title: Atlantoaxial instability in acute odontoid fractures is associated with nonunion and mortality.
abstract: BACKGROUND
  Odontoid fractures are the most common geriatric cervical spine fractures. Nonunion rates have been reported to be up to 40% and mortality up to 35%, and poor functional outcomes are common. Atlantoaxial instability (AAI) is a plausible prognostic factor, but its role has not been previously examined.
  
  
  OBJECTIVE
  To determine the effect of severe AAI on the outcomes of nonunion and mortality in patients with acute odontoid fractures.
  
  
  METHODS
  Retrospective cohort/single institution.
  
  
  METHODS
  One hundred twenty-four consecutive patients with acute odontoid fractures.
  
  
  METHODS
  Rates of nonunion and mortality.
  
  
  METHODS
  Two independent blinded reviewers measured AAI using postinjury computed tomography scans. Patients were classified as having "severe" or "minimal" AAI on the basis of greater versus less than or equal to 50% mean subluxation across each C1-C2 facet joint. Rates of nonunion and mortality were compared using independent samples t tests and adjusted for age, displacement, and subtype using binary logistic regression.
  
  
  RESULTS
  One hundred seven patients had minimal AAI and 17 had severe AAI. Mean follow-up was 4.4 months (standard deviation=4.6). Patients with severe AAI were more likely to experience nonunion (29% vs. 10%, respectively; p=.03) and mortality (35% vs. 14%, respectively; p=.03) regardless of treatment modality. Fracture displacement correlated with AAI (r(2)=0.65). When adjusted for patient age, the odds ratio of nonunion with severe AAI approached significance at 3.3 (95% confidence interval [CI]: 0.9-11.7). Mortality prediction with AAI approached a twofold increased risk (odds ratio=2.1; 95% CI: 0.6-6.8). In patients with Type-II fractures, the odds of mortality with severe AAI approached a threefold higher risk (odds ratio=3.3; 95% CI: 0.9-12.3).
  
  
  CONCLUSIONS
  Patients with acute odontoid fractures and severe AAI may be more likely to experience nonunion and mortality, suggesting the possibility that aggressive management could be warranted. Further investigation with a large prospective study including patient-important functional outcomes is justified.
authors.affiliation: Division of Orthopaedics, Department of Surgery, McMaster University, 293 Wellington St N, Suite 110, Hamilton, Ontario, Canada L8L 8E7. Electronic address: nathan.evaniew@medportal.ca.
authors.forename: Nathan
authors.initials: N
authors.lastname: Evaniew
authors.affiliation: Division of Neurosurgery, Department of Surgery, McMaster University, Hamilton General Hospital 8N-01, 237 Barton St E, Hamilton ON, L8L 2X2.
authors.forename: Blake
authors.initials: B
authors.lastname: Yarascavitch
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, 293 Wellington St N, Suite 110, Hamilton, Ontario, Canada L8L 8E7.
authors.forename: Kim
authors.initials: K
authors.lastname: Madden
authors.affiliation: Division of Orthopaedics, Department of Surgery, McMaster University, 293 Wellington St N, Suite 110, Hamilton, Ontario, Canada L8L 8E7.
authors.forename: Michelle
authors.initials: M
authors.lastname: Ghert
authors.affiliation: Division of Orthopaedics, Department of Surgery, McMaster University, 293 Wellington St N, Suite 110, Hamilton, Ontario, Canada L8L 8E7.
authors.forename: Brian
authors.initials: B
authors.lastname: Drew
authors.affiliation: Division of Orthopaedics, Department of Surgery, McMaster University, 293 Wellington St N, Suite 110, Hamilton, Ontario, Canada L8L 8E7; Department of Clinical Epidemiology and Biostatistics, McMaster University, 293 Wellington St N, Suite 110, Hamilton, Ontario, Canada L8L 8E7.
authors.forename: Mohit
authors.initials: M
authors.lastname: Bhandari
authors.affiliation: Division of Orthopaedics, Department of Surgery, McMaster University, 293 Wellington St N, Suite 110, Hamilton, Ontario, Canada L8L 8E7.
authors.forename: Desmond
authors.initials: D
authors.lastname: Kwok
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging* / Q000293:injuries; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging* / Q000401:mortality; D008297:Male; D008875:Middle Aged; D009809:Odontoid Process / Q000000981:diagnostic imaging* / Q000293:injuries; D011446:Prospective Studies; D011859:Radiography; D012189:Retrospective Studies; D016103:Spinal Fractures / Q000000981:diagnostic imaging / Q000401:mortality*; D016896:Treatment Outcome; D021801:Zygapophyseal Joint / Q000000981:diagnostic imaging* / Q000293:injuries
keywords: Cervical; Mortality; Nonunion; Odontoid; Spine; Trauma