Differences In Bone Size Research Articles

The amount of periosteal apposition required to maintain bone strength during aging depends on adult bone morphology and tissue-modulus degradation rate.

Although the continued periosteal apposition that accompanies age-related bone loss is a biomechanically critical target for prophylactic treatment of bone fragility, the magnitude of periosteal expansion required to maintain strength during aging has not been established. A new model for predicting periosteal apposition rate for men and women was developed to better understand the complex, nonlinear interactions that exist among bone morphology, tissue-modulus, and aging. Periosteal apposition rate varied up to eightfold across bone sizes, and this depended on the relationship between cortical area and total area, which varies with external size and among anatomical sites. Increasing tissue-modulus degradation rate from 0% to -4%/decade resulted in 65% to 145% increases in periosteal apposition rate beyond that expected for bone loss alone. Periosteal apposition rate had to increase as much as 350% over time to maintain stiffness for slender diaphyses, whereas robust bones required less than a 32% increase over time. Small changes in the amount of bone accrued during growth (ie, adult cortical area) affected periosteal apposition rate of slender bones to a much greater extent compared to robust bones. This outcome suggested that impaired bone growth places a heavy burden on the biological activity required to maintain stiffness with aging. Finally, sex-specific differences in periosteal apposition were attributable in part to differences in bone size between the two populations. The results indicated that a substantial proportion of the variation in periosteal expansion required to maintain bone strength during aging can be attributed to the natural variation in adult bone width. Efforts to identify factors contributing to variation in periosteal expansion will benefit from developing a better understanding of how to adjust clinical data to differentiate the biological responses attributable to size-effects from other genetic and environmental factors.

Quantitative Computerized Tomography (QCT) versus Dual X-Ray Absorptiometry (DXA) in the Assessment of Bone Mineral Density of HIV-1 Infected Children

Bone studies of HIV-infected children using dual X-ray absorptiometry (DXA) suggest bone mineral density (BMD) abnormalities. Pediatric studies are often performed using DXA instead of computed tomography (CT), which accounts for 3-dimensional differences in bone size of growing children. We evaluated whether CT would match DXA measurements in this population. For this purpose, the BMD of 16 perinatally HIV-infected patients, ages 6 to 22 was assessed. Subjects were matched by age, gender, and race to controls. BMD was assessed via DXA and QCT. Clinical anthropometric data, body mass index, immunologic and virologic parameters and laboratory markers for osteoblastic and osteoclastic activity were performed. No statistically significant differences in age and anthropometric parameters between subjects and controls were found. Individual CT and DXA z-scores were significantly different when subjects were evaluated as a group (p = 0.0002) or when males and females were analyzed independently (p = 0.001 and 0.03). DXA z-scores were below 1 SD, while CT z-scores were above the mean. 31% of subjects were identified as having poor bone mineralization by DXA while none had osteopenia/osteoporosis by CT. There was no correlation between immunologic/virologic parameters and BMD by either method. Increased osteoclastic activity was noted in 10 patients receiving tenofovir. In summary, decreased BMD diagnosed by DXA in pediatric HIV-infected subjects was not confirmed by CT. Increased bone turnover in patients on tenofovir was suggested by laboratory markers. Prospective studies using CT as the imaging standard are needed for evaluation of bone mineral changes in HIV-infected children.

Volumetric bone mineral density at the spine and hip in Chinese American and White women

This study evaluated racial differences in bone size and volumetric density at the spine and hip in pre- and postmenopausal Chinese American and White women. Compared with White women, Chinese American women have greater cortical volumetric bone density (vBMD) at the hip, congruent with the results at the peripheral skeleton. Chinese American women have lower rates of fracture than White women despite lower areal bone density. At the forearm and tibia, however, Chinese American women have higher cortical vBMD as well as greater trabecular and cortical thickness, but smaller bone area as measured by high-resolution peripheral quantitative computed tomography (HR-pQCT) compared with White women. Since HR-pQCT data are obtained at peripheral sites, it is unclear whether these differences are relevant to the clinically important lumbar spine and hip. This study assesses racial differences in bone size and vBMD at the spine and hip in Chinese American and White women. QCT of the spine and hip was measured to assess racial differences in bone size, structure, and vBMD in pre- (n = 83) and postmenopausal (n = 50) Chinese American and White women. Data were adjusted for weight, height, physical activity, total calcium intake, parathyroid hormone, and 25-hydroxyvitamin D levels. Among premenopausal women, lumbar spine trabecular vBMD was 5.8% greater in Chinese American versus White women (p = 0.01). At the hip, cortical vBMD was 3% greater at the femoral neck (p = 0.05) and 3.6% greater at the total hip (p = 0.01) in premenopausal Chinese American compared with White women. Among postmenopausal women, there was no difference in lumbar spine trabecular vBMD. Cortical vBMD was 4% greater at the total hip (p = 0.02) and tended to be greater at the femoral neck (p = 0.058) in Chinese American versus White women. Consistent with earlier findings in the peripheral skeleton, cortical vBMD is greater at the hip in Chinese American versus White women.

Recent insights into racial differences in bone and mineral metabolism

This study reviews recent insights into racial differences in bone from 2010 to 2011. Recent studies have focused on expanding our current understanding of responsible mechanisms for racial differences in osteoporotic fracture risk. Using newer, three-dimensional imaging techniques, these studies demonstrated that racial differences in bone mass and structure are apparent early in adolescence, even when accounting for differences in bone size and muscle mass by race. In addition, recent studies using genetic admixture analysis showed that greater percentage of African admixture was independently associated with higher bone mass and more favorable parameters of bone strength in children and adults. Furthermore, recent studies showed that the relationships between 25-hydoxyvitamin D and bone outcomes differed by race, with lower 25-hydroxyvitamin D levels being associated with lower bone quality and higher fracture risk in whites but not blacks. Racial differences in bone mass and strength are apparent early in life, are independently associated with genetic ancestry, and may be partly explained by differences in the relationships between vitamin D and bone metabolism. Further studies are needed to explore these findings, with the ultimate goal of better defining molecular and cellular mechanisms underlying racial differences in bone quality.

Radiographic evaluation of changes in the proximal phalanx of Thoroughbreds in race training

To evaluate changes in the cortical bone of the proximal phalanx of the fore-limbs of Thoroughbreds in response to training. Twenty-seven 2-year-old Thoroughbreds (20 females, 2 males, and 5 geldings). Horses were principally in training for races in a straight line and in a clockwise direction. Lateromedial and dorsopalmar radiographic views of each metacarpophalangeal joint were obtained before the horses started training and 1 year after starting exercise and racing. Width of the dorsal, palmar, lateral, and medial cortex and the width and thickness of the medulla were measured. Ratios (rather than absolute values) were used to remove the effect of differences in bone size among horses. 10 horses were lost from the study. Radiographs were obtained for 17 horses 1 year after starting training (9 horses raced in a clockwise direction, and 8 raced in clockwise and counterclockwise directions). There was no difference between the cortical bone in the right and left forelimbs at the start of the study. After training for 1 year, the palmar cortex in the right forelimb was significantly thicker than that in the left forelimb. The strain patterns, biomechanics of rapid exercise, and type of training most probably determined differences in the adaptive responses of the proximal phalanx. The data reported here can be used in the evaluation of weight-bearing distribution along the proximal phalanx and evaluation of the relationship between exercise and bone remodelling of the proximal phalanx.

Differences in volumetric bone mineral density (vBMD) at the radius and tibia in premenopausal Caucasian and Asian women

Current studies indicate that women of European origin have higher bone mineral density (BMD) than Far-East Asian women but few data exist on South Asian women. Roy et al (2005) explained differences in BMD between Caucasian and Asian women by differences in bone size. The aim of this study was to investigate differences between volumetric bone mineral density (vBMD) between Caucasian (C) and Asian (A) women. Thirty-five healthy premenopausal women (19 C and 16 A), age range 18-55 yrs, were studied. Peripheral Quantitative Computed Tomography (pQCT) measurements were taken at the radius and tibia (non-dominant) using a Stratec XCT 2000 pQCT scanner.

Gender differences in bone size, shape and strength parameters in patients with end-stage renal disease

Gender differences in bone size, shape and strength parameters in patients with end-stage renal disease

Bone Mass and Bone Size in Pre- or Early Pubertal 10-Year-Old Black and White South African Children and Their Parents

Genetic factors are thought to maintain bone mass in socioeconomically disadvantaged black South Africans. We compared bone mass between environmentally disadvantaged black and advantaged white children and their parents, after determining the most appropriate method by which to correct bone mineral content (BMC) for size. We collected data from 419 healthy black and white children of mean age 10.6 years (range 10.0-10.9), 406 biological mothers, and 100 biological fathers. Whole-body, femoral neck, lumbar spine, and mid- and distal one-third of radius bone area (BA) and BMC were measured by dual-energy X-ray absorptiometry. Power coefficients (PCs) were calculated from the linear-regression analyses of ln(BMC) on ln(BA) and used to correct site-specific BMC for bone size differences. Heritability (½h(2), %) by maternal and paternal descent was estimated by regressing children's Z scores on parents' Z scores. Correcting BMC for height, weight, and BA(PC) accounted for the greatest variance of BMC at all skeletal sites. In so doing, BMC in blacks was up to 2.6 times greater at the femoral neck and lumbar spine. Maternal and paternal heritability was estimated to be ~30% in both black and white subjects. These results may in part explain the lower prevalence of fragility fractures at the hip in black South African children when compared to whites. Heritability was comparable between environmentally disadvantaged black and advantaged white South African children and similar to that reported for Caucasians in other parts of the world.

Men with metabolic syndrome have lower bone mineral density but lower fracture risk—the MINOS study

Data on the association of the metabolic syndrome (MetS) with bone mineral density (BMD) and fracture risk in men are inconsistent. We studied the association between MetS and bone status in 762 older men followed up for 10 years. After adjustment for age, body mass index, height, physical activity, smoking, alcohol intake, and serum 25-hydroxycholecalciferol D and 17beta-estradiol levels, men with MetS had lower BMD at the hip, whole body, and distal forearm (2.2% to 3.2%, 0.24 to 0.27 SD, p < .05 to .005). This difference was related to abdominal obesity (assessed by waist circumference, waist-hip ratio, or central fat mass) but not other MetS components. Men with MetS had lower bone mineral content (3.1% to 4.5%, 0.22 to 0.29 SD, p < .05 to 0.001), whereas differences in bone size were milder. Men with MetS had a lower incidence of vertebral and peripheral fractures (6.7% versus 12.0%, p < .05). After adjustment for confounders, MetS was associated with a lower fracture incidence [odds ratio (OR) = 0.33, 95% confidence interval (CI) 0.15-0.76, p < .01]. Among the MetS components, hypertriglyceridemia was most predictive of the lower fracture risk (OR = 0.25, 95%CI 0.10-0.62, p < .005). Lower fracture risk in men with MetS cannot be explained by differences in bone size, rate of bone turnover rate and bone loss, or history of falls or fractures. Thus older men with MetS have a lower BMD related to the abdominal obesity and a lower risk of fracture related to hypertriglyceridemia. MetS probably is not a meaningful concept in the context of bone metabolism. Analysis of its association with bone-related variables may obscure the pathophysiologic links of its components with bone status.

Quantitative Computed Tomography Reveals the Effects of Race and Sex on Bone Size and Trabecular and Cortical Bone Density

To examine the effects of race and sex on bone density and geometry at specific sites within the proximal femur and lumbar spine, we used quantitative computed tomography to image 30 Caucasian American (CA) men, 25 African American (AA) men, 30 CA women, and 17 AA women aged 35–45 yr. Volumetric integral bone mineral density (BMD), trabecular BMD (tBMD), and cross sectional area were measured in the femoral neck, trochanter, total femur, and L1/L2 vertebrae. Volumetric cortical BMD (cBMD) was also measured in the femur regions of interest. Differences were ascertained using a multivariate regression model. Overall, AA subjects had denser bones than CA subjects, but there were no racial differences in bone size. Men had larger femoral necks but not larger vertebrae than women. The AA men had higher tBMD and cBMD in the femur than CA men, whereas AA women had higher femoral tBMD but not higher femoral cBMD than CA women. These data support the idea that higher hip fracture rates in women compared with men are associated with smaller bone size. Lower fracture rates in AA elderly compared with CA elderly are consistent with higher peak bone density, particularly in the trabecular compartment, and potentially lower rates of age-related bone loss rather than larger bone size.

Bone’s Structural Diversity in Adult Females Is Established before Puberty

Bone must be rigid for leverage yet light for mobility. We studied how bone modeling and remodeling fashioned differences in bone size, shape, and mass during growth to achieve these properties in adulthood. We measured the structural features of a tibial cross-section using quantitative computed tomography and markers of remodeling in 258 10- to 13-yr-old girls during 2 yr and in 108 of their mothers. Tibia total cross-sectional area and mass correlated between daughters and their mothers (r = 0.34 and 0.44, respectively, both P < 0.01). The location of a daughter's tibial total cross-sectional area, medullar area, and bone mass in the lower, middle, or upper part of the sample distribution was established before puberty and tracked during 2 yr (r = 0.84-0.94 first vs. last measurements' ranking). Tibial cross-sectional area correlated with medullar area (r = 0.69). Both areas correlated inversely with volumetric bone mineral density (r = -0.32 and -0.67, respectively; all P < 0.001), so larger cross-sections had a lower volumetric bone mineral density. The amount of bone deposited on the anterior and posterior periosteal surface during 2 yr was twice that deposited medially and laterally (P < 0.001), increasing strength more in the former than in the latter principal axis. Differences in skeletal size, shape, and mass in adulthood are likely to be largely established before puberty. We infer that bone fragility in advanced age has its structural antecedents partly established in early life.

Volumetric bone mineral density is an important tool when interpreting bone mineralization in healthy children

In adults, it is well known that gender influences bone mass, but studies in children have shown contradictory results. Also, conflicting results have been reported regarding bone mineral density in obese children. To investigate bone parameters in healthy 8-year-old children and relate them to anthropometry and self-reported physical activity (PA). Bone measurements were performed with dual X-ray absorptiometry in 96 children, and questionnaires were used to assess self-reported PA. Bone mineral content and density differed by gender. Eighteen percent of the children were overweight/obese and they had higher bone mineral content and density than children with normal weight. Bone mineral apparent density (g/cm(3)) of the lumbar spine did not differ, since the vertebral size differed, as was also the case between genders. Self-reported weight-bearing PA influenced bone mass in the hip. PA influenced bone mineralization at this age. The differences in bone mineral content and density in healthy children would mainly be explained by the differences in bone size, reflected in body height and the width of the vertebrae. This indicates the importance of determining volumetric bone mineralization in children.

Prevalence of Low Bone Mass in Relation to Estrogen Treatment and Body Composition in Male-to-Female Transsexual Persons

Bone health is a parameter of interest in the daily follow-up of male-to-female (M → F) transsexual persons both before and after sex reassignment surgery (SRS) due to an intensely changing hormonal milieu. We have studied body composition, areal, geometric, and volumetric bone parameters, using DXA and peripheral quantitative computed tomography at different sites in 50 M → F transsexual persons, at least 3 yr after the start of the hormonal treatment and 1 yr after SRS. In this cross-sectional study, hormone levels and markers of bone metabolism were assessed using immunoassays. Prevalence of low bone mass as defined by a Z-score ≤ −2.0 according to DXA criteria was 26% at lumbar spine and 2% at the total hip. We found no major differences in hormonal parameters between participants with a Z-score ≤ or > −2.0. Markers of bone turnover were comparable between subjects with or without low bone mass, indicating a stable bone turnover at the time of investigation. No significant differences in bone size or density were observed between patients on transdermal vs. oral estrogens. Low bone mass is not uncommon in M → F transsexual persons. Smaller bone size, and a strikingly lower muscle mass compared with men appear to underlie these findings.

Race and Diet Interactions in the Acquisition, Maintenance, and Loss of Bone

Racial differences in bone become apparent during puberty. Studies of areal bone mineral density (aBMD) generally show the greatest aBMD in African Americans followed by American white, Hispanic, and Native Americans, with the least aBMD in Asian Americans. Racial differences in fracture risk, however, do not exactly follow racial variation in aBMD. These group differences in bone mass are largely explained by differences in bone size, although calcium intake and physical activity are also significant predictors of aBMD and bone mineral content. Racial differences in calcium metabolism, as influenced by calcium and sodium intake, explain much of the black vs. white differences in skeletal calcium accretion during puberty. The relative importance of calcium and sodium in calcium metabolism has not yet been elucidated among Asians. Predictors of aBMD have been reported for African American and American white adults and predictors of aBMD in Chinese American women have recently been studied. Much remains to be studied regarding interactions between race and diet.

Gender Differences in Capitate Kinematics are Eliminated After Accounting for Variation in Carpal Size

Previous studies have found gender differences in carpal kinematics, and there are discrepancies in the literature on the location of the flexionextension and radio-ulnar deviation rotation axes of the wrist. It has been postulated that these differences are due to carpal bone size differences rather than gender and that they may be resolved by normalizing the kinematics by carpal size. The purpose of this study was to determine if differences in radio-capitate kinematics are a function of size or gender. We also sought to determine if a best-fit pivot point (PvP) describes the radio-capitate joint as a ball-and-socket articulation. By using an in vivo markerless bone registration technique applied to computed tomography scans of 26 male and 28 female wrists, we applied scaling derived from capitate length to radio-capitate kinematics, characterized by a best-fit PvP. We determined if radio-capitate kinematics behave as a ball-and-socket articulation by examining the error in the best-fit PvP. Scaling PvP location completely removed gender differences (P=0.3). This verifies that differences in radio-capitate kinematics are due to size and not gender. The radio-capitate joint did not behave as a perfect ball and socket because helical axes representing anatomical motions such as flexion-extension, radio-ulnar deviation, dart throwers, and antidart throwers, were located at distances up to 4.5 mm from the PvP. Although the best-fit PvP did not yield a single center of rotation, it was still consistently found within the proximal pole of the capitate, and rms errors of the best-fit PvP calculation were on the order of 2 mm. Therefore, the ball-and-socket model of the wrist joint center using the best-fit PvP is appropriate when considering gross motion of the hand with respect to the forearm such as in optical motion capture models. However, the ball-and-socket model of the wrist is an insufficient description of the complex motion of the capitate with respect to the radius. These findings may aid in the design of wrist external fixation and orthotics.

Gender differences in the ratio between humerus width and length are established prior to puberty

SummaryOn a sample of 1,317 children aged 9.9 years we developed a novel method of measuring humeral dimensions from total body dual-energy X-ray absorptiometry (DXA) scans and showed that gender differences in the ratio between humeral width and length are established prior to puberty.IntroductionIt is recognised that long bone cross-sectional area is greater in males compared to females, which is thought to reflect more rapid periosteal bone growth in boys. However, it is currently unclear whether these findings reflect gender differences in bone size or shape. In the present study, we investigated whether gender differences exist in the balance between longitudinal and periosteal long bone growth in children, leading to gender differences in bone shape, based on a novel method for evaluating shape of the humerus. We also examined whether these differences are established prior to puberty.MethodsLength, area and width of the humerus were estimated from total body DXA scans in 1,317 children aged 9.9 ± 0.33 years, who had participated in a nested case-control study of fractures within the Avon Longitudinal Study of Parents and Children (ALSPAC) (a geographically based birth cohort based in South West England). No differences were observed with respect to parameters of humeral geometry according to fracture history, and so both groups were pooled for further analysis. Aspect ratio (AR) of the humerus was calculated as humeral width divided by length. Total body height and weight were measured at the same time as the DXA scan. Puberty was assessed using self-completion questionnaires.ResultsHumeral width and length were positively associated with age and height in boys and girls combined (P < 0.001), and with Tanner stage in girls (P < 0.002). In contrast, age, height and Tanner stage were not related to humeral AR. We then examined gender differences in humeral shape according to pubertal stage. In prepubertal children (i.e. Tanner stage 1), humeral length was similar in boys and girls, but width (1.92 vs 1.88 cm, P < 0.001) and area (47.7 vs 46.9 cm2, P < 0.001) were greater in boys, resulting in a greater AR (7.78 vs 7.53, P < 0.001). Similar gender differences were observed in early pubertal children (i.e. Tanner stage 2).ConclusionWe conclude that the greater periosteal diameter of boys compared to girls reflects differences in the balance between longitudinal and periosteal bone growth. Interestingly, resulting gender differences in humeral AR are established in prepubertal children.

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

The aim of this study was to provide normative data of bone mineral density (BMD; g/cm(2)) 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. 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. There was no difference in calcaneus BMD when comparing boys and girls, whereas the boys had 4.5% (0.013 g/cm(2)) higher forearm BMD than the girls (P < 0.001). Calcaneal BMD (mean 0.318 g/cm(2)) was 11% higher than forearm BMD (mean 0.283 g/cm(2)). 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. 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.

Differences in bone size and bone mass between black and white 10-year-old South African children

Black and white South Africans hail from vastly disparate cultural and socio-economic backgrounds the result of which exposes black children to numerous factors known to impact negatively on bone mass. Thus, we studied ethnic differences in bone size and bone mass between 476 10-year-old black and white South African girls and boys (black boys n=182, white boys n=72, black girls n=158, white girls n=64) who formed part of a longitudinal cohort of children born in Johannesburg, South Africa, during 1990. Bone area (BA) and bone mineral content (BMC) were measured at the whole body, total hip, femoral neck, lumbar spine (L1-L4) and mid- and distal radii by dual energy X-ray absorptiometry (DXA). Vertebral heights and metacarpal indices were measured. Anthropometry, skeletal maturity and pubertal development were also assessed. After correction for height, weight, gender and puberty, black children had greater BMC at the femoral neck (P<0.0001), total hip (P<0.05) and mid-radius (P<0.001) than white children.. At the whole body, lumbar spine, and distal one-third of the radius, there were no differences in BMC between black and white children after correction for differences in body size. After correction for height and puberty, vertebral heights were less in black children than white children, and cortical areas at the second metacarpal were greater in black children. These findings suggest that, at the femoral neck, total hip and mid-radius, these differences are not a result of differences in anthropometry, bone age or pubertal stage, or environmental factors but are most likely to result from genetic differences.

High and low density in the same bone: a study on children and adolescents with mild osteogenesis imperfecta

Children and adolescents with osteogenesis imperfecta (OI) generally have low bone mineral density (BMD) at the lumbar spine and hip. However, the effects of the disease on diaphyseal bone have not been well characterized, even though long-bone fractures are common in such patients. In this study on 42 fully mobile children and adolescents with mild OI (age 6–19 years; 17 girls), lumbar spine, radius (metaphysis and diaphysis) and second metacarpal (diaphysis) were analyzed using dual-energy X-ray absorptiometry, peripheral quantitative computed tomography and radiogrammetry, respectively. Bone mineral content at the lumbar spine, radial metaphysis and radial diaphysis was between 25% and 31% lower than in age-matched healthy children and adolescents. At the lumbar spine and radial metaphysis, bone size (as estimated from projection area and cross-sectional area, respectively) was normal or only slightly below the results expected for healthy individuals, whereas bone size was very small at the diaphyseal sites of the radius and the second metacarpal. Total volumetric BMD is defined as the ratio between bone mineral content and bone volume. Therefore, these differences in bone size between skeletal locations led to markedly discrepant results for total volumetric BMD. Total volumetric BMD was low at the lumbar spine (23% below result expected for healthy subjects of the same age) and the radial metaphysis (− 15%) but elevated at the radial diaphysis (+ 25%; all differences to controls significant at P < 0.001). Despite high volumetric BMD, estimated bending strength at the radial diaphysis was very low. These results demonstrate that volumetric BMD can be abnormally high and low within the same bone in the same individual and highlight the fact that volumetric BMD at diaphyseal sites does not provide a good estimate of bone strength when bone size is abnormal.

Examining Bone Surfaces Across Puberty: A 20-Month pQCT Trial

This follow-up study assessed sex differences in cortical bone growth at the tibial midshaft across puberty. In both sexes, periosteal apposition dominated over endosteal resorption. Boys had a greater magnitude of change at both surfaces, and thus, a greater increase in bone size across puberty. Relative increase in cortical bone area was similar between sexes. Generally, sex differences in bone size become most evident as puberty progresses. This was thought to be caused, in part, by greater periosteal apposition in boys, whereas endosteal apposition prevailed in girls. However, this premise is based on evidence from cross-sectional studies and planar measurement techniques. Thus, our aim was to prospectively evaluate sex-specific changes in cortical bone area across puberty. We used pQCT to assess the tibial midshaft (50% site) at baseline and final (20 months) in girls (N = 68) and boys (N = 60) across early-, peri-, and postpuberty. We report total bone cross-sectional area (ToA, mm2), cortical area (CoA, mm2), marrow cavity area (CavA, mm2), and CoA/ToA ratio. Children were a mean age of 11.9 +/- 0.6 (SD) years at baseline. At the tibia, CoA ranged from 230 +/- 44, 261 +/- 50, and 258 +/- 46 in early-, peri-, and postpubertal girls. In boys, comparable values were 223 +/- 36 (early), 264 +/- 38 (peri), and 281 +/- 77 (postpubertal). There was no sex difference for ToA or CoA at baseline. Increase in ToA and CoA was, on average, 10% greater for boys than girls across maturity groups. The area of the marrow cavity increased in all groups, but with considerable variability. The increase in CavA was significantly less for girls than boys in the early- and postpubertal groups. Change in CoA/ToA was similar between sexes across puberty. Both sexes showed a similar pattern of change in CoA at the tibial midshaft, where periosteal apposition dominated over endosteal resorption. Boys showed a greater magnitude of change at both surfaces, and thus, showed a greater increase in bone size across puberty. The relative increase in cortical area was similar between sexes. These pQCT findings provide no evidence for endosteal apposition in postmenarchal girls.