Alterations of cortical and trabecular architecture are associated with fractures in postmenopausal women, partially independent of decreased BMD measured by DXA: the OFELY study

Peripheral quantitative computed tomography (pQCT)-based finite element analysis provides enhanced diagnostic performance in identifying non-vertebral fracture patients compared with dual-energy X-ray absorptiometry

Due to limitations of the predominant clinical method for diagnosing osteoporosis, an engineering model based on a dedicated CT scanner for bone density and structure was applied in fracture patients and controls. Improved diagnostic performance was observed, which supports its potential use in future research and clinical practice.

INTRODUCTION

Dual-energy X-ray absorptiometry (DXA), the predominant clinical method for diagnosing osteoporosis, has limitations in identifying individuals with increased fracture risk. Peripheral quantitative computed tomography (pQCT) provides additional information and can be used to generate finite element (FE) models from which bone strength properties can be estimated. We investigated the ability of pQCT-FE properties to distinguish peripheral low-trauma fracture patients from healthy controls, by comparison with DXA and standard pQCT.

METHODS

One hundred and eight fracture patients (77 females aged 67.7 ± 7.9 years, 31 males aged 69.7 ± 8.9 years) were recruited from a hospital fracture liaison service. One hundred and twenty healthy community controls (85 females aged 69.8 ± 8.5 years, 35 males aged 68.9 ± 7.2 years) were recruited.

RESULTS

Significant differences between groups were observed in pQCT-FE properties, especially at the 4% tibia site. Fracture odds increased most per standard deviation decrease in pQCT-FE at this location [shear stiffness estimate, k_shear, in females, OR = 10.34, 95% CI (1.91, 43.98); bending stiffness estimate, k_bend, in males, OR = 8.32, 95% CI (4.15, 33.84)]. Area under the receiver operating characteristics curve (AUROC) was observed to be highest with pQCT-FE properties at 4% the tibia site. In females, this was 0.83 for the pQCT-FE variable k_shear, compared with 0.72 for DXA total hip bone density (TH aBMD) and 0.76 for pQCT tibia trabecular density (Trb vBMD); in males, this was 0.81 for the pQCT-FE variable k_bend at the 4% tibia site, compared with 0.62 for TH aBMD and 0.71 for Trb vBMD. There were significant differences in AUROC between DXA and pQCT-FE variables in both females (p = 0.02) and males (p = 0.03), while no difference was observed in AUROC between primary pQCT and pQCT-FE variables.

CONCLUSIONS

pQCT-FE modeling can provide enhanced diagnostic performance compared with DXA and, given its moderate cost, may be useful in clinical settings.

Growth from birth to adolescence and bone mineral density in young adults: The 1993 Pelotas birth cohort

BACKGROUND

The study examined the association of body size (weight and length) at birth and gain in height and weight during childhood and adolescence with areal bone mineral density (aBMD) in adulthood for women and men.

METHODS

756 members (335 men and 421 women) of the 1993 Pelotas (Brazil) Birth cohort were studied. Data on weight and length/height were obtained at birth and subsequent follow-ups at 1, 4, 11, 15, 18, and 22 years of age and specific z scores were calculated by sex. The outcome was whole body aBMD (g/cm²) measured at 22 years of age using dual-energy X-ray absorptiometry (DXA). The effects of exposures, weight and length/height gain, were analyzed using conditional relative weight (CWh) and conditional length/height (CH). Linear regression models were adjusted for multiple confounders, including mother's educational level, family income, maternal smoking during pregnancy, gestational age, breastfeeding and skin color.

RESULTS

In the adjusted models, among men greater height gain at 4, 11, and 18 years of age was associated with higher whole body aBMD, and the result with greatest magnitude was at 11 years of age (β 0.018 g/cm²; 95%CI 0.006; 0.030). Among women, aBMD was associated with height gain at all assessments from 1-15 years, with greatest effect size at 4 years of age (β 0.017 g/cm²; 95%CI 0.007; 0.027). Regarding to body weight, among men, greater weight at 4 and 15 years were associated with higher aBMD, with the highest coefficients for 15 years of age (β 0.015 g/cm²; 95%CI 0.003; 0.027); for women, except at birth, all weight gain variables were associated with aBMD and the highest coefficients were observed at 4 years (β 0.025 g/cm²; 95%CI 0.015; 0.035).

CONCLUSIONS

In this birth cohort, height and weight gain, especially from 4 to 15 years have important positive implications for aBMD to early adulthood.

Progressive structural bone changes and their relationship with treatment in patients with psoriatic arthritis: a longitudinal HR-pQCT study

Background

Although the short-term effects of tumor necrosis factor alpha (TNF-α) and interleukin-17A (IL-17A) inhibition on the structural changes in psoriatic arthritis (PsA) using high-resolution peripheral quantitative computed tomography (HR-pQCT) have been reported, no studies have investigated the long-term structural changes in PsA patients receiving routine care. We reported longitudinal changes of erosions and enthesiophytes using HR-pQCT and their relationship with treatments in PsA patients over a 5-year period.

Methods

HR-pQCT examination at the second and third metacarpal heads (MCH2 and MCH3) was performed in 60 PsA patients at baseline and after 5 years. The size of each individual lesion was quantified. Erosion and enthesiophyte progression were defined as change exceeding the smallest detectable change (SDC).

Results

A total of 108 bone erosions and 99 enthesiophytes were detected at baseline. Three new bone erosions but no new enthesiophytes were evident at 5 years. A significant increase in mean (±SD) erosion (0.58 ± 1.50 mm³, P < 0.001) and enthesiophyte (0.47 ± 0.76 mm³, P < 0.001) volume was observed. Erosion and enthesiophyte progression were found in 37/111 (33.3%) and 50/99 (50.5%) lesions, respectively. During this 5-year period, 26 (43%) out of the 60 patients achieved sustained Disease Activity index for PSoriatic Arthritis (DAPSA) low disease activity (LDA) (SDL group, defined as achieving DAPSA-LDA at both baseline and 5 years). Fourteen (23%) out of 60 patients received a TNF inhibitor throughout the 5-year period (TNFi group). Fewer erosions progressed (12/51 [23.5%] vs 25/60 [41.7%], P = 0.047) and the increased in enthesiophyte volume was significantly less (0.28 ± 0.67 vs 0.61 ± 0.80 mm³, P = 0.048) in the SDL group than in the non-SDL group. However, no significant difference between the TNFi and non-TNFi groups was detected in terms of the change in volume or progression of bone erosion and enthesiophyte.

Conclusion

Damage accrual in terms of bone erosion and enthesiophyte was observed in PsA patients over a period of 5 years despite receiving routine clinical care. Nonetheless, sustained control of disease activity may be able to prevent these bony damages.

Cluster Analysis of Finite Element Analysis and Bone Microarchitectural Parameters Identifies Phenotypes with High Fracture Risk

High-resolution peripheral quantitative computed tomography (HRpQCT) is increasingly used for exploring associations between bone microarchitectural and finite element analysis (FEA) parameters and fracture. We hypothesised that combining bone microarchitectural parameters, geometry, BMD and FEA estimates of bone strength from HRpQCT may improve discrimination of fragility fractures. The analysis sample comprised of 359 participants (aged 72-81 years) from the Hertfordshire Cohort Study. Fracture history was determined by self-report and vertebral fracture assessment. Participants underwent HRpQCT scans of the distal radius and DXA scans of the proximal femur and lateral spine. Poisson regression with robust variance estimation was used to derive relative risks for the relationship between individual bone microarchitectural and FEA parameters and previous fracture. Cluster analysis of these parameters was then performed to identify phenotypes associated with fracture prevalence. Receiver operating characteristic analysis suggested that bone microarchitectural parameters improved fracture discrimination compared to aBMD alone, whereas further inclusion of FEA parameters resulted in minimal improvements. Cluster analysis (k-means) identified four clusters. The first had lower Young modulus, cortical thickness, cortical volumetric density and Von Mises stresses compared to the wider sample; fracture rates were only significantly greater among women (relative risk [95%CI] compared to lowest risk cluster: 2.55 [1.28, 5.07], p = 0.008). The second cluster in women had greater trabecular separation, lower trabecular volumetric density and lower trabecular load with an increase in fracture rate compared to lowest risk cluster (1.93 [0.98, 3.78], p = 0.057). These findings may help inform intervention strategies for the prevention and management of osteoporosis.

High FGF23 levels are associated with impaired trabecular bone microarchitecture in patients with osteoporosis

This cross-sectional study examined the associations between c-terminal FGF23 levels, laboratory markers of bone metabolism and bone microarchitecture in 82 patients with osteoporosis. Higher FGF23 levels were associated with impaired trabecular but not cortical bone microarchitecture, and this was confirmed after adjusting for confounding variables such as age or BMI.

INTRODUCTION

Fibroblast growth factor 23 (FGF23) is an endocrine hormone-regulating phosphate and vitamin D metabolism. While its mode of action is well understood in diseases such as hereditary forms of rickets or tumor-induced osteomalacia, the interpretation of FGF23 levels in patients with osteoporosis with regard to bone microarchitecture is less clear.

METHODS

C-terminal FGF23 levels and bone turnover markers were assessed in 82 patients with osteoporosis (i.e., DXA T-score ≤ - 2.5 at the lumbar spine or total hip). Bone microarchitecture was measured by high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal radius and tibia. Data were analyzed in a cross-sectional design using correlation and regression models.

RESULTS

We found a significant negative logarithmic correlation between FGF23 levels and trabecular but not cortical bone microarchitecture at both skeletal sites. Furthermore, using a multiple linear regression model, we confirmed FGF23 as a predictor for reduced trabecular parameters even when adjusting for confounding factors such as age, BMI, phosphate, bone-specific alkaline phosphatase, vitamin D3, and PTH.

CONCLUSIONS

Taken together, high FGF23 levels are associated with impaired trabecular bone microarchitecture in osteoporosis patients, and this association seems to occur after adjustment of confounding variables including phosphate and vitamin D. Future longitudinal studies are now needed to validate our findings and investigate FGF23 in relation to fracture risk.

Assessment of proximal femur microarchitecture using ultra-high field MRI at 7 Tesla

PURPOSE

The purpose of this study was to investigate bone microarchitecture of cadaveric proximal femurs using ultra-high field (UHF) 7-Tesla magnetic resonance imaging (MRI) and to compare the corresponding metrics with failure load assessed during mechanical compression test and areal bone mineral density (ABMD) measured using dual-energy X-ray absorptiometry.

MATERIALS AND METHODS

ABMD of ten proximal femurs from five cadavers (5 women; mean age=86.2±3.8 (SD) years; range: 82.5-90 years) were investigated using dual-energy X-ray absorptiometry and the bone volume fraction, trabecular thickness, trabecular spacing, fractal dimension, Euler characteristics, connectivity density and degree of anisotropy of each femur was quantified using UHF MRI. The whole set of specimens underwent mechanical compression tests to failure. The inter-rater reliability of microarchitecture characterization was assessed with the intraclass correlation coefficient (ICC). Associations were searched using correlation tests and multiple regression analysis.

RESULTS

The inter-rater reliability for bone microarchitecture parameters measurement was good with ICC ranging from 0.80 and 0.91. ABMD and the whole set of microarchitecture metrics but connectivity density significantly correlated with failure load. Microarchitecture metrics correlated to each other but did not correlate with ABMD. Multiple regression analysis disclosed that the combination of microarchitecture metrics and ABMD improved the association with failure load.

CONCLUSION

Femur bone microarchitecture metrics quantified using UHF MRI significantly correlated with biomechanical parameters. The multimodal assessment of ABMD and trabecular bone microarchitecture using UHF MRI provides more information about fracture risk of femoral bone and might be of interest for future investigations of patients with undetected osteoporosis.

Bone microarchitecture and bone turnover in hepatic cirrhosis

Liver cirrhosis leads to bone loss. To date, information on bone quality (three-dimensional microarchitecture) and, thus, bone strength is scarce. We observed decreased bone quality at both assessed sites, independent of disease severity. Therefore, all patients should undergo early-stage screening for osteoporosis.

INTRODUCTION

Recent studies found low bone mineral density in cirrhosis, but data on bone microstructure are scarce. This study assessed weight-bearing and non-weight-bearing bones in patients with cirrhosis and healthy controls. The primary objective was to evaluate trabecular and cortical microarchitecture.

METHODS

This was a single-center study in patients with recently diagnosed hepatic cirrhosis. Thirty-two patients and 32 controls participated in this study. After determining the type of cirrhosis, the parameters of bone microarchitecture were assessed by high-resolution peripheral quantitative computed tomography.

RESULTS

Both cortical and trabecular microarchitectures showed significant alterations. At the radius, trabecular bone volume fraction was 17% lower (corrected p = 0.028), and, at the tibia, differences were slightly more pronounced. Trabecular bone volume fraction was 19% lower (p = 0.024), cortical bone mineral density 7% (p = 0.007), and cortical thickness 28% (p = 0.001), while cortical porosity was 32% higher (p = 0.023), compared to controls. Areal bone mineral density was lower (lumbar spine - 13%, total hip - 11%, total body - 9%, radius - 17%, and calcaneus - 26%). There was no correlation between disease severity and microarchitecture. Areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry (DXA) correlated well with parameters of cortical and trabecular microarchitecture.

CONCLUSIONS

Hepatic cirrhosis deteriorates both trabecular and cortical microarchitecture, regardless of disease severity. Areal bone mineral density is diminished at all sites as a sign of generalized affection. In patients with hepatic cirrhosis, regardless of its origin or disease severity, aBMD measurements are an appropriate tool for osteologic screening.

Women's Values and Preferences Regarding Osteoporosis Treatments: A Systematic Review

BACKGROUND

Several treatments are available to reduce the risk of fragility fractures associated with osteoporosis. The choice of treatment requires knowledge of patients' values and preferences. The aim of the present study was to summarize what is known about the values and preferences relevant to the management of osteoporosis in women.

METHODS

We conducted a comprehensive search of several databases for studies reported in any language that had included women who had already started or were about to start any pharmacological therapy for osteoporosis. Pairs of reviewers independently selected the studies and extracted the data. The results were synthesized narratively.

RESULTS

We included 26 studies reporting on 15,348 women (mean age, 66 years). The women considered the effectiveness and adverse events equally, followed by the convenience of taking the drug and its effect on daily routine (less frequent dosing was preferred, the oral route was preferred, and the injectable route was preferred over oral if given less frequently). The treatment cost and duration were less important factors for decision making. Fear of breast cancer and fear of resuming uterine bleeding were common reasons for not choosing estrogen therapy. Calcium and vitamin D were viewed as safe and natural. Across the studies, the preferences were not affected by age, previous drug exposure, or employment status.

CONCLUSIONS

Women starting osteoporosis medications value effectiveness and side effects equally and prefer medications given less frequently. Injectable drugs appear acceptable if given less frequently. More research on patient values and preferences is needed to guide decision making in osteoporosis.

Porous Phosphate-Based Glass Microspheres Show Biocompatibility, Tissue Infiltration, and Osteogenic Onset in an Ovine Bone Defect Model

Phosphate-based glasses (PBGs) are bioactive and fully degradable materials with tailorable degradation rates. PBGs can be produced as porous microspheres through a single-step process, using changes in their formulation and geometry to produce varying pore sizes and interconnectivity for use in a range of applications, including biomedical use. Calcium phosphate PBGs have recently been proposed as orthobiologics, based on their in vitro cytocompatibility and ion release profile. In this study, porous microspheres made of two PBG formulations either containing TiO₂ (P40Ti) or without (P40) were implanted in vivo in a large animal model of bone defect. The biocompatibility and osteogenic potential of these porous materials were assessed 13 weeks postimplantation in sheep and compared to empty defects and autologous bone grafts used as negative and positive controls. Histological analysis showed marked differences between the two formulations, as lower trabeculae-like interconnection and higher fatty bone marrow content were observed in the faster degrading P40-implanted defects, while the slower degrading P40Ti material promoted dense interconnected tissue. Autologous bone marrow concentrate (BMC) was also incorporated within the P40 and P40Ti microspheres in some defects; however, no significant differences were observed in comparison to microspheres implanted alone. Both formulations induced the formation of a collagen-enriched matrix, from 20 to 40% for P40 and P40Ti2.5 groups, suggesting commitment toward the bone lineage. With the faster degrading P40 formulation, mineralization of the tissue matrix was observed both with and without BMC. Some lymphocyte-like cells and foreign body multinucleated giant cells were observed with P40Ti2.5, suggesting that this more durable formulation might be linked to an inflammatory response. In conclusion, these first in vivo results indicate that PBG microspheres could be useful candidates for bone repair and regenerative medicine strategies and highlight the role of material degradation in the process of tissue formation and maturation.

Th17 cell frequency is associated with low bone mass in primary sclerosing cholangitis

BACKGROUND & AIMS

Osteoporotic fractures are a major cause of morbidity and reduced quality of life in patients with primary sclerosing cholangitis (PSC), a progressive bile duct disease of unknown origin. Although it is generally assumed that this pathology is a consequence of impaired calcium homeostasis and malabsorption, the cellular and molecular causes of PSC-associated osteoporosis are unknown.

METHODS

We determined bone mineral density by dual-X-ray absorptiometry and assessed bone microstructure by high-resolution peripheral quantitative computed tomography in patients with PSC. Laboratory markers of liver and bone metabolism were measured, and liver stiffness was assessed by FibroScan. We determined the frequency of Th17 cells by the ex vivo stimulation of peripheral blood mononuclear cells in a subgroup of 40 patients with PSC. To investigate the potential involvement of IL-17 in PSC-associated bone loss, we analyzed the skeletal phenotype of mice lacking Abcb4 and/or Il-17.

RESULTS

Unlike in patients with primary biliary cholangitis, bone loss in patients with PSC was not associated with disease duration or liver fibrosis. However, we observed a significant negative correlation between the bone resorption biomarker deoxypyridinoline and bone mineral density in the PSC cohort, indicating increased bone resorption. Importantly, the frequency of Th17 cells in peripheral blood was positively correlated with the urinary deoxypyridinoline level and negatively correlated with bone mass. We observed that Abcb4-deficient mice displayed a low-bone-mass phenotype, which was corrected by an additional Il-17 deficiency or anti-IL-17 treatment, whereas the liver pathology was unaffected.

CONCLUSIONS

Our findings demonstrate that an increased frequency of Th17 cells is associated with bone resorption in PSC. Whether antibody-based IL-17 blockade is beneficial against bone loss in patients with PSC should be addressed in future studies.

LAY SUMMARY

Primary sclerosing cholangitis (PSC) is a cholestatic liver disease characterized by progressive bile duct destruction. One serious complication of PSC is reduced bone mass resulting in increased fracture risk. Herein, we demonstrate that Th17 cells mediate bone loss in PSC by inducing bone resorption, which suggests that antibody-based IL-17 blockade might be beneficial for the treatment of bone loss in affected patients.

Impact of Weight Loss With Intragastric Balloon on Bone Density and Microstructure in Obese Adults

The historical concept that obesity protects against bone fractures has been questioned. Weight loss appears to reduce bone mineral density (BMD); however, the results in young adults are inconsistent, and data on the effects of weight loss on bone microstructure are limited. This study aimed to evaluate the impact of weight loss using an intragastric balloon (IGB) on bone density and microstructure. Forty obese patients with metabolic syndrome (mean age 35.1 ± 7.3 yr) used an IGB continuously for 6 mo. Laboratory tests, areal BMD, and body composition measurements via dual-energy X-ray absorptiometry, and volumetric BMD and bone microstructure measurements via high-resolution peripheral quantitative computed tomography were conducted before IGB placement and after IGB removal. The mean weight loss was 11.5%. After 6 mo, there were significant increases in vitamin D and carboxyterminal telopeptide of type 1 collagen levels. After IGB use, areal BMD increased in the spine but decreased in the total femur and the 33% radius. Cortical BMD increased in the distal radius but tended to decrease in the distal tibia. The observed trabecular bone loss in the distal tibia contributed to the decline in the total volumetric BMD at this site. There was a negative correlation between the changes in leptin levels and the measures of trabecular quality in the tibia on high-resolutionperipheral quantitative computed tomography. Weight loss may negatively impact bone microstructure in young patients, especially for weight-bearing bones, in which obesity has a more prominent effect.

Pediatric bone evaluation with HR-pQCT: A comparison between standard and height-adjusted positioning protocols in a cohort of teenagers with chronic kidney disease

BACKGROUND

High-resolution peripheral quantitative computed tomography (HR-pQCT) evaluates different components of bone fragility. The positioning and length of the region of interest (ROI) in growing populations remain to be defined.

METHODS

Using HR-pQCT at the ultradistal tibia, we compared a single-center cohort of 28 teenagers with chronic kidney disease (CKD) at a median age of 13.6 (range, 10.2-19.9) years to local age-, gender-, and puberty-matched healthy peers. Because of the potential impact of short stature, bone parameters were assessed on two different leg-length-adjusted ROIs in comparison to the standard analysis, namely the one applied in adults. The results are presented as median (range).

RESULTS

After matching, SDS height was -0.9 (-3.3;1.6) and 0.3 (-1.4;2.0) in patients and controls, respectively (P<0.001). In younger children (e.g., prepubertal, n=11), bone texture parameters and bone strength were not different using standard analysis. However, using a height-adjusted ROI enabled better characterization of cortical bone structure. In older patients (e.g., pubertal, n=17), there were no differences for height between patients and controls: with the standard evaluation, cortical bone area and cortical thickness were significantly lower in CKD patients: 85 (50-124) vs. 108 (67-154) mm² and 0.89 (0.46-1.31) vs 1.09 (0.60-1.62) mm, respectively (both P<0.05).

CONCLUSIONS

Adapting the ROI to leg length enables better assessment of bone structure, especially when height discrepancies exist between controls and patients. Larger cohorts are required to prospectively validate this analytic HR-pQCT technique.

Accurate and Efficient Plate and Rod Micro Finite Element Whole Bone Models Based on High-Resolution Peripheral Computed Tomography

The high-resolution peripheral quantitative computed tomography (HRpQCT) provides unprecedented visualization of bone microstructure and the basis for constructing patient-specific micro-finite element (µFE) models. Based on HRpQCT images, we have developed a plate rod µFE (PRµFE) method for whole bone segments using individual trabecula segmentation (ITS) and an adaptive cortical meshing technique. In contrast to the conventional voxel approach, the complex microarchitecture of the trabecular compartment is simplified into shell and beam elements based on the trabecular plate-and-rod configuration. Compared to voxel-based µFE models of µCT and mechanical testing, nonlinear analyses of stiffness and yield strength using the HRpQCT-based PRµFE models demonstrated high correlation and accuracy, indicating that the combination of segmented trabecular plate-rod morphology and adjusted cortical mesh adequately captures mechanics of the whole bone segment. Meanwhile, the PRµFE approach reduced model size by nearly 300-fold and shortened computation time for nonlinear analysis from days to within hours, permitting broader clinical application of HRpQCT-based nonlinear µFE modeling. Furthermore, the presented approach was tested using a subset of radius and tibia HRpQCT scans of patients with prior vertebral fracture from a previous study. Results indicated that yield strength for radius and tibia predicted by the PRµFE model was effective in discriminating vertebral fracture subjects from non-fractured controls. In conclusion, the PR µFE model of HRpQCT images accurately predicted mechanics for whole bone segments and can serve as a valuable clinical tool to evaluate musculoskeletal diseases.

Deficits in Bone Geometry in Growth Hormone-Deficient Prepubertal Boys Revealed by High-Resolution Peripheral Quantitative Computed Tomography

INTRODUCTION

Although growth hormone (GH) is essential for attainment of peak bone mass, bone health in prepubertal children with GH deficiency is not routinely evaluated. The objective of this study was to evaluate bone microarchitecture in GH-deficient (GHD) boys using high-resolution peripheral quantitative computed tomography (HR-pQCT).

METHODS

Fifteen control and fifteen GHD, GH naïve pre-pubertal boys were recruited for a case-control study at a major academic center. Subjects with panhypopituitarism, chromosomal pathology, chronic steroids, or stimulant use were excluded. Volumetric bone mineral density (vBMD; total, cortical, and trabecular), bone geometry (total, cortical and trabecular cross-sectional area, cortical perimeter), bone microarchitecture, and estimated bone strength of the distal radius and tibia were assessed by HR-pQCT. Areal BMD and body composition were assessed by DXA. Insulin-like growth factor 1 (IGF-1), osteocalcin, C telopeptide, and P1NP levels were measured.

RESULTS

GHD subjects had a significantly smaller cortical perimeter of the distal radius compared to controls (p < 0.001), with the difference in cortical perimeter persisting after adjusting for height z score, age, lean mass, and 25-hydroxyvitamin D level (p < 0.05).No significant differences were found in vBMD. No significant differences were found in microarchitecture, estimated strength, areal BMD, body composition, or bone turnover markers. Analysis showed significant positive correlations between IGF-1 levels and cortical parameters.

DISCUSSION/CONCLUSIONS

Prepubertal GHD boys had deficits in bone geometry not evident with DXA. Larger prospective/longitudinal HR-pQCT studies are needed to determine the extent of these deficits, the need for routine bone evaluation, and the timing of GH replacement for prevention or restoration of these deficits.

Cortical and trabecular bone microarchitecture as an independent predictor of incident fracture risk in older women and men in the Bone Microarchitecture International Consortium (BoMIC): a prospective study

BACKGROUND

Although areal bone mineral density (aBMD) assessed by dual-energy x-ray absorptiometry (DXA) is the clinical standard for determining fracture risk, most older adults who sustain a fracture have T scores greater than -2·5 and thus do not meet the clinical criteria for osteoporosis. Importantly, bone fragility is due to low BMD and deterioration in bone structure. We assessed whether indices of high-resolution peripheral quantitative CT (HR-pQCT) were associated with fracture risk independently of femoral neck aBMD and the Fracture Risk Assessment Tool (FRAX) score.

METHODS

We assessed participants in eight cohorts from the USA (Framingham, Mayo Clinic), France (QUALYOR, STRAMBO, OFELY), Switzerland (GERICO), Canada (CaMos), and Sweden (MrOS). We used Cox proportional hazard ratios (HRs) to estimate the association between HR-pQCT bone indices (per 1 SD of deficit) and incident fracture, adjusting for age, sex, height, weight, and cohort, and then additionally for femoral neck DXA aBMD or FRAX.

FINDINGS

7254 individuals (66% women and 34% men) were assessed. Mean baseline age was 69 years (SD 9, range 40-96). Over a mean follow-up of 4·63 years (SD 2·41) years, 765 (11%) participants had incident fractures, of whom 633 (86%) had femoral neck T scores greater than -2·5. After adjustment for age, sex, cohort, height, and weight, peripheral skeleton failure load had the greatest association with risk of fracture: tibia HR 2·40 (95% CI 1·98-2·91) and radius 2·13 (1·77-2·56) per 1 SD decrease. HRs for other bone indices ranged from 1·12 (95% CI 1·03-1·23) per 1 SD increase in tibia cortical porosity to 1·58 (1·45-1·72) per 1 SD decrease in radius trabecular volumetric bone density. After further adjustment for femoral neck aBMD or FRAX score, the associations were reduced but remained significant for most bone parameters. A model including cortical volumetric bone density, trabecular number, and trabecular thickness at the distal radius and a model including these indices plus cortical area at the tibia were the best predictors of fracture.

INTERPRETATION

HR-pQCT indices and failure load improved prediction of fracture beyond femoral neck aBMD or FRAX scores alone. Our findings from a large international cohort of men and women support previous reports that deficits in trabecular and cortical bone density and structure independently contribute to fracture risk. These measurements and morphological assessment of the peripheral skeleton might improve identification of people at the highest risk of fracture.

FUNDING

National Institutes of Health National Institute of Arthritis Musculoskeletal and Skin Diseases.

Electroacupuncture Prevents Ovariectomy-Induced Osteoporosis in Rats: A Randomised Controlled Trial

Background

Electroacupuncture (EA) treatment has been shown to increase bone mineral density (BMD) in ovariectomised (OVX) rats; however, the underlying mechanisms remain unclear.

Objective

To systematically evaluate the effects of EA on OVX rats and the Wnt/β-catenin signalling pathway.

Methods

Three-month-old female Sprague–Dawley rats were randomly divided into three different groups (n=10 each): sham operated control (sham operated), ovariectomy (OVX) and ovariectomy with EA treatment (OVX+EA). Rats in the OVX+EA group received 12-week EA treatments.

Results

Serum bone-specific alkaline phosphatase level (p<0.01), BMD of the proximal femoral metaphysis and the fifth lumbar (L5) vertebral body (both, p<0.05) and maximum load and energy to failure of L5 vertebral body (both p<0.01) were significantly higher in the OVX+EA group than in the OVX group. Trabecular area, trabecular width and trabecular number were significantly higher in the OVX+EA group by 66.9%, 29.2% and 30.3%, respectively, than in the OVX group (all, p<0.01). Trabecular separation was 31.9% lower in the OVX+EA group than in the OVX group (p<0.01). Quantitative real-time reverse transcription polymerised chain reaction indicated that the expressions of mRNAs for low-density lipoprotein receptor-related protein 5 and β-catenin were significantly increased in the OVX+EA group, as compared with the OVX group (p<0.01 and p<0.05, respectively).

Conclusion

This study demonstrates that EA can prevent OVX-induced bone loss and deterioration of bone architecture and strength by stimulating the Wnt/β-catenin signalling pathway. These findings suggest that EA may bet a promising adjunct method for inhibiting OVX-induced osteoporosis in clinical settings.

Comparison of Bone Microarchitecture Between Adult Osteogenesis Imperfecta and Early-Onset Osteoporosis

Diagnosis and management of adult individuals with low bone mass and increased bone fragility before the age of 50 can be challenging. A number of these patients are diagnosed with mild osteogenesis imperfecta (OI) through detection of COL1A1 or COL1A2 mutations; however, a clinical differentiation from early-onset osteoporosis (EOOP) may be difficult. The purpose of this study was to determine the bone microstructural differences between mild OI and EOOP patients. 29 patients showed mutations in COL1A1 or COL1A2 and were classified as OI. Skeletal assessment included dual-energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HR-pQCT), and bone turnover serum analyses. Bone microstructure of 21/29 OI patients was assessed and compared to 23 age- and sex-matched patients clinically classified EOOP but without mutations in the known disease genes as well as to 20 healthy controls. In the OI patients, we did not observe an age-dependent decrease in DXA Z-scores. HR-pQCT revealed a significant reduction in volumetric BMD and microstructural parameters in the distal radius and tibia in both the OI and EOOP cohorts compared to the healthy controls. When comparing the bone microstructure of OI patients with the EOOP cohort, significant differences were found in terms of bone geometry in the radius, while no significant changes were detected in all other HR-pQCT parameters at the radius and tibia. Taken together, adult mild OI patients demonstrate a predominantly high bone turnover trabecular bone loss syndrome that shows minor microstructural differences compared to EOOP without mutation detection.

Trabecular bone microarchitecture predicts fragility fractures in postmenopausal women on denosumab treatment

BACKGROUND

High-resolution peripheral quantitative computed tomography (HR-pQCT) represents a three-dimensional tool for the screening of osteoporosis patients i.e., regarding fracture risk. The purpose of this study was to determine the baseline and follow-up bone microarchitecture in relation to incident fracture risk in postmenopausal women on denosumab treatment.

METHODS

We have retrospectively evaluated data from 182 postmenopausal women treated with denosumab that underwent an initial HR-pQCT scan before the initiation of the treatment; and at least one second HR-pQCT after 12 months. Women were assigned to two groups based on documented fragility fractures for the following 2.9 ± 1.1 years: fracture (n = 22) and no fracture (n = 160). Baseline parameters from DXA, HR-pQCT and bone turnover were compared between the two groups. Furthermore, ROC and multiple regression analyses of the baseline and follow-up data were performed to evaluate the predictive value regarding incident fractures.

RESULTS

At baseline, trabecular parameters were significantly reduced in the fracture group and showed the best predictive value for new fractures, while DXA results could not predict fractures. A multiple regression model identified BV/TV and age as the best baseline parameters for incident fracture risk. At 12 months, cortical and trabecular parameters increased in the non-fracture group, while no significant increase was noted in the fracture group. However, no significant differences regarding the changes of these parameters could be detected between the non-fracture and fracture cohort.

CONCLUSIONS

Trabecular bone microstructure at baseline is crucial for incident fracture risk in postmenopausal women on denosumab treatment, especially in comparison to DXA values. In this context, the microstructural follow-up results seemed to be of lesser importance regarding fracture risk. The results of this exploratory study should be validated in independent populations.

Harmonizing finite element modelling for non-invasive strength estimation by high-resolution peripheral quantitative computed tomography

The finite element (FE) method based on high-resolution peripheral quantitative computed tomography (HR-pQCT) use a variety of tissue constitutive properties and boundary conditions at different laboratories making comparison of mechanical properties difficult. Furthermore, the advent of a second-generation HR-pQCT poses challenges due to improved resolution and a larger region of interest (ROI). This study addresses the need to harmonize results across FE models. The aims are to establish the relationship between FE results as a function of boundary conditions and a range of tissue properties for the first-generation HR-pQCT system, and to determine appropriate model parameters for the second-generation HR-pQCT system. We implemented common boundary conditions and tissue properties on a large cohort (N = 1371), and showed the relationships were highly linear (R² > 0.99) for yield strength and reaction force between FE models. Cadaver radii measured on both generation HR-pQCT with matched ROIs were used to back-calculate a tissue modulus that accounts for the increased resolution (61 µm versus 82 µm), resulting in a modulus of 8748 MPa for second-generation HR-pQCT to produce bone yield strength and reaction force equivalent to using 6829 MPa for first-generation HR-pQCT. Finally, in vivo scans (N = 61) conducted on both generations demonstrated that the larger ROI in the second-generation system results in stronger bone outcome measures, suggesting it is not advisable to convert FE results across HR-pQCT generations without matching ROIs. Together, these findings harmonize FE results by providing a means to compare findings with different boundary conditions and tissue properties, and across scanner generations.

Association of High-resolution Peripheral Quantitative Computed Tomography (HR-pQCT) bone microarchitectural parameters with previous clinical fracture in older men: The Osteoporotic Fractures in Men (MrOS) study

High-resolution peripheral quantitative computed tomography (HR-pQCT) assesses both volumetric bone mineral density (vBMD) and trabecular and cortical microarchitecture. However, studies of the association of HR-pQCT parameters with fracture history have been small, predominantly limited to postmenopausal women, often performed limited adjustment for potential confounders including for BMD, and infrequently assessed strength or failure measures. We used data from the Osteoporotic Fractures in Men (MrOS) study, a prospective cohort study of community-dwelling men aged ≥65 years, to evaluate the association of distal radius, proximal (diaphyseal) tibia and distal tibia HR-pQCT parameters measured at the Year 14 (Y14) study visit with prior clinical fracture. The primary HR-pQCT exposure variables were finite element analysis estimated failure loads (EFL) for each skeletal site; secondary exposure variables were total vBMD, total bone area, trabecular vBMD, trabecular bone area, trabecular thickness, trabecular number, cortical vBMD, cortical bone area, cortical thickness, and cortical porosity. Clinical fractures were ascertained from questionnaires administered every 4 months between MrOS study baseline and the Y14 visit and centrally adjudicated by masked review of radiographic reports. We used multivariate-adjusted logistic regression to estimate the odds of prior clinical fracture per 1 SD decrement for each Y14 HR-pQCT parameter. Three hundred forty-four (19.2%) of the 1794 men with available HR-pQCT measures had a confirmed clinical fracture between baseline and Y14. After multivariable adjustment, including for total hip areal BMD, decreased HR-pQCT finite element analysis EFL for each site was associated with significantly greater odds of prior confirmed clinical fracture and major osteoporotic fracture. Among other HR-pQCT parameters, decreased cortical area appeared to have the strongest independent association with prior clinical fracture. Future studies should explore associations of HR-pQCT parameters with specific fracture types and risk of incident fractures and the impact of age and sex on these relationships.

Prediction of Fractures in Men Using Bone Microarchitectural Parameters Assessed by High-Resolution Peripheral Quantitative Computed Tomography-The Prospective STRAMBO Study

Areal bone mineral density (aBMD) poorly identifies men at high fracture risk. Our aim was to assess prediction of fractures in men by bone microarchitectural measures. At baseline, 825 men aged 60 to 87 years had the assessment of bone microarchitecture at distal radius and distal tibia by high-resolution peripheral QCT (HR-pQCT; XtremeCT-I, Scanco Medical, Brüttisellen, Switzerland). Bone strength was estimated by micro-finite element analysis. During the prospective 8-year follow-up, 105 men sustained fractures (59 vertebral fractures in 49 men and 70 nonvertebral fractures in 68 men). After adjustment for age, body mass index (BMI), prior falls, and fractures, most HR-pQCT measures at both skeletal sites predicted fractures. After further adjustment for aBMD, low distal radius trabecular number (Tb.N) was most strongly associated with higher fracture risk (hazard ratio [HR] = 1.63 per SD, 95% confidence interval [CI] 1.31-2.03, p < 0.001). In similar models, low Tb.N was associated with higher risk of major osteoporotic fracture (HR = 1.80 per SD, p < 0.001), vertebral fracture (HR = 1.78 per SD, p < 0.01) and nonvertebral fracture (HR = 1.46 per SD, p < 0.01). In comparison with the reference model (age, BMI, falls, fractures, aBMD), the adjustment for distal radius Tb.N increased the estimated fracture probability in men who sustained fractures versus those who did not have ones (difference = 4.1%, 95% CI 1.9-6.3%, p < 0.001). However, the adjustment for distal radius Tb.N did not increase the area under the curve (AUC, p = 0.37). Similar results were found for distal radius trabecular separation (Tb.Sp) and connectivity density (Conn. D). They were predictive of all fracture types and increased the estimated fracture risk, but not AUC, in men who had incident fractures. Thus, poor distal radius trabecular microarchitecture is predictive of fracture after adjustment for age, BMI, falls, fractures, and aBMD. Although distal radius Tb.N, Conn. D, and Tb.Sp improve the discrimination between men who will or who will not have fracture, they do not provide clinically relevant improvement of fracture prediction in older men. © 2018 American Society for Bone and Mineral Research.

Osteocyte-Intrinsic TGF-β Signaling Regulates Bone Quality through Perilacunar/Canalicular Remodeling

Poor bone quality contributes to bone fragility in diabetes, aging, and osteogenesis imperfecta. However, the mechanisms controlling bone quality are not well understood, contributing to the current lack of strategies to diagnose or treat bone quality deficits. Transforming growth factor beta (TGF-β) signaling is a crucial mechanism known to regulate the material quality of bone, but its cellular target in this regulation is unknown. Studies showing that osteocytes directly remodel their perilacunar/canalicular matrix led us to hypothesize that TGF-β controls bone quality through perilacunar/canalicular remodeling (PLR). Using inhibitors and mice with an osteocyte-intrinsic defect in TGF-β signaling (TβRII^ocy-/-), we show that TGF-β regulates PLR in a cell-intrinsic manner to control bone quality. Altogether, this study emphasizes that osteocytes are key in executing the biological control of bone quality through PLR, thereby highlighting the fundamental role of osteocyte-mediated PLR in bone homeostasis and fragility.

Low physical performance determined by chair rising test muscle mechanography is associated with prevalent fragility fractures

This study examined associations between physical performance assessed by chair rising test muscle mechanography and DXA T-score as well as body composition in a large patient cohort. Next to various significant interrelationships between these muscle and bone parameters, lower physical performance was associated with prevalent fragility fractures.

PURPOSE

Although the interaction between muscle and bone has been demonstrated in various aspects, the clinical focus in the diagnosis of musculoskeletal disorders mainly lies on the skeletal assessments. Accordingly, the association between muscle function, bone mineral density (BMD), and fragility fractures remains to be further elucidated with a feasible muscle assessment in a clinical setting.

METHODS

Patient data (2076 patients, 1538 women, 538 men) were evaluated retrospectively from a large dual energy X-ray absorptiometry (DXA) database as well as from chair rising test (CRT) that was performed on a muscle mechanograph. To determine potential predictors of the CRT time and maximum force, a multivariate regression analysis was performed including age, DXA T-score, and body composition indices. Furthermore, CRT results were compared between non-fracture and fracture cases.

RESULTS

We determined independent predictors for CRT time such as age, femoral DXA T-score, and total fat mass, whereas CRT force was only influenced by total lean mass. Both women and men with previous fragility fractures displayed a longer CRT time (women p = 0.009, men p = 0.001) and lower CRT force (women p < 0.001, men p < 0.001) than those with no fractures, while no clear differences in CRT results could be detected between normal BMD, osteopenia, and osteoporosis based on DXA T-scores.

CONCLUSIONS

Our study demonstrates that in addition to the associations between chair rising time and femoral T-score assessed by DXA, low muscle strength is associated with previous fragility fractures.

Biomechanical properties of bone are impaired in patients with ACPA-positive rheumatoid arthritis and associated with the occurrence of fractures

OBJECTIVES

Bone loss is a well-established consequence of rheumatoid arthritis (RA). To date, bone disease in RA is exclusively characterised by bone density measurements, while the functional properties of bone in RA are undefined. This study aimed to define the impact of RA on the functional properties of bone, such as failure load and stiffness.

METHODS

Micro-finite element analysis (µFEA) was carried out to measure failure load and stiffness of bone based on high-resolution peripheral quantitative CT data from the distal radius of anti-citrullinated protein antibody (ACPA)-positive RA (RA+), ACPA-negative RA (RA-) and healthy controls (HC). In addition, total, trabecular and cortical bone densities as well as microstructural parameters of bone were recorded. Correlations and multivariate models were used to determine the role of demographic, disease-specific and structural data of bone strength as well as its relation to prevalent fractures.

RESULTS

276 individuals were analysed. Failure load and stiffness (both P<0.001) of bone were decreased in RA+, but not RA-, compared with HC. Lower bone strength affected both female and male patients with RA+, was related to longer disease duration and significantly (stiffness P=0.020; failure load P=0.012) associated with the occurrence of osteoporotic fractures. Impaired bone strength was correlated with altered bone density and microstructural parameters, which were all decreased in RA+. Multivariate models showed that ACPA status (P=0.007) and sex (P<0.001) were independently associated with reduced biomechanical properties of bone in RA.

CONCLUSION

In summary, µFEA showed that bone strength is significantly decreased in RA+ and associated with fractures.

Volumetric Bone Mineral Density and Failure Load of Distal Limbs Predict Incident Clinical Fracture Independent HR-pQCT BMD and Failure Load Predicts Incident Clinical Fracture of FRAX and Clinical Risk Factors Among Older Men

Our objective was to determine the associations of peripheral bone strength and microarchitecture with incident clinical and major osteoporotic fracture among older men after adjusting for major clinical risk factors. We used a prospective cohort study design with data from 1794 men (mean age 84.4 years) in the Osteoporotic Fractures in Men (MrOS) study. Eligible men attended the year 14 visit, had high-resolution peripheral quantitative computed tomography (HR-pQCT) scans of the distal radius and distal or diaphyseal tibia, DXA measured BMD, and were followed for mean 1.7 years for incident fracture. Failure load was estimated using finite element analysis. We used Cox proportional hazards models with standardized HR-pQCT parameters as exposure variables. Primary outcome was clinical fracture (n = 108). Covariates included either Fracture Risk Assessment Tool (FRAX) major osteoporotic fracture probability calculated with BMD (FRAX-BMD), or individual clinical risk factors (CRF) including age, total hip BMD, race, falls, and prevalent fracture after age 50 years. Lower failure load was associated with higher risk of incident clinical fracture and incident major osteoporotic fracture. For clinical fracture with FRAX-BMD adjustment, the associations ranged from hazard ratio (HR) 1.58 (95% CI, 1.25 to 2.01) to 2.06 (95% CI, 1.60 to 2.66) per SD lower failure load at the diaphyseal tibia and distal radius. These associations were attenuated after adjustment for individual CRFs, but remained significant at the distal sites. Associations of volumetric BMD with these outcomes were similar to those for failure load. At the distal radius, lower trabecular BMD, number, and thickness, and lower cortical BMD, thickness, and area were all associated with higher risk of clinical fracture, but cortical porosity was not. Among community-dwelling older men, HR-pQCT measures including failure load, volumetric BMD, and microstructure parameters at peripheral sites (particularly distal radius) are robust independent predictors of clinical and major osteoporotic fracture. © 2018 American Society for Bone and Mineral Research.

Disease Duration and Stage Influence Bone Microstructure in Patients With Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is known to be a major risk factor for osteoporosis reflected by a reduction of bone mineral density (BMD). However, both the extent of the macro- and microstructural alterations of bone as well as the causative factors are unknown. We have retrospectively analyzed a total of 96 patients with PBC and 53 healthy controls matched for age, sex, and body mass index. In addition to dual-energy X-ray absorptiometry (DXA) measurements at the lumbar spine and hip, high-resolution peripheral quantitative computed tomography (HR-pQCT) was used to assess the geometric, volumetric, and microstructural changes of bone at the distal radius and tibia. Furthermore, serum analyses and measures of disease duration and stage including transient elastography were performed. Total, cortical, and trabecular volumetric BMD as well as geometric parameters were significantly reduced in PBC patients. Microstructural analysis revealed a significantly lower cortical thickness (p < 0.001) and bone volume per tissue volume (p < 0.001) in the radius and tibia but unchanged trabecular number in patients with PBC (radius: p = 0.42; tibia: p = 0.12). Multivariate regression models pointed out that disease duration and stage are the primary factors that are independently associated with bone loss in PBC. A subgroup analysis of patients with additional autoimmune hepatitis (AIH) revealed no significant changes in bone structure compared with PBC only. Taken together, PBC patients demonstrate severe alterations in bone microstructure that are positively associated with disease duration and stage. By applying HR-pQCT in the distal radius and tibia, a combined bone loss syndrome expressed by a predominant decrease in BMD and cortical thickness could be detected. © 2018 American Society for Bone and Mineral Research.

Effects of Gastric Bypass Surgery on Bone Mass and Microarchitecture Occur Early and Particularly Impact Postmenopausal Women

Roux-en-Y gastric bypass (RYGB) surgery is a highly effective treatment for obesity but negatively affects the skeleton. Studies of skeletal effects have generally examined areal bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA), but DXA may be inaccurate in the setting of marked weight loss. Further, as a result of modestly sized samples of mostly premenopausal women and very few men, effects of RYGB by sex and menopausal status are unknown. We prospectively studied the effects of RYGB on skeletal health, including axial and appendicular volumetric BMD and appendicular bone microarchitecture and estimated strength. Obese adults (N = 48; 27 premenopausal and 11 postmenopausal women, 10 men) with mean ± SD body mass index (BMI) 44 ± 7 kg/m² were assessed before and 6 and 12 months after RYGB. Participants underwent spine and hip DXA, spine QCT, radius and tibia HR-pQCT, and laboratory evaluation. Mean 12-month weight loss was 37 kg (30% of preoperative weight). Overall median 12-month increase in serum collagen type I C-telopeptide (CTx) was 278% (p < 0.0001), with greater increases in postmenopausal than premenopausal women (p = 0.049). Femoral neck BMD by DXA decreased by mean 5.0% and 8.0% over 6 and 12 months (p < 0.0001). Spinal BMD by QCT decreased by mean 6.6% and 8.1% (p < 0.0001); declines were larger among postmenopausal than premenopausal women (11.6% versus 6.0% at 12 months, p = 0.02). Radial and tibial BMD and estimated strength by HR-pQCT declined. At the tibia, detrimental changes in trabecular microarchitecture were apparent at 6 and 12 months. Cortical porosity increased at the radius and tibia, with more dramatic 12-month increases among postmenopausal than premenopausal women or men at the tibia (51.4% versus 18.3% versus 3.0%, p < 0.01 between groups). In conclusion, detrimental effects of RYGB on axial and appendicular bone mass and microarchitecture are detectable as early as 6 months postoperatively. Postmenopausal women are at highest risk for skeletal consequences and may warrant targeted screening or interventions. © 2017 American Society for Bone and Mineral Research.

Increased prevalence of asymptomatic vertebral fractures in HIV-infected patients over 50 years of age

The prevalence of asymptomatic vertebral fracture in HIV-infected patients over 50 was 20%, associated with older age, male sex, longer time since HIV diagnosis, and tubular renal alterations. Vertebral fractures were independent of osteoporosis at lumbar spine, and were not predicted by the use of the FRAX equation.

PURPOSE

Vertebral fractures (VF) are the hallmark of osteoporotic fractures. Our objective was to determine the prevalence of asymptomatic VF and associated factors in HIV-infected patients over 50 years, and the role of FRAX equation.

METHODS

In a cross-sectional study, a diagnosis of VF was established by the semiquantitative method of Genant in thoracic and lumbar radiographs. Simultaneously, a dual X-ray absorptiometry (DXA), bone and kidney-related analytical, calcium intake, physical exercise, HIV-related factors, and FRAX estimation were evaluated.

RESULTS

Overall, 128 patients (35 women, 27%) were included. Mean age was 57 years. Hypophosphatemia and tubular renal dysfunction were observed in 13 and 21%. DXA scan showed osteopenia and osteoporosis at hip in 65 and 7% of patients, and in spine in 39 and 34%, respectively. VF were observed in 26 patients (20%), with a trend to be associated with lower serum phosphate, increased alkaline phosphatase, and with lower daily calcium intake. In a multivariate analysis, older age (OR 1.2 per year; 14% of VF at 50-55; 44% at 65-70), male sex (26 vs 6%), longer time since HIV diagnosis, and renal and tubular dysfunction were the associated factors. VF were not related with osteoporosis at lumbar spine, and could not be predicted by the FRAX equation.

CONCLUSIONS

The prevalence of asymptomatic vertebral fractures is high in HIV-infected patients older than 50 years, and is not identified by the presence of osteoporosis in spine neither predicted by the FRAX equation. Spine and lumbar X-rays should be routinely performed in this aging population.

Bone Health After Bariatric Surgery

Bariatric surgery results in long-term weight loss and improvement or resolution in obesity-related comorbidities. However, mounting evidence indicates that it adversely affects bone health. This review summarizes clinical research findings about the impact of bariatric surgery on skeletal outcomes. The literature is the largest and strongest for the Roux-en-Y gastric bypass (RYGB) procedure, as RYGB was the most commonly performed bariatric procedure worldwide until it was very recently overtaken by the sleeve gastrectomy (SG). Because SG is a newer procedure, its skeletal effects have not yet been well defined. Epidemiologic studies have now demonstrated an increased risk of fracture after RYGB and biliopancreatic diversion with duodenal switch, both of which include a malabsorptive component. As these epidemiologic data have emerged, patient-oriented studies have elucidated the bone tissue-level changes that may account for the heightened skeletal fragility. Bariatric surgery induces early and dramatic increases in biochemical markers of bone turnover. A notable feature of recent patient-oriented clinical studies is the application of advanced skeletal imaging modalities; studies address the limitations of dual-energy X-ray absorptiometry (DXA) by using quantitative computed tomography (QCT)-based modalities to examine volumetric bone mineral density and compartment-specific density and microstructure. RYGB results in pronounced declines in bone mass at the axial skeleton demonstrated by DXA and QCT, as well as at the appendicular skeleton demonstrated by high-resolution peripheral quantitative computed tomography (HR-pQCT). RYGB has detrimental effects on trabecular and cortical microarchitecture and estimated bone strength. Skeletal changes after RYGB appear early and continue even after weight loss plateaus and weight stabilizes. The skeletal effects of bariatric surgery are presumably multifactorial, and mechanisms may involve nutritional factors, mechanical unloading, hormonal factors, and changes in body composition and bone marrow fat. Clinical guidelines address bone health and may mitigate the negative skeletal effects of surgery, although more research is needed to direct and support such guidelines. © 2018 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Lower Bone Density, Impaired Microarchitecture, and Strength Predict Future Fragility Fracture in Postmenopausal Women: 5-Year Follow-up of the Calgary CaMos Cohort

The aim of this prospective study was to use high-resolution peripheral quantitative computed tomography (HR-pQCT) to determine if baseline skeletal parameters can predict incident fragility fracture in women and, secondly, to establish if women that fracture lose bone at a faster rate than those who do not fracture. Women older than 60 years who experienced a fragility fracture during the 5-year follow-up period (incident fracture group, n = 22) were compared with those who did not experience a fragility fracture during the study (n = 127). After image registration between baseline and follow-up measures, standard and cortical morphological analyses were conducted. Odds ratios were calculated for baseline values and annualized percent change of HR-pQCT and finite element variables. At the radius, baseline HR-pQCT results show women who fractured had lower total bone mineral density (Tt.BMD; 19%), trabecular bone mineral density (Tb.BMD; 25%), and trabecular number (Tb.N; 14%), with higher trabecular separation (Tb.Sp; 19%) than women who did not fracture. At the tibia, women with incident fracture had lower Tt.BMD (15%), Tb.BMD (12%), cortical thickness (Ct.Th; 14%), cortical area (Ct.Ar; 12%), and failure load (10%) with higher total area (Tt.Ar; 7%) and trabecular area (Tb.Ar; 10%) than women who did not fracture. Odds ratios (ORs) at the radius revealed every SD decrease of Tt.BMD (OR = 2.1), Tb.BMD (OR = 2.0), and Tb.N (OR = 1.7) was associated with a significantly increased likelihood of fragility fracture. At the tibia, every SD decrease in Tt.BMD (OR = 2.1), Tb.BMD (OR = 1.7), Ct.Th (OR = 2.2), Ct.Ar (OR = 1.9), and failure load (OR = 1.7) were associated with a significantly increased likelihood of fragility fracture. Irrespective of scanning modality, the annualized percent rate of bone loss was not different between fracture groups. The results suggest baseline bone density, microarchitecture, and strength rather than change in these variables are associated with incident fragility fractures in women older than 60 years. Furthermore, irrespective of fragility fracture status, women experienced changes in skeletal health at a similar rate. © 2017 American Society for Bone and Mineral Research.

Bone-related Circulating MicroRNAs miR-29b-3p, miR-550a-3p, and miR-324-3p and their Association to Bone Microstructure and Histomorphometry

The assessment of bone quality and the prediction of fracture risk in idiopathic osteoporosis (IOP) are complex prospects as bone mineral density (BMD) and bone turnover markers (BTM) do not indicate fracture-risk. MicroRNAs (miRNAs) are promising new biomarkers for bone diseases, but the current understanding of the biological information contained in the variability of miRNAs is limited. Here, we investigated the association between serum-levels of 19 miRNA biomarkers of idiopathic osteoporosis to bone microstructure and bone histomorphometry based upon bone biopsies and µCT (9.3 μm) scans from 36 patients. Four miRNAs were found to be correlated to bone microarchitecture and seven miRNAs to dynamic histomorphometry (p < 0.05). Three miRNAs, namely, miR-29b-3p, miR-324-3p, and miR-550a-3p showed significant correlations to histomorphometric parameters of bone formation as well as microstructure parameters. miR-29b-3p and miR-324-p were found to be reduced in patients undergoing anti-resorptive therapy. This is the first study to report that serum levels of bone-related miRNAs might be surrogates of dynamic histomorphometry and potentially reveal changes in bone microstructure. Although these findings enhance the potential value of circulating miRNAs as bone biomarkers, further experimental studies are required to qualify the clinical utility of miRNAs to reflect dynamic changes in bone formation and microstructure.

A retrospective analysis of bone mineral status in patients requiring spinal surgery

Background

Impaired bone quality is associated with poor outcome of spinal surgery. The aim of the study was to assess the bone mineral status of patients scheduled to undergo spinal surgery and to report frequencies of bone mineral disorders.

Methods

We retrospectively analyzed the bone mineral status of 144 patients requiring spinal surgery including bone mineral density by dual-energy X-ray absorptiometry (DXA) as well as laboratory data with serum levels of 25-hydroxyvitamin D (25-OH-D), parathyroid hormone, calcium, bone specific alkaline phosphate, osteocalcin, and gastrin. High-resolution peripheral quantitative computed tomography (HR-pQCT) was additionally performed in a subgroup of 67 patients with T-Score below − 1.5 or history of vertebral fracture.

Results

Among 144 patients, 126 patients (87.5%) were older than 60 years. Mean age was 70.1 years. 42 patients (29.1%) had suffered from a vertebral compression fracture. 12 previously undiagnosed vertebral deformities were detected in 12 patients by vertebral fracture assessment (VFA). Osteoporosis was present in 39 patients (27.1%) and osteopenia in 63 patients (43.8%). Only 16 patients (11.1%) had received anti-osteoporotic therapy, while 54 patients (37.5%) had an indication for specific anti-osteoporotic therapy but had not received it yet. The majority of patients had inadequate vitamin D status (73.6%) and 34.7% of patients showed secondary hyperparathyroidism as a sign for a significant disturbed calcium homeostasis. In a subgroup of 67 patients, severe vertebral deformities were associated with stronger deficits in bone microarchitecture at the distal radius compared to the distal tibia.

Conclusions

This study shows that bone metabolism disorders are highly prevalent in elderly patients scheduled for spinal surgery. Vertebral deformities are associated with a predominant deterioration of bone microstructure at the distal radius. As impaired bone quality can compromise surgical outcome, we strongly recommend an evaluation of bone mineral status prior to operation and anti-osteoporotic therapy if necessary.

The Prevalence of Vertebral Fractures Is Associated With Reduced Hip Bone Density and Inferior Peripheral Appendicular Volumetric Bone Density and Structure in Older Women

Vertebral fractures (VFs) are among the most severe and prevalent osteoporotic fractures. Their association with bone microstructure have been investigated in several retrospective case-control studies with spine radiography for diagnosis of VF. The aim of this population-based cross-sectional study of 1027 women aged 75 to 80 years was to investigate if prevalent VF, identified by vertebral fracture assessment (VFA) by dual-energy X-ray absorptiometry (DXA), was associated with appendicular volumetric bone density, structure, and bone material strength index (BMSi), independently of hip areal bone mineral density (aBMD). aBMD was measured using DXA (Discovery; Hologic); BMSi with microindentation (Osteoprobe); and bone geometry, volumetric BMD, and microstructure with high-resolution peripheral quantitative computed tomography (HRpQCT) (XtremeCT; Scanco Medical AG). aBMD was lower (spine 3.2%, total hip [TH] 3.8%) at all sites in women with VF, but tibia BMSi did not differ significantly compared to women without VF. In multivariable adjusted logistic regression models, radius trabecular bone volume fraction and tibia cortical area (odds ratio [OR] 1.26; 95% confidence interval [CI], [1.06 to 1.49]; and OR 1.27 [95% CI, 1.08 to 1.49], respectively) were associated with VF prevalence, whereas BMSi and cortical porosity were not. The risk of having one, two, or more than two VFs was increased 1.27 (95% CI, 1.04 to 1.54), 1.83 (95% CI, 1.28 to 2.61), and 1.78 (95% CI, 1.03 to 3.09) times, respectively, for each SD decrease in TH aBMD. When including either cortical area, trabecular bone volume fraction or TBS in the model together with TH aBMD and covariates, only TH aBMD remained independently associated with presence of any VF. In conclusion, TH aBMD was consistently associated with prevalent VFA-verified VF, whereas neither trabecular bone volume fraction, cortical area, cortical porosity, nor BMSi were independently associated with VF in older women. © 2017 American Society for Bone and Mineral Research.

Characterization of trabecular bone microstructure in premenopausal women with distal radius fractures

Individual trabecular segmentation was utilized to identify differences in trabecular bone structure in premenopausal women with wrist fractures and non-fracture controls. Fracture subjects had reduced trabecular plate volume, number, thickness, and connectivity. Identifying altered trabecular microarchitecture in young women offers opportunities for counseling and lifestyle modifications to reduce fracture risk.

INTRODUCTION

Premenopausal women with distal radius fractures (DRF) have worse trabecular bone microarchitecture than non-fracture controls (CONT), yet the characteristics of their trabecular bone structure are unknown.

METHODS

Premenopausal women with DRF (n = 40) and CONT (n = 80) were recruited. Primary outcome variables included trabecular structure at the distal radius and tibia, assessed by volumetric decomposition of individual trabecular plates and rods from high-resolution peripheral quantitative CT images. Trabecular morphology included plate and rod number, volume, thickness, and connectivity. Areal bone mineral density (aBMD) of the femoral neck (FN aBMD), and ultradistal radius (UDR aBMD) were measured by DXA.

RESULTS

Trabecular morphology differed between DRF and CONT at the radius and tibia (OR per SD decline 1.58-2.7). At the radius, associations remained significant when adjusting for age and FN aBMD (ORs = 1.76-3.26) and age and UDR aBMD (ORs = 1.72-3.97). Plate volume fraction, number and axially aligned trabeculae remained associated with DRF after adjustment for trabecular density (ORs = 2.55-2.85). Area under the curve (AUC) for discriminating DRF was 0.74 for the proportion of axially aligned trabeculae, compared with 0.60 for FN aBMD, 0.65 for UDR aBMD, and 0.69 for trabecular density. Plate number, plate-plate junction, and axial bone volume fraction remained associated with DRF at the tibia (ORs = 2.14-2.77) after adjusting for age, FN aBMD, or UDR aBMD. AUC_P.P.Junc.D was 0.72 versus 0.61 for FNaBMD, 0.66 for UDRaBMD, and 0.70 for trabecular density.

CONCLUSION

Premenopausal women with DRF have lower trabecular plate volume, number, thickness, and connectivity than CONT. Identification of young women with altered microarchitecture offers opportunities for lifestyle modifications to reduce fracture risk.

Bone Phenotype Assessed by HRpQCT and Associations with Fracture Risk in the GLOW Study

The epidemiology and pathogenesis of fractures in postmenopausal women has previously been investigated in the Global Longitudinal study of Osteoporosis in Women (GLOW). To date, however, relationships between bone imaging outcomes and fracture have not been studied in this cohort. We examined relationships between high-resolution peripheral quantitative computed tomography (HRpQCT) parameters and fracture in the UK arm of GLOW, performing a cluster analysis to assess if our findings were similar to observations reported from older participants of the Hertfordshire Cohort Study (HCS), and extended the analysis to include tibial measurements. We recorded fracture events and performed HRpQCT of the distal radius and tibia and dual-energy X-ray absorptiometry (DXA) of the hip in 321 women, mean age 70.6 (SD 5.4) years, identifying four clusters at each site. We saw differing relationships at the radius and tibia. Two radial clusters (3 and 4) had a significantly lower hip areal bone mineral density (p < 0.001) compared to Cluster 1; only individuals in Cluster 4 had a significantly higher risk of fracture (p = 0.005). At the tibia, clusters 1, 3 and 4 had lower hip areal bone mineral density (p < 0.001) compared to Cluster 2; individuals in Cluster 3 had a significantly higher risk of fracture (p = 0.009). In GLOW our findings at the radius were very similar to those previously reported in the HCS, suggesting that combining variables derived from HRpQCT may give useful information regarding fracture risk in populations where this modality is available. Further data relating to tibial HRpQCT-phenotype and fractures are provided in this paper, and would benefit from validation in other studies. Differences observed may reflect age differences in the two cohorts.

Trabecular bone score (TBS) is associated with sub-clinical vertebral fractures in HIV-infected patients

Fragility fractures risk is increased among HIV infected patients. Bone microstructure alterations, in addition to bone mineral density (BMD) reduction, might be responsible for the increased risk. The aim of this study was to determine the prevalence of vertebral fractures (VFs) and their association with trabecular bone score (TBS), an indirect index of bone microstructure, in a cohort of HIV-infected subjects. One-hundred and forty-one HIV-infected patients (87% males, median age 43 years, 94% on stable antiretroviral therapy with undetectable viral load) underwent viro-immunological and bone metabolism biochemical screenings. Lumbar TBS and BMD at femoral neck, total hip, and lumbar spine, were measured with dual-energy X-ray absorptiometry (DXA). VFs were identified using the semiquantitative method and quantitative morphometric analysis from thoracic and lumbar spine X-ray images. VFs were observed in 19 patients (13.5%). BMD was below the expected range for age in 18 (12.8%) subjects. No significant differences were found stratifying VFs prevalence by BMD, whereas patients with lower TBS showed a higher prevalence of VFs (p = 0.03). In multivariate analysis, TBS was the only factor significantly associated to VFs (OR = 0.56; 95% CI = 0.33-0.96; p = 0.034), with increased fracture risk for lower TBS values. VFs are prevalent and associated with low TBS among HIV-positive patients, whereas no significant association was found with BMD.

Impaired bone strength estimates at the distal tibia and its determinants in adolescents with anorexia nervosa

BACKGROUND

Altered bone microarchitecture and higher marrow adipose tissue (MAT) may reduce bone strength. High resolution pQCT (HRpQCT) allows assessment of volumetric BMD (vBMD), and size and microarchitecture parameters of bone, while 1H-magnetic resonance spectroscopy (1H-MRS) allows MAT evaluation. We have reported impaired microarchitecture at the non-weight bearing radius in adolescents with anorexia nervosa (AN) and that these changes may precede aBMD deficits. Data are lacking regarding effects of AN on microarchitecture and strength at the weight-bearing tibia in adolescents and young adults, and the impact of changes in microarchitecture and MAT on strength estimates.

OBJECTIVE

To compare strength estimates at the distal tibia in adolescents/young adults with AN and controls in relation to vBMD, bone size and microarchitecture, and spine MAT.

DESIGN AND METHODS

This was a cross-sectional study of 47 adolescents/young adults with AN and 55 controls 14-24years old that assessed aBMD and body composition using DXA, and distal tibia vBMD, size, microarchitecture and strength estimates using HRpQCT, extended cortical analysis, individual trabecular segmentation, and finite element analysis. Lumbar spine MAT (1H-MRS) was assessed in a subset of 19 AN and 22 controls.

RESULTS

Areal BMD Z-scores were lower in AN than controls. At the tibia, AN had greater cortical porosity, lower total and cortical vBMD, cortical area and thickness, trabecular number, and strength estimates than controls. Within AN, strength estimates were positively associated with lean mass, aBMD, vBMD, bone size and microarchitectural parameters. MAT was higher in AN, and associated inversely with strength estimates.

CONCLUSIONS

Adolescents/young adults with AN have impaired microarchitecture at the weight-bearing tibia and higher spine MAT, associated with reduced bone strength.

Spontaneous mutation of Dock7 results in lower trabecular bone mass and impaired periosteal expansion in aged female Misty mice

Misty mice (m/m) have a loss of function mutation in Dock7 gene, a guanine nucleotide exchange factor, resulting in low bone mineral density, uncoupled bone remodeling and reduced bone formation. Dock7 has been identified as a modulator of osteoblast number and in vitro osteogenic differentiation in calvarial osteoblast culture. In addition, m/m exhibit reduced preformed brown adipose tissue innervation and temperature as well as compensatory increase in beige adipocyte markers. While the low bone mineral density phenotype is in part due to higher sympathetic nervous system (SNS) drive in young mice, it is unclear what effect aging would have in mice homozygous for the mutation in the Dock7 gene. We hypothesized that age-related trabecular bone loss and periosteal envelope expansion would be altered in m/m. To test this hypothesis, we comprehensively characterized the skeletal phenotype of m/m at 16, 32, 52, and 78wks of age. When compared to age-matched wild-type control mice (+/+), m/m had lower areal bone mineral density (aBMD) and areal bone mineral content (aBMC). Similarly, both femoral and vertebral BV/TV, Tb.N, and Conn.D were decreased in m/m while there was also an increase in Tb.Sp. As low bone mineral density and decreased trabecular bone were already present at 16wks of age in m/m and persisted throughout life, changes in age-related trabecular bone loss were not observed highlighting the role of Dock7 in controlling trabecular bone acquisition or bone loss prior to 16wks of age. Cortical thickness was also lower in the m/m across all ages. Periosteal and endosteal circumferences were higher in m/m compared to +/+ at 16wks. However, endosteal and periosteal expansion were attenuated in m/m, resulting in m/m having lower periosteal and endosteal circumferences by 78wks of age compared to +/+, highlighting the critical role of Dock7 in appositional bone expansion. Histomorphometry revealed that osteoblasts were nearly undetectable in m/m and marrow adipocytes were elevated 3.5 fold over +/+ (p=0.014). Consistent with reduced bone formation, osteoblast gene expression of Alp, Col1a1, Runx-2, Sp7, and Bglap was significantly decreased in m/m whole bone. Furthermore, markers of osteoclasts were either unchanged or suppressed. Bone marrow stromal cell migration and motility were inhibited in culture and changes in senescence markers suggest that osteoblast function may also be inhibited with loss of Dock7 expression in m/m. Finally, increased Oil Red O staining in m/m ear mesenchymal stem cells during adipogenesis highlights a potential shift of cells from the osteogenic to adipogenic lineages. In summary, loss of Dock7 in the aging m/m resulted in an impairment of periosteal and endocortical envelope expansion, but did not alter age-related trabecular bone loss. These studies establish Dock7 as a critical regulator of both cortical and trabecular bone mass, and demonstrate for the first time a novel role of Dock7 in modulating compensatory changes in the periosteum with aging.

Bone Strength Estimated by Micro-Finite Element Analysis (µFEA) Is Heritable and Shares Genetic Predisposition With Areal BMD: The Framingham Study

Genetic factors contribute to the risk of bone fractures, partly because of effects on bone strength. High-resolution peripheral quantitative computed tomography (HR-pQCT) estimates bone strength using micro-finite element analysis (µFEA). The goal of this study was to investigate if the bone failure load estimated by HR-pQCT-based µFEA is heritable and to what extent it shares genetic regulation with areal bone mineral density (aBMD). Bone microarchitecture was measured by HR-pQCT at the ultradistal tibia and ultradistal radius in adults from the Framingham Heart Study (n = 1087, mean age 72 years; 57% women). Radial and tibial failure load in compression were estimated by µFEA. Femoral neck (FN) and ultradistal forearm (UD) aBMD were measured by dual-energy X-ray absorptiometry (DXA). Heritability (h2 ) of failure load and aBMD and genetic correlations between them was estimated adjusting for covariates (age and sex). Failure load values at the non-weight-bearing ultradistal radius and at the weight-bearing ultradistal tibia were highly correlated (r = 0.906; p < 0.001). Estimates of h2 adjusted for covariates were 0.522 for the radius and 0.497 for the tibia. Additional adjustment for height did not impact on the h2 results, but adjustment for aBMD at the UD and FN somewhat decreased h2 point estimates: 0.222 and 0.380 for radius and tibia, respectively. In bivariate analysis, there was a high phenotypic and genetic correlation between covariate-adjusted failure load at the radius and UD aBMD (ρP  = 0.826, ρG  = 0.954, respectively), whereas environmental correlations were lower (ρE  = 0.696), all highly significant (p < 0.001). Similar correlations were observed between tibial failure load and femoral neck aBMD (ρP  = 0.577, ρG  = 0.703, both p < 0.001; ρE  = 0.432, p < 0.05). These data from adult members of families from a population-based cohort suggest that bone strength of distal extremities estimated by micro-finite element analysis is heritable and shares some genetic composition with areal BMD, regardless of the skeletal site. © 2017 American Society for Bone and Mineral Research.

Changes in cortical microarchitecture are independent of areal bone mineral density in patients with fragility fractures

Dual-energy X-ray absorptiometry (DXA) and high-resolution peripheral quantitative computed tomography (HR-pQCT) are commonly used to assess the areal bone mineral density (aBMD) and peripheral microstructure, respectively. While DXA is the standard to diagnose osteoporosis, HR-pQCT provides information about the cortical and trabecular architecture. Many fragility fractures occur in patients who do not meet the osteoporosis criterion (i.e., T-score≤-2.5). We hypothesize that patients with T-score above -2.5 and fragility fracture may have abnormal bone microarchitecture. Therefore, in this retrospective clinical study, HR-pQCT data obtained from patients with fragility fractures and T-scores≥-2.5 (n=71) were compared to corresponding data from patients with fragility fractures and T-scores≤-3.5 (n=56). Types of secondary osteoporosis were excluded from the study. To verify the dependency of alterations in bone microarchitecture and T-score, the association between HR-pQCT values and aBMD as reflected by the T-score at both proximal femora, was assessed. At the distal tibia, cortical thickness was lower (p<0.001), cortical porosity was similar (p=0.61), trabecular number was higher (p<0.001), and bone volume fraction (BV/TV) was higher (p<0.001) in patients with T-scores≥-2.5 than in patients with T-scores≤-3.5. Trabecular number and BV/TV correlated with T-score (r=0.68, p<0.001; r=0.61, p<0.001), whereas the cortical values did not. Our results thus demonstrate the importance of bone structure, as assessed by HR-pQCT, in addition to the standard DXA T-score in the diagnosis of osteoporosis.

A model of fracture risk used to examine the link between bone mineral density and the impact of different therapeutic mechanisms on fracture outcomes in patients with osteoporosis

A hazard model of fracture was developed using individual patient data (IPD) from the NHANES (2005-2008) database and summary-level data from an aggregate dataset (AD). The AD was built by performing a comprehensive and systematic literature search of clinical studies published from 1995 to 2015, recording fracture rate and bone mineral density (BMD) for both treatment and placebo arms. The search resulted in a metadata set comprised of 21 studies investigating the effects of various bisphosphonates, teriparatide, denosumab, and raloxifene in 65,254 patients over a cumulative 56.75 years of study. The IPD was used to augment an AD in a model-based meta-analysis (MBMA) hierarchical modeling approach. The resulting model predicts the probability of fracture events in patients with osteoporosis. The object of model building using this approach was to promote understanding of the impact of therapeutic drug effects on the probability of fracture together with, or independent of their effects on BMD. Candidate models were evaluated by deviance information criteria and posterior predictive check. The model with covariates for lumbar spine BMD with interaction with a drug effect on BMD, and patient body mass index, years post-menopause, fracture measure method (clinical or radiological) and an additional drug effect outperformed those models without interaction and without additional drug effects. The model quantitatively supports the widely held notion that changes in bone microarchitecture, which cannot be measured by areal BMD elicited by therapy contribute in a significant way to a reduction in fracture. Furthermore, this model can be used to simulate fracture risk in a clinical cohort similar to those contained in the MBMA.

Correlative Analysis of Vertebral Trabecular Bone Microarchitecture and Mechanical Properties: A Combined Ultra-high Field (7 Tesla) MRI and Biomechanical Investigation

STUDY DESIGN

High-resolution imaging and biomechanical investigation of ex-vivo vertebrae.

OBJECTIVE

The aim of this study was to assess bone microarchitecture of cadaveric vertebrae using ultra-high field (UHF) 7 Tesla magnetic resonance imaging (MRI) and to determine whether the corresponding microarchitecture parameters were related to bone mineral density (BMD) and bone strength assessed by dual-energy x-ray absorptiometry (DXA) and mechanical compression tests.

SUMMARY OF BACKGROUND DATA

Limitations of DXA for the assessment of bone fragility and osteoporosis have been recognized and criteria of microarchitecture alteration have been included in the definition of osteoporosis. Although vertebral fracture is the most common osteoporotic fracture, no study has assessed directly vertebral trabecular bone microarchitecture.

METHODS

BMD of 24 vertebrae (L2, L3, L4) from eight cadavers was investigated using DXA. The bone volume fraction (BVF), trabecular thickness (Tb.Th), and trabecular spacing (Tb.Sp) of each vertebra were quantified using UHF MRI. Measurements were performed by two operators to characterize the inter-rater reliability. The whole set of specimens underwent mechanical compression tests to failure and the corresponding failure stress was calculated.

RESULTS

The inter-rater reliability for bone microarchitecture parameters was good with intraclass correlation coefficients ranging from 0.82 to 0.94. Failure load and stress were significantly correlated with BVF, Tb.Sp, and BMD (P < 0.05). Tb.Th was only correlated with the failure stress (P < 0.05). Multiple regression analysis demonstrated that the combination of BVF and BMD improved the prediction of the failure stress from an adjusted R = 0.384 for BMD alone to an adjusted R = 0.414.

CONCLUSION

We demonstrated for the first time that the vertebral bone microarchitecture assessed with UHF MRI was significantly correlated with biomechanical parameters. Our data suggest that the multimodal assessment of BMD and trabecular bone microarchitecture with UHF MRI provides additional information on the risk of vertebral bone fracture and might be of interest for the future investigation of selected osteoporotic patients.

LEVEL OF EVIDENCE

N /A.

Clinical, radiographic and biochemical characteristics of adult hypophosphatasia

In this study, we report on clinical, radiographic and biochemical characteristics of 38 patients with adult hypophosphatasia. High-resolution peripheral quantitative computed tomography showed alterations of bone microstructure in a subgroup of 14 patients. Pyridoxal-5-phosphate levels correlated with the occurrence of fractures and the number of symptoms.

INTRODUCTION

Hypophosphatasia (HPP) is a rare disorder with a wide range of clinical manifestations. A reduced enzymatic activity of alkaline phosphatase (ALP) is the key marker of the disease, causing an accumulation of ALP substrates such as pyridoxal-5-phosphate (PLP). The purpose of this retrospective study was to further characterize adult onset HPP.

METHODS

We assessed clinical, radiographic and laboratory characteristics of 38 adult patients with HPP. Diagnosis of HPP was established by the combination of low-serum ALP, raised PLP levels and typical symptoms and was genetically confirmed in 32 patients. Dual-energy X-ray absorptiometry (DXA) and laboratory data were available in most patients. High-resolution peripheral quantitative computed tomography (HR-pQCT) was performed in 14 patients.

RESULTS

Clinical characteristics included a wide spectrum of symptoms. A history of fracture was present in 15 patients (39%). Twenty-one patients (55%) complained about recurring headaches, 23 patients (61%) had recurring muscle pain, 4 patients (11%) suffered from severe muscle weakness and 18 patients (47%) showed dental abnormalities. Z-scores assessed by DXA were only slightly reduced in most adult HPP patients. HR-pQCT of 14 patients showed microstructural changes of trabecular and cortical bone compared to reference values of healthy subjects. The occurrence of fractures and multiple symptoms (>2 typical HPP symptoms) were associated with significantly elevated levels of PLP.

CONCLUSION

Adult HPP presents with a wide range of clinical symptoms and is not associated with low bone mass in general. PLP seems to be a good marker for disease severity in adult patients as its level is correlated with the occurrence of fractures and number of symptoms.

Eating disorders and bone metabolism in women

PURPOSE OF REVIEW

Eating Disorders are psychiatric disorders associated with a high risk for low bone mineral density (BMD) and fractures. Low BMD is a consequence of undernutrition, changes in body composition, and hormonal alterations. This review summarizes recent findings regarding novel strategies for assessing bone outcomes in patients with eating disorders, factors contributing to altered bone metabolism, and possible therapeutic strategies.

RECENT FINDINGS

Emerging research in this field suggests that not only anorexia nervosa, but also bulimia nervosa results in lower BMD compared to controls. To date studies of bone structure, and all randomized controlled trials examining the impact of various therapies on bone outcomes in anorexia nervosa, have focused on adolescent girls and women. We discuss the impact of anorexia nervosa on bone structure, and associations of resting energy expenditure, marrow adipose tissue (including the ratio of saturated to unsaturated fat), and cold activated brown adipose tissue with BMD and bone structure. Promising strategies for treatment include physiological estrogen replacement (rather than oral contraceptives) in adolescent girls with anorexia nervosa, and bisphosphonates, as well as teriparatide, in adult women with anorexia nervosa.

SUMMARY

Recent data on (i) BMD and bone structure in adolescent girls and women with eating disorders, (ii) factors that contribute to altered bone metabolism, and (iii) randomized controlled trials reporting positive effects of physiologic estrogen replacement, bisphosphonates and teriparatide on bone health, provide us with a greater understanding of the impact of eating disorders on bone and novel management strategies.

Cortical microstructure compensates for smaller bone size in young Caribbean Hispanic versus non-Hispanic white men

Hispanic men have smaller bone size but thicker and denser cortices compared to white men, leading to similar mechanical competence.

INTRODUCTION

The purpose of this study was to assess differences in vBMD and microarchitecture in young Caribbean Hispanic (n = 30) and non-Hispanic Caucasian (n = 30) men.

METHODS

We measured areal bone mineral density (aBMD) at the spine, total hip (TH), femoral neck (FN), and forearm by dual-energy X-ray absorptiometry (DXA) and bone geometry, mass, microarchitecture, and mechanical competence by high-resolution peripheral quantitative computed tomography (HRpQCT), individual trabecula segmentation (ITS), and finite element analysis (FEA).

RESULTS

Hispanic men were slightly older, shorter, and heavier and had higher BMI compared with white men. aBMD, measured by DXA, did not differ at the spine, TH, or forearm before or after adjustment for age, height, weight, and the interaction of height and weight. At the FN, marginally significant higher BMD in Hispanics prior to adjustment was attenuated and no longer differed after adjustment for covariates. Adjusted HRpQCT indices indicated smaller total and trabecular area at the radius but greater total volumetric density and cortical thickness in Hispanic versus white men. The adjusted difference in cortical density at the radius was of borderline significance. Trabecular and ITS microstructure tended not to differ at the radius. At the tibia, results were similar. Bone size tended to be smaller and covariate-adjusted cortical density and cortical thickness were greater in Hispanic versus white men. Additionally, cortical porosity was lower at the tibia in Hispanic compared to white men. Stiffness and failure load did not differ at either skeletal site by ethnicity.

CONCLUSION

In conclusion, greater cortical thickness and density as well as lower cortical porosity tend to compensate for smaller bone size in Hispanic men, leading to similar mechanical competence compared with white men.

Bone Microarchitecture Assessed by HR-pQCT as Predictor of Fracture Risk in Postmenopausal Women: The OFELY Study

Several cross-sectional studies have shown that impairment of bone microarchitecture contributes to skeletal fragility. The aim of this study was to prospectively investigate the prediction of fracture (Fx) by bone microarchitecture assessed by high-resolution peripheral computed tomography (HR- pQCT) in postmenopausal women. We measured microarchitecture at the distal radius and tibia with HR-pQCT in the OFELY study, in addition to areal BMD with dual-energy X-ray absorptiometry (DXA) in 589 women, mean ± SD age 68 ± 9 years. During a median [IQ] 9.4 [1.0] years of follow-up, 135 women sustained an incident fragility Fx, including 81 women with a major osteoporotic Fx (MOP Fx). After adjustment for age, women who sustained Fx had significantly lower total and trabecular volumetric densities (vBMD) at both sites, cortical parameters (area and thickness at the radius, vBMD at the tibia), trabecular number (Tb.N), connectivity density (Conn.D), stiffness, and estimated failure load at both sites, compared with control women. After adjustment for age, current smoking, falls, prior Fx, use of osteoporosis-related drugs, and total hip BMD, each quartile decrease of several baseline values of bone microarchitecture at the radius was associated with significant change of the risk of Fx (HR of 1.39 for Tb.BMD [p = 0.001], 1.32 for Tb.N [p = 0.01], 0.76 for Tb.Sp.SD [p = 0.01], 1.49 [p = 0.01] for Conn.D, and 1.27 for stiffness [p = 0.02]). At the tibia, the association remained significant for stiffness and failure load in the multivariate model for all fragility Fx and for Tt.BMD, stiffness, and failure load for MOP Fx. We conclude that impairment of bone microarchitecture-essentially in the trabecular compartment of the radius-predict the occurrence of incident fracture in postmenopausal women. This assessment may play an important role in identifying women at high risk of fracture who could not be adequately detected by BMD measurement alone, to benefit from a therapeutic intervention. © 2017 American Society for Bone and Mineral Research.