Biomedical Engineering Reference
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Fig. 14.5.
An optical micrograph and stress maps in bovine femoral bone near a
fracture. The map in (
a
) was acquired at zero applied stress and in (
b
)atcritical
stress for crack propagation. The net stress field was obtained by subtracting (
a
)
from (
b
) and is shown in (
c
). Reprinted with permission from [48]
Tensile stresses were intensified even under weak external compression, and
a crisscross-like pattern was observed, suggesting a particular organization of
the collagen fibrils.
14.7 Osteoporosis
Most vibrational spectroscopic studies of osteoporotic tissue have been per-
formed in the infrared. For example, FTIR imaging of specimens from human
iliac crest biopsies showed that mineralization in untreated osteoporotic tra-
becular bone samples were decreased by
40% from the normal and the min-
eral/matrix ratio was lower in the center of trabeculae (more mature tissue)
than for controls [53]. The crystallinity ratio also increased in osteoporotic
specimens. Differences between the trabecular bone matrix of osteoporotic
and normal bone have also been demonstrated [54]. The spatial variation
of cross-links at bone-forming trabecular surfaces (within 50
∼
m) in patients
with osteoporotic or multiple spontaneous fractures was significantly different
than in normal bone and the collagen cross-link ratio was higher. It has been
hypothesized that the matrix produced in osteoporosis might mature more
quickly or undergo post-translational modifications for a longer time than
normal bone matrix.
However, signatures of susceptibility to osteoporotic fracture have been
identified in osteoporotic tissue matched for bone volume fraction. Fracture is
associated with more carbonated mineral [55], which is in turn associated with
μ
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