title: Role of posterior elements in the disc bulging of a degenerated cervical spine.
abstract: BACKGROUND
  Many studies have been developed to characterize the mechanical behavior of the intervertebral disc specifically for the lumbar spine and there have been limited studies done on the cervical spine with the goal to evaluate the strength of the cervical spine under compression without any information on the bulging of the intervertebral discs. The goal of the current study is to examine the deformation response of the cervical intervertebral disc classified with grade III or greater degeneration and analyze the relationship between axial deformation and anterior and posterior bulge under compression up to 550 N.
  
  
  METHODS
  Each specimen was compressed for 3 cycles to a maximum load of 550N in steps of 50 N. The bulge was measured using Linear Variable Differential Transformers (LVDTs on an intact spinal segment, spinal segment with post laminectomy, and spinal segment post facetectomy.
  
  
  RESULTS
  The anterior budge for an intact spinal segment shows a change of slope at loads of 262N±66N. For a physiological load of 250N the vertical displacement or spine segment height was reduced by 10.1% for an intact segment and 8.78% for the laminectomy and facetectomy configurations with F = 0.159 (Fcrit = 3.89) with no statistical difference observed. For the post laminectomy there was a decrease of 35% in anterior bulge compared to the intact specimen.
  
  
  CONCLUSIONS
  Our results show that for grade III disc degeneration the cervical segments bulging for both the laminectomy and facetectomy procedures are not significantly different. In post laminectomy the average anterior and posterior bulges are similar to the average anterior and posterior bulge post facetectomy.
authors.affiliation: Department of Orthopaedics, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Farid
authors.initials: F
authors.lastname: Amirouche
authors.affiliation: Department of Orthopaedics, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Giovanni F
authors.initials: GF
authors.lastname: Solitro
authors.affiliation: Department of Orthopaedics, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Kris
authors.initials: K
authors.lastname: Siemionow
authors.affiliation: Department of Orthopaedics, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: David
authors.initials: D
authors.lastname: Drucker
authors.affiliation: Department of Orthopaedics, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Ashish
authors.initials: A
authors.lastname: Upadhyay
authors.affiliation: Department of Orthopaedics, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Priyesh
authors.initials: P
authors.lastname: Patel
keywords: Bulging; Cervical Spine; Facetectomy; Laminectomy; disc degeneration