title: Does Navigation Improve Accuracy of Placement of Pedicle Screws in Single-level Lumbar Degenerative Spondylolisthesis?: A Comparison Between Free-hand and Three-dimensional O-Arm Navigation Techniques.
abstract: METHODS
  This was a prospective, nonrandomized study.
  
  
  OBJECTIVE
  To assess the accuracy of O-arm navigation-based pedicle screw insertion in lumbar degenerative spondylolisthesis and to compare it with free-hand pedicle screw insertion technique in matched population.
  
  
  BACKGROUND
  O-arm navigation is latest in navigation technology that can provide real-time intraoperative images in 3 dimensions while placing the pedicle screws to improve intraoperative pedicle screw accuracy. Degenerative lumbar spondylolisthesis is a locally unstable pathology and placement of pedicle screws can cause increased rotation and translation of the vertebral body. However, is this motion detected by the tracker placed across the unstable segment, is a matter of debate. Inability to detect these positional changes can lead to pedicle perforation while inserting screws using navigation. No study has evaluated the role of O-arm navigation in this patient population.
  
  
  METHODS
  The study population was divided into 2 groups with 19 patients each, one comprising patients who underwent O-arm navigation-based pedicle screw insertion (group 1) and the other comprising patients who underwent free-hand pedicle screw insertion technique (group 2). A total of 152 pedicle screws were implanted in 38 patients for 1-level instrumented fusion for degenerative lumbar spondylolisthesis. Intraoperative 3-dimensional computed tomography scans using the O-arm were obtained for all patients after insertion of pedicle screws. The images were reviewed intraoperatively and postoperatively for the analysis of pedicle breaches. Assessments in either of the group included (i) accuracy of placement of screws; (ii) the rate and direction of perforation; and (iii) the number of segments the perforated screw was away from the navigation tracker.
  
  
  RESULTS
  Mean age of patients in group 1 (O-arm navigation-assisted) was 60 years (SD 11.25; range, 37-73 y), whereas in group 2 (free-hand pedicle screw) was 62 years (SD 18.07; range, 36-90 y). Overall anatomic perforation rate was 12.5% (19/152). Individually, group 1 had 14.47% (11/76) of perforations in comparison with 10.53% (8/76) observed in group 2. The difference was not statistically significant. The lateral margin was the most common site of perforation in both group 1 (64%, 7/11) and group 2 (62.5%, 5/8). Functional perforation rate for the series was 3.3% (5/152), with group 1 having 2.63% (2/76) and group 2 having 3.95% (3/76). The rate of perforation (PR) was significantly higher statistically when the tracker was placed 3 or more [PR 37.5% (6/16)] spinal segments away from instrumented segment compared with when it was placed 1 (0%) or 2 [PR 13.89% (5/36)] spinal segments away. Overall, 11 screws (11/152, 7.24%) had grade 2 perforations and had to be revised. No neurological complications were observed in the series.
  
  
  CONCLUSIONS
  O-arm navigation does not provide any significant advantage over conventional free-hand pedicle screw insertion technique in patients with single-level degenerative spondylolisthesis. The accuracy is dependent on the distance of the tracker from the level of instrumentation. Lateral perforations are more common because of instability at the instrumented level leading to translation and rotation of the vertebral body while placing pedicle screws leading to preferential lateral trajectory. These lateral perforations could not be prevented by using navigation. However, no significant complications were noted in either technique.
authors: *Department of Orthopedic Surgery, Spine Service, Singapore General Hospital, Bukit Merah, Singapore †Center for Spinal Studies and Surgery, Queens Medical Center, Nottingham University Hospital NHS Trust, Nottingham, UK.
authors: Benjamin Phak
authors: BP
authors: Boon Tow
authors: Wai Mun
authors: WM
authors: Yue
authors: Abhishek
authors: A
authors: Srivastava
authors: Jenn Ming
authors: JM
authors: Lai
authors: Chang Ming
authors: CM
authors: Guo
authors: Benedict Chan
authors: BC
authors: Wearn Peng
authors: John L T
authors: JL
authors: Chen
authors: Andy K S
authors: AK
authors: Yew
authors: Chusheng
authors: C
authors: Seng
authors: Seang Beng
authors: SB
authors: Tan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001132:Arm; D005260:Female; D006225:Hand; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods*; D065289:Pedicle Screws; D011446:Prospective Studies; D013168:Spondylolisthesis / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed