title: An anatomic consideration of C2 vertebrae artery groove variation for individual screw implantation in axis.
abstract: METHODS
  Retrospective case series.
  
  
  OBJECTIVE
  To identify the variation of C2 vertebral artery groove (VAG) based on the thin-slice computed tomography (CT) scan and choose an individual screw placement method to decrease risk of malposition.
  
  
  BACKGROUND
  C2 pedicle screws can be successful anchors for a variety of cervical disorders. However, variations of VAG may cause malposition and breach when C2 transpedicle screw was inserted. Recognizing the variations of vertebrae artery groove (VAG) in C2 and choosing an individual screw placement method (transpedicle or translaminar) may be helpful for avoiding violation and decreasing the operation risk in upper cervical surgery.
  
  
  METHODS
  From January 2009 to December 2010, a total 45 patients with upper cervical disorders underwent 1-mm-thin-slice CT scans along the C2 pedicle direction to obtain the consecutive spectrum of C2 VAG were included in this study. The C2 VAG (types I, II, III, and IV) was subgrouped based on parameter e (the vertical distance from the apex of VAG to the upper facet joint surface) and parameter a (horizontal distance from the entrance of VAG to the vertebrae canal). Subsequently, individual strategy was used to avoid the VAG violation.
  
  
  RESULTS
  The variations of C2 VAG in these 45 patients include the following: type I 53 (58.9%), type II 16 (17.8%) type III 13 (14.4%), and type IV 8 (8.9%). Transpedicle screws of C2 were used in types I, III, and IV VAGs (n = 74); translaminar screws were inserted in type II subgroup (n = 16). Postoperative CT scans showed that there were two pedicle screws violated into the artery groove, and no translaminar screw breached into the vertebrae canal. All the other screws were in right position. None of the 45 patients had severe complications such as spinal cord injury, dura tear, and infection.
  
  
  CONCLUSIONS
  Thin-slice CT scan along the C2 pedicle direction to analysis the variations of C2 VAG can help choose an individual screw placement method (transpedicle or translaminar) with minimal complication for C2 screw fixation.
authors: Department of Orthopaedic Surgery, Liu Hua Qiao Hospital (General Military Hospital of Guangzhou Command), 111 Liuhua Road, Yuexiu District, 510010 Guangzhou, China. janhuawangddrr@163.com
authors: Janhua
authors: J
authors: Wang
authors: Hong
authors: H
authors: Xia
authors: Qingshui
authors: Q
authors: Ying
authors: Yang
authors: Y
authors: Lu
authors: Zenghui
authors: Z
authors: Wu
authors: Fzhi
authors: F
authors: Ai
authors: Xiangyang
authors: X
authors: Ma
mesh_terms: D000293:Adolescent; D000328:Adult; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000098:blood supply* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed; D014711:Vertebral Artery / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D055815:Young Adult
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