title: Quantitative Gross and CT measurements of Cadaveric Cervical Vertebrae (C3 - C6) as Guidelines for the Lateral mass screw fixation.
abstract: BACKGROUND
  Lateral mass screw fixation is the treatment of choice for posterior cervical stabilization. Long or misdirected screws carry a risk of injury to spinal nerve roots or vertebral artery. This study was aimed to assess the gross anatomic and CT measurements of typical cervical vertebrae for the selection of lateral mass screws.
  
  
  METHODS
  Dimensions of the articular pillars were measured on 1) Dry cervical vertebrae with Vernier calipers and 2) Multiplanar reformations of CT scans of the same vertebrae with Viewer software package. The data was statistically evaluated.
  
  
  RESULTS
  The transverse diameter of the articular pillars with Vernier calipers varied from 6.0 to 15.4 mm (mean=10.5 mm ± 1.5) and on CT scans ranged from 8.2 - 16.1 mm (mean=11.6 mm ± 1.4). The antero-posterior diameter, an estimate of the screw length by Roy-Camille technique varied from 3.9 to 12.7 mm (mean=8.6 mm ± 1.6) by Vernier calipers and from 6.4 to 13.3 mm (mean=9.1 ± 1.2) on CT scans. The oblique AP diameter, an estimate of screw length by Magerl method varied from 10.8 to 20.3 mm (mean=14.9 mm ± 1.8) by Vernier calipers and from 11.4 to 19.3 mm (mean=14.5 mm ± 1.7) on CT. The CT measurements for height, transverse and AP diameter of the articular pillars were 0.5 - 1.0 mm larger than dimensions by Vernier calipers. No statistically significant difference was observed between the caliper and CT measurements for the oblique AP diameter.
  
  
  CONCLUSIONS
  CT measurements of the articular pillars may slightly overestimate the desired screw length selected by spine surgeons when compared to actual anatomy. Although means of the articular pillars correspond to the screw lengths used, substantial number of observations below 10 mm for Roy-Camille trajectory and below 14 mm for Magerl trajectory requires careful preoperative planning and intra-operative confirmation to avoid long/misdirected lateral mass screws.
authors.affiliation: Program in Anatomy and Body Visualization, Department of Radiology, Weill Cornell Medicine, New York, NY.
authors.forename: Santosh K
authors.initials: SK
authors.lastname: Sangari
authors.affiliation: Weill Cornell Medical College, New York, NY; Otolaryngology - Head and Neck Surgery, UCLA Health, Los Angeles, CA.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Heinneman
authors.affiliation: Weill Cornell Medical College, New York, NY.
authors.forename: Mathew S
authors.initials: MS
authors.lastname: Conti
authors.affiliation: Weill Cornell Medical College, New York, NY; Department of Orthopedic Surgery, Albany Medical Center Hospital, Albany, NY.
authors.forename: Paul-Michel F
authors.initials: PF
authors.lastname: Dossous
authors.affiliation: Weill Cornell Medical College, New York, NY.
authors.forename: David J
authors.initials: DJ
authors.lastname: Dillon
authors.affiliation: Department of Radiology, Neuroradiology section, New York-Presbyterian Hospital, Weill Cornell Medicine, New York, NY.
authors.forename: Apostolos J
authors.initials: AJ
authors.lastname: Tsiouris
authors.affiliation: Brain and Spine Center, NewYork-Presbyterian Hospital, Weill Cornell Medicine, New York, NY; Department of Neurosurgery, College of Medicine, Inje University, Busan Paik Hospital, Busan Korea.
authors.forename: Se Young
authors.initials: SY
authors.lastname: Pyo
authors.affiliation: Program in Anatomy and Body Visualization, Department of Radiology, Weill Cornell Medicine, New York, NY.
authors.forename: Estomih P
authors.initials: EP
authors.lastname: Mtui
authors.affiliation: Brain and Spine Center, NewYork-Presbyterian Hospital, Weill Cornell Medicine, New York, NY.
authors.forename: Roger
authors.initials: R
authors.lastname: Härtl
keywords: articular pillar; lateral mass screws; posterior fixation; typical cervical vertebra