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DXA Measurements (dxa + measurement)
Selected AbstractsChildhood Fractures Do Not Predict Future Fractures: Results From the European Prospective Osteoporosis Study,,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2009Stephen R Pye Abstract Childhood fractures are common. Their clinical relevance to osteoporosis and fractures in later life is unclear. The aim of this study was to determine the predictive risk of childhood fracture on the risk of fracture in later life. Men and women ,50 yr of age were recruited from population registers for participation in the European Prospective Osteoporosis Study (EPOS). Subjects completed an interviewer administered questionnaire that included questions about previous fractures and the age at which the first of these fractures occurred. Lateral spine radiographs were performed to ascertain prevalent vertebral deformities. Subjects were followed prospectively by postal questionnaire to determine the occurrence of clinical fractures. A subsample of subjects had BMD measurements performed. Cox proportional hazards model was used to determine the predictive risk of childhood fracture between the ages of 8 and 18 yr on the risk of future limb fracture and logistic regression was used to determine the association between reported childhood fractures and prevalent vertebral deformity. A total of 6451 men (mean age, 63.8 yr) and 6936 women (mean age, 63.1 yr) were included in the analysis. Mean follow-up time was 3 yr. Of these, 574 (8.9%) men and 313 (4.5%) women reported a first fracture (any site) between the ages of 8 and 18 yr. A recalled history of any childhood fracture or forearm fracture was not associated with an increased risk of future limb fracture or prevalent vertebral deformity in either men or women. Among the 4807 subjects who had DXA measurements, there was no difference in bone mass among those subjects who had reported a childhood fracture and those who did not. Our data suggest that self-reported previous childhood fracture is not associated with an increased risk of future fracture in men or women. [source] Hip Fractures and the Contribution of Cortical Versus Trabecular Bone to Femoral Neck Strength,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2009Gerold Holzer Abstract Osteoporotic fractures are caused by both cortical thinning and trabecular bone loss. Both are seen to be important for bone fragility. The relative contributions of cortical versus trabecular bone have not been established. The aim of this study was to test the contribution of cortical versus trabecular bone to femoral neck stability in bone strength. In one femur from each pair of 18 human cadaver femurs (5 female; 4 male), trabecular bone was completely removed from the femoral neck, providing one bone with intact and the other without any trabecular structure in the femoral neck. Geometrical, X-ray, and DXA measurements were carried out before biomechanical testing (forces to fracture). Femoral necks were osteotomized, slices were analyzed for cross-sectional area (CSA) and cross-sectional moment of inertia (CSMI), and results were compared with biomechanical testing data. Differences between forces needed to fracture excavated and intact femurs (,F/F mean) was 7.0% on the average (range, 4.6,17.3%). CSA of removed spongiosa did not correlate with difference of fracture load (,F/F mean), nor did BMD. The relative contribution of trabecular versus cortical bone in respect to bone strength in the femoral neck seems to be marginal and seems to explain the subordinate role of trabecular bone and its changes in fracture risk and the effects of treatment options in preventing fractures. [source] Site-Specific Deterioration of Trabecular Bone Architecture in Men and Women With Advancing AgeJOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2008Eva-Maria Lochmüller Abstract We tested the hypothesis that the age dependence of trabecular bone microstructure differs between men and women and is specific to skeletal site. Furthermore, we aimed to investigate the microstructural pattern of bone loss in aging. Microstructural properties of trabecular bone were measured in vitro in 75 men and 75 age-matched women (age, 52,99 yr) using ,CT. Trabecular bone samples were scanned at a 26-,m isotropic resolution at seven anatomical sites (i.e., distal radius, T10 and L2 vertebrae, iliac crest, femoral neck and trochanter, and calcaneus). DXA measurements were obtained at the distal radius and proximal femur and QCT was used at T12. No significant decrease in bone density or structure with age was found in men using ,CT, DXA, or QCT at any of the anatomical sites. In women, a significant age-dependent decrease in BV/TV was observed at most sites, which was strongest at the iliac crest and weakest at the distal radius. At most sites, the reduction in BV/TV was associated with an increase in structure model index, decrease in Tb.N, and an increase in Tb.Sp. Only in the calcaneus was it associated with a significant decrease in Tb.Th. In conclusion, a significant, site-specific correlation of trabecular bone microstructure with age was found in women but not in men of advanced age. The microstructural basis by which a loss of BV/TV occurs with age can vary between anatomical sites. [source] Bone Strength at Clinically Relevant Sites Displays Substantial Heterogeneity and Is Best Predicted From Site-Specific Bone DensitometryJOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2002Felix Eckstein Ph.D. Abstract In this study we test the hypotheses that mechanical bone strength in elderly individuals displays substantial heterogeneity among clinically relevant skeletal sites, that ex situ dual-energy X-ray absorptiometry (DXA) provides better estimates of bone strength than in situ DXA, but that a site-specific approach of bone densitometry is nevertheless superior for optimal prediction of bone failure under in situ conditions. DXA measurements were obtained of the lumbar spine, the left femur, the left radius, and the total body in 110 human cadavers (age, 80.6 ± 10.5 years; 72 female, 38 male), including the skin and soft tissues. The bones were then excised, spinal and femoral DXA being repeated ex situ. Mechanical failure tests were performed on thoracic vertebra 10 and lumbar vertebra 3 (compressive loading of a functional unit), the left and right femur (side impact and vertical loading configuration), and the left and right distal radius (fall configuration, axial compression, and 3-point-bending). The failure loads displayed only very moderate correlation among sites (r = 0.39 to 0.63). Ex situ DXA displayed slightly higher correlations with failure loads compared with those of in situ DXA, but the differences were not significant and relatively small. Under in situ conditions, DXA predicted 50-60% of the variability in bone failure loads at identical (or closely adjacent) sites, but only around 20-35% at distant sites, advocating a site-specific approach of densitometry. These data suggest that mechanical competence in the elderly is governed by strong regional variation, and that its loss in osteoporosis may not represent a strictly systemic process. [source] Measurement of Midfemoral Shaft Geometry: Repeatability and Accuracy Using Magnetic Resonance Imaging and Dual-Energy X-ray AbsorptiometryJOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2001Helen J. Woodhead Abstract Although macroscopic geometric architecture is an important determinant of bone strength, there is limited published information relating to the validation of the techniques used in its measurement. This study describes new techniques for assessing geometry at the midfemur using magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry (DXA) and examines both the repeatability and the accuracy of these and previously described DXA methods. Contiguous transverse MRI (Philips 1.5T) scans of the middle one-third femur were made in 13 subjects, 3 subjects with osteoporosis. Midpoint values for total width (TW), cortical width (CW), total cross-sectional area (TCSA), cortical cross-sectional area (CCSA), and volumes from reconstructed three-dimensional (3D) images (total volume [TV] and cortical volume [CVol]) were derived. Midpoint TW and CW also were determined using DXA (Lunar V3.6, lumbar software) by visual and automated edge detection analysis. Repeatability was assessed on scans made on two occasions and then analyzed twice by two independent observers (blinded), with intra- and interobserver repeatability expressed as the CV (CV ± SD). Accuracy was examined by comparing MRI and DXA measurements of venison bone (and Perspex phantom for MRI), against "gold standard" measures made by vernier caliper (width), photographic image digitization (area) and water displacement (volume). Agreement between methods was analyzed using mean differences (MD ± SD%). MRI CVs ranged from 0.5 ± 0.5% (TV) to 3.1 ± 3.1% (CW) for intraobserver and 0.55 ± 0.5% (TV) to 3.6 ± 3.6% (CW) for interobserver repeatability. DXA results ranged from 1.6 ± 1.5% (TW) to 4.4 ± 4.5% (CW) for intraobserver and 3.8 ± 3.8% (TW) to 8.3 ± 8.1% (CW) for interobserver variation. MRI accuracy was excellent for TV (3.3 ± 6.4%), CVol (3.5 ± 4.0%), TCSA (1.8 ± 2.6%), and CCSA (1.6 ± 4.2%) but not TW (4.1 ± 1.4%) or CW (16.4 ± 14.9%). DXA results were TW (6.8 ± 2.7%) and CW (16.4 ± 17.0%). MRI measures of geometric parameters of the midfemur are highly accurate and repeatable, even in osteoporosis. Both MRI and DXA techniques have limited value in determining cortical width. MRI may prove valuable in the assessment of surface-specific bone accrual and resorption responses to disease, therapy, and variations in mechanical loading. [source] Biochemical Markers as Predictors of Rates of Bone Loss After MenopauseJOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2000A. Rogers Abstract Biochemical markers of bone turnover may correlate with rates of bone loss in a group of postmenopausal women, but it is uncertain how useful they are in predicting rates of bone loss in the individual. The aim of this study was to determine the value of measurements of biochemical markers for the prediction of rates of bone loss in the individual. We studied 60 postmenopausal women (ages, 49,62 years), 43 of whom had gone through a natural menopause 1,20 years previously and 17 of whom had undergone hysterectomy 3,22 years ago. Lumbar spine bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DXA) over 2,4 years. Bone formation markers (bone-specific alkaline phosphatase [ibAP] and amino terminal of type I collagen [PINP] and osteocalcin [OC]) were measured in serum. Bone resorption markers (N-telopeptide of type 1 collagen [NTx] and immunoreactive free deoxypyridinoline [iFDpd]) were measured in urine and corrected for creatinine (Cr). Rates of bone loss were calculated as percent change per year. We found significant negative correlations (Spearman rank) between all measured biochemical markers and rate of change in bone density with r values ranging from ,0.35 to ,0.52. When markers and rates of bone loss were divided into tertiles, prediction of bone loss in an individual was poor (, < 0.2). There was an exponential relationship between rate of bone loss and years since menopause (YSM) in the 43 women having a natural menopause (r2 = 0.44; p = 0.008) indicating higher rates of loss in the early postmenopausal period. Levels of NTx, iFDpd, and PINP also showed a significant negative correlation with YSM. We conclude that there is a strong relationship between rates of spinal bone loss and levels of bone turnover markers. Although this is a small study, the results also suggest that using DXA measurements of the lumbar spine as the "gold standard," it is not possible to use biochemical markers to predict rate of bone loss in the individual. [source] Accuracy and precision of dual-energy X-ray absorptiometry for body composition measurements in rhesus monkeys*JOURNAL OF MEDICAL PRIMATOLOGY, Issue 2 2001Angela Black Accuracy of body composition measurements by dual-energy X-ray absorptiometry (DXA) was compared with direct chemical analysis in 10 adult rhesus monkeys. DXA was highly correlated (r-values >0.95) with direct analyses of body fat mass (FM), lean mass (LM) and lumbar spine bone mineral content (BMC). DXA measurements of total body BMC were not as strongly correlated (r-value=0.58) with total carcass ash content. DXA measurements of body FM, LM and lumbar spine BMC were not different from data obtained by direct analyses (P -values >0.30). In contrast, DXA determinations of total BMC (TBMC) averaged 15% less than total carcass ash measurements (P=0.002). In conclusion, this study confirms the accurate measurement of fat and lean tissue mass by DXA in rhesus monkeys. DXA also accurately measured lumbar spine BMC but underestimated total body BMC as compared with carcass ash determinations. [source] Zoledronic acid improves femoral head sphericity in a rat model of perthes diseaseJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2005David G. Little Abstract We hypothesized that the bisphosphonate zoledronic acid (ZA) could improve femoral head sphericity in Perthes disease by changing the balance between bone resorption and new bone formation. This study tests the effect of ZA in an established model of Perthes disease, the spontaneously hypertensive rat (SHR). One hundred and twenty 4-week old SHR rats were divided into three groups of 40: saline monthly, 0.015 mg/kg ZA weekly, or 0.05 mg/kg ZA monthly. At 15 weeks DXA measurements documented that femoral head BMD was increased by 18% in ZA weekly and 21% in ZA monthly compared to controls (p < 0.01). Femoral head sphericity in animals with osteonecrosis was improved in ZA-treatment groups (p < 0.01) as measured by epiphyseal quotient (EQ). The proportion of "flat" heads (EQ ± 0.40) was significantly reduced from 32% in saline-treated animals to 12% in weekly ZA and 3% in monthly ZA (p < 0.01). Histologically there was a similar prevalence of osteonecrosis in all groups. The prevalence of ossification delay was significantly reduced by ZA treatment (p < 0.01). Zoledronic acid favorably altered femoral head shape in this spontaneous model of osteonecrosis in growing rats. Translation of these results to Perthes disease could mean that deformity of the femoral head may be modified in children, perhaps reducing the need for surgical intervention in childhood and adult life. © 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Relationships between plasma leptin levels and body composition parameters measured by different methods in postmenopausal womenAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2003Toivo Jürimäe The aim of this study was to determine the effects of body composition measured by different methods with different measurement errors on fasting plasma leptin level in normal body mass and obese postmenopausal women. It was hypothesized that the relationship between plasma leptin concentration and body fat is higher using more sophisticated laboratory methods (dual energy X-ray absorptiometry, DXA) in comparison with field methods (bioelectrical impedance analysis, BIA, or skinfold thickness) for body fat measurement because of the greater precision of DXA measurements. Thirty-five postmenopausal (55,83 years of age) healthy Estonian women were divided into two groups: BMI < 27kg/m2 as non obese (n = 18) and BMI> 27kg/m2 as obese (n = 17). Body composition was determined using DXA (total body, arms, legs, and trunk fat percent, fat mass, and LBM) and BIA methods. Body fat percent was significantly higher using the DXA method. Subcutaneous adipose tissue distribution was determined by measuring nine skinfold thicknesses. Body fat distribution was defined as the ratio of waist-to-hip (WHR) and waist-to-thigh (WTR) circumferences. Leptin was determined by means of radioimmunoassays. Leptin concentration was not significantly different between groups (19.0 ± 13.3 and 21.5 ± 21.5ng/ml in non obese and obese groups, respectively). Body fat percent and fat weight measured by DXA or BIA methods and all measured skinfold thickness values, except biceps and abdominal, were higher in obese women. Body height did not correlate significantly with leptin concentrations. The relationships between leptin concentration were highest with body weight (r = 0.67) and BMI (r = 0.73) values in the obese group. All measured body fat parameters using DXA or BIA methods correlated significantly with plasma leptin concentration in the obese group. LBM did not influence the leptin concentration in postmenopausal women. Stepwise multiple regression analysis indicated that the body fat percent measured using the DXA method was highly related to plasma leptin concentration in the obese group (63.2%; R2 × 100). When absolute fat mass parameters were considered, leptin concentration was related to the mass of arms fat tissue in the obese group of women (62.3%). Body fat percent measured by BIA was highly related to plasma leptin concentration in the obese group (63.3%). Only biceps skinfold thickness was related to leptin concentration (22.5% and 58.9%, in the nonobese and obese groups, respectively) from the nine measured skinfold thicknesses. WHR and WTR did not reflect leptin concentration in different groups of postmenopausal women. It was concluded that different methods of body composition estimation generate different correlations with plasma leptin concentration. Body fat percent and especially fat mass measured by DXA are the main predictors relating to plasma leptin concentration in obese, but not in nonobese, postmenopausal women. In addition, fat mass in arms measured by DXA and biceps skinfold thickness were also highly related to leptin concentration. Am. J. Hum. Biol. 15:628,636, 2003. © 2003 Wiley-Liss, Inc. [source] | |||||||||||||