title: Comparison of navigated versus non-navigated pedicle screw placement in 260 patients and 1434 screws: screw accuracy, screw size, and the complexity of surgery.
abstract: OBJECTIVE
  Computer 3D navigation (3D NAV) techniques in spinal instrumentation can theoretically improve screw placement accuracy and reduce injury to critical neurovascular structures, especially in complex cases. In this series, we analyze the results of 3D NAV in pedicle screw placement accuracy, screw outer diameter, and case complexity in comparison with screws placed with conventional lateral fluoroscopy.
  
  
  METHODS
  Pedicle screws placed in the cervical, thoracic, or lumbar spine using either standard lateral fluoroscopy or 3D NAV using isocentric fluoroscopy were retrospectively analyzed. The accuracy of each individual screw was graded on a 4-tiered classification system. Screw and pedicle diameter measurements were also made in both cohorts, and case complexity was compared between the 2 cohorts. Complex cases were defined as deformity surgery, re-do cases, and minimally invasive surgery.
  
  
  RESULTS
  A total of 708 screws were placed under 3D NAV guidance and 726 screws were placed without stereotaxy. Eighty-eight percent of 3D NAV-guided pedicle screws were graded nonbreach versus 82% of cases with lateral fluoroscopy (P<0.001). The ratio of screw/pedicle diameter was significantly larger in the 3D NAV cohort (0.71 vs. 0.63, P<0.05). Seventy-six percent of 3D NAV cases had a predefined aspect of complexity, whereas 44% of non-3D NAV cases met criteria to be labeled complex (P<0.001). Reoperation occurred less frequently in 3D NAV cases than fluoroscopy alone.
  
  
  CONCLUSIONS
  The use of 3D NAV was associated with improved screw placement accuracy, improved screw-to-pedicle diameter measurements, and was used in cases with a higher degree of surgical complexity. We conclude that 3D NAV is a valuable tool in current spinal instrumentation, especially for more complex surgeries.
authors.affiliation: Departments of *Neurological Surgery †Neuroradiology, Brain and Spine Center, Weill Cornell Medical College, New York, NY.
authors.forename: Neal
authors.initials: N
authors.lastname: Luther
authors.forename: J Bryan
authors.initials: JB
authors.lastname: Iorgulescu
authors.forename: Christian
authors.initials: C
authors.lastname: Geannette
authors.forename: Harry
authors.initials: H
authors.lastname: Gebhard
authors.forename: Tatianna
authors.initials: T
authors.lastname: Saleh
authors.forename: Apostolos J
authors.initials: AJ
authors.lastname: Tsiouris
authors.forename: Roger
authors.initials: R
authors.lastname: Härtl
mesh_terms: D001863:Bone Screws; D015331:Cohort Studies; D005471:Fluoroscopy; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D016268:Internal Fixators; D019637:Orthopedic Procedures / Q000379:methods*; D065289:Pedicle Screws; D012086:Reoperation; D012189:Retrospective Studies; D013131:Spine / Q000000981:diagnostic imaging / Q000601:surgery*; D013238:Stereotaxic Techniques; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed