Bone mineral density (BR;ID) and bone microarchitecture are important deter
minants for the mechanical properties of cancellous bone. Although BMD alon
e is a good predictor of average mechanical properties of cancellous bone,
there remains unexplained variation in mechanical properties that might be
due to missing information regarding bone microarchitecture. Recent develop
ments in three-dimensional (3D) structural analysis have provided possibili
ties for measuring a variety of structural indices to characterize bone mic
roarchitecture, The objectives of this study were to calculate structural i
ndices and elastic constants of human cancellous bone from different skelet
al sites and to investigate the predictive value of different 3D structural
indices for the elastic properties of bone, A total of 237 cancellous bone
samples taken from the iliac crest, lumbar spine, femoral head, and calcan
eus were imaged with a 3D microcomputed tomography (mu CT) system. The segm
ented 3D images were used to calculate BV/TV, BS/TV, Tb.Th, Tb.Sp, Tb.N, an
d hill, ratio and for microstructural finite-element (mu FE) analysis to ca
lculate Young's moduli, shear moduli, and Poisson's ratios. ii subgroup of
"critical" specimens within each site was selected to represent specimens t
hat could not be identified as osteoporotic or normal on the basis of BMD m
easurement alone. For these "critical" specimens, structural indices and el
astic constants were correlated by means of linear multivariate regression
analysis. It was found that the elastic constants clearly correlated better
when one of the 3D structural indices was included as independent variable
than when BV/TV was the only independent variable. Each of the examined st
ructural indices could improve the correlation: the R-2 values were maximal
ly increased from 53% (BV/TV alone) to 82% (BV/TV and MIL ratio). The most
effective indices, however, were not the same for the different skeletal si
tes. Even better correlations were found when more than one of the 3D struc
tural indices were included as independent variables: the R-2 values were m
aximally increased from 53% (BV/TV alone) to 92% (BV/TV, Tb,Sp, and Rm rati
o), The prediction of elastic constants for cancellous bone samples is clea
rly improved when BV/TV is supplemented with 3D structural indices. These r
esults suggest that the determination of mechanical properties of bone and
the diagnosis of osteoporosis can be improved if, in addition to BMD, the 3
D bone microarchitecture is assessed in vivo, (C) 1999 by Elsevier Science
Inc. All rights reserved.