title: Accurate and Simple Screw Insertion Procedure With Patient-Specific Screw Guide Templates for Posterior C1-C2 Fixation.
abstract: METHODS
  Prospective clinical trial of the screw insertion method for posterior C1-C2 fixation utilizing the patient-specific screw guide template technique.
  
  
  OBJECTIVE
  To evaluate the efficacy of this method for insertion of C1 lateral mass screws (LMS), C2 pedicle screws (PS), and C2 laminar screws (LS).
  
  
  BACKGROUND
  Posterior C1LMS and C2PS fixation, also known as the Goel-Harms method, can achieve immediate rigid fixation and high fusion rate, but the screw insertion carries the risk of injury to neuronal and vascular structures. Dissection of venous plexus and C2 nerve root to confirm the insertion point of the C1LMS may also cause problems. We have developed an intraoperative screw guiding method using patient-specific laminar templates.
  
  
  METHODS
  Preoperative bone images of computed tomography (CT) were analyzed using three-dimensional (3D)/multiplanar imaging software to plan the trajectories of the screws. Plastic templates with screw guiding structures were created for each lamina using 3D design and printing technology. Three types of templates were made for precise multistep guidance, and all templates were specially designed to fit and lock on the lamina during the procedure. Surgery was performed using this patient-specific screw guide template system, and placement of the screws was postoperatively evaluated using CT.
  
  
  RESULTS
  Twelve patients with C1-C2 instability were treated with a total of 48 screws (24 C1LMS, 20 C2PS, 4 C2LS). Intraoperatively, each template was found to exactly fit and lock on the lamina and screw insertion was completed successfully without dissection of the venous plexus and C2 nerve root. Postoperative CT showed no cortical violation by the screws, and mean deviation of the screws from the planned trajectories was 0.70 ± 0.42 mm.
  
  
  CONCLUSIONS
  The multistep, patient-specific screw guide template system is useful for intraoperative screw navigation in posterior C1-C2 fixation. This simple and economical method can improve the accuracy of screw insertion, and reduce operation time and radiation exposure of posterior C1-C2 fixation surgery.
  
  
  METHODS
  3.
authors.affiliation: Department of Spinal Surgery, Research Institute for Brain and Blood Vessels Akita, Akita, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Sugawara
authors.affiliation: Department of Spinal Surgery, Research Institute for Brain and Blood Vessels Akita, Akita, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Higashiyama
authors.affiliation: Department of Orthopaedic Surgery, Kobe Rosai Hospital, Kobe, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kaneyama
authors.affiliation: Department of Orthopaedic Surgery, Kobe Rosai Hospital, Kobe, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Sumi
mesh_terms: D000328:Adult; D000368:Aged; D001268:Atlanto-Axial Joint / Q000601:surgery*; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000601:surgery*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007593:Joint Instability / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D065289:Pedicle Screws; D011446:Prospective Studies; D013123:Spinal Fusion / Q000379:methods