No abstract

In conclusion, LS_aBMD and LS_TBS predicted fractures equally well. In our cohort, the addition of LS_TBS to age and LS_aBMD added only limited information on fracture risk prediction. However, using the lowest quartile of LS_TBS helped in redefining a significant subset of non-osteoporotic women as a higher risk group which is important for patient management.

Few studies have investigated bone microarchitecture and biomechanical properties in men. This study assessed in vivo both aspects in a population of 185 men (aged 71 AE 10 years) with prevalent fragility fractures, compared to 185 controls matched for age, height, and weight, from the Structure of the Aging Men's Bones (STRAMBO) cohort.In this case-control study, areal BMD (aBMD) was measured by DXA, bone microarchitecture was assessed by high resolution (HR)-pQCT, and finite element (mFE) analysis was based on HR-pQCT images of distal radius and tibia. A principal component (PC) analysis (PCA) was used to study the association of synthetic PCs with fracture by computing their odds ratio (OR [95%CI]) per SD change. Specific associations with vertebral fracture (n ¼ 100), and nonvertebral fracture (n ¼ 85) were also computed.At both sites, areal and volumetric BMD, cortical thickness and trabecular number, separation, and distribution were significantly worse in cases than in controls, with differences ranging from À6% to 15%. mFE-derived stiffness and failure load were 8% to 9% lower in fractures ( p < .01). No difference in load distribution was found between the two groups. After adjustment for aBMD, only differences of mFE-derived stresses, stiffness, and failure load at the tibia remained significant ( p < .05).PCA resulted in defining 4 independent PCs, explaining 83% of the total variability of bone characteristics. Nonvertebral fractures were associated with PC1, reflecting bone quantity and strength at the radius (tibia) with OR ¼

This study demonstrated the good reproducibility of the HR-pQCT volumetric measurements at MCPs and confirmed the involvement of trabecular compartment in periarticular osteopoenia. Thus, HR-pQCT appears interesting to simultaneously assess differences in bone volumetric density, microarchitecture and erosions.

Areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry (DXA) identifies 20% of men who will sustain fragility fractures. Thus we need better fracture predictors in men. We assessed the association between the low-trauma prevalent fractures and bone microarchitecture assessed at the distal radius and tibia by high-resolution peripheral quantitative computed tomography (HRpQCT) in 920 men aged 50 years of older. Ninety-eight men had vertebral fractures identified on the vertebral fracture assessment software of the Hologic Discovery A device using the semiquantitative criteria, whereas 100 men reported low-trauma peripheral fractures. Men with vertebral fractures had poor bone microarchitecture. However, in the men with vertebral fractures, only cortical volumetric density (D.cort) and cortical thickness (C.Th) remained significantly lower at both the radius and tibia after adjustment for aBMD of ultradistal radius and hip, respectively. Low D.cort and C.Th were associated with higher prevalence of vertebral fractures regardless of aBMD. Severe vertebral fractures also were associated with poor trabecular microarchitecture regardless of aBMD. Men with peripheral fractures had poor bone microarchitecture. However, after adjustment for aBMD, all microarchitectural parameters became nonsignificant. In 15 men with multiple peripheral fractures, trabecular spacing and distribution remained increased after adjustment for aBMD. Thus, in men, vertebral fractures and their severity are associated with impaired cortical bone, even after adjustment for aBMD. The association between peripheral fractures and bone microarchitecture was weaker and nonsignificant after adjustment for aBMD. Thus bone microarchitecture may be a determinant of bone fragility in men, which should be investigated in prospective studies. ß

Risk for premature osteoporosis is a major health concern in astronauts and cosmonauts; the reversibility of the bone lost at the weight-bearing bone sites is not established, although it is suspected to take longer than the mission length. The bone three-dimensional structure and strength that could be uniquely affected by weightlessness is currently unknown. Our objective is to evaluate bone mass, microarchitecture, and strength of weight-bearing and non-weight-bearing bone in 13 cosmonauts before and for 12 months after a 4-month to 6-month sojourn in the International Space Station (ISS). Standard and advanced evaluations of trabecular and cortical parameters were performed using high-resolution peripheral quantitative computed tomography. In particular, cortical analyses involved determination of the largest common volume of each successive individual scan to improve the precision of cortical porosity and density measurements. Bone resorption and formation serum markers, and markers reflecting osteocyte activity or periosteal metabolism (sclerostin, periostin) were evaluated. At the tibia, in addition to decreased bone mineral densities at cortical and trabecular compartments, a 4% decrease in cortical thickness and a 15% increase in cortical porosity were observed at landing. Cortical size and density subsequently recovered and serum periostin changes were associated with cortical recovery during the year after landing. However, tibial cortical porosity or trabecular bone failed to recover, resulting in compromised strength. The radius, preserved at landing, unexpectedly developed postflight fragility, from 3 months post-landing onward, particularly in its cortical structure. Remodeling markers, uncoupled in favor of bone resorption at landing, returned to preflight values within 6 months, then declined farther to lower than preflight values. Our findings highlight the need for specific protective measures not only during, but also after spaceflight, because of continuing uncertainties regarding skeletal recovery long after landing. © 2017 American Society for Bone and Mineral Research.

Obesity is associated with higher areal bone density (aBMD) but its protective effect on the risk of fracture is controversial. We aimed to analyze bone microarchitecture and biomechanical properties in obese (OB) postmenopausal French women compared with normal weight (NW) women. A matched case-control study from the Os des Femmes de Lyon (OFELY) cohort was conducted in 63 OB women (body mass index [BMI] > 30, mean age 69 AE 8 years) age-matched with 126 NW women (19 BMI 25). Bone architecture was measured with high-resolution pQCT at the distal radius and tibia and bone strength was assessed by micro-finite element analysis (µFEA). aBMD, total body fat mass (FM) and lean mass (LM) were measured by dual-energy X-ray absorptiometry (DXA). aBMD was 15% higher at the total hip in OB compared with NW women. At the radius, OB had 13% and 14% higher volumetric total and trabecular bone densities, 11% higher cortical thickness, 13% greater trabecular number, and 22% lower distribution of trabecular separation compared with NW (p adjusted for height, physical activity, and medication use, <0.01 for all). Differences of a similar magnitude were found at the distal tibia. At both sites, µFEA showed significant higher values of bone strength in OB compared to controls. After normalizing values for individual body weight, we observed that all the parameters were relatively lower in OB compared to NW women. The increase of FM was fourfold greater than the increase of LM in OB. The effect of FM on bone parameters was more pronounced at the tibia compared to the non-weight-bearing site. Nevertheless, the coefficients of correlation were about one-half of those of LM for the biomechanical parameters. We conclude that higher absolute values of bone densities, cortical and trabecular architecture, and strength indices were not in proportion to the excess of BMI and particularly of FM in obese postmenopausal French women.

Few data concern the relationship between bone turnover and microarchitecture in men. We investigated the association between levels of biochemical markers of bone turnover (BTM) and bone microarchitecture in 1149 men aged 19 to 85 years. Bone microarchitecture was assessed by high-resolution peripheral quantitative computed tomography at the distal radius and tibia. Bone formation was assessed by serum osteocalcin, bone alkaline phosphatase, and N-terminal extension propeptide of type I collagen. Bone resorption was assessed by serum C-terminal telopeptide of type I collagen and urinary excretion of total deoxypyridinoline. BTM levels were high in young men and decreased until age 50 years. Urinary deoxypyridinoline (DPD) increased after age 70 years, whereas other BTMs remained stable. Before 50 years of age, only cortical volumetric bone mineral density (D cort ) correlated negatively with BTM levels. Between 50 and 70 years of age, D cort and some microarchitectural parameters correlated significantly with BTM at the radius and tibia. After 70 years of age, higher BTM levels were associated with lower cortical thickness and D cort at both the skeletal sites. At the distal radius, men in the highest BTM quartile had lower trabecular density, number (Tb.N), and thickness (Tb.Th) and more heterogeneous trabecular distribution compared with men in the lower quartiles. At the distal tibia, higher BTM levels were associated with lower Tb.N and Tb.Th in the central but not subendocortical area. Thus, in men, bone microarchitecture depends weakly on the current bone turnover rate until age 70. Thereafter, bone turnover seems to be a significant determinant of bone microarchitecture. ß