title: Risk of internal carotid artery injury during C1 screw placement: analysis of 160 computed tomography angiograms.
abstract: BACKGROUND
  Injury to the internal carotid artery (ICA) is a potentially catastrophic complication of C1-lateral mass (C1-LM) or C1-C2 transarticular screw insertion.
  
  
  OBJECTIVE
  This study was designed to determine the risk of injury to the ICA during placement of these screws using computed tomography angiography (CTA).
  
  
  METHODS
  Radiographic analysis using CTA.
  
  
  METHODS
  One hundred sixty CTAs were examined, for a total of 320 ICAs.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Fine-cut intravenous CTAs with multiplanar and three-dimensional reconstruction were reviewed. The position of the ICA in relation to the anterior cortex (AC) of C1, anterior end of the anterior tubercle (AT), and medial margin of the transverse foramen (TF) was measured bilaterally in three ascending and equidistant levels of the C1-AT.
  
  
  RESULTS
  The position of the ICA in relation to C1 was variable. The average distance between the ICA and the AC of C1 was only 3.7 mm. Furthermore, 96% of the time the posterior margin of the ICA was located posterior to the anteriormost aspect of the anterior C1 tubercle (average distance, 5.4 mm), making the ICA vulnerable to damage if a drill, tap, or screw was inserted to the depth of the anteriormost portion of the AT as seen on a lateral fluoroscopic or radiographic view. The medial margin of the ICA was located medial to the TF (a location potentially vulnerable to injury with bicortical screw placement) less often at the caudal aspect of the C1-AT (54%) than at its middle or cranial aspect (74% and 75%, respectively). No ICAs were located anterior to the medial 30% of the C1-LM or more medially.
  
  
  CONCLUSIONS
  Bicortical C1-LM or C1-C2 transarticular screw placement carries a potential risk of ICA injury. Given the wide variation in ICA location relative to C1, if bicortical C1 fixation is required, preoperative CTA should be considered to determine the optimal screw trajectory. In general, inferomedially angulated C1-LM screws appear to be safer with respect to the ICA injury than other potential trajectories.
authors.affiliation: Spine Center and Department of Orthopaedic Surgery, Seoul National University College of Medicine and Seoul National University Bundang Hospital, 166 Gumiro, Bundang-ku, Sungnam 463-707, Republic of Korea.
authors.forename: Romel P
authors.initials: RP
authors.lastname: Estillore
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Buchowski
authors.forename: Do Van
authors.initials: do V
authors.lastname: Minh
authors.forename: Kun-Woo
authors.initials: KW
authors.lastname: Park
authors.forename: Bong-Soon
authors.initials: BS
authors.lastname: Chang
authors.forename: Choon-Ki
authors.initials: CK
authors.lastname: Lee
authors.forename: K Daniel
authors.initials: KD
authors.lastname: Riew
authors.forename: Jin S
authors.initials: JS
authors.lastname: Yeom
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography; D001268:Atlanto-Axial Joint / Q000601:surgery; D001863:Bone Screws / Q000009:adverse effects*; D002339:Carotid Arteries / Q000000981:diagnostic imaging*; D020212:Carotid Artery Injuries / Q000000981:diagnostic imaging* / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D013123:Spinal Fusion / Q000009:adverse effects*; D055815:Young Adult