title: ISSLS Prize Winner: Vibration Really Does Disrupt the Disc: A Microanatomical Investigation.
abstract: METHODS
  Microstructural investigation of vibration-induced disruption of the flexed lumbar disc.
  
  
  OBJECTIVE
  The aim of the study was to explore micro-level structural damage in motion segments subjected to vibration at subcritical peak loads.
  
  
  BACKGROUND
  Epidemiological evidence suggests that cumulative whole body vibration may damage the disc and thus play an important role in low back pain. In vitro investigations have produced herniations via cyclic loading (and cyclic with added vibrations as an exacerbating exposure), but offered only limited microstructural analysis.
  
  
  METHODS
  Twenty-nine healthy mature ovine lumbar motion segments flexed 7° and subjected to vibration loading (1300 ± 500 N) in a sinusoidal waveform at 5 Hz to simulate moderately severe physiologic exposure. Discs were tested either in the range of 20,000 to 48,000 cycles (medium dose) or 70,000 to 120,000 cycles (high dose). Damaged discs were analyzed microstructurally.
  
  
  RESULTS
  There was no large drop in displacement over the duration of both vibration doses indicating an absence of catastrophic failure in all tests. The tested discs experienced internal damage that included delamination and disruption to the inner and mid-annular layers as well as diffuse tracking of nucleus material, and involved both the posterior and anterior regions. Less frequent tearing between the inner disc and endplate was also observed. Annular distortions also progressed into a more severe form of damage, which included intralamellar tearing and buckling and obvious strain distortion around the bridging elements within the annular wall.
  
  
  CONCLUSIONS
  Vibration loading causes delamination and disruption of the inner and mid-annular layers and limited diffuse tracking of nucleus material. These subtle levels of disruption could play a significant role in initiating the degenerative cascade via micro-level disruption leading to cell death and altered nutrient pathways.
  
  
  METHODS
  5.
authors.affiliation: Experimental Tissue Mechanics Laboratory, Department of Chemical and Materials Engineering, University of Auckland, New Zealand.
authors.forename: Kelly R
authors.initials: KR
authors.lastname: Wade
authors.affiliation: Experimental Tissue Mechanics Laboratory, Department of Chemical and Materials Engineering, University of Auckland, New Zealand.
authors.forename: Meredith L
authors.initials: ML
authors.lastname: Schollum
authors.affiliation: Department of Orthopaedic Surgery, Auckland City Hospital, Auckland, New Zealand.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Robertson
authors.affiliation: Experimental Tissue Mechanics Laboratory, Department of Chemical and Materials Engineering, University of Auckland, New Zealand.
authors.forename: Ashvin
authors.initials: A
authors.lastname: Thambyah
authors.affiliation: Experimental Tissue Mechanics Laboratory, Department of Chemical and Materials Engineering, University of Auckland, New Zealand.
authors.forename: Neil D
authors.initials: ND
authors.lastname: Broom
mesh_terms: D000818:Animals; D001363:Awards and Prizes; D001696:Biomechanical Phenomena / Q000502:physiology*; D004195:Disease Models, Animal; D007403:Intervertebral Disc / Q000166:cytology*; D007405:Intervertebral Disc Displacement; D017116:Low Back Pain / Q000175:diagnosis / Q000473:pathology*; D008159:Lumbar Vertebrae / Q000033:anatomy & histology* / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology*; D012421:Rupture / Q000601:surgery; D012756:Sheep; D013314:Stress, Mechanical; D014732:Vibration; D016474:Weight-Bearing / Q000502:physiology