Non-pharmacologic approaches to preserve or increase bone mineral density (BMD) include whole body vibration (WBV), but its efficacy in elderly persons is not clear. Therefore, we conducted the Vibration to Improve Bone in Elderly Subjects (“VIBES”) trial, a randomized, placebo-controlled trial of 10 minutes of daily WBV (0.3g at 37 Hz) in seniors recruited from 16 independent living communities. The primary outcomes were volumetric BMD of the hip and spine measured by quantitative computed tomography (QCT), and biochemical markers of bone turnover. We randomized 174 men and women (89 active, 85 placebo) with T-scores −1 to −2.5 who were not taking bone active drugs and had no diseases affecting the skeleton (mean age 82 ± 7 yrs, range 65–102). Participants received daily calcium (1,000 mg) and vitamin D (800 IU). Study platforms were activated using radio frequency ID cards providing electronic adherence monitoring; placebo platforms resembled the active platforms. In total, 61% of participants in the active arm and 73% in the placebo arm completed 24 months. The primary outcomes, median percent changes (inter-quartile range; IQR) in total volumetric femoral trabecular BMD (active group (2.2% [−0.8%, 5.2%]) vs. placebo 0.4% [−4.8%, 5.0%]), and in median mid-vertebral trabecular BMD of L1 and L2 (active group (5.3% [−6.9%, 13.3%]) vs. placebo (2.4% [−4.4%, 11.1%]), did not differ between groups (all p-values > 0.1). Changes in biochemical markers of bone turnover (P1NP and sCTX) also were not different between groups (p=0.19 and p=0.97, respectively). In conclusion, this placebo-controlled randomized trial of daily WBV in older adults did not demonstrate evidence of significant beneficial effects on volumetric BMD or bone biomarkers; however, the high variability in vBMD changes limited our power to detect small treatment effects. The beneficial effects of WBV observed in previous studies of younger women may not occur to the same extent in elderly individuals.
Studies of vitamin D pathway genetic variants in relation to cancer risk have been inconsistent. We examined associations between vitamin D-related genetic polymorphisms, plasma 25-hydroxyvitamin D [25(OH)D], and breast cancer risk.
In a population-based case-control study of 967 incident breast cancer cases and 993 controls, we genotyped 25 polymorphisms encoding the vitamin D receptor (VDR) gene, 1α-hydroxylase (CYP27B1), 24-hydroxylase (CYP24A1), and vitamin D binding protein (GC) and measured plasma 25(OH)D. We used multivariable logistic regression to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CI).
Among CYP24A1 polymorphisms, rs6068816 was associated with a 72% reduction in breast cancer risk (TT vs. CC, OR: 0.28, 95%CI: 0.10–0.76; ptrend=0.01), but for rs13038432, the 46% decrease included the null value (GG vs. AA, OR: 0.54, 95%CI: 0.17–1.67; ptrend=0.03). Increased risk that included the null value was noted for CYP24A1 rs3787557 (CC vs. TT, OR: 1.34, 95% CI: 0.92–1.89). The VDR polymorphism, TaqI (rs731236), was associated with a 26% risk reduction (TT vs. CC, OR: 0.74, 95%CI: 0.56–0.98; ptrend=0.01). For other polymorphisms, ORs were weak and included the null value. The inverse association for plasma 25(OH)D with breast cancer was more pronounced (OR: 0.43, 95%CI: 0.27–0.68) among women with the common allele for CYP24A, rs927650 (p for interaction on a multiplicative scale=0.01).
Breast cancer risk may be associated with specific vitamin D-related polymorphisms, particularly CYP24A1. Genetic variation in the vitamin D pathway should be considered when designing potential intervention strategies with vitamin D supplementation.
breast cancer; vitamin D related gene polymorphisms; plasma 25-hydroxyvitamin D; CYP24A1
The intensity of bone remodeling is a critical determinant of the decay of cortical and trabecular microstructure after menopause. Denosumab suppresses remodeling more than alendronate, leading to greater gains in areal bone mineral density (aBMD). These greater gains may reflect differing effects of each drug on bone microarchitecture and strength. In a phase 2 double-blind pilot study, 247 postmenopausal women were randomized to denosumab (60mg subcutaneous 6 monthly), alendronate (70mg oral weekly), or placebo for 12 months. All received daily calcium and vitamin D. Morphologic changes were assessed using high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal radius and distal tibia and QCT at the distal radius. Denosumab decreased serum C-telopeptide more rapidly and markedly than alendronate. In the placebo arm, total, cortical, and trabecular BMD and cortical thickness decreased (−2.1% to −0.8%) at the distal radius after 12 months. Alendronate prevented the decline (−0.6% to 2.4%, p = .051 to < .001 versus placebo), whereas denosumab prevented the decline or improved these variables (0.3% to 3.4%, p < .001 versus placebo). Changes in total and cortical BMD were greater with denosumab than with alendronate (p ≤ .024). Similar changes in these parameters were observed at the tibia. The polar moment of inertia also increased more in the denosumab than alendronate or placebo groups (p < .001). Adverse events did not differ by group. These data suggest that structural decay owing to bone remodeling and progression of bone fragility may be prevented more effectively with denosumab.
DENOSUMAB; ALENDRONATE; HR-PQCT; VOLUMETRIC BONE MINERAL DENSITY; CORTICAL THICKNESS
The majority of fragility fractures occur in women with osteopenia rather than osteoporosis by dual energy x-ray absorptiometry (DXA). However, it is difficult to identify which women with osteopenia are at greatest risk. We performed this study to determine whether osteopenic women with and without fracture had differences in trabecular morphology and biomechanical properties of bone. We hypothesized that women with fractures would have fewer trabecular plates, less trabecular connectivity and lower stiffness. We enrolled 117 postmenopausal women with osteopenia by DXA (mean age 66 years; 58 with fragility fractures and 59 non-fractured controls). All had areal bone mineral density by DXA. Trabecular and cortical volumetric BMD (vBMD), trabecular microarchitecture, and cortical porosity were measured by high resolution peripheral computed tomography (HR-pQCT) of the distal radius and tibia. HR-pQCT scans were subjected to finite element analysis to estimate whole bone stiffness and individual trabecula segmentation (ITS) to evaluate trabecular type (as plate or rod), orientation and connectivity. Groups had similar age, race, BMI, and mean T-scores. Fracture subjects had lower cortical and trabecular vBMD, thinner cortices, and thinner more widely separated trabeculae. By ITS, fracture subjects had fewer trabecular plates, less axially aligned trabeculae and less trabecular connectivity. Whole bone stiffness was lower in women with fractures. Cortical porosity did not differ. Differences in cortical bone were found at both sites, whereas trabecular differences were more pronounced at the radius. In summary, postmenopausal women with osteopenia and fractures had lower cortical and trabecular vBMD, thinner, more widely separated and rod-like trabecular structure, less trabecular connectivity and lower whole bone stiffness compared to controls, despite similar aBMD by DXA. Our results suggest that in addition to trabecular and cortical bone loss, changes in plate and rod structure may be important mechanisms of fracture in postmenopausal women with osteopenia.
Osteoporosis; fracture; microarchitecture; bone quality; menopause
Interpretation of bone mineral density (BMD) results in premenopausal women is particularly challenging, because the relationship between BMD and fracture risk is not the same as for postmenopausal women. Z scores rather than T scores should be used to define “low BMD” in premenopausal women. The finding of low BMD in a premenopausal woman should prompt an evaluation for secondary causes of bone loss. If a secondary cause is found, management should focus on treatment of this condition. In some cases in which the secondary cause cannot be addressed, such as glucocorticoid therapy or cancer chemotherapy, treatment with a bone-active agent to prevent bone loss should be considered. In women with no fractures and no known secondary cause, low BMD may not signify compromised bone strength. BMD is likely to remain stable in these women, and pharmacologic therapy is rarely justified. Assessment of markers of bone turnover and follow-up bone density measurements can help to identify those with an ongoing process of bone loss that may indicate a higher risk for fracture, and possible need for pharmacologic intervention.
Interpretation of bone mineral density (BMD) results in premenopausal women is particularly challenging, since the relationship between BMD and fracture risk is not the same as for postmenopausal women. In most cases, Z scores rather than T scores should be used to define “low BMD” in premenopausal women. The finding of low BMD in a premenopausal woman should prompt thorough evaluation for secondary causes of bone loss. If a secondary cause is found, management should focus on treatment of this condition. In a few cases where the secondary cause cannot be eliminated, treatment with a bone active agent to prevent bone loss should be considered. In women with no fractures and no known secondary cause, low BMD is associated with microarchitectural defects similar to young women with fractures; however, no longitudinal data are available to allow use of BMD to predict fracture risk. BMD is likely to be stable in these women with isolated low BMD, and pharmacologic therapy is rarely necessary. Assessment of markers of bone turnover and follow-up bone density measurements can help to identify those with an ongoing process of bone loss that may indicate a higher risk for fracture, and possible need for pharmacologic intervention.
Premenopausal Osteoporosis; Bisphosphonates; Teriparatide
Hispanic Americans of Caribbean origin are a fast-growing subset of the US population, but there are no studies on bone density, microstructure and biomechanical integrity in this minority group. In this study, we aimed to compare Caucasian and Caribbean Hispanic postmenopausal American women with respect to these characteristics. Thirty-three Caribbean Hispanics were age-matched to thirty-three Caucasian postmenopausal women. At the lumbar spine, the Hispanic women had significantly lower areal bone mineral density (aBMD). At the radius by high-resolution peripheral quantitative computed tomography (HR-pQCT), there were minimal differences between Hispanic and Caucasian women. At the tibia, Hispanic women had lower trabecular volumetric bone density and trabecular number, and higher trabecular separation. Individual trabecula segmentation (ITS) analyses indicated that at the tibia, Hispanic women not only had significantly lower bone volume fraction, but also had significantly lower rod bone volume fraction, plate trabecular number, rod trabecular number and lower plate–plate, plate–rod and rod–rod junction densities compared to Caucasian women. The differences in bone quantity and quality contributed to lower whole bone stiffness at the radius, and both whole bone and trabecular bone stiffness at the tibia in Hispanic women. In conclusion, Hispanic women had poorer bone mechanical and microarchitectural properties than Caucasian women, especially at the load-bearing distal tibia.
Susceptibility to fracture is increased across the spectrum of chronic kidney disease (CKD). Moreover, fracture in patients with end-stage kidney disease (ESKD) results in significant excess mortality. The incidence and prevalence of CKD and ESKD are predicted to increase markedly over the coming decades in conjunction with the aging of the population. Given the high prevalence of both osteoporosis and CKD in older adults, it is of the utmost public health relevance to be able to assess fracture risk in this population. Dual-energy X-ray absorptiometry (DXA), which provides an areal measurement of bone mineral density (aBMD), is the clinical standard to predict fracture in individuals with postmenopausal or age-related osteoporosis. Unfortunately, DXA does not discriminate fracture status in patients with ESKD. This may be, in part, because excess parathyroid hormone (PTH) secretion may accompany declining kidney function. Chronic exposure to high PTH levels preferentially causes cortical bone loss, which may be partially offset by periosteal expansion. DXA can neither reliably detect changes in bone volume nor distinguish between trabecular and cortical bone. In addition, DXA measurements may be low, normal, or high in each of the major forms of renal osteodystrophy (ROD). Moreover, postmenopausal or age-related osteoporosis may also affect patients with CKD and ESKD. Currently, transiliac crest bone biopsy is the gold standard to diagnose ROD and osteoporosis in patients with significant kidney dysfunction. However, bone biopsy is an invasive procedure that requires time-consuming analyses. Therefore, there is great interest in developing non-invasive high-resolution imaging techniques that can improve fracture risk prediction for patients with CKD. In this paper, we review studies of fracture risk in the setting of ESKD and CKD, the pathophysiology of increased fracture risk in patients with kidney dysfunction, the utility of various imaging modalities in predicting fracture across the spectrum of CKD, and studies evaluating the use of bisphosphonates in patients with CKD.
chronic kidney disease; renal osteodystrophy; fracture; bone imaging
This article will discuss the diagnosis of osteoporosis in premenopausal women and the evaluation and management of those with low-trauma fractures and/or low bone mineral density. As secondary causes (glucocorticoid excess, anorexia nervosa, premenopausal estrogen deficiency, and celiac disease) are commonly the underlying cause of osteoporosis in this population, treatment of the underlying condition should be the focus of management. Additional management options, generally reserved for those with major or multiple fractures and/or ongoing bone loss, will also be described.
premenopausal women; osteoporosis; bone mineral density; pregnancy-associated osteoporosis; lactation- associated osteoporosis; idiopathic osteoporosis
Osteoporosis, a disease characterized by loss of bone mass and structural deterioration, is currently diagnosed by dual-energy x-ray absorptiometry (DXA). However, DXA does not provide information about bone microstructure, which is a key determinant of bone strength. Recent advances in imaging permit the assessment of bone microstructure in vivo using high-resolution peripheral quantitative computed tomography (HR-pQCT). From these data, novel image processing techniques can be applied to characterize bone quality and strength. To date, most HR-pQCT studies are cross-sectional comparing subjects with and without fracture. These studies have shown that HR-pQCT is capable of discriminating fracture status independent of DXA. Recent longitudinal studies present new challenges in terms of analyzing the same region of interest and multisite calibrations. Careful application of analysis techniques and educated clinical interpretation of HR-pQCT results have improved our understanding of various bone-related diseases and will no doubt continue to do so in the future.
High-resolution peripheral quantitative computed tomography; HR-pQCT; Bone microarchitecture; Osteoporosis; Fragility fractures; Finite element analysis; Clinical imaging
Antiepileptic drugs, particularly cytochrome P450 enzyme inducers, are associated with disorders of bone metabolism. We studied premenopausal women with epilepsy receiving antiepileptic drug monotherapy (phenytoin, carbamazepine, valproate, and lamotrigine). Subjects completed exercise and nutrition questionnaires and bone mineral density studies. Serum was analyzed for indices of bone metabolism including calcium, 25-hydroxyvitamin D, parathyroid hormone, insulin growth factor I, insulin binding protein III, and bone formation markers, bone-specific alkaline phosphatase, and osteocalcin. Urine was analyzed for cross-linked N-telopeptide of type I collagen, a bone resorption marker. Calcium concentrations were significantly less in subjects receiving carbamazepine, phenytoin, and valproate than in those receiving lamotrigine (p = 0.008). Insulin growth factor-I was significantly reduced in subjects receiving phenytoin compared with those receiving lamotrigine (p = 0.017). Subjects receiving phenytoin had significantly greater levels of bone-specific alkaline phosphatase (p = 0.007). Our results demonstrate that phenytoin is associated with changes in bone metabolism and increased bone turnover. The lower calcium concentrations in subjects taking carbamazepine or valproate compared with those taking other antiepileptic drugs suggest that these antiepileptic drugs may have long-term effects. Subjects receiving lamotrigine had no significant reductions in calcium or increases in markers of bone turnover, suggesting this agent is less likely to have long-term adverse effects on bone.
While high-resolution peripheral quantitative computed tomography (HR-pQCT) has advanced clinical assessment of trabecular bone microstructure, nonlinear microstructural finite element (μFE) prediction of yield strength by HR-pQCT voxel model is impractical for clinical use due to its prohibitively high computational costs. The goal of this study was to develop an efficient HR-pQCT-based plate and rod (PR) modeling technique to fill the unmet clinical need for fast bone strength estimation. By using individual trabecula segmentation (ITS) technique to segment the trabecular structure into individual plates and rods, a patient-specific PR model was implemented by modeling each trabecular plate with multiple shell elements and each rod with a beam element. To validate this modeling technique, predictions by HR-pQCT PR model were compared with those of the registered high resolution μCT voxel model of 19 trabecular sub-volumes from human cadaveric tibiae samples. Both Young’s modulus and yield strength of HR-pQCT PR models strongly correlated with those of μCT voxel models (r2=0.91 and 0.86). Notably, the HR-pQCT PR models achieved major reductions in element number (>40-fold) and CPU time (>1,200-fold). Then, we applied PR model μFE analysis to HR-pQCT images of 60 postmenopausal women with (n=30) and without (n=30) a history of vertebral fracture. HR-pQCT PR model revealed significantly lower Young’s modulus and yield strength at the radius and tibia in fracture subjects compared to controls. Moreover, these mechanical measurements remained significantly lower in fracture subjects at both sites after adjustment for aBMD T-score at the ultradistal radius or total hip. In conclusion, we validated a novel HR-pQCT PR model of human trabecular bone against μCT voxel models and demonstrated its ability to discriminate vertebral fracture status in postmenopausal women. This accurate nonlinear μFE prediction of HR-pQCT PR model, which requires only seconds of desktop computer time, has tremendous promise for clinical assessment of bone strength.
trabecular microarchitecture; trabecular plate and rod; individual trabeculae segmentation; high-resolution peripheral quantitative computed tomography; finite element model
To assess the effects of HIV infection and antiretroviral therapy (ART) on trabecular and cortical microarchitecture in postmenopausal minority women.
A subgroup of 106 (46 HIV-infected, 60 uninfected) postmenopausal Hispanic and African American women from an established cohort had areal bone mineral density (aBMD) measured by dual-energy x-ray absorptiometry, and trabecular and cortical volumetric BMD (vBMD) and microarchitecture measured by high-resolution peripheral quantitative computed tomography (HRpQCT) at the radius and tibia.
HIV-infected women were slightly younger (58±1 versus 61±1 yrs, p=0.08), and had lower body mass index (BMI, 28±1 versus 32±1 kg/m2, p<0.01). BMI-adjusted aBMD Z scores were lower in HIV-infected women at the lumbar spine, total hip and ultradistal radius. Serum N-telopeptide and C-telopeptide levels were also higher in HIV-infected women. Trabecular and cortical vBMD were similar at the radius, but cortical area (105.5±2.4 versus 120.6±2.0mm2, p<0.01) and thickness (956±33 versus 1075±28 m, p<0.01) at the tibia were approximately 11–12% lower in HIV-infected women. Differences remained significant after adjusting for age, BMI and race/ethnicity. In contrast, cortical porosity was similar in both groups.
Although HIV-infected postmenopausal women had lower aBMD at the spine, total hip and ultradistal radius and higher levels of bone resorption markers, the only differences detected by HRpQCT were lower cortical thickness and area at the tibia.
HIV; microarchitecture; cortical structure; osteoporosis; postmenopausal women
HIV infection and antiretroviral therapy (ART) early in life may interfere with acquisition of peak bone mass, thereby increasing fracture risk in adulthood.
We conducted a cross-sectional study of dual-energy X-ray absorptiometry (DXA) and high-resolution peripheral quantitative computed tomography (HR-pQCT) in 30 HIV-infected African–American or Hispanic Tanner stage 5 men aged 20–25 on ART (15 perinatally infected and 15 infected during adolescence) and 15 HIV-uninfected controls.
HIV-infected men were similar in age and BMI, but were more likely to be African–American (P = 0.01) than uninfected men. DXA-derived areal bone mineral density (aBMD) Z-scores were 0.4–1.2 lower in HIV-infected men at the spine, hip, and radius (all P < 0.05). At the radius and tibia, total and trabecular volumetric BMD (vBMD), and cortical and trabecular thickness were between 6 and 19% lower in HIV-infected than uninfected men (P <0.05). HIV-infected men had dramatic deficiencies in plate-related parameters by individual trabeculae segmentation (ITS) analyses and 14–17% lower bone stiffness by finite element analysis revealed. Differences in most HR-pQCT parameters remained significant after adjustment for race/ethnicity. No DXA or HR-pQCT parameters differed between men infected perinatally or during adolescence.
At an age by which young men have typically acquired peak bone mass, HIV-infected men on ART have lower BMD, markedly abnormal trabecular plate and cortical microarchitecture, and decreased whole bone stiffness, whether infected perinatally or during adolescence. Reduced bone strength in young adults infected with HIV early in life may place them at higher risk for fractures as they age.
bone microarchitecture; bone mineral density; bone strength; high-resolution peripheral quantitative computed tomography; peak bone mass; perinatal HIV infection
Hypoparathyroidism is associated with abnormal structural and dynamic skeletal properties. We hypothesized that parathyroid hormone(1–84) [PTH(1–84)] treatment would restore skeletal properties toward normal in hypoparathyroidism. Sixty-four subjects with hypoparathyroidism were treated with PTH(1–84) for 2 years. All subjects underwent histomorphometric assessment with percutaneous iliac crest bone biopsies. Biopsies were performed at baseline and at 1 or 2 years. Another group of subjects had a single biopsy at 3 months, having received tetracycline before beginning PTH(1–84) and prior to the biopsy (quadruple-label protocol). Measurement of biochemical bone turnover markers was performed. Structural changes after PTH(1–84) included reduced trabecular width (144 ± 34 µm to 128 ± 34 µm, p = 0.03) and increases in trabecular number (1.74 ± 0.34/mm to 2.07 ± 0.50/mm, p = 0.02) at 2 years. Cortical porosity increased at 2 years (7.4% ± 3.2% to 9.2% ± 2.4%, p = 0.03). Histomorphometrically measured dynamic parameters, including mineralizing surface, increased significantly at 3 months, peaking at 1 year (0.7% ± 0.6% to 7.1% ± 6.0%, p = 0.001) and persisting at 2 years. Biochemical measurements of bone turnover increased significantly, peaking at 5 to 9 months of therapy and persisting for 24 months. It is concluded that PTH(1–84) treatment of hypoparathyroidism is associated with increases in histomorphometric and biochemical indices of skeletal dynamics. Structural changes are consistent with an increased remodeling rate in both trabecular and cortical compartments with tunneling resorption in the former. These changes suggest that PTH(1–84) improves abnormal skeletal properties in hypoparathyroidism and restores bone metabolism toward normal euparathyroid levels.
Hypoparathyroidism; PTH(1–84); Bone histomorphometry; Bone turnover markers; Remodeling
Typically, in the milder form of primary hyperparathyroidism (PHPT), seen in most countries now, bone density by DXA and detailed analyses of iliac crest bone biopsies by histomorphometry and µCT show detrimental effects in cortical bone, whereas the trabecular site (lumbar spine by DXA) and the trabecular compartment (by bone biopsy) appear to be relatively well preserved. Despite these findings, fracture risk at both vertebral and non-vertebral sites is increased in PHPT. Emerging technologies, such as high-resolution peripheral quantitative computed tomography (HRpQCT), may provide additional insight into microstructural features at sites such as the forearm and tibia that have heretofore not been easily accessible. Using HRpQCT, we determined cortical and trabecular microstructure at the radius and tibia in 51 postmenopausal women with PHPT and 120 controls. Individual trabecula segmentation (ITS) and micro finite element (µFE) analyses of the HRpQCT images were also performed to further understand how the abnormalities seen by HRpQCT might translate into effects on bone strength. Women with PHPT showed, at both sites, decreased volumetric densities at trabecular and cortical compartments, thinner cortices, and more widely spaced and heterogeneously distributed trabeculae. At the radius, trabeculae were thinner and fewer in PHPT. The radius was affected to a greater extent in the trabecular compartment than the tibia. ITS analyses revealed, at both sites, that plate-like trabeculae were depleted, with a resultant reduction in the plate/rod ratio. Microarchitectural abnormalities were evident by decreased plate-rod and plate-plate junctions at the radius and tibia, and rod-rod junctions at the radius. These trabecular and cortical abnormalities resulted in decreased whole bone stiffness and trabecular stiffness. These results provide evidence that in PHPT, microstructural abnormalities are pervasive and not limited to the cortical compartment. They may help to account for increased global fracture risk in PHPT.
Primary hyperparathyroidism; high-resolution peripheral quantitative computed tomography; individual trabecula segmentation; finite element analysis; fracture risk
The objectives of this study were to evaluate the capability of a novel ultrasound device to clinically estimate bone mineral density (BMD) at the 1/3rd radius. The device rests on a desktop and is portable, and permits real-time evaluation of the radial BMD. The device measures two (2) net time delay (NTD) parameters, NTDDW and NTDCW. NTDDW is defined as the difference between the transit time of an ultrasound pulse to travel through soft-tissue, cortex and medullary cavity, and the transit time through soft tissue only of equal overall distance. NTDCW is defined as the difference between the transit time of an ultrasound pulse to travel through soft-tissue and cortex only, and the transit time through soft tissue only again of equal overall distance. The square root of the product of these two parameters is a measure of the radial BMD at the 1/3rd location as measured by dual-energy x-ray absorptiometry (DXA). A clinical IRB-approved study measured ultrasonically sixty adults at the 1/3rd radius. BMD was also measured at the same anatomical site and time using DXA. A linear regression using NTD produced a linear correlation coefficient of 0.93 (P<0.001). These results are consistent with previously reported simulation and in vitro studies. In conclusion, although x-ray methods are effective in bone mass assessment, osteoporosis remains one of the largest undiagnosed and under-diagnosed diseases in the world today. The research described here should enable significant expansion of diagnosis and monitoring of osteoporosis through a desktop device that ultrasonically assesses bone mass at the 1/3rd radius.
osteoporosis; bone mineral density; ultrasound; net time delay; DXA; radius
High-resolution peripheral quantitative computed tomography (HR-pQCT) has recently been introduced as a clinical research tool for in vivo assessment of bone quality. The utility of this technique to address important skeletal health questions requires translation to standardized multi-center data pools. Our goal was to evaluate the feasibility of pooling data in multi-center HR-pQCT imaging trials.
Reproducibility imaging experiments were performed using structure and composition-realistic phantoms constructed from cadaveric radii. Single-center precision was determined by repeat scanning over short (<72hrs), intermediate (3–5mo), and long-term intervals (28mo). Multi-center precision was determined by imaging the phantoms at nine different HR-pQCT centers. Least significant change (LSC) and root mean squared coefficient of variation (RMSCV) for each interval and across centers was calculated for bone density, geometry, microstructure, and biomechanical parameters.
Single-center short-term RMSCVs were <1% for all parameters except Ct.Th (1.1%), Ct.Th.SD (2.6%), Tb.Sp.SD (1.8%), and porosity measures (6–8%). Intermediate-term RMSCVs were generally not statistically different from short-term values. Long-term variability was significantly greater for all density measures (0.7–2.0%; p < 0.05 vs. short-term) and several structure measures: Ct.Th (3.4%; p < 0.01 vs. short-term), Ct.Po (15.4%; p < 0.01 vs. short-term), and Tb.Th (2.2%; p < 0.01 vs. short-term). Multi-center RMSCVs were also significantly higher than short-term values: 2–4% for density and µFE measures (p < 0.0001), 2.6–5.3% for morphometric measures (p < 0.001), while Ct.Po was 16.2% (p < 0.001).
In the absence of subject motion, multi-center precision errors for HR-pQCT parameters were generally less than 5%. Phantom-based multi-center precision was comparable to previously reported in vivo single-center precision errors, although this was approximately 2–5 times worse than ex vivo short-term precision. The data generated from this study will contribute to the future design and validation of standardized procedures that are broadly translatable to multi-center study designs.
HR-pQCT; osteoporosis; precision; bone; microstructure; bone strength; multi-center studies
Abnormal bone metabolism and progressive demineralization have been described in patients with heart failure (HF). We hypothesized that mechanical unloading through implantation of a ventricular assist device (VAD) with subsequent haemodynamic improvement would correct abnormal bone metabolism in patients with advanced HF.
Methods and results
Serum was collected from 14 controls, 20 patients with moderate HF, 34 patients with advanced HF undergoing VAD implantation, and 34 patients at the time of VAD explantation (mean duration: 169 ± 125 days). Bone metabolism markers were measured using enzyme-linked immunosorption assay (ELISA) or chemiluminescence immunoassay (CLIA). Compared with controls, HF patients showed increased parathyroid hormone (PTH: 42 ± 19 vs. 117 ± 117 pg/mL in HF; P < 0.02) with decreased 25-hydroxyvitamin D [25(OH)D: 29 ± 14 vs. 21 ± 11 ng/mL in HF; P = 0.05]. While procollagen-1 N-terminal peptide (P1NP) and osteocalcin were similar, cross-linked C- and N-telopeptides of type I collagen (CTX and NTX) were both higher in HF (NTX: 14 ± 6 vs. 20 ± 11 ng/mL; P < 0.05; CTX: 0.35 ± 0.13 vs. 1.05 ± 0.78 ng/mL; P < 0.01 for controls and HF, respectively). P1NP increased markedly after VAD implantation (49 ± 37 vs. 121 ± 62 ng/mL; P < 0.0001), with a mild decrease in CTX and NTX levels indicating a shift towards anabolic bone formation. Serum PTH correlated with estimated glomerular filtration rate (r = –0.245, P < 0.05).
Patients with advanced HF are characterized by increased levels of biochemical markers of bone resorption potentially as a result of secondary hyperparathyroidism and uncoupling of bone remodelling. Haemodynamic improvement and mechanical unloading after VAD implantation lead to correction of bone metabolism and increased levels of anabolic bone formation markers.
Heart failure; Bone metabolism; Ventricular assist; Device
Both type 1 diabetes mellitus and end stage renal disease are associated with increased fracture risk, likely due to metabolic abnormalities that reduce bone strength. Simultaneous pancreas-kidney transplantation is a treatment of choice for patients with both disorders, yet the effects of simultaneous pancreas-kidney versus kidney transplantation alone on post-transplantation fracture risk are unknown. From the United States Renal Data System we identified 11, 145 adults with type 1 diabetes undergoing transplantation of whom 4,933 had a simultaneous pancreas-kidney while 6, 212 had a kidney alone transplant between 2000 and 2006. Post-transplantation fractures resulting in hospitalization were identified from discharge codes. Time to first fracture was modeled and propensity score adjustment was used to balance covariates between groups. Fractures occurred in significantly fewer (4.7%) of pancreas-kidney compared to kidney-alone transplant (5.9%) cohorts. After gender stratification and adjustment for fracture covariates, pancreas-kidney transplantation was associated with a significant 31% reduction in fracture risk in men (hazard risk 0.69). Older age, white race, prior dialysis and pre transplantation fracture were also associated with increased fracture risk. Prospective studies are needed to determine the gender-specific mechanisms by which pancreas-kidney transplantation reduces fracture risk in men.
pancreas-kidney transplantation; fracture; kidney; diabetes; renal; gender differences; USRDS
Obese adults are frequently vitamin D deficient before bariatric surgery; whether similar abnormalities exist in morbidly obese adolescents is unknown.
To determine the prevalence of vitamin D deficiency in morbidly obese adolescents.
Cross-sectional study of preoperative laboratory measures from 236 adolescents evaluated for bariatric surgery.
The group (N = 219 with 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) levels; 76 boys, 143 girls; 15.9 ± 1.2 years; 43% Caucasian, 35% Hispanic, and 15% African American) had mean BMI of 47.6 ± 8.1 kg/m2. 25OHD levels were deficient (<20 ng/mL) in 53%; 8% had severe deficiency (<10 ng/mL); only 18% of patients were replete (>30 ng/mL). 25OHD levels were inversely associated with BMI (r = −0.28, < 0.0001) and PTH levels (r = −0.24, P = 0.0003). Race was the strongest predictor of 25OHD (P < 0.002); 82% of African Americans, 59% of Hispanics, and 37% of Caucasians were deficient. African American race, BMI, and PTH explained 21% of the variance in 25OHD (P < 0.0001).
Most adolescents presenting for bariatric surgery have suboptimal vitamin D levels, with African Americans and those with higher BMIs at greatest risk for vitamin D deficiency. All morbidly obese adolescents should be screened for vitamin D deficiency before bariatric procedures.
Background. Obese adults are frequently vitamin D deficient before bariatric surgery; whether similar abnormalities exist in morbidly obese adolescents is unknown. Objective. To determine the prevalence of vitamin D deficiency in morbidly obese adolescents. Methods. Cross-sectional study of preoperative laboratory measures from 236 adolescents evaluated for bariatric surgery. Results. The group (N = 219 with 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) levels; 76 boys, 143 girls; 15.9 ± 1.2 years; 43% Caucasian, 35% Hispanic, and 15% African American) had mean BMI of 47.6 ± 8.1 kg/m2. 25OHD levels were deficient (<20 ng/mL) in 53%; 8% had severe deficiency (<10 ng/mL); only 18% of patients were replete (>30 ng/mL). 25OHD levels were inversely associated with BMI (r = −0.28, P < 0.0001) and PTH levels (r = −0.24, P = 0.0003). Race was the strongest predictor of 25OHD (P < 0.002); 82% of African Americans, 59% of Hispanics, and 37% of Caucasians were deficient. African American race, BMI, and PTH explained 21% of the variance in 25OHD (P < 0.0001). Conclusions. Most adolescents presenting for bariatric surgery have suboptimal vitamin D levels, with African Americans and those with higher BMIs at greatest risk for vitamin D deficiency. All morbidly obese adolescents should be screened for vitamin D deficiency before bariatric procedures.
Osteoporosis is typically diagnosed by dual energy x-ray absorptiometry (DXA) measurements of areal bone mineral density (aBMD). Emerging technologies, such as high-resolution peripheral quantitative computed tomography (HR-pQCT), may increase the diagnostic accuracy of DXA and enhance our mechanistic understanding of decreased bone strength in osteoporosis. Women with (n=68) and without (n=101) a history of postmenopausal fragility fracture had aBMD measured by DXA, trabecular plate and rod microarchitecture measured by HR-pQCT image-based individual trabeculae segmentation (ITS) analysis, and whole bone and trabecular bone stiffness by micro finite element analysis (μFEA) of HR-pQCT images at the radius and tibia. DXA T-scores were similar in women with and without fractures at the spine, hip and 1/3 radius, but lower in fracture subjects at the ultradistal radius. Trabecular microarchitecture of fracture subjects was characterized by preferential reductions in trabecular plate bone volume, number, and connectivity over rod trabecular parameters, loss of axially aligned trabeculae, and a more rod-like trabecular network. In addition, decreased thickness and size of trabecular plates were observed at the tibia. The differences between groups were greater at the radius than the tibia for plate number, rod bone volume fraction and number and plate-rod and rod-rod junction densities. Most differences between groups remained after adjustment for T-score by DXA. At a fixed bone volume fraction, trabecular plate volume, number and connectivity were directly associated with bone stiffness. In contrast, rod volume, number and connectivity were inversely associated with bone stiffness. In summary, HR-pQCT-based ITS and μFEA measurements discriminate fracture status in postmenopausal women independent of DXA measurements. Moreover, these results suggest that preferential loss of plate-like trabeculae contribute to lower trabecular bone and whole bone stiffness in women with fractures. We conclude that HR-pQCT-based ITS and μFEA measurements increase our understanding of the microstructural pathogenesis of fragility fracture in postmenopausal women.
bone micarchitecture; high-resolution peripheral quantitative computed tomography; individual trabecula segmentation; trabecular plate/rod; fragility fractures