title: The intravertebral distribution of bone density: correspondence to intervertebral disc health and implications for vertebral strength.
abstract: This study's goal was to determine associations among the intravertebral heterogeneity in bone density, bone strength, and intervertebral disc (IVD) health. Results indicated that predictions of vertebral strength can benefit from considering the magnitude of the density heterogeneity and the congruence between the spatial distribution of density and IVD health.
  
  
  BACKGROUND
  This study aims to determine associations among the intravertebral heterogeneity in bone density, bone strength, and IVD health
  
  
  METHODS
  Regional measurements of bone density were performed throughout 30 L1 vertebral bodies using micro-computed tomography (μCT) and quantitative computed tomography (QCT). The magnitude of the intravertebral heterogeneity in density was defined as the interquartile range and quartile coefficient of variation in regional densities. The spatial distribution of density was quantified using ratios of regional densities representing different anatomical zones (e.g., anterior to posterior regional densities). Cluster analysis was used to identify groups of vertebrae with similar spatial distributions of density. Vertebral strength was measured in compression. IVD health was assessed using two scoring systems.
  
  
  RESULTS
  QCT- and μCT-based measures of the magnitude of the intravertebral heterogeneity in density were strongly correlated with each other (p < 0.005). Accounting for the interquartile range in regional densities improved predictions of vertebral strength as compared to predictions based only on mean density (R (2) = 0.59 vs. 0.43; F-test p-value = 0.018). Specifically, after adjustment for mean density, vertebral bodies with greater heterogeneity in density exhibited higher strength. No single spatial distribution of density was associated with high vertebral strength. Analyses of IVD scores suggested that the health of the adjacent IVDs may modulate the effect of a particular spatial distribution of density on vertebral strength.
  
  
  CONCLUSIONS
  Noninvasive measurements of the intravertebral distribution of bone density, in conjunction with assessments of IVD health, can aid in predictions of bone strength and in elucidating biomechanical mechanisms of vertebral fracture.
authors.affiliation: Department of Mechanical Engineering, Boston University, 110 Cummington Mall, Boston, MA, 02215, USA, amirah@bu.edu.
authors.forename: A I
authors.initials: AI
authors.lastname: Hussein
authors.forename: T M
authors.initials: TM
authors.lastname: Jackman
authors.forename: S R
authors.initials: SR
authors.lastname: Morgan
authors.forename: G D
authors.initials: GD
authors.lastname: Barest
authors.forename: E F
authors.initials: EF
authors.lastname: Morgan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density / Q000502:physiology*; D019245:Compressive Strength / Q000502:physiology; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000502:physiology* / Q000503:physiopathology; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000379:methods; D055114:X-Ray Microtomography / Q000379:methods