title: Accuracy and complications of posterior C2 screw fixation using intraoperative three-dimensional fluoroscopy-based navigation.
abstract: BACKGROUND
  The peculiar and highly variable C2 anatomy can make screw fixation more challenging and prone to potential vertebral artery or neurologic injury. Conventional C-arm fluoroscopy has several drawbacks. The aim of this research was to evaluate the accuracy of posterior C2 screw fixation using intraoperative three-dimensional fluoroscopy-based navigation (ITFN) and assess the perioperative complication rate related to screw placement.
  
  
  METHODS
  A retrospective review identified patients who underwent operative management with C2 instruments using ITFN at our hospital between January 2006 and December 2012. Clinical data were obtained from medical records and final screw positions were graded according to a modified classification of Gertzbein and Robbins. Grade A and B screws were considered well positioned.
  
  
  RESULTS
  The study included 99 patients (53 males and 46 females) who underwent posterior C2 screw fixation using ITFN. The mean Japan Orthopedic Association score improved from (6.7 ± 1.9) points before surgery to (12.5 ± 2.7) points at 6-month follow-up (z = +8.628, P < 0.01). The mean visual analogue scale improved from (4.1 ± 1.2) points before surgery to (0.7 ± 0.9) points at 6-month follow-up, with an improvement of 83.7% (z = 8.638, P < 0.01). Of the 196 screws analyzed using computed tomography and chart review, 126 transarticular, 64 pedicle, and 6 pars screws were placed with 82.5% (104/126), 89.1% (57/64), and 100% (6/6) accuracy (grade A), respectively; 98.5% (193/196) of screws were grade A or B (grade C, 1.5% (3/196)), and no neurologic injuries occurred. In normal C2 cases, 93 transarticulars and 47 pedicles were placed with high accuracy rates of 90.3% (84/93) and 93.6% (44/47) (grade A), respectively. However, in cases with C2 deformity, 33 transarticular, 17 pedicle, and 6 pars screws were placed with only 60.6% (20/33), 76.5% (13/17), and 100% (6/6) accuracy (grade A), respectively.
  
  
  CONCLUSIONS
  ITFN is a safe, accurate, and effective tool for posterior C2 fixation.
authors.affiliation: Department of Spine Surgery, Beijing Jishuitan Hospital, Peking University Fourth Clinical Medical College, Beijing 100035, China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Tao
authors.affiliation: Department of Spine Surgery, Beijing Jishuitan Hospital, Peking University Fourth Clinical Medical College, Beijing 100035, China. Email: pumctaotao@yeah.net.
authors.forename: Wei
authors.initials: W
authors.lastname: Tian
authors.affiliation: Department of Spine Surgery, Beijing Jishuitan Hospital, Peking University Fourth Clinical Medical College, Beijing 100035, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.affiliation: Department of Spine Surgery, Beijing Jishuitan Hospital, Peking University Fourth Clinical Medical College, Beijing 100035, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Spine Surgery, Beijing Jishuitan Hospital, Peking University Fourth Clinical Medical College, Beijing 100035, China.
authors.forename: Guilin
authors.initials: G
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001863:Bone Screws / Q000009:adverse effects*; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D055815:Young Adult