Influence of puberty on muscle area and cortical bone area of the forearm in boys and girls

Assessing the Muscle-Bone Unit in Girls Exposed to Different Amounts of Impact-Loading Physical Activity-A Cross-Sectional Association Study

BACKGROUND/OBJECTIVES

In children, an association exists between muscle and bone, as well as between physical activity and osteogenesis. Impact loading is a factor in increasing bone accrual during growth. In this work, we explored the muscle-bone association in girls exposed to long-term physical activity at different levels of impact loading.

METHODS

Four groups of girls aged 7-16 were considered. The curricular (C; n = 22) group only had curricular physical activity at school (2 h/w). In addition to curricular physical activity, the girls in the dance (D; n = 21), gymnastics at lower training (GL; n = 14), and gymnastics at higher training (GH; n = 20) groups had 2 h/w, 4 h/w, and 4 h/w < training ≤ 12 h/w additional physical activity, respectively, for at least one year. A visual analysis estimated the respective amounts of impact-loading activity. The bone mineral content (BMC), areal bone mineral density (aBMD), and fat-free soft tissue mass (FFSTM) were assessed with dual-energy X-ray absorptiometry.

RESULTS

The results showed that, after adjusting for several confounders, statistically significant correlations were present between muscle mass and several bone mineral variables. A regression analysis confirmed the correlation in the data, and showed the marginal role of other body composition variables and physical activity for predicting BMC and BMD.

CONCLUSION

Skeletal muscle mass is a major determinant of the BMC and BMD of the TBLH, as well as of the Appendicular level, in girls exposed to different amounts of long-term impact-loading physical activity.

Cortical impairment and reduced muscle mass in children and young adults with nephropathic cystinosis

Nephropathic cystinosis is an orphan autosomal recessive lysosomal storage disease characterized by a deficiency of cystinosin, a cystine transporter protein, leading to tissue damage, primarily in the kidney and cornea. With the introduction of cystine-depleting therapy with cysteamine and the possibility to survive to adulthood, new challenges of skeletal complications are a concern, with sparse data available regarding bone development. The aim of the current study was to gain more information on bone density and geometry in these patients. Fifty-one patients (29 males, 22 females) with genetically proven nephropathic cystinosis were clinically evaluated with a medical history, physical examination, grip strength measurements, and biochemical and imaging studies. Bone mineral density, bone geometry, and muscle cross sectional area were measured, and muscle was evaluated. Results were compared with age- and gender-specific reference data. Z-scores for height (mean [M] = -1.75, standard deviation [SD] = 1.43), weight (M = -1.67, SD = 1.29), and BMI (M = -0.98, SD = 1.29) were lower than reference data. Medullary cross-sectional area (CSA) and cortical density z-scores were not compromised (M = 0.12, SD = 1.56 and M = -0.25, SD = 1.63, respectively), but cortical CSA z-scores and Strength-Strain Index (SSI) were reduced (M = -2.16, SD = 1.08, M = -2.07, SD = 1.08). Muscular deficits were reflected by reduced z-scores for muscle CSA (M = -2.43, SD = 1.27) and grip strength (M = -3.01, SD = 1.10), along with jump force (34% lower than reference value). Multiple regression analyses indicated an association of muscle mass with medullary CSA and SSI, but not with cortical CSA. While bone density parameters were normal, bone geometry was altered, resulting in a thinner cortex with possible impact on bone strength. Muscle weakness be partially responsible for altered bone geometry and could provide a potential treatment target.

Gains in relative cortical area during growth and their relationship to nutrition, body size, and physical activity

OBJECTIVES

In studies of growth in the past, low percentage of cortical area (%CA) is commonly attributed to poor general health, due to factors including poor nutrition, low socioeconomic status, or other physiological stressors. What constitutes low relative cortical dimensions has not been established across a diverse range of human skeletal samples. This study examines %CA in a large immature skeletal sample to establish typical variation in humans with consideration of both body mass and subsistence strategy.

MATERIALS AND METHODS

Percentage of cortical area was calculated at the midshaft of the humerus, femur, and tibia in seven skeletal samples. Age at death was estimated from dental development, and body mass from bone dimensions. Patterns of %CA with age and log-transformed body mass were examined in the pooled sample and compared among samples using LOESS regression, Welch's ANOVA, and Kruskal-Wallis tests.

RESULTS

Across all samples, %CA displays a generally non-linear pattern, but variation in %CA with age was high, particularly in samples with lower levels of %CA. There was no relationship between %CA and age-adjusted body mass.

DISCUSSION

The lack of a relationship between %CA and body mass suggests that %CA should not be used as an indicator of mechanical loading. The variation present across samples implies that appositional bone growth is affected by physiological stress in varying ways. Without a deeper understanding of what is "typical" for long bone development, it is impossible to draw conclusions about individual or population level health.

Characterizing the Adolescent Premature Ovarian Insufficiency Phenotype: A Case Control Study

STUDY OBJECTIVES

To characterize the skeletal, cardiometabolic, cognitive, and mental health phenotype of adolescents with idiopathic premature ovarian insufficiency (POI) DESIGN: Case control SETTING: Pediatric tertiary referral center in Cincinnati, Ohio PARTICIPANTS: Nine adolescents (ages 11-18.99 years) with newly diagnosed POI and 9 normally menstruating controls, matched by age and body mass index MAIN OUTCOME MEASURES: Between-group comparisons of bone characteristics assessed by dual energy x-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT), psychosocial health (anxiety, depression, and quality of life), and cognition and memory by questionnaire RESULTS: Adolescents with POI had lower bone density Z-scores by DXA (lumbar spine -1.93 vs 0.80; whole body less head -2.05 vs 0.00; total hip -1.03 vs 0.83; and femoral neck -1.23 vs 0.91; all P < .001), as well as lower trabecular volumetric bone mineral density (tibia 3% site 226 vs 288 mg/mm³, P < .001; radius 3% site 200 vs 251, P = .001), smaller cortical area (tibia 66% site 251 vs 292 mm², P = .028), and thickness (tibia 66% site 3.56 vs 4.30 mm, P = .001) than controls. No abnormalities in cardiometabolic biomarkers were detected in POI cases. Adolescents with POI were also more likely to report low energy (78% vs 22%, P = .02).

CONCLUSION

Estrogen deficiency adversely affects bone health in adolescents with POI. However, we did not find associations with cardiometabolic, mental health, or cognitive outcomes in this small sample.

Association of Sarcopenia with Osteopenia and Osteoporosis in Community-Dwelling Older Korean Adults: A Cross-Sectional Study

Sarcopenia and bone disorders, such as osteopenia and osteoporosis, are common musculoskeletal disorders in older adults. Therefore, this study aimed to establish the association between sarcopenia and bone disorders such as osteoporosis and osteopenia according to sex. We analyzed 3077 participants from the 2008-2011 Korean National Health and Nutrition Examination Survey aged 65 years or older. After adjusting for all covariates, such as physical examinations, exercise, and nutrient intake (model 4), the odds ratios for the association between sarcopenia and bone disorders were 2.051 (95% confidence interval [CI]: 1.498-2.808) in osteopenia and 2.258 (95% CI: 1.584-3.218) in osteoporosis. However, when sex was analyzed separately, the odds ratio was significantly different in men (osteopenia-2.068, 95% CI: 1.462-2.924; osteoporosis-3.247, 95% CI: 1.953-5.399), but not in women. Therefore, the results of this study show an association between sarcopenia and bone disorders in older Korean adults. Sarcopenia is significantly related to osteopenia and osteoporosis, especially in men, when stratified by sex.

Biomechanical Evaluation on the Bilateral Asymmetry of Complete Humeral Diaphysis in Chinese Archaeological Populations

Diaphyseal cross-sectional geometry (CSG) is an effective indicator of humeral bilateral asymmetry. However, previous studies primarily focused on CSG properties from limited locations to represent the overall bilateral biomechanical performance of humeral diaphysis. In this study, the complete humeral diaphyses of 40 pairs of humeri from three Chinese archaeological populations were scanned using high-resolution micro-CT, and their biomechanical asymmetries were quantified by morphometric mapping. Patterns of humeral asymmetry were compared between sub-groups defined by sex and population, and the representativeness of torsional rigidity asymmetry at the 35% and 50% cross-sections (J35 and J50 asymmetry) was testified. Inter-group differences were observed on the mean morphometric maps, but were not statistically significant. Analogous distribution patterns of highly asymmetrical regions, which correspond to major muscle attachments, were observed across nearly all the sexes and populations. The diaphyseal regions with high variability of bilateral asymmetry tended to present a low asymmetrical level. The J35 and J50 asymmetry were related to the overall humeral asymmetry, but the correlation was moderate and they could not reflect localized asymmetrical features across the diaphysis. This study suggests that the overall asymmetry pattern of humeral diaphysis is more complicated than previously revealed by individual sections.

Gut microbiome depletion and repetitive mild traumatic brain injury differentially modify bone development in male and female adolescent rats

Dysregulation of the gut microbiome has been shown to disrupt both bone formation and bone resorption in several preclinical and clinical models. However, the role of microbiome in adolescent bone development remains poorly understood. This effect of disrupted bone development may be more pronounced during adolescence, when bone development is vulnerable to environmental stimuli and external insults (e.g., antibiotic treatment and traumatic brain injury), as this is a critical window of development. Therefore, in this study, we sought to investigate the effect of repetitive mild traumatic brain injury (RmTBI) and gut microbiome depletion by antibiotic treatment on femur length and bone density in male and female adolescent Sprague Dawley rats. Rats were randomly assigned to receive standard or antibiotic autoclaved drinking water and to receive sham or RmTBIs injuries. Using micro-computed tomography (μCT), we found sexually dimorphic changes in adolescent bone development in response to microbiome depletion and RmTBI. Specifically, gut microbiome depletion stunted femur growth in males and altered cross sectional bone area (CSA), bone area fraction, and the bone volume of low and mid density bone in the distal metaphyseal region of the femur. Conversely, RmTBI and antibiotic treatment individually disrupted bone growth, bone area fraction, and bone volume of high-density bone within the distal metaphyseal region of the femur in females, but not when combined. Therefore, findings from this study indicate that gut microbiome and RmTBI may alter bone development in a sex-dependent manner during adolescence.

Effects of Interval Exercise Training on Serum Biochemistry and Bone Mineral Density in Dogs

Simple Summary

In this study, six male beagle dogs underwent 12 weeks of interval exercise following the Frequency, Intensity, Time/duration, Type, Volume, and Progression (FITT-VP) training principle. The heart rate (HR) response was measured during the entire exercise period, and changes in bone mineral density (BMD), muscle volume (MV), and hematology and serum biomarkers were evaluated at the pre-exercise training period and post-exercise training period. We showed that exercise training increased BMD in the femur and serum total alkaline phosphatase (TALP), aspartate aminotransferase, and creatine kinase levels. In addition, our data suggest a positive correlation between BMD and TALP, demonstrating that increased TALP might be an important contributing factor for enhancing BMD with physical training in dogs.

Abstract

Exercise has been suggested as a powerful intervention for health care and fitness management in humans; however, few studies have demonstrated the benefits of exercise training in dogs. The purpose of this study was to examine the effects of exercise training on heart rate (HR), bone mineral density (BMD), muscle volume (MV), and hematological and serum biomarkers in dogs. Six healthy beagles completed the interval treadmill exercise, developed on the basis of the FITT principle, two times a week for 12 weeks. To evaluate the physiological parameters, the HR values were analyzed using the Polar H10 system during the entire exercise period. At pre-and post-exercise, quantitative computed tomography and hematological and serum biochemical parameters were analyzed. The interval exercise resulted in a normal HR response and no adverse behavioral or physiological effects on the dogs. We showed that exercise improved BMD in the femur (541.6 ± 16.7 vs. 610.2 ± 27.8 HA, p < 0.01) and increased serum total alkaline phosphatase (TALP; 68.6 ± 9.2 vs. 81.3 ± 17.2, p < 0.01), aspartate aminotransferase (23.5 ± 1.0 vs. 33.5 ± 1.6, p < 0.01), and creatine kinase (114.8 ± 5.3 vs. 214.0 ± 20.8, p < 0.01) levels. There was a positive relationship between BMD and TALP (femur: r = 0.760, p = 0.004; vertebrae: r = 0.637; p = 0.025). Our findings suggest that interval exercise training is beneficial to increase BMD in the femur, and an increased TALP level would be a concomitant mechanism for enhancing BMD with exercise in dogs.

A systematic review exploring the bidirectional relationship between puberty and autoimmune rheumatic diseases

BACKGROUND

Autoimmune rheumatic diseases (ARDs) are associated with a significant sex-bias, which becomes more evident post-puberty. This systematic review aims to elucidate the bidirectional relationship between puberty and ARD-related outcomes.

METHODS

Studies published in English until October 2019 were identified using a systematic search of endocrinology and rheumatology literature. Information was extracted on study design, sample size, demographics, puberty outcome measures, disease outcome measures, and main findings. The methodological quality of the studies included was analysed using the Newcastle-Ottawa Scale (NOS).

RESULTS

Sixteen non-randomised studies reporting on the impact of puberty on ARD outcomes (n = 7), ARD impact on puberty-related outcomes (n = 8), or both (n = 1) have been identified. The impact of puberty on ARD outcomes were investigated in patients with juvenile idiopathic arthritis (JIA)-associated uveitis (n = 1), juvenile systemic lupus erythematosus (JSLE) (n = 5) or in healthy controls who developed adult-onset SLE (n = 1) or had non-specific symptoms (n = 1). The impact of ARD on puberty outcomes was explored in JIA (n = 4) and JSLE (n = 3). Quality assessment of studies showed a small to moderate risk of bias overall (NOS 4-9/9). Due to large heterogeneity of the studies it was not possible to perform a meta-analysis. Multiple studies reported on delayed puberty in patients with JIA/JSLE, menstrual and hormonal abnormalities, and lower height and weight than controls. Earlier (pre-pubertal) onset of JSLE was correlated with more severe disease and more need for systemic treatment.

CONCLUSION

A bidirectional relationship exists between puberty and ARDs; however, more and better research is required to elucidate the complexity of this relationship. We propose puberty-related clinical assessments in patients with ARDs, which can improve patient outcomes and facilitate future research.

Testing the Functional Model of Bone Development: Direct and Mediating Role of Muscle Strength on Bone Properties in Growing Youth

This study examines the functional model of bone development in peri-pubertal boys and girls. Specifically, we implemented a mixed-longitudinal design and hierarchical structural models to provide experimental evidence in support of the conceptual functional model of bone development, postulating that the primary mechanical stimulus of bone strength development is muscle force. To this end, we measured radial and tibial bone properties (speed of sound, SOS), isometric grip and knee extensors strength, bone resorption (urinary NTX concentration), body mass index (BMI), somatic maturity (years from peak height velocity) and skeletal maturity (bone age) in 180 children aged 8–16 years. Measurements were repeated 2–4 times over a period of 3 years. The multilevel structural equation modeling of 406 participant-session observations revealed similar results for radial and tibial SOS. Muscle strength (i.e., grip strength for the radial and knee extension for tibial model) and NTX have a significant direct effect on bone SOS (β = 0.29 and −0.18, respectively). Somatic maturity had a direct impact on muscle strength (β = 0.24) and both a direct and indirect effect on bone SOS (total effect, β = 0.30). Physical activity and BMI also had a significant direct impact on bone properties, (β = 0.06 and −0.18, respectively), and an additional significant indirect effect through muscle strength (β = 0.01 and 0.05, respectively) with small differences per bone site and sex. Muscle strength fully mediated the impact of bone age (β = 0.14) while there was no significant effect of energy intake on either muscle strength or bone SOS. In conclusion, our results support the functional model of bone development in that muscle strength and bone metabolism directly affect bone development while the contribution of maturity, physical activity, and other modulators such as BMI, on bone development is additionally modulated through their effect on muscle strength.

Adolescent idiopathic scoliosis: The mechanobiology of differential growth

Adolescent idiopathic scoliosis (AIS) has been linked to neurological, genetic, hormonal, microbial, and environmental cues. Physically, however, AIS is a structural deformation, hence an adequate theory of etiology must provide an explanation for the forces involved. Earlier, we proposed differential growth as a possible mechanism for the slow, three-dimensional deformations observed in AIS. In the current perspective paper, the underlying mechanobiology of cells and tissues is explored. The musculoskeletal system is presented as a tensegrity-like structure, in which the skeletal compressive elements are stabilized by tensile muscles, ligaments, and fasciae. The upright posture of the human spine requires minimal muscular energy, resulting in less compression, and stability than in quadrupeds. Following Hueter-Volkmann Law, less compression allows for faster growth of vertebrae and intervertebral discs. The substantially larger intervertebral disc height observed in AIS patients suggests high intradiscal pressure, a condition favorable for notochordal cells; this promotes the production of proteoglycans and thereby osmotic pressure. Intradiscal pressure overstrains annulus fibrosus and longitudinal ligaments, which are then no longer able to remodel and grow, and consequently induce differential growth. Intradiscal pressure thus is proposed as the driver of AIS and may therefore be a promising target for prevention and treatment.

Sex differences in the longitudinal associations between body composition and bone stiffness index in European children and adolescents

Fat mass (FM) and fat free mass (FFM) may influence bone health differentially. However, existing evidences on associations between FM, FFM and bone health are inconsistent and vary according to sex and maturity. The present study aims to evaluate longitudinal associations between FM, FFM and bone stiffness index (SI) among European children and adolescents with 6 years follow-up. A sample of 2468 children from the IDEFICS/I.Family was included, with repeated measurements of SI using calcaneal quantitative ultrasound, body composition using skinfold thickness, sedentary behaviors and physical activity using self-administrated questionnaires. Regression coefficients (β) and 99%-confidence intervals (99% CI) were calculated by sex-specified generalized linear mixed effects models to analyze the longitudinal associations between FM and FFM z-scores (zFM and zFFM) and SI percentiles, and to explore the possible interactions between zFM, zFFM and maturity. Baseline zFFM was observed to predict the change in SI percentiles in both boys (β = 4.57, 99% CI: 1.36, 7.78) and girls (β = 3.42, 99% CI: 0.05, 6.79) after 2 years. Moreover, baseline zFFM (β = 8.72, 99% CI: 3.18, 14.27 in boys and β = 5.89, 99% CI: 0.34, 11.44 in girls) and the change in zFFM (β = 6.58, 99% CI: 0.83, 12.34 in boys and β = 4.81, 99% CI: -0.41, 10.02 in girls) were positively associated with the change in SI percentiles after 6 years. In contrast, a negative association was observed between the change in zFM and SI percentiles in boys after 6 years (β = -3.70, 99% CI: -6.99, -0.42). Besides, an interaction was observed between the change in zFM and menarche on the change in SI percentiles in girls at 6 years follow-up (p = .009), suggesting a negative association before menarche while a positive association after menarche. Our findings support the existing evidences for a positive relationship between FFM and SI during growth. Furthermore, long-term FM gain was inversely associated with SI in boys, whereas opposing associations were observed across menarche in girls.

Sex-Specific Muscular Mediation of the Relationship Between Physical Activity and Cortical Bone in Young Adults

Muscle mass is a commonly cited mediator of the relationship between physical activity (PA) and bone, representing the mechanical forces generated during PA. However, neuromuscular properties (eg, peak force) also account for unique portions of variance in skeletal outcomes. We used serial multiple mediation to explore the intermediary role of muscle mass and force in the relationships between cortical bone and moderate-to-vigorous intensity PA (MVPA). In a cross-sectional sample of young adults (n = 147, 19.7 ± 0.7 years old, 52.4% female) cortical diaphyseal bone was assessed via peripheral quantitative computed tomography at the mid-tibia. Peak isokinetic torque in knee extension was assessed via Biodex dynamometer. Thigh fat-free soft tissue (FFST) mass, assessed via dual-energy X-ray absorptiometry, represented the muscular aspect of tibial mechanical forces. Habitual MVPA was assessed objectively over 7 days using Actigraph GT3X+ accelerometers. Participants exceeded MVPA guidelines (89.14 ± 27.29 min/day), with males performing 44.5% more vigorous-intensity activity relative to females (p < 0.05). Males had greater knee extension torque and thigh FFST mass compared to females (55.3%, and 34.2%, respectively, all p < 0.05). In combined-sex models, controlling for tibia length and age, MVPA was associated with strength strain index (pSSI) through two indirect pathways: (i) thigh FFST mass (b = 1.11 ± 0.37; 95% CI, 0.47 to 1.93), and (i) thigh FFST mass and knee extensor torque in sequence (b = 0.30 ± 0.16; 95% CI, 0.09 to 0.73). However, in sex-specific models MVPA was associated with pSSI indirectly through its relationship with knee extensor torque in males (b = 0.78 ± 0.48; 95% CI, 0.04 to 2.02) and thigh FFST mass in females (b = 1.12 ± 0.50; 95% CI, 0.37 to 2.46). Bootstrapped CIs confirmed these mediation pathways. The relationship between MVPA and cortical structure appears to be mediated by muscle in young adults, with potential sex-differences in the muscular pathway. If confirmed, these findings may highlight novel avenues for the promotion of bone strength in young adults. © 2019 American Society for Bone and Mineral Research.

The muscle-bone unit in adolescent swimmers

Most researchers adjust bone by lean mass when comparing swimmers with controls. This adjustment is done under the assumption that lean affects bone similarly in both groups. Nonetheless, we found that the muscle-bone association is uncoupled in swimmers, and consequently, researchers should avoid this adjustment when evaluating swimmers' bone.

INTRODUCTION

To examine the functional and structural muscle-bone unit in adolescent swimmers.

METHODS

Sixty-five swimmers (34 girls/31 boys) and 119 controls (51 girls/68 boys) participated in the study. Muscle cross-sectional area (MCSA), bone mineral content (BMC), and polar strength-strain index (SSIPOL) were measured in the non-dominant radius by peripheral quantitative computed tomography (pQCT). Subtotal BMC and lean mass were evaluated with dual-energy X-ray absorptiometry (DXA). Handgrip and isometric knee extension (IKE) tests were performed to determine muscle force. The effect of MCSA, lean and force on SSIPOL, and BMC were tested, and the functional and structural muscle-bone ratios of swimmers and controls were compared.

RESULTS

Both muscle size (MCSA and lean) and muscle force (handgrip and IKE) influenced BMC and SSIPOL in swimmers and controls similarly. Swimmers presented normal MCSA and lean values for their height, but when compared with controls, swimmers presented a higher amount of lean and MCSA for the same BMC or SSIPOL (structural muscle-bone unit). For the functional muscle-bone unit, different results were found for the lower and upper limbs, as no differences were found for the upper limbs, while for the lower limbs, swimmers presented higher muscle force for the same amount of BMC.

CONCLUSIONS

The contradictory results regarding BMC in swimmers found in previous studies could partly be explained with the findings of the present study that reinforce the idea that swimming is not an effective sport to practice regarding bone mass and that the muscle-bone unit is different in swimmers than in controls.

Do bone geometric properties of the proximal femoral diaphysis reflect loading history, muscle properties, or body dimensions?

OBJECTIVES

The aim of this study was to investigate activity-induced effects from bone geometric properties of the proximal femur in athletic vs nonathletic healthy females by statistically controlling for variation in body size, lower limb isometric, and dynamic muscle strength, and cross-sectional area of Musculus gluteus maximus.

METHODS

The material consists of hip and proximal thigh magnetic resonance images of Finnish female athletes (N = 91) engaged in either high jump, triple jump, soccer, squash, powerlifting, endurance running or swimming, and a group of physically active nonathletic women (N = 20). Cross-sectional bone geometric properties were calculated for the lesser trochanter, sub-trochanter, and mid-shaft of the femur regions. Bone geometric properties were analyzed using a general linear model that included body size, muscle size, and muscle strength as covariates.

RESULTS

Body size and isometric muscle strength were positively associated with bone geometric properties at all three cross-sectional levels of the femur, while muscle size was positively associated with bone properties only at the femur mid-shaft. When athletes were compared to nonathletic females, triple jump, soccer, and squash resulted in greater values in all studied cross-sections; high jump and endurance running resulted in greater values at the femoral mid-shaft cross-section; and swimming resulted in lower values at sub-trochanter and femur mid-shaft cross-sections.

CONCLUSIONS

Activity effects from ground impact loading were associated with higher bone geometric values, especially at the femur mid-shaft, but also at lesser and sub-trochanter cross-sections. Bone geometric properties along the femur can be used to assess the mechanical stimuli experienced, where ground impact loading seems to be more important than muscle loading.

A longitudinal comparison of appendicular bone growth and markers of strength through adolescence in a South African cohort using radiogrammetry and pQCT

To compare growth patterns and strength of weight- and non-weight-bearing bones longitudinally. Irrespective of sex and ethnicity, metacarpal growth was similar to that of the non-weight-bearing radius but differed from that of the weight-bearing tibia. Weight- and non-weight-bearing bones have different growth and strength patterns.

INTRODUCTION

Functional loading modulates bone size and strength.

METHODS

To compare growth patterns and strength of weight- and non-weight-bearing bones longitudinally, we performed manual radiogrammetry of the second metacarpal on hand-wrist radiographs and measured peripheral quantitative computed tomography images of the radius (65%) and tibia (38% and 65%), annually on 372 black and 152 white South African participants (ages 12-20 years). We aligned participants by age from peak metacarpal length velocity. We assessed bone width (BW, mm); cortical thickness (CT, mm); medullary width (MW, mm); stress-strain index (SSI, mm³); and muscle cross-sectional area (MCSA, mm²).

RESULTS

From 12 to 20 years, the associations between metacarpal measures (BW, CT and SSI) and MCSA at the radius (males R² = 0.33-0.45; females R² = 0.12-0.20) were stronger than the tibia (males R² = 0.01-0.11; females R² = 0.007-0.04). In all groups, radial BW, CT and MW accrual rates were similar to those of the metacarpal, except in white females who had lower radial CT (0.04 mm/year) and greater radial MW (0.06 mm/year) accrual. In all groups, except for CT in white males, tibial BW and CT accrual rates were greater than at the metacarpal. Tibial MW (0.29-0.35 mm/year) increased significantly relative to metacarpal MW (- 0.07 to 0.06 mm/year) in males only. In all groups, except white females, SSI increased in each bone.

CONCLUSION

Irrespective of sex and ethnicity, metacarpal growth was similar to that of the non-weight-bearing radius but differed from that of the weight-bearing tibia. The local and systemic factors influencing site-specific differences require further investigation. Graphical abstract.

Fractures and bone health monitoring in boys with Duchenne muscular dystrophy managed within the Scottish Muscle Network

There are limited reports of radiologically confirmed fractures and bone health monitoring in with Duchenne muscular dystrophy. We performed a retrospective study of 91 boys, with a median age of 11.0 years, who are currently managed in Scotland with the aim to assess the frequency of radiologically confirmed fractures and report on bone health monitoring in relation to International Care Consensus Guidance. Of these boys, 59 (65%) were receiving glucocorticoid (GC) therapy and 23 (25%) had received previous treatment. Of those currently on GC, 37 (63%) had an assessment of bone mineral density and none had routine imaging for vertebral fractures during the study period. Of the 91 boys, 44 (48%) had sustained at least one symptomatic radiographically confirmed fracture. The probability of sustaining a first symptomatic fracture was 50% by 12.8 years old (95%CI: 12.1, 13.6). The most common sites for non-vertebral fracture were the femur and tibia. In this review of boys with DMD, almost half had sustained at least one radiologically confirmed symptomatic fracture. There is a need for standardized bone health monitoring in DMD that includes routine imaging of the spine to identify vertebral fractures, given the persistence of insult to the skeleton in these boys.

Indian girls have higher bone mineral content per unit of lean body than boys through puberty

Our aim is to describe changes in the muscle-bone unit assessed as a ratio of bone mineral content (BMC) to lean body mass (LBM) through puberty at total body and various skeletal sites in Indian boys and girls. A cross-sectional study was conducted (888 children, 480 boys, aged 5-17 years) in Pune, India. Pubertal staging was assessed. BMC, LBM and fat percentage at the arms, legs, android, gynoid and total body (less the head) were assessed by dual energy X-ray absorptiometry. The amount of BMC per unit LBM (BMC/LBM) was computed. Changes in mean BMC/LBM at 5 Tanner (pubertal) stages after adjustment for age and fat percentage were calculated. In boys, adjusted BMC/LBM was significantly higher with successive Tanner stages [legs (TS-II vs TS-I), android (TS-III vs TS-II, TS-IV vs TS-III) and gynoid region (TS-III vs TS-II and TS-II vs TS-I) (p < 0.05)]. In girls, adjusted BMC/LBM was significantly higher with successive Tanner stages at total body, legs and gynoid (TS-III vs TS-II; TS-II vs TS-I; TS-V vs TS-IV), arms (TS-I to TS-V) and android regions (TS-V vs TS-IV) (p < 0.05). Boys had significantly higher adjusted BMC/LBM than girls at earlier Tanner stages (TS-I to TS-III), whereas girls had significantly higher adjusted BMC/LBM than boys at later Tanner stages (TS-IV, TS-V) (p < 0.05). Indian boys and girls showed higher total and regional body, and age- and fat percentage-adjusted BMC/LBM with successive pubertal stages. Girls had higher BMC/LBM than boys which may possibly act as a reservoir for later demands of pregnancy and lactation.

Relationship between body mass, lean mass, fat mass, and limb bone cross-sectional geometry: Implications for estimating body mass and physique from the skeleton

OBJECTIVES

Estimating body mass from skeletal dimensions is widely practiced, but methods for estimating its components (lean and fat mass) are poorly developed. The ability to estimate these characteristics would offer new insights into the evolution of body composition and its variation relative to past and present health. This study investigates the potential of long bone cross-sectional properties as predictors of body, lean, and fat mass.

MATERIALS AND METHODS

Humerus, femur and tibia midshaft cross-sectional properties were measured by peripheral quantitative computed tomography in sample of young adult women (n = 105) characterized by a range of activity levels. Body composition was estimated from bioimpedance analysis.

RESULTS

Lean mass correlated most strongly with both upper and lower limb bone properties (r values up to 0.74), while fat mass showed weak correlations (r ≤ 0.29). Estimation equations generated from tibial midshaft properties indicated that lean mass could be estimated relatively reliably, with some improvement using logged data and including bone length in the models (minimum standard error of estimate = 8.9%). Body mass prediction was less reliable and fat mass only poorly predicted (standard errors of estimate ≥11.9% and >33%, respectively).

DISCUSSION

Lean mass can be predicted more reliably than body mass from limb bone cross-sectional properties. The results highlight the potential for studying evolutionary trends in lean mass from skeletal remains, and have implications for understanding the relationship between bone morphology and body mass or composition.

Proceedings of the 2017 Santa Fe Bone Symposium: Insights and Emerging Concepts in the Management of Osteoporosis

The 18th Annual Santa Fe Bone Symposium was held on August 4-5, 2017, in Santa Fe, New Mexico, USA. The symposium convenes health-care providers and clinical researchers to present and discuss clinical applications of recent advances in research of skeletal diseases. The program includes lectures, oral presentations by endocrinology fellows, case-based panel discussions, and breakout sessions on topics of interest, with emphasis on participation and interaction of all participants. Topics included the evaluation and treatment of adult survivors with pediatric bone diseases, risk assessment and management of atypical femur fractures, nonpharmacologic strategies in the care of osteoporosis, and skeletal effects of parathyroid hormone with opportunities for therapeutic intervention. Management of skeletal complications of rheumatic diseases was discussed. Insights into sequential and combined use of antiresorptive agents were presented. Individualization of patient treatment decisions when clinical practice guidelines may not be applicable was covered. Challenges and opportunities with osteoporosis drug development were discussed. There was an update on progress of Bone Health TeleECHO (Bone Health Extension for Community Healthcare Outcomes), a teleconferencing strategy for sharing knowledge and expanding capacity to deliver best-practice skeletal health care.

Metacarpal Growth During Adolescence in a Longitudinal South African Cohort

To monitor the drift of the periosteal and endocortical surfaces during metacarpal growth longitudinally, radiogrammetry was carried out on hand-wrist X-rays of 572 children from the Birth to Twenty Bone Health Cohort annually from ages 9 to 21 years. This is the largest collection of longitudinal X-rays in African children. The second metacarpal bone length, bone width, and medullary width were measured using digital vernier calipers on a total of 4730 X-rays. Superimposition by Translation and Rotation (SITAR) was used to obtain age at peak metacarpal length velocity (PLV). Bone width and medullary width were modeled using SITAR against both chronological age and age from PLV. In black and white females, tempo and velocity of metacarpal length growth was synchronized. Black males, however, attained PLV 7 months later than white males (p < 0.0001). Compared to white males, black males had a longer second metacarpal (p < 0.05), and greater bone width size (p < 0.02), tempo (p < 0.0009), and velocity (p < 0.0001). Medullary width growth velocity in black participants peaked 2 years prior to attainment of PLV and exceeded that of their white peers (p < 0.0001) in whom it peaked 6 to 12 months post-PLV attainment. Black adolescents therefore had wider bones with relatively thinner cortices and wider medullary cavities than their white peers. Ethnic and sex differences also occurred in the timing of medullary width contraction that accompanied expansion in bone width and cortical thickness. In black males, medullary width contraction commenced approximately 3 years later than in black females, whereas in white males this occurred a year later than in white females. The ethnic and sex differences in bone acquisition reported in this study may differentially affect bone mass in later life. © 2017 American Society for Bone and Mineral Research.

Mechanical, biochemical, and dietary determinants of the functional model of bone development of the radius in children and adolescents

This study examined the degree to which various mechanical, biochemical, and dietary factors are related to nonweight bearing bone properties in 172 healthy peri-pubertal children (age, 11.7 ± 2.0 years). Dominant radial speed of sound (rSOS) was measured by transaxial quantitative ultrasound at distal radius. Potential modulating factors included somatic maturity offset (years from age of peak height velocity), grip strength, forearm lean cross-sectional area (CSA), physical activity, nutritional intake, and amino-terminal cross-linking propeptide (NTx), reflecting bone resorption. In a hierarchical regression, grip strength adjusted for CSA was the second most important predictor of rSOS after the maturity offset (β = 0.22 and β = 0.33, respectively; R² = 0.16). When relative grip strength was added to the model the contribution of sex was no longer significant. Calcium intake was a significant predictor of rSOS only after NTx was accounted for in the model (β = 0.17, R² = 0.21). This may suggest that calcium's effects on the muscle-bone unit may be modulated through bone resorption. In the final model, relative grip strength together with maturity offset, dietary calcium, and NTx explained up to 21% of the variance in rSOS in this cohort of children. Therefore, during the peri-pubertal stage, size-adjusted forearm muscle strength is related to radial bone strength after controlling for maturity, with calcium intake having a potential indirect association through NTx.

Analysis of the functional muscle-bone unit of the forearm in patients with phenylketonuria by peripheral quantitative computed tomography

Bone disease in patients with phenylketonuria (PKU) is incompletely characterized. We therefore analyzed, in a cross-sectional study radius macroscopic bone architecture and forearm muscle size by peripheral quantitative computed tomography (pQCT) and muscle strength by hand dynamometry in a large cohort (n = 56) of adolescent and adult patients with PKU aged 26.0 ± 8.9 (range, 11.8-41.5) years. Data were compared with a reference population (n = 700) from the DONALD study using identical methodology. We observed a significant reduction of cortical thickness (z-score -1.01 ± 0.79), Strength-Strain Index (SSI) (z-score -0.81 ± 1.03), and total bone mineral density (BMD) of the distal radius (z-score -1.05 ± 1.00). Mean muscle cross-sectional area (z-score -0.98 ± 1.19) and muscle grip force (z-score -0.64 ± 1.26) were also significantly reduced, indicating an impaired muscular system as part of the clinical phenotype of PKU. SSI positively correlated (r = 0.53, P < 0.001) with the corresponding muscle cross-sectional area in the reference population; however, the regression line slope in PKU patients was less steep (P < 0.001), indicating that bone strength is not adequately adapted to muscle force. In conclusion, the radial bone in PKU patients is characterized by reduced bone strength in relation to muscular force, decreased cortical thickness, and impaired total BMD at the metaphyseal site. These alterations indicate a mixed bone defect in PKU, both of which are due to primary alterations of bone metabolism and to secondary alterations in response to neuromuscular abnormalities.

Peripheral quantitative computed tomography (pQCT) for the assessment of bone strength in most of bone affecting conditions in developmental age: a review

Peripheral quantitative computed tomography provides an automatical scan analysis of trabecular and cortical bone compartments, calculating not only their bone mineral density (BMD), but also bone geometrical parameters, such as marrow and cortical Cross-Sectional Area (CSA), Cortical Thickness (CoTh), both periosteal and endosteal circumference, as well as biomechanical parameters like Cross-Sectional Moment of Inertia (CSMI), a measure of bending, polar moment of inertia, indicating bone strength in torsion, and Strength Strain Index (SSI). Also CSA of muscle and fat can be extracted. Muscles, which are thought to stimulate bones to adapt their geometry and mineral content, are determinant to preserve or increase bone strength; thus, pQCT provides an evaluation of the functional 'muscle-bone unit', defined as BMC/muscle CSA ratio. This functional approach to bone densitometry can establish if bone strength is normally adapted to the muscle force, and if muscle force is adequate for body size, providing more detailed insights to targeted strategies for the prevention and treatment of bone fragility. The present paper offers an extensive review of technical features of pQCT and its possible clinical application in the diagnostic of bone status as well as in the monitoring of the skeleton's health follow-up.

Trabecular and cortical bone deficits are present in children and adolescents with cystic fibrosis

Osteopenia and increased fracture rates are well-recognized in adults with CF, but neither the specific contributions of cortical and trabecular bone deficits to bone fragility nor their presence in youth with CF are well-characterized. This study sought to characterize cortical and trabecular volumetric bone mineral density (vBMD), geometry, and biomechanical competence in children with CF and determine their relationship to growth, body composition, and disease severity. Peripheral quantitative computerized tomography (pQCT) measures of total, cortical, and trabecular vBMD, cortical, muscle, and fat cross-sectional areas (CSA), periosteal and endosteal circumferences, and the polar unweighted section modulus (Zp) of the tibia were converted to age- and tibial length-adjusted Z-scores in 97 CF and 199 healthy children (aged 8-21y). Effects of body composition and pulmonary function (forced expiratory volume in 1s, FEV1) upon pQCT outcomes were determined using linear regression. Children with CF (FEV1%-predicted: 84.4+19.7) had lower weight-, height-, BMI-, and whole body lean mass (LBM)-Z and tibial length. Females with CF had lower (p<0.01) total and trabecular vBMD; cortical, muscle, and fat CSA; Zp and periosteal circumference than females in the healthy reference group. These bone differences persisted after adjustment for BMI-Z and to a great extent following adjustment for muscle CSA. Males with CF had lower (p<0.01) cortical, muscle, and fat CSA and their trabecular vBMD deficit approached significance (p=0.069). Deficits were attenuated by adjustment for BMI-Z and to a greater extent adjustment for muscle CSA-Z. The relationship between FEV1%-predicted and pQCT outcomes persisted only in males following adjustment for age and BMI-Z. The CF cohort had lower tibial muscle CSA than expected for their LBM. In this relatively healthy, young CF cohort, deficits in trabecular and multiple cortical bone parameters were present. In females, deficits were greater at older ages and were not fully explained by alterations in body composition. In males worsening pulmonary function was associated with greater deficits that was not explained by increasing age or compromised nutritional status. The occurrence of these differences in CF youth highlights the importance of instituting measures to optimize peak bone mass early in the course of CF.

Muscle volume is related to trabecular and cortical bone architecture in typically developing children

INTRODUCTION

Muscle is strongly related to cortical bone architecture in children; however, the relationship between muscle volume and trabecular bone architecture is poorly studied. The aim of this study was to determine if muscle volume is related to trabecular bone architecture in children and if the relationship is different than the relationship between muscle volume and cortical bone architecture.

MATERIALS AND METHODS

Forty typically developing children (20 boys and 20 girls; 6 to 12y) were included in the study. Measures of trabecular bone architecture [i.e., apparent trabecular bone volume to total volume (appBV/TV), trabecular number (appTb.N), trabecular thickness (appTb.Th) and trabecular separation (appTb.Sp)] in the distal femur, cortical bone architecture [cortical volume, total volume, section modulus (Z) and polar moment of inertia (J)] in the midfemur, muscle volume in the midthigh and femur length were assessed using magnetic resonance imaging. Total physical activity and moderate-to-vigorous physical activity were assessed using an accelerometer-based activity monitor worn around the waist for four days. Calcium intake was assessed using diet records. Relationships among the measures were tested using multiple linear regression analysis.

RESULTS

Muscle volume was moderately-to-strongly related to measures of trabecular bone architecture [appBV/TV (r=0.81), appTb.N (r=0.53), appTb.Th (r=0.67), appTb.Sp (r=-0.71); all p<0.001] but more strongly related to measures of cortical bone architecture [cortical volume (r=0.96), total volume (r=0.94), Z (r=0.94) and J (r=0.92; all p<0.001)]. Similar relationships were observed between femur length and measures of trabecular (p<0.01) and cortical (p<0.001) bone architecture. Sex, physical activity and calcium intake were not related to any measure of bone architecture (p>0.05). Because muscle volume and femur length were strongly related (r=0.91, p<0.001), muscle volume was scaled for femur length (muscle volume/femur length(2.77)). When muscle volume/femur length(2.77) was included in a regression model with femur length, sex, physical activity and calcium intake, muscle volume/femur length(2.77) was a significant predictor of appBV/TV, appTb.Th and appTb.Sp (partial r=0.44 to 0.49, p<0.05) and all measures of cortical bone architecture (partial r=0.47 to 0.54; p<0.01).

CONCLUSIONS

The findings suggest that muscle volume in the midthigh is related to trabecular bone architecture in the distal femur of typically developing children. The relationship is weaker than the relationship between muscle volume in the midthigh and cortical bone architecture in the midfemur, but the discrepancy is driven, in large part, by the greater dependence of cortical bone architecture measures on femur length.

Muscle Density and Bone Quality of the Distal Lower Extremity Among Individuals with Chronic Spinal Cord Injury

BACKGROUND

Understanding the related fates of muscle density and bone quality after chronic spinal cord injury (SCI) is an important initial step in determining endocrine-metabolic risk.

OBJECTIVE

To examine the associations between muscle density and indices of bone quality at the distal lower extremity of adults with chronic SCI.

METHODS

A secondary data analysis was conducted in 70 adults with chronic SCI (C2-T12; American Spinal Injury Association Impairment Scale [AIS] A-D; ≥2 years post injury). Muscle density and cross-sectional area (CSA) and bone quality indices (trabecular bone mineral density [TbBMD] at the distal tibia [4% site] and cortical thickness [CtTh], cortical area [CtAr], cortical BMD [CtBMD], and polar moment of inertia [PMI] at the tibial shaft [66% site]) were measured using peripheral quantitative computed tomography. Calf lower extremity motor score (cLEMS) was used as a clinical measure of muscle function. Multivariable linear regression analyses were performed to determine the strength of the muscle-bone associations after adjusting for confounding variables (sex, impairment severity [AIS A/B vs AIS C/D], duration of injury, and wheelchair use).

RESULTS

Muscle density was positively associated with TbBMD (b = 0.85 [0.04, 1.66]), CtTh (b = 0.02 [0.001, 0.034]), and CtBMD (b = 1.70 [0.71, 2.69]) (P < .05). Muscle CSA was most strongly associated with CtAr (b = 2.50 [0.12, 4.88]) and PMI (b = 731.8 [161.7, 1301.9]) (P < .05), whereas cLEMS was most strongly associated with TbBMD (b = 7.69 [4.63, 10.76]) (P < .001).

CONCLUSIONS

Muscle density and function were most strongly associated with TbBMD at the distal tibia in adults with chronic SCI, whereas muscle size was most strongly associated with bone size and geometry at the tibial shaft.

Ontogeny of the male femur: Geometric morphometric analysis applied to a contemporary Spanish population

OBJECTIVE

To describe the morphological changes of the male femur during the adolescent growth spurt and to compare the pattern obtained with that reported previously for females.

MATERIAL AND METHODS

Two hundred and forty males from a Spanish population aged between 9 and 16 years were analysed, based on telemetries. Size and shape variation of the femur was quantified by 22 2D-landmarks and analysed using geometric morphometric methods. Likewise, the variation of neck-shaft and bicondylar angles were also determined and evaluated by Student's t-test. Sexual differences were analysed by comparing results here obtained on boys with those corresponding to girls reported in a previous study.

RESULTS

In males, both size and shape varied significantly with age, with males having larger dimensions than females. In general terms, these changes are generally characterised by an increase in robustness of the femur and shape modifications in the epiphyses. During growth, the neck-shaft angle decreases and the size of the greater and lesser trochanters increase. A significant increase of distal epiphyseal dimensions was recorded, mainly in the medial condyle. The angular remodeling of both the neck and the bicondylar regions of the male femur continues until 16 and 15 years, respectively. Female and male femur each followed divergent growth trajectories. Males showed a greater variability in neck-shaft and bicondylar angles than females.

DISCUSSION

The timing, morphology and growth trajectories provided on the femur during development can be very helpful in anthropological, paleoanthropological and evolution studies.

Interaction between bone and muscle in older persons with mobility limitations

Aging is associated with a progressive loss of bone-muscle mass and strength. When the decline in mass and strength reaches critical thresholds associated with adverse health outcomes, they are operationally considered geriatric conditions and named, respectively, osteoporosis and sarcopenia. Osteoporosis and sarcopenia share many of the same risk factors and both directly or indirectly cause higher risk of mobility limitations, falls, fractures and disability in activities of daily living. This is not surprising since bones adapt their morphology and strength to the long-term loads exerted by muscle during anti-gravitational and physical activities. Non-mechanical systemic and local factors also modulate the mechanostat effect of muscle on bone by affecting the bidirectional osteocyte-muscle crosstalk, but the specific pathways that regulate these homeostatic mechanisms are not fully understood. More research is required to reach a consensus on cut points in bone and muscle parameters that identify individuals at high risk for adverse health outcomes, including falls, fractures and disability. A better understanding of the muscle-bone physiological interaction may help to develop preventive strategies that reduce the burden of musculoskeletal diseases, the consequent disability in older persons and to limit the financial burden associated with such conditions. In this review, we summarize age-related bone-muscle changes focusing on the biomechanical and homeostatic mechanisms that explain bone-muscle interaction and we speculate about possible pathological events that occur when these mechanisms become impaired. We also report some recent definitions of osteoporosis and sarcopenia that have emerged in the literature and their implications in clinical practice. Finally, we outline the current evidence for the efficacy of available anti-osteoporotic and proposed antisarcopenic interventions in older persons.

An in-school exercise intervention to enhance bone and reduce fat in girls: the CAPO Kids trial

The CAPO Kids trial was a 9-mo, controlled, school-based intervention to examine the effects of a novel, brief, high intensity exercise regime on indices of musculoskeletal and metabolic health in pre- and early-pubertal girls.

METHODS

A total of 151 pre- and early-pubertal girls (10.6±0.6years), recruited from two different schools consented to participate; 76 in the exercise group (EX) and 75 in the control group (CON). EX performed 10min bouts of thrice-weekly jumping plus capoeira (a Brazilian sport that combines martial art with dance), along with usual physical education (PE) activities. CON continued usual PE alone. Maturity, weight, height, waist circumference, resting heart rate and blood pressure, maximal vertical jump, and aerobic capacity were determined using standard clinical and field measures. Calcaneal broadband ultrasound attenuation (BUA) and stiffness index (SI) were determined from quantitative ultrasonometry. A subsample of children also underwent DXA and pQCT measures. Prior physical activity participation and daily calcium consumption were determined from validated instruments.

RESULTS

EX girls improved BUA more than CON (+4.5% vs. +1.4%, p=0.019). Resting heart rate (-7.2% vs. -1.8%, p<0.01), maximal vertical jump (+13.4% vs. -1.2%, p<0.001), estimated maximal oxygen consumption (+10.6% vs. +1.0%, p<0.001), and waist circumference (+2.7% vs. +5.6%, p<0.001) also improved more for EX than CON.

CONCLUSION

Ten minutes of high intensity exercise (capoeira and jumping) three times a week in the primary school setting enhances musculoskeletal and metabolic outcomes in pre- and early-pubertal girls without disrupting the academic schedule. The programme, amenable to broad-scale school implementation, would confer meaningful public health benefits.

Comparison of bone mass and quality determinants in adolescents and young adults with juvenile systemic lupus erythematosus (JSLE) and juvenile idiopathic arthritis (JIA)

BACKGROUND

Few prospective data have been published on the comparison of bone density and quality in homogeneous groups of patients with juvenile systemic lupus erythematosus (JSLE) and juvenile idiopathic arthritis (JIA).

OBJECTIVE AND HYPOTHESIS

The objective of this study is to perform a longitudinal evaluation of the prevalence and the characteristics of bone mass and quality and to evaluate the differences on the bone parameters, using DXA, pQCT and QUS.

POPULATION AND/OR METHODS

Forty-three JSLE patients (35 females, 8 males, median age 18.8, range 14.0-34.1 years) have been studied with DXA, pQCT and QUS scans and compared with 138 JIA patients (112 females, 26 males, median age 18.9, range 13.4-33.2 years), and 79 controls (59 females, 20 males; median age 19.3, range 13.5-36.5 years). Of these, 39 patients (32 females and 7 males, median age 20.3, range 16.6-36.8 years) with JSLE were followed longitudinally and compared with 131 patients (108 females, 23 males median age 20.7, range 15.8-37.1 years) with JIA and 63 controls (48 females, 15 males; median age 21.9, range 15.5-38.3 years).

RESULTS

JSLE patients have a higher bone cortical density (CrtBMD) than controls and JIA patients (p < 0.005). However, JSLE and JIA patients have a significantly reduced bone trabecular density (TrbBMD) compared to controls (p < 0.0001), with no differences between JSLE and JIA. In addition, JIA patients show a significantly reduced muscle area (MuscleCSA) compared to JSLE and controls (p < 0.001). Conversely, fat area (FatCSA) is significantly increased both in JIA and JSLE patients when compared to controls (p < 0.001), with no differences between the JSLE and JIA groups. Analogous results are observed in the polar resistance to stress (SSIp). On longitudinal evaluation, contrary to CrtBMD, the difference between BMAD SDS, TrbBMD, MuscleCSA and FatCSA remains unchanged; in JSLE patients, SSIp is stable in comparison to JIA and controls without any difference between the two groups.

CONCLUSIONS

The evaluation of bone density and structure parameters in JSLE patients highlights significant differences compared with JIA patients and controls. These data might indicate a different pathogenesis of bone damage in the two entities, and suggest a different diagnostic and therapeutic approach to improve the peak bone mass.

Ontogeny of the female femur: geometric morphometric analysis applied on current living individuals of a Spanish population

In this study we describe the development of the female femur based on the analysis of high-resolution radiographic images by means of geometric morphometrics, while assessing the usefulness of this method in these kinds of studies. The material analysed consisted of digital images in DICOM format (telemetries), corresponding to 184 left femora in anterior view, obtained from the database of the Hospital Sant Joan de Déu of Barcelona (Spain). Bones analysed corresponded to individuals from 9 to 14 years old. Size and shape variation of the entire femur was quantified by 22 two-dimensional landmarks. Landmark digitisation errors were assessed using Procrustes anova test. Centroid size (CS) variation with age was evaluated by an anova test. Shape variation was assessed by principal component analysis. A mancova test between the first five principal components and age, using the CS as covariable, was applied. Results indicated that both size and shape vary significantly with age. Several age-related shape changes remained significant after removing the allometric effect. In general, an increase in the robustness of the bone and noticeable phenotypic changes in certain areas of the femur were observed. During growth in the proximal region of the femur, the collo-diaphyseal angle decreases, the neck of the femur widens and the fovea moves to a lower position, standing more in line with the plane of the neck. Likewise, the size of the greater and lesser trochanters increase. In the distal region, a significant increase of epiphyseal dimensions was recorded, mainly in the medial condyle. The angular remodelling of the neck and the bicondylar region of the femur in females continues until 13 years old. The information provided in the present study increases our knowledge on the timing and morphology of the femur during development, and in particular the morphology of the different femoral ossification centres during development.

Bone microarchitecture and strength of the radius and tibia in a reference population of young adults: an HR-pQCT study

Within a normative youth cohort (16-29 years) bone parameters for males and females remained stable at the radius. At the tibia, a peak was observed for females at 16-19 years, with bone density and strength decreasing by 29 years.

PURPOSE

To determine if bone microstructural and strength parameters identified by high-resolution peripheral quantitative computed tomography (HR-pQCT) and finite element analysis (FEA) at the distal radius and tibia, peak within the age range of this youth cohort, and whether the timing of the peaks differ based on sex or skeletal site.

METHODS

We recruited 251 participants (158 female; 16 to 29 years), grouping them into 5-year age brackets (16-19; 20-24; 25-29 years) assessing microstructural and strength parameters with HR-pQCT and FEA.

RESULTS

HR-pQCT assessment of males and females (age-matched groups) showed males had higher total area and BMD, trabecular BMD and trabecular number (radius only) cortical thickness and porosity, and failure load, but lower cortical BMD (p < 0.05). Within sex, microstructural and strength parameters remained stable for males, but in females they appeared to peak at 16-19 years at the tibia. Tibia bone strength and trabecular BMD were highest in females 16-19 years (p < 0.05), and tibia cortical porosity was lowest in females 16-19 years (p < 0.001). With the exception of an age-related increase in cortical BMD, all other parameters were stable between 16 and 29 years at the radius for both males and females. We found no peak values for males or females at the radius. At the tibia, a peak was observed for females 16-19 years.

CONCLUSION

These data provide a population-based assessment of bone microstructural and strength parameters from HR-pQCT and FEA in a youth cohort, showing clear differences in bone quality dependent on sex and skeletal site.

Pilot study for reconstruction of soft tissues: muscle cross-sectional area of the forearm estimated from cortical bone for a Neolithic sample

On a basis of a method for muscle cross-sectional area estimation from cortical bone area that was previously developed (Slizewski et al. Anat Rec 2013; 296:1695-1707), we reconstructed muscle cross-sectional area at 65% of radius length for a sample of Neolithic human remains from the Linear Pottery Culture (ca. 5,700-4,900 years BC). Muscle cross-sectional area estimations for the Neolithic sample were compared to in vivo measurements from a recent human sample. Results demonstrate that the Neolithic individuals had larger muscle cross-sectional area relative to radius length than the contemporary humans and that their forearms were more muscular and robust. We also found significant differences in relative muscle cross-sectional area between Neolithic and recent children that indicate different levels of physical stress and isometric activities. Our results fit into the framework of studies previously published about the sample and the Linear Pottery Culture. Therefore, the new approach was successfully applied to an archaeological sample for the first time here. Results of our pilot study indicate that muscle cross-sectional area estimation could in the future supplement other anthropological methods currently in use for the analysis of postcranial remains.

Dual-energy X-ray absorptiometry interpretation and reporting in children and adolescents: the revised 2013 ISCD Pediatric Official Positions

The International Society for Clinical Densitometry Official Revised Positions on reporting of densitometry results in children represent current expert recommendations to assist health care providers determine which skeletal sites should be measured, which, if any, adjustments should be made, reference databases to be used, and the elements to include in a dual-energy X-ray absorptiometry report. The recommended scanning sites remain the total body less head and the posterior-anterior spine. Other sites such as the proximal femur, lateral distal femur, lateral vertebral assessment, and forearm are discussed but are only recommended for specific pediatric populations. Different methods of interpreting bone density scans in children with short stature or growth delay are presented. The use of bone mineral apparent density and height-adjusted Z-scores are recommended as suitable size adjustment techniques. The validity of appropriate reference databases and technical considerations to consider when upgrading software and hardware remain unchanged. Updated reference data sets for all contemporary bone densitometers are listed. The inclusion of relevant demographic and health information, technical details of the scan, Z-scores, and the wording "low bone mass or bone density" for Z-scores less than or equal to -2.0 standard deviation are still recommended for clinical practice. The rationale and evidence for the development of the Official Positions are provided. Changes in the grading of quality of evidence, strength of recommendation, and worldwide applicability represent a change in current evidence and/or differences in opinion of the expert panelists used to validate the position statements for the 2013 Position Development Conference.

Pathological fractures in paediatric patients with inflammatory bowel disease

Paediatric inflammatory bowel disease (IBD), especially Crohn's disease (CD), is commonly associated with poor skeletal health, related to the direct effects of chronic inflammation, prolonged use of glucocorticoid (GC), poor nutrition, delayed puberty and low muscle mass. Low bone mineral density is commonly reported, although the prevalence of long bone fractures may not be increased in these patients. Emerging evidence however suggests that there may be an increased risk of vertebral fractures (VFs) in this group. VFs presenting at diagnosis of paediatric CD, prior to any GC exposure, have been reported, highlighting the deleterious effect of inflammation on skeletal health. This paper reviews the published literature on pathophysiology of skeletal morbidity and fractures in paediatric IBD, illustrated with a new case report of multiple VFs in a prepubertal girl with CD, soon after diagnosis, who received minimal amounts of oral GC. Optimising control of disease, addressing vitamin D deficiency, encouraging physical activity and ensuring normal growth and pubertal progression are paramount to management of bone health in these patients. Despite the lack of evidence, there may be a place for bisphosphonate treatment, especially in the presence of symptomatic pathological fractures, but this requires close monitoring by clinicians with expertise in paediatric bone health.

CONCLUSION

Chronic inflammation mediated by pro-inflammatory cytokines may have adverse effects on skeletal health in paediatric patients with IBD. The risk of vertebral fractures may be increased, even without exposure to glucocorticoid. Clinical monitoring of these patients requires careful attention to the various factors that impact on bone health.

Prevention of Osteoporosis and Bone Fragility

The importance of optimal bone growth in childhood and adolescence has been recognized as one of the key strategies in osteoporotic fracture prevention. Low birth size, poor childhood growth, and low peak bone mass at the cessation of growth have been linked to the later risk of osteoporosis and hip fracture. Formerly, the focus was merely on maximizing bone mineral accrual because a high peak bone mineral mass may prevent attainment of a critical “fracture threshold” associated with age-related bone loss and osteoporosis. More recently, the focus has shifted away from bone mineral accrual—as measured by dual-energy X-ray absorptiometry (DXA)—toward the optimization of bone strength. This is partly because of the advances in bone imaging that have enabled estimation of bone strength beyond bone mass. In this review, we briefly describe long-bone growth and structural development and our abilities to assess bone properties by medical imaging tools. In addition, we summarize the evidence of factors contributing to skeletal growth, bone fragility, and the development of strong, healthy bones.

Muscle area estimation from cortical bone

This article investigates the relationship between the cortical bone of the radius and the muscle area of the forearm. The aim of this study was to develop a method for muscle area estimation from cortical bone area at 65% of radius length where the muscle area at the forearm is largest. Muscle area and cortical area were measured directly in vivo by peripheral Quantitative Computed Tomography (pQCT). We found significant correlations between muscle area and cortical area (r = 0.881) in the forearm that are in line with previous studies. We have set up a regression model by testing relevant parameters such as age, sex, forearm length, and stature that were all highly correlated to muscle area. The influence of age and sex on the proportion of muscle area to cortical area is strong and potentially related to the effects of testosterone and estrogen on the muscle-bone-unit. Muscle area estimation from cortical bone is possible with a Percent Standard Error of Estimate (%SEE) ranging from 12.03% to 14.83%, depending on the parameters available and the age and sex of the individual. Muscle area estimation from cortical bone can provide new information for the study of skeletal and/or fossil human remains.

Cortical bone thickness can adapt locally to muscular loading while changing with age

Mechanical loading of muscle action is concentrated at muscle attachment sites; thus there may be a potential for site-specific variation in cortical bone thickness. Humeri from an early 20th-century Finnish (Helsinki) and two medieval English (Newcastle, Blackgate and York, Barbican) populations were subjected to pQCT scanning to calculate site-specific cross-sectional cortical bone area (CA) for four locations and to measure cortical thickness at muscle attachment sites and non-attachment sites. We found that CA at 80% of humerus length was significantly reduced compared to more distal cross-sections, which can be due to reduced stresses at the proximal shaft. The principal direction of loading at 80% humerus length was towards mediolateral plane, likely due to fixing the humerus close to the torso. At 35% the main direction of loading was towards anteroposterior plane, reflecting elbow flexing forces. The principal direction of loading varied between populations, sides and sexes at 50% humerus length due to preference between elbow and shoulder joint; thus this location might be useful when trying to infer differences in activity. These changes are likely due to overall shaft adaptation to forces acting at the humerus. In addition, we found a potential for site-specific variation in cortical thickness; cortical bone at muscle attachment sites was significantly thicker compared to non-attachment sites. Lastly, CA at 35% of humerus length and cortical thickness at non-attachment sites decreased with age. These results underline the importance of muscle loading for bone mass preservation as well as indicate that a site-specific variation of bone mass is possible.

Site-specific variance in radius and tibia bone strength as determined by muscle size and body mass

PURPOSE

To investigate the predictive ability of muscle cross-sectional area (MCSA) and body mass on bone mineral content, compressive bone strength index (BSIc), and the polar stress-strain index (SSIp) of the forearms and lower legs of middle-aged adults.

METHODS

A total of 53 healthy adults (37 male, 16 female; mean age 50.4; SD 2.1 y) were scanned with peripheral quantitative computed tomography (pQCT) to measure radius and tibia total and cortical bone mineral content, BSIc, SSIp, and forearm and lower-leg MCSA (BSIc: 4% distal; SSIp and MCSA at 65% and 66% radius and tibia shaft sites, respectively). Multiple regression models adjusted for sex and height were used to assess the relative variance in radius or tibia bone outcomes predicted by body mass and/or forearm or lower-leg MCSA.

RESULTS

Forearm MCSA independently predicted total bone-mineral content, BSIc, and SSIp in radius (r partial=0.59, 0.56, 0.42). Body mass was a negative predictor of radius BSIc (r partial=-0.32) and did not predict other radius outcomes when both body mass and MCSA were forced in the models. In the lower leg shaft, MCSA, and body mass predicted bone content and strength similarly when independently added to the models with sex and height.

CONCLUSIONS

Forearm MCSA was a dominant predictor of radius bone content and estimated strength. In the tibia, both body mass and lower-leg MCSA contributed to predicting bone content and estimated strength.

A family-centered lifestyle intervention to improve body composition and bone mass in overweight and obese children 6 through 8 years: a randomized controlled trial study protocol

BACKGROUND

Childhood obesity gives rise to health complications including impaired musculoskeletal development that associates with increased risk of fractures. Prevention and treatment programs should focus on nutrition education, increasing physical activity (PA), reducing sedentary behaviours, and should monitor bone mass as a component of body composition. To ensure lifestyle changes are sustained in the home environment, programs need to be family-centered. To date, no study has reported on a family-centered lifestyle intervention for obese children that aims to not only ameliorate adiposity, but also support increases in bone and lean muscle mass. Furthermore, it is unknown if programs of such nature can also favorably change eating and activity behaviors. The aim of this study is to determine the effects of a 1 y family-centered lifestyle intervention, focused on both nutrient dense foods including increased intakes of milk and alternatives, plus total and weight-bearing PA, on body composition and bone mass in overweight or obese children.

METHODS/DESIGN

The study design is a randomized controlled trial for overweight or obese children (6-8 y). Participants are randomized to control, standard treatment (StTx) or modified treatment (ModTx). This study is family-centred and includes individualized counselling sessions on nutrition, PA and sedentary behaviors occurring 4 weeks after baseline for 5 months, then at the end of month 8. The control group receives counselling at the end of the study. All groups are measured at baseline and every 3 months for the primary outcome of changes in body mass index Z-scores. At each visit blood is drawn and children complete a researcher-administered behavior questionnaire and muscle function testing. Changes from baseline to 12 months in body fat (% and mass), waist circumference, lean body mass, bone (mineral content, mineral density, size and volumetric density), dietary intake, self-reported PA and sedentary behaviour are examined.

DISCUSSION

This family-centered theory-based study permits for biochemical and physiological assessments. This trial will assess the effectiveness of the intervention at changing lifestyle behaviours by decreasing adiposity while enhancing lean and bone mass. If successful, the intervention proposed offers new insights for the management or treatment of childhood obesity.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01290016.

Mid-thigh cortical bone structural parameters, muscle mass and strength, and association with lower limb fractures in older men and women (AGES-Reykjavik Study)

In a cross-sectional study we investigated the relationship between muscle and bone parameters in the mid-thigh in older people using data from a single axial computed tomographic section through the mid-thigh. Additionally, we studied the association of these variables with incident low-trauma lower limb fractures. A total of 3,762 older individuals (1,838 men and 1,924 women), aged 66-96 years, participants in the AGES-Reykjavik study, were studied. The total cross-sectional muscular area and knee extensor strength declined with age similarly in both sexes. Muscle parameters correlated most strongly with cortical area and total shaft area (adjusted for age, height, and weight) but explained <10 % of variability in those bone parameters. The increment in medullary area (MA) and buckling ratio (BR) with age was almost fourfold greater in women than men. The association between MA and muscle parameters was nonsignificant. During a median follow-up of 5.3 years, 113 women and 66 men sustained incident lower limb fractures. Small muscular area, low knee extensor strength, large MA, low cortical thickness, and high BR were significantly associated with fractures in both sexes. Our results show that bone and muscle loss proceed at different rates and with different gender patterns.

Modifiable risk factors associated with bone deficits in childhood cancer survivors

BACKGROUND

To determine the prevalence and severity of bone deficits in a cohort of childhood cancer survivors (CCS) compared to a healthy sibling control group, and the modifiable factors associated with bone deficits in CCS.

METHODS

Cross-sectional study of bone health in 319 CCS and 208 healthy sibling controls. Bone mineral density (BMD) was measured by dual-energy x-ray absorptiometry (DXA). Generalized estimating equations were used to compare measures between CCS and controls. Among CCS, multivariable logistic regression was used to evaluate odds ratios for BMD Z-score ≤ -1.

RESULTS

All subjects were younger than 18 years of age. Average time since treatment was 10.1 years (range 4.3 - 17.8 years). CCS were 3.3 times more likely to have whole body BMD Z-score ≤ -1 than controls (95% CI: 1.4-7.8; p = 0.007) and 1.7 times more likely to have lumbar spine BMD Z-score ≤ -1 than controls (95% CI: 1.0-2.7; p = 0.03). Among CCS, hypogonadism, lower lean body mass, higher daily television/computer screen time, lower physical activity, and higher inflammatory marker IL-6, increased the odds of having a BMD Z-score ≤ -1.

CONCLUSIONS

CCS, less than 18 years of age, have bone deficits compared to a healthy control group. Sedentary lifestyle and inflammation may play a role in bone deficits in CCS. Counseling CCS and their caretakers on decreasing television/computer screen time and increasing activity may improve bone health.

Cross sectional properties of the human radial tuberosity

This study examines the cross sectional shape and biomechanical properties of the radial bone shaft at mid-radial tuberosity (RT) musculoskeletal marker (MSM). This information will provide insight into factors affecting bone modelling at muscle insertions. Radial shaft cross-sectional properties at radial tuberosity area (RTA) have not been previously studied. The material consists of 54 male skeletons derived from autopsies performed during the 1920s and 1930s and housed at the Central Natural History Museum, University of Helsinki. The age, sex and occupation of these individuals are known. We applied a pQCT (peripheral quantitative computed tomography) scan on the mid-site of the radial tuberosity to investigate the cross-sectional shape, the bone mineral density (BMD) and biomechanical properties. Our results indicate that bone modelling does not produce increased wall thickness or BMD at the RT site. Additionally we noticed that aging and physical activity affect the biomechanics of the RT and that the bone distribution at mid-RT is adapted to accommodate the biceps brachii muscle pull. We also found a clear association between RTA and biomechanical properties of mid-RT cross section.

Comparisons of trabecular and cortical bone in late adolescent black and white females

Few childhood studies have investigated racial differences in volumetric bone mineral density (vBMD), bone geometry, and bone strength indices measured by three-dimensional bone imaging. The purpose of this study was to compare trabecular and cortical bone parameters at the radius and tibia between late adolescent white and black females using peripheral quantitative computed tomography (QCT). White (n = 25) and black females (n = 25), 18-19 years of age, were pair-matched for age, height, and fat-free soft tissue mass. Peripheral QCT scans were obtained at the 4% (trabecular bone), 20% (cortical bone), and 66% [muscle cross-sectional area (CSA)] sites from the distal metaphyses. Bone strength was determined from vBMD and bone geometry to calculate bone strength index (BSI; trabecular site) and polar strength-strain index (SSI; cortical site). Radial SSI was not different between groups; however, blacks had greater radial BSI (P = 0.02) than whites. After adjustment for the longer forearm in blacks, the greater radial BSI in blacks no longer remained. At the tibia, blacks versus whites had greater bone strength at the trabecular and cortical bone sites (BSI, P = 0.03; SSI, P = 0.04, respectively). When controlling for differences in tibial length and muscle CSA, the higher estimates of bone strength persisted in blacks versus whites (BSI, P = 0.01; SSI, P = 0.02). Our data suggest that when differences in body size are considered, late adolescent black versus white females have a stronger bone profile, due to greater bone geometry and vBMD, at the trabecular and cortical regions of the tibia but not at the radius.

The muscle-bone unit of peripheral and central skeletal sites in children and young adults

Changes and gender differences in the muscle bone unit at different skeletal sites were investigated during pubertal development. Females accrued greater BMC in relation to muscle compared to males; these gender differences were greater after adjustment for height and regional fat mass.

PURPOSE

To describe changes and gender differences in the muscle-bone unit at different skeletal sites during pubertal development.

METHODS

Four hundred forty-two children aged 5-18 years were studied. Measurements of bone mineral content (BMC), lean mass (LM) and fat mass of the whole body (WB), legs, arms and lumbar spine were obtained from dual-energy X-ray absorptiometry. Peripheral quantitative computed tomography was used to measure BMC of the radius diaphysis and cross-sectional muscle area (CSMA) of the mid-forearm. These measurements were used to describe differences between, and within, genders at each pubertal stage in BMC accrual relative to muscle, both before and after adjustment for height, regional fat and muscle at central and peripheral skeletal sites.

RESULTS

In males, there were significant increases in adjusted WB and leg BMC at the end of pubertal development. Unadjusted and adjusted lumbar spine BMC increased at the onset of, and at the end, of puberty. Radius BMC increased at most pubertal stages. In females, there were increases in unadjusted and adjusted whole body BMC at late puberty, in leg BMC at the onset of puberty and at pubertal stage four. Unadjusted arm BMC increased at most pubertal stages; however, after adjustment, an increase occurred at pubertal stage four. Both adjusted and unadjusted lumbar spine BMC increased at pubertal stage four. Unadjusted radius BMC increased at most pubertal stages. Females had greater BMC at all skeletal sites, compared to males, except at the radius, where adjusted BMC was greater in males at pubertal stage four.

CONCLUSIONS

Males and females accrue more BMC in relation to lean mass at multiple skeletal sites as puberty proceeds. Females accrue more BMC in relation to lean mass, in comparison to males, at most skeletal sites.