Axial and Total-Body Bone Densitometry Using a Narrow-Angle Fan-Beam

We assessed a new dual-energy bone densitometer, the PRODIGY, that uses a narrow-angle fan-beam (4.5°) oriented parallel to the longitudinal axis of the body (i.e., perpendicular to the usual orientation). High-resolution scans across the body can be stepped at 17 mm intervals. The energy-sensitive array detector uses cadmium zinc telluride, which allowed rapid photon counting. Spine and femur scans required 30 s, and total-body scans required 4–5 min; the dose was only 3.7 mrem and 0.04 mrem respectively, or about 5 to 10 times lower than conventional fan-beam densitometry. We found only a small influence of soft-tissue thickness on bone mineral density (BMD) results. There was also a small ( ± 1%) influence of height above the tabletop on BMD results. A software correction for object height allowed a first-order correction for the large magnification effects of position on bone mineral content (BMC) and area. Consequently, the results for BMC and area, as well as BMD, with PRODIGY corresponded closely to those obtained using the predecessor DPX densitometer, both in vitro and in vivo; there was a generally high correlation (r= 0.98–0.99) for BMD values. Spine and femur values for BMC, area and BMD averaged within 0.5% in vivo (n= 122), as did total-body BMC and BMD (n= 46). PRODIGY values for total-body lean tissue and fat also corresponded within 1% to DPX values. Regional and total-body BMD were measured with 0.5% precision in vitro and 1% precision in vivo. The new PRODIGY densitometer appears to combine the low dose and high accuracy of pencil-beam densitometry with the speed of fan-beam densitometers. Received: 2 April 1999 / Accepted: 27 July 1999     

The Effect of Weight Change on DXA Scans in a 2-Year Trial of Etidronate Therapy

Variation in soft tissue composition is a potential cause of error in dual X-ray absorptiometry (DXA) measurements of bone mineral density (BMD). We investigated the effect of patients' change of weight on DXA scans in 152 women enrolled in a 2-year trial of cyclical etidronate therapy. Scans of the spine, hip, and total body were performed at baseline, 1 and 2 years on a Hologic QDR-2000. The study was completed by 135 subjects (64 on etidronate, 71 on placebo). Results were expressed as the percentage change in BMD (spine, femoral neck, total body) or bone mineral content (BMC) (total body only) at 2 years. Total body scans were analyzed using the manufacturer's `standard' and `enhanced' algorithms. Analysis was performed using multivariate regression with percentage change in BMD or BMC as the dependent variable, and treatment group and percentage change in weight as the independent variables. Weight change varied between −14.4% and +16.7%. All DXA variables showed a statistically significant treatment effect. Standard total body BMD and BMC and enhanced total body BMC all showed a significant dependence on weight change (P < 0.01, P < 0.001 and P < 0.01, respectively). No effect of weight change was seen on spine, femoral neck, or enhanced total body BMD. In order to investigate the effects of weight on long-term precision, patients were allocated to two groups according to baseline body mass index (BMI <25 and >25 kg/m², respectively). For femoral neck BMD the root mean square (RMS) residual percentage change was statistically significantly larger in the high BMI group (P < 0.05) but all other bone density variables showed no significant difference. With patients allocated to two groups according to their absolute percentage change in weight (<5% and >5%, respectively) the RMS residual percentage changes in the bone density variables were statistically significantly larger in the large weight change group for femoral neck BMD (P < 0.05) and for standard and enhanced total body BMC (P < 0.01 and P < 0.05, respectively). With the exception of the standard total body algorithm, weight change in a longitudinal study of postmenopausal women was not found to cause systematic errors in the results of DXA studies but may adversely affect precision. Received: 22 November 1996 / Accepted: 30 April 1997     

Dual Energy X-Ray Absorptiometry in Small Rats with Low Bone Mineral Density

The feasibility of dual energy X-ray absorptiometry (DXA) using the Norland XR-26 Mark II bone densitometer for measurements of bone mineral content (BMC) and bone mineral density (BMD) in small rats was evaluated. Thirty-two young, isogenic, Lewis rats (weights from 119 g to 227 g) were used; normal rats (n = 7) and rats with low BMD obtained from three different vitamin D-depleted models (n = 25). DXA measurements were performed using the special software for small animals. Duplicate scans of excised femurs performed at 2 mm/second (pixel size of 0.5 mm × 0.5 mm) were very precise measurements with a coefficient of variation (CV) below 1.6% in animals with normal BMD; in rats with low BMD, the CV was significantly higher (P= 0.02–0.04), 7.8% and 4.4% for BMC and BMD, respectively. Regression analysis demonstrated that these measurements were related to the ash weight (R² > 98.6%). The CV for measurements of the lumbar spine at 10 mm/second (pixel size 0.5 mm × 0.5 mm) was 2.6% and 2.2% for BMC and BMD, respectively in rats with normal BMD, and again higher (P= 0.03–0.14) in rats with low BMD, 7.3% and 4.7%, respectively, for BMC and BMD. Even though low CVs were obtained for total body duplicate scans (scan speed of 20 mm/second and a pixel size of 1.5 mm × 1.5 mm), the measurements were problematic for accuracy because of an overestimation of both BMC and the area of bone. Using these scan parameters the measurements of total body bone mineral could not be recommended in small rats with low BMD. Received: 21 May 1999 / Accepted: 3 August 2000 / Online publication: 22 December 2000     

Effect of High Impact Activity on Bone Mass and Size in Adolescent Females: A Comparative Study Between Two Different Types of Sports

The purpose of this cross-sectional study was to investigate the influence of two different types of weight-bearing activity, muscle strength, and body composition on bone mineral density (BMD), bone mineral content (BMC), and bone area in three different groups of late adolescent girls. The first group consisted of 10 females participating in competitive rope-skipping (age 17.8 ± 0.8 years) training for 6.7 ± 3.1 hours/week; the second group consisted of 15 soccer players (age 17.4 ± 0.8 years) training for 6.1 ± 2.0 hours/week; and the third group consisted of 25 controls (age 17.6 ± 0.8 years) with physical activity of 0.9 ± 1.1 hours/week. The groups were matched for age, height, and weight. BMD (g/cm²), BMC (g), and bone area (cm²) of the total body, lumbar spine, hip, total femur, distal femur, diaphyses of femur and tibia, proximal tibia, and humerus were measured using dual-energy X-ray absorptiometry (DXA). Bone density was also assessed in the radial forearm site of the dominant limb in the rope skippers and in 10 matched controls. The rope skippers had 22% higher BMD at the ultradistal site (P < 0.01). Both high-activity groups had significantly higher BMD (P < 0.05) at most loaded sites compared with the control group. When adjusting for differences in lean mass and starting age of sport-specific training between the activity groups, the rope-skipping group had a higher BMD of the total body, lumbar spine, and right humerus compared with the soccer group. They also had a significantly higher bone area of the total body, total femur, and the proximal femur than both other groups, and a significantly higher bone area of the tibia diaphysis, compared with the soccer group. In a multivariate analysis among all subjects (n = 50), all BMD sites, except the femur diaphysis, distal femur, and proximal tibia, were significantly related to type of physical activity (β= 0.25–0.43, P < 0.05). The bone area values at different sites were strongly related to muscle strength and parameters related to body size [height, weight, lean mass, fat mass, and body mass index (BMI)]. In conclusion, it appears that in late adolescent women, weight-bearing activities are an important determinant for bone density, and high impact activities such as jumping also seem to be associated with a modification of the bone geometry (hence, the bone width) at the loaded sites. Received: 28 June 1999 / Accepted: 22 March 2000     

Anomalies in the Measurement of Changes in Bone Mineral Density of the Spine by Dual-Energy X-ray Absorptiometry

Dual-energy X-ray absorptiometry (DXA) is frequently used for longitudinal studies of bone mineral status because of the high precision obtained, but evidence is emerging that the accuracy of measurements of changes may be a limitation because of artefacts of the analysis procedure, in particular, a dependence of the measured bone area (BA) on the bone mineral content (BMC). Results of spine bone mineral measurements taken at intervals with two DXA scanners, a Hologic QDR 1000W, and a Norland XR 26 HS, were examined. There was a consistent correlation between changes in BA and in BMC, with a slope of approximately 0.25 when expressed as percentages. A real change of BA of the magnitude observed is not feasible. There were no differences among the correlations for different instruments, genders, ages, or weight changes. There would appear to be an underestimation of changes in bone mineral density (BMD), but there is a possibility that some of the anomaly is manifested as an overestimation of a change in BMC. Phantom measurements were undertaken with the DXA scanners mentioned above and with a Lunar DPX. The phantoms consisted of simulations of the spine cut from aluminium sheet, so that the effective BMD could be varied. The dependence of the measured BA on BMC varied with the phantom outline, particularly the thickness of the transverse processes. Evidence was obtained of both an underestimate of BMD changes and an overestimate of BMC changes. There are errors in measuring spine changes, but these do not seem to be as serious as a previous report suggests for the Hologic scanner and are not likely to lead to misinterpretation of results. Received: 17 June 1997 / Accepted: 23 January 1998     

Bone Mineral Content and Density in Professional Tennis Players

Total and regional bone mineral content (BMC) as well as lean and fat mass were measured in nine male professional tennis players (TPs) and 17 nonactive subjects; dual-energy X-ray absorptiometry (DXA) was used for measuring. The mean (±SD) age, body mass, and height were 26 ± 6 and 24 ± 3 years, 77 ± 10 and 74 ± 9 kg, and 180 ± 6 and 178 ± 6 cm for the TP and the control group (CG), respectively. The whole body composition for BMC, lean mass, and fat of the TP was similar to that observed in the CG. The tissue composition of the arms and legs was determined from the regional analysis of the whole-body DXA scan. The arm region included the hand, forearm, and arm, and was separated from the trunk by an inclined line crossing the scapulo-humeral joint. In the TP, the arm tissue mass (BMC + fat + lean mass) was about 20% greater in the dominant compared with the contralateral arm because of a greater lean (3772 ± 500 versus 3148 ± 380 g, P < 0.001) and BMC (229.0 ± 43.5 versus 188.2 ± 31.9 g, P < 0.001). In contrast, no significant differences were observed either in BMC or BMD between arms in the CG. Total mass, lean mass, and BMC were greater in the dominant arm of the TP than in the CG (all P < 0.05). In the TP, BMD was similar in both legs whereas in the CG, BMD was greater in the right leg. Lumbar spine (L2–L4) BMD, adjusted for body mass and height, was 15% greater in the TP than in the CG (P < 0.05). Femoral neck BMDs (femoral neck, Ward's triangle, greater trochanter, and intertrochanteric regions) adjusted for body mass and height were 10–15% greater in the TP (all P < 0.05). Ward's triangle BMD was correlated with the maximal leg extension isometric strength (r = 0.77, P < 0.05) even when adjusted for body mass (r = 0.76, P < 0.05) and height (r = 0.77, P < 0.05). In summary, the participation in tennis is associated with increased BMD in the lumbar spine and femoral neck. These results may have implications for devising exercise strategies in young and middle-aged persons to prevent involutional osteoporosis later in life. Received: 29 April 1997 / Accepted: 14 November 1997     

Professional Football (Soccer) Players Have a Markedly Greater Skeletal Mineral Content, Density and Size Than Age- and BMI-Matched Controls

The total skeletal bone mineral content (BMC), bone mineral density (BMD), bone size, and body composition were measured by dual-energy x-ray absorptiometry (DXA) in all professional male football players of a 1st division team (n = 24) and age- and BMI-matched (n = 22) controls (less than 3 hours of recreational sport activities per week). Average (±1 SD) age of the athletes was 22.6 ± 2.5 years. Intensive training is conducted during 48 weeks a year for 20–22 hours/week. The length of the registered playing career before the study was 8.2 ± 2.7 years. Total skeleton BMC was 18.0% (P < 0.001) greater in the football players. The difference resulted from the sum of 5.2% (P < 0.02) increment of bone size and 12.3% (P < 0.001) increment of BMD. The analysis of skeletal subareas revealed that the difference of the BMC and BMD was greater at the level of the pelvis and legs compared with the arms or trunk. The BMC and BMD of the head was equal for both groups. Also, the bone size of the legs and pelvis was significantly greater for the players compared with controls; there was no difference at the level of the arms or head. Within the group of football players the increment of total skeleton BMD was similar in the young players, with less than 7 years of practice (age 20.6 ± 0.9 years) compared with relative older players (age 24.6 ± 1.9) with more than 7 years of practice. Lean body mass was significantly greater in the players (63.3 ± 4.0 kg) compared with the controls (56.7 ± 3.6, P < 0.001) whereas fat mass was markedly lower (9.4 ± 2.9 kg versus 14.9 ± 6.3 kg), P < 0.002). The BMD of the controls was significantly correlated to total weight, height, and lean mass whereas the BMD of the players was only correlated to muscle mass. The calcium intake from dairy products was similar in both groups. The range of calcium intake was wide among the players (184–2519 mg/day) but it was not significantly correlated to BMD (r = 0.03). In conclusion, male professional football players develop a significant increment of BMC as a result of increased bone size and density. This is already present at the end of the second decade and maintained at least to the end of the third decade in active players. As in other high impact loading sports, the effect on area is specific involving mainly the pelvis and legs. The increment was totally unrelated to the calcium intake from dairy products. The fate of the increased BMC after intensive training is discontinued should be assessed. However, if the findings of the present cross-sectional study are supported by detailed longitudinal investigations, the presently reported observations might be important for the prevention of future osteoporotic fractures. Received: 8 August 1997 / Accepted: 26 January 1998     

Differential Effects of Bone Mineral Content and Bone Area on Vertebral Strength in a Swine Model

Since the biomechanical competence of a vertebral body may be closely related to the content and distribution of the bone mineral, we have evaluated the effects of projected vertebral bone area (BA) and bone mineral parameters [bone mineral content (BMC) or bone mineral density (BMD)] on their biomechanical competence. We used dual-energy X-ray absorptiometry (DXA) to assess the bone mineral parameters of 36 swine thoracic vertebrae (T1–T12) and 15 lumbar vertebrae (L1–L5) after removal of the posterior elements. The failure load, compressive stress, and the stored strain energy of these vertebral bodies were assessed by a uniaxial compressive test using an MTS 810 testing system. Multiple regression analysis showed a significantly negative effect of BA and significantly positive effect of BMC on the biomechanical competence (compressive stress, r²= 0.67, P < 0.0001; failure load, r²= 0.75, P < 0.0001). However, the stored strain energy was only related to the BMC (r²= 0.35, P < 0.0001). The contributory effects of BMC and BA on the biomechanical competence were not equal. The effects of BMC was larger than BA in determining the failure load and stored strain energy, whereas the reverse was found for the compressive stress. Using the log-transformed parameters as the regressors resulted in similar results. These results suggested the differential effects of BA and BMC in determining the biomechanical competence of vertebral bodies. We recommend the use of both parameters instead of BMD alone for evaluation of the vertebral biomechanical competence. Received: 26 June 1997 / Accepted: 8 January 1998     

Bone Mineral Density During Reduction, Maintenance and Regain of Body Weight in Premenopausal, Obese Women

Weight loss may lead to bone loss but little is known about changes in bone mass during regain of reduced weight. We studied changes in bone mineral density (BMD) and bone mineral content (BMC) during voluntary weight reduction and partial regain. The study consisted of three phases: a 3 month weight reduction with very-low-energy diet (VLED), a 9 month randomized, controlled walking intervention period with two training groups (target energy expenditure 4.2 or 8.4 MJ/week) and a 24-month follow-up. The participants were premenopausal women with a mean body mass index of 34.0 (SD 3.6) kg/m². Seventy-four of 85 subjects completed the whole study. Total body, lumbar spine, proximal femur and dominant radius BMD and BMC were measured with dual-energy X-ray absorptiometry (DXA). The mean weight loss during VLED was 13.2 (3.4) kg, accompanied by unchanged total body BMC and decreased lumbar, trochanteric and radial BMD (p<0.05). During months 3–36, an average of 62% of the weight loss was regained, total body BMC decreased and trochanteric BMD increased (p<0.05). At the end of the study, total body BMC and lumbar and femoral neck BMD were lower than initially (p<0.05). Weight change throughout the study correlated significantly with the change in radial (r= 0.54), total body (r= 0.39) and trochanteric (r= 0.37) BMD. Exercise-group assignment had no effect on BMD at weight-bearing sites. In conclusion, the observed changes in BMD and BMC during weight reduction and its partial regain were clinically small and partly reversible. More studies are needed to clarify whether the observed weight changes in BMD and BMC are real or are artifacts arising from assumptions, inaccuracies and technical limitations of DXA. Received: 20 April 2000 / Accepted: 20 September 2000     

Low Bone Density with Normal Bone Turnover in Ovariectomized and Streptozotocin-Induced Diabetic Rats

Diabetes and estrogen deficit are known causes of osteopenia, diabetes being associated with a low bone turnover and estrogen deficit with a high bone turnover. In the present work, we studied the effect of combined ovariectomy and diabetes on bone mineral content (BMC) and bone mineral density (BMD) and several bone markers in the rat. Four groups of rats were studied: control (C), ovariectomized (O), diabetic (D), and ovariectomized and diabetic (DO). Twelve weeks after starting the experiments, BMC and BMD of the first six lumbar vertebrae were measured; a bone formation marker (BGP) and a bone resorption marker (free collagen cross-links, PYD) were also analyzed. Diabetic rats showed diminished gain in bone mass, BMC (D: 0.417 ± 0.028 g, DO: 0.422 ± 0.020 g) and BMDs (D: 0.171 ± 0.006 g/cm², DO: 0.174 ± 0.006 g/cm²) both being significantly (P < 0.001) lower than those of control (C: BMC 0.727 ± 0.024 g and BMD 0.258 ± 0.004 g/cm²) and ovariectomized (O: BMC 0.640 ± 0.044 g and BMD 0.240 ± 0.009 g/cm²) groups. Moreover, the BMC and BMD of the C group were significantly (P < 0.05) higher than that of the O group. BGP and PYD levels were significantly (P < 0.01) higher in the O group (BGP: 138.2 ± 16.8 ng/ml, PYD: 270.2 ± 17.8 nM/mM) than those found in the control rats (BGP: 44.7 ± 4.8 ng/ml, PYD: 165.6 ± 12.5 nM/mM); the D group showed significantly (P < 0.01) lower values (BGP: 27.4 ± 14.6 ng/ml, PYD: 55.0 ± 7.4 nM/mM) than those of the control group. The DO group showed similar levels (BGP: 43.4 ± 5.1 ng/ml, PYD: 146.7 ± 14.6 nM/mM) to those found in the C group. Although bone marker levels in the O and D groups were in accordance with those expected in these situations, in the DO group the corresponding levels are apparently ``normal.' Also, the decrease of gain in bone mass observed after combining estrogen deficit and diabetes (DO group) did not seem to be more marked than that caused by diabetes alone. Received: 7 January 1997 / Accepted: 7 August 1997     

Accuracy and precision of in vivo bone mineral measurements in sheep using dual-energy X-ray absorptiometry

We evaluated the precision and accuracy of in vivo measurements of spine bone mineral density (BMD) and bone mineral content (BMC) in five ewes using dual-energy X-ray absorptiometry (DXA, Lunar DPX-L). The short-term in vivo reproducibility expressed as the coefficient of variation (CV) varied from 0.9 to 1.6% for spine BMD and from 1 to 3.1% for spine BMC. The ex vivo measurements, performed in 20 cm of water to simulate soft tissue thickness, correlated closely with the in vivo measurements, yielding an r value of 0.98 and 0.97 for spine BMD and BMC, respectively. The accuracy was determined by comparing the total BMC of each vertebra measured in vivo with the corresponding ash weight. The correlation coefficient between the two measurements was r = 0.98, with an accuracy error of 5.6%. We concluded that the DXA allows a precise and accurate measurement of spine bone mineral in live ewes using the methodology designed for humans. Received: 19 March 1999 / Accepted: 26 July 1999     

Determinants of Bone Mass and Bone Geometry in Adolescent and Young Adult Women

Bone mass and bone geometry are considered to have independent effects on bone strength. The purpose of this study was to obtain data on bone mass and geometry in young female populations and how they are influenced by body size and lifestyle factors. In a cross-sectional, observational study in six European countries, 1116 healthy Caucasian girls aged 11–15 and 526 women aged 20–23 participated. Their radius was scanned at the ultradistal site and at a site approximately 30% of the radius length from the distal end with dual energy X-ray absorptiometry (DXA). The following parameters were assessed from the scans: bone mineral content (BMC), bone mineral density (BMD), cortical wall thickness (CWT), middistal diameter (D), cortical index (CI = 2CWT/D), and the Breaking Bending Resistance Index (BBRI = (D⁴− [D-CWT]⁴)/D). Calcium intake was assessed by 3-day food records and physical activity by questionnaire. Body size parameters were measured by anthropometry. All parameters showed an increasing trend with pubertal stage and age, except for physical activity and calcium intake. BMC and BMD were relatively more dependent on body weight and age at menarche, whereas variation in D and the mechanical index BBRI was better explained by differences in height and grip strength. CI and CWT were relatively independent of variation in body size, whereas BMC and BBRI especially were explained for a substantial proportion (25–33% in the young adults) by body size parameters. Dietary intake of calcium and level of physical activity seem to contribute little to variation in bone parameters. Received: 1 October 1998 / Accepted: 26 July 1999     

Lifestyle Determinants of Bone Mineral: A Comparison Between Prepubertal Asian- and Caucasian-Canadian Boys and Girls

The purpose of this study was to examine the difference in lifestyle and morphometric factors that affect bone mineral and the attainment of peak bone mass in 168 healthy Asian (n = 58) and Caucasian (n = 110) Canadian, prepubertal girls and boys (mean age 8.9 ± 0.7) living in close geographical proximity. DXA (Hologic 4500) scans of the proximal femur (with regions), lumbar spine, and total body (TB) were acquired. We report areal bone mineral densities (aBMD g/cm²) at all sites and estimated volumetric density (νBMD, g/cm³) at the femoral neck. Dietary calcium, physical activity, and maturity were estimated by questionnaire. Of these prepubertal children, all of the boys and 89% of the girls were Tanner stage 1. A 2 × 2 ANOVA demonstrated no difference between ethnicities for height, weight, body fat, or bone mineral free lean mass. Asian children consumed significantly less dietary calcium (35%) on average and were significantly less active (15%) than their Caucasian counterparts (P < 0.001). There were significant ethnicity main effects for femoral neck bone mineral content (BMC) and αBMD (both P < 0.001) and significant sex by ethnicity interactions (P < 0.01). The Asian boys had significantly lower femoral neck BMC (11%), aBMD (8%), and νBMD (4.4%). At the femoral neck, BMFL mass, sex, and physical activity explained 37% of the total variance in aBMD (P < 0.05). In summary, this study demonstrated differences in modifiable lifestyle factors and femoral neck bone mineral between Asian and Caucasian boys. Received: 21 July 1998 / Accepted: 30 September 1999     

Plasma Leptin Values in Relation to Bone Mass and Density and to Dynamic Biochemical Markers of Bone Resorption and Formation in Postmenopausal Women

After the menopause it has been noted that heavier women conserve bone better than those with lower body weight. The protective effect of obesity on bone mass has been ascribed to a high body fat content. The present study of 54 postmenopausal women was undertaken to determine whether circulating plasma levels of leptin, the newly described hormone produced in adipocytes, were correlated with age-adjusted total body bone mineral content (BMC) or bone mineral density (BMD), or with dynamic biochemical markers of bone resorption or of bone formation. Leptin values were strongly correlated with all measures of adiposity (P < 0.001). Age-adjusted values for BMC and BMD, respectively, were also positively correlated (P < 0.001) with body weight (r = 0.643, r = 0.502), total fat mass (r = 0.557, r = 0.510) and with plasma leptin concentrations (r = 0.480, r = 0.551), confirming a positive relationship between fat mass and bone mass. By contrast, no significant correlations were observed between plasma leptin and dynamic markers of bone resorption (urinary deoxypyridinoline/creatinine r =−0.105, hydroxyproline/creatinine r =−0.193) or formation (plasma osteocalcin r = 0.103). Because there was no evidence for an association between ciculating plasma levels of leptin and biochemical markers of either osteoclastic or osteoblastic activity we conclude it is unlikely that circulating leptin plays any significant direct role in controlling bone cell activity. Our results do not support the hypothesis that leptin mediates the bone-sparing effects of obesity. Received: 23 September 1997 / Accepted: 11 May 1998     

Peripheral Bone Mass is Not Affected by Winter Vitamin D Deficiency in Children and Young Adults from Ushuaia

Low vitamin D levels in elderly people are associated with reduced bone mass, secondary hyperparathyroidism, and increased fracture risk. Its effect on the growing skeleton is not well known. The aim of this study was to evaluate the possible influence of chronic winter vitamin D deficiency and higher winter parathyroid hormone (PTH) levels on bone mass in prepubertal children and young adults. The study was carried out in male and female Caucasian subjects. A total of 163 prepubertal children (X age ± 1 SD: 8.9 ± 0.7 years) and 234 young adults (22.9 ± 3.6 years) who had never received vitamin D supplementation were recruited from two areas in Argentina: (1)Ushuaia (55° South latitude), where the population is known to have low winter 25OHD levels and higher levels of PTH in winter than in summer, and (2)Buenos Aires (34°S), where ultraviolet (UV) radiation and vitamin D nutritional status in the population are adequate all year round. Bone mineral content (BMC) and bone mineral density (BMD) of the ultradistal and distal radius were measured in the young adults. Only distal radius measurements were taken in the children. Similar results were obtained in age-sex matched groups from both areas. The only results showing significant difference corresponded to comparison among the Ushuaian women: those whose calcium (Ca) intake was below 800 mg/day presented lower BMD and BMC values than those whose Ca intake was above that level (0.469 ± 0.046 versus 0.498 ± 0.041 g/cm², P < 0.02; 3.131 ± 0.367 versus 3.339 ± 0.386 g, P < 0.05, respectively). In conclusion, peripheral BMD and BMC were similar in children and young adults from Ushuaia and Buenos Aires in spite of the previously documented difference between both areas regarding UV radiation and winter vitamin D status. BMD of axial skeletal areas as well the concomitant effect of a low Ca diet and vitamin D deficiency on the growing skeleton should be studied further. Received: 7 June 1999 / Accepted: 22 March 2000     

Long-term Loading and Regional Bone Mass of the Arm in Female Volleyball Players

In the present study, we compared the bone mineral content (BMC) and bone mineral density (BMD) in the arms of 11 female volleyball players (mean age 22.0 ± 2.6 years) training for about 8 hours/week, and 11 nonactive females aged 24.6 ± 3.1 years (mean ± SD) not participating in regular or organized sport activity. Using dual X-ray absorptiometry (DXA), BMC was measured in the proximal and distal humerus, and BMD in the distal radius. Isokinetic concentric peak torque (highest value attained during 5 or 10 repetitions) of the rotator muscles of the shoulder and flexor and extensor muscles of the elbow were measured using an isokinetic dynamometer. The volleyball players had significantly higher BMC (P < 0.05) at the proximal humerus of the dominant arm compared with the nonactive group, but there were no differences between the groups in BMC of the distal humerus and BMD of the distal radius. In the volleyball players, BMC was significantly higher at the proximal humerus, at the distal humerus, and at the distal radius in the dominant compared with the nondominant arm. In the nonactive group, there were no significant differences in BMC and BMD between the dominant and nondominant arm at any site measured. Except for shoulder internal rotation strength and elbow flexion strength at 90°/second that was higher in the dominant arm in the volleyball players, there were no significant differences in muscle strength of the rotator muscles of the shoulder and flexor and extensor muscles of the elbow between the dominant and nondominant arm in the volleyball players and nonactive controls. In the volleyball players, but not in the nonactive controls, there were several significant relationships between shoulder and elbow strength and BMC at the distal humerus of the dominant and especially the nondominant arm. These results show that young female volleyball players have a higher bone mass in the proximal humerus, distal humerus, and distal radius in the dominant compared with the nondominant arm, and a higher bone mass in the proximal humerus compared with nonactive controls. Muscle strength of the rotator muscles of the shoulder is not related to the higher bone mass in the proximal humerus of the dominant arm. Theoretically, the observed differences in bone mass can be related to the type of loading the skeleton undergoes when playing volleyball. Received: 21 June 1996 / Accepted: 3 September 1997     

Bone Density of the Spine and Femur in Adult White Females

We measured bone mineral density (BMD in g/cm²) of the spine (L2-L4) and femur (four regions) in 1472 and 1487 cases, respectively, of ambulatory white women ages 20–79 years in the USA. A DPX densitometer was used in a mobile setting. The BMD values for women up to 69 years corresponded closely with published values for the USA, the UK, and northern Europe; our values were somewhat lower than those from other studies only in women over 70 years. The USA data were combined with data from Europe to give reference curves on about 12,000 subjects. Decreases of BMD with age in women below 50 years were much smaller than in older women (0.2% versus 0.6–1.0% per year). Femoral bone decreased from the neck region, but not the trochanter with age; the decrease of total femur BMD with age was due to loss from the former region. Loss of bone mineral content (BMC in g) from the femur neck and total femur region did not accelerate until after age 50 years, much like the spine. The apparent decrease of BMD in these regions that begins about age 40 actually is due to an increase of bone area. About 20% of USA women aged 50–79 years had BMD levels for the lumbar spine, or for the femur neck, more than −2.5 SD below the average values in young adult women 20–39 years old. Body weight had several times more impact on BMD than height, and in fact, a change of 1 kg in postmenopausal women was commensurate with the effect of a 1-year change in age. Subjects in the lowest quartile of body weight had T-scores that were 1 SD below those in the highest quartile. Received: 10 September 1998 / Accepted: 15 December 1998     

Influence of Electromagnetic Fields on Bone Mass and Growth in Developing Rats: A Morphometric,Densitometric, and Histomorphometric Study

The effect of electromagnetic fields on bone is debated. In an experimental study of this effect, we compared two lots of growing female rates (both lots n = 15, age 3 weeks, average weight 23.2 ± 3.3 g), one of which was exposed to a 3-mT, 100-Hz, Helmholtz-type electromagnetic field for 24 hours a day for 30 days, and the other of which served as the control. Bone development and bone mass were evaluated by morphometry, densitometry, and histomorphometry. The rats were killed at 30 days and weighed. The right femurs were dissected, measured, and weighed; bone densitometry was used to determine femoral bone mineral content (BMC) and density (BMD), and histomorphometry of the nondecalcified bone was used to determine trabecular bone volume (Cn-BV-TV%), number (Tb-N mm) and thickness (Tb-Th μm), intertrabecular space (Tb-Sp μm) and growth cartilage thickness (Gc-Th μm). In the rats exposed to the electromagnetic field, BMC and BMD (P= 0.019 and P= 0.002, respectively) and Cn-BV-TV, Tb-N, Tb-Th (P= 0.005, P= 0.036, and P= 0.027, respectively) all were decreased, whereas Tb-Sp was increased (P= 0.002). There were no significant differences in initial and final body weight, or in final femur weight, femur length, and GC-Th. These findings indicate that electromagnetic fields of the type used here reduced bone formation and increased bone resorption without affecting bone development in rats. Received: 12 February 1996 / Accepted: 2 December 1996     

Switching from DXA pencil-beam to fan-beam. I: Studies in vitro at four centers

The performance of the Hologic QDR-2000 DXA osteodensitometer was critically evaluated at four centers, using at all four centers one bone equivalent humanoid spine phantom supplied by the manufacturer. Results were compared with results from Hologic QDR-1000/W using that phantom tested at the same centers.

It appears that the concept of fan-beam scanning—as used in the QDR-2000: a fan-beam, a linear array detector above the phantom, and an x-ray tube located rather close to the spine below the phantom—creates problems due to the magnification effect of the fan beam. The effect of decreasing the distance between the “vertebrae” of the phantom and the couch are: bone mineral content (BMC) increases by 2.8% per cm, projected area (Area) by 2.8% per cm, and bone mineral density (BMD) is unchanged.

When QDR-1000/W is upgraded to QDR-2000, BMD is relatively constant, but there are shifts of BMC and Area which are partly due to the magnification effect of the fanbeam. Replacement of a QDR-1000/W with a QDR-2000 can invalidate longitudinal measurements, even for BMD, unless the proportionality factors of the QDR-2000 are checked and, if necessary, changed. This is true for switching from QDR-1000/W to pencil-beam mode of QDR-2000 or to fanbeam mode of QDR-2000.

Even with pencil-beam mode, the long-term precision error with phantoms is higher for QDR-2000 than for QDR-1000/W (for BMD, 0.47% versus 0.35%).     

Bone Mineral Density of Opposing Hips Using Dual Energy X-Ray Absorptiometry in Single-Beam and Fan-Beam Design

Bone densitometry focuses on bone mineral area density (BMD in g/cm²) of the proximal femur and spine in anterior-posterior (AP) projections. Artifacts, such as osteoarthritis and osteophytic calcifications (OC) influence spine BMD, especially in AP scans. If only two sites are measured, as is usual in clinical practice, there may be advantages to measuring both femora rather than one femur and the spine. This would not be useful, however, if there was strong symmetry between the two sides. Furthermore, fan beam (FB) techniques have become available for measuring BMD with less data acquisition time. We compared densitometry of opposing femora in 421 patients (369 women, mean age 59.0 ± 4.8; 52 men, mean age 56.9 ± 7.4) using dual-energy X-ray absorptiometry (DXA): both single-beam (SB) and FB modes were evaluated. The precision errors in vivo (short- and midterm) of total BMD were 0.7% for both SB and FB. The total BMD and BMC of the left hip (0.817 ± 0.124 g/cm², 31.3 ± 6.4 g) were significantly (P < 0.001) higher (2–3%) than the corresponding values of the right hip (0.801 ± 0.125 g/cm², 30.3 ± 6.3 g) in both SB and FB (left BMD 0.802 ± 0.117 g/cm², BMC 30.0 ± 6.2 g versus right BMD 0.795 ± 0.117 g/cm², BMC 29.3 ± 6.3 g) modes. However, BMD of the femoral neck and Ward's triangle were not significantly (P > 0.05) different between the two sides. The FB results were generally 2% lower than SB results. There were highly significant (P < 0.001) correlations (r > 0.9) between both hips using both SB and FB. For diagnostic procedures and longitudinal studies, one should consider that there are bilateral differences of femur BMD, as well as differences between FB and SB scan modes.