title: Hangman's fracture: a biomechanical comparison of stabilization techniques.
abstract: METHODS
  In vitro biomechanical flexibility experiment studying 5 sequential conditions.
  
  
  OBJECTIVE
  To determine the biomechanical differences among 3 fixation techniques after a simulated hangman's fracture.
  
  
  BACKGROUND
  Type II hangman's fractures are often treated surgically with a C2-C3 anterior cervical discectomy, fusion, and plating. Other techniques include direct fixation with C2 pars interarticularis screws or posterior C2-C3 fixation connecting C2 pars screws to C3 lateral mass screws.
  
  
  METHODS
  Seven cadaveric specimens (Oc-C4) were tested intact, after a simulated hangman's fracture, and after each fixation technique. Flexion, extension, lateral bending, and axial rotation were induced using nonconstraining torques while recording angular motions stereophotogrammetrically.
  
  
  RESULTS
  Direct screw fixation reduced motion an average of 61% +/- 13% during lateral bending and axial rotation compared to the injured state (P < 0.007). However, instability remained during flexion and extension. Posterior C2-C3 rod fixation provided significantly greater rigidity than anterior plate fixation during lateral bending (P < 0.008) and axial rotation (P < 0.04).
  
  
  CONCLUSIONS
  Direct fixation of the pars ineffectively limits flexion and extension after a Type II hangman's fracture. If pars screw fixation can be achieved, posterior C2-C3 fixation more effectively stabilizes a hangman's fracture than anterior cervical plating.
authors.affiliation: London Health Sciences Centre, London, Ontario.
authors.forename: Neil
authors.initials: N
authors.lastname: Duggal
authors.forename: Robert H
authors.initials: RH
authors.lastname: Chamberlain
authors.forename: Luis E
authors.initials: LE
authors.lastname: Perez-Garza
authors.forename: Adolfo
authors.initials: A
authors.lastname: Espinoza-Larios
authors.forename: Volker K H
authors.initials: VK
authors.lastname: Sonntag
authors.forename: Neil R
authors.initials: NR
authors.lastname: Crawford
mesh_terms: D000328:Adult; D000368:Aged; D001368:Axis, Cervical Vertebra / Q000000981:diagnostic imaging / Q000293:injuries*; D001696:Biomechanical Phenomena; D001858:Bone Nails; D001860:Bone Plates; D001863:Bone Screws; D016025:Bone Transplantation; D002102:Cadaver; D002574:Cervical Vertebrae / Q000601:surgery; D017586:Diskectomy; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009984:Orthopedic Fixation Devices; D011859:Radiography; D016059:Range of Motion, Articular; D016103:Spinal Fractures / Q000150:complications* / Q000000981:diagnostic imaging; D013168:Spondylolisthesis / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology / Q000601:surgery*