title: Proposal of a modified, treatment-oriented classification of odontoid fractures.
abstract: BACKGROUND
  The classification scheme of odontoid fractures described by Anderson and D'Alonzo is the one most commonly used. However, uncertainty exists in the distinction between Type II and "shallow" Type III fractures. Moreover, fractures at the base of the odontoid (Anderson and D'Alonzo Type II) include a spectrum of injury patterns.
  
  
  OBJECTIVE
  To modify the Anderson and D'Alonzo classification of odontoid fractures based on current clinical treatment options.
  
  
  METHODS
  Proposal of a modified classification system for odontoid fractures.
  
  
  METHODS
  A more precise distinction between Type II and III fractures based on the presence/absence of C1-C2 facet involvement is proposed. A modified classification of Type II fractures based on fracture line obliquity, displacement and comminution is then proposed, because these are factors deemed to influence management. To evaluate the reproducibility of this classification, 52 odontoid fractures were reviewed and classified by four attending spine surgeons and three spine fellows.
  
  
  RESULTS
  There was substantial agreement (at least five of seven respondents) in 70% of cases. The overall kappa value for the modified classification system was 0.48, indicating moderate agreement, and there were no differences in kappa values between attending spine surgeons and fellows.
  
  
  CONCLUSIONS
  The reproducibility of this system was demonstrated by the moderate agreement observed when applied to odontoid fractures at our institution. The proposed utility of this system is its ability to guide clinical decision making in the treatment of odontoid fractures. Prospective application of this modified classification system and suggested treatment options is now required.
authors.affiliation: Rothman Institute at Thomas Jefferson University, 925 Chestnut St., Philadelphia, PA 19107-4216, USA. jonathan.grauer@yale.edu
authors.forename: Jonathan N
authors.initials: JN
authors.lastname: Grauer
authors.forename: Bilal
authors.initials: B
authors.lastname: Shafi
authors.forename: Alan S
authors.initials: AS
authors.lastname: Hilibrand
authors.forename: James S
authors.initials: JS
authors.lastname: Harrop
authors.forename: Brian K
authors.initials: BK
authors.lastname: Kwon
authors.forename: John M
authors.initials: JM
authors.lastname: Beiner
authors.forename: Todd J
authors.initials: TJ
authors.lastname: Albert
authors.forename: Michael G
authors.initials: MG
authors.lastname: Fehlings
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Vaccaro
mesh_terms: D002965:Classification; D005592:Fracture Fixation / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D009809:Odontoid Process / Q000293:injuries* / Q000601:surgery; D009985:Orthopedics / Q000379:methods*; D015203:Reproducibility of Results; D016103:Spinal Fractures / Q000145:classification* / Q000601:surgery