Age at menarche and cortical bone geometry in premenopausal women

3T-MRI-based age, sex and site-specific markers of musculoskeletal health in healthy children and young adults

Objective

The aim of this study is to investigate the role of 3T-MRI in assessing musculoskeletal health in children and young people.

Design

Bone, muscle and bone marrow imaging was performed in 161 healthy participants with a median age of 15.0 years (range, 8.0, 30.0).

Methods

Detailed assessment of bone microarchitecture (constructive interference in the steady state (CISS) sequence, voxel size 0.2 × 0.2 × 0.4 mm3), bone geometry (T1-weighted turbo spin echo (TSE) sequence, voxel size 0.4 × 0.4 × 2 mm3) and bone marrow (1H-MRS, point resolved spectroscopy sequence (PRESS) (single voxel size 20 × 20 × 20 mm3) size and muscle adiposity (Dixon, voxel size 1.1 × 1.1 × 2 mm3).

Results

There was an inverse association of apparent bone volume/total volume (appBV/TV) with age (r = -0.5, P < 0.0005). Cortical area, endosteal and periosteal circumferences and muscle cross-sectional area showed a positive association to age (r > 0.49, P < 0.0001). In those over 17 years of age, these parameters were also higher in males than females (P < 0.05). This sex difference was also evident for appBV/TV and bone marrow adiposity (BMA) in the older participants (P < 0.05). AppBV/TV showed a negative correlation with BMA (r = -0.22, P = 0.01) which also showed an association with muscle adiposity (r = 0.24, P = 0.04). Cortical geometric parameters were highly correlated with muscle area (r > 0.57, P < 0.01).

Conclusions

In addition to providing deep insight into the normal relationships between bone, fat and muscle in young people, these novel data emphasize the role of MRI as a non-invasive method for performing a comprehensive and integrated assessment of musculoskeletal health in the growing skeleton.

The Relationship Between Greater Prepubertal Adiposity, Subsequent Age of Maturation, and Bone Strength During Adolescence

This longitudinal study investigated whether greater prepubertal adiposity was associated with subsequent timing of maturation and bone strength during adolescence in 135 girls and 123 boys participating in the Iowa Bone Development Study. Greater adiposity was defined using body mass index (BMI) data at age 8 years to classify participants as overweight (OW, ≥85th percentile for age and sex) or healthy weight (HW). Maturation was defined as the estimated age of peak height velocity (PHV) based on a series of cross-sectional estimates. Measurements were taken at ages 11, 13, 15, and 17 years for estimates of body composition by dual-energy X-ray absorptiometry (DXA), bone compression (bone strength index), and torsion strength (polar strength-strain index) at the radius and tibia by pQCT, and femoral neck bending strength (section modulus) by hip structural analysis. Bone strength in OW versus HW were evaluated by fitting sex-specific linear mixed models that included centered age (visit age - grand mean age of cohort) as the time variable and adjusted for change in fat mass, and limb length in model 1. Analyses were repeated using biological age (visit age - age PHV) as the time variable for model 1 with additional adjustment for lean mass in model 2. BMI was negatively associated with age of maturation (p < 0.05). OW versus HW girls had significantly greater bone strength (p < 0.001) in model 1, whereas OW versus HW boys had significantly greater bone strength (p < 0.001) at the tibia and femoral neck but not radius (p > 0.05). Analyses were repeated using biological age, which yielded reduced parameter estimates for girls but similar results for boys (model 1.) Differences were no longer present after adjustment for lean mass (model 2) in girls (p > 0.05) whereas differences at the tibia were sustained in boys (p < 0.05). These findings demonstrate sex- and site-specific differences in the associations between adiposity, maturation, and bone strength. © 2016 American Society for Bone and Mineral Research.

Bivariate genome-wide association analyses identified genes with pleiotropic effects for femoral neck bone geometry and age at menarche

Femoral neck geometric parameters (FNGPs), which include cortical thickness (CT), periosteal diameter (W), buckling ratio (BR), cross-sectional area (CSA), and section modulus (Z), contribute to bone strength and may predict hip fracture risk. Age at menarche (AAM) is an important risk factor for osteoporosis and bone fractures in women. Some FNGPs are genetically correlated with AAM. In this study, we performed a bivariate genome-wide association study (GWAS) to identify new candidate genes responsible for both FNGPs and AAM. In the discovery stage, we tested 760,794 SNPs in 1,728 unrelated Caucasian subject, followed by replication analyses in independent samples of US Caucasians (with 501 subjects) and Chinese (with 826 subjects). We found six SNPs that were associated with FNGPs and AAM. These SNPs are located in three genes (i.e. NRCAM, IDS and LOC148145), suggesting these three genes may co-regulate FNGPs and AAM. Our findings may help improve the understanding of genetic architecture and pathophysiological mechanisms underlying both osteoporosis and AAM.

Peripubertal estrogen levels and physical activity affect femur geometry in young adult women

The growing skeleton is particularly responsive to exercise around the time of puberty, suggesting a possible role for estrogen in mechanical adaptation in young women. We assessed femoral neck strength index at age 17 in young women with varying adolescent physical activity levels and E2 levels in the first 3 years after menarche. The results indicate that both E2 levels in the first year after menarche and adolescent physical activity are positively associated with bone strength in young adulthood, such that hormone levels may modify human osteogenic responses to exercise.

INTRODUCTION

It is well established that physical activity contributes to bone strength in young females, but less is known about how peripubertal estrogen affects skeletal responses to exercise.

METHODS

We used data from 84 participants in the Penn State Young Women's Health Study to test the prediction that young women who (1) had higher E2 levels during the first year after menarche or (2) were more physically active in adolescence will have greater bone strength at the end of adolescence. Subjects were divided into tertiles of physical activity and of E2 level in the first, second, and third postmenarchal years, and femoral strength was calculated from dual-energy X-ray absorptiometry scans of the proximal femur using hip structure analysis.

RESULTS

At age 17, subjects with the highest E2 levels in year 1 after menarche had 5-14% greater strength in the narrow neck and intertrochanteric region, and the most active subjects had 10-11% greater strength in the femoral narrow neck vs. less active girls.

CONCLUSIONS

This study suggests that both physical activity and peripubertal estrogen have important influences on young adult bone strength and that hormone levels may be mediators of human osteogenic responses to exercise.

History of amenorrhoea compromises some of the exercise-induced benefits in cortical and trabecular bone in the peripheral and axial skeleton: a study in retired elite gymnasts

BACKGROUND

Female gymnasts frequently present with overt signs of hypoestrogenism, such as late menarche or menstrual dysfunction. The objective was to investigate the impact of history of amenorrhoea on the exercise-induced skeletal benefits in bone geometry and volumetric density in retired elite gymnasts.

SUBJECTS AND METHODS

24 retired artistic gymnasts, aged 17-36 years, who had been training for at least 15 h/week at the peak of their career and had been retired for 3-18 years were recruited. They had not been engaged in more than 2 h/week of regular physical activity since retirement. Former gymnasts who reported history of amenorrhoea ('AME', n=12: either primary or secondary amenorrhoea) were compared with former gymnasts ('NO-AME', n=12) and controls ('C', n=26) who did not report history of amenorrhoea. Bone mineral content (BMC), total bone area (ToA) and total volumetric density (ToD) were measured by pQCT at the radius and tibia (4% and 66%). Trabecular volumetric density (TrD) and bone strength index (BSI) were measured at the 4% sites. Cortical area (CoA), cortical thickness (CoTh), medullary area (MedA), cortical volumetric density (CoD), stress-strain index (SSI) and muscle and fat area were measured at the 66% sites. Spinal BMC, areal BMD and bone mineral apparent density (BMAD) were measured by DXA.

RESULTS

Menarcheal age was delayed in AME when compared to NO-AME (16.4+/-0.5 years vs. 13.3+/-0.4 years, p<0.001). No differences were detected between AME and C for height-adjusted spinal BMC, aBMD and BMAD, TrD and BSI at the distal radius and tibia, CoA at the proximal radius, whereas these parameters were greater in NO-AME than C (p<0.05-0.005). AME had lower TrD and BSI at the distal radius, and lower spinal BMAD than NO-AME (p<0.05) but they had greater ToA at the distal radius (p<0.05).

CONCLUSION

Greater spinal BMC, aBMD and BMAD as well as trabecular volumetric density and bone strength in the peripheral skeleton were found in former gymnasts without a history of menstrual dysfunction but not in those who reported either primary or secondary amenorrhoea. History of amenorrhoea may have compromised some of the skeletal benefits associated with high-impact gymnastics training.

Hypothalamic suppression decreases bone strength before and after puberty in a rat model

The incidence of menstrual irregularities, both primary and secondary amenorrhea, has been reported to be as high as 60%, with the highest incidence in younger athletes, suggesting possible adverse effects on bone development. It was hypothesized that in a rat model, suppressed hypothalamic activity via a gonadotropin-releasing hormone antagonist (GnRH-a) before onset of puberty would result in a relatively larger bone strength deficit compared with suppression after puberty. Hypothalamic suppression was achieved by providing GnRH injections. Animals received injections for 25 days either before puberty (pre group) (age 23-46 days) or after puberty (post group) (age 65-90 days). Body weights and uterine weights were measured. Serum estradiol was assayed. Mechanical strength of the right femora and histomorphometry of the left femur were measured. Suppression of the hypothalamic-pituitary-gonadal axis was confirmed by significant atrophy of uterine tissue and suppressed estradiol levels. The peak moment was significantly lower in the pre and post GnRH-a groups compared with control. The percentage difference of the average peak moment and stiffness values from the respective age-matched control groups yielded a greater percentage difference in the pre group. The cortical area was less in the GnRH-a-treated groups, but no significant difference between the relative deficits between pre and post groups were found. Hypothalamic-pituitary-gonadal axis suppression before puberty resulted in a significantly larger deficit in mechanical strength compared with postpubertal animals. The time before puberty may represent a time when skeletal strength is more compromised. Women experience both primary and secondary amenorrhea; however, the treatment may need to be different for each condition.

High and low birth weight and its implication for growth and bone development in childhood and adolescence

AIM

To investigate the relationship of birth weight (BW) to anthropometric measures, local body composition and bone development.

POPULATION AND METHODS

284 individuals (age 5-19 yr, 145 females) were recruited from the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study. Parameters of bone development (cortical bone mineral density [BMDcort], endosteal circumference [CE]) and of local body composition (cross-sectional fat area [FA]) were analyzed by pQCT at the forearm. Parameters were transformed into SD scores to adjust for age or height.

RESULTS

BW predicted weight-SDS (R = 0.221), height-SDS (R = 0.260) and FA-SDS (R = 0.150). Individuals with lower BW (< 10th percentile) had lower weight-SDS (p < 0.01), height-SDS (p < 0.01), BMDcort-SDS (p = 0.02) and higher CE-SDS (p = 0.05). BMDcort was correlated with BW (r = -0.319) and FA (r = -0.283) in pubertal females.

CONCLUSION

BW is characterized by direct and indirect effects on growth, body composition and bone development.

Whole bone geometry and bone quality in distal forearm fracture

Fracture of the distal radius is a sentinel for future increased risk of other "osteoporotic" fractures, in which the peak age for incidence of distal radius fracture is 5 to 10 years before that for spine and hip fractures. Mean bone mineral density (BMD) of the distal radius was lower in patients with osteoporosis compared with age- and sex-matched normal subjects. However, it has been shown that to predict the strength of the distal radius at the site where fractures occur requires more than measurement of bone mineral content (BMC) or BMD. Only moderate correlations have been found between forearm sites, which may be a result of differences in bone composition between sites. Different forearm sites may be used interchangeably for diagnostic purposes, but the prognostic value is not known. Using the distal radius as a screening tool for identifying individuals at risk of "osteoporotic" fracture shows that forearm site selection and accuracy of measurement can be important confounders in group studies.Improving resolution of computed tomography (CT) scanners has enabled quantitation of cortical bone density and cortical thickness. These measurements have enabled the mechanism of bone loss in the distal radius to be elucidated and show that, after menopause, bone loss is primarily through thinning of the cortex. CT imaging allows the precise localization of bone changes in individuals and should be of value in the assessment of the severity of osteoporosis. It also shows that this technology has the potential to determine the efficacy of therapeutic interventions. A concerted effort has been made to elucidate the interrelationships between the amount of bone and the geometry and that clinical imaging of BMC and/or cross-sectional area in the radius would provide improved prediction of an individual's risk of fracture.The technological tools are available, in the clinic, to accurately measure the 3-dimensional (3D) geometry of the distal radius and the amount of bone. In addition, the cortical and cancellous bone compartments can be analyzed separately. This capability, along with the easy accessibility of the distal radius to clinical imaging modalities, provides an excellent framework for longitudinal prospective studies to determine morphologic risk factors for osteoporotic fractures of the distal radius.

Subcutaneous fat and body fat mass have different effects on bone development at the forearm in children and adolescents

The present study investigated whether subcutaneous fat differs in the impact on bone development from fat mass (FM). We analyzed 295 healthy children and adolescents (age 5-19 years, 139 males) for FM by measuring four skinfold thicknesses and for bone development and body composition at the forearm by peripheral quantitative computed tomography in a cross-sectional investigation. Relative cross-sectional fat area (FA) was a surrogate for relative subcutaneous FM at the forearm and was associated positively with percent fat in prepubertal individuals and pubertal females but negatively in pubertal males. Percent FM was associated with trabecular bone mineral density (BMDtrab) in prepubertal individuals (females r = 0.394, males r = 0.242) and pubertal individuals (females r = 0.215, males r = -0.275). Bone mineral count was correlated with percent FM in pubertal males (r = -0.287). FA was correlated with BMDtrab (r = 0.285) and with cortical bone mineral density (BMDcort, r = -0.296) in pubertal females. The ratio FA/ FM was negatively correlated with BMDcort (r = -0.299) in pubertal females. Pubertal females with relatively high subcutaneous fat area (high ratio FA/FM) were characterized by lower bone strength (P = 0.047). FM and the relative amount of subcutaneous fat have effects on bone formation and resorption that depend on gender and puberty. Especially in pubertal females, higher levels of subcutaneous fat may decrease bone strength due to increased cortical remodeling.

Relationship of circulating total homocysteine and C-reactive protein to trabecular bone in postmenopausal women

Homocysteine (Hcy) and C-reactive protein (CRP) are novel risk factors for osteoporosis. The purpose of this analysis was to determine the relationship of Hcy and CRP to volumetric trabecular bone, but also to assess their relationship to areal composite bone in healthy postmenopausal women (N=184). We used peripheral quantitative computed tomography to assess volumetric bone at the distal tibia and dual-energy X-ray absorptiometry to assess areal composite bone at the proximal femur and lumbar spine. Multiple regression revealed that 22% of the variability in trabecular bone mineral content (F=9.59, p Collapse

Key Words

• homocysteine
• c-reactive protein
• pqct
• trabecular bone
• osteoporosis
• postmenopausal women

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MESH Headings

• Aged
• Blood Glucose/metabolism
• Bone Density
• Bone and Bones/metabolism
• Bone and Bones/pathology
• C-Reactive Protein/biosynthesis
• Double-Blind Method
• Female
• Hemoglobins/metabolism
• Homocysteine/blood
• Humans
• Middle Aged
• Osteoporosis, Postmenopausal/blood
• Osteoporosis, Postmenopausal/diagnosis
• Placebos
• Postmenopause
• Regression Analysis
• Research Design
• Uric Acid/metabolism

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Grants

• R01 AR046922 NIAMS NIH HHS
• AR046922 NIAMS NIH HHS

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Affiliation(s)

Shilpa N Bhupathiraju Department of Food Science and Human Nutrition, Human Metabolic Unit, Center for Designing Foods to Improve Nutrition, Iowa State University, Ames, IA 50011, USA
D Lee Alekel
Jeanne W Stewart
Laura N Hanson
Kristine M Shedd
Manju B Reddy
Kathy B Hanson
Marta D Van Loan
Ulrike Genschel
Kenneth J Koehler

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Collaborators Collapse

Structural and functional assessment of trabecular and cortical bone by micro magnetic resonance imaging

Osteoporosis is a multifactorial disorder of bone mineral homeostasis affecting the elderly. It is a major public health issue with significant socioeconomic consequences. Recent findings suggest that bone loss-the key manifestation of the disease-is accompanied by architectural deterioration, both affecting the bone's mechanical competence and susceptibility to fracture. This article reviews the potential of quantitative micro MRI (mu-MRI), including a discussion of the technical requirements for image acquisition, processing, and analysis for assessing the architectural implications of osteoporosis and as a means to monitor the response to treatment. With current technology, the resolution achievable in clinically acceptable scan times and necessary signal-to-noise ratio (SNR) is comparable to trabecular thickness. This limited spatial resolution regime demands processing and analysis algorithms designed to operate under such limiting conditions. It is shown that three different classes of structural parameters can be distinguished, characterizing scale, topology, and orientation. There is considerable evidence that osteoporotic bone loss affects all three classes but that topological changes, resulting from conversion of trabecular plates to rods, with the latter's eventual disconnection, are particularly prominent. Clinical applications discussed can be divided into those dealing with assessment of osteoporotic fracture risk as opposed to the study of the effect of disease progression and regression in response to treatment. Current data suggest that noninvasive assessment of cortical and trabecular bone (TB) architecture by mu-MRI may provide new surrogate endpoints to assess the efficacy of intervention in osteoporosis treatment and prevention.

Glucocorticoid-induced osteoporosis in children: impact of the underlying disease

Glucocorticoids inhibit osteoblasts through multiple mechanisms, which results in significant reductions in bone formation. The growing skeleton may be especially vulnerable to adverse glucocorticoid effects on bone formation, which could possibly compromise trabecular and cortical bone accretion. Although decreased bone mineral density has been described in various pediatric disorders that require glucocorticoids, and a population-based study reported increased fracture risk in children who require >4 courses of glucocorticoids, some of the detrimental bone effects attributed to glucocorticoids may be caused by the underlying inflammatory disease. For example, inflammatory cytokines that are elevated in chronic disease, such as tumor necrosis factor alpha, suppress bone formation and promote bone resorption through mechanisms similar to glucocorticoid-induced osteoporosis. Summarized in this review are changes in bone density and dimensions during growth, the effects of glucocorticoids and cytokines on bone cells, the potential confounding effects of the underlying inflammatory-disease process, and the challenges in interpreting dual-energy x-ray absorptiometry results in children with altered growth and development in the setting of glucocorticoid therapy. Two recent studies of children treated with chronic glucocorticoids highlight the differences in the effect of underlying disease, as well as the importance of associated alterations in growth and development.

Short-term delay of puberty causes a transient reduction in bone strength in growing female rats

Multiple factors affect the structural development of the skeleton; in particular, estrogen levels during growth are an important factor in the pathogenesis of bone fragility. The delay of menarche and infrequent menstrual cycles decrease estrogen levels during adolescence and decrease peak bone mass. The aim of this study was to determine if delayed puberty through administration of a GnRH antagonist initiated prior to the onset of the first estrus cycle would delay the increase in estrogen levels and impede bone strength development in female rats. Twenty-three-day-old female Sprague-Dawley rats were randomly assigned to one of four groups; 1) short-term control group (C-ST) (n = 12), 2) long-term control (C-LT) (n = 12), 3) short-term GnRH antagonist group (G-ST) (n = 12) and 4) long-term GnRH antagonist group (G-LT) (n = 12). Injections (0.2 ml) of either saline or GnRH antagonist (100 microg/day) (Cetrotide, Serono, Inc) were given intraperitoneally for a duration of 18 days. Pubertal and gonadal development was retarded as indicated by a delay in vaginal opening (an indicator of pubertal onset), lower ovarian and uterine weights and lower estradiol levels in the short-term experimental animals (G-ST). However, at maturity (G-LT), there were no significant differences found in these measures. A delay in the timing of puberty significantly attenuated the development of femoral bone strength at 6 weeks of age. Peak moment, yield moment and stiffness in the G-ST group were all significantly less than the C-ST group. Cortical width was significantly attenuated due to the increased percentage of marrow area per total bone area in the G-ST group. However, femoral bone strength was recovered at maturity (G-LT). In summary, a transient delay in pubertal timing has short-term effects on bone strength development. In the current animal model of delaying puberty through GnRH antagonist injections, there appears to be no long-term effects on bone strength.

Method for cortical bone structural analysis from magnetic resonance images

RATIONALE AND OBJECTIVES

Quantitative evaluation of cortical bone architecture as a means to assess bone strength typically is accomplished on the basis of images obtained by means of dual-energy X-ray absorptiometry (DXA) or computed tomography. Magnetic resonance (MR) imaging has potential advantages for this task in that it allows imaging in arbitrary scan planes at high spatial resolution. However, several hurdles have to be overcome to make this approach practical, including resolution of issues related to nonlinear receive coil sensitivity, variations in marrow composition, and the presence of periosteal isointense tissues, which all complicate segmentation. The aim of this study is to develop MR acquisition and analysis methods optimized for the detection of cortical boundaries in such complex geometries as the femoral neck.

MATERIALS AND METHODS

Cortical boundary detection is achieved by radially tracing intensity profiles that intersect the periosteal and endosteal boundaries of bone. Profiles subsequently are normalized to the intensity of the marrow signal, processed with morphologic image operators, and binarized. The resulting boundaries are mapped back onto the spatial image, and erroneous boundary points are removed. From the detected cortical boundaries, cortical cross-sectional area and thickness are computed. The method was evaluated on cortical bone specimens and human volunteers on the basis of high-resolution images acquired at a 1.5-Tesla field strength. To assess whether the method is sensitive to detect the expected dependencies of cortical parameters in weight-bearing bone on overall habitus, 10 women aged 46-73 years (mean age, 56 years) underwent the cortical imaging protocol in the proximal femur, and results were compared with DXA bone mineral density parameters of the hip and spine.

RESULTS

Reproducibility was approximately 2%. Double oblique images of the femoral neck in the 10 women studied showed that cortical cross-sectional area correlated strongly with height (r = 0.88; p = .0008), whereas cortical diameter versus age approached significance (r = 0.61; p = .06). Measurements in specimens of some cortical parameters indicated resolution dependence. However, note that specimen ranking within each parameter remained constant across all resolutions studied.

CONCLUSION

Data suggest the new method to be robust and applicable on standard clinical MR scanners at arbitrary anatomic locations to yield clinically meaningful quantitative results.

Measurement of midfemoral shaft geometry: repeatability and accuracy using magnetic resonance imaging and dual-energy X-ray absorptiometry

Although macroscopic geometric architecture is an important determinant of bone strength, there is limited published information relating to the validation of the techniques used in its measurement. This study describes new techniques for assessing geometry at the midfemur using magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry (DXA) and examines both the repeatability and the accuracy of these and previously described DXA methods. Contiguous transverse MRI (Philips 1.5T) scans of the middle one-third femur were made in 13 subjects, 3 subjects with osteoporosis. Midpoint values for total width (TW), cortical width (CW), total cross-sectional area (TCSA), cortical cross-sectional area (CCSA), and volumes from reconstructed three-dimensional (3D) images (total volume [TV] and cortical volume [CVol]) were derived. Midpoint TW and CW also were determined using DXA (Lunar V3.6, lumbar software) by visual and automated edge detection analysis. Repeatability was assessed on scans made on two occasions and then analyzed twice by two independent observers (blinded), with intra- and interobserver repeatability expressed as the CV (CV +/- SD). Accuracy was examined by comparing MRI and DXA measurements of venison bone (and Perspex phantom for MRI), against "gold standard" measures made by vernier caliper (width), photographic image digitization (area) and water displacement (volume). Agreement between methods was analyzed using mean differences (MD +/- SD%). MRI CVs ranged from 0.5 +/- 0.5% (TV) to 3.1 +/- 3.1% (CW) for intraobserver and 0.55 +/- 0.5% (TV) to 3.6 +/- 3.6% (CW) for interobserver repeatability. DXA results ranged from 1.6 +/- 1.5% (TW) to 4.4 +/- 4.5% (CW) for intraobserver and 3.8 +/- 3.8% (TW) to 8.3 +/- 8.1% (CW) for interobserver variation. MRI accuracy was excellent for TV (3.3 +/- 6.4%), CVol (3.5 +/- 4.0%), TCSA (1.8 +/- 2.6%), and CCSA (1.6 +/- 4.2%) but not TW (4.1 +/- 1.4%) or CW (16.4 +/14.9%). DXA results were TW (6.8 +/- 2.7%) and CW (16.4 +/- 17.0%). MRI measures of geometric parameters of the midfemur are highly accurate and repeatable, even in osteoporosis. Both MRI and DXA techniques have limited value in determining cortical width. MRI may prove valuable in the assessment of surface-specific bone accrual and resorption responses to disease, therapy, and variations in mechanical loading.

Bone densities and bone size at the distal radius in healthy children and adolescents: a study using peripheral quantitative computed tomography

Peripheral quantitative computed tomography (pQCT) has the ability to improve the diagnostic utility of densitometry in children and adolescents, because bone size and volumetric bone mineral density (vBMD) can be measured independently. Nevertheless, detailed reference data are lacking. We therefore performed pQCT (XCT-2000 scanner, Stratec, Inc., Pforzheim, Germany) at the distal radius in 371 healthy children, adolescents, and young adults (185 males and 186 females, ages 6-23 years) and in 107 of their parents (19 men and 88 women, ages 29-40 years). Total vBMD, trabecular, and "cortical + subcortical" vBMD as well as cross-sectional area (CSA) were determined at the "4% site" of the distal radius. This location was defined as the site whose distance to the most distal portion of the growth plate or to the radial articular surface corresponded to 4% of the forearm length. In both genders, total vBMD remained stable between 6 and 15 years of age and then increased by 30% in girls and by 46% in boys. Regarding pubertal development, total vBMD remained almost constant throughout pubertal stages 1-4 and thereafter increased in both genders. Trabecular vBMD did not change with age in girls, whereas in boys an increase with age of about 10% was noted after 15 years of age. Males had higher trabecular vBMD than females. This gender difference increased from 6% in prepubertal children to 23% in adults. The variation with age and pubertal stage in "cortical + subcortical" vBMD-cort was similar to that of total vBMD. CSA roughly doubled between 6 and 15 years of age in both genders. In conclusion, the availability of this reference material will provide a basis for the use of pQCT in the assessment of pediatric bone diseases.