title: Biomechanical evaluation of anterior cervical spine stabilization.
abstract: METHODS
  An in vitro biomechanical study.
  
  
  OBJECTIVE
  To simulate a severe compressive flexion injury for determination of the relative stability of different anterior instrumentation systems in a porcine model and to validate this model in human cadaveric specimens.
  
  
  BACKGROUND
  Anterior plate fixation is useful for high-grade mechanical insufficiency of the cervical spine and may prevent the need for a second procedure.
  
  
  METHODS
  The cervical spines of 45 porcine and 12 cadaveric specimens were subjected to nondestructive flexion, lateral bending, and torsional testing on a modified universal testing machine. A corpectomy was performed with release of the posterior ligamentous structures. The specimens were stabilized with one of three anterior plate constructs. The nondestructive testing was repeated to evaluate structural stability (stiffness and neutral zone). Finally, destructive testing examined failure moment, energy to failure, and mechanism of failure.
  
  
  RESULTS
  The instrumented specimens had flexural and lateral bending and torsional stiffness values that were similar to or greater than those of their paired intact specimens. The cervical spine locking plate had a significantly higher flexural stiffness ratio (plated:intact), torsional stiffness ratio, lower flexural neutral zone ratio, higher failure moment, and higher energy to failure than did the Caspar plate.
  
  
  CONCLUSIONS
  The cervical spine locking plate is theoretically safer than the Caspar system because the posterior vertebral body cortex is not breached by the fixation screws, and the screws are less likely to back out anteriorly and irritate the esophagus. According to these results, the cervical spine locking plate system is biomechanically equivalent to and in some cases more stable than the Caspar system for fixation of a severe compressive flexion injury.
authors.affiliation: Department of Orthopedics, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Grubb
authors.forename: B L
authors.initials: BL
authors.lastname: Currier
authors.forename: J S
authors.initials: JS
authors.lastname: Shih
authors.forename: V
authors.initials: V
authors.lastname: Bonin
authors.forename: J J
authors.initials: JJ
authors.lastname: Grabowski
authors.forename: E Y
authors.initials: EY
authors.lastname: Chao
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D002574:Cervical Vertebrae / Q000293:injuries / Q000601:surgery*; D019544:Equipment Failure Analysis; D006801:Humans; D007796:Laminectomy; D008875:Middle Aged; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013124:Spinal Injuries / Q000601:surgery*; D013552:Swine; D013718:Tensile Strength / Q000502:physiology