Bone mineral density measured by dual-energy X-ray absorptiometry in healthy finnish women

Summary A cross-sectional study of 351 healthy Finnish women aged 20–76 years was done to establish reference values of bone mineral density (BMD) using dual-energy X-ray absorptiometry (DEXA). The effects of age and of several physical and lifestyle factors on BMD of the lumbar spine and proximal femur (femoral neck, trochanter, and Ward's triangle area) were investigated. Altogether 58 women were excluded from the final analysis due to significant spinal osteoarthritis or other diseases or drugs known to influence calcium or bone metabolism. The precision of the method was 0.9, 1.2, 2.7, and 2.4% in the lumbar, femoral neck, Ward's triangle and trochanter area, respectively. Lumbar BMD was increased by 30% (P<0.001) in 15 patients with osteoarthritis (21% of women 50 years or older), but it was apparently unaffected in 5 cases with aortic calcification. Except for the trochanter area, BMD diminished along with age, and this was significant after the menopause. The peak of mean BMD was observed at the age of 31–35 years in the spine and at the age of 20–25 years in the femoral neck and Ward's triangle. BMD was in a positive relationship to weight both in premenopausal and postmenopausal women and to the use of oral contraceptives in premenopausal women and to that of estrogen replacement therapy in postmenopausal women. Labors and pregnancies had a weak positive effect on BMD in premenopausal women. As compared with nonusers premenopausal women who had used alcohol showed a slightly decreased BMD of Ward's triangle. In postmenopausal women there was a positive correlation between alcohol intake and BMD.     

Bone mineral density measured by dual X-ray absorptiometry in Spanish patients with insulin-dependent diabetes mellitus

Previous studies suggest that low bone mass is a potential complication of insulin-dependent diabetes mellitus. Nevertheless, the factors that influence diabetic osteopenia are not well established. In order to evaluate the prevalence and magnitude of diabetic osteopenia and its association with clinical and metabolic variables, we studied 94 consecutive patients with insulin-dependent diabetes mellitus. Their age ranged from 20 to 56 years and duration of diabetes varied from 1 to 35 years. Bone mineral density (BMD) was measured by dual X-ray absorptiometry at lumbar spine and proximal femur and the values were expressed as z-score. The presence and extent of microvascular complications, degree of metabolic control, and other risk factors for osteoporosis were recorded and some biochemical markers of bone metabolism were assessed. Diabetic patients showed reduced BMD in all sites (lumbar spine: −0.89±1.21; femoral neck: −0.99±1.24; Ward triangle; −1.05±1.24;P<0.0001). Of the 94 patients 19.1% met diagnostic criteria for osteoporosis. BMD correlated with body mass index in all sites and with the duration of disease in Ward's triangle. Presence and extent of diabetic complications were associated with lower BMD, as was smoking. No correlation was found between BMD and biochemical markers. In conclusion, osteopenia is a common complication in patients with insulin-dependent diabetes mellitus. Microvascular complications are a critical point in the progression of diabetic osteopenia. Other risk factors for osteoporosis (nutritional status and smoking) must be taken into account. Preliminary results partially presented at the EASD Meeting in Prague, Czechoslovakia, September 1992     

High bone mineral density is associated with high body mass index

Summary  High BMD is an infrequent finding. In this retrospective cohort study of women 50 years and older, we documented a strong association between high BMD and high BMI. Introduction  High bone mineral density (BMD) has been associated with genetic disorders and a variety of dietary, endocrine, metabolic, infectious and neoplastic diseases that in many cases warrant medical attention. Since body mass index (BMI) is closely correlated with BMD, we sought to explore the relationship between these two parameters in older women. Methods  We conducted a retrospective clinical cohort study of 16,500 women 50 years and older who underwent baseline BMD testing between May 1998 and October 2002. Mean T-scores and Z-scores, and the proportions of women with high BMD (T-score +2.5 or greater, Z-score +2.0 or greater), were assessed according to BMI category. Results  Higher BMI category was associated with higher mean T-scores and Z-scores at all sites (P < 0.001). The proportion of women with high BMD increased with each BMI category (P for trend <0.05). In women with a lumbar spine T-score of +2.5 or more, 43.5% were obese with BMI > 30 kg/m² (55.6% for the femoral neck and 73.1% for the total hip). For women with a lumbar spine Z-score of +2.0 or more, 37.2% were obese (42.0% for the femoral neck and 50.9% for the total hip). There was no evidence of a paradoxical increase in fracture rates in women with high BMD. Conclusions  High BMD is closely associated with elevated BMI in women. This should be taken into consideration prior to initiating extensive investigations for rare pathologies. This study was supported in part by an unrestricted educational grant from the CHAR/GE Healthcare Development Awards Programme.     

体成分对男性2型糖尿病患者骨密度的影响

目的 应用双能X线骨密度仪（DXA）探讨体成分对男性2型糖尿病患者骨密度的影响。方法 选择年龄50～60岁在我科住院的男性2型糖尿病患者107例,分为正常体重组、超重组和肥胖组,分别测定其身高、体重,计算体重指数（BMI）,利用全自动生化分析仪测定血糖、血脂,高压液相色谱法测定糖化血红蛋白（HbA1c）,采用双能Ｘ线骨密度仪测定腰椎、左股骨大转子骨密度（BMD）及体成分,并进行统计学分析。结果 3组男性2型糖尿病患者腰椎BMD分别为1.12±0.05,1.21±0.07,1.36±0.09,左股骨大转子BMD分别1.12±0.06,1.22±0.08,1.41±0.08,与骨密度呈正相关;全身各部位肌肉含量与骨密度成正相关,且大腿＞上肢＞躯干;不同部位脂肪含量对骨密度的影响是不同的,其中上肢脂肪和大腿脂肪与骨密度成正相关,而躯干脂肪与骨密度成负相关;年龄、糖化血红蛋白、血脂对男性2型糖尿病患者骨密度无明显影响,而体重指数、肌肉含量及脂肪含量影响明显。结论 体重指数、肌肉含量和脂肪含量对男性2型糖尿病患者骨密度有直接影响。男性2型糖尿病患者加强锻炼,减少腹部脂肪含量,增加四肢肌肉含量,可以预防骨质疏松症的发生。     

A comparison of two dual-energy X-ray absorptiometry systems for spinal bone mineral measurement

Summary Two dual-energy X-ray absorptiometry (DEXA) systems—the Hologic QDR-1000 and the Norland XR-26 bone densitometers—were evaluated in terms of precision, accuracy, linearity of response, X-ray exposure, and correlation of in vivo spinal measurements. In vitro precision and accuracy studies were performed using the Hologic anthropomorphic spine phantom; linearity of response was determined with increasing thicknesses of aluminum slabs and concentrations of Tums E-X in a constant-level water bath. Both systems were comparable in precision, achieving coefficients of variation (CVs) of less than 1% in bone mineral content (BMC, g), bone area (cm²), and bone mineral density (BMD, g/cm²). Both were accurate in their determination of BMC, bone area, and BMD with reference to the Hologic spine phantom. Both systems also showed good BMC and BMD linearity of response. Measured X-ray skin surface exposures for the Hologic and the Norland systems were 3.11 and 3.02 mR, respectively. In vivo spinal measurements (n=65) on the systems were highly correlated (BMC: r=0.993, SEE=1.770 g; area: r=0.984, SEE=1.713 cm²; BMD: r=0.990, SEE=0.028 g/cm²). In conclusion, both systems are comparable in terms of precision, accuracy, linearity of response, and exposure efficiency.     

Women at risk for developing osteoporosis: Determination by total body neutron activation analysis and photon absorptiometry

Summary With stepwise multiple logistic regression (MLR), probabilistic classification equations were developed to identify asymptomatic women who are at risk for development of fracture of the spine. Clinically normal women with low TBCa/ ratios can be classified as at risk for osteoporosis prior to their developing spinal compression fractures. With receiver operating characteristic (ROC) analysis, it was possible to verify the accuracy of the MLR model to discriminate “normal” women at risk, with high sensitivity and specificity. With the MLR model, discrimination of osteoporotic women (50–59 years) was made correctly for 86.2% of the total osteoporotic subjects with the TBCa data. Similar models were derived from the photon absorptiometry data. From the spinal density (BD_s) data, correct classification in the 50–59 year group was 55.6% of the total osteoporosis subjects; from the radius density (BMC_r) data, the corresponding value was 31%. The highest probability of identifying osteoporosis in all age categories was, therefore, on the basis of TBCa data. Similar, but less accurate discrimination was achieved with the BD_s and BMC_r data. These conclusions were confirmed by the application of receiver operating characteristic (ROC) analysis. Correct identification of the population at risk permits the timely and efficient application of therapeutic programs prior to onset of fracture. In a serial study of 104 perimenopausal women, for example, it was possible to determine theP value for individuals measured annually over a 3–10 year period and thus to predict normal individuals at risk for developing osteoporosis each year.     

体重体成分与骨密度的关系

为了研究体成分与骨密度（ＢＭＤ）之间的关系，因体重与ＢＭＤ显著相关，体成分各个组成相加等于体重，而体成分与ＢＭＤ的关系仍不清楚。方法随机选取２０６名１６～５２岁健康的男女性汉族人，用双能Ｘ射线吸收法（ＤＸＡ）测量ＢＭＤ与体成分，进行ＢＭＤ与体重，体成分的多元线性回归分析。结果体重，瘦组织（ＬＴＭ）与男女性的ＢＭＤ显著正相关，脂肪组织（ＦＴＭ）仅对女性全身，腰椎ＢＭＤ起显著性作用。结论影响男女性ＢＭＤ的体成分中，ＬＴＭ是主要因素，ＦＴＭ仅对女性ＢＭＤ有影响。本文较全面地研究了体成分与ＢＭＤ的关系。     

Bone mineral density of the distal femur following uncemented total knee arthroplasty: a two-year follow-up of 11 knees using dual energy X-ray absorptiometry

Abstract In a prospective study, we evaluated the adaptive bone remodelling pattern of the distal femur using dual energy X-ray absorptiometry (DEXA) after total knee arthroplasty (TKA). Eleven patients underwent TKA with insertion of an Interax total knee system (Howmedica) because of primary osteoarthrosis of the knee. All patients received an uncemented femoral component with an uncoated cast-mesh ingrowth surface. The components had a 20-mm long central peg placed anteriorly just behind the anterior flange. DEXA scans were performed postoperatively at 2 weeks and at 3, 6, 12 and 24 months in the mediolateral plane of the distal femur and in the anteroposterior plane of the distal tibia and fibula. Compared to the immediate 2-week postoperative bone mineral density (BMD) value, we found no significant changes in BMD in 4 regions of interest (ROI) in the distal femur during the 2-year follow-up at 3 months. A temporary but significant decrease in BMD of 11.2% (95% CL, -17.3% to -5.0%) was observed in the most distal ROI just posterior to the fixation peg. Bone mineral content (BMC) of the distal tibia and fibula showed no significant changes in the operated and contralateral legs during the follow-up. The adaptive bone remodelling of the distal femur after TKA using an uncemented femoral component not previously examined by DEXA induced only a very limited and temporary loss of bone mineral.     

Influence of patient's weight on dual-photon absorptiometry and dual-energy X-ray absorptiometry measurements of bone mineral density

Lumbar spine bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) (Hologic QDR 1000) and by¹⁵³Gd dual-photon absorptiometry (DPA) (Novo Lab 22a) in 120 postmenopausal women. Though a high correlation existed between the two techniques, the ratio between DXA and DPA values was not constant. Using DXA we observed a higher dependence of BMD on weight than in the DPA measurements. To investigate the different behaviour of DXA and DPA machines with weight, we analysed the effects of increasing thickness of soft tissue equivalents on the BMD of the Hologic spine phantom and on the BMD equivalent of an aluminium standard tube. Increasing tissue-equivalent thickness caused the phantom BMD measured by DPA to decrease significantly but had not effect on the DXA measurements. The different behaviour of DPA and DXA equipment with regard to the phantoms could account for the differences observed in the relations between BMD and weight in the patients. Using multiple regression we studied the influence of weight and body mass index on the relation between BMD measured by the two techniques. The introduction of either of these variables into the regression resulted in an improvement of the prediction of the DXA values from the DPA values. However, the residual standard error of the estimate was still higher than the combined precision errors of the two methods, so that no simple relation allows a conversion of BMD_DPA into BMD_DXA. Our results confirm that BMD is positively correlated with weight in postmenopausal women; the influence of weight on BMD is blunted when the Novo Lab 22a DPA machine is used for measuring bone mineral.     

Effective dose values in bone mineral measurements by photon absorptiometry and computed tomography

A high degree of uncertainty and irritation predominates in the assessment and comparison of radiation dose values resulting from measurements of bone mineral density of the lumbar spine by photon absorptiometry and X-ray computed tomography. The skin dose values which are usually given in the literature are of limited relevance because the size of the irradiated volumes, the relative sensitivity of the affected organs and the radiation energies are not taken into account. The concept of effective dose, sometimes called whole-body equivalent dose, has to be applied. A detailed analysis results in an effective dose value of about 1 µSv for absorptiometry and about 30 µSv for computed tomography when low kV and mAs values are used. Lateral localizer radiographs, which are necessary for slice selection in CT, mean an additional dose of 30 µSv. Lateral X-ray films of the spine which are frequently taken in combination with absorptiometry result in a dose of 700 µSv or more. The concept of effective dose, the basic data and assumptions used in its assessment and a comparison with other dose burdens (for example the natural background radiation, of typically 2400 µSv per year) are discussed in detail.     

Comparative assessment of bone mineral density of the forearm using single photon and dual X-ray absorptiometry

Summary Forearm bone mineral density (BMD) was measured at proximal and distal sites by ¹²⁵I single photon absorptiometry (SPA) and by dual energy X-ray absorptiometry (DXA) in 67 consecutive subjects, aged 18–75 years. Correlations and regression equations between these two techniques were determined. All forearm measurements were significantly correlated with each other (r=0.599–0.926; P0.0001). Although SPA and DXA correct for fat in different ways, we found similar correlation and regression equations in women with body mass index measurements above and below the mean. In addition, forearm measurements by both techniques were moderately correlated with vertebral spine and hip BMD. We conclude that overall, SPA forearm measurements in a population can be calibrated to DXA measurements if necessary, and that DXA forearm measurements are as predictive of the remainder of the skeleton as SPA measurements.     

Single X-ray absorptiometry of the forearm: Precision,correlation, and reference data

The performance of a single X-ray absorptiometry (SXA) device incorporating an X-ray tube as a photon source was evaluated with respect to precision in vivo and in vitro, scan time, image quality, and correlation with an existing dual energy X-ray absorptiometry (DXA) device. SXA precision in vivo, expressed as a coefficient of variation (CV), was 0.66% for bone mineral content (BMC) and 1.05% for bone mineral density (BMD). Precision in vitro, based on 78 BMC measurements of a forearm phantom over 195 days, was 0.53%. Correlation with DXA at the 8 mm distal forearm site was high (r=0.97 for BMC and r=0.96 for BMD). A preliminary SXA reference database composed of 151 healthy Caucasian American women was developed to facilitate the interpretation of patient measurements. SXA scan time was 4 minutes and delivered a radiation exposure of 1.68 mrem. SXA image quality and spatial resolution were superior to SPA and comparable to DXA.     

Vertebral bone mineral density measured laterally by dual-energy X-ray absorptiometry

The bone mineral density (BMD) of lumbar vertebrae in the anteroposterior (AP) view may be overestimated in osteoarthritis or with aortic calcification, which are common in elderly. Furthermore, the risk of spinal crush fracture should be more closely related inversely to the BMD of the vertebral body than to that of the posterior arch. Therefore, we measured BMD of lumbar vertebrae in lateral (LAT) view (L2–L3), using a standard dual-energy X-ray absorptiometer (DEXA), thus eliminating most of the posterior spinal elements. The precision of BMD LAT measurement was determined both in vitro and in healthy volunteers. Then, we compared the capability of BMD LAT and BMD AP scans for monitoring bone loss related to age and for discriminating the BMD of postmenopausal women with nontraumatic vertebral fractures from that of young subjects. In vitro, when a spine phantom was placed in lateral position in the middle of 26 cm of water in order to simulate both soft-tissue thickness and X-ray source remoteness, the coefficient of variation (CV) of six repeated determinations of BMD was 1.0%. In vivo, the CV of paired BMD LAT measurements obtained in 20 healthy volunteers after repositioning was 2.8%. The age-related difference between a peak bone mass group estimated in a group of 27 healthy women aged 20 to 35 years and a group of 50 women aged 60 to 75 years, in whom neither vertebral fracture nor osteoporosis risk factors could be detected, were 21.7% and 37.6% in AP and LAT view, respectively. An arbitrary BMD fracture threshold was defined in AP and LAT views as the 90th percentile of the BMD value of a group of 22 osteoporotic women with vertebral fractures. The distribution of BMD AP and LAT above and below this threshold in 169 consecutively screened women without vertebral fracture was then analysed. In both AP and LAT views, 39.1% and 31.3% had BMD values above and below this threshold, respectively. Of the remaining, 16.0% had a BMD below this threshold only in AP and 13.6% only in LAT view. Thus, if BMD LAT was a better reflection of vertebral body bone mass than BMD AP, and thereby a better predictor of the resistance to crush fracture, our results would suggest that only the use of the standard AP view could under- or overestimate spinal fracture risk in about 30% of women screened for osteoporosis. In conclusion, our results indicate that BMD measurement in lateral view is feasible with a standard DEXA instrument. This mode of scanning, besides overcoming artefacts due to osteoarthritis of the posterior arch and aortic calcifications, appears to provide a greater sensitivity for assessing bone mass loss of the vertebral body than the standard anteroposterior scan.     

Body composition in children with renal disease: use of dual energy X-ray absorptiometry

Dual energy X-ray absorptiometry (DEXA) is a non-invasive accurate method which estimates bone mineral content and density (BMD), as well as fat (FM) and lean (LM) body mass. This method was used in control children in order to establish normal values for BMD of lumbar spine and whole body composition {logistic curves, general equation E=k+K/[1+exp(-A)]}. In children with chronic renal failure (CRF), LM correlated with the urinary excretion of creatinine (r=0.97,P=0.0001) independently from glomerular filtration rate. However, the assessment of LM by DEXA must take into account the hydration level, since there is a positive correlation between fluid loss and reduction in LM in children on hemodialysis (r=0.98,P=0.0001). After renal transplantation, a significant loss of BMD (median –9.2%), was observed at 6 months which returned to 95% of pretransplant values by the end of the 1 st year. Maximal changes in LM and FM occurred during the first 3 months (–7.8% and +7.2%, respectively) and may be due to steroids; these should be influenced by physical activity since FM correlated inversely with maximal oxygen consumption (r=0.69P=0.0001). Recombinant growth hormone treatment could also increase LM and decrease FM, as shown in 9 patients. DEXA appears therefore to be a reliable method for evaluating therapeutic interventions affecting nutritional status in children with CRF.     

Bone mineral density in children after renal transplantation

A successful kidney transplantation (Tx) offers good quality of life for children suffering from chronic renal failure. However, some metabolic abnormalities may not be corrected and may persist after Tx despite good graft function. Post-Tx bone disease seems to be a universal finding in adult Tx recipients, and is most probably related to steroids. Reports on bone mineral density (BMD) in children after renal Tx are not uniform. Recent studies suggest that BMD is normal when corrected for height. However, longitudinal studies show a transient decrease in BMD in the early post-Tx period. These controversial results raise the issue of the correct interpretation of dual-energy X-ray absorptiometry in children with stunted growth. Etiopathogenetic factors of the decreased BMD, preventive and thera- peutic measures are discussed. In conclusion, the results of dual energy X-ray absorptiometry should be interpreted with caution, especially in children with disturbed growth. Received: 3 May 1999 / Revised: 16 January 2000 / Accepted: 23 January 2000     

Bone mineral density of the spine in normal Japanese subjects using dual-energy X-ray absorptiometry: Effect of obesity and menopausal status

Summary Bone mineral density (BMD) of the lumbar spine was measured to determine normal Japanese values and to examine the effect of obesity and menopausal status on BMD. Normal Japanese subjects (N=1,296, 1,048 women and 248 men) were examined using dual-energy X-ray absorptiometry. BMD for men peaked between age 20 and 29. For women, there was abrupt bone loss after age 50. Obese women within the same age bracket had a higher BMD than thin women after age 40–49. We determined that BMD began to decline during the irregular menstruation period before the onset of menopause. We conclude that there is a positive correlation between obesity and BMD, particularly in postmenopausal women. In addition, we found that bone loss related to menopause begins during the irregular menstruation period before menopause.     

A comparison of quantitative dual-energy radiographic absorptiometry and dual photon absorptiometry of the lumbar spine in postmenopausal women

Summary Noninvasive bone densitometry is an important aspect in the detection and management of osteoporosis and other forms of metabolic disease of calcified tissue. A system using quantitative dual-energy digital projection radiography (QDR) of the lumbar spine was systematically tested against dual-photon absorptiometry (DPA) of the lumbar spine in 131 women over 55 years of age and free from major risk factors for osteoporosis. All subjects were scanned by both QDR and DPA under the same conditions. Measurements for a given subject were made within 15 minutes of each other. Bone mineral densities (BMD) were determined for four individual levels in the lumbar spine (L1-L4). Regression equations for BMD vs. age, height, and weight were calculated. The results of this investigation indicate that DPA- and QDR-derived BMD values are comparable. BMD values derived by QDR were consistently lower than those obtained by DPA (DPA=1.115 QDR+0.137, r=0.942). The L2 lumbar region was the most strongly correlated determination.     

Bone loss around failed femoral implant measured by dual-energy X-ray absorptiometry

Periprosthetic bone mineral density (BMD) and its changes after primary total hip arthroplasty (THA) have been studied extensively, but quantitative data on BMD around loosened prostheses are still lacking. In this study, using dual-energy X-ray absorptiometry (DXA), we determined periprosthetic BMD in 19 patients with failed primary THA. There was a decrease in BMD (8.8%–25.5%) in every Gruen zone as compared with the patient's non-operated (control) side. Although the bone loss was most significant in the proximal femur, as in primary THA, the pattern of bone loss around the failed THA differred from the typical remodeling seen after successful THA. We suggest that quantitation of bone mass around the failed femoral stem is possible. Remarkable generalized bone loss around the stem is associated with a loosened prosthesis. Received: November 12, 1999 / Accepted: December 24, 1999     

Determination of bone mineral density by dual x-ray absorptiometry in patients with uncemented total hip arthroplasty.

Bone remodeling is an expected sequela with total hip arthroplasty (THA). Although there are several methods of estimating bone response in THA patients from radiographs, there are no accurate and generally accepted methods for quantitative determinations in vivo. In this study, we describe an application of dual x-ray absorptiometry (DXA) for measuring bone mineral content and bone mineral density in the proximal femur following THA. DXA is a noninvasive technique with minimal radiation exposure (< 5 mrem). Various aspects of measurement error (accuracy and reliability) of this application of DXA were determined in a series of studies reported here. Accuracy error (how similar are the measured and actual values) was < 1% determined in bone phantoms of four densities. Precision error (how reproducible are the measurements) was also < 1% at all four densities in the phantoms and was only slightly elevated (0.9-1.5%) in repeated measurements of implanted cadaver femora. Precision error in vivo, determined both from multiple replicates on five patients and from duplicate scans on 30 patients, was further elevated but remained < 5%. Contributions to precision error, rotation of the leg, and interoperator variability were assessed; none was found to elevate precision error appreciably. We suggest that DXA is a feasible method for quantifying bone response following THA, and will allow discrimination of small changes (> 5%) not previously measurable.     

股骨近端骨密度的测量

双能X线骨密度仪检测骨密度是诊断骨质疏松症和疗效随访的金标准,特别是髋部骨密度的测量对于骨折的预测尤其测定部位本身骨折的预测作用较大.由于脊柱部位的骨密度测量值易受到脊柱退行性疾病的病理改变如退行性侧凸、骨赘增生、腰椎间盘突出等影响,测量的准确性下降.因而近年来欧美国家临床试验也好或者骨质疏松诊疗也好,大都以股骨近端的BMD测定为标准.本文就股骨近端解剖特点、骨密度测量的意义、方法以及测量的注意点作一个综述,以期帮助临床医生或技术员全面评估股骨近端骨密度测定的意义.