A physical model for dual-energy X-ray absorptiometry--derived bone mineral density

A Case of Bilateral Transient Pregnancy-Related Osteoporosis of the Hip Diagnosed Late During the Lactation Period: A Rare Clinical Presentation and a Mini Review of the Literature

Transient pregnancy-related osteoporosis of the hip is a rare, idiopathic, benign, and usually self-limiting condition caused by edema of the bone marrow, which can be visualized on magnetic resonance imaging. Bilateral localization of the disease is even less common. Our case concerns a 31-year-old primigravida who, during the 35th week of pregnancy, was hospitalized at the Obstetrics and Gynecology Clinic of the General Hospital of Trikala with lumbar and hip pain. The pain gradually increased in intensity and was accompanied by severe movement limitation. No history of falls or injury was reported. Her personal history was unremarkable, and the course of the pregnancy was uneventful. A clinical examination by a team of orthopedic surgeons established a diagnosis of acute hip and back pain. Rest and administration of paracetamol did not improve her clinical condition. During the postpartum and lactation period, the lack of symptom relief led to the decision to further evaluate the patient. The diagnosis of pregnancy-related transient osteoporosis of both hips was established by magnetic resonance imaging. Immediate treatment with bisphosphonate medication after the discontinuation of breastfeeding led to a definitive remission of the symptoms three months later. In this study, after the case description, a brief literature review of this rare clinical entity is presented. Proper knowledge of this condition helps to provide the best possible short- and long-term prognostic outcomes for the mother, fetus, and newborn.

Quantifying Bone Strength Deficits in Young Adults Born Extremely Preterm or Extremely Low Birth Weight

The long-term bone health of young adults born extremely preterm (EP; <28 weeks' gestation) or extremely low birth weight (ELBW; <1000 g birth weight) in the post-surfactant era (since the early 1990s) is unclear. This study investigated their bone structure and estimated bone strength using peripheral quantitative computed tomography (pQCT)-based finite element modeling (pQCT-FEM). Results using this technique have been associated with bone fragility in several clinical settings. Participants comprised 161 EP/ELBW survivors (46.0% male) and 122 contemporaneous term-born (44.3% male), normal birth weight controls born in Victoria, Australia, during 1991-1992. At age 25 years, participants underwent pQCT at 4% and 66% of tibia and radius length, which was analyzed using pQCT-FEM. Groups were compared using linear regression and adjusted for height and weight. An interaction term between group and sex was added to assess group differences between sexes. Parameters measured included compressive stiffness (kcomp ), torsional stiffness (ktorsion ), and bending stiffness (kbend ). EP/ELBW survivors were shorter than the controls, but their weights were similar. Several unadjusted tibial pQCT-FEM parameters were lower in the EP/ELBW group. Height- and weight-adjusted ktorsion at 66% tibia remained lower in EP/ELBW (mean difference [95% confidence interval] -180 [-352, -8] Nm/deg). The evidence for group differences in ktorsion and kbend at 66% tibia was stronger among males than females (pinteractions  <0.05). There was little evidence for group differences in adjusted radial models. Lower height- and weight-adjusted pQCT-FEM measures in EP/ELBW compared with controls suggest a clinically relevant increase in predicted long-term fracture risk in EP/ELBW survivors, particularly males. Future pQCT-FEM studies should utilize the tibial pQCT images because of the greater variability in the radius possibly related to lower measurement precision. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Association Between Physical Fitness and Bone Strength and Structure in 3- to 5-Year-Old Children

BACKGROUND

The positive association between physical fitness and bone structure has been widely investigated in children and adolescents, yet no studies have evaluated this influence in young children (ie, preschoolers).

HYPOTHESIS

Fit children will present improved bone variables when compared with unfit children, and no sex-based differences will emerge in the sample.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Handgrip strength, standing long jump (SLJ), speed/agility, balance, and cardiorespiratory fitness (CRF) were assessed using the Assessing FITness levels in PREschoolers (PREFIT) test battery in 92 children (50 boys; age range, 3-5 years). A peripheral quantitative computed tomography scan was performed at 38% of the length of the nondominant tibia. Cluster analysis from handgrip strength, SLJ, speed/agility, and CRF was developed to identify fitness groups. Bone variables were compared between sexes and between cluster groups. The association between individual physical fitness components and different bone variables was also tested.

RESULTS

Three cluster groups emerged: fit (high values on all included physical fitness variables), strong (high strength values and low speed/agility and CRF), and unfit (low strength, speed/agility, and CRF). The fit group presented higher values than the strong and unfit groups for total and cortical bone mineral content, cortical area, and polar strength strain index (all P < 0.05). The fit group also presented a higher cortical thickness when compared with the unfit group (P < 0.05). Handgrip, SLJ, and speed/agility predicted all bone variables except for total and cortical volumetric bone mineral density. No differences were found for bone variables between sexes.

CONCLUSION

The results suggest that global fitness in preschoolers is a key determinant for bone structure and strength but not volumetric bone mineral density.

CLINICAL RELEVANCE

Physical fitness is a determinant for tibial bone mineral content, structure, and strength in very young children. Performing physical fitness tests could provide useful information related to bone health in preschoolers.

Regional changes in indices of bone strength of upper and lower limbs in response to high-intensity impact loading or high-intensity resistance training

It is well known that the bone response to physical activity is highly dependent on the nature of the loads imposed. Despite this, few direct comparisons of the effect of impact-style loading and resistance training on bone have been made. We therefore aimed to compare the effects of 10-month, twice-weekly, high-impact loading and 10-month, twice-weekly, high-intensity resistance training on indices of bone strength of both the upper and lower limbs of young adult women. Physically inactive, otherwise healthy, young adult women (18-30 years) with below average bone mass (T-score ≤ 0) were recruited as part of the OPTIMA-Ex trial. Testing included DXA- and pQCT-derived measures of bone mass and indices of bone strength and QUS-derived measures of bone quality of the dominant (D) and non-dominant (ND) upper (radius) and lower limbs (femoral neck, tibia, calcaneus). The present study examined those participants who completed the impact training (IT; n = 10) and resistance training (RT; n = 12) arms of the trial. Age differed between groups at baseline (IT = 23.2 ± 3.8 years, RT = 20.5 ± 1.8 years; p = 0.042). Compliance with the training programs did not differ (IT = 61.4 ± 15.1%, RT = 66.4 ± 11.2%, p = 0.381). Age and baseline differences in bone outcomes served as covariates for repeated measures and univariate ANCOVA conducted for dependent variables and percent change respectively. IT improved distal pQCT-derived bone mineral density (BMD) of the upper limb (ND radius: total BMD = 8.55 ± 2.26% versus 1.50 ± 2.04%, p = 0.040 and trabecular BMD = 1.86 ± 0.90% versus -1.30 ± 0.81%, p = 0.029) and lower limb (ND tibia trabecular BMD = 1.22 ± 0.55% versus -0.82 ± 0.50%, p = 0.017), more than RT. IT also improved upper limb bone strength index (BSI) (ND radius total BSI = 15.35 ± 2.83% versus 2.67 ± 2.55, p = 0.005) and lower limb BSI (D tibia total BSI = 5.16 ± 1.13% versus 0.37 ± 1.02%, p = 0.008; D tibia trabecular BSI = 3.93 ± 1.76% versus -2.84 ± 1.59, p = 0.014, ND tibia trabecular BSI = 3.57 ± 1.63% versus -3.15 ± 1.48%, p = 0.009) more than RT. Conversely, RT improved DXA-derived cortical volumetric BMD at the femoral neck more than IT (3.68 ± 1.99% versus -4.14 ± 2.20%, p = 0.021). Results suggest that IT and RT provide differing site-specific effects in both the upper and lower limbs, with superior bone responses observed at the distal segment from IT, while RT appeared to have greater effect on the shaft of the bone, on indices of bone-strength in young adult women.

Bone Mass and Strength and Fall-Related Fractures in Older Age

INTRODUCTION

Low bone mineral density is a risk factor for fractures. The aim of this follow-up study was to assess the association of various bone properties with fall-related fractures.

MATERIALS AND METHODS

187 healthy women aged 55 to 83 years at baseline who were either physically active or inactive were followed for 20 years. They were divided into two groups by whether or not they sustained fall-related fractures: fracture group (F) and nonfracture group (NF). At baseline, several bone properties were measured with DXA and pQCT, and their physical performance was also assessed.

RESULTS

During the follow-up, 120 women had no fall-related fractures, while 67 (38%) sustained at least one fall with fracture. NF group had about 4 to 11% greater BMD at the femoral neck and distal radius; the mean differences (95% CI) were 4.5 (0.3 to 8.6) % and 11.1 (6.3 to 16.1) %, respectively. NF group also had stronger bone structure at the tibia, the mean difference in BMC at the distal tibia was 6.0 (2.2 to 9.7) %, and at the tibial shaft 3.6 (0.4 to 6.8) %. However, there was no mean difference in physical performance.

CONCLUSIONS

Low bone properties contribute to the risk of fracture if a person falls. Therefore, in the prevention of fragility fractures, it is essential to focus on improving bone mass, density, and strength during the lifetime. Reduction of falls by improving physical performance, balance, mobility, and muscle power is equally important.

Aging-associated microstructural deterioration of vertebra in zebrafish

Zebrafish, a small teleost fish, is currently emerging as an animal model of local and systemic aging. In this study, we assessed age-related degenerative changes in the vertebral bone of zebrafish (3–12 month-post-fertilisation [mpf]) using micro-CT scanning. The bone volume (BV) of the trabecular bone in the male and female fish peaked at 6 mpf and reduced with age. In contrast to BV, bone mineral density and tissue volume did not change after 6 mpf, implying that the total mineral volume in the trabecular area remains unchanged, retaining the strength of vertebra. In addition, we performed micro-structural analysis of the trabecular thickness, trabecular number, and star volume of the tissue space and trabeculae, and found that the size of the trabecular bone reduced with age. Furthermore, aged zebrafish (45 mpf) exhibited ectopic ossification inside or outside of their vertebrae.

In summary, we analysed bone structural parameters in adult zebrafish vertebra, which are also used in humans, and demonstrated that aged zebrafish have deteriorated microarchitecture (trabecular thickness and number, tissue space star volume and trabecular star volume) with reduction of trabecular bones, similar to that observed during aging in humans. Zebrafish can be utilised as an animal model to understand the pathology of human bone aging, and the discovery of new therapeutic agents against age-related osteoporosis.

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We analysed bone structural parameters in adult zebrafish vertebrae.

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Microstructural changes in aged-zebrafish are similar to those in humans.

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Aged zebrafish exhibited ectopic ossification inside or outside of their vertebrae.

Circulating Levels of Inflammation and the Effect on Exercise-Related Changes in Bone Mass, Structure and Strength in Middle-Aged and Older Men

Chronic, low-grade systematic inflammation has been associated with bone loss and increased fracture risk. We previously reported that exercise improved femoral neck bone mineral density (BMD), geometry and strength and lumbar spine trabecular BMD in middle-aged and older men, but had no effect on markers of inflammation. The aim of this study was to examine the association between basal inflammatory status and the adaptive skeletal responses to exercise. Secondary analysis was completed on 91 men aged 50-79 years who participated in an 18-month program of progressive resistance training plus weight-bearing impact exercise (3 day/week) with and without additional calcium-vitamin D₃. Markers of inflammation (serum hs-CRP, TNF-α and IL-6) and DXA and QCT-derived BMD, bone structure and strength at the lumbar spine and proximal femur were measured at baseline and 18 months. Multiple regression was used to assess associations between skeletal changes and both baseline levels of individual inflammatory markers and a composite inflammatory index derived from the number of markers categorized into the highest tertile. Baseline serum hs-CRP, TNFα and IL-6 and the composite inflammatory index score were not associated with skeletal changes at any site after adjusting for age, change in lean mass, disease(s)/medication use and adherence to the exercise intervention. In conclusion, this study indicates that basal inflammatory status does not influence the osteogenic response to exercise training in healthy middle-aged and older men.

Peripheral Quantitative Computed Tomography: Review of Evidence and Recommendations for Image Acquisition, Analysis, and Reporting, Among Individuals With Neurological Impairment

In 2015, the International Society for Clinical Densitometry (ISCD) position statement regarding peripheral quantitative computed tomography (pQCT) did not recommend routine use of pQCT, in clinical settings until consistency in image acquisition and analysis protocols are reached, normative studies conducted, and treatment thresholds identified. To date, the lack of consensus-derived recommendations regarding pQCT implementation remains a barrier to implementation of pQCT technology. Thus, based on description of available evidence and literature synthesis, this review recommends the most appropriate pQCT acquisition and analysis protocols for clinical care and research purposes, and recommends specific measures for diagnosis of osteoporosis, assigning fracture risk, and monitoring osteoporosis treatment effectiveness, among patients with neurological impairment. A systematic literature search of MEDLINE, EMBASE^©, CINAHL, and PubMed for available pQCT studies assessing bone health was carried out from inception to August 8th, 2017. The search was limited to individuals with neurological impairment (spinal cord injury, stroke, and multiple sclerosis) as these groups have rapid and severe regional declines in bone mass. Of 923 references, we identified 69 that met review inclusion criteria. The majority of studies (n = 60) used the Stratec XCT 2000/3000 pQCT scanners as reflected in our evaluation of acquisition and analysis protocols. Overall congruence with the ISCD Official Positions was poor. Only 11% (n = 6) studies met quality reporting criteria for image acquisition and 32% (n = 19) reported their data analysis in a format suitable for reproduction. Therefore, based on current literature synthesis, ISCD position statement standards and the authors' expertise, we propose acquisition and analysis protocols at the radius, tibia, and femur sites using Stratec XCT 2000/3000 pQCT scanners among patients with neurological impairment for clinical and research purposes in order to drive practice change, develop normative datasets and complete future meta-analysis to inform fracture risk and treatment efficacy evaluation.

Bone geometry in young male and female football players: a peripheral quantitative computed tomography (pQCT) study

The present study shows that football practice during growth may improve bone geometry in male and female football players. However, only females had better bone strength in comparison with controls.

PURPOSE

The aim of this study was to compare bone geometry in adolescent football players and controls.

METHODS

A total of 107 football players (71 males/36 females; mean age 12.7 ± 0.6/12.7 ± 0.6 years) and 42 controls (20 males/22 females; mean age 13.1 ± 1.4/12.7 ± 1.3 years) participated in this study. Total and trabecular volumetric bone mineral content (Tt.BMC/Tb.BMC), cross-sectional area (Tt.Ar/Tb.Ar), and bone strength index (BSI) were measured at 4% site of the non-dominant tibia by peripheral quantitative computed tomography (pQCT). Moreover, Tt.BMC, cortical BMC (Ct.BMC), Tt.Ar, cortical Ar (Ct.Ar), cortical thickness (Ct.Th), periosteal circumference (PC), endosteal circumference (EC), fracture load in X-axis, and polar strength strain index (SSIp) were measured at 38% site of the tibia. Multivariate analyses of covariance were used to compare bone pQCT variables between football players and controls using the tibia length and maturity offset as covariates.

RESULTS

Female football players demonstrated 13.8-16.4% higher BSI, Ct.Th, fracture load in X-axis, and SSIp than controls (p < .0036). Males showed no significant differences in bone strength when compared to controls (p > .0036). In relation to bone mineral content and area, male football players showed 8.8% higher Tt.Ar and Tb.Ar at the 4% site of the tibia when compared to controls; whereas 13.8-15.8% higher Tt.BMC, Ct.BMC, and Ct.Ar at the 38% site of the tibia were found in female football players than controls (p < .0036).

CONCLUSIONS

In this study, female adolescent football players presented better bone geometry and strength values than controls. In contrast, only bone geometry was higher in male football players than controls.

Low free 25-hydroxyvitamin D and high vitamin D binding protein and parathyroid hormone in obese Caucasians. A complex association with bone?

Background

Studies have shown altered vitamin D metabolism in obesity. We assessed differences between obese and normal-weight subjects in total, free, and bioavailable 25-hydroxyvitamin D (25(OH)D, 25(OH)D_Free, and 25(OH)D_Bio, respectively), vitamin D binding protein (DBP), parathyroid hormone (PTH) and bone traits.

Methods

595 37-47-year-old healthy Finnish men and women stratified by BMI were examined in this cross-sectional study. Background characteristic and intakes of vitamin D and calcium were collected. The concentrations of 25(OH)D, PTH, DBP, albumin and bone turnover markers were determined from blood. 25(OH)D_Free and 25(OH)D_Bio were calculated. pQCT was performed at radius and tibia.

Results

Mean±SE (ANCOVA) 25(OH)D_Free (10.8±0.6 vs 12.9±0.4 nmol/L; P = 0.008) and 25(OH)D_Bio (4.1±0.3 vs 5.1±0.1 nmol/L; P = 0.003) were lower in obese than in normal-weight women. In men, 25(OH)D (48.0±2.4 vs 56.4±2.0 nmol/L, P = 0.003), 25(OH)D_Free (10.3±0.7 vs 12.5±0.6 pmol/L; P = 0.044) and 25(OH)D_Bio (4.2±0.3 vs 5.1±0.2 nmol/L; P = 0.032) were lower in obese. Similarly in all subjects, 25(OH)D, 25(OH)D_Free and 25(OH)D_Bio were lower in obese (P<0.001). DBP (399±12 vs 356±7mg/L, P = 0.008) and PTH (62.2±3.0 vs 53.3±1.9 ng/L; P = 0.045) were higher in obese than in normal-weight women. In all subjects, PTH and DBP were higher in obese (P = 0.047and P = 0.004, respectively). In obese women, 25(OH)D was negatively associated with distal radius trabecular density (R² = 0.089, P = 0.009) and tibial shaft cortical strength index (CSI) (R² = 0.146, P = 0.004). 25(OH)D_Free was negatively associated with distal radius CSI (R² = 0.070, P = 0.049), radial shaft cortical density (CorD) (R² = 0.050, P = 0.045), and tibial shaft CSI (R² = 0.113, P = 0.012). 25(OH)D_Bio was negatively associated with distal radius CSI (R² = 0.072, P = 0.045), radial shaft CorD (R² = 0.059, P = 0.032), and tibial shaft CSI (R² = 0.093, P = 0.024).

Conclusions

The associations between BMI and 25(OH)D, 25(OH)D_Free, and 25(OH)D_Bio, DBP, and PTH suggest that obese subjects may differ from normal-weight subjects in vitamin D metabolism. BMI associated positively with trabecular bone traits and CSI in our study, and slightly negatively with cortical bone traits. Surprisingly, there was a negative association of free and bioavailable 25(OH)D and some of the bone traits in obese women.

Bone loss patterns in cortical, subcortical, and trabecular compartments during simulated microgravity

Disuse studies provide a useful model for bone adaptation. A direct comparison of these studies is, however, complicated by the different settings used for bone analysis. Through pooling and reanalysis of bone data from previous disuse studies, we determined bone loss and recovery in cortical, subcortical, and trabecular compartments and evaluated whether the study design modulated skeletal adaptation. Peripheral quantitative tomographic (pQCT) images from control groups of four disuse studies with a duration of 24, 35, 56, and 90 days were reanalyzed using a robust threshold-free segmentation algorithm. The pQCT data were available from 27 young healthy men at baseline, and at specified intervals over disuse and reambulation phases. The mean maximum absolute bone loss (mean ± 95% CI) was 6.1 ± 4.5 mg/mm in cortical, 2.4 ± 1.6 mg/mm in subcortical, and 9.8 ± 9.1 mg/mm in trabecular compartments, after 90 days of bed rest. The percentage changes in all bone compartments were, however, similar. During the first few weeks after onset of reambulation, the bone loss rate was systematically greater in the cortical than in the trabecular compartment (P < 0.002), and this was observed in all studies except for the longest study. We conclude that disuse-induced bone losses follow similar patterns irrespective of study design, and the largest mean absolute bone loss occurs in the cortical compartment, but apparently only during the first 60 days. With longer study duration, trabecular loss may become more prominent.

Does bone resorption stimulate periosteal expansion? A cross-sectional analysis of β-C-telopeptides of type I collagen (CTX), genetic markers of the RANKL pathway, and periosteal circumference as measured by pQCT

We hypothesized that bone resorption acts to increase bone strength through stimulation of periosteal expansion. Hence, we examined whether bone resorption, as reflected by serum β-C-telopeptides of type I collagen (CTX), is positively associated with periosteal circumference (PC), in contrast to inverse associations with parameters related to bone remodeling such as cortical bone mineral density (BMDC ). CTX and mid-tibial peripheral quantitative computed tomography (pQCT) scans were available in 1130 adolescents (mean age 15.5 years) from the Avon Longitudinal Study of Parents and Children (ALSPAC). Analyses were adjusted for age, gender, time of sampling, tanner stage, lean mass, fat mass, and height. CTX was positively related to PC (β=0.19 [0.13, 0.24]) (coefficient=SD change per SD increase in CTX, 95% confidence interval)] but inversely associated with BMDC (β=-0.46 [-0.52,-0.40]) and cortical thickness [β=-0.11 (-0.18, -0.03)]. CTX was positively related to bone strength as reflected by the strength-strain index (SSI) (β=0.09 [0.03, 0.14]). To examine the causal nature of this relationship, we then analyzed whether single-nucleotide polymorphisms (SNPs) within key osteoclast regulatory genes, known to reduce areal/cortical BMD, conversely increase PC. Fifteen such genetic variants within or proximal to genes encoding receptor activator of NF-κB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) were identified by literature search. Six of the 15 alleles that were inversely related to BMD were positively related to CTX (p<0.05 cut-off) (n=2379). Subsequently, we performed a meta-analysis of associations between these SNPs and PC in ALSPAC (n=3382), Gothenburg Osteoporosis and Obesity Determinants (GOOD) (n=938), and the Young Finns Study (YFS) (n=1558). Five of the 15 alleles that were inversely related to BMD were positively related to PC (p<0.05 cut-off). We conclude that despite having lower BMD, individuals with a genetic predisposition to higher bone resorption have greater bone size, suggesting that higher bone resorption is permissive for greater periosteal expansion.

Calcium intake in health maintenance - a systematic review

Background

Calcium (Ca) is an essential nutrient for the human body. Despite lively research, there is uncertainty about Ca requirements in terms of desirable health outcomes including an upper intake level above which the potential for harm increases.

Objectives

The aim was to conduct a review to update requirements and desirable or harmful health effects of Ca on the current scientific evidence.

Methods

We searched Medline and Swemed from January 2000 to December 2011 and included all systematic reviews that reported Ca supplementation or usual Ca intake on health outcomes. Meta-analyses, randomized clinical trials and cohort studies were included in the second search between May 2009 and March 2011 and an additional search covering studies till the end of 2011. This review concentrated on studies reporting independent effects of Ca, although a few recent trials report sole effects of Ca on health outcomes, most trials use Ca in combination with vitamin D vs. placebo.

Results

In total, we reviewed 38 studies addressing the effects of Ca on bone, pregnancy-related outcomes, cancers, cardiovascular outcomes, obesity, and mortality. There was a lot of heterogeneity in the study protocols, which made it difficult to draw any strong conclusions. According to the literature, high Ca intake seems to have a small positive effect on bone mineral content (BMC) or bone mineral density (BMD) in children and postmenopausal women. We did not find any consistent evidence on the effects of Ca on bone health in premenopausal women or men. Also, the evidence that Ca supplementation reduces fracture incidence is scarce and inconsistent. Maternal diet may influence the peak bone mass of offspring but more studies are required. There was no overall effect of Ca intake on cancers. Ca was associated with a decreased risk of breast cancer and a slightly increased risk of prostate cancer in two of the three studies. No associations were found with other cancers. We found no consistent association between cardiovascular outcomes and Ca intake except for blood pressure. A small decrease of 2–4 mmHg in systolic blood pressure was found in pregnant and in hypertensive subjects with Ca supplementation. Reviewed studies did not show consistent evidence relating Ca intake to either mortality or obesity.

Conclusion

Based on this evidence, there is no need to change the Nordic recommendations for Ca intake. However, due to heterogeneity in the studies it is difficult to interpret the results and provide single summary statement.

Sport-specific association between exercise loading and the density, geometry, and microstructure of weight-bearing bone in young adult men

In this population-based study of 24-year-old men, we have investigated the association between sport-specific exercise loading and different bone parameters. We reveal that the association between exercise loading and bone parameters is sport-specific, indicating that nonspecific resistance exercise does not impact bone density, geometry, or microstructure in young men.

INTRODUCTION

In this cross-sectional study, the association between nonspecific resistive exercise and areal and volumetric bone density, bone geometry, or bone microstructure was investigated in young adult men.

METHODS

A total of 184 male athletes, 24.0 ± 0.6 years of age (mean ± SD), representing nonspecific resistive exercise and soccer (proportion of recreational athletes, 93.4 and 7.7 %, respectively), and 177 nonathletic age-matched controls were measured with dual-energy X-ray absorptiometry. Radius and tibia were measured by peripheral quantitative computed tomography (pQCT) at the diaphysis and by three-dimensional pQCT at the metaphysis.

RESULTS

Men in the nonspecific resistive exercise group had higher grip strength(9.1 % or 0.4 SD) and higher lean mass(5.6 % or 0.5 SD) than those in the nonathletic group(p < 0.01 and p < 0.001, respectively). However, men who participated in nonspecific resistive exercise did not have higher bone density or a more favorable bone microstructure or geometry than their nonathletic referents. In contrast, men playing soccer had higher areal bone mineral density (aBMD) at the femoral neck (19.5 % or 1.2 SD) and lumbar spine (12.6 % or 1.0 SD), as well as larger cortical cross-sectional area (16.4 % or 1.1 SD) and higher trabecular bone volume fraction (14.5 % or 0.9 SD), as a result of increased trabecular number (8.7 % or 0.6 SD) and thickness (5.7 % or 0.4 SD) at the tibia than men in the nonathletic group(p < 0.001).

CONCLUSIONS

Weight-bearing exercise with impacts from varying directions (playing soccer) is associated with aBMD and volumetric BMD, cortical bone geometry, as well as trabecular microstructure of weight-bearing bone. Nonspecific recreational resistance exercise does not appear to be a strong determinant of bone density, geometry, or microstructure in young adult men.

Genetic determinants of trabecular and cortical volumetric bone mineral densities and bone microstructure

Most previous genetic epidemiology studies within the field of osteoporosis have focused on the genetics of the complex trait areal bone mineral density (aBMD), not being able to differentiate genetic determinants of cortical volumetric BMD (vBMD), trabecular vBMD, and bone microstructural traits. The objective of this study was to separately identify genetic determinants of these bone traits as analysed by peripheral quantitative computed tomography (pQCT). Separate GWA meta-analyses for cortical and trabecular vBMDs were performed. The cortical vBMD GWA meta-analysis (n = 5,878) followed by replication (n = 1,052) identified genetic variants in four separate loci reaching genome-wide significance (RANKL, rs1021188, p = 3.6×10⁻¹⁴; LOC285735, rs271170, p = 2.7×10⁻¹²; OPG, rs7839059, p = 1.2×10⁻¹⁰; and ESR1/C6orf97, rs6909279, p = 1.1×10⁻⁹). The trabecular vBMD GWA meta-analysis (n = 2,500) followed by replication (n = 1,022) identified one locus reaching genome-wide significance (FMN2/GREM2, rs9287237, p = 1.9×10⁻⁹). High-resolution pQCT analyses, giving information about bone microstructure, were available in a subset of the GOOD cohort (n = 729). rs1021188 was significantly associated with cortical porosity while rs9287237 was significantly associated with trabecular bone fraction. The genetic variant in the FMN2/GREM2 locus was associated with fracture risk in the MrOS Sweden cohort (HR per extra T allele 0.75, 95% confidence interval 0.60–0.93) and GREM2 expression in human osteoblasts. In conclusion, five genetic loci associated with trabecular or cortical vBMD were identified. Two of these (FMN2/GREM2 and LOC285735) are novel bone-related loci, while the other three have previously been reported to be associated with aBMD. The genetic variants associated with cortical and trabecular bone parameters differed, underscoring the complexity of the genetics of bone parameters. We propose that a genetic variant in the RANKL locus influences cortical vBMD, at least partly, via effects on cortical porosity, and that a genetic variant in the FMN2/GREM2 locus influences GREM2 expression in osteoblasts and thereby trabecular number and thickness as well as fracture risk.

Osteoporosis is a common highly heritable skeletal disease characterized by reduced bone mineral density (BMD) and deteriorated bone microstructure, resulting in an increased risk of fracture. Most previous genetic epidemiology studies have focused on the genetics of the complex trait BMD, not being able to separate genetic determinants of the trabecular and cortical bone compartments and bone microstructure. The trabecular and cortical BMDs can be analysed separately by computed tomography. Therefore, we performed separate genome-wide association studies for trabecular and cortical BMDs, demonstrating that the genetic determinants of cortical and trabecular BMDs differ. Genetic variants in the RANKL, LOC285735, OPG, and ESR1 loci were associated with cortical BMD, while a genetic variant in the FMN2/GREM2 locus was associated with trabecular BMD. Two of these are novel bone-related loci. Follow-up analyses of bone microstructure demonstrated that a genetic variant in the RANKL locus is associated with cortical porosity and that the FMN2/GREM2 locus is associated with trabecular number and thickness. We propose that a genetic variant in the RANKL locus influences cortical BMD via effects on cortical porosity, and that a genetic variant in the FMN2/GREM2 locus influences trabecular BMD and fracture risk via effects on both trabecular number and thickness.

Femoral neck cross-sectional geometry and exercise loading

The aim of this study was to examine the association between different types of exercise loading and femoral neck cross-sectional geometry. Our data comprised proximal femur magnetic resonance (MR) images obtained from 91 female athletes and their 20 age-matched controls. The athletes were categorized according to typical training activity - high impact (high and triple jumping), odd impact (racket and soccer playing), high magnitude (power lifting), repetitive low impact (endurance running) and repetitive non-impact (swimming). Segmented MR images at two locations, narrowest cross-section of the femoral neck (narrowFN) and the cross-section at insertion of articular capsule (distalFN), were investigated to detect between group differences in shape, curvature and buckling ratio derived using image and signal analysis tools. The narrowFN results indicated that the high-impact group had weaker antero-superior (33% larger buckling ratio than controls) but stronger inferior weight-bearing region (32% smaller than controls), while the odd-impact group had stronger superior, posterior and anterior region (21% smaller buckling ratio than controls). The distalFN results indicated that the high-impact group had stronger inferior region (37% smaller buckling ratio), but the odd-impact group had stronger superior region (22% smaller buckling ratio) than the controls. Overall, the results point towards odd-impact exercise loading, with inherently varying directions of impact, associated with more robust cross-sectional geometry along the femoral neck. In conclusion, our one-dimensional polar treatment for geometrical traits and intuitive presentation of differences in trends between exercise groups and controls provides a basis for analysis with high angular accuracy.

Increased physical activity is associated with enhanced development of peak bone mass in men: a five-year longitudinal study

Data supporting physical activity guidelines to optimize bone development in men is sparse. Peak bone mass is believed to be important for the risk of osteoporosis later in life. The objective of this study was to determine if an increased amount of physical activity over a 5-year period was associated with increased bone mineral content (BMC), areal (aBMD) and volumetric (vBMD) bone mineral density, and a favorable development of cortical bone size in young adult men. The original 1068 young men, initially enrolled in the Gothenburg Osteoporosis and Obesity Determinants (GOOD) study, were invited to participate in the longitudinal study, and a total of 833 men (78%), 24.1 ± 0.6 years of age, were included in the 5-year follow-up. A standardized self-administered questionnaire was used to collect information about patterns of physical activity at both the baseline and 5-year follow-up visits. BMC and aBMD were measured using dual energy X-ray absorptiometry, whereas vBMD and bone geometry were measured by peripheral quantitative computed tomography. Increased physical activity between the baseline and follow-up visits was associated with a favorable development in BMC of the total body, and aBMD of the lumbar spine and total hip (p < 0.001), as well as with development of a larger cortex (cortical cross sectional area), and a denser trabecular bone of the tibia (p < 0.001). In conclusion, increased physical activity was related to an advantageous development of aBMD, trabecular vBMD and cortical bone size, indicating that exercise is important in optimizing peak bone mass in young men.

Effects of high-impact training and detraining on femoral neck structure in premenopausal women: a hip structural analysis of an 18-month randomized controlled exercise intervention with 3.5-year follow-up

PURPOSE

This study evaluated the training effects of an 18-month exercise intervention and subsequent 3.5-year follow-up on femoral neck structure in premenopausal women.

METHODS

Of 98 women who participated in this randomized controlled study, 84 (39 trainees and 45 controls) completed the 18-month intervention. At both 18 months and 3.5 years, dual-energy X-ray absorptiometry data on 22 trainees and 22 control participants (ages 35-45 y) were available for hip structural analysis. The section modulus (Z), cross-sectional area (CSA), and subperiosteal width at the femoral neck were analyzed. Lower-leg explosive power and estimated maximal oxygen uptake (Vo(2)max) were assessed by vertical countermovement jump and standardized 2 km walking test, respectively. Progressive supervised high-impact exercises were done three times per week for 18 months.

RESULTS

Significant between-group differences in favour of trainees were observed after the 18-month intervention in Z (3.2%, p=0.047) and CSA (2.8%, p=0.043). At the 3.5-year follow-up point, the exercise-induced benefits in Z and CSA had diminished and were statistically insignificant. A between-group difference in favour of trainees was observed in lower-limb power after intervention (4.2%, p=0.002) and at 3.5-year follow-up (5.1%, p=0.003). A similar difference was seen in estimated Vo(2)max (5.6% after intervention, p=0.002, and 4.6% at 3.5-y follow-up, p=0.005).

CONCLUSION

The 18-month high-impact exercise intervention strengthened the femoral neck in premenopausal women by enhancing its structural properties; however, this benefit was not maintained at 3.5-year follow-up. In contrast, the exercise benefits on physical performance continued to be maintained 3.5 years after intervention.

Divergent Significance of Bone Mineral Density Changes in Aging Depending on Sites and Sex Revealed through Separate Analyses of Bone Mineral Content and Area

Bone mineral density (aBMD) is equivalent to bone mineral content (BMC) divided by area. We rechecked the significance of aBMD changes in aging by examining BMC and area separately. Subjects were 1167 community-dwelling Japanese men and women, aged 40-79 years. ABMDs of femoral neck and lumbar spine were assessed by DXA twice, at 6-year intervals. The change rates of BMC and area, as well as aBMD, were calculated and described separately by the age stratum and by sex. In the femoral neck region, aBMDs were significantly decreased in all age strata by an increase in area as well as BMC loss in the same pattern in both sexes. In the lumbar spine region, aBMDs decreased until the age of 60 in women, caused by the significant BMC decrease accompanying the small area change. Very differently in men, aBMDs increased after their 50s due to BMC increase, accompanied by an area increase. Separate analyses of BMC and area change revealed that the significance of aBMD changes in aging was very divergent among sites and between sexes. This may explain in part the dissociation of aBMD change and bone strength, suggesting that we should be more cautious when interpreting the meaning of aBMD change.

Bone mineral density discordance and exploration of one of its causes

Discordances between hip and spine areal density T-score values are common and incompletely understood. In a cohort of 1157 postmenopausal women, discordances of greater than 10% occurred in 91%, with spine bone mineral density (BMD) T-scores significantly less negative than femoral neck (FN) T-scores (p<0.001). However, when T-scores based on bone mineral content (BMC) rather than BMD were used, the mean discordance was not significantly different from 0. This was largely because BMC at the FN had seemingly declined with age less rapidly than had BMD at that site. This can be explained by age-related areal expansion at the hip, which would be missed in the reported BMD output. One consequence is that if BMC-based T-scores are used to classify patients, substantially fewer individuals would have been judged osteoporotic in this cohort (two-thirds fewer for spine and three-fourths fewer for hip).

Do both areal BMD and injurious falls explain the higher incidence of fractures in women than in men?

The higher incidence of fractures in women than in men is generally attributed to the lower areal bone mineral density (areal BMD, g/cm(2)) of the former. The purpose of the present study was to investigate both areal BMD and injurious falls as risk factors for fractures. In a first cohort, areal BMD was measured in 5,131 men and women (age range 40-95 years). In a second cohort, consisting of 26,565 men and women (age range 40-69 years), a health survey was conducted including questions about lifestyle and medication. Main outcome measures included validated prospective injurious falls and fractures in both cohorts. The higher areal BMD and femoral neck BMD in men compared to women (P < 0.001) were explained by a higher diameter of the femoral neck. Importantly, the diameter of the femoral neck was not associated with fractures in either sex (hazard ratio [HR] 0.94-1.04, P > 0.05 for all), suggesting that a higher areal BMD and lower incidence of osteoporosis in men do not explain their lower incidence of fractures. In contrast, women were more prone to sustain injurious falls than men in both cohorts investigated (HR for women = 1.61 and 1.84, P < 0.001 for both), resulting in a higher incidence of fractures (HR for women = 2.24 and 2.36, P < 0.001 for both). The number of injurious falls and fractures occurring each month during the study period showed a very strong correlation in both women (r = 0.95, P < 0.00001) and men (r = 0.97, P < 0.00001). In summary, low areal BMD, and thus osteoporosis, may not explain the higher fracture incidence in women than in men. Instead, a higher incidence of injurious falls in women was strongly associated with the higher fracture risk.

Independent and combined effects of calcium-vitamin D3 and exercise on bone structure and strength in older men: an 18-month factorial design randomized controlled trial

CONTEXT

Exercise and calcium-vitamin D are independently recognized as important strategies to prevent osteoporosis, but their combined effects on bone strength and its determinants remain uncertain.

OBJECTIVE

To assess whether calcium-vitamin D(3) fortified milk could enhance the effects of exercise on bone strength, structure, and mineral density in middle-aged and older men.

DESIGN, SETTING, PARTICIPANTS

An 18-month factorial design randomized controlled trial in which 180 men aged 50-79 years were randomized to the following: exercise + fortified milk; exercise; fortified milk; or controls. Exercise consisted of progressive resistance training with weight-bearing impact activities performed 3 d/week. Men assigned to fortified milk consumed 400 ml/d of 1% fat milk containing 1000 mg/d calcium and 800 IU/d vitamin D(3).

MAIN OUTCOME MEASURES

Changes in bone mineral density (BMD), bone structure, and strength at the lumbar spine (LS), proximal femur, mid-femur, and mid-tibia measured by dual energy x-ray absorptiometry and/or quantitative computed tomography.

RESULTS

There were no exercise-by-fortified milk interactions at any skeletal site. Main effect analysis showed that exercise led to a 2.1% (95% confidence interval, 0.5-3.6) net gain in femoral neck section modulus, which was associated with an approximately 1.9% gain in areal BMD and cross-sectional area. Exercise also improved LS trabecular BMD [net gain 2.2% (95% confidence interval, 0.2-4.1)], but had no effect on mid-femur or mid-tibia BMD, structure, or strength. There were no main effects of the fortified milk at any skeletal site.

CONCLUSION

A community-based multi-component exercise program successfully improved LS and femoral neck BMD and strength in healthy older men, but providing additional calcium-vitamin D(3) to these replete men did not enhance the osteogenic response.

Anatomical sector analysis of load-bearing tibial bone structure during 90-day bed rest and 1-year recovery

The aim of this study was to investigate whether the bone response to long bed rest-related immobility and during subsequent recovery differed at anatomically different sectors of tibial epiphysis and diaphysis. For this study, peripheral quantitative tomographic (pQCT) scans obtained from a previous 90-day 'Long Term Bed Rest' intervention were preprocessed with a new method based on statistical approach and re-analysed sector-wise. The pQCT was performed on 25 young healthy males twice before the bed rest, after the bed rest and after 1-year follow-up. All men underwent a strict bed rest intervention, and in addition, seven of them received pamidronate treatment and nine did flywheel exercises as countermeasures against disuse-related bone loss. Clearly, 3-9% sector-specific losses in trabecular density were observed at the tibial epiphysis on average. Similarly, cortical density decreased in a sector-specific way being the largest at the anterior sector of tibial diaphysis. During recovery, the bed rest-induced bone losses were practically restored and no consistent sector-specific modulation was observed in any subgroup. It is concluded that the sector-specific analysis of bone cross-sections has potential to reveal skeletal responses to various interventions that cannot be inferred from the average analysis of the whole bone cross-section. This approach is considered also useful for evaluating the bone responses from the biomechanical point of view.

Lactase gene c/t(-13910) polymorphism, calcium intake, and pQCT bone traits in Finnish adults

Genetic lactase nonpersistence may influence calcium intake and thereby bone health. We investigated in the Cardiovascular Risk in Young Finn Study whether young adults aged 31-46 years with the C/C(-13910) genotype are more susceptible to reduced bone phenotypes, low-energy fractures, and low calcium intake than subjects with other lactase genotypes. We also analyzed the gene-environment interactions on bone with calcium intake and physical activity. Peripheral quantitative computed tomography bone traits were measured from the distal and shaft sites of the radius and tibia. The total number of those subjects whose nondominant forearm was measured and the lactase genotype was defined was 1551. Information on diet, lifestyle factors, and fractures was collected with questionnaires. The mean intake of calcium was the lowest in men with the C/C(-13910) genotype (P = 0.001). Men with the T/T(-13910) genotype had ~3% higher trabecular density at the distal radius and distal tibia compared to other lactase genotypes (P = 0.03 and 0.02, respectively). In women, we found no evidence of the gene effect at the radius and tibia. No major interactions of the C/T(-13910) polymorphism with calcium intake or physical activity on bone phenotypes were found in either sex. In conclusion, the C/T(-13910) polymorphism was associated with trabecular density at the distal radius and tibia in men. These differences may be due to the differences in calcium intake between the lactase genotypes.

Densitometric and geometric measurement of the proximal femur in elderly women with and without osteoporotic vertebral fractures by volumetric quantitative multi-slice CT

There is a lack of research on volumetric multi-slice CT (MSCT) application in hip densitometric assessment and geometric measures in elderly women with osteoporotic vertebral fractures. A total of 237 elderly women were divided into three groups based on BMD values of the lumbar spine (AP-SPINE) and/or the femoral neck (NECK) by dual energy X-ray absorptiometry (DXA): osteoporosis with (OP_FX, 53 cases) or without vertebral fracture (OP_NONFX, 94 cases), or normal BMD (CONTROL, 90 cases). Volumetric BMD of trabecular bone (TRAB), integral bone (INTGL) and cortical bone (CORT) with neck axis length (NAL) and minimum cross-section area (mCSA) measures of the left femoral neck were calculated, respectively, by using OsteoCAD software based on MSCT scans of the abdominal-pelvic region of all participants, then the index of femoral neck strength (FNSI) was estimated. The values of TRAB, CORT and INTGL of OP_FX were significantly lower than those of OP_NONFX, with the decrease in 6.8-21.8%, as well as being lower than those in CONTROL, whereas no significant differences in the values of AP-SPINE and NECK were found between OP_FX and OP_NONFX. No significant difference of the value of mCSA was found among these three groups. The NAL value of OP_NONFX was larger than that of CONTROL. FNSI of femoral neck in OP_FX (0.42 ± 0.15 g(2)/cm(4)) was significantly lower than OP_NONFX (0.50 ± 0.14 g(2)/cm(4)) (p < 0.05). vQCT measurement seemed to be more effective than DXA in evaluating hip densitometric changes and discriminating osteoporotic elderly subjects with fractured vertebrae from the non-fractured in a group of Chinese women.

Targeted exercise against osteoporosis: A systematic review and meta-analysis for optimising bone strength throughout life

BACKGROUND

Exercise is widely recommended to reduce osteoporosis, falls and related fragility fractures, but its effect on whole bone strength has remained inconclusive. The primary purpose of this systematic review and meta-analysis was to evaluate the effects of long-term supervised exercise (> or =6 months) on estimates of lower-extremity bone strength from childhood to older age.

METHODS

We searched four databases (PubMed, Sport Discus, Physical Education Index, and Embase) up to October 2009 and included 10 randomised controlled trials (RCTs) that assessed the effects of exercise training on whole bone strength. We analysed the results by age groups (childhood, adolescence, and young and older adulthood) and compared the changes to habitually active or sedentary controls. To calculate standardized mean differences (SMD; effect size), we used the follow-up values of bone strength measures adjusted for baseline bone values. An inverse variance-weighted random-effects model was used to pool the results across studies.

RESULTS

Our quality analysis revealed that exercise regimens were heterogeneous; some trials were short in duration and small in sample size, and the weekly training doses varied considerably between trials. We found a small and significant exercise effect among pre- and early pubertal boys [SMD, effect size, 0.17 (95% CI, 0.02-0.32)], but not among pubertal girls [-0.01 (-0.18 to 0.17)], adolescent boys [0.10 (-0.75 to 0.95)], adolescent girls [0.21 (-0.53 to 0.97)], premenopausal women [0.00 (-0.43 to 0.44)] or postmenopausal women [0.00 (-0.15 to 0.15)]. Evidence based on per-protocol analyses of individual trials in children and adolescents indicated that programmes incorporating regular weight-bearing exercise can result in 1% to 8% improvements in bone strength at the loaded skeletal sites. In premenopausal women with high exercise compliance, improvements ranging from 0.5% to 2.5% have been reported.

CONCLUSIONS

The findings from our meta-analysis of RCTs indicate that exercise can significantly enhance bone strength at loaded sites in children but not in adults. Since few RCTs were conducted to investigate exercise effects on bone strength, there is still a need for further well-designed, long-term RCTs with adequate sample sizes to quantify the effects of exercise on whole bone strength and its structural determinants throughout life.

Three-month weight reduction does not compromise bone strength in obese premenopausal women

Weight loss is claimed to cause bone loss. This prospective 12-month study evaluated effects of 3-month group-based weight loss with VLED on body composition, bone mass and strength (DXA and pQCT), muscle performance and biomarkers of bone turnover. The assessments were done at baseline and at 3 and 12 months. Sixty-two women of the recruited 75 obese (BMI>30) premenopausal women who completed the study were divided into 3 groups based on the tertiles of weight loss at 3 months. The group means of weight losses were 15.5% (Large), 10.5% (Medium) and 5.9% (Low). Statistical analyses were based on analysis of covariance. Bone turnover increased during the weight reduction period in all groups but practically returned to baseline during the weight maintenance phase. In general, mean bone changes remained marginal (approximately +/-1%) and the amount of weight reduction was not associated with bone loss. The only notable change was the 4% decline in bending strength at the distal radius. These results indicate that in obese premenopausal women, 3-month weight reduction resulted in increased bone turnover but was not deleterious for bone mass or strength at 3 months or after 9-month weight maintenance.

Time-course of exercise and its association with 12-month bone changes

Background

Exercise has been shown to have positive effects on bone density and strength. However, knowledge of the time-course of exercise and bone changes is scarce due to lack of methods to quantify and qualify daily physical activity in long-term. The aim was to evaluate the association between exercise intensity at 3, 6 and 12 month intervals and 12-month changes in upper femur areal bone mineral density (aBMD) and mid-femur geometry in healthy premenopausal women.

Methods

Physical activity was continuously assessed with a waist-worn accelerometer in 35 healthy women (35-40 years) participating in progressive high-impact training. To describe exercise intensity, individual average daily numbers of impacts were calculated at five acceleration levels (range 0.3-9.2 g) during time intervals of 0-3, 0-6, and 0-12 months. Proximal femur aBMD was measured with dual x-ray absorptiometry and mid-femur geometry was evaluated with quantitative computed tomography at the baseline and after 12 months. Physical activity data were correlated with yearly changes in bone density and geometry, and adjusted for confounding factors and impacts at later months of the trial using multivariate analysis.

Results

Femoral neck aBMD changes were significantly correlated with 6 and 12 months' impact activity at high intensity levels (> 3.9 g, r being up to 0.42). Trochanteric aBMD changes were associated even with first three months of exercise exceeding 1.1 g (r = 0.39-0.59, p < 0.05). Similarly, mid-femoral cortical bone geometry changes were related to even first three months' activity (r = 0.38-0.52, p < 0.05). In multivariate analysis, 0-3 months' activity did not correlate with bone change at any site after adjusting for impacts at later months. Instead, 0-6 months' impacts were significant correlates of 12-month changes in femoral neck and trochanter aBMD, mid-femur bone circumference and cortical bone attenuation even after adjustment. No significant correlations were found at the proximal or distal tibia.

Conclusion

The number of high acceleration impacts during 6 months of training was positively associated with 12-month bone changes at the femoral neck, trochanter and mid-femur. These results can be utilized when designing feasible training programs to prevent bone loss in premenopausal women.

Trial registration

Clinical trials.gov NCT00697957

Bone mass and structure in adolescents with type 1 diabetes compared to healthy peers

SUMMARY

We measured bone mass and structure using pQCT and DXA in adolescents with Type 1 diabetes and compared the results with those of healthy peers. Our results showed that diabetes is associated with reduced bone mass and smaller bones. The diabetes-associated deficits seemed to concern male adolescents more than females.

INTRODUCTION

The aim of this study was to compare bone mass and structure between adolescents with type 1 diabetes and their healthy peers.

METHODS

Peripheral quantitative computed tomography (pQCT) at radius and tibia, and dual-energy X-ray absorptiometry (DXA) at lumbar spine and proximal femur were performed for 48 adolescents, 26 girls and 22 boys, with type 1 diabetes, and for healthy peers matched for age, sex, body height and weight, and pubertal maturity.

RESULTS

Diabetes was associated with reduced bone mineral content (BMC) and smaller bone cross-sectional size. Diabetic boys seemed to be more affected than diabetic girls. Among the boys, the mean deficit in BMC of all measured skeletal sites was more than 10%, while among the girls it was less than 5%.

CONCLUSION

In conclusion, type 1 diabetes is associated with reduced BMC and appears to affect bone cross-sectional size and cortical rigidity. The diabetes-related skeletal deficits seemed to concern male adolescents more than females. Whether diabetes-related deficits would contribute to an increased risk of fractures in adulthood or later in life remains to be confirmed.

Maintenance of exercise-induced benefits in physical functioning and bone among elderly women

SUMMARY

This study showed that about a half of the exercise-induced gain in dynamic balance and bone strength was maintained one year after cessation of the supervised high-intensity training of home-dwelling elderly women. However, to maintain exercise-induced gains in lower limb muscle force and physical functioning, continued training seems necessary.

INTRODUCTION

Maintenance of exercise-induced benefits in physical functioning and bone structure was assessed one year after cessation of 12-month randomized controlled exercise intervention.

METHODS

Originally 149 healthy women 70-78 years of age participated in the 12-month exercise RCT and 120 (81%) of them completed the follow-up study. Self-rated physical functioning, dynamic balance, leg extensor force, and bone structure were assessed.

RESULTS

During the intervention, exercise increased dynamic balance by 7% in the combination resistance and balance-jumping training group (COMB). At the follow-up, a 4% (95% CI: 1-8%) gain compared with the controls was still seen, while the exercise-induced isometric leg extension force and self-rated physical functioning benefits had disappeared. During the intervention, at least twice a week trained COMB subjects obtained a significant 2% benefit in tibial shaft bone strength index compared to the controls. A half of this benefit seemed to be maintained at the follow-up.

CONCLUSIONS

Exercise-induced benefits in dynamic balance and rigidity in the tibial shaft may partly be maintained one year after cessation of a supervised 12-month multi-component training in initially healthy elderly women. However, to maintain the achieved gains in muscle force and physical functioning, continued training seems necessary.

A novel DXA-based hip failure index captures hip fragility independent of BMD

Capability of a novel dual-energy X-ray absorptiometry (DXA)-based hip failure index (HiFI) to discriminate between hip fracture cases and controls was evaluated. Given the constraints of planar DXA, the femoral neck was assumed a foam-filled ( approximately trabecular bone), thin-walled ( approximately cortical bone) sandwich structure, while HiFI estimated the critical force sufficient to buckle the wall of such a structure. Proximal femur DXA data from 1379 women aged 65yr and older, 268 with prior hip fracture were used. Comparison between standard areal bone mineral density (BMD), femur strength index (FSI), and HiFI was based on areas under receiver operatoring characteristic curves (AUC). The mean femoral neck BMD (SD) was 0.689 (0.109) g/cm(2) among the cases and 0.768 (0.119) g/cm(2) among the controls; the mean FSI 1.33 (0.36) and 1.54 (0.41), and the mean HiFI -0.28 (0.14) and -0.18 (0.15), respectively; all intergroup differences were highly significant (p<0.001). The intergroup difference for HiFI remained significant (p<0.002) after adjusting for age and BMD or FSI. The AUCs were 0.696 (95% confidence interval [CI]: 0.661-0.730) for BMD, 0.665 (0.630-0.700) for FSI, and 0.701 (0.666-0.736) for HiFI. In conclusion, HiFI may capture structural traits that account for femoral neck fragility independently of BMD or FSI. Obviously, the use of actual geometric and structural information from three-dimensional imaging of the femoral neck would help diminish the crude assumptions of the present DXA approach and reveal the true potential of the HiFI approach to gauge hip fragility and identify at-risk individuals for hip fractures.

Genetic and environmental influence on structural strength of weight-bearing and non-weight-bearing bone: a twin study

A bivariate genetic analysis among 217 older female twin pairs showed that, although the structural strength of tibia and radius are mainly regulated by same genetic and environmental factors, the tibia is more affected by environment.

INTRODUCTION

The habitual loading environment of the bone may modulate the relative contribution of genetic and environmental factors to bone structure. The purpose of this study was to estimate the contribution of the common and site-specific genetic and environmental factors to interindividual variation in compressive structural strength of the weight-bearing tibia and non-weight-bearing radius.

MATERIALS AND METHODS

pQCT scans were obtained from both members of 103 monozygotic (MZ) and 114 dizygotic (DZ) 63- to 76-yr-old female twin pairs to estimate the compressive strength of the distal tibia and distal radius. Quantitative genetic models were used to decompose the phenotypic variance into additive genetic, shared environmental, and individual environmental effects at each bone site and to study whether these bone sites share genetic or environmental effects.

RESULTS

The MZ and DZ twins did not differ in mean age, height, weight, or bone structural strength. The age-adjusted Cholesky model showed that additive genetic factors accounted for 83% (95% CI, 77-88%) of the variance in radial strength and 61% (95% CI, 52-69%) of the variance in tibial strength, and these were fully correlated. A shared environmental factor accounted for 15% (95% CI, 10-20%) of tibial strength. An individual environmental factor accounted for 17% (95% CI, 12-23%) of the variance in radial strength and 10% (95% CI, 5-17%) of the variance in tibial strength. The relative contribution of an individual environmental factor specific to tibial strength was 14% (95% CI, 11-18%).

CONCLUSIONS

The results suggest that, in older women, the majority of the individual differences in the compressive structural strength of the forearm and leg are regulated by genetic and environmental factors that are common to both bone sites. However, the relative importance of environmental factors was greater for the weight-bearing tibia than for the non-weight-bearing radius. Thus, the heritability of bone strength seems to vary between skeletal sites according to differences in the typical loading environment.

Influence of calcium intake and physical activity on proximal femur bone mass and structure among pre- and postmenopausal women. A 10-year prospective study

This 10-year follow-up evaluated the effect of physical activity and calcium intake on proximal femur bone mass (BMC) and structural indices (CSA and Z) and physical performance. A cohort of 133 premenopausal and 134 postmenopausal women with contrasting levels of physical activity (high [PA+]) and low [PA-]) and calcium intake (high [Ca+] and low [Ca-]) was measured with DXA at baseline and 5 and 10 years thereafter. Among premenopausal women, the mean (95% CI) femoral neck BMC was 3.8% (-0.1 to 7.8%) and the trochanter BMC 6.7% (2.4 to 11.3%) greater in the PA+ group than the PA- group. There was no difference between the Ca-intake groups. Among postmenopausal women, the mean femoral neck BMC was 4.2% (-0.2 to 8.8%) greater in the Ca+ group than in the Ca- group and 6.9% (2.2 to11.8%) greater in the PA+ group than in the PA- group. For trochanter BMC, the corresponding differences were 2.7% (-1.6 to 7.2%) and 5.5% (0.9 to 10.3%). The mean differences in CSA and Z were 3.8% (-0.9 to 8.7%) and 4.4% (-2.1 to 11.4%) in favor of the Ca+ group and 6.8% (1.9 to 12.0%) and 9.6% (2.5 to 17.1%) in favor of the PA+ group, respectively. Proximal femur BMC declined generally, but the initial differences between the physical activity and the calcium intake groups were maintained. High calcium intake seemed to slow the decline in trochanter BMC in premenopausal women, while high physical activity was beneficial for proximal femur, particularly among older women.

Race and ethnic variation in proximal femur structure and BMD among older men

Femoral neck dimensions and vBMD from QCT were compared among 3,305 black, Asian, Hispanic, and white men >or=65 yr of age. All had similar stature-adjusted mean femoral neck volume, but black and Asian men had thicker cortices and higher trabecular vBMD, which may increase bone strength.

INTRODUCTION

Hip fracture rates among elderly U.S. black and Asian men are lower than rates among white men. Structural characteristics or volumetric BMD (vBMD), which confer advantages for femoral neck bone strength, may vary by race/ethnicity. However, this topic has not been studied in detail.

MATERIALS AND METHODS

In a cross-sectional study, dimensions and vBMD in the femoral neck and shaft were obtained from QCT scans among 3,305 men >or=65 yr of age in the Osteoporotic Fractures in Men (MrOS) study. Femoral neck measures were cross-sectional area; integral, cortical, and medullary volumes and integral, cortical, and trabecular vBMD. Shaft measures were cross-sectional, cortical, and medullary areas and cortical vBMD. Self-reported race/ethnicity was classified as black, Asian, Hispanic, or white. We used multivariable linear regression models with adjustment for age, height, and body mass index to compare means of the outcome measures in black, Asian, and Hispanic men to those in whites.

RESULTS

All groups had similar femoral neck integral volume. Among black and Asian men, mean cortical volume as a percent of integral volume was 6% greater, integral vBMD was 6-10% greater, and trabecular vBMD was 33-36% greater than means among whites. Shaft cross-sectional area was similar among blacks, but smaller among Asians, compared with whites. However, mean shaft cortical area was greater among blacks but similar among Asians and whites, resulting in mean cortical thickness being 5% greater among black and Asian men. Blacks also had greater mean cortical vBMD in both the femoral neck and shaft.

CONCLUSIONS

Black and Asian men >or=65 yr of age have features in the proximal femur that may confer advantages for bone strength. Specifically, greater cortical thickness and higher trabecular vBMD among black and Asian men could help explain the lower hip fracture rates in these populations. Discerning the mechanisms underlying these differences could provide advances for the prevention and treatment of osteoporosis.

Load-specific differences in the structure of femoral neck and tibia between world-class moguls skiers and slalom skiers

Bone structure of weight-bearing proximal femur and tibia was examined among the Finnish world-class moguls skiers and slalom skiers. We hypothesized that these bones, during typical sport-specific performance, had been subjected not only to extreme loading but also to distinct loading in terms of rate and primary direction. Bone [dual-energy X-ray absorptiometry (DXA), peripheral quantitative computed tomography (pQCT), magnetic resonance imaging] and muscle performance data of the lower extremities were obtained from the five Finnish male moguls skiers and six slalom skiers competing at the World Cup level. Data (DXA, pQCT) from 12 age- and weight-matched normally active men were used for comparison. The ANCOVA with body height as a covariate was used for statistical analysis. The weight-bearing bones of the athletes were 10-60% stronger than those of the normally active men. Compared with the moguls skiers, the slalom skiers showed an average 43% thicker anterior cortex at the narrowest region of the femoral neck. This study suggests that the bone structure at skiers' heavily loaded lower extremities was very robust. A specific finding was the thick anterior cortex of the femoral neck among the slalom skiers. Apparently, the predominant loading type had modulated the site-specific skeletal response to physical exertion.

Age-related decline in trabecular and cortical density: a 5-year peripheral quantitative computed tomography follow-up study of pre- and postmenopausal women

This 5-year prospective study assessed changes in trabecular and cortical volumetric bone density at the non-weight-bearing radius and weight-bearing tibia among clinically healthy pre- and postmenopausal women. Altogether 79 premenopausal (mean age +/- SD at baseline 33 +/- 2 years) and 108 postmenopausal (68 +/- 2 years) women participated in the baseline and follow-up measurements. Trabecular density (TrD) of the distal radius and tibia and cortical density (CoD) of the radial and tibial shafts were assessed by peripheral quantitative computed tomography (pQCT). Repeated measures analysis of variance was used to analyze differences of means and mean changes between the age groups. As expected, TrD and CoD values were greater among premenopausal than postmenopausal women. Changes in radial TrD were similar in both age groups: mean (95% confidence interval) TrD of the distal radius declined by 3.0 mg/cm(3) (-0.9 to 7.0) and 5.1 mg/cm(3) (1.8-8.5) in the younger and older age groups, respectively. The respective declines in TrD of the distal tibia were 4.1 mg/cm(3) (2.1-6.0) and 2.8 mg/cm(3) (1.2-4.3). Decline in CoD was greater in the older than younger age group at both the radial and tibial shafts (P < 0.001). The mean absolute declines in radial CoD were 33.3 mg/cm(3) (27.9-38.7) and 49.4 mg/cm(3) (44.9-53.9) in younger and older women, and the declines in tibial CoD were 16.5 mg/cm(3) (12.6-20.2) and 28.1 mg/cm(3) (25.0-31.2), respectively. In conclusion, volumetric TrD in the weight-bearing tibia and non-weight-bearing radius showed similar age-related declines among pre- and postmenopausal women, while the decline in CoD was greater among postmenopausal women.

Tibial geometry is associated with failure load ex vivo: a MRI, pQCT and DXA study

We studied the relations between bone geometry and density and the mechanical properties of human cadaveric tibiae. Bone geometry, assessed by MRI and pQCT, and bone density, assessed by DXA, were significantly associated with bone's mechanical properties. However, cortical density assessed by pQCT was not associated with mechanical properties.

INTRODUCTION

The primary objective of this study was to determine the contribution of cross-sectional geometry (by MRI and pQCT) and density (by pQCT and DXA) to mechanical properties of the human cadaveric tibia.

METHODS

We assessed 20 human cadaveric tibiae. Bone cross-sectional geometry variables (total area, cortical area, and section modulus) were measured with MRI and pQCT. Cortical density and areal BMD were measured with pQCT and DXA, respectively. The specimens were tested to failure in a four-point bending apparatus. Coefficients of determination between imaging variables of interest and mechanical properties were determined.

RESULTS

Cross-sectional geometry measurements from MRI and pQCT were strongly correlated with bone mechanical properties (r(2) range from 0.55 to 0.85). Bone cross-sectional geometry measured by MRI explained a proportion of variance in mechanical properties similar to that explained by pQCT bone cross-sectional geometry measurements and DXA measurements.

CONCLUSIONS

We found that there was a close association between geometry and mechanical properties regardless of the imaging modality (MRI or pQCT) used.

Effect of impact exercise and its intensity on bone geometry at weight-bearing tibia and femur

INTRODUCTION

Physical activity is known to enhance the mechanical competence of bone. However, information about the optimal type of exercise is limited. The aim of this study was to evaluate the contribution of jumping exercise to changes in bone geometry.

METHODS

We carried out a 12-month population-based trial with 120 women (aged 35-40 years), randomly assigned to an exercise group or to a control group. The exercise regimen consisted of supervised, progressive high-impact exercises three times per week and an additional home program. The intensity of impact loading was assessed as the magnitude of acceleration peaks using an accelerometer-based body movement monitor. The activity was analyzed as the daily number of impacts within five acceleration ranges (0.3-1.0g, 1.1-2.4g, 2.5-3.8g, 3.9-5.3g and 5.4-9.2g; g=acceleration of gravity, 9.81 m/s(2)). Bone geometry was assessed with spiral quantitative computed tomography (QCT) scanner at mid-femur, proximal tibia and distal tibia.

RESULTS

Thirty-nine women (65%) in the exercise group and 41 women (68%) in the control group completed the study. QCT and physical activity data were available from 65 subjects. The exercise group showed a significant 0.2% (p=0.033) higher gain in bone circumference compared to the control group at mid-femur. Subgroup analyses revealed geometric changes indicating up to a 2.5% increment in bone strength in favor of the most active exercisers (>66 exercise sessions during the 12 months) compared to the least active exercisers (<19 sessions). In pooled groups, the changes in cortical attenuation and cross-sectional moment of inertia correlated positively (p<0.05-p<0.01) with the number of impacts exceeding 1.1g, while changes in cortical thickness (p<0.05) and bone circumference (p<0.05-p<0.01) were positively associated with impacts 3.9g, or more. The number and intensity of impacts during the 12 months were the most significant predictors of changes in bone geometry explaining up to 36% of changes.

CONCLUSIONS

Bone geometry adapts to impact exercise and the adaptation is most marked at the mid-femur. The changes in bone geometry are associated with the number and intensity of daily impacts while the redistribution of bone mineral appears to be the main mechanism in the skeletal adaptation to varying intensities of exercise.

Young-elderly differences in bone density, geometry and strength indices depend on proximal femur sub-region: a cross sectional study in Caucasian-American women

Fragility fractures at the trochanter (TR) and the femoral neck (FN) have distinct etiologies, but the underlying age-related structural changes at these proximal femoral sub-regions are poorly understood. 28 young (41+/-3 years) and 124 elderly (74+/-3 years) healthy Caucasian women underwent volumetric quantitative computed tomography at the hip. Integral (i), cortical (c) and trabecular (t) bone mineral density and content (BMD, BMC) were measured. Geometric parameters included cross sectional area (CSA), and volumes of the integral, cortical and trabecular regions (VOL). Structural measures included indices of compressive (Compstr) and bending (BSI) strength. After adjusting for height and weight, an F-test was used to compare the TR and the FN mean values between young and elderly and to test for interaction to compare logarithmic difference of young and elderly (log(Young)-log(Elderly), Y/Ed) between the FN and the TR in an ANOCOVA model. All BMC, iBMD and tBMD values were significantly lower in elderly than in young women, with the largest Y/Ed in the FN tBMC and tBMD (P<0.0011 and P<0.0001). cBMD in young and elderly groups was not significantly different at the TR while at the FN it was greater (P=0.0075) in elderly than young women, showing significant Y/Ed (P=0.0003) dependence on skeletal site. Elderly women had significantly larger iVOL and CSA values (0.0001<P<0.0051), except for the FN iVOL. cVOL values were smaller in elderly than young women (P<0.0001). Y/Ed in bone geometry differed by sub-region only for cVOL measures (P=0.0267). Despite larger CSA and iVOL measures in elderly, the younger women had greater Compstr (P<0.0001) and BSI (P=0.0051). Thus, although both the TR and the FN appear to increase in size with age, this enlargement is insufficient to protect against loss of bone strength.

Loading modalities and bone structures at nonweight-bearing upper extremity and weight-bearing lower extremity: a pQCT study of adult female athletes

This cross-sectional study of adult female athletes assessed whether the apparent loading-related differences in bone structure are primarily associated with the loading type or the muscle performance-related joint moments. Several structural variables at shaft sites of the tibia, radius and humerus, and distal sites of the tibia and radius were measured with peripheral quantitative computed tomography (pQCT) among 113 female national level athletes (representing hurdling, volleyball, soccer, racket-sports and swimming) and their 30 nonathletic referents. For the weight-bearing lower extremities, the loading modalities of the above sports were classified into high-impact (hurdling, volleyball), odd-impact (soccer, racket-sports) and repetitive, nonimpact (swimming) loadings; and for the nonweight-bearing upper extremities into high magnitude (functional weightlifting in hurdling and soccer), impact (volleyball, racket-sports) and repetitive, nonimpact (swimming) loadings. As expected, athletes' bone mass was substantially higher at loaded bone sites compared with the nonathletic referents, but more pertinently to the locomotive perspective, the loading-induced additional bone mass seemed to be used to build mechanically strong and appropriate bone structures. Compared with controls, the weight-bearing bone structures of female athletes (swimmers excluded) were characterized by larger diaphysis, thicker cortices and somewhat denser trabecular bone. The athletes' bones at the nonweight-bearing upper extremity were generally larger in cross-sectional area. The estimated indices of joint moment (muscle force x estimated lever arm) were explained from 29% to 50%, and the loading modalities from 8% to 25%, of the variance in most bone variables (P < 0.05) of the tibia (shaft and distal site). In contrast to the weight-bearing tibia, only the estimated joint moment was positively associated (P < 0.05) with the structural characteristics of the radius and humerus, accounting for 6% to 26% of the variance in bone variables of the shafts of these bones. Such association was not observed at the distal radius. In conclusion, at the weight-bearing lower extremity, the strong bone structure of the female athletes was attributable to muscle performance-related estimated joint moments and impact loading modality. At the shaft sites of the nonweight-bearing upper extremity, the strong bone structure was mainly attributable to the estimated joint moments. Thus, different loading history and other features of loading seemed to govern the skeletal adaptation at the upper and lower extremity.

Lifetime sport and leisure activity participation is associated with greater bone size, quality and strength in older men

INTRODUCTION

It remains uncertain whether long-term participation in regular weight-bearing exercise confers an advantage to bone structure and strength in old age. The aim of this study was to investigate the relationship between lifetime sport and leisure activity participation on bone material and structural properties at the axial and appendicular skeleton in older men (>50 years).

METHODS

We used dual-energy X-ray absorptiometry (DXA) to assess hip, spine and ultradistal (UD) radius areal bone mineral density (aBMD) (n=161), quantitative ultrasound (QUS) to measure heel bone quality (n=161), and quantitative computed tomography (QCT) to assess volumetric BMD, bone geometry and strength at the spine (L(1)-L(3)) and mid-femur (n=111). Current (>50+ years) and past hours of sport and leisure activity participation during adolescence (13-18 years) and adulthood (19-50 years) were assessed by questionnaire. This information was used to calculate the total time (min) spent participating in sport and leisure activities and an osteogenic index (OI) score for each participant, which provides a measure of participation in weight-bearing activities.

RESULTS

Regression analysis revealed that a greater lifetime (13-50+ years) and mid-adulthood (19-50 years) OI, but not total time (min), was associated with a greater mid-femur total and cortical area, cortical bone mineral content (BMC), and the polar moment of inertia (I (p)) and heel VOS (p ranging from <0.05 to <0.01). These results were independent of age, height (or femoral length) and weight (or muscle cross-sectional area). Adolescent OI scores were not found to be significant predictors of bone structure or strength. Furthermore, no significant relationships were detected with areal or volumetric BMD at any site. Subjects were then categorized into either a high (H) or low/non-impact (L) group during adolescence (13-18 years) and adulthood (19-50+ years) according to their OI scores during each of these periods. Three groups were subsequently formed to reflect weight-bearing impact categories during adolescence and then adulthood: LL, HL and HH. Compared to the LL group, mid-femur total and cortical area, cortical BMC and I (p) were 6.5-14.2% higher in the HH group. No differences were detected between the LL and HL groups.

CONCLUSIONS

In conclusion, these findings indicate that long-term regular participation in sport and leisure activities categorized according to an osteogenic index [but not the total time (min) spent participating in all sport and leisure activities] was an important determinant of bone size, quality and strength, but not BMD, at loaded sites in older men. Furthermore, continued participation in weight-bearing exercise in early to mid-adulthood appears to be important for reducing the risk of low bone strength in old age.

Comparison of volumetric bone mineral density in the tibial region of interest for ACL reconstruction

Adequate tibial bone mineral density (BMD) is essential to soft tissue graft fixation during anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare volumetric bone plug density measurements at the tibial region of interest for ACL reconstruction using a standardized immersion technique and Archimedes' principle. Cancellous bone cores were harvested from the proximal, middle, and distal metaphyseal regions of the lateral tibia and from the standard tibial tunnel location used for ACL reconstruction of 18 cadaveric specimens. Proximal tibial cores displayed 32.6% greater BMD than middle tibial cores and 31.8% greater BMD than distal tibial cores, but did not differ from the BMD of the tibial tunnel cores. Correlational analysis confirmed that the cancellous BMD in the tibial tunnel related to the cancellous BMD of the proximal and distal lateral tibial metaphysis. In conjunction with its adjacent cortical bone, the cancellous BMD of the region used for standard tibial tunnel placement provides an effective foundation for ACL graft fixation. In tibia with poor BMD, bicortical fixation that incorporates cortical bone from the distal tibial tunnel region is recommended.

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.

INTRODUCTION

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSION

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.