title: Effects of endplate removal on the structural properties of the lower lumbar vertebral bodies.
abstract: METHODS
  A biomechanical investigation using indentation tests in human cadaveric lumbar vertebrae.
  
  
  OBJECTIVE
  To determine the effect of endplate removal on the structural properties across the lower lumbar vertebral bodies (L3-L5).
  
  
  BACKGROUND
  The structural properties of the vertebral endplates exhibit substantial regional variation. In addition, several recent studies of the endplate-implant interface have suggested that the endplate is not a significant structural element.
  
  
  METHODS
  The bony endplates on the left or right side of seven intact human vertebrae (L3-L5) were removed with a high-speed burr. Indentation tests were performed at standardized test sites on both sides of the endplate using a 3-mm diameter, hemispherical indenter with a test rate of 0.2 mm/s to a depth of 3 mm. The failure load and stiffness at each site were determined from the load-displacement curves. Three-way repeated measures analyses of variance were used to analyze the resulting data for variation in the anterior-posterior and lateral directions, as well as to determine the effect of endplate removal.
  
  
  RESULTS
  For the intact endplates, both the failure load and stiffness varied significantly across the endplate surfaces (P < 0.0001), with the posterolateral regions being stronger and stiffer than the central regions. With endplate removal, the mean failure load decreased to about 33% of the intact failure load, a significant drop (P = 0.04), and there was a trend toward greater decreases posteriorly (P = 0.05). With endplate removal, the mean stiffness also decreased significantly (P = 0.01), with the greater decreases occurring laterally (P = 0.04).
  
  
  CONCLUSIONS
  There was a significant effect of endplate removal on the local structural characteristics of the vertebral endplate.
authors.affiliation: Division of Orthopaedic Engineering Research, University of British Columbia and Vancouver Hospital and Health Sciences Centre, Vancouver, British Columbia, Canada. toxland@interchange.ubc.ca
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Oxland
authors.forename: J Pamela
authors.initials: JP
authors.lastname: Grant
authors.forename: Marcel F
authors.initials: MF
authors.lastname: Dvorak
authors.forename: Charles G
authors.initials: CG
authors.lastname: Fisher
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D002102:Cadaver; D019245:Compressive Strength / Q000502:physiology; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology*; D008161:Lumbosacral Region; D013314:Stress, Mechanical