title: Cervical lateral mass screw fixation without fluoroscopic control: analysis of risk factors for complications associated with screw insertion.
abstract: OBJECTIVE
  To examine the outcome of cervical lateral mass screw fixation focusing on analysis of the risk factors for screw-related complications.
  
  
  METHODS
  Ninety-four patients who underwent posterior cervical fixation with a total of 457 lateral mass screws were included in the study. The lateral mass screws were placed using a modified Magerl method. Computed tomographic (CT) images were taken in the early postoperative period in all patients, and the screw trajectory angle was measured on both axial and sagittal plane images.
  
  
  RESULTS
  In the postoperative CT analysis for the screw trajectory, 56.5 % of the screws were directed within the acceptable range (within 21-40° on both axial and sagittal planes). As intraoperative screw-associated complications, 9.6 % of the screws were found to contact with or breach the vertebral artery foramen. In this group, the screw trajectory angle on axial plane was significantly lower than in the group without contact. Facet violation was observed in 13 screws (2.8 %). This complication was associated with a significantly lower trajectory angles in the sagittal plane, predominantly at C6 level (69.2 %). In the patient chart review, no serious neurovascular injuries were documented.
  
  
  CONCLUSIONS
  In the analysis of potential risk factors for violation of the VA foramen as well as FV during screw insertion, the former incidence was significantly related to the screw trajectory angle (lack of lateral angulation) in the axial plane, while the latter incidence was related to a poor screw trajectory angle in the sagittal plane.
authors.affiliation: Department of Orthopaedic Surgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, Japan. inoshin@hyo-med.ac.jp
authors.forename: Shinichi
authors.initials: S
authors.lastname: Inoue
authors.forename: Tokuhide
authors.initials: T
authors.lastname: Moriyama
authors.forename: Toshiya
authors.initials: T
authors.lastname: Tachibana
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Okada
authors.forename: Keishi
authors.initials: K
authors.lastname: Maruo
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Horinouchi
authors.forename: Shinichi
authors.initials: S
authors.lastname: Yoshiya
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001863:Bone Screws / Q000009:adverse effects*; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000293:injuries / Q000601:surgery*; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D015641:Radiography, Interventional; D012189:Retrospective Studies; D012307:Risk Factors; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed; D055815:Young Adult