Biomedical Engineering Reference
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Fig. 4 Histological images of osteoclasts removing bone matrix (left) and osteoblasts laying
down osteoid (right). Von Kossa's silver impregnation with Hematoxylin and Eosin counterstain.
(Black is bone mineral, on the left panel, arrows indicate actively resorbing osteoclasts and on the
right panel arrows indicate osteoblast actively laying down osteoid on bone surfaces)
(BV/TV, also called 'bone volume fraction'), bone surface per tissue volume
(BS/TV) and bone surface per bone volume (BS/BV). From these independent
measures, derived parameters include trabecular thickness (Tb.Th), trabecular sep-
aration (Tb.Sp) and trabecular number (Tb.N) [ 87 ]. These histomorphometric
indices of bone structure have been universally adopted [ 84 ] and continue to be used.
Bone histomorphometry has also been extended to bone cell dynamics,
including mineralization measured from fluorochrome labeling. By measuring the
extent of bone surface with osteoid, resorption pits or active mineralization it is
possible to derive indices of bone turnover [ 39 , 106 ]. These techniques have
provided insights into the temporal sequence of the components of the basic
multicellular unit (BMU) [ 39 ], such that activation frequency for new BMUs can
be calculated, the extent of resorption measured, the extent of osteoid measured
and the rate of mineralization of the osteoid calculated [ 13 ]. More recently, the
principles of bone histomorphometry have been adapted to quantify microdamage
accumulation, where en bloc or bulk staining of whole bone samples preferentially
stains areas of microdamage, which can be visualized after subsequent processing
into resin and sectioning [ 30 , 32 , 72 , 95 ].
The quantitative techniques available for study of trabecular bone structure and
trabecular bone cellular dynamics encompass manual, semi-quantitative/interac-
tive and automated techniques. Manual quantitation from histological sections of
trabecular bone involves point counting, where a grid pattern overlaid on the
section determines where sampling of the feature of interest occurs [ 56 ]. These
point counts provide estimates of area or perimeter of the features of interest and
by application of Parfitt's plate or rod model to the raw point counts, indices
representing the trabecular bone structure are derived [ 84 ]. Point counting tech-
niques have been applied to provide static indices of trabecular bone structure,
such as bone volume fraction, trabecular thickness, trabecular separation and
trabecular number as well as dynamic indices of bone structure, such as bone
formation rate and bone apposition rate [ 40 ]. Semi-quantitative techniques typi-
cally utilize a camera-mounted microscope interfaced to a computer monitor
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