title: Modification of C1-C2 transarticular screw fixation by image-guided surgery.
abstract: METHODS
  This is a feasibility study of image-guided surgery for C1-C2 transarticular screw fixation comparing postoperative screw position in a nonrandomized prospective cohort with a historic control group in which fluoroscopic guidance was used alone.
  
  
  OBJECTIVE
  To evaluate the potential benefits and disadvantages of image-guided surgery for C1-C2 screw placement.
  
  
  BACKGROUND
  C1-C2 transarticular screw fixation is biomechanically superior to other current surgical stabilization procedures. The original technique for C1-C2 screw placement relies on anatomic landmarks and intraoperative fluoroscopy. Screw misplacement or anatomic variations can result in vertebral artery injury. Image-guided surgery involves using computed tomography (CT) data to plan the optimal screw trajectory before surgery and then use this data to guide screw placement during the actual surgery. Promising results of this technique are reported in the literature, but no direct comparison between image-guided surgery and conventional surgical techniques has been previously reported.
  
  
  METHODS
  The image-guided surgery group consisted of 37 prospective patients. The historic control group included 78 patients who had similar surgeries performed using only fluoroscopic guidance. For the image-guided surgery group, subluxation was reduced by positioning at the time of CT examination. The CT data were transferred to a StealthStation (Sofamor-Danek, Memphis, TN) surgical planning and guidance computer system, and an optimal screw trajectory was determined for the right and left transarticular screws. After matching the surgical field to the virtual computer field, C2 was drilled according to the planned screw trajectory, and screws were placed. Plain radiographs and CT were used for postoperative evaluation of the image-guided surgery group.
  
  
  RESULTS
  Image-guided surgery reduced but did not eliminate the risk of screw misplacement. Surgical time was not increased overall.
  
  
  CONCLUSIONS
  Image-guided surgery is an effective tool for the achievement of correct screw placement in C1-C2 transarticular screw fixation procedures. The procedure remains technically demanding.
authors.affiliation: Spine Center Osnabrück, Osnabrück, Germany. spine.osib@t-online.de
authors.forename: A
authors.initials: A
authors.lastname: Weidner
authors.forename: M
authors.initials: M
authors.lastname: Wähler
authors.forename: S T
authors.initials: ST
authors.lastname: Chiu
authors.forename: C G
authors.initials: CG
authors.lastname: Ullrich
mesh_terms: D001368:Axis, Cervical Vertebra / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D001863:Bone Screws / Q000009:adverse effects / Q000592:standards*; D001270:Cervical Atlas / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D015331:Cohort Studies; D005260:Female; D005471:Fluoroscopy / Q000009:adverse effects / Q000706:statistics & numerical data; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects / Q000592:standards*; D007431:Intraoperative Complications / Q000453:epidemiology / Q000209:etiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D016896:Treatment Outcome; D014584:User-Computer Interface