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PubMed1997

Bone densitometry: current status and future prospects.

Over the past decade, growing awareness of the impact of osteoporosis on the elderly population and the consequent costs of healthcare have stimulated development of new treatments to prevent fractures, together with new imaging technologies to assist in diagnosis. With its ability to perform high-precision measurements of bone mineral density (BMD) in the spine and hip, dual X-ray absorptiometry (DXA) is well suited to meet this latter need. However, there is continuing interest in smaller, less expensive, systems for assessing the peripheral skeleton. These include peripheral DXA scanning of the distal forearm and a variety of devices for performing quantitative ultrasound (QUS) measurements of broad-band ultrasonic attenuation (BUA) and speed of sound (SOS) in bone. Pivotal to all these developments is the demonstration in prospective studies that new technologies can reliably identify patients at risk of osteoporotic fractures. Whether DXA technology can meet the anticipated need for wider provision of diagnostic services is uncertain at present. The likely alternative is bone ultrasound. Although QUS technology is substantially cheaper than DXA and has proved its ability to predict fracture risk in the elderly, it is less precise, there is a lack of appropriate phantoms for quality control and there are doubts about how to interpret results in younger women.

Absorptiometry, Photon↗
PubMed1997

The combined use of ultrasound and densitometry in the prediction of vertebral fracture.

Measurement of ultrasonographic parameters provides information concerning not only bone density but also bone architecture. We investigated the usefulness of ultrasonographic parameters and bone mineral density for evaluating the probability of vertebral fracture. 397 postmenopausal women (59.1 +/- 6.0 years) with (n = 178) or without (n = 219) atraumatic vertebral fractures were studied. In all women, bone mineral density (BMD) of the lumbar spine was evaluated by dual X-ray absorptiometry (DXA) and speed of sound (SOS); broadband ultrasound attenuation (BUA) and Stiffness in the calcaneus were evaluated by an Achilles unit (Lunar Corporation). Ultrasonographic parameters and BMD were compared by examining the magnitude of the odds ratios, to determine which produces the highest estimate of the probability of odds of fracture, and by examining widths of the respective confidence intervals (CI) to show which estimate of odd ratio is the most precise. The relative risk of vertebral fracture, after adjusting for potential confounders, was 3.5 (CI 2.6-4.8) for BUA; 4.5 (CI 3.2-6.2) for SOS; 5.8 (CI 4.0-8.4) for Stiffness and 7.5 (CI 4.8-11.5) for BMD. Ultrasound (US) parameters were still significant independent predictors of vertebral fracture, even after adjusting for BMD. The relative risk of fracture for a simultaneous decrease by 1 SD of BMD and by 1 SD of each ultrasound parameter was 17.3 (CI 9.4-39.6) for BMD and SOS; 18.3 (CI 8.4-30.6) for BMD and BUA and 22.1 (CI 8.9-52.7) for BMD and Stiffness. Our data suggest that US and BMD provide complementary information which can be combined to improve estimates of vertebral fracture risk.

Age Factors↗
PubMed2002

Prevalence of osteoporotic bone mineral density at the hip in Britain differs substantially from the US over 50 years of age: implications for clinical densitometry.

The purpose of this study was to compare hip bone mineral density (BMD) recorded in seven population based cohorts in Britain with the third National Health and Nutrition Examination Survey (NHANES III) US population-based reference data, in order to assess geographic variation in the prevalence of osteoporosis. Men and women aged 50-80+ years were randomly recruited from population and health registers. Dual X-ray absorptiometry (DXA) equipment was used to measure BMD at the hip, with the femoral neck and the trochanter regions studied. Prevalences of osteopenia and osteoporosis were estimated in accordance with World Health Organisation diagnostic criteria for women. Young normal data, used to establish cut-off criteria, was from NHANES III. Both male and female British subjects over 50-years-old were found to have significantly higher mean BMD at the femoral neck and trochanter than their US counterparts. Decline in BMD with age in British men appeared slower than in US men. Between British centres there were also statistically significant differences in BMD values in both sexes. British age-adjusted prevalences of osteopenia in women averaged 20% less than those of NHANES III, whereas the prevalence of osteoporosis was substantially lower in British subjects of both sexes (55% in women, 68% in men). Thus, applying the US NHANES III data as the referent, osteoporosis of the proximal femur in Britain appears to be less common than in the US, due primarily to differences in the lower tails of the BMD distributions. Providing that the relationship between fracture rates and BMD is the same in Britain and the US, it would still be appropriate to apply the reference data in fracture risk assessment in the UK.

Absorptiometry, Photon↗
PubMed2006

Bone remodelling around a cemented polyethylene cup. A longitudinal densitometry study.

The aims of this study were to examine the repeatability of measurements of bone mineral density (BMD) around a cemented polyethylene Charnley acetabular component using dual-energy x-ray absorptiometry and to determine the longitudinal pattern of change in BMD during the first 24 months after surgery. The precision of measurements of BMD in 19 subjects ranged from 7.7% to 10.8% between regions, using a four-region-of-interest model. A longitudinal study of 27 patients demonstrated a transient decrease in net pelvic BMD during the first 12 months, which recovered to baseline at 24 months. The BMD in the region medial to the dome of the component reduced by between 7% and 10% during the first three months, but recovered to approximately baseline values by two years. Changes in BMD in the pelvis around cemented acetabular components may be measured using dual-energy x-ray absorptiometry. Bone loss after insertion of a cemented Charnley acetabular component is small, transient and occurs mainly at the medial wall of the acetabulum. After two years, bone mass returns to baseline values, with a pattern suggesting a uniform transmission of load to the acetabulum.

Absorptiometry, Photon↗
PubMed2004

Association of five quantitative ultrasound devices and bone densitometry with osteoporotic vertebral fractures in a population-based sample: the OPUS Study.

UNLABELLED: We compared the performance of five QUS devices with DXA in a population-based sample of 2837 women. All QUS approaches discriminated women with and without osteoporotic vertebral fractures. QUS of the calcaneus performed as well as central DXA. INTRODUCTION: Quantitative ultrasound (QUS) methods have found widespread use for the assessment of bone status in osteoporosis, but their optimal use remains to be established. To determine QUS performance for current devices in direct comparison with central DXA, we initiated a large population-based investigation, the Osteoporosis and Ultrasound Study (OPUS). MATERIALS AND METHODS: A total of 463 women 20-39 years of age and 2374 women 55-79 years of age were measured on five different QUS devices along with DXA of the spine and the proximal femur. Their vertebral fracture status was evaluated radiographically. The association of QUS and DXA with vertebral fracture status was evaluated using logistic regression. RESULTS: All QUS approaches tested discriminated women with and without osteoporotic vertebral fractures (20% height reduction), with age-adjusted standardized odds ratios ranging 1.2-1.3 for amplitude-dependent speed of sound (AD-SOS) at the finger phalanges, 1.2-1.4 for broadband ultrasound attenuation (BUA) at the calcaneus, and 1.4-1.5 for speed of sound (SOS) at the calcaneus, 1.4-1.6 for DXA of the total femur, and 1.5-1.6 for DXA at the spine. For more severe fractures (40% height reduction), age-adjusted standardized odds ratios increased to up to 1.9 for DXA of the spine and 2.3 for SOS of the calcaneus. CONCLUSIONS: In conclusion, all five QUS devices tested showed significant age-adjusted differences between subjects with and without vertebral fracture. When selecting the strongest variable, QUS of the calcaneus worked as well as central DXA for identification of women at high risk for prevalent osteoporotic vertebral fractures. QUS-based case-finding strategies would allow halving the number of radiographs in high-risk populations, and this strategy works increasingly well for women with more severe vertebral fractures. It is likely that the good performance of QUS was in part achieved by rigorous quality assurance measures that should also be used in clinical practice.

Absorptiometry, Photon↗
PubMed1997

Prediction of vertebral strength in vitro by spinal bone densitometry and calcaneal ultrasound.

Spinal bone mineral density (BMD) measurements and calcaneal ultrasound were compared in terms of their ability to predict the strength of the third lumbar vertebral body using specimens from 62 adult cadavers (28 females, 34 males). BMD was measured using dual X-ray absorptiometry (DXA) in both vertebra and calcaneus. Quantitative computed tomography (QCT) was used to determine trabecular BMD, cortical BMD, cortical area, and total cross-sectional area (CSA) of the vertebral body. Bone velocity (BV) and broadband ultrasonic attenuation (BUA) were measured in the right calcaneus. Vertebral strength was determined by uniaxial compressive testing. Vertebral ultimate load was best correlated with DXA-determined vertebral BMD (r2 = 0.64). Of the QCT parameters, the best correlation with strength was obtained using the product of trabecular BMD and CSA (r2 = 0.61). For vertebral ultimate stress, however, the best correlation was observed with QCT-measured trabecular BMD (r2 = 0.51); the correlation with DXA-determined BMD was slightly poorer (r2 = 0.44). Calcaneal ultrasound correlated only weakly with both ultimate load and stress with correlation coefficients (r2) of 0.10-0.17, as did calcaneal BMD (r2 = 0.18). Both spinal DXA and spinal QCT were significantly (p < 0.001) better predictors of L3 ultimate load and stress than were either calcaneal ultrasound or calcaneal DXA. Multiple regression analysis revealed that calcaneal ultrasound did not significantly improve the predictive ability of either DXA or QCT for L3 ultimate load or stress. Calcaneal DXA BMD, bone velocity, and BUA correlated well with each other (r2 = 0.67-0.76), but were only modestly correlated with the DXA and QCT measurements of the vertebra. These data indicate that spinal DXA and spinal QCT provide comparable prediction of vertebral strength, but that a substantial proportion (typically 40%) of the variability in vertebral strength is unaccounted for by BMD measurements. Ultrasonic measurements at the calcaneus are poor predictors of vertebral strength in vitro, and ultrasound does not add predictive information independently of BMD. These findings contrast with emerging clinical data, suggesting that calcaneal ultrasound may be a valuable predictor of vertebral fracture risk in vivo. A possible explanation for this apparent discrepancy between in vivo and in vitro findings could be that current clinical ultrasound measurements at the calcaneus reflect factors that are related to fracture risk but not associated with bone fragility.

Absorptiometry, Photon↗
PubMed2002

Prediction of fracture risk in postmenopausal white women with peripheral bone densitometry: evidence from the National Osteoporosis Risk Assessment.

Low bone mineral density (BMD) is a risk factor for fracture. Although the current "gold standard" test is DXA of the hip and spine, this method is not universally available. No large studies have evaluated the ability of new, less expensive peripheral technologies to predict fracture. We studied the association between BMD measurements at peripheral sites and subsequent fracture risk at the hip, wrist/forearm, spine, and rib in 149,524 postmenopausal white women, without prior diagnosis of osteoporosis. At enrollment, each participant completed a risk assessment questionnaire and had BMD testing at the heel, forearm, or finger. Main outcomes were new fractures of the hip, wrist/forearm, spine, or rib within the first 12 months after testing. After 1 year, 2259 women reported 2340 new fractures. Based on manufacturers' normative data and multivariable adjusted analyses, women who had T scores < or = -2.5 SD were 2.15 (finger) to 3.94 (heel ultrasound [US]) times more likely to fracture than women with normal BMD. All measurement sites/devices predicted fracture equally well, and risk prediction was similar whether calculated from the manufacturers' young normal values (T scores) or using SDs from the mean age of the National Osteoporosis Risk Assessment (NORA) population. The areas under receiver operating characteristic (ROC) curves for hip fracture were comparable with those published using measurements at hip sites. We conclude that low BMD found by peripheral technologies, regardless of the site measured, is associated with at least a twofold increased risk of fracture within 1 year, even at skeletal sites other than the one measured.

Absorptiometry, Photon↗
PubMed2002

Universal standardization of forearm bone densitometry.

As part of an effort to quantify device-dependent differences in forearm bone density, 101 women, aged 20-80 years (approximately 16 women in each age decade), were scanned on six forearm bone densitometers: the Aloka DCS-600EX, the Hologic QDR-4500A, the Lunar PIXI, the Norland pDEXA, the Osteometer DTX-200, and the Pronosco X-posure System. Regression statistics are reported for all similar regions of interest (ROIs). However, comparisons were confounded because of large differences in the ROI size and placement. The number of ROIs reported for a single scan by each device varied from 1 to 12. The correlation coefficients ranged from 0.7 < r < 0.97, with the highest correlation coefficients and lowest SEs for comparisons between the most similar ROIs. Standardized units of bone mineral density are derived for distal (sdBMD), mid-(smBMD), and proximal (spBMD) ROTs that allow for comparable mean bone densities to be derived for patient populations. Five phantoms were scanned and characterized on five of the devices and the precision and mean values were reported. These phantom values will aid in the in vitro cross-calibration between manufacturers to recreate the presented in vivo relationships. Care should be exercised when using these equations for cross-calibrating patient databases or pooling clinical data from different devices because the least significant differences detectable from measurements taken on two different machines can be increased substantially.

Absorptiometry, Photon↗
PubMed2002

Radius bone strength in bending, compression, and falling and its correlation with clinical densitometry at multiple sites.

This study comprehensively analyzes the ability of site-specific and nonsite-specific clinical densitometric techniques for predicting mechanical strength of the distal radius in different loading configurations. DXA of the distal forearm, spine, femur, and total body and peripheral quantitative computed tomography (pQCT) measurements of the distal radius (4, 20, and 33%) were obtained in situ (with soft tissues) in 129 cadavers, aged 80.16 +/- 9.8 years. Spinal QCT and calcaneal quantitative ultrasound (QUS) were performed ex situ in degassed specimens. The left radius was tested in three-point bending and axial compression, and the right forearm was tested in a fall configuration, respectively. Correlation coefficients with radius DXA were r = 0.89, 0.84, and 0.70 for failure in three-point bending, axial compression, and the fall simulation, respectively. The correlation with pQCT (r = 0.75 for multiple regression models with the fall) was not significantly higher than for DXA. Nonsite-specific measurements and calcaneal QUS displayed significantly (p < 0.01) lower correlation coefficients, and QUS did only contribute to the prediction of axial failure stress but not of failure load. We conclude that a combination of pQCT parameters involves only marginal improvement in predicting mechanical strength of the distal radius, nonsite-specific measurements are less accurate for this purpose, and QUS adds only little independent information to site-specific bone mass. Therefore, the noninvasive diagnosis of loss of strength at the distal radius should rely on site-specific measurements with DXA or pQCT and may be the earliest chance to detect individuals at risk of osteoporotic fracture.

Absorptiometry, Photon↗
PubMed1998

A comparison of a peripheral DXA system with conventional densitometry of the spine and femur.

Because of the perceived high cost of dual-energy X-ray absorptiometry (DXA) studies of the spine and femur, there is renewed interest in small, low-cost X-ray devices for scanning the peripheral skeleton. We have compared forearm bone mineral density (BMD) measurements (distal and ultradistal sites) performed on a DTX-200 (Osteometer MediTech, Hoersholm, Denmark) with spine (L1-L4) and femur (femoral neck and total hip sites) scans performed on a QDR-4500 (Hologic, Waltham, MA) in 172 white UK women aged 22-84 yr with a view to establishing differences caused by inconsistent reference ranges and different age-related changes in BMD. All BMDs were expressed as T-scores using the manufacturers' reference ranges for the forearm and spine, and the National Health and Nutrition Examination Survey (NHANES) ranges for the femur. Linear regression between peripheral and axial sites gave correlation coefficients r = 0.71-0.74 and roof mean standard errors (RMSE) 0.88-1.14 in T-score units. Subjects were divided into the following five age groups: <40 yr; 40-49 yr; 50-59 yr; 60-69 yr and >/=70 yr. A large systematic difference between distal and ultradistal T-scores (mean DeltaT = 0.59, SEM = 0.05) was found affecting all age groups. When the mean difference in T-score between each forearm site (distal, ultradistal) and each axial site (spine, femoral neck, total hip) was examined for premenopausal subjects (n = 58) the mean difference between forearm and axial T-score showed a consistent negative offset (DeltaT = -0.41 to -0.48) for the distal forearm site and a consistent positive offset (DeltaT = +0.30 to +0.37) for the ultradistal site. When interpreting results in postmenopausal women, age-related T-score changes in the forearm were in close agreement with the femoral neck region of exterest (ROI), but systematic differences were found between the forearm and the spine and total hip sites. The two forearm and three axial sites were compared to evaluate the number of postmenopausal subjects identified as osteoporotic on the basis of the World Health Organization (WHO) Study Group criteria (T-score <-2.5). Although forearm and spine T-scores identified approximately equal numbers of subjects as osteoporotic (distal 38/114; ultradistal 31/114; spine 30/114), the two femur sites identified fewer subjects as osteoporotic (femoral neck 25/114; total hip 16/114). The number for the total hip site was statistically significantly smaller than the spine and forearm sites.

Journal Article↗
PubMed1998

Bone densitometry: choosing the proper skeletal site to measure.

In the last several years, many new techniques have been introduced for the measurement of bone density. At present, the clinician is faced with a choice between various technologies that provide measurements of different skeletal sites. Each of these techniques offer advantages and disadvantages for clinical use. Currently, no single technique ideally addresses all clinical requirements. Although all bone density techniques have clinical utility for assessing fracture risk, some devices offer advantages in terms of versatility (i.e., the number of skeletal sites which can be measured), ability to monitor response, cost, availability, and ease of use. Still, the question often is asked, which technique is the best to use? In clinical practice, the answer to this question will depend on the purpose of the bone density measurement. Different indications for bone mass evaluation will necessitate the measurement of different skeletal sites, which will in turn dictate which technique should be ideally used. In this article, the common clinical questions surrounding bone density measurements are reviewed, together with data supporting the appropriate skeletal site to measure to best answer these clinical questions.

Journal Article↗