Initial years of recreational artistic gymnastics training improves lumbar spine bone mineral accrual in 4- to 8-year-old females.

Gymnasts' bone mineral characteristics are generally not known before starting their sport. Prepubertal females who enrolled in beginning artistic gymnastics (n = 65) had lower bone mineral than controls (n = 78). However, 2 years of gymnastics participation versus no participation led to a significantly greater accrual of forearm bone area and lumbar spine areal BMD. INTRODUCTION: The skeletal response to exercise in children compared with adults is heightened because of the high bone turnover rate and the ability of bone to change its size and shape. Whereas child gymnasts generally have greater rates of bone mineral accrual compared with nongymnasts, it is unknown if some of these skeletal advantages are present before the onset of training or are caused entirely by training. MATERIALS AND METHODS: Changes in bone area (BA; cm2), BMC (g), and areal BMD (aBMD; g/cm2) over 24 months were examined in prepubertal females, 4-8 years of age, who selected to perform recreational gymnastics (GYM; n = 65), nongymnastic activities, or no organized activity (CON; n = 78). Participants had essentially no lifetime history of organized athletic participation (< 12 weeks). Pubertal maturation was assessed annually by a physician. Total body, lumbar spine, total proximal femur, and forearm BA, BMC, and aBMD were measured every 6 months using DXA (Hologic QDR-1000W). Independent samples t-tests determined baseline group differences. Nonlinear mixed effects models were used to model 24-month changes in bone data. In subset analyses, high-level gymnasts advancing to competition (HLG; n = 9) were compared with low-level nonadvancing gymnasts (LLG; n = 56). RESULTS: At baseline, GYM were shorter, lighter, and had lower BA, BMC, and aBMD compared with CON (p < 0.05), whereas HLG did not differ significantly in these measurements compared with LLG (p > 0.05). Controlling for differences in race, baseline measures of body mass, height, and calcium intake, and change in breast development beyond stage II at 24 months, GYM had greater long-term (asymptotic) mean responses for total body aBMD and forearm BMC (p < 0.04) and greater rates of increase in the mean responses of lumbar spine aBMD and forearm BA compared with CON over 24 months. Over time, forearm BA increased to a greater extent in HLG compared with LLG (p < 0.01). CONCLUSIONS: Females participating in recreational gymnastics initiated during childhood have enhanced bone mineral gains at the total body, lumbar spine, and forearm over 24 months. Higher-level training promotes additional gains in forearm BA.     

Differences in bone mineral density,bone mineral content,and bone areal size in fracturing and non-fracturing women,and their interrelationships at the spine and hip

Osteoporotic fractures are a major public health problem, particularly in women. Bone mineral density (BMD), bone mineral content (BMC), and bone size have been regarded as important determinants of osteoporotic fractures. In 1449 women over age 30 years, we studied the detailed relationship, at the spine and hip, between BMD, BMC, and bone areal size (all measured by dual-energy X-ray absorptiometry) and compared their relative magnitudes in fracturing and non-fracturing individuals. We find that, (1) BMD and BMC are significantly higher at the spine and hip in non-fracturing women. Bone areal size is significantly larger at the spine in non-fracturing women; however, the significance disappears when adjustment is made for the significant difference of height (stature) between fracturing and non-fracturing women. In contrast to the spine, bone areal size is always significantly largerin fracturing women at the hip. (2) The relationship among BMD, BMC, and bone areal size is different at the spine and hip. Specifically, at the spine, BMD increases with bone areal size linearly. At the hip, BMD has a quadratic relationship with bone areal size, so that BMD increases at lower bone areal sizes, then (after an intermediate zone of values) decreases with increasing bone areal size. However, BMD adjusted for BMC always decreases with increasing bone areal size, as expected by the definition of BMD. With no adjustment for BMC, the increase in BMD with bone areal size is due to a more rapid increase of BMC than increasing bone areal size, thus explaining the observations of association of both larger BMD and larger bone areal size with stronger bone. (3) At the spine, 86.2% of BMD variation is attributable to BMC and 12.6% to bone areal size. At the hip, 98.0% of BMD variation is due to BMC and 1.1% due to bone areal size. The current study may be important in understanding the relationship among BMD, BMC, and bone size as risk determinants of osteoporotic fractures.     

Jumping improves hip and lumbar spine bone mass in prepubescent children: a randomized controlled trial.

Physical activity during childhood is advocated as one strategy for enhancing peak bone mass (bone mineral content [BMC]) as a means to reduce osteoporosis-related fractures. Thus, we investigated the effects of high-intensity jumping on hip and lumbar spine bone mass in children. Eighty-nine prepubescent children between the ages of 5.9 and 9.8 years were randomized into a jumping (n = 25 boys and n = 20 girls) or control group (n = 26 boys and n = 18 girls). Both groups participated in the 7-month exercise intervention during the school day three times per week. The jumping group performed 100, two-footed jumps off 61-cm boxes each session, while the control group performed nonimpact stretching exercises. BMC (g), bone area (BA; cm2), and bone mineral density (BMD; g/cm2) of the left proximal femoral neck and lumbar spine (L1-L4) were assessed by dual-energy X-ray absorptiometry (DXA; Hologic QDR/4500-A). Peak ground reaction forces were calculated across 100, two-footed jumps from a 61-cm box. In addition, anthropometric characteristics (height, weight, and body fat), physical activity, and dietary calcium intake were assessed. At baseline there were no differences between groups for anthropometric characteristics, dietary calcium intake, or bone variables. After 7 months, jumpers and controls had similar increases in height, weight, and body fat. Using repeated measures analysis of covariance (ANCOVA; covariates, initial age and bone values, and changes in height and weight) for BMC, the primary outcome variable, jumpers had significantly greater 7-month changes at the femoral neck and lumbar spine than controls (4.5% and 3.1%, respectively). In repeated measures ANCOVA of secondary outcomes (BMD and BA), BMD at the lumbar spine was significantly greater in jumpers than in controls (2.0%) and approached statistical significance at the femoral neck (1.4%; p = 0.085). For BA, jumpers had significantly greater increases at the femoral neck area than controls (2.9%) but were not different at the spine. Our data indicate that jumping at ground reaction forces of eight times body weight is a safe, effective, and simple method of improving bone mass at the hip and spine in children. This program could be easily incorporated into physical education classes.     

体重、身高对成都地区青壮年腰椎、髋部骨量的影响

目的　研究体重、身高对青壮年腰椎、髋部骨量的影响。方法　随机抽取成都地区年龄在 2 0～ 39岁 ,排除心肝肺肾、内分泌等慢性病、骨代谢疾病及脊椎畸形者 2 37名 (其中男性 10 8名 ,女性 12 9名 ) ,采用美国Lunar公司生产DPX L型双能X线骨密度仪测定受试者腰椎和髋部的骨矿含量 (BMC)、面积 (AREA)、骨密度 (BMD)。全部资料输入微机 ,用SPSS软件进行统计学处理。结果　体重、身高、体重指数 (BMI)与腰椎、髋部的BMC、Area、BMD呈正相关 ,其中体重与腰椎、髋部的BMC、Area中等程度相关 (r=0 39～ 0 5 5 ,P <0 0 1) ,身高与腰椎 (L2 - 4)AREA相关性最好 (r=0 75 8,P <0 0 1) ,体重、身高与BMD相关性差 (r=0 15 2～ 0 2 2 5 ,P <0 0 5 )。男性腰椎及髋部的BMC、AREA均明显高于同年龄组女性 (P <0 0 1) ,男、女L2 - 4BMD无显著性差异 (P >0 0 5 ) ,男性略低于女性。L2 - 4BMC与体重比值及L2 - 4AREA与体重比值 ,男、女无显著性差异 (P >0 0 5 )。L2 - 4Area与身高比值男性明显高于女性 (P <0 0 1)。结论　体重对青壮年BMC的影响大于身高 ,身高对L2 - 4AREA影响最大 ,男、女体重、身高的差异决定了峰值骨量的差异。BMC、Area、BMD 3项指标中 ,BMC更能反映体重、身高的差异 ,用BMC诊断骨质疏松     

Measurement of bone in the os calcis: a clinical evaluation

Bone mineral content (BMC) was measured in the os calcis of 232 normal subjects aged 17-82 years. The mean reproducibility (coefficient of variation) of the measurement was 1.8%. Substantial bone loss occurred between the ages of 20 and 50 years, and in females the menopause was associated with additional bone loss. There was no significant difference in the rate of bone loss in females and males, but the mean BMC was greater at all ages in males than in females. We also compared os calcis BMC with spinal bone mineral density (BMD), measured by quantitative computed tomographic (CT) scanning, in 85 subjects: 33 were normal controls, 19 had osteoporosis defined by the presence of one or more pathological fractures, and in the remainder the CT examination was performed at the patient's request. Os calcis BMC correlated with spinal BMD in both females (r = 0.69, p less than 0.001) and males (r = 0.84, p less than 0.001). However, the os calcis BMC did not reliably predict spine values around the CT "fracture threshold" of 90-100 mg/cm3 and did not correlate with osteoporotic fracture as well as did spinal BMD. It is concluded that measurement of the os calcis BMC is of limited clinical usefulness for the early diagnosis of osteoporosis.     

Frame size, ethnicity, lifestyle, and biologic contributors to areal and volumetric lumbar spine bone mineral density in Indian/Pakistani and American Caucasian premenopausal women.

Published data on the spinal bone mineral density (BMD) of premenopausal women originating from the Indian subcontinent (Indian/Pakistani) are few. We compared anteroposterior (AP) and lateral areal BMD (aBMD) using dual X-ray absorptiometry and calculated volumetric BMD (vBMD) in Indian/Pakistani (n = 47) vs American (n = 47) women with dissimilar statures and skeletal sizes. To account for differences, we "adjusted" lumbar aBMD separately for vertebral size (aBMD/the square root of the projected area), height (aBMD/height), and hip skeletal width (aBMD/hip width). We "corrected" bone mineral content (BMC), aBMD, and vBMD for frame size, collectively using height, hip width, and vertebral size. Unadjusted mean aBMD values for AP lumbar (L1-L4, p = 0.0086; L3-L4, p = 0.044) spine were higher in Americans than Indians/Pakistanis,whereas lateral vBMD (p = 0.56) or aBMD (p = 0.060) values were not different. After adjusting for height, hip width, or vertebral size, or correcting for frame size, differences in aBMD disappeared. Regression analyses indicated that the best measures to correct for frame size were: vertebral area for BMC, hip width for aBMD, and vertebral width for lateral vBMD. Height was not significant in any model. In correcting for frame size, we accounted for 73-85% of the variability in BMC, 22-28% in aBMD, and 27% in lateral vBMD. After frame size was corrected, we accounted for 34% of the variability in AP BMC and aBMD, in contrast with 6-9% in the lateral models. Five significant biologic and lifestyle factors remained in AP models; only body weight remained for lateral spine. Upon accounting for frame size using regression, much variability in BMD, aBMD, and vBMD was explained by lifestyle and biologic factors, not by ethnicity.     

Rural versus nonrural differences in BMC, volumetric BMD, and bone size: a population-based cross-sectional study

Despite reports of lower fracture risk among rural versus urban populations, few studies have investigated rural versus urban differences in bone mineral content (BMC) and bone mineral density (BMD). Population differences in cross-sectional bone geometry and understanding lifestyle factors responsible for these differences may reveal insights into the reason for differences in fracture risk. We hypothesized that if lifestyle differences in bone mass, size, and geometry are a result of muscle strength, activity, or dietary differences, Hutterite and rural populations should have greater bone mass compared to nonrural populations. The study population consisted of 1189 individuals: 504 rural Hutterites (188 men), 349 rural individuals (>75% life farming, 184 men), and 336 nonrural individuals (never lived on farm, 134 men) aged 20 to 66 years. BMC, bone area, and areal BMD (aBMD) of the total body (TB), hip, femoral neck (FN), and spine by DXA; volumetric BMD (vBMD) and bone geometry at the 4% and 20% radius; polar stress strain index (pSSI), a measure of bone strength, at the 20% pQCT site; and strength, 7-day activity recall, and 24-h diet recall were collected and compared among groups. Hutterite women and men had greater grip strength compared to rural and nonrural populations (both, P < 0.001). Rural women had greater activity versus Hutterite and nonrural (P < 0.001), while both Hutterite and rural men had greater activity than nonrural (P < 0.001). Hutterite and rural populations tended to have greater BMC and areal size than the nonrural population, while Hutterites had greater BMC and areal size than rural population at some (TB, FN for females only), but not all (proximal hip), sites. Cortical vBMD was inversely associated with periosteal circumference at the 20% radius in women (r = −0.25, P < 0.001) and men (r = −0.28, P < 0.001) and was higher in nonrural versus Hutterite and rural men. Hutterite and rural women and men had greater pSSI at the 20% radius compared to nonrural; inclusion of strength measurements explained population differences among women, but not men. Lifestyle differences did not explain population differences in BMC, aBMD, vBMD, or bone size.     

The structural basis of bone fragility in men.

Understanding of the pathogenesis of bone fragility in men requires knowledge of its structural basis. There is no evidence that gender differences in fracture rates are explained by gender differences in bone mineral content (BMC) or areal bone mineral density (BMD). This is an untested assumption. The BMD measurement integrates the modeling and remodeling that occurs on the periosteal and endosteal surfaces of bone during growth and aging. The size, shape, and architecture of the bone so formed determine its breaking strength. None of these three-dimensional structural components is "seen" by the dual photons of the densitometer. Men and women attain a similar peak vertebral height during growth. Vertebral width is greater in men, conferring higher BMC and areal BMD, but trabecular number and thickness (trabecular volumetric BMD) is no greater in men than women. Blacks have shorter vertebra than whites, and vertebral width is similar. Trabecular thickness is greater in blacks than whites. Thus, at peak, gender differences in vertebral strength are likely to be size, not BMD, dependent. Racial differences in vertebral strength are likely to be BMD, not size, dependent. Greater periosteal expansion during growth in males than females, and blacks than whites, establishes the gender and racial differences in peak bone size. Men have wider long bones than women. Blacks have wider long bones than whites. The proximity of the endocortical surface to the periosteal surface determines peak cortical width, which is similar in men, women, blacks, and whites. It is the greater distance of the cortical mineral mass from the neutral axis of a long bone in males than in females, in blacks than in whites, and in men with, than men without, fractures, that partly accounts for the greater bone strength in the first mentioned in each group. Thus, at peak, racial and gender differences in long bone strength are likely to be size, not BMD dependent. Trabecular bone loss is similar in men and women. Loss of connectivity is greater in women. Endocortical resorption is greater in women than men, but men lose less cortical width because subperiosteal apposition during aging is greater in men than in women offsetting endocortical resorption. Men with spine fractures have smaller vertebrae because vertebral width is less. Men with hip fractures have smaller femoral neck width. In both types of fractures, there is less bone in the smaller bone-reduced volumetric BMD. The relative contributions of reduced accrual during growth, excessive bone loss during aging, or both to the deficit in volumetric BMD are undefined. No antifracture efficacy trials have been done in men. Reasonable approaches to treatment include the use of testosterone in hypogonadal men, and vitamin D if vitamin D deficiency is present. Calcium supplements may slow endocortical bone loss. Bisphosphonates may increase BMD.     

The effects of gonadectomy on bone size, mass, and volumetric density in growing rats are gender-, site-, and growth hormone-specific.

Peak volumetric bone mineral density (BMD) is determined by the growth in bone size relative to the mineral accrued within its periosteal envelope. Thus, reduced peak volumetric BMD may be the result of reduced mineral accrual relative to growth in bone size. Because sex steroids and growth hormone (GH) influence bone size and mass we asked: What are the effects of gonadectomy (Gx) on bone size, bone mineral content (BMC), areal and volumetric BMD in growing male and female rats? Does GH deficiency (GH-) reduce the amount of bone in the (smaller) bone, i.e., reduce volumetric BMD? Does GH- alter the effect of Gx on bone size and mineral accrual? Gx or sham surgery was performed at 6 weeks in GH- and GH replete (GH+) Fisher 344 male and female rats. Changes in bone size, volume, BMC, areal and volumetric BMD, measured using dual X-ray absorptiometry (DPX-L), were expressed as percentage of controls at 8 months (mean +/- SEM). All results shown were significant (p < 0.05 level) unless otherwise stated. In GH+ and GH- males, respectively, Gx was associated with: lower femur volume (24%, 25%), BMC (43%, 45%), areal BMD (21%, 14%), and volumetric BMD (30%, 28%); lower spine (L1-L3) volume (26%, 28%), BMC (26%, 30%), and areal BMD (28%, 12%), but not volumetric BMD. Following Gx, GH+ females had increased femur volume (11%), no effect on BMC, decreased areal BMD (6%) and decreased volumetric BMD (17%); GH- females had no change in femur volume, but decreased femur BMC (24%), areal BMD (10%), and volumetric BMD (25%). In GH+ and GH- females, respectively, Gx was associated with a decrease in spine (L1-L3) BMC (12%, 15%), areal BMD (16%, 15%), and volumetric BMD (10%, 16%) with no change in volume. Deficits in non-Gx GH- relative to non-Gx GH+ (males, females, respectively) were: femur BMC (49%, 37%), areal BMD (23%, 8%), volume (19%, 19%) and volumetric BMD (37%, 22%); spine (L1-L3) BMC (46%, 42%), areal BMD (37%, 43%), volume (10%, 15%), and volumetric BMD (40%, 33%). Testosterone and GH are growth promoting in growing male rats, producing independent effects on bone size and mass; deficiency produced smaller appendicular bones with reduced volumetric BMD because deficits in mass were greater than deficits in size. At the spine, the reduction in size and accrual were proportional, resulting in a smaller bone with normal volumetric BMD. In growing female rats, estrogen was growth limiting at appendicular sites; deficiency resulted in a GH-dependent increase in appendicular size, relatively reduced accrual, and so, reduced volumetric BMD in a bigger bone. At the spine, accrual was reduced while growth in size was normal, thus volumetric BMD was reduced in the normal sized bone. Understanding the pathogenesis of low volumetric BMD requires the study of the differing relative growth in size and mass of the axial and appendicular skeleton in the male and female and the regulators of the growth of these traits.     

Increased fat mass is associated with increased bone size but reduced volumetric density in pre pubertal children

Recent studies have shown that obesity is associated with an increased risk of fracture in both adults and children. It has been suggested that, despite greater bone size, obese individuals may have reduced true volumetric density; however this is difficult to assess using two dimensional techniques such as DXA. We evaluated the relationship between fat mass, and bone size and density, in a population cohort of children in whom DXA and pQCT measurements had been acquired. We recruited 530 children at 6 years old from the Southampton Women's Survey. The children underwent measurement of bone mass at the whole body, lumbar spine and hip, together with body composition, by DXA (Hologic Discovery, Hologic Inc., Bedford, MA, USA). In addition 132 of these children underwent pQCT measurements at the tibia (Stratec XCT2000, Stratec Biomedical Systems, Birkenfeld, Germany). Significant positive associations were observed between total fat mass and both bone area (BA) and bone mineral content (BMC) at the whole body minus head, lumbar spine and hip sites (all p<0.0001). When true volumetric density was assessed using pQCT data from the tibia, fat mass (adjusted for lean mass) was negatively associated with both trabecular and cortical density (β=-14.6 mg/mm(3) per sd, p=0.003; β=-7.7 mg/mm(3) per sd, p=0.02 respectively). These results suggest that fat mass is negatively associated with volumetric bone density at 6 years old, independent of lean mass, despite positive associations with bone size.     

Bone density interpretation and relevance in Caucasian children aged 9-17 years of age: insights from a population-based fracture study.

The interpretation of bone density measurement in children is difficult due to a number of factors including rapid change in body size and uncertain clinical significance of bone density in children. This study asked two questions. (1) Is there a preferred bone density measurement site or type for fracture risk in children? (2) What is the best way to interpret bone density in children? This population-based case control study included 321 upper limb fracture cases and 321 class- and sex- matched randomly selected controls. Bone density at the hip, spine, and total body (including the arm) was measured by a Hologic QDR2000 densitometer (Waltham, MA) and examined as bone area (BA), bone mineral content (BMC), bone mineral density (BMD), bone mineral apparent density (BMAD), and BMC/lean mass (BMCLM). The only dual-energy X-ray absorptiometry (DXA) variables that were consistently associated with fracture risk in both boys and girls were spine BMD and BMAD for total upper limb fractures, and spine and hip BMAD for wrist and forearm fractures. No significant associations were observed for BA and BMCLM and inconsistent associations for BMC and other BMD sites. Five-yr fracture risk varied from 15–24% depending on site and gender in a child with a Z-score of -3. In the controls, all DXA variables were associated with age, height, and weight, but the weakest associations were with BMAD. In conclusion, in this study the spine BMAD had the strongest and most consistent association with upper limb fracture risk in children. The associations with age and body size imply that age specific Z-scores will be the most convenient for interpretation of DXA measures in children. Five-yr wrist and forearm fracture risk has potential as a clinical endpoint of immediate relevance.     

Heterogeneity of fracture pathogenesis in urban South African children: the birth to twenty cohort

South African black children fracture less than white children. Differences in bone mass, body composition, and physical activity may be contributing risk factors. This study aimed to investigate the association between fracture prevalence, bone mass, and physical activity in South African children. Using the Bone Health cohort of the Birth to Twenty longitudinal study, we retrospectively obtained information of lifetime fractures until age 15 years in 533 subjects. Whole-body bone mineral content (BMC), bone area (BA), fat mass (FM), and lean mass (LM) (measured by dual-energy X-ray absorptiometry [DXA]), anthropometric data, physical activity scores, and skeletal maturity were obtained at ages 10 and 15 years. Nonfracturing black females were used as the control group and comparisons were made between those who did and did not fracture within the same sex and ethnic groups. Of the 533 subjects, 130 (24%) reported a fracture (black, 15%; white, 41.5%; p < 0.001). White males who fractured were significantly taller (10 years, p < 0.01), more physically active (15 years, p < 0.05) and had higher LM (10 years, p = 0.01; 15 years, p < 0.001), whereas white females who fractured were fatter (10 and 15 years, p = 0.05 and p < 0.05, respectively), than their nonfracturing peers. White males who fractured had greater BA and BMC at all sites at 10 and 15 years compared to their nonfracturing peers after adjusting for differences in height and weight; BA and BMC were similar in each of the other sex and ethnic groups. No anthropometric or bone mass differences were found between black children with and without fractures. The factor associated with fractures in white males appears to be participation in sports activities, while in white females obesity appears to play a role. No contributing factors in black males and females were found, and needs further elucidation.     

Positive, site-specific associations between bone mineral status, fitness, and time spent at high-impact activities in 16- to 18-year-old boys

The incidence of hip and forearm fracture in elderly men in the United Kingdom is a public health issue, but there is limited knowledge on lifestyle factors affecting male bone health. The aim of this cross-sectional study was to evaluate the relationships between whole body and regional bone mineral status and self-reported participation time in no-, low-, moderate-, and high-impact activities and fitness measurements in 16- to 18-year-old boys. One hundred twenty-eight boys underwent absorptiometry (DXA) measurements (Hologic QDR 1000W) of bone mineral content (BMC), bone area (BA), and bone mineral density (BMD) at the whole body, hip, spine, and forearm. They also completed the EPIC (European Prospective Investigation of Cancer) physical activity questionnaire, which allowed categorization of activities according to impact and aerobic intensity. Fitness and strength were assessed in each subject using estimated VO2 max, grip strength, and back strength. Significant positive relationships were found between BMC, BA, and BMD and the fitness and strength measurements and participation time in high-impact sports at most skeletal sites. The relationships were further examined after adjustment of BMC for height, weight, and bone area, thereby minimizing the influence of body and bone size on these relationships. VO2 max was a significant positive determinant of size-adjusted BMC at the whole body, the ultradistal and one-third radius, and all the hip sites, except the trochanter. Size-adjusted BMC at the forearm sites and trochanter was significantly positively associated with grip strength. Size-adjusted BMC at the whole body and all the hip sites was significantly positively associated with time spent at high-impact activities. Differences in size-adjusted BMC across thirds of time spent at high-impact activities were also examined. Boys in the highest third of high-impact activity had significantly greater size-adjusted whole body BMC and total hip BMC compared to subjects in the lowest third [+3.4 (1.2)% for whole body and +8.5 (2.2)% for hip, both P = 0.001]. Boys in the highest third of high-impact activity spent most activity time jogging, playing tennis, football and rugby, basketball, and exercising with weights. Back strength and lean mass were significantly greater in subjects in the highest third compared to those in the middle (P = 0.02) and lowest third (P = 0.03). No significant differences were found between subjects in each third of high-impact activity for potential confounders including TV viewing, calcium intake, body fat, and height. These findings indicate that participation of male adolescents in a range of high-impact activities for 1 h or more a day is associated with greater bone size and mineral content, especially at the hip.     

A tibial shaft fracture sustained in childhood or adolescence does not seem to interfere with attainment of peak bone density.

High peak bone mass or density in early adulthood is an important protective factor against osteoporotic fractures in later life, but it is not known whether injuries on growing bones affect the attainment of peak bone mass and density. The purpose of this study was therefore to examine with dual-energy X-ray absorptiometry the areal bone mineral density (BMD) of the injured and uninjured extremity (the femoral neck, trochanter area of the femur, distal femur, patella, proximal tibia, and distal tibia), lumbar spine, and distal radius of young adults with a history of early life tibial shaft fracture and to find out whether the fracture had affected the attainment of peak bone density of these patients. The second objective was to clarify whether any background or clinical follow-up variable would predict the BMD difference between the affected and unaffected extremity. Thus, the BMD and clinical status of 45 patients (34 men and 11 women), who had sustained a tibial shaft fracture in childhood or in adolescence (between 7 and 15 years of age) an average 11 years before the study, were examined. The results showed that the fracture had created a small but statistically significant injured-to-uninjured side BMD difference (proximal tibia -1.7%; p = 0.011, and distal tibia 2.6%; p = 0.014), while the other sites showed no significant side-to-side differences. There were neither significant differences in the spinal or radial BMDs between the patients and their age-, height-, and weight-matched healthy controls. A further analysis of the data showed that the better the muscle strength in the injured lower limb, the lower the side-to-side BMD deficit in the proximal tibia of the same limb (r = 0.51; p < 0.001). Smoking had a significant association with the relative BMD in the injured distal tibia (mean injured-to-uninjured side BMD difference: smokers 6.1% vs. nonsmokers -0.6%, p = 0.016). Also patient's age at the time of the injury showed an association: the younger the patient at the time of the injury, the lower the side-to-side BMD deficit in the injured distal tibia (r = -0.35; p = 0.048). In conclusion, this study indicates that early life tibial fracture leads to a small long-term BMD deficit in the fractured bone while the other sites of the skeleton seem not to be affected. Thus, a tibial shaft fracture sustained in childhood or adolescence seems to only marginally interfere the attainment of peak bone density, the important predictor of the osteoporotic fractures in later life.     

Sexual dimorphism affects tibia size and shape but not tissue-level mechanical properties

Understanding how growth influences adult bone morphology and tissue quality should provide important insight into why females show a greater incidence of stress fractures early in life and fragility fractures later in life compared to males. The objective of this study was to test whether females acquire similar tissue-level mechanical properties as males by the time peak bone properties are established. Standardized beams of bone were machined from the tibial diaphyses of 14 young, adult females ranging in age from 22 to 46 years. Data for males (n=17, age=17-46 years) were taken from a prior study. Measures of tissue-level mechanical properties, including stiffness, strength, ductility, toughness, and damageability, were compared between sexes using t-tests. The relationship between cross-sectional morphology and tissue-level mechanical properties was also examined. Males and females showed nearly identical tissue-level mechanical properties. Both sexes also showed similar age-related degradation of mechanical properties and a similar relationship between cross-sectional morphology and tissue quality. However, for all body sizes, female tibiae were smaller relative to body size (i.e., less robust) compared to males. The results indicated that sex-specific growth patterns affected transverse bone size, but did not affect tissue-level mechanical properties. This, combined with the observation that young, adult female long bones are undersized relative to body size, suggests that adult females would be expected to accumulate more damage under intense loading compared to males. This may be a contributing factor to the greater incidence of stress fractures observed for female military recruits.     

Characterization of low bone mass in young patients with thalassemia by DXA, pQCT and markers of bone turnover

Previous reports using dual x-ray absorptiometry (DXA) suggest that up to 70% of adults with thalassemia major (Thal) have low bone mass. However, few studies have controlled for body size and pubertal delay, variables known to affect bone mass in this population. In this study, bone mineral content and areal density (BMC, aBMD) of the spine and whole body were assessed by DXA, and volumetric BMD and cortical geometries of the distal tibia by peripheral quantitative computed tomography (pQCT) in subjects with Thal (n = 25, 11 male, 10 to 30 years) and local controls (n=34, 15 male, 7 to 30 years). Z-scores for bone outcomes were calculated from reference data from a large sample of healthy children and young adults. Fasting blood and urine were collected, pubertal status determined by self-assessment and dietary intake and physical activity assessed by written questionnaires. Subjects with Thal were similar in age, but had lower height, weight and lean mass index Z-scores (all p < 0.001) compared to controls. DXA aBMD was significantly lower in Thal compared to controls at all sites. Adult Thal subjects (> 18 years, n = 11) had lower tibial trabecular vBMD (p = 0.03), cortical area, cortical BMC, cortical thickness, periosteal circumference and section modulus Z-scores (all p < 0.01) compared to controls. Cortical area, cortical BMC, cortical thickness, and periosteal circumference Z-scores (p = 0.02) were significantly lower in young Thal (≤ 18 years, n = 14) compared to controls. In separate multivariate models, tibial cortical area, BMC, and thickness and spine aBMD and whole body BMC Z-scores remained lower in Thal compared to controls after adjustment for gender, lean mass and/or growth deficits (all p < 0.01). Tanner stage was not predictive in these models. Osteocalcin, a marker of bone formation, was significantly reduced in Thal compared to controls after adjusting for age, puberty and whole body BMC (p=0.029). In summary, we have found evidence of skeletal deficits that cannot be dismissed as an artifact of small bone size or delayed maturity alone. Given that reduced bone density and strength are associated with increased risk of fracture, therapies focused on increasing bone formation and bone size in younger patients are worthy of further evaluation.     

High parity is associated with increased bone size and strength

Some, but not all, studies report an association between decreased hip fracture risk and high parity despite similar bone mineral density (BMD). Our hypothesis was that bone size, a major determinant of bone strength, is greater in women with high parity compared with low parity or nulliparous women. A cross-sectional study of 168 Hutterite women aged 40–80 years was conducted. BMD, bone mineral content (BMC) and bone area of the total body (TB), hip, femoral neck (FN), and lumbar spine (LS) were measured, as well as bone geometry at the 4% and 20% distal radius and bending strength at 20% radius. Diet and activity recall and strength measurements were obtained. Of the 168 women, 42 (25%) were nulliparous while the remaining women reported 1 to 16 births (median=6). Of the 126 parous women, 122 (97%) breast-fed their infants (range 1.5–24 months). Hip, FN and LS BMD were not associated with either parity or months of breast-feeding. TB BMC and bone area (both, p <0.05) and FN bone area ( p <0.01) were associated with parity. FN bone area was 4% greater in women with 7+ vs 1–4 children. Torsional bending strength, which includes structural and material bone properties, at the 20% distal radius was greater with higher parity ( p =0.01). No bone measure was associated with average months of breast-feeding. High parity is associated with increased radial torsional bending strength and femoral neck size. The greater femoral neck size, without higher BMD, may explain the reduced hip fracture risk among women with high parity previously reported in some studies.     

Low lumbar spine bone mineral density in both male and female endurance runners

There have been many reports of low bone mineral density (BMD) in female endurance runners. Although there have been several reports of low BMD in male runners, it is unclear how comparable the problem is to that in females. We compared BMD between male and female endurance runners and with a reference population. One hundred and nine endurance runners (65 females, 44 males) aged 19-50 years participated and had been training regularly for at least 3 years (32-187.2 km week(-1)) in events from 3 km to the marathon. BMD was measured at the lumbar spine (L2-L4) and hip by DXA. A questionnaire assessed training and menstrual status. Lumbar spine T scores were similar in male and female runners (-0.8 (0.8) versus -0.8 (0.7); f = 0.015; P = 0.904) as were total hip T scores (0.6 (7.9) versus 0.5 (9.2); f = 0.192; P = 0.662). The proportion of male runners with low lumbar spine BMD (<-1.0) (n = 16 from 44) compared to that of females (n = 27 from 65) (P = 0.675). Males had lower spine T scores than eumenorrhoeic females (-0.8 (0.7) versus -0.4 (0.7); f = 5.169; P = 0.03). There were moderate negative correlations between weekly running distance and lumbar spine BMD in males and females (r(2) = 0.267; 0.189; P < 0.001), independent of menstrual status in females (r(2) = 0.192; P < 0.001). Lumbar spine but not hip T scores were greater in runners who participated in resistance training at least twice-a-week (male: -0.4 versus -1.1; female: -0.5 versus -1.1; P < 0.01). Using multiple regression, running distance (-) and BMI (+) together best predicted lumbar spine T scores (r(2) = 0.402; P < 0.01) in females. Although weak, BMI (+) best predicted hip T scores (r(2) = 0.167; P < 0.05). In males, running distance and training years (-) together best predicted lumbar spine T scores (r(2) = 0.400; P < 0.01). Training years (-) best predicted hip T scores (r(2) = 0.361; P < 0.01). To conclude, our findings suggest that male runners face the same bone threat at the spine, as female runners. Further research in male athletes is required. Incorporation of regular resistance training into an athlete's training programme may be a useful preventative strategy.     

Growth in early life predicts bone strength in late adulthood: the Hertfordshire Cohort Study

Infant growth is a determinant of adult bone mass, and poor childhood growth is a risk factor for adult hip fracture. Peripheral quantitative computed tomography (pQCT) allows non-invasive assessment of bone strength. We utilised this technology to examine relationships between growth in early life and bone strength. We studied 313 men and 318 women born in Hertfordshire between 1931 and 1939 who were still resident there in adult life, for whom detailed early life records were available. Lifestyle factors were evaluated by questionnaire, anthropometric measurements made, and peripheral QCT examination of the radius and tibia performed (Stratec 4500). Birthweight and conditional weight at 1 year were strongly related to radial and tibial length in both sexes (p<0.001) and to measures of bone strength [fracture load X, fracture load Y, polar strength strain index (SSI)] at both the radius and tibia. These relationships were robust to adjustment for age, body mass index (BMI), social class, cigarette and alcohol consumption, physical activity, dietary calcium intake, HRT use, and menopausal status in women. Among men, BMI was strongly positively associated with radial (r=0.46, p=0.001) and tibial (r=0.24, p=0.006) trabecular bone mineral density (BMD). Current smoking was associated with lower cortical (radius: p=0.0002; tibia: p=0.08) and trabecular BMD (radius: p=0.08; tibia: p=0.04) in males. Similar trends of BMD with these anthropometric and lifestyle variables were seen in women but they were non-significant. Current HRT use was associated with greater female cortical (radius: p=0.0002; tibia: p=0.001) and trabecular (radius: p=0.008; tibia: p=0.04) BMD. Current HRT use was also associated with greater radial strength (polar SSI: p=0.006; fracture load X: p=0.005; fracture load Y: p=0.02) in women. Women who had sustained any fracture since the age of 45 years had lower radial total (p=0.0001), cortical (p<0.005) and trabecular (p=0.0002) BMD, poorer forearm bone strength [polar SSI (p=0.006), fracture load X and Y (p=0.02)], and lower tibial total (p<0.001), cortical (p=0.008), and trabecular (p=0.0001) BMD. We have shown that growth in early life is associated with bone size and strength in a UK population aged 65-73 years. Lifestyle factors were associated with volumetric bone density in this population.