title: Risk factors for intraoperative lateral mass fracture of lateral mass screw fixation in the subaxial cervical spine.
abstract: OBJECTIVE
  Although lateral mass screw fixation for the cervical spine is a safe technique, lateral mass fracture during screw fixation is occasionally encountered intraoperatively. This event is regarded as a minor complication; however, it poses difficulties in management that may affect fixation stability and clinical outcome. The purpose of this study is to determine the incidence and etiology of lateral mass fractures during cervical lateral mass screw fixation.
  
  
  METHODS
  A retrospective clinical review of patient records was performed in 117 consecutive patients (mean age 57 years, range 15-86 years) who underwent lateral mass screw fixation using a modified Magerl method from 1997 to 2010 at a single institution. A total of 555 lateral masses were included in this study. The outer diameters of the screws were 3.5 or 4.0 mm. In the retrospective clinical analysis, the incidence of intraoperative lateral mass fractures was reviewed. Potential risk factors for this complication were assessed using multivariate analysis.
  
  
  RESULTS
  The incidence of lateral mass fractures during cervical lateral mass screw fixation was 4.7% (26 lateral masses) among all cases. Among the disorders, the incidence was highest in patients with destructive spondyloarthropathy (DSA) (18.8%, 12 lateral masses). There was no significant difference with respect to lateral mass fracture between the use of 4.0-mm screws (5.6%) and 3.5-mm screws (3.6%). Independent risk factors identified by logistic regression were DSA (OR 7.89, p < 0.001) and screw insertion in the C-6 lateral masses (OR 2.80, p = 0.018).
  
  
  CONCLUSIONS
  The overall incidence of lateral mass fracture during cervical lateral mass screw fixation was 4.7%. Destructive spondyloarthropathy as an underlying cause of morbidity and screw placement in the C-6 lateral mass were identified as independent risk factors. Use of a 4.0-mm screw in patients with DSA may be a principal risk factor for this complication.
authors.affiliation: Department of Orthopaedic Surgery, Hyogo College of Medicine, Nishinomiya, Japan.
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 / Q000293:injuries* / Q000601:surgery; D005260:Female; D006801:Humans; D007431:Intraoperative Complications / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D017887:Ossification of Posterior Longitudinal Ligament / Q000601:surgery; D012307:Risk Factors; D016103:Spinal Fractures / Q000209:etiology*; D013123:Spinal Fusion / Q000009:adverse effects*; D025242:Spondylarthropathies / Q000601:surgery; D055009:Spondylosis / Q000601:surgery; D016896:Treatment Outcome