title: The Vertebral Artery Cave at C2: Anatomic Study with Application to C2 Pedicle Screw Placement.
abstract: OBJECTIVE
  Knowledge of the course of the vertebral artery during instrumentation is of paramount importance. It has been shown that erosion of the C2 pedicle and body can occur due to pulsations of the adjacent vertebral artery. This often results in a "cave" for this segment of the artery. The descriptions of this anatomy are limited. The current study was performed with the hope that these data will be of use to spine surgeons during C2 instrumentation.
  
  
  METHODS
  In 40 human adult C2 bone specimens, the position of the vertebral artery in relation to the undersurface of the superior articular facet, pedicle, and C2 body was observed. A classification system was used to better describe these relationships. Pedicle screws were then placed into selected examples of each type.
  
  
  RESULTS
  We found type 0 specimens, with no cave, on 8 sides (10%). Types I, II, and III caves with minimal, moderate, and significant encroachment of the pedicle were observed on 40%, 35%, and 27.5% sides, respectively. Type IV caves with erosion into the lateral C2 body and undersurface of the superior articular facet were observed on 12.5% of sides. Although larger caves were found on left sides, this did not reach statistical significance. Pedicle screw placement for types III and IV were most likely to enter the vertebral artery cave (P < 0.05).
  
  
  CONCLUSIONS
  Additional osteologic data regarding the course of the vertebral artery while within C2 may decrease morbidity during surgery in this region.
authors.affiliation: Seattle Science Foundation, Seattle, Washington, USA.
authors.forename: R Shane
authors.initials: RS
authors.lastname: Tubbs
authors.affiliation: Seattle Science Foundation, Seattle, Washington, USA.
authors.forename: Andre
authors.initials: A
authors.lastname: Granger
authors.affiliation: Seattle Science Foundation, Seattle, Washington, USA; Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA. Electronic address: christian.fisahn@gmail.com.
authors.forename: Christian
authors.initials: C
authors.lastname: Fisahn
authors.affiliation: Department of Anatomical Sciences, St. George's University, Grenada.
authors.forename: Marios
authors.initials: M
authors.lastname: Loukas
authors.affiliation: Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA.
authors.forename: Marc
authors.initials: M
authors.lastname: Moisi
authors.affiliation: Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA.
authors.forename: Joe
authors.initials: J
authors.lastname: Iwanaga
authors.affiliation: Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA.
authors.forename: David
authors.initials: D
authors.lastname: Paulson
authors.affiliation: Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA.
authors.forename: Shiveindra
authors.initials: S
authors.lastname: Jeyamohan
authors.affiliation: Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA.
authors.forename: Jens R
authors.initials: JR
authors.lastname: Chapman
authors.affiliation: Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA.
authors.forename: Rod J
authors.initials: RJ
authors.lastname: Oskouian
mesh_terms: D059925:Anatomic Landmarks / Q000033:anatomy & histology / Q000601:surgery; D002102:Cadaver; D002574:Cervical Vertebrae / Q000033:anatomy & histology* / Q000601:surgery*; D006801:Humans; D065289:Pedicle Screws; D019919:Prosthesis Implantation / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014711:Vertebral Artery / Q000033:anatomy & histology* / Q000601:surgery*
keywords: Anatomy; Axis; Complications; Spine; Surgery