title: The effect of disc degeneration on anterior shear translation in the lumbar spine.
abstract: Many pathologies involving disc degeneration are treated with surgery and spinal implants. It is important to understand how the spine behaves mechanically as a function of disc degeneration. Shear loading is especially relevant in the natural and surgically stabilized lumbar spine. The objective of our study was to determine the effect of disc degeneration on anterior translation of the lumbar spine under shear loading. We tested 30 human cadaveric functional spinal units (L3-4 and L4-5) in anterior shear loading. First, the specimens were imaged in a 1.5 T magnetic resonance scanner. The discs were graded according to the Pfirrmann classification. The specimens were then loaded up to 250 N in anterior shear with an axial compression force of 300 N. Motion of the vertebrae was captured with an optoelectronic camera system. Inter- and intra-observer reliability for disc grading was determined (Cohen's and Fleiss' Kappa), and a non-parametric test was performed on the translation data to characterize the effect of disc degeneration on this parameter. We found fair to moderate agreement between and within observers for the disc grading. We found no significant effect of disc degeneration on anterior shear translation (Kruskal-Wallis ANOVA). Our results indicate that disc degeneration, as classified with the Pfirrmann scale, does not predict lumbar spinal motion in shear.
authors.affiliation: Department of Mechanical Engineering, University of British Columbia, Vancouver, British Columbia, Canada; Department of Orthopaedics, University of British Columbia, Vancouver, British Columbia, Canada; International Collaboration on Repair Discoveries, Vancouver Coastal Health Research Institute, Vancouver, British Columbia, Canada.
authors.forename: Angela D
authors.initials: AD
authors.lastname: Melnyk
authors.forename: Adrienne
authors.initials: A
authors.lastname: Kelly
authors.forename: Jason D
authors.initials: JD
authors.lastname: Chak
authors.forename: Tian Lin
authors.initials: TL
authors.lastname: Wen
authors.forename: Peter A
authors.initials: PA
authors.lastname: Cripton
authors.forename: Marcel F
authors.initials: MF
authors.lastname: Dvorak
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Oxland
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D055959:Intervertebral Disc Degeneration / Q000150:complications / Q000503:physiopathology*; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009038:Motion; D015588:Observer Variation; D016474:Weight-Bearing
keywords: Disc degeneration; biomechanics; lumbar spine; shear; translation