title: Effect of an intervertebral disk spacer on stiffness after monocortical screw/polymethylmethacrylate fixation in simulated and cadaveric canine cervical vertebral columns.
abstract: OBJECTIVE
  To determine the biomechanical effect of an intervertebral spacer on construct stiffness in a PVC model and cadaveric canine cervical vertebral columns stabilized with monocortical screws/polymethylmethacrylate (PMMA).
  
  
  METHODS
  Biomechanical study.
  
  
  METHODS
  PVC pipe; cadaveric canine vertebral columns.
  
  
  METHODS
  PVC model-PVC pipe was used to create a gap model mimicking vertebral endplate orientation and disk space width of large-breed canine cervical vertebrae; 6 models had a 4-mm gap with no spacer (PVC group 1); 6 had a PVC pipe ring spacer filling the gap (PCV group 2). Animals-large breed cadaveric canine cervical vertebral columns (C2-C7) from skeletally mature dogs without (cadaveric group 1, n = 6, historical data) and with an intervertebral disk spacer (cadaveric group 2, n = 6) were used. All PVC models and cadaver specimens were instrumented with monocortical titanium screws/PMMA. Stiffness of the 2 PVC groups was compared in extension, flexion, and lateral bending using non-destructive 4-point bend testing. Stiffness testing in all 3 directions was performed of the unaltered C4-C5 vertebral motion unit in cadaveric spines and repeated after placement of an intervertebral cortical allograft ring and instrumentation. Data were compared using a linear mixed model approach that also incorporated data from previously tested spines with the same screw/PMMA construct but without disk spacer (cadaveric group 1).
  
  
  RESULTS
  Addition of a spacer increased construct stiffness in both the PVC model (P < .001) and cadaveric vertebral columns (P < .001) compared to fixation without a spacer.
  
  
  CONCLUSIONS
  Addition of an intervertebral spacer significantly increased construct stiffness of monocortical screw/PMMA fixation.
authors: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Ohio State University, Columbus, Ohio.
authors: Bianca F
authors: BF
authors: Hettlich
authors: Matthew J
authors: MJ
authors: Allen
authors: Gabriela S
authors: GS
authors: Glucksman
authors: Geoffrey T
authors: GT
authors: Fosgate
authors: Alan S
authors: AS
authors: Litsky
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001843:Bone Cements; D001863:Bone Screws / Q000662:veterinary*; D002102:Cadaver; D002574:Cervical Vertebrae / Q000293:injuries / Q000601:surgery*; D004285:Dogs / Q000293:injuries / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000379:methods / Q000662:veterinary*; D007403:Intervertebral Disc; D019904:Polymethyl Methacrylate / Q000008:administration & dosage; D016059:Range of Motion, Articular
chemical_list: D001843:Bone Cements; D019904:Polymethyl Methacrylate