders of the pedicle in the sagittal plane.
  
  
  RESULTS
  The percentages of N-lines located between the superior and inferior borders of the pedicle were 100% at C3, 100% at C4, 99% at C5, 96% at C6, and 97% at C7. The lower cervical spine has the higher N-line location.
  
  
  CONCLUSIONS
  The N-line was frequently located at the level of the pedicle of each cervical spine in the sagittal plane. The superomedial edge of the lamina could be a new landmark for the insertion point of the cervical pedicle screw.
authors.affiliation: Department of Orthopaedic Surgery, Shiga University of Medical Science, Otsu, Japan.
authors.forename: Kazuya
authors.identifier: 0000-0001-5992-2390
authors.initials: K
authors.lastname: Nishizawa
authors.affiliation: Department of Orthopaedic Surgery, Shiga University of Medical Science, Otsu, Japan.
authors.forename: Kanji
authors.identifier: 0000-0002-1975-2339
authors.initials: K
authors.lastname: Mori
authors.affiliation: Department of Orthopaedic Surgery, Shiga University of Medical Science, Otsu, Japan.
authors.forename: Akira
authors.identifier: 0000-0002-1481-7965
authors.initials: A
authors.lastname: Nakamura
authors.affiliation: Department of Orthopaedic Surgery, Shiga University of Medical Science, Otsu, Japan.
authors.forename: Shinji
authors.identifier: 0000-0002-4548-9853
authors.initials: S
authors.lastname: Imai
keywords: Cervical spine; Novel landmark; Pedicle screws; Superomedial edge of lamina; X-ray computed tomography