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Fig. 19 Collagen orientation distribution in the cross-section of female femurs. a a 28-year-old
female individual demonstrating a high proportion of transverse collagen fibers, predominantly
located within circumferential lamellar bone, b a 51-year-old female individual demonstrating a
high proportion of transverse collagen fibers in circumferential lamellar bone of the anterior
cortex, c an 88-year-old female demonstrating little patterning of collagen fiber orientation
around the cortex. (Presented by Goldman et al. [
143
])
mineral density of the humeral shaft does not vary significantly between genders
[
108
]. Similarly, gender effects on mineralization were not significant in the
proximal and mid-shaft of the femur [
105
]. In slight contrast, quantitative
microradiography of the femoral shaft shows that women start with a higher level
of mineralization than men, but fall below the level in men after the sixth decade;
mineralization was more stable throughout life in men [
100
].
5.1.4 Collagen Phase
The effect of gender on the micro- and ultrastructural changes in the collagen network
of bone are not well documented in the literature. Nonetheless, some studies have
indicated that gender has an influence on collagen fibril orientation, collagen network
integrity, as well as its interaction with the mineral phase. The variability of preferred
collagen fiber orientation in bone from women is related to age, showing a complex
pattern between age groups (Fig.
19
)[
143
]. Irrespective of a similar trend between
males and females, higher variability between different age groups is found in females
than males. For instance, the proportion of collagen fibers aligned transversely
decreases more with age in women. In addition, females show a higher proportion of
transversely oriented lamellae in newly formed bone than males [
143
,
144
].
Cortical bone from women and men has shown age-related changes in both
immature and mature enzymatic collagen crosslinks. In a study on secondary osteons
and interstitial tissues from middle-aged (42-63 years) and elderly (69-90 years)
bone, the mature enzymatic cross-links (i.e., hydroxylysyl-pyridinoline [HP] and
lysylpyridinoline [LP]) decreased slightly after middle-age, perhaps due to increased
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