Spatial distribution of intracortical porosity varies across age and sex - PubMed (original) (raw)

Spatial distribution of intracortical porosity varies across age and sex

Jasmine A Nirody et al. Bone. 2015 Jun.

Abstract

Cortical bone porosity is a major determinant of strength, stiffness, and fracture toughness of cortical tissue. The goal of this work was to investigate changes in spatial distribution and microstructure of cortical porosity associated with aging in men and women. The specific aims were to: 1) develop an automated technique for spatial analysis of cortical microstructure based on HR-pQCT data, and; 2) apply this technique to explore sex- and age-specific spatial distribution and microstructure of porosity within the cortex. We evaluated HR-pQCT images of the distal tibia from a cross-sectional cohort of 145 individuals, characterizing detectable pores as being in the endosteal, midcortical, or periosteal layers of the cortex. Metrics describing porosity, pore number, and pore size were quantified within each layer and compared across sexes, age groups, and cortical layers. The elderly cohort (65-78 years, n=22) displayed higher values than the young cohort (20-29 years, n=29) for all parameters both globally and within each layer. While all three layers displayed significant age-related porosity increases, the greatest difference in porosity between the young and elderly cohort was in the midcortical layer (+344%, p<0.001). Similarly, the midcortical layer reflected the greatest differences between young and elderly cohorts in both pore number (+243%, p<0.001) and size (+28%, p<0.001). Females displayed greater age-related changes in porosity and pore number than males. Females and males displayed comparable small to non-significant changes with age in pore size. In summary, considerable variability exists in the spatial distribution of detectable cortical porosity at the distal tibia, and this variability is dependent on age and sex. Intracortical pore distribution analysis may ultimately provide insight into both mechanisms of pore network expansion and biomechanical consequences of pore distribution.

Keywords: Aging; Cortical bone; Gender; HR-pQCT; Porosity; Spatial distribution.

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Figures

Fig. 1

An overview of cortical layers and the pore assignment technique. Unassigned pores are shown in black (top panel in inlay). Pores are assigned to one of endosteal, midcortical, or periosteal layers (shown in red, blue, and green respectively). This assignment is done according to the location of the pore’s skeleton (second and third panels in inlay). Pores are assigned wholly to a layer; no individual pore is split between layers (bottom panel in inlay). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Gender-specific variation in the evolution of total pore area (TPA, mm2/mm2), total pore number (TPN, mm−2), and average pore area (APA, mm2) with age. Data shown are mean ± 95% CI in each cohort grouped by age and gender. Boxed values indicate differences between young (20–29) and elderly (65–78) cohorts.

Fig. 3

Decade-by-decade total pore area (TPA, mm2/mm2) by layer for males (top) vs. females (bottom). Data shown are the mean ± 95% CI. Females display a significant increase in porosity between the fourth and fifth decades (consistent with the onset of menopause), while males show a more gradual increase. Accelerated age-related porosity increase is most extreme in the midcortical layer in the female cohort.

Fig. 4

Decade-by-decade analysis of total pore number (TPN, mm−2) by layer for males (top) vs. females (bottom). Data shown are the mean ± 95% CI. The female cohort undergoes a more drastic increase in TPN with age than the male cohort. Age-related TPN increase is most extreme in the midcortical layer in the female cohort.

Fig. 5

Decade-by-decade analysis of average pore area (APA mm2) by layer for males (top) vs. females (bottom). Data shown are the mean ± 95% CI.

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Spatial distribution of intracortical porosity varies across age and sex - PubMed (original) (raw)