Objectives. 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