Osteocyte lacunar properties and cortical microstructure in human iliac crest as a function of age and sex.

Osteocytes are suggested to play a central role in bone remodeling. Evaluation of iliac crest biopsies is a standard procedure for evaluating bone conditions in the clinical setting. Despite the widespread use of such biopsies, little is known about the population of osteocytes in the iliac crest from normal individuals. Contradicting results have been reported on osteocyte lacunar properties in human bone. Hence, a solid understanding of the osteocyte population in healthy bone and the effect of age and sex is needed as good reference data are lacking. Furthermore, the role of cortical bone in bone quality has recently been suggested to be more important than previously realized. Therefore, the present study assesses osteocyte lacunar properties and cortical microstructure of the iliac crest as a function of age and sex. A total of 88 iliac crest bone samples from healthy individuals (46 women, aged 18.5-96.4years and 42 men, aged 22.6-94.6years) with an even age-distribution were examined using synchrotron radiation µCT and in house µCT, with >5×10(6) osteocyte lacunae measured and analyzed. The study revealed that osteocyte lacunar volumes were unaffected by both age and sex. Osteocyte lacunar density did not differ between women and men, and only showed a significant decrease with age when pooling data from both sexes. Cortical porosity and Haversian canal density increased while cortical thickness decreased with age, with cortical thinning dominating the age-related cortical bone loss. None of the cortical microstructural parameters showed any sex dependency. Only weak links between osteocyte lacunar properties and cortical microstructural properties in iliac crest bone were found. Interestingly, the Haversian canal diameters were significantly but weakly negatively correlated with osteocyte lacunar volumes.

Age-related changes of vertical and horizontal lumbar vertebral trabecular 3D bone microstructure is different in women and men.

The study presents a 3D method for subdividing a trabecular network into horizontal and vertical oriented bone. This method was used to investigate the age related changes of the bone volume fraction and thickness of horizontal and vertical trabeculae in human lumbar vertebral bone estimated with unbiased 3D methods in women and men over a large age-range. The study comprised second lumbar vertebral body bone samples from 40 women (aged 21.7-96.4years, median 56.6years) and 39 men (aged 22.6-94.6years, median 55.6years). The bone samples were µCT scanned and the 3D microstructure was quantified. A voxel based algorithm inspecting the local neighborhood is presented and used to segment the trabecular network into horizontal and vertical oriented bone. For both women and men BV/TV decreased significantly with age, Tb.Th* was independent of age, while SMI increased significantly with age. Vertical (BV.vert/TV) and horizontal (BV.horz/TV) bone volume fraction decreased significantly with age for both sexes. BV.vert/TV decreased significantly faster with age for women than for men. Vertical (Tb.Th*.vert) and horizontal (Tb.Th*.horz) trabecular thickness were independent of age, while Tb.Th*.horz/Tb.Th*.vert decreased significantly with age for both sexes. Additionally, the 95th percentile of the trabecular thickness distribution increased significantly with age for vertical trabeculae in women, whereas it was independent of age in men. In conclusion, we have shown that vertical and horizontal oriented bone density decreases with age in both women and men, and that vertical oriented bone is lost more quickly in women than in men. Furthermore, vertical and horizontal trabecular thickness were independent of age, whereas the horizontal to vertical trabecular thickness ratio decreased significantly with age indicating a relatively more pronounced thinning of horizontal trabeculae. Finally, the age-related loss of trabecular elements appeared to result in a compensatory hypertrophy of vertical trabeculae in women, but not in men.