title: Pedicle violation and Navigational errors in pedicle screw insertion using the intraoperative O-arm: A preliminary report.
abstract: BACKGROUND
  Use of computer-assisted insertion of pedicle screws has some advantages owing to the reportedly decreased incidence of pedicle breach and clinical events. Registration-based methods based on preoperative computed tomography imaging, 2D fluoroscopy, and 3D fluoroscopy are the most popular, however each has its limitations. O-arm-based navigation, which uses intraoperative acquisition and registration of navigated images, may overcome many of these disadvantages. We set out to study the clinical accuracy and navigational accuracy for pedicle screw insertion using our recently acquired O-arm and present our preliminary findings.
  
  
  METHODS
  The first 26 patients operated consecutively for L4-5 fusion were included in the study. O-arm-based navigation was used to insert the pedicle screws. Postoperative computed tomography images were acquired and assessed for pedicle breach and anterior cortical perforation. Planned trajectories of each screw were compared with the actual trajectories in the postoperative images to assess navigational accuracy in both axial and sagittal planes.
  
  
  RESULTS
  A total of 104 screws were inserted. One screw (1%) breached the pedicle laterally. Nonsignificant anterolateral cortical perforations were noted in 7 screws (6.7%), all of which occurred at L5 level. The mean axial and sagittal navigational error was 2.3° (±1.7) and 3.1° (±2.3), respectively. There were no significant differences in the errors between L4 or L5 level. The occurrence of anterior perforation correlated with the degree of axial (P = .02) but not sagittal (P = .12) navigational error. There were no clinical events related to the screw insertion.
  
  
  CONCLUSIONS
  Use of O-arm-guided pedicle screw insertion was associated with low incidence of pedicle breach (1%) and a low range of navigational error in both sagittal and axial planes. Anterolateral vertebral body perforation was higher at L5 without any negative clinical events. Despite the high need for technical support, we found that O-arm was a very efficient tool for accurate pedicle screw insertion.
authors.affiliation: Department of Orthopedics, Montreal General Hospital, Montreal, Quebec, Canada.
authors.forename: Jacob E
authors.initials: JE
authors.lastname: Mathew
authors.affiliation: Neuronavigation, Montreal Neurological Institute, Montreal, Quebec, Canada.
authors.forename: Kelvin
authors.initials: K
authors.lastname: Mok
authors.affiliation: Neurosurgery, Montreal Neurological Institute, Montreal, Quebec, Canada.
authors.forename: Benoit
authors.initials: B
authors.lastname: Goulet
keywords: Clinical accuracy; Computer-assisted navigation; Navigational accuracy; O-arm; Pedicle screw