title: Design and biomechanical evaluation of a rodent spinal fixation device.
abstract: METHODS
  An in vitro and in vivo study in rats.
  
  
  OBJECTIVE
  To design a novel rat spinal fixation device and investigate its biomechanical effectiveness in stabilizing the spine up to 8 weeks post injury.
  
  
  METHODS
  A fixation device made of polyetheretherketone was designed to stabilize the spine via bilateral clamping pieces. The device effectiveness was assessed in a Sprague-Dawley rat model after it was applied to a spine with a fracture-dislocation injury produced at C5-C6. Animals were euthanized either immediately (n=6) or 8 weeks (n=9) post-injury and the C3-T1 segment of the cervical spine was removed for biomechanical evaluation. Segments of intact spinal columns (C3-T1) (n=6) served as uninjured controls. In these tests, anterior-posterior shear forces were applied to the C3 vertebra to produce flexion and extension bending moments at the injury site (peak 12.8 Nmm). The resultant two-dimensional motions at the injury site (that is, C5-C6) were measured using digital imaging and reported as ranges of motion (ROM) or neutral zones (NZ).
  
  
  RESULTS
  Flexion/extension ROMs (average±s.d.) were 18.1±3.3°, 19.9±7.5° and 1.5±0.7°, respectively for the intact, injured/fixed, and injured/8-week groups, with the differences being highly significant for the injured/8-week group (P=0.0002). Flexion/extension NZs were 3.4±2.8°, 5.0±2.4°, and 0.7±0.5°, respectively for the intact, injured/fixed, and injured/8-week groups, with the differences being significant for the injured/8-week group (P=0.04).
  
  
  CONCLUSIONS
  The device acutely stabilizes the spine and promotes fusion at the site of injury.
authors.affiliation: Orthopaedic and Injury Biomechanics Group, Departments of Orthopaedics, The University of British Columbia and Vancouver Coastal Health Research Institute, Vancouver, British Columbia, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Shahrokni
authors.forename: Q
authors.initials: Q
authors.lastname: Zhu
authors.forename: J
authors.initials: J
authors.lastname: Liu
authors.forename: W
authors.initials: W
authors.lastname: Tetzlaff
authors.forename: T R
authors.initials: TR
authors.lastname: Oxland
mesh_terms: D000818:Animals; D002574:Cervical Vertebrae / Q000293:injuries* / Q000503:physiopathology / Q000601:surgery; D055119:Elastic Modulus; D019544:Equipment Failure Analysis; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000662:veterinary*; D008297:Male; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D051381:Rats; D017207:Rats, Sprague-Dawley; D016103:Spinal Fractures / Q000503:physiopathology* / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000662:veterinary*; D013314:Stress, Mechanical; D016896:Treatment Outcome