Dual-energy X-ray Absorptiometry Studies Research Articles

Different loss of BMD using uncemented press-fit and whole polyethylene cups fixed with cement: Repeated DXA studies in 96 hips randomized to 3 types of fixation

Background In cemented THA, aseptic loosening of the cup is more common than loosening of the stem, while periprosthetic osteolysis of the socket resulting in difficult reconstruction problems has emerged as the most significant problem with cementless cup fixation.Patients and methods 90 patients (96 hips) scheduled for THA were stratified in three groups according to the method of fixation of the acetabular component: acrylic bone cement with fluoride (Cemex-F), porous-coated press-fit cup with ceramic coating (Trilogy, uncemented) and acrylic cement with gentamicin (Palacos). All patients received the Spectron EF stem. Acetabular bone mineral density was measured with dual-energy X-ray absorptiometry (DXA) 1 week postoperatively, and after 12 and 24 months. The periprosthetic BMD was evaluated in 5 ROIs positioned around the acetabular component.Results In the uncemented sockets, the BMD had decreased proximally and medially to the cup after 2 years. The difference was significant in the proximal region as compared to the control group (Palacos). No difference was noted between the 2 groups with cemented components after 2 years. Stepwise linear regression analysis showed that loss of periprosthetic BMD in the proximal high-pressure region after 2 years increased with higher postoperative BMD and when the uncemented design had been used.Interpretation Contrary to previous studies of cemented stems, the use of fluoride cement did not influence the periprosthetic BMD 2 years after the examination. Increased loss of BMD with use of uncemented press-fit cups in the region in which osteolytic lesions are commonly found suggests that stress shielding may initiate the development of this complication. Longer follow-up will, however, be necessary to substantiate this hypothesis.

Development and Evaluation of a Vertebral Fracture Assessment Program Using IVA and Its Integration With Mobile DXA

Currently, it is unusual to combine evaluation for vertebral fracture with measurement of bone mineral density in clinical practice. Using Quantitative Morphometric Vertebral Analysis (Instant Vertebral Assessment [IVA]) in our existing Mobile Dual-Energy X-Ray Absorptiometry (DXA) Program, we implemented a testing procedure that examined 5 different IVA protocols focusing on clinical utility and cost. Using small-scale tests of change (PDSA cycles), data from the preceding cycle drives the development of the next cycle. In this article, we describe the process and rationale for selecting patients for the IVA study. In addition, we review the literature on vertebral fracture assessment using DXA and emphasize the clinical utility of point of service testing by providing the needed knowledge for best patient care by simultaneous DXA and IVA testing. The application of this new technology increased identification of the high-risk patient by 11%, with a nominal additional cost per DXA study of $14. This study provides a useful framework for the integration of IVA into a clinical DXA program.

Bone Assessment in Children

The newest version of whole body dual-energy X-ray absorptiometry (DXA) analysis software from Hologic (Discovery 12.1) is designed to enhance bone detection in smaller subjects. We re-analyzed 1127 pediatric scans (ages 1.8-18.5 yr) previously analyzed using software version 11.2. Regression analysis compared new and original results for bone area (BA), bone mineral content (BMC), bone mineral density (BMD), and DXA-derived body weight. Changes in total and regional bone results were compared with age, weight, and height. New results were highly correlated with original analyses (R2 > or = 0.9), but there were large differences at the individual subject level. The BA and BMC values increased in subjects less than 40 kg weight, resulting in a lower BMD. Original and new results were equivalent by about age 14 yr in both genders. Regional bone data showed the greatest changes in the legs. The newest software produces significant changes in bone values in subjects weighing less than 40 kg, compared with earlier versions. This effect increases with decreasing body weight. This will impact interpretation of longitudinal pediatric DXA studies, as well as existing pediatric whole body bone reference databases. Investigators must recognize which DXAsoftware version they are using, and which version produced any reference database they may use for comparison.

Correlation of Quantitative Heel Ultrasonography With Central Dual-Energy X-ray Absorptiometric Bone Mineral Density in Postmenopausal Women

In this study, we sought the proper cutoff level for quantitative ultrasonography (QUS) of the heel in identifying bone mineral density (BMD) categories as determined by dual-energy x-ray absorptiometry (DXA) in postmenopausal women. With the use of DXA, BMD categories of the lumbar spine and different areas of the left femur of 420 healthy women according to World Health Organization definitions were determined. Quantitative ultrasonography of the heel was also performed in each subject. Receiver operating characteristic curves were plotted, and sensitivity and specificity of QUS to diagnose osteoporosis were examined at different points to identify the best cutoff level. The diagnostic agreement between the two techniques in identifying osteoporosis was assessed with kappa scores. The kappa scores were 0.31 for the lumbar region and 0.5 for the femoral neck region. On the receiver operating characteristic study, a score of -1 was found to be the appropriate cutoff point for QUS studies, in which the sensitivity of QUS to diagnose BMD osteoporosis varied between 78% and 87.5% depending on the site of the DXA study. With the proposed cutoff point (-1), sensitivity and specificity of QUS in detecting osteoporosis at the lumbar spine were 83.9% and 51%, respectively, and at the femoral neck were 84% and 50%, respectively. Insufficient agreement between QUS and DXA led to uncertainty on expected BMD in people tested by QUS. The proposed cutoff value could achieve higher sensitivity but only by accepting higher rates of false-positive results.

Regional Body Fat Distribution in HIV-Infected Patients with Lipodystrophy

BackgroundObjective criteria for the assessment of patients with lipodystrophy syndrome in human immunodeficiency virus infection (LDHIV) have not emerged.MethodsWe compared regional body fat changes in 13 men with severe LDHIV...

SOY ISOFLAVONE TABLETS REDUCE OSTEOPOROSIS RISK FACTORS AND OBESITY IN MIDDLE‐AGED JAPANESE WOMEN

1. This study examines whether the supplementation of isoflavones (ISO) exerts beneficial effects on the bone mineral density (BMD) measured by dual energy X-ray absorptiometry (DEXA). 2. Eighty-one healthy Japanese pre- and postmenopausal women were randomly assigned to the following two groups taking either ISO (100 mg) tablets (ISO group) or placebo tablets (P group) containing vitamins C (25 mg) and E (5 mg) daily for 24 weeks in a double-blind placebo controlled parallel design. 3. Seventy women completed the intervention study (34 on ISO, 36 on P), only ISO group was proven to increase significantly BMD (P < 0.05 vs before) and to significantly decrease body fat measured by the DEXA (P < 0.0001 vs before and P < 0.05 vs P group), while BMI was maintained in ISO group despite significant BMI increase in P group. Thus, percent changes in BMI were significantly different between ISO and P groups (P < 0.05) 24 weeks after the intervention. 4. This prospective DEXA study confirmed a long-term ISO supplementation, 100 mg/day could not only prevent menopausal bone resorption but also increase BMD and decrease body fat concomitantly with BMI reduction. Enough ISO supplementation may contribute to the risk reduction of osteoporosis and obesity and, thus to overall health promotion in menopausal women.

Adults with partial growth hormone deficiency have an adverse body composition.

The current biochemical definition of severe GH deficiency (stimulated peak GH < 3 micro g/liter) provides good separation of GH-deficient (GHD) adults from normal subjects, although it may not account for all patients with impaired GH secretion. The vast majority of normal subjects display a peak GH level in excess of 7 micro g/liter in response to the insulin tolerance test. Using a peak GH response of 7 micro g/liter as an arbitrary upper limit, we investigated the effects of partial GH deficiency (GH insufficiency, GHI; peak GH response of 3-7 micro g/liter) on the body composition of hypopituitary adults. GHD adults (n = 30, peak GH < 3 micro g/liter) were of shorter stature than the controls. Body mass index was not significantly increased, but waist/hip ratio (0.885 vs. 0.818, P = 0.001) and skinfold thickness (78.2 vs. 59.6 mm, P = 0.003) were greater than control subjects. Bioimpedance analysis revealed these patients to have reduced lean body mass (LBM) (44.4 vs. 51.2 kg, P = 0.023) and increased fat mass (FM) (25.7 vs. 18.4 kg, P = 0.039). Dual-energy x-ray absorptiometry (DXA) analysis of body composition confirmed reduced LBM (43.6 vs. 50.6 kg, P = 0.010) and increased FM (26.0 vs. 19.2 kg, P = 0.015). The excess FM was observed to be primarily truncal in distribution. Similarly, GHI adults were of shorter stature but with increased waist/hip ratio (0.871 vs. 0.818, P = 0.006) and skinfold thickness (80.8 vs. 59.6 mm, P = 0.003), compared with controls. Bioimpedance analysis revealed a reduction in LBM (44.9 vs. 51.2 kg, P = 0.020). DXA studies confirmed the reduced LBM (45.0 vs. 50.6 kg, P = 0.041) and additionally noted an increase in percent FM (32.9 vs. 27.4%, P = 0.019). All measures of body composition in the GHI patients were intermediate between those of the controls and GHD patients. Serum leptin levels were significantly elevated in both the GHD (41.5 vs. 20.7 ng/ml, P = 0.009) and GHI (36.7 vs. 20.7 ng/ml, P = 0.022) adults, compared with healthy controls. The excess FM observed using DXA in the GHD and GHI adults equated to 6.5 kg (8%) and 3.5 kg (5.5%), respectively, relative to healthy controls. In summary, we have shown that adults with GHI have abnormalities of body composition characteristic of GHD. The degree of abnormality of body composition lies between that of healthy subjects and GHD adults and correlates with the IGF-I level. Any future trials of GH replacement in patients with GHI must await further studies to establish the exact impact of this relative deficiency on the broad spectrum of biological end points influenced by GH status.

Indications and Reporting for Dual-Energy X-Ray Absorptiometry

Abstract Although dual-energy X-ray absorptiometry (DXA) is widely used to measure bone mineral density (BMD), there are few guidelines regarding indications for testing in populations other than postmenopausal women or for reporting the results from DXA studies. At the 2003 Position Development Conference of the International Society for Clinical Densitometry, positions were developed to formalize indications for bone density testing and the components of a DXA report. Bone density testing is indicated for the following individuals: women 65 yr of age and older, postmenopausal women under age 65 yr with risk factors, men 70 yr of age and older, adults with fragility fracture, adults taking a medication or adults with a disease or condition associated with low bone mass or bone loss, any individual being treated for low bone mass to monitor treatment effect, and any individual in whom evidence of bone loss would affect treatment decisions. The DXA report should include patient identification and demographics, identification of the referring provider, indications for the test, an explanation of the technique, and abnormalities in performing the study. In addition, the report should include BMD values, the T-score and/or Z-score as appropriate, World Health Organization (WHO) classification for diagnosis, risk factors, and recommendations for follow-up.

Four-Year Gain in Bone Mineral in Girls With and Without Past Forearm Fractures: A DXA Study

We have previously shown that girls with a recent distal forearm fracture have weaker skeletons than girls who have never fractured. This could be a transient or persistent phenomenon. The present study was undertaken to determine whether the bone mineral content (BMC) of girls with previous distal forearm fractures remains lower 4 years postfracture or if catch-up gain has occurred. We report baseline and follow-up dual energy X-ray absorptiometry (DXA) results for 163 girls: 81 girls from the original control group who remained free of fracture (group 1) and 82 girls from the original group with distal forearm fractures (group 2). In data adjusted for bone area, height, weight, and pubertal status, group 2 girls had 3.5-8.5% less BMC at the total body, lumbar spine, ultradistal radius, and hip trochanter than group 1 at baseline, and 2.4-5.7% less BMC at these sites at follow-up. Even girls from group 2 who did not experience another fracture after baseline (n = 58) did not display greater BMC at follow-up compared with baseline values at any site, indicating that the decreased BMC at the time of fracture had persisted. In group 2, the relative gain in BMC after adjusting for the initial BMC and current bone area, height, weight, and pubertal stage was less than or similar to, but not greater than that of group 1 (ratio [95% CI]: total body, 0.985 [0.972-0.998]; lumbar spine, 0.961 [0.935-0.987]; ultradistal radius, 0.968 [0.939-0.998]; hip trochanter, 0.955 [0.923-0.988]; femoral neck, 0.981 [0.956-1.007]; and 33% radius 0.999 [0.977-1.021]). These findings indicate that girls with distal forearm fractures do not improve their gain of BMC. We conclude that girls who have sustained a distal forearm fracture maintain their lower BMC at most sites for at least 4 years.

Bone Densitometry: Applications and Limitations

Osteoporosis is clinically diagnosed in its advanced stages, usually following a fracture. Accurate, precise, and noninvasive skeletal assessment is now possible for early detection of osteoporosis at a preclinical stage. Currently, the gold standard in bone mass measurement and fracture prediction is dual energy X-ray absorptiometry (DEXA) of the hip and spine. Exponential increases in fracture risk have been observed with small decreases in bone mineral density. Bone mineral density BMD should be considered in conjunction with independent clinical risk factors for fracture, including: low body weight, history of postmenopausal fracture, family history of fracture, and poor neuromuscular function. The World Health Organization (WHO) diagnostic criteria for osteoporosis and osteopenia are appropriate for postmenopausal Caucasian women and are applicable to DEXA assessments at the hip, spine, or forearm. This review explores the relationship between BMD and fracture risk, the principles of bone densitometry interpretation, and the applications as well as the limitations of DEXA technology, and presents cases illustrating common errors seen in the interpretation of DEXA studies.

Effects of allogeneic bone marrow transplantation on recipient bone mineral density: A prospective study

Allogeneic bone marrow transplant (BMT) recipients have many known risk factors for developing decreased bone mineral density (BMD) after transplantation. We performed a prospective sequential evaluation of BMD in the lumbar spine and nondominant hip using dual-energy x-ray absorptiometry (DEXA) in a cohort of 47 adult patients (median age, 43 years) who were undergoing radiation-based BMT for hematologic malignancies. Baseline DEXA studies were performed before BMT and repeated at 3 to 4 months, 6 to 8 months, and 12 to 14 months after BMT. The majority of patients (60%) had been minimally treated with combination cytotoxic chemotherapy, having received no more than 1 treatment regimen before BMT. Graft-versus-host disease prophylaxis consisted of cyclosporine in combination with either methotrexate or prednisone, or both. Mean lumbar spine and hip BMD were normal before BMT (spine: 1.01 g/cm2, z score = 96%; hip: 0.86 g/cm2, z score = 100%) and gradually decreased (spine: 0.98 g/cm2, z score = 94%; hip: 0.76 g/cm2, z score = 91%) at 12 to 14 months. These declines were statistically significant (P < .006 and < .002 for lumbar spine; P < .001 and < .001 for hip). In addition, the sharpest decline occurred during the first 6 months after BMT and was more marked in the hip than the lumbar spine. These data suggest that BMT adversely affects BMD in this patient population. Biol Blood Marrow Transplant 2000;6(3A):344-51.

Assessing body composition and changes in body composition. Another look at dual-energy X-ray absorptiometry.

Dual-energy X-ray absorptiometry (DXA) is selected with increasing frequency as a method for both assessing body composition and measuring the changes in body composition. Issues have been raised about hydration, software version, hardware (fan beam vs. pencil beam), and the subject population in relation to the validity of DXA-derived estimates of body composition. This paper reviews validation studies of DXA to assess the impact of recent developments in its technology. Studies by Prior et al., Kohrt et al., Salamone et al., Going et al., and Pietrobelli et al. demonstrate the effectiveness of DXA estimates of changes in body composition. By contrast, Clasey et al., Nelson et al., and Friedl et al. found limitations in DXA estimates of body composition and its changes. These contradictory conclusions were explored for threats to internal validity in each research study. From this analysis, two validation guidelines are recommended for use when evaluating estimates of body composition. When multicomponent models are used, it is essential that estimates of body water as a fraction of fat-free mass fall in the expected range (71 to 75%) and have a relatively small standard deviation (2 to 3%). For measuring changes in body composition, DXA estimates of total body mass must accurately reflect both baseline and posttreatment scale body weight estimates. Failure to meet these guidelines threatens the internal validity of the study and raises the likelihood of methodological discrepancies. Applying these criteria to DXA studies of body composition under review accounts for much of the contradictory conclusions among investigations.

Pediatric Bone Densitometry: Technical Issues

Equipment and software used for dual energy x-ray absorptiometry (DXA) was developed for adults. As use of the method grows in pediatrics, understanding technical issues is important for those performing and interpreting DXA studies in infants, children, and adolescents. Detection of very low bone mineral density requires alteration of automated scan techniques. Normal values based on chronologic age have been published. The Z score becomes the more meaningful statistic as opposed to the T score used in reporting adult DXA measurement of bone mineral density.

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.

Effect of Chronic Maternal Calcium (Ca) Supplementation on Fetal Bone Mineralization (FBM). † 1535

Pregnancy is a time of physiologic stress on Ca homeostasis but there has been no systematic study on the effect of maternal Ca intake on FBM. We tested the hypothesis that maternal Ca supplementation increases FBM as indicated by dual energy X-ray absorptiometry (DXA) measurements of the neonate. Two hundred eighty-nine women enrolled in a randomized trial of Ca supplementation during pregnancy were approached to participate in a study of FBM; 276 agreed. The women had been randomized to receive 2-g elemental Ca or placebo tablets daily from 13-21 wks gestation until delivery. At each prenatal visit compliance was determined by pill counts. The treatment grp received an average of 1284 mg supplemental Ca/d. All mothers were provided with the same prenatal vitamin supplement. There were no significant differences in maternal dietary Ca, protein and energy intake between grps based on the average of 24-hr recalls conducted at randomization and at 32-33 wks gestation. There was also no significant difference between grps in maternal body mass index and wt gain during pregnancy. Eight neonates were not studied because of 2 deaths, 5 technical problems with DXA and learly discharge. Twelve infants had delayed DXA studies beyond one week after birth because of illness. Of the remaining 256 infants (128/grp), DXA measurements were performed by the same operator at 1.75 (mean) ± 0.1 (SEM) d. Scan acquisition used Hologic 1000/W densitometer (Hologic Inc., Waltham, MA) and infant platform. Quality control scans using manufacturer supplied phantom showed a long term (>3 yrs) CV of<0.5%. Only scans without movement artifact were analyzed using software(v5.64 for total body and v4.57Q for spine) developed in conjunction with the manufacturer. General linear modeling showed that the mean total body bone mineral content (BMC) and lumbar spine BMC were significantly (p<0.05) higher in the treatment grp (13.4% and 14.6%, respectively) at the lowest quintile of maternal dietary Ca intake (mean 504 [treatment] vs 555 [placebo] mg/d). The effect of Ca supplementation on FBM was not significantly different at the highest quintile of dietary Ca intake. We conclude that FBM can be significantly improved by Ca supplementation at low maternal dietary Ca intake.

Changing femoral geometry in growing girls: a cross-sectional DEXA study.

In elderly women, a long hip axis length has been shown to increase the risk of hip fracture. However, to date, few measurements of hip geometry have been reported in children and adolescents. The present cross-sectional dual-energy X-ray absorptiometry (DEXA) study of 200 girls aged 3-16 years was undertaken to determine at what age adult hip geometry is achieved and to examine possible influences of anthropometry and body composition on the development of femur axis length (FAL) and femur width (FW) during growth. Adult values for FAL and FW were achieved by age 15 years. Age, height, lean tissue mass, total body bone mineral content (BMC), weight, FW, neck of femur bone mineral density (BMD), and fat were each strongly associated with FAL (p < 0.001), the highest correlations being with age (r = 0.917) and height (r = 0.906). However, after adjusting for age and height, only lean tissue mass, weight, and fat mass remained significantly associated with FAL, suggesting that bone mineral accrual does not influence variance in FAL. Our results also suggested that fat mass and weight per se tended to have greater influence on FW than on FAL in age- and height-adjusted data. Twin studies indicate that 20% of adult hip axis length is associated with environmental factors. We therefore conclude that any environmental effects of physical activity or nutrition on hip geometry must occur before early teen-age years.

Patient doses in bone mineral densitometry

Procedures were developed to compute effective dose equivalent (H(E)) values for patients undergoing bone mineral densitometry (BMD) measurements such as dual energy X-ray absorptiometry (DEXA) and quantitative computed tomography (QCT). Representative values of H(E) were determined for patients undergoing each type of BMD procedure. Typical DEXA measurements are associated with an H(E) of about 2.5 microSv. For QCT, the values of H(E) are 300 microSv for single energy techniques and 1 mSv for dual energy techniques, respectively. By comparison, a single well collimated abdominal X-ray examination often taken in conjunction with DEXA studies results in an H(E) of about 100 microSv. BMD patient doses are at the lower end of the exposure range encountered in diagnostic radiology. As a result, radiation dose is not a primary factor in choosing the method for BMD determination.

Skeletal muscle mass: evaluation of neutron activation and dual-energy X-ray absorptiometry methods.

Although skeletal muscle (SM) is a major body component, whole body measurement methods remain limited and inadequately investigated. The aim of the present study was to evaluate the Burkinshaw in vivo neutron activation analysis (IVNA)-whole body 40K-counting and dual-energy X-ray absorptiometry (DXA) methods of estimating SM by comparison to adipose tissue-free SM measured using multiscan computerized axial tomography (CT). In the Burkinshaw method the potassium-to-nitrogen ratios of SM and non-SM lean tissue are assumed constant; in the DXA method the ratio of appendicular SM to total SM is assumed constant at 0.75. Seventeen healthy men [77.5 +/- 13.8 (SD) kg body wt] and eight men with acquired immunodeficiency syndrome (AIDS; 65.5 +/- 7.6 kg) completed CT, IVNA, and DXA studies. SM measured by CT was 34.4 +/- 6.2 kg for the healthy subjects and 27.2 +/- 4.0 kg for the AIDS patients. Compared with CT, the Burkinshaw method underestimated SM by an average of 6.9 kg (20.1%, P = 0.0001) and 6.3 kg (23.2%, P = 0.01) in the healthy men and the men with AIDS, respectively. The DXA method minimally overestimated SM in both groups (2.0 kg and 5.8% in healthy men, P = 0.001; 1.4 kg and 5.1% in men with AIDS, P = 0.16). This overestimate could be explained by a higher actual than assumed ratio of DXA-measured appendicular SM to total body SM (actual = 0.79 +/- 0.05, assumed = 0.75). The current study results reveal that large errors are present in the Burkinshaw SM method and that substantial refinements in the models that form the basis of this IVNA approach are needed. The model on which the DXA-SM method is based also needs further minor refinements, but this is a promising in vivo approach because of less radiation exposure and lower cost than the IVNA and CT methods.

Quality control of DXA instruments in multicenter trials.

Dual-energy X-ray absorptiometry (DXA) has become the measurement of choice for multicenter trials with bone density endpoints. When performing DXA measurements with several different systems, it is important to implement a quality assurance program to guarantee that any observed density changes are real and not due to machine and/or operator variability. In this study, we present a series of procedures based on phantom measurements designed to monitor DXA instrument stability. Techniques for longitudinal evaluation of machine performance and cross-calibration of instruments are described. These procedures are then demonstrated using quality assurance data collected from a number of different DXA scanners. Together these methods provide a defined approach to instrument quality control. Though based primarily on the use of spinal phantoms, these procedures can be generalized for use in any multicenter DXA study.