title: Atlantoaxial transarticular screw fixation for a high-riding vertebral artery.
abstract: METHODS
  The feasibility of inserting a screw for the narrow isthmus with a high-riding vertebral artery was evaluated in patients subjected to posterior atlantoaxial transarticular screw fixation.
  
  
  OBJECTIVE
  To demonstrate the feasibility of inserting bilateral screws and obtaining a stable atlantoaxial complex for patients with a high-riding vertebral artery.
  
  
  BACKGROUND
  Posterior atlantoaxial transarticular screw fixation entails the potential risk of vertebral artery injury, which may be lethal. The risk is much higher for the narrow isthmus caused by a high-riding vertebral artery, and many authors recommend that the procedure should be abandoned if the isthmus is too narrow. On the other hand, bilateral screw fixation is stronger than unilateral screw fixation.
  
  
  METHODS
  For this study 27 consecutive patients who submitted to atlantoaxial transarticular screw fixation were evaluated before surgery for the position of the vertebral artery grooves using computed tomography (CT) reconstruction. Seven of the patients were defined as having a unilateral high-riding vertebral artery. For these patients, bilateral screw insertion through the most posterior and medial part of the isthmus was performed.
  
  
  RESULTS
  No massive bleeding or major complications were encountered in any patients with a high-riding vertebral artery. Postoperative computed tomography reconstruction demonstrated that five of the screws cleared the vertebral artery groove successfully, and two slightly breached it. No screws penetrated into the vertebral artery groove.
  
  
  CONCLUSIONS
  It is possible to insert a screw safely, even into the narrow isthmus with a high-riding vertebral artery, if the surgeon realizes where the screw should be inserted and has the requisite insertion technique. Bilateral screw fixation should provide a high fusion rate.
authors.affiliation: Department of Orthopaedic Surgery, Kyoto University Graduate School of Medicine, Japan. neo@kuhp.kyoto-u.ac.jp
authors.forename: Masashi
authors.initials: M
authors.lastname: Neo
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Matsushita
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Iwashita
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yasuda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D002648:Child; D005240:Feasibility Studies; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment; D012307:Risk Factors; D013122:Spinal Diseases / Q000601:surgery*; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D014711:Vertebral Artery / Q000033:anatomy & histology / Q000000981:diagnostic imaging