title: Anterior cervical plating reverses load transfer through multilevel strut-grafts.
abstract: METHODS
  In vitro biomechanical study using a programmable testing apparatus that replicated physiologic flexion/extension cervical spine motion and loading mechanics.
  
  
  OBJECTIVE
  To determine the influence of anterior plating on multilevel cervical strut-graft mechanics in vitro.
  
  
  BACKGROUND
  The addition of anterior instrumentation does not prevent construct failure in multilevel cervical corpectomy.
  
  
  METHODS
  Six fresh human cadaveric cervical spines (C2-T1) were tested in the four following sequential conditions: harvested, C4-C6 corpectomy, strut-grafted, and strut-grafted with an anterior cervical plate. A force-sensing strut-graft was used to measure compression/tension, flexion/extension and lateral bending moments, and axial torsion. Parameters of stiffness, vertebral motion, and strut-graft loads were compared to determine differences between the four spine conditions.
  
  
  RESULTS
  Application of the anterior plate significantly increased the global stiffness (P < 0.01) and decreased the local motion (P < or = 0.01) of the instrumented levels (C3-C7). Flexion of the strut-grafted spine loaded the strut-graft, whereas extension unloaded the strut-graft. With the anterior plate, flexion of the plated spine unloaded the strut-graft. Extension significantly loaded the strut-graft more than similar degrees of flexion in the strut-grafted condition (P = 0.01). Strut-graft loading end limits of 225 N were reached with a mean 7.5 degrees extension in the plated spines.
  
  
  CONCLUSIONS
  Anterior multilevel cervical plating effectively increases stiffness and decreases local cervical motion after corpectomy. However, anterior cervical plating also reverses graft loads and excessively loads the graft in extension, which may promote pistoning and failure of multilevel constructs.
authors.affiliation: from the School of Biomedical Engineering and the Department of Neurosurgery, University of Tennessee-Memphis, Memphis, TN 38163, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: DiAngelo
authors.forename: K T
authors.initials: KT
authors.lastname: Foley
authors.forename: K A
authors.initials: KA
authors.lastname: Vossel
authors.forename: Y R
authors.initials: YR
authors.lastname: Rampersaud
authors.forename: T H
authors.initials: TH
authors.lastname: Jansen
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D002574:Cervical Vertebrae / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement; D012399:Rotation; D013128:Spinal Osteophytosis / Q000601:surgery; D016474:Weight-Bearing