Biomedical Engineering Reference
In-Depth Information
Table 1
Changes in trabecular bone structure or density with ageing from middle to old age
Study
Materials
Site
(parameter)
Male versus
female
Percent change per decade
Female
Male
QCT [
25
]
51F,50M
19-96 years
L3 Vertebra
(vBMD)
ns
-9%
-9%
Micro-CT
[
26
,
66
]
75 F, 75 M
52-99 years
L2 Vertebra
(BV/TV)
ns
-9.1
ns
Iliac crest
(BV/TV)
ns
-15.5
ns
Femoral neck
(BV/TV)
F \ M
(-35%)
-13.4
ns
Femoral troch.
(BV/TV)
F \ M
(-19%)
ns
9.0
Calcaneus
(BV/TV)
ns
-8.3
ns
Distal radius
(BV/TV)
F \ M
(-30%)
ns
ns
HR-pQCT
[
74
]
64 F, 66 M
60-99 years
Distal radius
[region 1]
(BV/TV)
F \ M
(-32%)
-11.4
-9.1
F female M male; ns not significant (p [ 0.05)
which results in a large increase in osteoclastic resorption. This massive up-reg-
ulation in the removal of bone matrix is not matched by equivalent replacement of
bone therefore there is a net loss of bone mass. The increased number and depth of
resorption events results in perforation of individual trabeculae, particularly rod-
like structures, which now unloaded are targeted for further resorption and com-
pletely removed. This process results in disconnectivity in the structure locally and
as a whole and reduces the strength of the structure to a greater degree than
accounted for by the loss of bone mass alone [
97
,
107
]. In addition, plate-like
trabeculae become perforated and over a number of cycles become more rod-like,
which in turn are susceptible to complete perforation and removal. While the
increased turnover in females returns to pre-menopausal levels after a number of
years, the transformation of the trabecular bone structural can be dramatic with an
associated increase in fracture risk.
In males, loss of bone mass from the 6th decade is more gradual than for
females and is associated with decreased androgen production [
68
,
92
]. There is
increased bone activation of osteoclasts but not to the extent seen in menopausal
females, which while resulting in decreased bone mass is not associated with
resorption of sufficient depth to perforate trabeculae. Hence, there is generalized
thinning of trabeculae but the overall structure remains intact. However, in both
males and females there is an increased fracture incidence, which is not completely
explained by the loss of bone mass, which again suggests that the mechanical
integrity of the trabecular bone structure has been compromised [
68
].
The sex specific changes to trabecular bone structure in aging, described
above, are generalizations, and for individuals will be a combination of trabecular
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