Assessment of bone mass following renal transplantation in children

Throughout childhood and adolescence, skeletal growth results in site-specific increases in trabecular and cortical dimensions and density. Childhood osteoporosis can be defined as a skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture. Pediatric renal transplant recipients have multiple risk factors for impaired bone density and bone strength, including pre-existing renal osteodystrophy, delayed growth and development, malnutrition, decreased weight-bearing activity, inflammation, and immunosuppressive therapies. Dual energy X-ray absorptiometry (DXA) is the most-common method for the assessment of skeletal status in children and adults. However, DXA has many important limitations that are unique to the assessment of bone health in children. Furthermore, DXA is limited in its ability to distinguish between the distinct, and sometimes opposing, effects of renal disease on cortical and trabecular bone. This review summarizes these limitations and the difficulties in assessing and interpreting bone measures in pediatric transplantation are highlighted in a review of select studies. Alternative strategies are presented for clinical and research applications.This work was presented in part at the IPNA Seventh Symposium on Growth and Development in Children with Chronic Kidney Disease: The Molecular Basis of Skeletal Growth, 1–3 April 2004, Heidelberg. Germany     

Differences in mineral homeostasis, volumetric bone mass and femoral neck axis length in black and white South African women

In South Africa, appendicular and lumbar spine bone mineral density (BMD) have been found to be similar in black and white women. However, femoral BMD has been found to be higher in black than in white women. Two different techniques were used to recalculate BMD to eliminate the possible confounding influence of ethnic differences in height on areal BMD measurements. Volumetric bone mineral apparent density (BMAD) values were calculated and bone mineral content (BMC) was corrected for body and bone size. This report analyses differences in BMD (corrected for height and weight), BMAD, BMC (corrected for body and bone size), femoral neck axis length (FNAL), mineral homeostasis and bone turnover (BT) in a group of 20 to 49-year-old premenopausal (105 whites and 74 blacks) and 45 to 64-year-old postmenopausal (50 whites and 65 blacks) female South African nurses. The corrected BMD and BMC findings were congruous, showing that both pre- and postmenopausal blacks and whites have similar distal radius and lumbar spine bone mass but that whites have lower femoral neck bone mass than blacks. In contrast, BMAD findings suggest that pre- and postmenopausal whites have lower bone mass at the lumbar spine and femoral neck than blacks but similar bone mass at the distal radius to blacks. There is a greater rate of decline in BMD in postmenopausal whites than in blacks. BMD at the femoral neck was 12.1% lower in premenopausal whites and 16.5% lower in postmenopausal whites than in blacks. There was a positive association between femoral neck BMD and weight in premenopausal blacks (R ²=0.5,p=0.0001) but not in whites. Blacks had shorter FNAL than whites in both the pre- and postmenopausal groups. Blacks had lower serum 25-hydroxyvitamin D (25-(OH)D) and higher 1,25-dihydroxyvitamin D (1,25-(OH)₂D) levels than whites. There were no ethnic differences in biochemical markers of bone formation (serum alkaline phosphatase and osteocalcin) or bone resorption (urine hydroxyproline and pyridinoline), or in dietary calcium intake in either the pre- or postmenopausal groups. In the postmenopausal group, whites had higher ionized serum calcium (p=0.003), similar serum albumin, lower serum parathyroid hormone (p=0.003) and higher urinary calcium excretion (p=0.0001) than blacks. These results suggest that the higher peak femoral neck BMD in South African blacks than in whites might be determined by greater weight-bearing in blacks and that the significantly lower femoral neck BMD in postmenopausal whites than in blacks is determined by lower peak femoral neck BMD and a faster postmenopausal decline in BMD in whites. The higher incidence of femoral neck fractures in South African whites than in blacks is probably determined by the lower femoral neck BMD and longer FNAL in whites. The greater rate of decline in BMD in postmenopausal whites than in blacks is associated with an increase in urinary calcium excretion in whites. Measurement of biochemical markers of BT has not contributed to the understanding of ethnic differences in BMD and skeletal metabolism in our subjects.     

Gender differences in bone density at different skeletal sites of acquisition with age in Chinese children and adolescents

Bone mass acquisition from different genders and races of children and adolescents may vary. To explore gender- and age-related differences in bone mineral density (BMD) measurements in Chinese children and adolescents, we used the dual-energy X-ray absorptiometry (DXA) bone densitometer to take BMD measurements at the posteroanterior (PA) and lateral spine, hip, and forearm in 1286 healthy children and adolescents, ranging from 6 to 24 years of age. Our results show a correlation between BMD measurements taken from different skeletal sites and from different ages of subjects. Male data were best fit to a power regression model, yielding the largest determinant coefficients (R ²), whereas S regression was the best fitting model for females. In individuals younger than 17 years of age, the rate of BMD accumulation in the PA spine is more rapid in females than in males, whereas in individuals older than 19 years of age, the converse was found to be true. In children younger than 14 years of age, BMD measurements, taken from the lateral spine, the neck and trochanter of the femur, and the total hip, correlated with age similarly in both genders. Additionally, in measurements taken from the forearm ultradistal and 1/3 region, BMD measurements from similar ages of both genders are similar. With increasing age, BMD measurements in males become significantly higher than those of females. However, volumetric BMD (vBMD) measurements from both genders show good uniformity at the lateral spine with a near overlap of the two models. Our findings suggest that vBMD acquisition measurements in Chinese children and adolescents show no gender differences, with gender differences only demonstrated in areal BMD (aBMD) measurements taken from different skeletal sites.     

Asynchrony between the rates of standing height gain and bone mass accumulation during puberty

During puberty, the marked increases in both standing height and bone mass appear to be dissociated in time, the former occurring earlier than the latter. However, the age or pubertal stage at which this dissociation is maximal in girls as opposed to boys, and whether this dissociation is similar at all parts of the skeleton, are not clearly established. Standing height and bone mineral mass, as assessed by measuring areal bone mineral density (BMD), at the levels of the lumbar spine, femoral neck and midfemoral shaft, were measured in 98 females and 100 males between the ages of 9 and 19 years twice at a 1-year interval. In males, the greatest difference between height and BMD gains occurred in the 13–14 year age group and was more pronounced for the lumbar spine and femoral neck than for the midfemoral shaft. In females, the greatest difference was detectable at a younger age (11–12 year age group) and appeared to be of a lower magnitude than in males. In both genders, the maximal difference occurred during the period of peak height velocity, which corresponded to the pubertal stages P2-P3. Such a dissociation between the rates of statural growth and mineral mass accrual could define a state of relatively low bone mass and contribute to the higher incidence of fracture known to occur at the age and/or pubertal stage when this dissociation is maximal.     

Comparison of areal and estimated volumetric bone mineral density values between older men and women

We compared areal bone mineral density (BMD) of the total body (TBMD), antero-posterior lumbar spine at L3 (APS), lateral spine at L3 (LS) and femoral neck (FN). In order to understand better the effect of gender-related size differences on BMD, we also compared the estimated volumetric BMD at L3 (VLS) and the femoral neck (VFN). Subjects were asymptomatic women (n=22) and men (n=44) with an age range of 58–79 years. BMD at each site was measured by dual-energy X-ray absorptiometry using a Hologic 2000 in array mode. Results of the statistical analyses (ANOVA) showed the men to have significantly greater BMD at all areal sites [APS, LS (p<0.05); FN (p<0.01); TBMD (p<0.001)]. The two estimated volumetric comparisons, however, showed no gender differences. Results demonstrate how measures from areal BMD measures can be misleading when comparing groups of different size. In older men and women planar measures may overestimate gender differences in BMD.     

Specific evaluation of localized bone mass and bone loss in the rat using dual-energy X-ray absorptiometry subregional analysis

Dual-energy X-ray absorptiometry (DXA), together with the use of ultra-high resolution software, recently appeared as an accurate method for determining bone mineral density (BMD) in the rat. In order to assess the ability of this technique to detect changes in bone mass in the rat rapidly and precisely, we measured BMD at various sites of the femur using DXA subregional analysis. In particular, we studied the BMD of the metaphyseal part of the femur (M-BMD) rich in trabecular bone, and compared the values obtained with the cancellous bone volume measured by histomorphometry. In short-term ovariectomized animals (experiment 1), M-BMD was the only parameter to differentiate statistically between 10 ovariectomized (OVX) and 10 SHAM-operated (SHAM) rats (–11.2%,p<0.01) 9 days after surgery. M-BMD still expressed the greatest variation between OVX and SHAM rats 42 days following ovariectomy (experiment 2) (–16.1%,p<0.001 v –6.2%,p<0.01 for the total femur BMD) and confirmed previous data demonstrating a greater loss of cancellous than cortical bone after cessation of ovarian activity. M-BMD was highly correlated with cancellous bone volume (BV) in normal (r=0.82,p<0.001,n=30), OVX (r=0.77,p<0.001,n=22) and SHAM (r=0.88,p<0.001,n=21) rats. Furthermore, subcutaneous treatment with rat parathyroid hormone fragment (1–34) (r-PTH(1-34)) partially and significantly protected animals from trabecular osteopenia induced by OVX; there was a similar degree of protection of BV and M-BMD (50% and 61% respectively), while BMD of the entire femur achieved complete protection. This M-BMD measurement, specifically reflecting cancellous bone mass as confirmed by the correlation study and the response to PTH treatment, is a sensitve and simple method which can be used to assess any precocious modifications of bone density under physiopathological or therapeutic conditions in experimental rat models of bone loss.     

Accuracy and precision of lumbar bone mineral content by dual-energy X-ray absorptiometry in live female monkeys

Summary Dual-energy X-ray absorptiometry (DXA) was used to determine thein vivo bone mineral content (BMC) of lumbar vertebrae in 20 feral adult female cynomolgus macaques (Macaca fascicularis). The ash weight of the third lumbar vertebra (L3) was compared to the measured L3BMC of thein vivo DXA analyses. Correlation between the estimated L3BMC by DXA and the actual ash weight was significant (r=0.965,P<0.01); however, DXA methodology underestimated ash weight on the average of 6.2%. Correlation was significant between two sequentialin vivo DXA scans (r=0.988,P<0.001). Noninvasivein vivo DXA was a fast, precise, and effective method for measuring the lumbar BMC in female cynomolgus macaques.     

Bone mineral density and bone turnover markers in children with chronic renal failure

Bone mineral density (BMD) at lumbar spine (L₂-L₄) was measured by dual-energy X-ray absorptiometry (DEXA) in 21 children with predialysis chronic renal failure (CRF) and 44 children with end-stage renal failure (ESRF) on regular hemodialysis. BMD results were expressed as Z-scores. Osteopenia was documented in 13 predialysis patients (61.9%) and 26 patients (59.1%) with ESRF. No significant correlation was observed between Z-scores and the duration of CRF or estimated creatinine clearance. In osteopenic children there was a negative correlation between Z-scores and serum phosphorus (r=–0.61, P=0.004), intact parathyroid hormone (iPTH) (r=–0.47, P=0.03), and bone-specific alkaline phosphatase (r=–0.52, P=0.02) and a positive correlation with total calcium (r=0.41, P=0.07) and 25-hydroxycholecalciferol (r=0.53, P=0.02). Osteopenic children who had iPTH values 200 pg/ml were more osteopenic than those who had lower iPTH levels (P=0.006). In conclusion, osteopenia, assessed by DEXA, is frequent in children with CRF. It occurs early irrespective of the duration or the severity of CRF. In children with ESRF the degree of osteopenia is correlated with laboratory markers of renal osteodystrophy and patients with biochemical findings of secondary hyperparathyroidism are more osteopenic than the others.     

体重体成分与骨密度的关系

为了研究体成分与骨密度（ＢＭＤ）之间的关系，因体重与ＢＭＤ显著相关，体成分各个组成相加等于体重，而体成分与ＢＭＤ的关系仍不清楚。方法随机选取２０６名１６～５２岁健康的男女性汉族人，用双能Ｘ射线吸收法（ＤＸＡ）测量ＢＭＤ与体成分，进行ＢＭＤ与体重，体成分的多元线性回归分析。结果体重，瘦组织（ＬＴＭ）与男女性的ＢＭＤ显著正相关，脂肪组织（ＦＴＭ）仅对女性全身，腰椎ＢＭＤ起显著性作用。结论影响男女性ＢＭＤ的体成分中，ＬＴＭ是主要因素，ＦＴＭ仅对女性ＢＭＤ有影响。本文较全面地研究了体成分与ＢＭＤ的关系。     

Computed radiographic absorptiometry and morphometry in the assessment of postmenopausal bone loss

The best method for the diagnosis of osteoporosis and assessment of fracture risk is currently considered to be bone densitometry. The most commonly used dual-energy X-ray absorptiometry (DXA) methods may sometimes not predict bone mass accurately in every skeletal site, are expensive and not widely available. The recent development of computed analysis of a plain radiograph of the hand might provide a practical, inexpensive and rapid method for evaluation of bone mineral status. In this study we evaluated 20 healthy premenopausal and 660 postmenopausal women. In 36 of these subjects a second evaluation was carried out after 2 years of therapy with calcium supplements. The internal and external diameters of the second metacarpal and the metacarpal and ultradistal radial bone density were evaluated using a technical device developed in our laboratory and marketed by NIM, Verona, Italy (Osteoradiometer). The radio-graphic images, captured by a video camera, were digitized and studied by computed analysis. In 150 subjects bone density at the level of the lumbar spine, femur, and ultradistal and proximal radius was also measured by DXA techniques. Both external (D) and internal (d) diameters increase significantly with age and years since menopause (YSM), whereas metacarpal index (D–d/D) and metacarpal and ultradistal radial bone density decrease significantly with age and YSM. The ratio between metacarpal bone mineral content and the cortical area (volumetric metacarpal bone density) did not change with age. Significant correlations were found between radiometric findings and DXA measurements. The best correlation coefficients were between bone density measured at the level of the ultradistal radius by DXA and radiographic absorptiometry. In the 2-year follow-up study, a 4.9% and 6.2% decline in radial metacarpal bone density respectively were observed, but the difference was statistically significant only for the latter. In conclusion, computed radiogrammetry is closely correlated with all DXA measurements and may be useful in screening of large populations, providing a simple, inexpensive and sufficiently precise method for evaluation of bone mineral status. Further studies are warranted for assessing the accuracy of radiogrammetry for longitudinal investigations and its capacity to predict fracture risk.     

Changes in bone mass and bone turnover following tibial shaft fracture

Introduction: Bone loss occurs in the regional bone following tibial shaft fracture. An earlier cross-sectional study showed that measurements made at the metaphyseal region of the tibia using peripheral quantitative computed tomography (pQCT) and the ultradistal region of the tibia using dual-energy X-ray absorptiometry (DXA) were the most responsive at monitoring this bone loss. Biochemical markers of bone turnover enable us to assess the activity of bone formation and resorption during fracture healing. The aim of this longitudinal study was to determine the pattern and distribution of bone loss and bone turnover following a tibial shaft fracture treated with either plaster cast or intramedullary nail. Methods: Eighteen subjects underwent bone mass measurements using DXA at the tibia and hip and quantitative ultrasound (QUS) at the tibia and calcaneus of both limbs at 2 weeks, 8 weeks, 12 weeks and 24 weeks following fracture, with hip and tibia DXA measurements also performed at 52 weeks. Nine of the patients treated with plaster cast had pQCT measurements at the tibia at 24 weeks. We measured three bone formation markers, bone alkaline phosphatase (bone ALP), osteocalcin (OC) and procollagen type 1 N-terminal peptide (PINP), a marker of bone resorption, serum C-telopeptides of type 1 collagen (β-CTX) and a marker of collagen III turnover, procollagen type III N-terminal peptide (PIIINP) at 1 day, 3 days and 7 days and at 2, 4, 8, 12, 16 and 24 weeks following fracture. The greatest bone losses were observed at the ultradistal region of the tibia using DXA (28%, p <0.001) and the metaphyseal region of the tibia using pQCT (26–31%, p <0.001) at 24 weeks. In the hip, the greatest loss was in the trochanter region at 24 weeks (10%, p <0.001). The greatest loss at the calcaneus measured using QUS was for broadband ultrasound attenuation (BUA) measured using CUBA Clinical at 24 weeks (13%, p =0.01). Results: At 1 year, there was a small recovery in bone loss (ultradistal tibia DXA, 20%, p <0.01; trochanter DXA 9%, p <0.001). Bone turnover increased following fracture (PINP +72±21%, p <0.0001, bone ALP +199±22%, p =0.004, β-CTX +105±23%, p <0.0001, all at 24 weeks). There was a smaller +33±10% increase in osteocalcin at 24 weeks. PIIINP concentration peaked at week 8 (+57±9%, p <0.0001). The bone resorption marker β-CTX showed an earlier rise (week 2, 139±33%) than the bone formation markers. Conclusions: We conclude that: (1) bone loss following tibial shaft fracture occurs both proximal and distal to the fracture; (2) the decreased BMD is largest for trabecular bone in the tibia with similar measurements using DXA and pQCT; (3) there is limited recovery of bone lost at the hip and tibia at 1 year; (4) tibial speed of sound (SOS) demonstrated a greater decrease than calcaneal SOS when comparing z -scores; (5) BUA is the QUS variable that shows the biggest decrease of bone mass at the calcaneus; (6) increase in bone turnover occurs following fracture with an earlier increase in bone resorption markers and a later rise in bone formation markers.     

Minimum sample size requirements for bone density precision assessment produce inconsistency in clinical monitoring

Introduction Detection of change during bone mineral density (BMD) monitoring is affected by test precision. The International Society of Clinical Densitometry (ISCD) recommends that each center determine precision error using repeat measurements in 30 subjects (or an equivalent method providing 30 degrees of freedom).Methods We hypothesized that this sample size may be too small for a robust precision estimate, which could affect the performance of BMD monitoring in clinical practice. Replicate measurements of the spine and total hip (198 spine and 193 hip scan pairs) were obtained (interval 6±5 days). The sample was randomly divided into six groups of 30 patients each. Root mean square standard deviation (RMS-SD in g/cm²) and coefficient of variation (RMS-CV in %) precision errors and corresponding 95% least significant change (LSC) were calculated for each group and the pooled sample. LSC cutoffs were applied to 1,420 individuals from the Manitoba Bone Density Program who had follow-up measurements on the same instrument (interval 21±9 months). While the pooled spine RMS-SD was 0.017 and pooled hip RMS-SD was 0.009 g/cm², sample sizes of 30 gave a range of RMS-SD point estimates from 0.012 to 0.021 for the spine and from 0.008 to 0.012 for the hip.Results When the respective LSC cutoffs were applied to the 1,420 follow-up scan pairs, the fraction of patients categorized with significant change in the spine varied from 20.7% to 46.0%; four of the six LSCs based upon 30 subjects gave fractions significantly different from the pooled LSC of 30.7%. Significant change fractions for the hip varied from 31.1% to 51.1%; two of the six LSCs based upon 30 subjects gave fractions significantly different from the pooled LSC of 40.1%. Similar results were obtained using relative precision errors.Conclusion BMD precision studies using a sample size of 30 are insufficient to reliably characterize precision error or change during clinical monitoring.     

Discriminatory ability of bone mass measurements (SPA and DEXA) for fractures in elderly postmenopausal women

Summary We investigated the discriminatory ability of forearm bone mineral content (BMC_arm) measured by single photon absorptiometry (SPA) and spinal bone mineral density (BMD_spine) measured by dual-energy X-ray absorptiometry (DEXA) in 387 elderly postmenopausal women. Of these, 22 had never sustained a fracture (normal), 91 had had less than three vertebral wedge fractures (mild), 51 had experienced a peripheral fracture (moderate), and 24 had had more than three vertebral wedge or compression fractures (severe). BMC_arm exceeded BMD_spine slightly in the ability to discriminate the mild and moderate groups (P< 0.01–0.001), whether calculations were performed on raw values or the Z-scores compared with premenopausal women. Receiver operating (ROC) analysis showed that at every cutoff level BMC_arm had a similar ability as BMD_spine to discriminate between the vertebral fracture (mild and severe) groups and healthy premenopausal and nonfractured postmenopausal women (normal), whereas BMC_arm had a significantly higher discriminatory ability of peripheral fractures (P< 0.05) (moderate) group compared with premenopausal women. We conclude that SPA and DEXA are equally capable as diagnostic procedures in women with established osteoporosis.     

Bone mineral density and bone histomorphometry in children on long-term dialysis

Bone mineral density (BMD) at the lumbar vertebrae (L(1)-L(4)) was assessed by dual-energy X-ray absorptiometry (DXA) in 20 children with chronic kidney disease (CKD) on dialysis, and its results were compared with bone biopsy and biochemical parameters. Biopsy specimens provided evidence of hyperparathyroid bone disease in eight cases (40%), and low bone turnover in 12 (60%). For BMD, expressed as Z-scores relative to normal, median Z-scores were -1.05 (range -2.36 to 1.06) for hyperparathyroid patients and -1.05 (range -4.40 to -0.03) for low bone turnover patients, with no statistical differences between groups (P = 0.512). In relation to BMD, of the whole sample, five (25%) had a Z-score under -2.0. When it was corrected for height, BMD was in the normal range. Additionally, there were no significant differences in single samples of serum calcium, alkaline phosphatase, phosphorus and intact parathyroid hormone (PTH) between groups with high or low bone turnover. Assessment of nutritional status, through height/age, showed that ten patients had Z-scores below -2.0 (median -2.12, range -7.13 to 0.73). In conclusion, renal osteodystrophy (ROD) seems to have a high prevalence among CKD pediatric patients, although only approximately a quarter of them developed changes in BMD. In children with CKD, measurements of bone mineral density may not be used for classification of various forms of ROD.     

Exercise and oral contraceptive use suppress the normal age-related increase in bone mass and strength of the femoral neck in women 18-31 years of age

Women who exercise during their second and third decades may increase their peak bone mass and lower their eventual risk for postmenopausal fracture. However, the effects of exercise in younger women can be modulated by the use of oral contraceptives, which may prevent the normal accretion of bone mass that would otherwise occur. We hypothesized that exercise intervention in young adult women would significantly increase both bone mass and the bending rigidity of the femoral neck. We further hypothesized that exercise intervention in the presence of oral contraceptive use would have a negative effect on bone mass and bending rigidity. Women 18–31 years of age (n = 123) were classified by oral contraceptive use (OC, NOC) and age (18–23, 24–31 years), and then randomized into exercise or nonexercise groups. The exercise protocol consisted of three sessions/week of aerobic and nonaerobic exercises, and continued for 2 years. Each 6 months, the femoral neck of each subject was scanned using a Lunar dual-energy X-ray absorptiometry (DEXA) scanner, and bone mineral content, density and geometric information were used to calculate estimated stresses and bending rigidity at the hip. Percent changes from baseline were analyzed using two-way analysis of variance (ANOVA) at 6, 12, 18, and 24 months. Women who neither exercised nor took oral contraceptives (NE/NOC) had the greatest percentage increases in cross-sectional area (4.98 ± 2.29%), cross-sectional moment of inertia (9.45 ± 2.37%), total bone mineral density (2.07 ± 2.09%), fracture index (8.03 ± 2.03%), and safety factor (20.03 ± 5.79%) over the 24 month exercise program. Women who exercised and did not take oral contraceptives (E/NOC) declined on most variables related to femoral strength and bone mass, whereas those women who took oral contraceptives were usually intermediate between NE/NOC and E/NOC, whether they exercised or not. These data show that either exercise or OC use is associated with a suppression of the normal increase in bone mass and mechanical strength in the femoral neck in women 18–31 years old, but the combination of exercise and OC use appears to have a less suppressive effect.     

Sex Differences in Bone Size and Bone Mineral Density Exist before Puberty. The Copenhagen School Child Intervention Study (CoSCIS)

Background The aim of this study was to provide normative data of bone mineral density (BMD; g/cm²) of the forearm and the calcaneus, evaluated by peripheral dual X ray absorbtiometry (DXA), in children aged 6 to 7 years of age and to evaluate the association with anthropometrics and sex. Material and methods 368 boys and 326 girls with a mean age of 6.7 ± 0.4 years participated. BMD was measured by DXA in the forearms and the os calcanei, with average values presented in this report. Measurements of weight, height, skinfolds, the width of distal radius and ulna, and the femur condyles were collected and body composition estimated from skinfolds measurements. Results There was no difference in calcaneus BMD when comparing boys and girls, whereas the boys had 4.5% (0.013 g/cm²) higher forearm BMD than the girls (P < 0.001). Calcaneal BMD (mean 0.318 g/cm²) was 11% higher than forearm BMD (mean 0.283 g/cm²). Linear relationship was found between calcaneus BMD and weight (partial r = 0.50), Fat free mass (FFM) (partial r = 0.50), Fat mass (FM) (partial r = 0.45), % body fat (partial r = 0.29) and knee width (partial r = 0.46), all P < 0.000 respectively. Adjusted for weight the relationship between calcaneus BMD and FFM, FM, %body fat and knee width disappeared. There were significant relationships between the forearm BMD and weight (partial r = 0.37), FFM (partial r = 0.39), FM (partial r = 0.28), %body fat (partial r = 0.14) and wrist width (partial r = 0.24), all P < 0.000 respectively. Adjusted for body weight, the relationship remained between forearm BMD and FFM (r = 0.10), FM (R = −0.10) and % body fat (r = −0.12), all P < 0.000 respectively. Children measured in the spring had 3.5% (P < 0.01) higher calcaneus BMD than children measured in the winter. Conclusion Seven year old boys have higher BMD in the forearm but not in the calcaneus in comparison with girls of a similar age. Body weight is the best predictor of calcaneus BMD, accounting for 25% of the variance whereas body weight and FFM are the best predictors of forearm BMD, each accounting for 17% of the variance, respectively.     

Lumbar spine bone density in argentine children

It has been demonstrated that bone mineral density (BMD) in children and adolescents is influenced by individual height. The aim of the present work was to introduce a formula to include height in the BMD analysis. Postero-anterior (PA) (L2–L4) and lateral (L2–L3) lumbar BMD was assessed by dual X-ray absorptiometry (DXA) in 433 and 393, respectively, healthy Caucasian females from 2 to 20 years of age. A complete medical examination including weight, height, and Tanner puberal stage was performed in all the subjects. Bone age was assessed by left wrist radiographs and analyzed by the TW2 method to insure that it was within 1 year of chronological age. Bone mineral density adjusted for height (BMD_corr=BMC/projected area × height), was calculated for each individual. As analyzed by Tanner stage, both PA and lateral BMD increased up to stage 3, and there were no significant differences among stages 3–5. Results of BMD_corr variations related to Tanner stage suggested that the increase in lateral BMD before puberty might be related to height. PA BMD_corr increased up to Tanner stage 3, and there were no differences among stages 3–5. The BMD_CORR approach can be used to get a more reliable analysis of BMD studies in children and adolescents. This study was presented in part at the 16th Annual Meeting of the American Society for Bone and Mineral Research, Kansas City, Missouri, September, 1994 This study has been supported by a grant from the Metabolic Research Foundation, Buenos Aires, Argentina     

乌鲁木齐地区2711例骨密度调查研究

目的了解新疆乌鲁木齐地区正常汉族人群骨密度(BMD)的变化规律和骨质疏松症(OP) 的患病率。方法应用法国DMS公司生产的CHALLENGER型双能X线骨密度仪对乌鲁木齐地区汉族人群共2711名20～80岁居民进行腰椎2～4及股骨近端的骨密度测定。结果乌鲁木齐地区汉族人群男性、女性的腰椎及股骨近端的BMD峰值均出现在20～29岁年龄组,峰值后随着年龄的增长,而骨密度BMD降低,女性在50～59岁明显加速下降,男性没有加速下降现象。乌鲁木齐地区40岁以后OP患病率男性28．3％,女性OP患病率45．2％。男女性50～59岁以上,组间患病率有显著差异(P<0．05)。结论通过对乌鲁木齐地区汉族人群的骨密度变化规律及患病率研究, 为乌鲁木齐地区汉族人群的骨质疏松症诊断及治疗提供客观有效的依据。     

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.     

The determination of bone fracture properties by dual-energy X-ray absorptiometry and single-photon absorptiometry: A comparative study

Summary Dual-energy X-ray absorptiometry (DEXA) and single-photon absorptiometry (SPA) were used to quantitate the structural strength and local material properties of healing tibial osteotomies in 32 dogs. Dogs were divided into four equal groups, euthanatized at either 2, 4, 8, or 12 weeks, and imaged with DEXA and SPA. Invasive techniques were used to determine (1) the torsional properties of the bone, (2) the local stiffness properties and calcium content within the bone, and (3) new bone formation and porosity by histology. There were no differences between SPA and DEXA in their associations with the torsional properties of bone. SPA and DEXA had strong correlations with the ultimate torque (R²=0.76, 0.51) and the torsional stiffness (R²=0.68, 0.53) of bone. SPA and DEXA of periosteal callus, endosteal callus, and cortical bone had similar associations with indentation stiffness, calcium content, new bone formation, and porosity. SPA of gap tissue had significantly stronger associations with these four parameters than DEXA (P<0.05). Correlation coefficients (R²) with these local material properties ranged as high as 0.82 for SPA with new bone formation in the gap tissue and 0.73 for DEXA with indentation stiffness of periosteal callus.