title: Assessment of axial bone rigidity in rats with metabolic diseases using CT-based structural rigidity analysis.
abstract: OBJECTIVE
  This study aims to assess the correlation of CT-based structural rigidity analysis with mechanically determined axial rigidity in normal and metabolically diseased rat bone.
  
  
  METHODS
  A total of 30 rats were divided equally into normal, ovariectomized, and partially nephrectomized groups. Cortical and trabecular bone segments from each animal underwent micro-CT to assess their average and minimum axial rigidities using structural rigidity analysis. Following imaging, all specimens were subjected to uniaxial compression and assessment of mechanically-derived axial rigidity.
  
  
  RESULTS
  The average structural rigidity-based axial rigidity was well correlated with the average mechanically-derived axial rigidity results (R(2) = 0.74). This correlation improved significantly (p < 0.0001) when the CT-based Structural Rigidity Analysis (CTRA) minimum axial rigidity was correlated to the mechanically-derived minimum axial rigidity results (R(2) = 0.84). Tests of slopes in the mixed model regression analysis indicated a significantly steeper slope for the average axial rigidity compared with the minimum axial rigidity (p = 0.028) and a significant difference in the intercepts (p = 0.022). The CTRA average and minimum axial rigidities were correlated with the mechanically-derived average and minimum axial rigidities using paired t-test analysis (p = 0.37 and p = 0.18, respectively).
  
  
  CONCLUSIONS
  In summary, the results of this study suggest that structural rigidity analysis of micro-CT data can be used to accurately and quantitatively measure the axial rigidity of bones with metabolic pathologies in an experimental rat model. It appears that minimum axial rigidity is a better model for measuring bone rigidity than average axial rigidity.
authors.affiliation: Harvard Medical School, 25 Shattuck Street, Boston, 02115 Massachusetts, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Smith
authors.forename: S
authors.initials: S
authors.lastname: Baldassarri
authors.forename: L
authors.initials: L
authors.lastname: Anez-Bustillos
authors.forename: A
authors.initials: A
authors.lastname: Tseng
authors.forename: V
authors.initials: V
authors.lastname: Entezari
authors.forename: D
authors.initials: D
authors.lastname: Zurakowski
authors.forename: B D
authors.initials: BD
authors.lastname: Snyder
authors.forename: A
authors.initials: A
authors.lastname: Nazarian
keywords: Bone; Computed tomography; Fracture risk; Metabolic bone disease; Rat model; Structural rigidity