Biomedical Engineering Reference
In-Depth Information
menopausal or age-related bone loss for females and males, respectively, is a
marked increase in fracture incidence, although the changes to the trabecular bone
architecture are different between sexes.
1 Introduction
Trabecular bone is found at the end of the long bones of the appendicular skeleton
and in the vertebral bodies of the axial skeleton. The bone has a complex, porous
spatial arrangement and the spatial complexity contributes to maximal strength for
minimum mass for the skeleton as a whole [
23
]. The high mineral surface area
associated with the arrangement of the trabecular bone elements provides a vast
substrate on which cellular interaction with bone mineral material can occur.
The characterisation of trabecular bone structure has until recently relied on
morphometric analysis of histological sections. While histological sections only
provide a two-dimensional ''snapshot'' of the complex three-dimensional entity,
the insights gained from these preparations have been validated and further
developed by the data analysis from three-dimensional imaging modalities that
have become the methods of choice for studying trabecular bone [
12
,
27
,
75
,
78
].
The main difference between these methodologies is that of bias in estimating the
dimensions of the trabecular bone structure from histological sections [
78
]. The
bias originates from the use of Parfitt's idealized plate and rod model of trabecular
bone structure [
85
]. The destructive nature of histological section preparation has
limited the study of bone strength to parallel investigations in cross-sectional
studies [
2
,
19
,
20
,
24
,
28
,
34
,
37
,
70
,
78
,
86
,
89
,
98
,
104
,
106
].
There is now wide availability of bench top non-destructive X-ray-based imaging
with the ability to resolve trabecular elements at resolution on the order of
*10 microns. The advent of non-destructive X-ray-based imaging, such as micro-
computed tomography (micro-CT) has enabled measurements from image datasets,
representing the three-dimensional structure of trabecular bone [
63
,
79
,
100
,
101
].
Subsequent mechanical testing of the same sample has enabled explanatory models
of bone strength to be developed, which provide further understanding of the change
in trabecular bone structure associated with ageing and disease [
6
,
64
,
102
]. These
three-dimensional datasets have also been used as input for finite element analysis
models to determine apparent mechanical properties of bone [
62
,
81
]. To the present,
trabecular bone has been studied at multiple skeletal sites, in all age groups from
neonates to the elderly [
4
,
14
,
42
,
111
]. Advantages given by non-destructive
imaging of trabecular bone include the ability to subsequently perform mechanical
testing on the bone samples, histological analysis and/or gene expression analysis
[
6
,
105
,
106
].
Ex vivo studies into trabecular bone structure in osteoporosis have mainly
focused on clinically relevant skeletal sites, such as the proximal femur, the distal
radius and vertebral bodies [
3
,
35
,
36
]. In vivo, the iliac crest and the sternum have
been used to obtain material for the diagnosis of metabolic bone diseases including
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