Anomalies in the Measurement of Changes in Bone Mineral Density of the Spine by Dual-Energy X-ray Absorptiometry

Dual-energy X-ray absorptiometry (DXA) is frequently used for longitudinal studies of bone mineral status because of the high precision obtained, but evidence is emerging that the accuracy of measurements of changes may be a limitation because of artefacts of the analysis procedure, in particular, a dependence of the measured bone area (BA) on the bone mineral content (BMC). Results of spine bone mineral measurements taken at intervals with two DXA scanners, a Hologic QDR 1000W, and a Norland XR 26 HS, were examined. There was a consistent correlation between changes in BA and in BMC, with a slope of approximately 0.25 when expressed as percentages. A real change of BA of the magnitude observed is not feasible. There were no differences among the correlations for different instruments, genders, ages, or weight changes. There would appear to be an underestimation of changes in bone mineral density (BMD), but there is a possibility that some of the anomaly is manifested as an overestimation of a change in BMC. Phantom measurements were undertaken with the DXA scanners mentioned above and with a Lunar DPX. The phantoms consisted of simulations of the spine cut from aluminium sheet, so that the effective BMD could be varied. The dependence of the measured BA on BMC varied with the phantom outline, particularly the thickness of the transverse processes. Evidence was obtained of both an underestimate of BMD changes and an overestimate of BMC changes. There are errors in measuring spine changes, but these do not seem to be as serious as a previous report suggests for the Hologic scanner and are not likely to lead to misinterpretation of results. Received: 17 June 1997 / Accepted: 23 January 1998     

Dual Energy X-Ray Absorptiometry in Small Rats with Low Bone Mineral Density

The feasibility of dual energy X-ray absorptiometry (DXA) using the Norland XR-26 Mark II bone densitometer for measurements of bone mineral content (BMC) and bone mineral density (BMD) in small rats was evaluated. Thirty-two young, isogenic, Lewis rats (weights from 119 g to 227 g) were used; normal rats (n = 7) and rats with low BMD obtained from three different vitamin D-depleted models (n = 25). DXA measurements were performed using the special software for small animals. Duplicate scans of excised femurs performed at 2 mm/second (pixel size of 0.5 mm × 0.5 mm) were very precise measurements with a coefficient of variation (CV) below 1.6% in animals with normal BMD; in rats with low BMD, the CV was significantly higher (P= 0.02–0.04), 7.8% and 4.4% for BMC and BMD, respectively. Regression analysis demonstrated that these measurements were related to the ash weight (R² > 98.6%). The CV for measurements of the lumbar spine at 10 mm/second (pixel size 0.5 mm × 0.5 mm) was 2.6% and 2.2% for BMC and BMD, respectively in rats with normal BMD, and again higher (P= 0.03–0.14) in rats with low BMD, 7.3% and 4.7%, respectively, for BMC and BMD. Even though low CVs were obtained for total body duplicate scans (scan speed of 20 mm/second and a pixel size of 1.5 mm × 1.5 mm), the measurements were problematic for accuracy because of an overestimation of both BMC and the area of bone. Using these scan parameters the measurements of total body bone mineral could not be recommended in small rats with low BMD. Received: 21 May 1999 / Accepted: 3 August 2000 / Online publication: 22 December 2000     

The Effect of Peritoneal Dialysate on DXA Bone Densitometry Results in Patients with End-Stage Renal Disease

The bone mineral density of patients undergoing peritoneal dialysis (PD) is low compared to a healthy population. No studies have been conducted to investigate whether the presence of peritoneal dialysate affects dual-energy X-ray absorptiometry (DXA) results. We hypothesized that the presence of peritoneal dialysate would not affect the measurement of bone mineral density (BMD) or bone mineral content (BMC) in the spine. Thirty patients on PD had DXA scans of the lumbar spine and hip completed before and after the drainage of peritoneal dialysate. A paired t-test was used to compare the difference in area, BMC, and BMD before and after drainage of dialysate. A significant difference was found in the BMC of the spine before and after the drainage of dialyzate. We recommend that peritoneal dialyzate be removed prior to scanning patients on PD and that densitometry technologists should be observant about the presence of peritoneal dialysate.     

Comparison of Pencil-, Fan-, and Cone-Beam Dual X-ray Absorptiometers for Evaluation of Bone Mineral Content in Excised Rat Bone

The aim of the present study was to assess the reproducibility and accuracy of measurements done on excised rat bone with three different generations of densitometers: Hologic QDR2000 pencil beam, Hologic QDR4500 fan beam, and Lunar PIXImus cone beam. The coefficients of variation for repeated measurements of bone mineral content (BMC) were 0.62 and 0.85% for pencil beam, 1.73 and 3.59% for fan beam, and 0.70 and 1.52% for cone beam for femur and tibia, respectively. BMC and ash weight were linearly correlated: 0.998 for pencil, 0.984 for fan, and 0.995 for cone beam. However, the three densitometers overestimated BMC by 10.9, 12.6, and 3.1%, respectively, and the overestimation was found to be dependent on the net BMC. The highest coefficient of correlation was found between BMC measurements from pencil and cone beam (r = 0.995). Data from cone-beam DXA were, respectively, 8.8 and 9.2% lower than those from penciland fan-beam DXA. We conclude that the three DXA instruments precisely and accurately measure BMC in excised rat bone; however, DXA overestimates BMC with a dependence on the bone ash weight. This dependence was less pronounced with the cone-beam technology.     

Body Composition Measurements by Dual-Energy X-ray Absorptiometry Differ Between Two Analysis Modes

This study was undertaken to determine to what extent body-composition measurements by dual-energy X-ray absorptiometry (DXA) differed between two analysis modes (standard vs extended). Whole-body bone mineral density (BMD), bone mineral content (BMC), bone area (BA), fat mass (FM), lean mass (LM), and percentage of fat (%fat) of 263 women, aged 20-74 yr, were measured by DXA, with each scan analyzed by both the standard and extended analysis modes. The standard mode had significantly higher values for BMD, BMC, BA, and %fat, and significantly lower values for LM than extended mode (p < 0.05). The measurement error of BMC was highly correlated with the measurement error of BA (r = 0.93), thereby indicating the possibility of bone-edge instability by different analysis modes. Body mass index (BMI) was also significantly correlated with the measurement error of BMC (r = 0.75). The degree of obesity might be tightly associated with the occurrence of the measurement error. Caution is recommended when different analysis modes are used for making multicenter comparisons or assessing intervention-induced changes.     

Precision and Accuracy of a Transportable Dual-Energy X-ray Absorptiometry Unit for Bone Mineral Measurements in Guinea Pigs

Dual energy X-ray absorptiometry (DXA) is a valuable tool for measuring bone mineral content (BMC) and bone mineral density (BMD) in small-animal research. The present study was devised to establish guidelines and to define sites for bone mineral measurements in guinea pigs and to evaluate the accuracy of a new transportable research DXA unit. Repeated scans were performed on 30 guinea pig hindlimbs (in situ) as well as the isolated bones from these limbs (ex situ). Nine exactly specified regions of interest (ROIs) were analyzed twice for BMC and BMD by three different observers. Additionally, the BMC of whole bones and bone segments as measured by DXA was correlated to ash weights of bone in a subset of five animals to determine the accuracy of the DXA measurements. On ex situ scans, intra-observer variability for BMD ranged from 0.09% to 2.33% and inter-observer variability from 0.23% to 5.86% depending on the site studied, with smaller ROIs exhibiting more variability. Coefficients of variance (CV) for BMC measurements were slightly higher than for BMD. However, BMC offered a better correlation between in situ and ex situ values than BMD. On in situ scans, observer variability for BMD and BMC for comparable sites was higher than the ex situ variability. The results of this study indicate that DXA provides an accurate measurement of BMC even in small specimens. The precision of BMC and BMD measurements in situ can be improved considerably by using specific, well-defined ROIs and by careful placement of the bones to be scanned in close proximity to the scanning surface.     

Effect of bone strontium on BMD measurements.

Strontium ranelate is a new treatment for osteoporosis that is of interest for, among other reasons, its unusual effect on measurements of bone mineral density (BMD). When some of the calcium in bone is replaced by strontium, X-ray absorptiometry measurements of BMD are overestimated because strontium attenuates X-rays more strongly than calcium. In this study, we report the first theoretical estimation of this effect for measurements made using axial (spine and hip) dual-energy X-ray absorptiometry (DXA), peripheral DXA (pDXA), and single-energy quantitative computed tomography (SEQCT). Tables of X-ray attenuation coefficients were used to calculate values of the strontium ratio defined as the ratio of the percentage overestimation of BMD to the molar percentage of strontium (%Sr/[Ca+Sr]) in bone. For DXA measurements, the theoretical value of the strontium ratio increased slightly with increasing effective photon energy of the X-ray beam with figures of 9.0 for Osteometer DTX200 and G4 pDXA devices (Osteometer Meditech Inc., Hawthorne, CA), 10.0 for GE-Lunar DPX and Prodigy DXA systems (GE-Lunar, Madison, WI), 10.4 for Hologic QDR1000 and QDR2000, and 10.8 for Hologic QDR4500 and Discovery (Hologic Inc., Bedford, MA). Results for SEQCT also varied with the effective photon energy with strontium ratios of 6.2 at 60 keV and 4.4 at 80 keV. The results of the theoretical study are in good agreement with the experimental value of 10 reported by Pors Nielsen and colleagues for a variety of different axial DXA systems. A reliable figure for the strontium ratio is important for adjusting BMD measurements in strontium ranelate treated patients for the effect of bone strontium content. This latter correction will be required for the interpretation of future DXA scans in patients who have discontinued strontium ranelate treatment.     

Perspective on Fracture Risk and Phalangeal Bone Mineral Density

Current bone mineral density (BMD) represents the composite, cumulative effect of many past and present risk factors, including both genetic and lifestyle influences. Reduced BMD, increasing age, and the presence of pre-existing fractures independently increase the risk of osteoporotic fracture. BMD is the most clinically useful of these indicators. Assessment of phalangeal BMD by dual-energy X-ray absorptiometry (DXA) or radiographic absorptiometry (RA) has been shown to provide long-term value in predicting the risk of both hip and spine fracture. Data from phalangeal BMD measurements may be most valuable to the patient if they are used to compute the patient's remaining lifetime fracture probability (RLFP).     

用骨强度概念探索骨密度测量的诊断指标

30多年来，医学上一直用骨矿密度（BMD,g/cm^2）诊断骨质疏松，骨质疏松引起骨折，骨折由骨强度减低引起，体重是骨强度的重要决定因素。 本引入体重评价BMC（g）和BMD两个指标。结果，体重与BMC的相关明显强于与BMD的相关，证明男女之间的BMC差由体重引起，男女间相同体重配对的BMC没有差异，所以在评价骨的 力学强度上体重标准化后BMC优于BMC指标。     

Effects of strontium on bone strength, density, volume, and microarchitecture in laying hens.

Strontium has been reported to have beneficial effects on bone. Treatment of laying hens, which are susceptible to osteoporosis and bone fracture, with strontium increased DXA measurements of BMD and BMC and microCT measurements of bone volume and microarchitecture and improved the mechanical performance of whole bone, but had no effect on the estimated material properties of the bone tissue. INTRODUCTION: Strontium (Sr) has been reported to dissociate bone remodeling and have positive influences on bone formation. We supplemented the diet of laying hens, which are susceptible to osteoporosis and bone fracture, with Sr to study the capacity of the element to improve bone mechanical integrity and resistance to fracture. MATERIALS AND METHODS: Increasing dosages of Sr (0, 3000, 4500, and 6000 ppm) were fed to 196 13-week-old pullets for 11 months. BMD and BMC, as measured by conventional and DXA methods, microarchitectural parameters derived from microCT, and structural and material properties as determined by three-point bending test, were studied. Calcium (Ca), phosphorus (P), and Sr levels in plasma and bone, as well as egg output, shell quality, and composition, were assessed. RESULTS: Sr concentrations in plasma and bone increased in a dose-dependent manner without affecting Ca and P. Treatment with Sr increased BMD and BMC as measured by DXA, increased cortical and medullary bone volume, trabecular thickness, number, and surface, and improved whole bone ultimate load, but had no effect on the estimated material properties of diaphyseal bone. Sr also increased the ash content of eggshells and did not affect egg output and shell quality. CONCLUSIONS: Sr supplementation induced large positive effects on bone density, volume, and microarchitecture as measured by radiographic methods. Sr treatment also improved the structural strength of diaphyseal bone but had no effect on the estimated material properties of the bone tissue.     

Bone Mineral Density Measurement at Both Spine and Hip for Diagnosing Osteoporosis in Japanese Patients

In Japan, spinal dual-energy X-ray absorptiometry (DXA) has been commonly performed for diagnosing osteoporosis but scanning the proximal femur is not done widely. The latest Japanese guidelines for prevention and treatment of osteoporosis, revised in 2006, recommend bone mineral density (BMD) measurement at both spine and hip for diagnosing osteoporosis, although there have been no reports that proved the necessity of those measurements. One thousand forty-one women and 485 men with clinical suspicion of osteoporosis were enrolled in this study, and DXA was performed at both spine and hip. The proportions of the patients who had inconsistency between diagnosis of osteoporosis from spinal DXA and that of hip were estimated. As a result, 22% of women and 15% of men had an inconsistency with the diagnosis of osteoporosis using DXA at each measurement site. There was inconsistency in diagnosing osteoporosis using DXA at the spine and proximal femur measurement sites. Because spine and femoral DXA measurements complement each other in the diagnosis of osteoporosis, BMD measurement at both spine and hip should be performed for all Japanese patients who are suspected osteoporosis, regardless of age and sex.     

The accuracy of volumetric bone density measurements in dual X-ray absorptiometry

New developments in dual x-ray absorptiometry (DXA) allow the performance of high precision anteroposterior (AP) and lateral scans of spinal bone mineral density (BMD, units: g/cm²) without the patient moving from the supine position. Data from both projections may be combined to give an estimate of the true volumetric bone mineral density (VBMD, units: g/cm³) of the lumbar vertebral bodies. This report presents a cadaver study designed to validate DXA measurements of volumetric bone density. Sections of whole lumbar spine were scanned in AP and lateral projections in a water tank to simulate soft tissue. Individual vertebrae were then divided to separate the vertebral body from the neural arch, and vertebral body volume was measured using the displacement of sand. The bone mineral content (BMC) of vertebral bodies and neural arches was measured by ashing at 250°C for 60 hours followed by 500°C for a further 24 hours. The results showed that DXA scanning systematically underestimated ashing data by 14% for AP BMC, 33% for vertebral body BMC, 23% for vertebral body volume, and 12% for VBMD. Despite these significant systematic errors, the DXA measurements and ashing values were highly correlated (r=0.979-0.992). The results suggested that after allowing for the systematic errors, lateral DXA parameters related closely to true BMC, volume, and VBMD.     

Differential Effects of Bone Mineral Content and Bone Area on Vertebral Strength in a Swine Model

Since the biomechanical competence of a vertebral body may be closely related to the content and distribution of the bone mineral, we have evaluated the effects of projected vertebral bone area (BA) and bone mineral parameters [bone mineral content (BMC) or bone mineral density (BMD)] on their biomechanical competence. We used dual-energy X-ray absorptiometry (DXA) to assess the bone mineral parameters of 36 swine thoracic vertebrae (T1–T12) and 15 lumbar vertebrae (L1–L5) after removal of the posterior elements. The failure load, compressive stress, and the stored strain energy of these vertebral bodies were assessed by a uniaxial compressive test using an MTS 810 testing system. Multiple regression analysis showed a significantly negative effect of BA and significantly positive effect of BMC on the biomechanical competence (compressive stress, r²= 0.67, P < 0.0001; failure load, r²= 0.75, P < 0.0001). However, the stored strain energy was only related to the BMC (r²= 0.35, P < 0.0001). The contributory effects of BMC and BA on the biomechanical competence were not equal. The effects of BMC was larger than BA in determining the failure load and stored strain energy, whereas the reverse was found for the compressive stress. Using the log-transformed parameters as the regressors resulted in similar results. These results suggested the differential effects of BA and BMC in determining the biomechanical competence of vertebral bodies. We recommend the use of both parameters instead of BMD alone for evaluation of the vertebral biomechanical competence. Received: 26 June 1997 / Accepted: 8 January 1998     

The Range of Bone Mineral Density in Healthy Canarian Women by Dual X-ray Absorptiometry Radiography and Quantitative Computer Tomography

Bone mass measurements play a crucial role in the diagnosis of osteoporosis. According to a World Health Organization (WHO) Working Group, osteoporosis in women can be diagnosed if the value for bone mineral density (BMD) is 2.5 or more standard deviations below the mean value of a young reference population. This definition obviously requires the availability of normal data, which should ideally be obtained locally. The objective was establish normal values of BMD in the female Canarian population, by dual X-ray absorptiometry (DXA) in the lumbar spine and the proximal femur, and by quantitative computed tomography (QCT) in the lumbar spine, and to study the correlation between the results of both techniques and the changes with age. Seven hundred forty-four Healthy Canarian women, from 20-80 yr old were examined. Measurement of bone density was performed by an Hologic QDR 1000 densitometer (DXA) in the lumbar spine and proximal femur, and by a Toshiba scanner model 600 HQ in the lumbar spine. Both methods show that the peak bone mass is achieved in the fourth decade (30-39 yr). Bone density decreases thereafter with age in the lumbar spine (r = -0.3364 DXA and r = -0.6988 for QCT) and in the femoral neck (r = -0.3988). Bone density mean values obtained by DXA are very similar to those described in Spain and in other European female populations, using the same densitometer. The correlations between both techniques (DXA and QCT) were high and statistically significant (p < 0.001 in every case). Normal values in the normal Canarian women for DXA and QCT are provided. Our results are very similar to those previously described. These two techniques have a close correlation.     

Interpretation of whole body dual energy X-ray absorptiometry measures in children: comparison with peripheral quantitative computed tomography

The assessment of bone health in children requires strategies to minimize the confounding effects of bone size on dual energy X-ray absorptiometry (DXA) areal bone mineral density (BMD) results. Cortical bone composes 80% of the total skeletal bone mass. The objective of this study was to develop analytic strategies for the assessment of whole body DXA that describe the biomechanical characteristics of cortical bone across a wide range of body sizes using peripheral quantitative computed tomography (pQCT) measures of cortical geometry, density (mg/mm³), and strength as the gold standard. Whole body DXA (Hologic QDR 4500) and pQCT (Stratec XCT-2000) of the tibia diaphysis were completed in 150 healthy children 6–21 years of age. To assess DXA and pQCT measures relative to age, body size, and bone size, gender-specific regression models were used to establish z scores for DXA bone mineral content (BMC) for age, areal BMD for age, bone area for height, bone area for lean mass, BMC for height, BMC for lean mass, and BMC for bone area; and for pQCT, bone cross-sectional area (CSA) for tibia length and bone strength (stress-strain index, SSI) for tibia length. DXA bone area for height and BMC for height were both strongly and positively associated with pQCT CSA for length and with SSI for length (all P < 0.0001), suggesting that decreases in DXA bone area for height or DXA BMC for height represent narrower bones with less resistance to bending. DXA BMC for age (P < 0.01) and areal BMD (P < 0.05) for age were moderately correlated with strength. Neither DXA bone area for lean mass nor BMC for lean mass correlated with pQCT CSA for length or SSI for length. DXA BMC for bone area was weakly associated with pQCT SSI for length, in females only. Therefore, normalizing whole body DXA bone area for height and BMC for height provided the best measures of bone dimensions and strength. DXA BMC normalized for bone area and lean mass were poor indicators of bone strength.     

容积性定量CT测量股骨近端骨密度准确性研究

目的通过分别对比容积性定量CT(vQCT)、双能X射线吸收法(DXA)与灰化法测量股骨近端骨密度结果,确定并对比相关性,进行指导临床骨质疏松诊断及治疗。方法选取20个尸体股骨近端标本,先使用DXA骨密度仪扫描,测得骨矿含量(BMC)及骨密度(BMD)。再对标本相同部位行64层螺旋CT扫描,数据导入OsteoCAD软件自动分析得出骨密度值。应用灰化法得出标本灰质量密度。所有资料进行统计分析分别确定并对比vQCT及DXA测量的骨密度值与灰密度之间的相关性。结果vQCT测量股骨颈骨密度与灰质量密度线性相关性较好(r=0.852,P0.01),DXA与灰质量密度的相关性略差(r=0.807,P0.01)。结论vQCT测得的骨密度较DXA与灰质量密度线性相关性更好,可靠性高,对于诊断骨质疏松,预测骨质疏松性骨折,评价、指导骨质疏松骨折手术更有应用价值。     

The correction of BMD measurements for bone strontium content.

Strontium ranelate (SR) is a new oral treatment for osteoporosis associated with large increases in bone mineral density (BMD) compared with alternative therapies such as bisphosphonates. Much of the BMD increase during SR treatment is a physical effect caused by the increased attenuation of X-rays due to the accumulation of strontium in bone tissue. The aim of this study was to assess the contribution made by bone strontium content (BSC) to the overall BMD increase by evaluating the percentage F of the BMD change explained by the physical presence of strontium in bone. A value of F less than 100% would provide evidence of the anabolic effect of SR as an additional factor contributing to the overall BMD increase. Studies of mixtures of strontium hydroxyapatite (SrHA) and calcium hydroxyapatite (CaHA) scanned on a variety of dual-energy X-ray absorptiometry (DXA) systems show that a 1% molar ratio of SrHA/(CaHA+SrHA) causes a 10% overestimation of BMD. The correction of spine BMD measurements for the physical effects of strontium depends on knowledge of 2 further factors: (1) bone biopsy measurements of iliac crest BSC and (2) the ratio R of BSC at the DXA site to BSC at the iliac crest measured in animal studies. We used clinical trial data and values of R(spine) measured in studies of monkeys and beagle dogs to determine values of F(spine) for 1, 2, and 3 yr treatment with SR. Based on the average value of R(spine) approximately 0.7 for male and female monkeys, we found values for F(spine) approximately 75-80% for 1, 2, and 3 yr of treatment. Using the value of R(spine) approximately 1.0 from the beagle study gave values of F(spine) approximately 100%. Although values of F(spine) as low as 40% are possible, we conclude that the most likely figure is 75% or greater. However, it is apparent that there are large uncertainties in the correction of BMD results for the effect of bone strontium and that the most important of these is the inference of BSC values at DXA scan sites from measurements of iliac crest bone biopsy specimens.     

The Role of Body Mass Index, Insulin, and Adiponectin in the Relation Between Fat Distribution and Bone Mineral Density

Despite the positive association between body mass index (BMI) and bone mineral density (BMD) and content (BMC), the role of fat distribution in BMD/BMC remains unclear. We examined relationships between BMD/BMC and various measurements of fat distribution and studied the role of BMI, insulin, and adiponectin in these relations. Using a cross-sectional investigation of 2631 participants from the Erasmus Rucphen Family study, we studied associations between BMD (using dual-energy X-ray absorptiometry (DXA]) at the hip, lumbar spine, total body (BMD and BMC), and fat distribution by the waist-to-hip ratio (WHR), waist-to-thigh ratio (WTR), and DXA-based trunk-to-leg fat ratio and android-to-gynoid fat ratio. Analyses were stratified by gender and median age (48.0 years in women and 49.2 years in men) and were performed with and without adjustment for BMI, fasting insulin, and adiponectin. Using linear regression (adjusting for age, height, smoking, and use of alcohol), most relationships between fat distribution and BMD and BMC were positive, except for WTR. After BMI adjustment, most correlations were negative except for trunk-to-leg fat ratio in both genders. No consistent influence of age or menopausal status was found. Insulin and adiponectin levels did not explain either positive or negative associations. In conclusion, positive associations between android fat distribution and BMD/BMC are explained by higher BMI but not by higher insulin and/or lower adiponectin levels. Inverse associations after adjustment for BMI suggest that android fat deposition as measured by the WHR, WTR, and DXA-based android-to-gynoid fat ratio is not beneficial and possibly even deleterious for bone.     

Effect of Hand Dominance on Bone Mass Measurement in Sedentary Individuals

The aim of this study was to determine in healthy sedentary subjects the effect of hand dominance on side-to-side difference in bone area and bone mass for upper and lower extremities. Dual-energy X-ray absorptiometry (DXA) measurements of both forearms and hips were performed on 193 right-handed and 20 left-handed subjects as determined by self-report. Scan acquisition and scan analyses were performed by one investigator, but all scan pairs were independently assessed for symmetry of positioning and movement artifacts by three investigators. Results show that DXA measurements between sides may be highly correlated regardless of the symmetry of the scan pair. However, asymmetric DXA scan pairs may have more than twice the side-to-side difference found in symmetric DXA scan pairs at the hip. Side-to-side differences between subregions were greater than the differences between measurements at the total radius, ulna, or hip. For symmetric pairs of DXA scans, the dominant forearm has significantly higher bone area and bone mineral content (BMC). Bone mineral density (BMD) was significantly higher only in the ulna of the dominant forearm. However, the nondominant forearm has higher values than dominant forearm in at least one DXA measurement in >24% of the subjects. There were no significant differences in any DXA measurements between hips, and higher DXA measurements did not occur significantly more frequently at the hip corresponding to the dominant hand. We conclude that healthy sedentary subjects tend to have proportionally higher bone area and BMC in the dominant forearm that results in similar BMD between dominant and nondominant forearms. This relationship does not appear to be applicable to measurements at the hip. In addition, there is a significant proportion of subjects with higher bone area and BMC in the nondominant extremities. Thus, in sedentary subjects, the consistency in the use of same extremity and the consistency in scan acquisition techniques and scan analyses is of greater importance than the selection of an extremity based on hand dominance in DXA studies.     

葛根素对绝经后骨质疏松大鼠不同部位骨骼的抗骨质疏松作用差异的研究

目的本文拟通过动物实验研究葛根素对大鼠骨密度的影响，探讨葛根素对不同部位骨骼抗骨质疏松作用的差异。 方法对24只雌性SD大鼠行双侧卵巢切除术，构建大鼠绝经后骨质疏松模型。采用葛根素处理大鼠后，分别于第2、4、8、12周采用双能X射线吸收法（DXA）检测其各部位骨骼骨密度随时间发生的变化，并对比不同部位骨骼骨密度、骨矿含量的差异，同时通过组织切片观察葛根素对骨组织微结构的影响。 结果葛根素应用后的第8周疗效最为显著，经葛根素处理后股骨远端、腰椎等松质骨的骨密度、骨矿含量显著提高，且骨小梁更粗、数量更多，而股骨中段等皮质骨的骨密度、骨矿含量变化则不大。 结论葛根素对绝经后骨质疏松大鼠松质骨的抗骨质疏松作用优于皮质骨。