Bone mineral and soft tissue measurements by dual-energy X-ray absorptiometry during growth

"Sex" and body region effects on bone mineralization in male pigs

Lameness in pigs is one of the major reasons for culling and early losses in pigs. This can be linked to osteoporosis due to pathologic alterations in bone mineral density (BMD) or bone mineral content (BMC) and may also be linked to the sex. Dealing with the ban on piglet castration without anaesthesia in Germany 2021, we have three male “sex” types: entire boars (EB), immunocastrated boars (IB), and surgically castrated boars (SB). The hypothesis of the present study is that BMC or BMD varies between different male sex types. If sex has an effect on bone mineralization (BMC or BMD) and if this affects leg health, it could result in more lameness and problems during fattening in the negatively affected sex type. The present study evaluated bone mineralization (in terms of BMD and BMC) and body composition traits using dual-energy X-ray absorptiometry (DXA) three times during growth at 30, 50, and 90 kg live body weight. Nine body regions were analysed for bone mineral traits and compared for different male sex types and the fattening season. Significant differences were found regarding BMD (and BMC) among EB, IB, and SB for whole-body BMD (BMC). Additionally significant differences were found in the front and lower hind limbs, where SB showed a significantly higher BMD compared to EB, with IB in between. Additionally regional differences were detected among the groups. Further studies are needed to evaluate the effect of these differences in bone mineralization on leg health.

Reference data and percentile curves of body composition measured with dual energy X-ray absorptiometry in healthy Chinese children and adolescents

Measurements of body composition by dual-energy X-ray absorptiometry (DXA) have evident value in evaluating skeletal and muscular status in growing children and adolescents. This study aimed to generate age-related trends for body composition in Chinese children and adolescents, and to establish gender-specific reference percentile curves for the assessment of muscle-bone status. A total of 1541 Chinese children and adolescents aged from 5 to 19 years were recruited from southern China. Bone mineral content (BMC), lean mass (LM) and fat mass (FM) were measured for total body and total body less head (TBLH). After 14 years, total body LM was significantly higher in boys than girls (p < 0.001). However, total body FM was significantly higher in girls than boys in age groups 13-19 years (p < 0.01). Both LM and FM were consistent independent predictors of total body and subcranial bone mass in both sexes, even after adjustment for the well-known predictors of BMC. The results of multiple linear regression identified LM as the stronger predictor of total body and subcranial skeleton BMC while the fat mass contributed less. For all the subjects, significant positive correlations were observed between total body LM, height, total body BMC and subcranial BMC (p < 0.01). Subcranial BMC had a better correlation with LM than total body BMC. We have also presented gender-specific percentile curves for LM-for-height and BMC-for-LM which could be used to evaluate and follow various pediatric disorders with skeletal manifestations in this population.

Age trends of bone mineral density and percentile curves in healthy Chinese children and adolescents

The clinical utility of dual-energy X-ray absorptiometry (DXA) measurement requires appropriate normative values, designed to be diverse with respect to age, gender and ethnic background. The purpose of this study was to generate age-related trends for bone density in Chinese children and adolescents, and to establish a gender-specific reference database. A total of 1,541 Chinese children and adolescents aged from 5 to 19-years were recruited from southern China. Bone mineral density (BMD), bone mineral content (BMC), and bone area (BA) were measured for the total body (TB) and total body less head (TBLH). The height-for-age, height-for-BA, and BMC-for-BA percentile curves were developed using the least mean square method. TB BMD and TBLH BMD were highly correlated. After 18 years, TB BMD was significantly higher in boys than girls. For TB BMC and TBLH BMC, gender differences were found in age groups 12 years and 16-19 years; however, the TBLH BMD was significantly different between genders >16 years. The head region accounted for 13-52 and 16-49 % of the TB BMC in boys and girls, respectively. Furthermore, the percentages were negatively correlated with age and height. This study describes a gender-specific reference database for Chinese children and adolescents aged 5-19 years. These normative values could be used for clinical assessment in this population.

The muscle-bone unit of peripheral and central skeletal sites in children and young adults

Changes and gender differences in the muscle bone unit at different skeletal sites were investigated during pubertal development. Females accrued greater BMC in relation to muscle compared to males; these gender differences were greater after adjustment for height and regional fat mass.

PURPOSE

To describe changes and gender differences in the muscle-bone unit at different skeletal sites during pubertal development.

METHODS

Four hundred forty-two children aged 5-18 years were studied. Measurements of bone mineral content (BMC), lean mass (LM) and fat mass of the whole body (WB), legs, arms and lumbar spine were obtained from dual-energy X-ray absorptiometry. Peripheral quantitative computed tomography was used to measure BMC of the radius diaphysis and cross-sectional muscle area (CSMA) of the mid-forearm. These measurements were used to describe differences between, and within, genders at each pubertal stage in BMC accrual relative to muscle, both before and after adjustment for height, regional fat and muscle at central and peripheral skeletal sites.

RESULTS

In males, there were significant increases in adjusted WB and leg BMC at the end of pubertal development. Unadjusted and adjusted lumbar spine BMC increased at the onset of, and at the end, of puberty. Radius BMC increased at most pubertal stages. In females, there were increases in unadjusted and adjusted whole body BMC at late puberty, in leg BMC at the onset of puberty and at pubertal stage four. Unadjusted arm BMC increased at most pubertal stages; however, after adjustment, an increase occurred at pubertal stage four. Both adjusted and unadjusted lumbar spine BMC increased at pubertal stage four. Unadjusted radius BMC increased at most pubertal stages. Females had greater BMC at all skeletal sites, compared to males, except at the radius, where adjusted BMC was greater in males at pubertal stage four.

CONCLUSIONS

Males and females accrue more BMC in relation to lean mass at multiple skeletal sites as puberty proceeds. Females accrue more BMC in relation to lean mass, in comparison to males, at most skeletal sites.

Z-score comparability of bone mineral density reference databases for children

PURPOSE

The diversity of pediatric dual-energy x-ray absorptiometry (DXA) bone mineral density (BMD) reference databases raises questions as to whether they are interchangeable in their application. This study examined the comparability of BMD Z-scores generated from the largest available Hologic DXA databases, applied on BMD results of a large series of unselected pediatric patients.

METHODS

A total of 2027 BMD scans were extracted from Hologic QDR-4500A machines. Age- and sex-specific BMD Z-scores of children aged 8-17 yr, calculated from six Hologic databases, were compared for lumbar spine (LS) and total body (TB). The final dataset included 708 scans (307 of girls).

RESULTS

BMD Z-scores calculated from the six databases were highly correlated but differed significantly (P < 0.001) in both scan regions. Interdatabase Z-score differences (boys/girls, respectively) were up to 0.54/0.55 for LS and 1.0/0.83 for TB. These differences also varied significantly among age groups. In girls, the percentage of LS BMD Z-scores of -2 or below ("low BMD for age") varied between 15.4 and 27.9% (P < 0.012). The percentage of TB BMD Z-scores of -2 or below varied similarly in boys (P < 0.009).

CONCLUSIONS

Clinically relevant differences in BMD Z-scores exist between the Hologic databases, revealing a significant potential for misdiagnosis. Ideally, Z-scores should be calculated using model-, brand-, and software-specific reference curves for age, sex, and ethnic group. However, our results can be used to estimate converted values. There are other differences in children's bone mass, shape, strength, and body size that are not detected by DXA.

Skeletal and muscular status in juveniles with GFD treated clinical and newly diagnosed atypical celiac disease--preliminary data

Undiagnosed and untreated celiac disease (CD) constitutes an increasing skeletal health problem due to its association with low bone density and fractures. Examinations of skeletal status in children using dual-energy X-ray absorptiometry (DXA) are prone to size-related misinterpretation. In contrary, the analysis of muscle-bone relationship seems to limit a possibility of misdiagnosis because skeletal status is evaluated from the functional perspective. The study was aimed to assess skeletal status of children suffering from CD with the use of muscle-bone functional algorithm. The study group comprised 29 celiac patients (13.7yr+/-2.9) on gluten-free diet (GFD), and 24 newly diagnosed atypical celiac patients, including subgroup with normal height (n=14; 12.6yr+/-3.9) and subgroup with short stature (n=10; 12.2yr+/-2.9). Muscular and skeletal status was evaluated by DXA (DPX-L, GE). Anthropometry, total body bone mineral density (TBBMD, g/cm(2)). and total body bone mineral content (TBBMC, g) as well as lean body mass (LBM, g) were evaluated. Muscle-bone interactions were estimated using TBBMC/LBM ratio. Previously established references for healthy controls were used for the calculation of Z-scores (age-matched) and SD-scores (height-matched). GFD treated celiacs and atypical celiacs with normal body height had TBBMD, TBBMC, LBM, and TBBMC/LBM ratio Z-scores and SD-scores within normal range for healthy controls. In contrary, atypical celiacs with short stature had significantly lower Z-scores for TBBMD (-2.3+/-0.4), TBBMC (-2.1+/-0.3), LBM (-1.4+/-0.3). and TBBMC/LBM ratio (-2.3+/-0.6) when compared to respective values observed in GFD treated celiacs (p<0.001, p<0.001, p<0.05, p<0.01) and atypical celiacs with normal height (p<0.01, p<0.01, p<0.05, p<0.01). When body-height matching of DXA data was used to limit the influence of body size, the atypical celiacs with short stature had SD-scores for TBBMD (-1.3+/-0.7), TBBMC (-1.3+/-0.6), and LBM (+0.8+/-0.3) not significantly different from the corresponding SD-scores obtained in the remaining 2 groups. Nevertheless, short stature in atypical celiacs still coincided with significantly lower TBBMC/LBM ratio SD-score of -1.9+/-0.7 when compared to values observed in GFD treated celiacs (+0.04+/-0.2; p<0.05) and atypical celiacs with normal height (-0.4+/-0.2; p<0.05). GFD regime in classic celiacs corresponded with physiological values of DXA assessed indicators of bone and muscle status as well as normal muscle-bone interactions. Untreated atypical celiacs may present a broad spectrum of heterogeneous abnormalities from normal to markedly depressed TBBMC/LBM ratio values pointing on the marked imbalance between TBBMC and LBM.

Idiopathic juvenile osteoporosis--an analysis of the muscle-bone relationship

INTRODUCTION

Idiopathic Juvenile Osteoporosis (IJO), a disease of unknown etiology, manifests typically by pain, bone deformities and fractures. Due to limits in BMD data interpretation, evaluation of the muscle-bone functional unit has recently been proposed as a means to assess the general competence of the skeleton. The aim of this study was to evaluate skeletal status during the acute phase of IJO and during recovery from the disease in relation to muscles.

MATERIALS AND METHODS

The study population comprised 61 IJO children, including 34 girls (mean age: 13.6+/-3.1 years; range: 7-18) and 27 boys (14.3+/-3.3; 5-18 years). DXA total body (TB) and lumbar spine (S) bone mineral content (BMC) and density (BMD) were measured. Lean body mass (LBM) was employed to calculate SBMC/LBM, TBBMC/LBM, body height (BH)/LBM and LBM/body weight (BW) ratios. Previously established references for healthy controls were utilized for the calculation of Z-score values in IJO cases in respect to phase of the disease.

RESULTS

IJO patients had significantly decreased Z-score values for TBBMD, SBMD, SBMC/LBM and TBBMC/LBM ratios but not for the LBM and BH/LBM or LBM/BW ratios. During the acute phase IJO girls had mean Z-scores for TBBMD and SBMD of -2.49+/-0.61 and -3.27+/-1.03, respectively, which were significantly lower than Z-scores during the recovery phase: -0.90+/-0.66, -1.38+/-0.95 (p<0.0001). IJO boys during the acute phase had Z-scores of -2.08+/-0.65 and -2.75+/-1.19 for TBBMD and SBMD, respectively, which were significantly lower than those during the recovery phase (-0.51+/-1.04 and -1.39+/-1.49; p<0.0001). Further, during the acute phase, TBBMC/LBM Z-scores of -2.95+/-1.15 and -2.56+/-1.49 were noted in girls and boys, respectively; the corresponding SBMC/LBM Z-scores were -2.66+/-1.07 and -2.22+/-1.62. During the recovery from IJO, TBBMC/LBM and SBMC/LBM Z-scores of -1.07+/-0.99 and -0.91+/-1.16 and of -1.15+/-1.40 and -0.68+/-1.45 were noted in girls and boys, respectively, and all were significantly higher than those during the acute phase (p<0.0001).

CONCLUSIONS

The results of this study indicate that IJO is a bone disorder characterized by an imbalanced muscle-bone relationship and fractures at onset and during the acute phase and by at least a partial recovery without bone pain and new fractures. Implementation of the BH/LBM, TBBMC/LBM and SBMC/LBM ratios to the armamentarium of pediatricians diagnosing bone disorders will provide mechanically meaningful data for diagnostic purposes and, hopefully, for proper therapeutic decisions.

Skeletal developmental effects of selective and nonselective cyclooxygenase-2 inhibitors administered through organogenesis and fetogenesis in Wistar CRL:(WI)WUBR rats

Cyclooxygenase (COX) inhibitors are the most commonly ingested drugs. The aim of the study was to evaluate the prenatal skeletal effect of selective (DFU) and nonselective (tolmetin, ibuprofen, piroxicam) COX-2 inhibitors. All the tested compounds were administered intragastrically to pregnant Wistar rats from 7 to 21 gestation day. The initial dose was set at 8.5mg/kg/dose for tolmetin and ibuprofen, 0.3 and 0.2mg/kg/dose for piroxicam and DFU. The middle dose was increased 10-times. The highest dose, except for ibuprofen, was elevated 100-times. The highest dose for ibuprofen was set at 200mg/kg/dose. Tolmetin and ibuprofen were administered three times a day. Piroxicam and DFU were dosed once daily. After routine teratological examinations, extremities of randomly selected 21-day-old fetuses were taken for histological, immunohistochemical and molecular studies. The proximal femoral epiphyses were separated and their ultrastructure evaluated. The expression of genes coding cytokines (IL-1alpha, IL-1beta, IL-6, TNF-alpha, TNF-beta) and proteins (COX-1, COX-2, cathepsin K, collagen types I, II and X; osteocalcin, osteopontin) was evaluated in femoral epiphyses by RNase Protection Assay and/or immunohistochemically. The articulate development was checked histologically and found undisturbed in any of the experimental groups. The epiphysis of the 21-day-old fetuses, presented physiological expression of COX-1 and COX-2, as well as cathepsin K, collagen types I, II and X; osteopontin, osteocalcin and TNF-alpha. Increased developmental skeletal variation was noted in groups exposed to the highest dose of nonselective drugs. Unlike the increased number of skeletal variations observed in fetuses exposed to highest doses of nonselective compounds, both groups of COX inhibitors did not disturb joint formation and morphology of femoral epiphyses when administered even in high maternal toxic doses.

Reference values for the indicators of skeletal and muscular status of healthy Polish children

Dual-energy X-ray absorptiometry (DXA) results are affected by the growth- and maturation-based anthropometric variances during childhood and adolescence. To address this issue, anthropometric variables were implemented to normative DXA values for the total body (TB) and lumbar spine (S) data obtained from a cross-sectional sample of 562 healthy Caucasian children (278 females) aged 5 to 18 yr who were measured using a pencil-beam DXA device (DPX-L; GE Lunar). Across age or body height (BH) groups, female and male values for TB bone mineral content (TBBMC) (g), TB bone mineral density (TTBMD) (g/cm(2)), SBMC (g), SBMD (g/cm(2)), lean body mass (LBM) (g), TBBMD/LBM (g/g), and SBMC/LBM [(g/g) x 100)] were assessed and compared using ANOVA and t-tests. There was no gender difference in TBBMC until age 16 and in TBBMD until age 17; thereafter, male values were significantly higher. At 12 to 13 yr of age, female SBMD values were significantly higher than male. The BH matching revealed lack of major gender-related differences in TBBMC or TBBMD values across whole height range, whereas at heights of 150 to 175 cm, females had generally higher values of SBMC and SBMD than male counterparts. Further, the LBM values and calculated TBBMC/LBM and SBMC/LBM ratios were considered as the muscle and muscle-bone indicators, respectively. The muscle-bone relationship analysis using LBM and TBBMC/LBM and SBMC/LBM values revealed age- and BH-related differences between genders. At LBM values of 32 kg and above and ages 14 yr and above for the whole skeleton as well as 12 yr and above for spine segment, females accrued significantly more BMC for the LBM unit than males. In order to properly assess children who might be at risk for low bone mass, we provide reference values for BMC and BMD of usually studied sites, expanded by muscle-bone relationship indicators owing to reduced diagnostic errors and distinguished bone disorders.

Strategic approaches to osteoporosis in transplantation

Recipients of stem cell transplantation are at risk for osteopenia and osteoporosis. Longitudinal studies performed in adults have shown that significant bone demineralization occurs following myeloablative therapy and subsequent immune suppression. Among children and adolescents, cross-sectional analyses indicate that younger patients are also at risk for long-term bone toxicity. Strategies to detect and manage this disorder in pediatric SCT recipients are presented.

Interpretation of whole body dual energy X-ray absorptiometry measures in children: comparison with peripheral quantitative computed tomography

The assessment of bone health in children requires strategies to minimize the confounding effects of bone size on dual energy X-ray absorptiometry (DXA) areal bone mineral density (BMD) results. Cortical bone composes 80% of the total skeletal bone mass. The objective of this study was to develop analytic strategies for the assessment of whole body DXA that describe the biomechanical characteristics of cortical bone across a wide range of body sizes using peripheral quantitative computed tomography (pQCT) measures of cortical geometry, density (mg/mm(3)), and strength as the gold standard. Whole body DXA (Hologic QDR 4500) and pQCT (Stratec XCT-2000) of the tibia diaphysis were completed in 150 healthy children 6-21 years of age. To assess DXA and pQCT measures relative to age, body size, and bone size, gender-specific regression models were used to establish z scores for DXA bone mineral content (BMC) for age, areal BMD for age, bone area for height, bone area for lean mass, BMC for height, BMC for lean mass, and BMC for bone area; and for pQCT, bone cross-sectional area (CSA) for tibia length and bone strength (stress-strain index, SSI) for tibia length. DXA bone area for height and BMC for height were both strongly and positively associated with pQCT CSA for length and with SSI for length (all P < 0.0001), suggesting that decreases in DXA bone area for height or DXA BMC for height represent narrower bones with less resistance to bending. DXA BMC for age (P < 0.01) and areal BMD (P < 0.05) for age were moderately correlated with strength. Neither DXA bone area for lean mass nor BMC for lean mass correlated with pQCT CSA for length or SSI for length. DXA BMC for bone area was weakly associated with pQCT SSI for length, in females only. Therefore, normalizing whole body DXA bone area for height and BMC for height provided the best measures of bone dimensions and strength. DXA BMC normalized for bone area and lean mass were poor indicators of bone strength.

The relationship between muscle size and bone geometry during growth and in response to exercise

As muscles become larger and stronger during growth and in response to increased loading, bones should adapt by adding mass, size, and strength. In this unilateral model, we tested the hypothesis that (1) the relationship between muscle size and bone mass and geometry (nonplaying arm) would not change during different stages of puberty and (2) exercise would not alter the relationship between muscle and bone, that is, additional loading would result in a similar unit increment in both muscle and bone mass, bone size, and bending strength during growth. We studied 47 competitive female tennis players aged 8-17 years. Total, cortical, and medullary cross-sectional areas, muscle area, and the polar second moment of area (I(p)) were calculated in the playing and nonplaying arms using magnetic resonance imaging (MRI); BMC was assessed by DXA. Growth effects: In the nonplaying arm in pre-, peri- and post-pubertal players, muscle area was linearly associated BMC, total and cortical area, and I(p) (r = 0.56-0.81, P < 0.09 to < 0.001), independent of age. No detectable differences were found between pubertal groups for the slope of the relationship between muscle and bone traits. Post-pubertal players, however, had a higher BMC and cortical area relative to muscle area (i.e., higher intercept) than pre- and peri-pubertal players (P < 0.05 to < 0.01), independent of age; pre- and peri-pubertal players had a greater medullary area relative to muscle area than post-pubertal players (P < 0.05 to < 0.01). Exercise effects: Comparison of the side-to-side differences revealed that muscle and bone traits were 6-13% greater in the playing arm in pre-pubertal players, and did not increase with advancing maturation. In all players, the percent (and absolute) side-to-side differences in muscle area were positively correlated with the percent (and absolute) differences in BMC, total and cortical area, and I(p) (r = 0.36-0.40, P < 0.05 to < 0.001). However, the side-to-side differences in muscle area only accounted for 11.8-15.9% of the variance of the differences in bone mass, bone size, and bending strength. This suggests that other factors associated with loading distinct from muscle size itself contributed to the bones adaptive response during growth. Therefore, the unifying hypothesis that larger muscles induced by exercise led to a proportional increase in bone mass, bone size, and bending strength appears to be simplistic and denies the influence of other factors in the development of bone mass and bone shape.

Importance of lean mass in the interpretation of total body densitometry in children and adolescents

OBJECTIVE

Most studies that use total body dual energy x-ray absorptiometry (DEXA) in children rely on areal bone mineral density (BMD=bone mineral content [BMC]/bone area [BA]) and compare the output with age- and sex-specific normative data. Because this approach is prone to size-related misinterpretation, this study focuses on the interrelations among BMC, body size (height), and lean tissue mass (LTM).

STUDY DESIGN

This cross-sectional study presents normative total body LTM data in relation to height and BMC for 459 healthy white subjects (249 female), 3 to 30 years of age. Guidelines for DEXA interpretation in children are provided and illustrated for patients with growth hormone deficiency (n=5) and anorexia nervosa (n=5).

RESULTS

LTM/height tended to be greater in male than in girls. The BMC/LTM ratio was greater in female than in boys (P<.001), even after adjustment for age and height. Sex-specific reference curves were created for LTM/height, the BMC/LTM ratio, BA/height, and BMC/BA.

CONCLUSIONS

We recommend that total body DEXA in children should be interpreted in 4 steps: (1) BMD or BMC/age, (2) height/age, (3) LTM/height, and (4) BMC/LTM ratio for height. This allows differentiation of the origin of a low BMD or BMC/age, for example, short stature and primary, secondary, and mixed bone defects.