Dual-energy X-ray Absorptiometry Bone Mineral Density Research Articles

Influence of bone quality on the strength of internal and external fixation of tibial plateau fractures

We studied the influence of different parameters of bone quality on the fixation strength of bicondylar tibial plateau fractures and examined the relationship between these parameters. Bone quality was measured in the plateau of 16 cadaveric tibias using three modalities: dual-energy X-ray absorptiometry (DXA), peripheral quantitative computer tomography (pQCT), and spectral analysis of digitized radiographs (SADR). The tibias were divided into two groups by the median bone mineral density (BMD) and randomized to receive either dual plating or external fixator for the stabilization of a standardized bicondylar tibial fracture. The fixed fractures were subjected to axial compression until failure. DXA BMD correlated most significantly with the failure load (r>or=0.79, p<0.001), followed by the pQCT parameters of cancellous bone (0.52>or=r>or=0.73, p<0.01). Similar strong correlations were also evident in both fixation methods. For parameters derived from SADR, only those including both longitudinal and transverse trabecular orientations had modest correlation with the fixation strength (0.53>or=r>or=0.71, p<0.01). The failure loads of the two fixation techniques were not significantly different (mean+/-SD=3522+/-1386 N and 3710+/-1356 N, respectively, p=0.78). However, BMD in the dual-plating group influenced the failure load significantly (p=0.03), whereas in the external fixation group this was less evident (p=0.100). The majority of bone quality parameters that correlated with fixation strength were also strongly correlated with each other, particularly the BMDs measured by DXA and pQCT. This is the first study that relates fixation strength of bicondylar tibial plateau fractures to bone quality assessed at the same anatomical site. BMD around the fracture site had the best correlation with the failure load regardless of the fixation technique. The two fixation methods tested performed equally well, and the choice between them depends on the soft tissue condition and surgeon preference.

Osteoprotegerin and Bone Mass in Squamous Cell Head and Neck Cancer Patients

Osteoprotegerin (OPG) is considered one of the main regulators of bone remodeling. Various patterns of serum OPG levels have been described in different types of tumors. We undertook this study to determine serum OPG levels in patients with squamous cell head and neck cancer (SCHNC), analyzing their relationship with other metabolic bone parameters and bone mineral density (BMD), as well as the possible influence of chemotherapy. Forty male patients with localized SCHNC were studied, and their results were compared with those of 40 healthy male controls. The type of treatment followed by each patient was noted. Age, weight, height, and lifestyle habits were recorded; and OPG, Ca(2+), intact parathyroid hormone (iPTH), 25-Hydroxyvitamin D (25OHD) and 1,25-Dihydroxyvitamin D (1,25(OH)(2)D), bone alkaline phosphatase, osteocalcin, and serum C-terminal cross-links telopeptide of type I collagen (ICTP) were determined. Dual-energy X-ray absorptiometry BMD at the lumbar spine, femoral neck, and hip was also measured. Serum OPG was higher in patients than in controls (91.7 +/- 25.8 vs. 77.2 +/- 26.3, P = 0.02). ICTP (a bone resorption marker) was 37% higher in patients (P = 0.007). Bone mass was lower in patients at the lumbar spine, femoral neck, and total hip. Lumbar spine Z-score showed a significant progressive decrease in controls, stage I-III patients, and stage IV patients. Logistic regression analysis showed a significant association between the disease and serum OPG levels, the odds ratio per standard deviation increase of this being 1.9 (95% confidence interval 1.1-3.8, P = 0.04) after adjusting for bone mass and ICTP serum levels, as well as for alcohol and smoking history. Adjustment for alcohol intake and tobacco use did not cancel out BMD differences between patients and controls. Patients with SCHNC show increased OPG serum levels, increased bone resorption, and decreased bone mass. The OPG rise appears to be unrelated to the BMD decrease, and the BMD decrease seems to be, at least in part, independent of smoking and drinking habits. No differences in either OPG or BMD were seen between patients with and without chemotherapy. Further studies are needed to clarify the mechanisms responsible for OPG and BMD changes in SCHNC.

Bone Mineral Density and Content: Dual Energy X‐ray Absorptiometry versus Peripheral Quantitative Computed Tomography

Dual energy x-ray absorptiometry (DXA) assesses bone mineral density (BMD) and content (BMC), but does not differentiate between cortical (Cr) and trabecular (Tb) bone, independent contributors to bone strength and fracture risk. Peripheral quantitative computed tomography (pQCT) provides a 3-D image of bone and assesses Tb and Cr bone. We compared total (To) BMC, TbBMC, volumetric (v) BMD, and TbBMD of the 4% distal tibia, and ToBMC, CrBMC, vBMD, and CrBMD of the 33% midshaft femur using pQCT to lumbar spine (Sp), hip, and femoral neck (FN) BMD and BMC from DXA in healthy, postmenopausal women. Tibia pQCT BMC and BMD measures were highly correlated (p<0.0001) with DXA measures, while femur pQCT was related to hip and FN BMC and BMD DXA measures, but not spine BMD DXA (Table 1). Table 1. Correlation Coefficients between DXA and pQCT Measures (N=187) Skeletal heterogeneity between axial and peripheral sites suggests that BMD measures from one site are not a good proxy for another BMD site. Further studies are needed to determine the relevance of peripheral densitometry data. Supported by NIAMS/NIH (AR046922); USDA, ARS, WHNRC.

Method for Cortical Bone Structural Analysis From Magnetic Resonance Images 1

Quantitative evaluation of cortical bone architecture as a means to assess bone strength typically is accomplished on the basis of images obtained by means of dual-energy X-ray absorptiometry (DXA) or computed tomography. Magnetic resonance (MR) imaging has potential advantages for this task in that it allows imaging in arbitrary scan planes at high spatial resolution. However, several hurdles have to be overcome to make this approach practical, including resolution of issues related to nonlinear receive coil sensitivity, variations in marrow composition, and the presence of periosteal isointense tissues, which all complicate segmentation. The aim of this study is to develop MR acquisition and analysis methods optimized for the detection of cortical boundaries in such complex geometries as the femoral neck. Cortical boundary detection is achieved by radially tracing intensity profiles that intersect the periosteal and endosteal boundaries of bone. Profiles subsequently are normalized to the intensity of the marrow signal, processed with morphologic image operators, and binarized. The resulting boundaries are mapped back onto the spatial image, and erroneous boundary points are removed. From the detected cortical boundaries, cortical cross-sectional area and thickness are computed. The method was evaluated on cortical bone specimens and human volunteers on the basis of high-resolution images acquired at a 1.5-Tesla field strength. To assess whether the method is sensitive to detect the expected dependencies of cortical parameters in weight-bearing bone on overall habitus, 10 women aged 46-73 years (mean age, 56 years) underwent the cortical imaging protocol in the proximal femur, and results were compared with DXA bone mineral density parameters of the hip and spine. Reproducibility was approximately 2%. Double oblique images of the femoral neck in the 10 women studied showed that cortical cross-sectional area correlated strongly with height (r = 0.88; p = .0008), whereas cortical diameter versus age approached significance (r = 0.61; p = .06). Measurements in specimens of some cortical parameters indicated resolution dependence. However, note that specimen ranking within each parameter remained constant across all resolutions studied. Data suggest the new method to be robust and applicable on standard clinical MR scanners at arbitrary anatomic locations to yield clinically meaningful quantitative results.

Comparison of DXA, QCT and trabecular structure in β‐thalassaemia

Osteopathy, as a major feature of homozygous beta-thalassaemia, is a multifactorial disorder, not fully understood. We studied the lumbar vertebrae of 48 patients using Dual-Energy X-ray Absorptiometry (DXA) and Quantitative Computed Tomography (QCT), and we focused on structural properties, assessed by High Resolution Computed Tomography (HRCT). Bone Mineral Density (BMD) values were expressed as Z-scores and the results were correlated. The effect of age, sex, and type of thalassaemia and hormonal factors on BMD was assessed. We estimated, with HRCT, the cortex integrity and the number and thickness of trabeculae; the latter were classified to a three-grade scale. Our results showed the overall prevalence of osteoporosis to be 44% with DXA and 6% with QCT. Both techniques revealed an inverse correlation between age and BMD, whereas hormonal factors demonstrated associations with QCT and DXA measurements. The correlation coefficient between DXA's BMD and QCT's trabecular BMD was 0.545 (P < 0.001) whereas the corresponding value for Z-scores was r = 0.491 (P < 0.001). The classification of the patients into normal, osteopenic and osteoporotic categories, using QCT's Z, was in better agreement with the assignment based on trabecular number (K = 0.209, P = 0.053) than the classification using DXA's Z (K = 0.145, P = 0.120). Cortex evaluation by HRCT showed discontinuity in 15 patients. Both methods indicate a progression of osteoporosis with age. Hormonal deficiency is associated with thalassaemic osteoporosis whereas the visual estimation of cortex indicates that Thalassaemia Intermedia (TI) patients could be more affected than Thalassaemia Major (TM). Using the trabecular number as an indicator of osteoporosis, it seems that QCT may evaluate osteopathy better than DXA. Since the former has the ability to measure trabecular and cortical BMD separately, it could give early indication of which changes more rapidly and to what degree.

Can peripheral DXA measurements be used to predict fractures in elderly women living in the community?

While axial dual energy X-ray absorptiometry (DXA) is the accepted "gold standard" method both for diagnosing osteoporosis and predicting fractures, appropriate equipment is not universally available. Peripheral bone mass measurements may have the potential to identify patients at risk of fracture and to be used to target appropriate treatment. We assessed the effectiveness of peripheral DXA (PIXI, GELunar) in the assessment of risk and targeting treatment to prevent future fracture in 7,604 women aged 60-80 from five centres across Britain. At enrolment women completed a lifestyle and risk factor questionnaire and had a PIXI DXA scan of the heel. Women were categorised by PIXI DXA bone mineral density (BMD) into high, medium or low risk of future osteoporotic fracture. Treatment was recommended to those at highest risk. Follow-up was by simple questionnaire 18-24 months after baseline assessment. Seventy-four percent returned the follow-up questionnaire. The area under the receiver operator characteristic (ROC) curves for any fracture and osteoporotic fracture were comparable to those published using other sites and technologies. A 1-SD decrease in PIXI BMD was associated with an 86% increase in risk of osteoporotic fracture. Of the women identified as high risk, 74% had started treatment following their heel scan and 84.7% continued to take treatment at follow-up. No significant difference was noted in fracture rates in those who started treatment after assessment compared to those who did not. While peripheral DXA is highly effective for predicting older women who are at increased risk of future fracture, it has yet to be established as an effective method for targeting bisphosphonate or other therapy.

Bone measures in HIV-1 infected children and adolescents: disparity between quantitative computed tomography and dual-energy X-ray absorptiometry measurements

Investigators have found that dual-energy X-ray absorptiometry (DXA) of areal bone mineral density (BMD) values in HIV-1 infected children and adolescents are reduced. Volumetric bone density (BD) measured by quantitative computed tomography (CT) in this population has not been studied. This study was designed to evaluate bone measurements in HIV-1 infected children and adolescents using DXA and CT. Fifty-eight children and adolescents (32 females and 26 males with a mean age +/- SD of 12.0+/-3.9 years, age range 5.0-19.4 years) with perinatally acquired HIV-1 infection underwent simultaneous bone area and density evaluation by DXA and CT. Height and weight measurements as well as pubertal assessment were performed on the same day. All but four subjects were receiving highly active antiretroviral therapy (HAART). Subjects were matched with healthy children and adolescents for age, gender, and ethnicity. HIV-1 infected children were significantly shorter (P <0.001), lighter (P <0.005), and had delayed puberty (P <0.001) compared to controls. Using DXA, HIV-1 infected subjects had significantly less bone area (P <0.001), bone mineral content (BMC) (P <0.005), and BMD (P <0.05) at the vertebral level compared to controls. In addition, bone area (P <0.001), BMC (P <0.001), and BMD (P <0.005) of the whole body were also reduced relative to controls. In contrast, using CT, HIV-1 infected subjects had similar vertebral BD compared to controls, but smaller vertebral height and cross-sectional area (CSA) (P =0.01 and P <0.005, respectively). DXA Z-scores provided values significantly lower than CT Z-scores in the HIV-1 infected population (P <0.01). After accounting for weight and vertebral height, stepwise multiple regression demonstrated that the prediction of CT BD values of L1 to L3 from DXA values of these vertebrae was significantly improved. HIV-1 infected children and adolescents have lower vertebral and whole body BMC and BMD DXA measures. In contrast, vertebral BD measurements by CT are normal. The lower bone measurements were primarily due to the decreased bone and body size of the HIV-1 subjects.

Association of an aromatase TTTA repeat polymorphism with circulating estrogen, bone structure, and biochemistry in older women

Osteoporosis is a disease that is strongly genetically determined. Aromatase converts androgens to estradiol in postmenopausal women, therefore polymorphisms of the gene for this enzyme may be associated with bone mass and fracture. We investigated the association of the TTTA microsatellite polymorphism in intron 4 of the aromatase (CYP19) gene with bone mineral density (BMD) and fracture in 1,257 women aged 70 yr and greater. The data obtained were stratified based on the presence or absence of a [TTTA]n of 7 (A2), determined from a preliminary analysis of hip dual-energy X-ray absorptiometry BMD, which was present in 27% of the population. The presence of an A2 allele was associated with a higher free estradiol index (0.52 +/- 0.49, P = 0.049) compared with the absence of an A2 allele (0.47 +/- 0.45); higher BMD at all sites of the hip (3.4% total hip, 2.3% femoral neck, 3.6% intertrochanter, 4.1% trochanter) and the lumbar spine (12.7%); higher values for the calcaneal quantitative ultrasound parameters broadband ultrasound (1.3%), speed of sound (0.4%), and stiffness (3.7%); and higher peripheral quantitative computed tomography measures for total (3.4%), trabecular (3.3%), and cortical BMD (3.3%) and the derived stress strain index (SSI) parameters SSI polar (6.4%) and SSI x (6.8%) values. A lower deoxypryridinoline creatinine ratio was observed in subjects with an A2 allele (30.3 +/- 10.4 vs. 27.1 +/- 9.1, P = 0.03). The A2 allele was associated with a lower prevalence of vertebral fracture in subjects who were osteoporotic (odds ratio 0.27, confidence interval 0.09-0.79). Therefore, a common polymorphism of the aromatase gene, perhaps in linkage disequilibrium with a functionally significant CYP19 polymorphism, is associated with bone structure and bone turnover, either by local effects or by effects on circulating bioactive estrogen.

Comparison between the Klemetti index and heel DXA BMD measurements in the diagnosis of reduced skeletal bone mineral density in the elderly

Osteopenia/osteoporosis affect many elderly people and might not be detected until symptoms of fractures occur. Early detection of osteopenia/osteoporosis is important and would allow preventive measures and treatment. Access to screening for osteopenia/osteoporosis is often limited, whereas panoramic radiography is commonly used in dentistry. The aim of this study was to determine the validity of the Klemetti index (KI), measured on panoramic radiographs, in the diagnosis of osteopenia/osteoporosis as defined by a bone mineral density (BMD) measurement below -1.5 standard deviations (SDs) of a community based sample. In total, 211 consecutive participants (102 men and 109 women) 60-96 years in the SNAC-Blekinge study (Swedish National Study on Ageing and Care) underwent bone densitometry [by dual-energy X-ray absorptiometry (DXA)] of both heels. A panoramic radiograph was taken of each participant, and mandibular cortex on a panoramic radiograph was classified as '0' or normal (even and sharp endosteal margin), '1', moderately eroded (evidence of lacunar resorption or endosteal cortical residues), or '2', severely eroded (unequivocal porosity). From logistic regression, the odds ratio of having a BMD measurement below -1.5 SD was 8.04 (95% CI 2.39 to 27.12, P<0.001) in the 'osteopenic' (KI category 2), compared with the 'normal' group (KI categories 0 and 1). Receiver operating characteristic (ROC) curve analysis was used to measure the validity of the KI indicating osteopenia (KI category 2) in predicting reduced BMD. This point provided a sensitivity of 50% and a specificity of 89%. Positive and negative predictive values were 21% and 97%, respectively. There were 87% correctly classified subjects. The area under the ROC curve was 0.64. The present study demonstrated that a negative finding (KI category <2) is highly predictive of the absence of osteopenia/osteoporosis as defined by the DXA measurements.

ESTIMATION OF LOW BONE MASS FOR THE ASSESSMENT OF OSTEOPOROSIS FRACTURE RISK IN INDIAN MEN AND WOMEN USING QUANTITATIVE ULTRASOUND AND DUAL ENERGY X-RAY ABSORPTIOMETRY

The objective of the present work is to estimate the prevalence of low bone mass in Indian men and women for the assessment of osteoporosis and fracture risk using quantitative ultrasound and dual energy X-ray absorptiometry (DEXA) and carryout a comparative evaluation for early prediction of osteoporosis. Data collected in this study is analyzed to assess the diagnostic performance of the ultrasound and how its performance compares to DEXA bone mineral density (BMD). Quantitative ultrasound assessment of osteoporosis is carried out by measuring broadband ultrasound attenuation (BUA) and speed of sound (SOS) through calcaneus bone to provide a clinical measure called the stiffness index (SI). The SI is a measure of bone density used to predict the risk of bone fracture due to osteoporosis. Bone mineral density (BMD) measurement is performed in lumbar region (L1–L4) of the spine in anterior-posterior direction using DEXA. In both studies the data is found to be significant in men and women subjects with p&lt;0.0005 and percentage bone loss in men and women are significantly matching in both studies. Ultrasound performance correlates moderately well with DEXA (r=0.60 to 0.68) and provides comparable diagnostic sensitivity to spine BMD in predicting osteoporotic fractures.

The effect of valproate on bone mineral density in adult epileptic patients

The effect of long-term valproate (VPA) treatment on bone mineral density (BMD) in adult epileptic patients is not clearly known, although several studies have been done in children. In adult epileptic patients ( n=50; 24 men, 26 women) treated with VPA, the bone mineral density at lumbar level (L1–L4) and neck, trochanter, and intertrochanter regions of left femur was studied by dual energy X-ray absorptiometry (DXA) at the beginning of the study and after 6 months, with the specific aim to evaluate the effect of long-term valproate monoteraphy on bone mineral density. Routine biochemical parameters were also evaluated. Sixty healthy control subjects were evaluated. Control subjects were similar to patient group with respect to age, race (all White), geographic area, and socioeconomic status. Lumbar and femural BMD values were significantly lower in patient group than control group (0.814±0.157 g/cm 2 versus 0.894±0.102 g/cm 2, P=0.003) and (0.824±0.144 g/cm 2 versus 0.906±0.104 g/cm 2, P=0.001), respectively. Osteopenia were detected in 13 of 60 control subjects (22%) and the others had no osteoporosis. In epileptic group, osteoporosis and osteopenia were detected in 8 subjects (16%), and in 26 subjects (52%), respectively. In epileptic group 16 subjects were normal (32%) at the lumbar regions, and 7 had osteoporosis (14%), 28 had osteopenia (56%), and 15 were normal (30%) at the femoral region. In the second measurements of the patients on valproate treatment, after 6 months, all of the DXA BMD values had worsened compared with the first measurements ( P=0.001 for lumbar BMD values and P=0.004 for femural BMD values). In the patient group, a significant inverse correlation was observed between duration of valproate therapy and all DXA BMD values in the first and second measurements. Parathyroid hormone, alkaline phosphatase, and phosphor levels of patients were significantly higher than those of control group (52±11 pg/ml versus 46±13 pg/ml, P=0.013), (113±32 U/l versus 95±36 U/l, P=0.006), and (4.50±0.5 mg/dl versus 4.0±0.7 mg/dl, P=0.0001), respectively. However, all of the parameters were within the normal reference ranges. It has been concluded that long-term (more than one year) valproate treatment induces a decrease in bone mineral density in epileptic adults. However, the multivariate analysis did show no association between BMD changes and parathyroid hormone, alkaline phosphatase or phosphorus levels.

Comparison of ultrasound and X-ray absorptiometry bone measurements in a case control study of female rheumatoid arthritis patients and randomly selected subjects in the population.

To compare quantitative ultrasound (QUS) and dual-energy X-ray absorptiometry (DXA) bone measurements in female rheumatoid arthritis (RA) patients and controls were randomly selected from the population; secondly, to examine disease and demographic factors associated with these bone measurements. In a total of 115 RA patients (mean age 63.0 years) and 115 age- and gender-matched controls demographic and clinical variables were collected and heel QUS parameters [speed of sound (SOS), broadband ultrasound attenuation (BUA) and stiffness index (SI)] as well as DXA bone mineral density (BMD) at spine and hip were measured. The differences in QUS and DXA measurements between RA patients and controls were tested both on a group and on an individual level. Univariate and multivariate statistical tests were applied to explore for associations to the bone measurements. In the RA patients mean disease duration was 16.6 years, erythrocyte sedimentation rate 23.6 mm/h, M-HAQ 1.68, 28-swollen joint count 7.7, 18-deformed joint count 4.5, 50.0% were rheumatoid factor (RF) positive and 44.2% were current users of prednisolone. All bone measurements were reduced in RA patients compared with controls (SOS 1.9%, BUA 9.4%, SI 19.5%, femoral neck BMD 7.4%, total hip BMD 7.5%, spine L2-L4 BMD -3.0%). Only at spine was the BMD reduction not statistically significant ( P=0.21). In the subgroup of never users of prednisolone SOS was decreased by 1.4%, BUA by 3.7%, SI by 11.0, femoral neck BMD by 2.7%, and total hip BMD by 0.6%, whereas for spine L2-L4 BMD was increased by 4.3% and only for SOS and SI was the decrease statistically significant. The QUS discriminated better than DXA between patients and controls on a group level, but this difference in favor of QUS disappeared on an individual level when the measurement errors were taken into account. Age, BMI, RF and deformed joint count, but not corticosteroids, were independently associated with at least one of the QUS and one of the DXA measures; however, the association between disease-related variables was stronger with the QUS bone measures than with the DXA bone measures. The results for the quantitative QUS bone measures seem to mainly reflect bone mass. Disease-related variables in multivariate analysis remained independently associated with all QUS measures even when adjusting for DXA bone measures. Further studies are needed to examine if QUS may reflect other aspects than bone mass and be a potential better predictor for fracture risk in RA and corticosteroid-induced osteoporosis.

Accuracy and precision of bone mineral density and bone mineral content in excised rat humeri using fan beam dual-energy X-ray absorptiometry

The aim of this study was the evaluation of fan beam dual-energy X-ray absorptiometry (DXA) for measuring bone mineral density (BMD) and bone mineral content (BMC) of isolated rat humeri. Defleshed rat humeri from male Lewis rats were examined with a Hologic QDR 4500 A (Hologic, Inc., Bedford, MA) high-resolution densitometer both in water and 0.9% saline solution. The small animal scan protocol with the regional high-resolution mode was used. BMC measured by DXA was compared with bone dry weight, ash weight, and bone calcium content. Furthermore, DXA BMD and BMC precision were determined. We also evaluated the effect of salinity of the water bath in which the bones were measured. Correlations (r2) of BMC, as determined by DXA with dry weight, ash weight, and bone calcium content, were 0.978, 0.988, and 0.890, respectively. DXA overestimated ash weight by 5%–9%. Precision errors for BMC (BMD) were 0.90% (0.76%) without and 1.3 (0.86) with repositioning. Changes in the salinity of the water bath had a significant influence on the DXA results: At the 0.9% physiological level, BMC (−4.4%) and area (−4.1%), but not BMD, values were significantly lower (p < 0.005) compared with measurements in tap water. Fan beam DXA is a highly accurate and precise technique for measuring BMC and BMD in excised small animal bones. A physiological saline concentration in the water bath had a significant impact on BMC and area, but not on BMD, and should therefore be strictly controlled to avoid an underestimation of BMC.

Comparison of bone parameters by dual-energy X-ray absorptiometry and peripheral quantitative computed tomography in hutterite vs. non-hutterite women aged 35–60 years

A previous report of elevated dual-energy X-ray absorptiometry (DXA) bone mineral density (BMD) Z scores suggests that Hutterite females might be significantly less likely to develop osteoporosis compared with other U.S. females. In the present study, we sought to determine if high Hutterite DXA BMD Z scores were elevated because of larger bone size. Hutterites reside in isolated, self-sufficient colonies with an emphasis on agricultural production, and girls enter a strenuous task rotation at age 15 years. We obtained cross-sectional bone measurements of the 66% distal tibia using peripheral quantitative computed tomography (pQCT) to compare bone size and geometry on 97 Hutterite and 30 non-Hutterite women, aged 35–60 years. Total body (TB) and lumbar bone mineral content (BMC), BMD, and bone area measurements by DXA were available on a subset of the study population. We identified no differences between groups in pQCT total bone area, cortical bone area, or cortical bone density. Larger bone area by DXA was apparent in Hutterites compared with non-Hutterites at the TB (least square means: 2038 ± 8 cm 2 vs. 1953 ± 19 cm 2, p < 0.05) and lumbar (least square means: 58 ± 0.5 cm 2 vs. 57 ± 2 cm 2, p < 0.01) sites. TB BMC adjusted for TB bone area was marginally higher in Hutterites compared with non-Hutterites (least square means: 2341 ± 15 g vs. 2281 ± 30 g, p = 0.08). Hutterites had marginally higher TB BMD Z scores when controlling for weight and age (least square means: 1.3 ± 0.1 vs. 0.8 ± 0.2, p = 0.07). Hutterites had higher lumbar BMC adjusted for lumbar bone area and weight (least square means: 65 ± 1 g vs. 58 ± 2 g, p < 0.01) and higher weight-and age-adjusted lumbar BMD Z scores (least square means: 1.1 ± 0.1 vs. 0.1 ± 0.4, p = 0.01). Our data indicate that a true advantage in trabecular bone density probably exists among Hutterite women aged 35–60 years. Hutterite women might be protected against age-related fractures because of their larger bone size and higher bone density at normally susceptible trabecular sites.

Inaccuracies inherent in dual-energy X-ray absorptiometry in vivo bone mineral densitometry may flaw osteopenic/osteoporotic interpretations and mislead assessment of antiresorptive therapy effectiveness

New, anatomically realistic simulation studies based on a cadaveric lumbar vertebra and a broad range of soft tissue anthropometric representations have quantitatively delineated inaccuracies inherent in dual-energy X-ray absorptiometry (DXA) in vivo bone mineral density (BMD) methodology. It is found that systematic inaccuracies in DXA BMD measurements may readily exceed ±20% at typical in vivo lumbar vertebral sites, especially for osteopenic/osteoporotic, postmenopausal, and elderly patients. These findings are quantitatively compared with extensive clinical evidence of strong, positive correlations between soft tissue anthropometrics and DXA in vivo BMD upon which prior significant bone biology interpretations and implications have been based. The agreement is found to be both qualitatively and quantitatively excellent. Moreover, recent extensive multicenter clinical studies have also exposed new facets of strong linkages between body mass/percent body fat/body mass index (BMI) and DXA-measured BMD that are particularly relevant to osteopenia/osteoporosis and remedial effectiveness of antiresorptive drug therapy. These seemingly disparate and unrelated diagnostic and prognostic aspects of clinically observed associations between soft tissue anthropometrics and measured vertebral BMD are, in this study, self-consistently shown to share the common origin of being manifestations of systematic inherent inaccuracies in DXA in vivo BMD methodology, without the need to invoke any underlying biologically causal mechanism(s). These inaccuracies arise principally from absorptiometric disparities between the intra- and extraosseous soft tissues within the DXA scan region of interest. The present evaluative comparisons are based exclusively on an incisive and diverse body of clinical data that appears difficult to dismiss or discount. Previous invocations of biologically causal mechanisms responsible for this broad range of observations linking body mass, percent body fat, and/or BMI to measured BMD now appear questionable. This doubtful status has also been extended in the present work to previously reported relationships between antiresorptive therapies and observed changes in DXA-derived BMD. These findings strongly indicate that critical and insightful reassessments of diagnostic/prognostic imputations underpinned by DXA in vivo BMD measurements are warranted. It is suggested that a good deal of what is known of bone fragility, bone densitometry, antiresorptive drug efficacy, and/or other therapeutic regimens, if based on patient-specific in vivo DXA methodology, may prove to be equivocal and tenuous.

The contribution of cortical and cancellous bone to dual-energy X-ray absorptiometry measurements in the female proximal femur.

Dual-energy X-ray absorptiometry (DXA) is the most common method for determining bone mineral density (BMD) in the proximal femur. However, there remain questions concerning the contribution of cortical and cancellous bone to this technology in the proximal femur. The purpose of this investigation was to identify structural and compositional characteristics of human bone in the proximal femur that significantly influence DXA BMD measurements. Twenty-four femora were obtained at autopsy from Caucasian females ranging in age from 17 to 92 years (mean +/- SD, 61 +/- 25 years). DXA scans were performed on each specimen with a Hologic QDR-2000 densitometer. Direct measurements were determined from proximal femoral sections for cancellous bone (volume fraction, ash fraction, cancellous cross-sectional area and percent cancellous cross-sectional area), cortical bone (thickness, ash fraction, porosity, cortical cross-sectional area and percent cortical cross-sectional area) and anteroposterior thickness. These parameters were compared with the associated DXA measurements by means of simple and multiple regressions. Cancellous volume fraction was the best predictor of variability of DXA measurements for both the neck and trochanter, with an R2 of 0.87 and 0.76, respectively (p < 0.0001). There was only a minor influence of cortical factors such as thickness (neck and trochanter R2 = 0.51 and 0.42, respectively, p < 0.001) and trochanteric cross-sectional area (R2 = 0.21, p < 0.05). Although the accuracy for determining specific components of the proximal femur was low, the DXA BMD measurement was a strong predictor of cancellous bone factors, but not cortical bone factors that have been shown to change significantly with age.

Quantitative ultrasound of the tibia depends on both cortical density and thickness.

This study investigated whether tibial speed of sound (SOS; SoundScan 2000, Myriad Ultrasound Systems, Israel) reflects not only bone mineral density (BMD) but also tibial cortical thickness, as assessed by dual-energy X-ray absorptiometry (DXA) and Quantitative CT (QCT) at a site-matched location. The secondary focus of the study was how tibial SOS compares with BMD at the spine and the hip, the most widely used locations for densitometry. Twenty-two young normal (N) and 23 postmenopausal women with spinal fractures (Fx) (mean (SD) age 35 (8) and 70 (5) years) underwent quantitative ultrasound (QUS) SOS measurement at the left tibial midshaft. From site-matched QCT scans (three 3-mm slices spaced along the QUS measurement region), BMD and cortical thickness were computed (QCT-cBMD, QCT-cTh). The cortex in the CT images was then subdivided into three concentric and equally spaced bands, and QCT-cBMD was computed separately for each band. DXA was performed at the mid-tibia (TIB BMD), at the spine (SPINE BMD) and the hip (total hip, HIP BMD). Correlation coefficients between parameters were determined with least-square linear fits. Intergroup differences were assessed by analysis of covariance, whose r2 value reflects the percentage variation in the data explained by group assignment. SOS correlated significantly with site-matched parameters (QCT-cBMD, OCT-cTh and TIB BMD, all r = 0.6, p < 0.001), SPINE BMD and HIP BMD (both r = 0.5, p < 0.001). Multiple regression with both QCT-cBMD and QCT-cTh against SOS yielded r = 0.7 with both parameters contributing significantly. For the cortex band subdivision, SOS correlated better with QCT-cBMD in the outermost band of the cortex (r = 0.67) than with the more central bands (r = 0.59 and r = 0.53). Group assignment could best explain SPINE BMD (r2 = 0.62) and HIP BMD (r2 = 0.51). SOS was comparable to TIB BMD (r2 = 0.3 vs. r2 = 0.35).: Our findings suggest that the tibial SOS measurement depends on both the thickness and density of the tibia, but is more strongly influenced by the density of the cortex near the surface than by its interior parts. The power of tibial ultrasound to discriminate between normal and fracture patients was less than that of spinal and femoral DXA BMD and comparable to site-matched DXA BMD.

Inaccuracies inherent in patient-specific dual-energy X-ray absorptiometry bone mineral density measurements: comprehensive phantom-based evaluation.

An extensive series of dual-energy X-ray absorptiometry (DXA) scans and dual polyenergetic X-ray simulation studies of 150 different phantom arrays were carried out to evaluate quantitatively the extent of systematic inaccuracies inherent in DXA in vivo bone mineral density (BMD). These measurements are particularly relevant to lumbar vertebral and proximal femoral sites. The phantoms were specially fabricated near perfect absorptiometric representations of bone material, red marrow (RM) and yellow marrow (YM), and extraosseous mixtures of fat (F) and lean muscle that spanned the full range of soft tissue anthropometrics encountered clinically. In each case, the DXA-measured BMD values obtained using Hologic, Lunar, and Norland densitometers were found to be virtually the same and to be in excellent agreement with the corresponding quantitative simulation study BMD results. Comparisons of the known phantom BMD values and DXA-measured BMD in each case allowed the BMD inaccuracies to be evaluated. These present findings show that these ubiquitous inaccuracies in DXA BMD methodology are of in vivo soft tissue anthropometric genesis. It is found that patient-specific DXA-measured in vivo BMD inaccuracies as high as 20% or more can be readily anticipated clinically, particularly in cases of osteopenic, osteoporotic, and elderly patients. As these inaccuracies exceed considerably DXA precision errors, they may compromise patient-specific evaluations of fracture risk and, in prospective studies, mask or exaggerate clinically significant true changes in BMD. It is concluded that the magnitudes and variability of inherent inaccuracies in DXA-measured in vivo BMD underscore the need for prudence and circumspection in interpretations and assessments of DXA-based clinical studies.

Prevalence Of Osteoporosis In Women: Variation With Skeletal Site Of Measurement Of Bone Mineral Density

ObjectiveTo determine retrospectively the prevalence of osteoporosis in a referral population of female patients and to compare the sensitivity for diagnosing osteoporosis by dual-energy x-ray absorptiometry (DXA) measurements of bone mineral density (BMD) at multiple skeletal sites. MethodsWe studied the data from 625 consecutive women (mean age, 57.3 ± 13.9 years), who had been referred to our center for lumbar spine (anteroposterior [AP] and lateral region) and hip (femoral neck [FN], Ward’s triangle [WT], trochanter, intertrochanteric region, and total hip) BMD measurements with use of DXA (Hologic QDR-2000) between June 1994 and July 1998. ResultsOsteoporosis (based on the World Health Organization definition—T-score of -2.5 or lower for BMD) was diagnosed by DXA at the following sites: AP spine in 21.7%, lateral spine in 43.2%, FN in 33.6%, WT in 49.1%, trochanter in 26.1%, intertrochanteric region in 25.9%, and total hip in 28.4% of study patients. Significant site differences were found in the prevalence of osteoporosis between the lateral and AP spine (P<0.001), as well as between WT and the FN, trochanter, intertrochanteric region, and total hip (P<0.001). In a subgroup of 71 women, forearm (ultradistal radius and radius 1/3 region) BMD results indicated low sensitivity for diagnosing osteoporosis, similar to that seen at the AP spine, trochanter, and intertrochanteric region. Not surprisingly, the prevalence of osteoporosis increased with advancing age (15.5% in patients younger than 50 years, in comparison with 59.6% in those older than 69 years of age). The frequency of misclassification of patients (osteoporosis at one site and normal BMD at another) with use of the seven measurement sites was 16.6% (104 of the 625 patients). ConclusionFor diagnosis of osteoporosis, DXA BMD measurements are significantly more sensitive at the lateral spine than at the AP spine, as well as at WT than at the FN, trochanter, intertrochanteric region, and total hip sites. (Endocr Pract. 2000;6:127-131)

Age- and gender-related differences in vertebral bone mass, density, and strength.

This study was designed to evaluate age- and gender-related differences in vertebral bone mass, density, and strength by dual-energy X-ray absorptiometry (DXA), quantitative computed tomography (QCT), peripheral QCT (pQCT), ash measurements, and biomechanical testing. The material comprised human lumbar vertebral bodies (L3) from 51 females and 50 males (age-range: 18-96 years). The results showed that females had significantly lower vertebral body bone mass (ash weight) than males at any given age. The decline in bone mass with age was parallel for females and males. The different bone density measurements-cancellous ash density, total vertebral body ash density, DXA bone mineral density, QCT, and pQCT-showed no gender-related difference concerning numeric value or changes with age. Morphometrical measurements showed that females had smaller vertebral bodies (volumes) than males. Hence the females had significantly smaller cross-sectional area (CSA) of L3 than males (11.6 cm2 and 14.4 cm2, respectively). This led to females having lower maximum compressive load (N) than males at all ages, whereas maximum compressive stress (load/CSA) showed no gender-related difference. In conclusion, females have lower vertebral body bone mass than males at any given age, due to smaller vertebral bodies. Hence, maximum compressive load (strength not corrected for size) was lower in females. Vertebral body cancellous bone density and total-vertebral body density were equal when comparing genders, and no gender differences were found in the size-corrected strength: maximum compressive stress. The decrease with age in vertebral body compressive strength decrease was twice as large as the age decrease in density.