A Hip Analysis Protocol for Pediatric Bone Densitometry: The Iowa Bone Development Study

Pediatric proximal femur dual-energy X-ray absorptiometry (DXA) scans present analytic challenges because of the lack of standard points of reference in the growing skeleton. The Iowa Bone Development Study (IBDS) developed a modified pediatric-specific proximal femur analysis protocol using Hologic software. Serial DXA measurements were obtained for 214 children at approximate ages 5, 8, 11, and 13 yr. Standard analysis procedures as described by the manufacturer (Hologic default) were compared with the IBDS protocol. The IBDS protocol yielded lower but more stable results for bone area, bone mineral content (BMC), and bone mineral density for total hip, femoral neck, trochanter, and intertrochanter as a result of more precisely controlling the regions of interest. Linear regression models with body size, age, and gender as predictors were developed to examine variation in measurements. Coefficients of determination (R²) with the IBDS protocol were greater for each time point, demonstrating that the modified protocol was better aligned with body size. Similarly, Spearman correlation coefficients between total hip and hip subregions were consistently higher for BMC and bone area with the IBDS protocol with differences more notable among younger children. The IBDS protocol provides a reproducible method for evaluating pediatric proximal femur DXA scans during growth.     

Bone Assessment in Children: Comparison of Fan-Beam DXA Analysis

Reference databases play a key role in the management of osteoporosis. The aim of this preliminary study was to compare the diagnostic consequences of using either an international or a local reference database in peripheral densitometry. For this purpose, standard curves for bone mineral density (measured by dual-energy X-ray absorptiometry at the distal and proximal forearm) were generated for healthy Hungarian men and women. In total, 303 healthy volunteers of both sexes (age range: 20–94 yr) were recruited from four osteoporosis centers. Subjects with medical conditions or taking medication affecting the bone metabolism were excluded. Bone densitometry was performed with pDEXA (Norland-Stratec, Fort Atkinson, WI) devices in each center after cross-calibration of the machines. The precision error of the forearm measurement was also determined (< 1% in vitro, and 1.2–2.5% in vivo). In females, the peak forearm density was detected in the 30–39-yr group. The density decreased by 8% per 5 yr in early postmenopausal females, and by 10% per 10 yr in late postmenopausal females. In males, the highest bone mineral density was found in the 30–39-yr group for the distal forearm, but 1 decade later for the proximal site. Subsequently, a 5% decrease in density occurred per 10 yr, except in the 8th decade, in which a 20% decrease was demonstrated. One thousand four hundred thirty-four patients with suspected osteoporosis were classified according to the forearm density T-scores using both the new Hungarian reference database and the international database provided by the manufacturer. Comparison of the results measured at the distal forearm with the two different databases led to similar outcomes. However, at the proximal site, one fifth of the female patients were reclassified from the low-density group to the normal group using the domestic normative database. An opposite difference was observed for the males: use of the Hungarian reference data resulted in 40% more men being categorized in the low-density group than when the international normal database was applied. Our results suggest that not only geographic differences, but also the reference database used, can influence the prevalence of the diagnosis of osteoporosis. Further data are currently being collected to increase the statistical power of the study.     

Automated Assessment of Exclusion Criteria for DXA Lumbar Spine Scans

Modern bone densitometry systems using dual-energy X-ray absorptiometry (DXA) automatically analyze lumbar spine scans and provide clinically important information concerning spine bone mineral density (BMD) and fracture risk. Lumbar spine BMD accurately reflects skeletal health and fracture risk in most cases, but degenerative diseases associated with aging may lead to the formation of reactive bone (osteophytes) and other confounding conditions that elevate BMD without a concomitant increase in bone strength or decrease in fracture risk. Automated densitometry software known as computer-aided densitometry (CAD) (GE Medical Systems Lunar) assists the user in identifying scans with common acquisition and analysis irregularities known to influence BMD values. Visual examination of 231 female spine scans measured with DXA found abnormal conditions that could influence BMD results in 29% of scans. The sensitivity and specificity of several criteria for identifying scans with conditions that could influence BMD were determined. A good criterion for identifying scans with abnormal conditions was a T-score difference of greater than 0.9 or 1.0 between L1-L4 mean and individual vertebrae. Criteria for excluding affected vertebrae were determined. Exclusion of affected vertebrae resulted in a mean BMD decrease of nearly 0.6 SD (T-score) among affected scans.     

Optimal monitoring time interval between DXA measures in children

The monitoring time interval (MTI) is the expected time in years necessary to identify a change between two measures that exceeds the measurement error. Our purpose was to determine MTI values for dual‐energy X‐ray absorptiometry (DXA) scans in normal healthy children, according to age, sex, and skeletal site. 2014 children were enrolled in the Bone Mineral Density in Childhood Study and had DXA scans of the lumbar spine, total hip, nondominant forearm, and whole body. Measurements were obtained annually for seven visits from 2002 to 2010. Annualized rates of change were calculated by age and sex for all bone regions. A subgroup of 155 children ages 6 to 16 years (85 boys) had duplicate scans for calculation of scan precision. The bone mineral density (BMD) regions of interest included the spine, total body less head (TBLH), total hip, femoral neck, and one‐third radius. Bone mineral content (BMC) was also evaluated for the spine and TBLH. The percent coefficient of variation (%CV) and MTI were calculated for each measure as a function of age and sex. The MTI values were substantially less than 1 year for the TBLH and spine BMD and BMC for boys ≤ 17 years and girls ≤ 15 years. The hip and one‐third radius MTIs were generally 1 year in the same group. MTI values as low as 3 months were found during the peak growth years. However, the MTI values in late adolescence for all regions were substantially longer and became nonsensical as each region neared the age for peak bone density. All four DXA measurement sites had reasonable (< 1 year) MTI values for boys ≤ 17 years and girls ≤ 15 years. MTI was neither useful nor stable in late adolescence and young adulthood. Alternative criteria to determine scan intervals must be used in this age range. © 2011 American Society for Bone and Mineral Research     

Monitoring Bone Growth Using Quantitative Ultrasound in Comparison with DXA and pQCT

Quantitative ultrasound (QUS) is a safe, inexpensive, and nonradiation method for bone density assessment. QUS correlates with, and predicts fragility fractures comparable to, dual-energy X-ray absorptiometry (DXA)-derived bone mineral density (BMD) in postmenopausal women. However, its validity in monitoring bone growth in children is not well understood. Two hundred and fifty-eight 10–13 yr pubertal girls and 9 37–43 yr adults without diseases or history of medications known to affect bone metabolism were included in the 2-yr prospective study. Calcaneal broadband ultrasound attenuation (cBUA) was assessed using QUS-2 (Quidel, Santa Clara, CA), speed of sound of tibial shaft (tSOS) using Omnisense (Sunlight Technologies, Israel), apparent volumetric BMD (vBMD) of tibial shaft using peripheral quantitative computed tomography (pQCT; XCT2000, Stratec), and femoral neck (FN) and lumbar spine 2–4 (LS) areal BMD (aBMD) using DXA (Prodigy, GE). Over the 2 yr in girls, FN and LS aBMD showed the largest increases (17 ± 8% and 20 ± 8%, respectively), followed by tibial vBMD and cBUA (10 ± 5% and 9 ± 9%, respectively). There was no apparent change in tSOS (2 ± 3%). The increase in FN and LS aBMD attenuated 48% and 40%, respectively, after adjustment of the change in body size. The change of cBUA correlated significantly with change in tibial vBMD and FN and LS aBMD (r = 0.24–0.40). At the matched location, tSOS correlated only with cortical vBMD, not with cortical thickness, apparent vBMD, or bone size. The long-term reproducibility, assessed using the concordance correlation coefficient of young adults' pre-post measurements, was substantially lower in tSOS than cBUA, tibial vBMD, FN, and LS aBMD (0.65 vs 0.97, 0.95, 0.98, and 0.96; p < 0.05). The transverse transmission method-derived calcaneal BUA, but not the axial transmission method-derived SOS, is comparable to DXA and pQCT for monitoring bone densitometric change in pubertal girls. The role of QUS in fracture-risk prediction in children and adolescents needs further investigation.     

Immunosuppressant Drugs and Bone Disease: A Clinician''s Perspective

Immunosuppressant agents are used widely for a variety of diseases, and their usage will increase as organ transplantation becomes more frequent. One of the consequences of their administration is the occurrence of rapid bone loss with fractures. Generally, glucocorticoids (GC) are the main culprit, but calmodulin-calcineurin phosphatase inhibitors, e.g., cyclosporine and tacrolimus, seem to play a role as does the underlying disease, which necessitates treatment or organ transplantation. The mechanisms for the bone disease are multifactorial and actively being researched. The management at present is largely empirical and consists of calcium, vitamin D, and antiresorbers, especially bisphosphonates. In order to achieve an optimum treatment strategy, bone density measurements are essential to define the severity of the bone loss, help decide therapy and monitor progress of the patient.     

Prevalence of Osteoporosis Using DXA Bone Mineral Density Measurements at the Calcaneus: Cut-Off Points of Diagnosis and Exclusion of Osteoporosis

The objective of this article is to evaluate different T-score cut-off points in the calcaneus in order to establish the prevalence of osteoporosis in the general population and to evaluate the clinical value of bone mineral density at the calcaneus as a tool to identify patients with spine or hip osteoporosis. A total of 1455 people (727 women and 728 men) from the Hortega cohort were studied. The densitometric studies were carried out in the calcaneal region using a Peripheral Instantaneous X-ray Imaging (PIXI) Lunar bone densitometer. We established three cut-off points (-1.6, -2.0, -2.5). One-hundred twenty-five patients (67 men with a mean age of 47 +/- 13 yr and 58 women with a mean age of 66 +/- 8 yr) from internal medicine outpatient clinics who were undergoing densitometry of the calcaneus, spine, and hip were subsequently studied. The prevalence of osteoporosis in women with a calcaneus T-score -1.6 was 12.4%, which is comparable to the 12.7% obtained with an axial densitometer in a Spanish population. The prevalence in men was 7.8%, with a calcaneus T-score of <-2.0. In women, the highest sensitivity (85%) was obtained with a calcaneus T-score of <-1.0 and the highest specificity with a calcaneus T-score of <-2.5. In men, the best sensitivity (61%) was obtained with a calcaneus T-score of <-1.0 and the best specificity (98%) with a calcaneus T-score of <-2.5. A calcaneus T-score <-1.6 is an adequate cut-off to establish the prevalence of osteoporosis in population studies. In women, a calcaneus T-score of >-1.0 enables the diagnosis of the disease to be excluded, whereas a calcaneus T-score of <-2.5 enables the diagnosis to be confirmed and treatment to be initiated in both men and women.     

Mid-Term Study of Bone Remodeling After Femoral Cemented Stem Implantation: Comparison Between DXA and Finite Element Simulation

This five-year prospective study was designed to investigate periprosthetic bone remodeling associated with two cemented stem models, ABG-II (Stryker) and VerSys (Zimmer), randomly implanted in patients older than 75 years. The sample consisted of 64 cases (32, ABG-II; 32, VerSys). Inclusion criterion was diagnosis of osteoarthritis recommended for cemented total hip arthroplasty. Besides clinical study, Finite Element (FE) simulation was used to analyze biomechanical changes caused by hip arthroplasty. Bone Mineral Density (BMD) measurements showed a progressive increase in bone mass throughout the entire follow-up period for both stems, well correlated with FE results except in Gruen zones 4, 5, 6 for ABG-II and in zones 4, 5 for VerSys, denoting that remodeling in those zones does not depend on mechanical factors but rather on biological or physiological ones.     

Risk Assessment for Osteoporosis Using Bone Mineral Density Determination: A Belgian Perspective

The availability of bone densitometry in daily clinical practice has revolutionized the capacity to detect osteoporosis, to estimate the risk of future fracture, and to select those patients who are likely to benefit most from preventive or therapeutic measures. In spite of the high availability of densitometry in Belgium and the high incidence of risk factors for osteoporosis in elderly women, osteoporosis is presumably underdiagnosed. It is likely that the limited use of widely available technology to evaluate osteoporosis results from a complex interaction of numerous factors, some of which are discussed. In spite of many unanswered questions, the main conclusion to be drawn from the Belgian experience is that a high density of densitometry facilities is no guarantee that the majority of women who are at greatest risk of fracture will actually become the focus of preventive measures or therapy.     

Validation of Longitudinal DXA Changes in Body Composition From Pre- to Mid-Adolescence Using MRI as Reference

Dual-energy X-ray absorptiometry (DXA) has been used extensively for bone mineral density and body composition assessments. Surprisingly, the role of DXA in monitoring changes in children’s body composition, using direct imaging methods such as magnetic resonance imaging (MRI) as reference, is still yet to be validated. We aimed at validating the use of DXA in monitoring change in the thigh lean soft tissue mass (LSTM) and fat mass (FM) when compared with thigh skeletal muscle mass (SM) and FM, measured using MRI as the reference standard, from childhood to midadolescence. At baseline, 22 healthy children (16 boys and 6 girls) aged 8–11 yr were included, and then recalled at pubertal stage Tanner2–Tanner4. LSTM-DXA and FM-DXA of the mid-third femur and SM-MRI and FM-MRI of the same region were measured on the same day. The same protocol was repeated 26–48 mo later. At baseline, DXA overestimated LSTM-DXA on average by 222 g (95% confidence interval [CI]: 33–410 g) with a concordance C-LSTM = 0.576. FM-MRI and FM-DXA were not significantly different (95% CI = 213 to 199 g, the C-FM = 0.907). At follow-up, change in LSTM-DXA and FM-DXA were not significantly different to change in SM-MRI and FM-MRI, respectively (95% CI of the difference was −278 to 208 g for LSTM, and −148 to 236 g for FM). The coefficient of concordance between the 2 techniques was 0.88 for both LSTM and FM. This study validates the use of DXA in monitoring changes in LSTM and FM in children, confirming its significant potential in clinical and research roles in pediatric body composition.     

The Utility of Portable Dual-Energy X-Ray Absorptiometry of the Wrist in Patients Referred to a Bone Health Clinic: A Pilot Study

Fifty white female patients referred to a bone health care clinic were studied. Patients with a history of fracture were excluded. At the time of hip and spine dual-energy X-ray absorptiometry (DXA), those willing underwent portable dual-energy X-ray absorptiometry (pDXA) of the wrist. The mean age of the patients was 57 yr. Bone mineral density (BMD) assessment was performed on each patient at four different sites: posterior-anterior lumbar spine, nondominant hip, the distal radius and ulna, and the proximal radius and ulna of the nondominant arm. Comparison of the pDXA results with that of the conventional DXA results showed the highest correlation between pDXA of the distal radius and ulna (DR + U) and the DXA of the femoral neck and lumbar spine. By defining a pDXA (DR + U) T-score 相似文献   

Definition of a population-specific DXA reference standard in Italian women: the Densitometric Italian Normative Study (DINS)

Osteoporosis is currently defined on the basis of the T-score by dual-energy X-ray absorptiometry (DXA). Despite its limitations, this definition is applied worldwide. However, the normal values provided by manufacturers may not be fully representative of specific local populations. So far, there are no normative data in the Italian population using Hologic densitometers. The Densitometric Italian Normative Study (DINS) is an ongoing multi-center study that aims to establish reference values for bone densitometry with dual-energy X-ray absorptiometry (DXA) in the male and female Italian population. In this paper we report the results of the lumbar vertebrae (L2–L4) and proximal femur in 1,622 women aged 20–79 years. Bone mineral density (BMD) was determined using dual-energy X-ray absorptiometry (DXA) on Hologic bone densitometers (Hologic, Waltham, Mass.). Most of the subjects were examined with a QDR 4500. The BMD of the lumbar vertebrae was virtually constant between 20 and 49 years (test for trend: P=0.66); the BMD values between 20–45 in premenopausal women (mean 1.036; SD 0.109 g/cm²) were thus defined as the peak bone mass values, significantly lower compared to the Hologic reference curve (mean 1.079, SD 0.11 g/cm²). The mean BMD values of the femoral neck were virtually identical to those of the NHANES study in the first 3 decades; after the age of 50 the BMD values were slightly greater than those of the NHANES subject. The subject classification according to the WHO criteria was similar using the DINS and NHANES reference values for the femur; for the spine, the Hologic reference values classified a larger proportion of women as osteoporotic (21 vs. 16%) or osteopenic (42 vs. 38%) compared to DINS.     

Comparison of Bone Mineral Density of the Phalanges, Lumbar Spine, Hip, and Forearm for Assessment of Osteoporosis in Postmenopausal Women

The objective of this study was to compare peripheral bone mineral density (BMD) of the phalanges with BMD of the lumbar spine, total hip, femoral neck, and forearm and to determine the clinical value of measuring a single peripheral site (phalanges) in identifying postmenopausal women with osteoporosis. BMD was measured by dual energy X-ray absorptiometry using the accuDEXA((R)) (ADXA-finger) (Schick, New York, NY) and the QDR-4500 (DXA-lumbar spine, hip, forearm) (Hologic, Waltham, MA). Correlation coefficients between ADXA and DXA of the lumbar spine, total hip, femoral neck and one third radial site ranged from 0.53 to 0.73. The sensitivity of an ADXA T-score of -2.5 in identifying patients with a DXA T-score of < or = -2.5 at the femoral neck was 35%. An ADXA T-score cut point of -1.0 improved the sensitivity of ADXA in identifying patients with a femoral neck T-score of < or = -2.5 (85%), but the specificity declined from 88 to 49%. There was substantial discordance in the diagnosis of osteoporosis when a single site was measured, regardless of technique. Within the limitations of single-site measurements, BMD measured by ADXA has adequate sensitivity to identify women with low BMD at the femoral neck, if an appropriate T-score criterion is used.     

Heritability of bone density: Regional and gender differences in monozygotic twins

Bone mineral density (BMD) is a measure of a person's skeletal mineral content, and assessing BMD by dual x‐ray absorptiometry (DEXA) can help to diagnose diseases of low bone density. In this study, we determine the heritability of BMD in male and female monozygotic twin subjects using DEXA in 13 specific anatomical regions. In an attempt to quantify the genetic contribution of gender and skeletal region to BMD heritability, we scanned 14 pairs of identical twins using DEXA and calculated the broad‐sense heritability coefficient (H²) in each of the 13 different body regions. The region of the body that was most heritable for both genders was the head (H² ≥ 95%). When males were compared to females, H² values for male hip (H² = 87%) and lower extremities (H² = 90%) were higher than those in females (H² = 49% and 56%, respectively). Conversely, H² value for the female pelvis (H² = 68%) was higher than that for males (H² = 26%). These data show that different regions of the skeleton exhibit different degrees of heritability, and that the variation depends on gender. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:150–154, 2009     

Age-related differences in total and regional bone mass: A cross-sectional study with DXA in 429 normal women

Total body bone mineral content (TBBMC), total body bone mineral density (TBBMD) and regional bone mineral content (BMC) and density (BMD) were assessed by dual-energy X-ray absorptiometry (DXA) in 429 normal women aged 15–83 years, of whom 242 were premenopausal and 187 postmenopausal. The population was divided into 5-year age groups. In the premenopausal women no changes in TBBMC, TBBMD or regional BMC and BMD were observed with age, and TBBMC and TBBMD values correlated well with body weight (p<0.001). Postmenopausal women showed an overall reduction in bone mass (p<0.001), more marked at the axial level than peripherally (1.6% vs. 0.8%/year). The values of TBBMC and TBBMD correlated well with chronological age, time since the onset of menopause and body weight (p<0.001). In these women age did not correlate with body weight, which suggests that postmenopausal bone mass loss depends more on chronological age and time since the onset of menopause than on other variables. The stability observed in bone mass values from ages 15–19 to menopause highlights the importance of stimulating the acquisition of an appropriate peak bone mass in women before adolescence begins.