Low volumetric BMD is linked to upper-limb fracture in pubertal girls and persists into adulthood: a seven-year cohort study

A Comparative Study of Bone-Health and Associated Factors in Healthy Indian Adolescents and Young Women

Introduction

Adolescence is a critical period for the accrual of bone mass. However, few studies have assessed the bone geometry in slum-dwelling girls/young women. We thus conducted this study: (1) to assess bone health in Indian adolescent girls and young women residing in slum vs nonslum (NS) areas and (2) to identify factors associated with poor bone health.

Methods

This cross-sectional case-control study was performed on 110 apparently healthy unmarried, nonpregnant, nonlactating, postmenarchal adolescent girls and young women aged 11 to 24 years residing in urban slums with the same number of age-matched controls from NS areas. Anthropometric, dietary, physical-activity and bone-health parameters (using dual-energy X-ray absorptiometry and peripheral quantitative computed tomography-DXA and pQCT-respectively) were evaluated using standard protocols. A P value of < 0.05 was considered statistically significant.

Results

Slum girls were significantly shorter and lighter and had lower dietary intakes of calcium and protein after adjusting for total daily calorie intake than NS girls (P < 0.05). Areal bone-mineral density (BMD) at lumber spine (0.940 ± 0.13 vs1.042 ± 0.15 g/cm2), femur and total body (less-head), bone-mineral apparent density adjusted for volume at the lumbar spine (0.295 ± 0.04 vs 0.319 ± 0.04 g/cm3) and height-adjusted bone density at femur (0.862 ± 0.011 vs 0.905 ± 0.011 g/cm2) were significantly lower in slum dwelling participants as compared to their NS counterparts (P < 0.05). After adjusting for confounders like sunlight exposure, anthropometric parameters and dietary calcium intake, area of dwelling was still a significant factor for the difference in BMD.

Conclusions

The potential determinants of poor bone density and geometry in girls and young women residing in slums include residential location, dietary habits, and physical activity levels. Despite adjustments for confounding factors, differences in bone health between those in slum and nonslum areas suggest adaptations developed over generations of deprivation in these individuals, necessitating urgent intervention.

Decreased bone mass in adolescents with bone fragility fracture but not in young children: a case-control study

Background

The incidence of distal forearm fracture due to minimal/moderate trauma shows a bimodal distribution for age at event, with one peak occurring during early adolescence, in both boys and girls and the other one in postmenopausal females. The aim of this study was, therefore, to document whether the relationship between bone mineral density and fracture is different in young children compared with adolescents.

Methods

A matched-pair, case-control study has been conducted to evaluate bone mineral density in 469 young children and 387 adolescents of both sexes, with/without fracture due to minimal/moderate trauma with assurance that the compared groups were equally susceptible to the outcome event. All fractures were radiographically confirmed. The study utilized bone mineral areal density of the total body, spine, hips, and forearm; volumetric bone mineral density of the forearm; and metacarpal radiogrammetry measurements. The study controlled for skeletal development, bone geometry, body composition, hand grip strength, calcium intake, and vitamin D status.

Results

Adolescents with distal forearm fracture have reduced bone mineral density at multiple skeletal regions of interest. This was documented by the bone mineral areal density measurements at multiple skeletal sites (p < 0.001), volumetric bone mineral density measurements of the forearm (p < 0.0001), and metacarpal radiogrammetry (p < 0.001). Adolescent females with fracture had reduced cross-sectional areas of the radius and metacarpals. The bone status of young female and male children with fracture was no different to its controls. Increased body fatness was more prevalent among fracture cases than in controls. Around 72% of young female and male children with fracture had serum 25-hydroxyvitamin D levels below the threshold of 31 ng/ml, compared with only 42% of female controls and to 51% of male controls.

Conclusions

Adolescents with bone fragility fracture had reduced bone mineral density at multiple skeletal regions of interest, whereas this was not the case with younger children. The results of the study may have implications for the prevention of bone fragility in this segment of the pediatric population.

The Association between First Fractures Sustained during Childhood and Adulthood and Bone Measures in Young Adulthood

OBJECTIVE

To describe the association between fractures sustained at different stages of growth and bone measures in early adulthood.

STUDY DESIGN

Participants (n = 201) in southern Tasmania were at birth at a higher risk of sudden infant death syndrome; they were followed to age 25. Outcomes were areal bone mineral density at the spine, hip, and total body (by dual-energy x-ray absorptiometry) and trabecular and cortical bone measures at the radius and tibia (by high-resolution peripheral quantitative computed tomography). Fractures were self-reported and confirmed by radiographs at 8, 16, and 25 years of age. Multivariable linear regression was used to analyze the association of the occurrence of prepubertal (<9 years of age), pubertal (9-16 years of age), and postpubertal (17-25 years of age) fractures with all bone measures.

RESULTS

Over 25 years, 99 participants had at least 1 fracture. For high-resolution peripheral quantitative computed tomography measures at age 25, prepubertal fractures were negatively associated with cortical and trabecular volumetric bone mineral density and most microarchitecture measures at both the tibia and radius. Prepubertal fractures had a significant association with smaller increase of areal bone mineral density from age 8 to 16 years and at 25 years of age compared with participants with no fractures. Pubertal fractures had no association with any bone measures and postpubertal fractures were only associated with a lower trabecular number at the tibia.

CONCLUSIONS

Prepubertal fractures are negatively associated with areal bone mineral density increases during growth and high-resolution peripheral quantitative computed tomography bone measures in young adulthood. There is little evidence that fractures occurring from age 8 years onward with bone measures in young adulthood, implying that prepubertal fractures may be associated with bone deficits later in life.

Diagnosis of Recurrent Fracture in a Pediatric Cohort

Significant fracture history in children is defined as having at least one vertebral fracture, at least 2 fractures by age 10, or at least 3 fractures by age 19. Between September 2011 and December 2014, clinical data were collected on children with a significant fracture history that attended a major Australian children's hospital. Fifty-six patients were identified as having 305 fractures in total, including 44 vertebral fractures. 18% of patients (10/56) were diagnosed with osteogenesis imperfecta (OI) by a bone health expert, molecular testing or both, and they sustained 23% of all fractures (71/305). Analysis of serum bone biochemistry showed all median values to be within a normal range and no clinically significant differences between patients with and without OI. The DXA and pQCT derived bone mineral density (BMD) and bone mineral content (BMC) Z scores were reduced overall. DXA derived total body and lumbar spine areal BMD-for-age and BMC-for-age Z scores were significantly lower in children who had vertebral fractures or who were later diagnosed with OI. Similarly, pQCT performed on radii and tibiae showed Z scores significantly less than zero. pQCT-derived limb muscle cross sectional area Z scores were significantly lower in the OI subgroup. In conclusion, this study describes the bone phenotype of children referred to a tertiary hospital clinic for recurrent fractures and highlights a subset of children with previously undiagnosed OI, but a larger cohort without classic OI. Thus it can be clinically challenging to differentiate between children with OI type 1 (mild phenotype) and non-OI children without bone densitometry and genetic testing. We conclude that recurrent fractures in children should prompt a comprehensive bone and systemic health assessment to eliminate an underlying pathology.

Relationship between growth, maturation and musculoskeletal conditions in adolescents: a systematic review

Objective

To determine whether there is a relationship between physical growth and development, as determined by markers of biological maturation, and musculoskeletal conditions in adolescents.

Design

Systematic review.

Data sources

Electronic databases (PubMed, EMBASE and the Cumulative Index to Nursing and Allied Health Literature) were searched up to 6 September 2017.

Eligibility criteria for selecting studies

Studies that evaluated the association between biological maturation or growth and musculoskeletal conditions in adolescents (chronological age 10–19 years).

Results

From 20 361 titles identified by the searches, 511 full-text articles were retrieved and assessed for eligibility; 56 studies, all at high risk of bias, evaluating the relationship between maturation and/or growth and musculoskeletal conditions were included. A total of 208 estimates of association were identified across the included studies, which generally indicated no association or an unclear association between maturation, growth and musculoskeletal conditions.

Summary/Conclusions

While the relationship between maturation, growth and musculoskeletal conditions remains plausible, the available evidence is not supportive. The current body of knowledge is at high risk of bias, which impedes our ability to establish whether biological maturity and growth are independent risk factors for musculoskeletal conditions.

Cohort study shows that peripheral dual-energy X-ray absorptiometry is of limited epidemiologic use in prepubertal children

AIM

Peripheral methods are increasingly used to assess bone health, despite little evidence on their predictive ability. We aimed to evaluate the usefulness of forearm dual-energy X-ray absorptiometry in prepubertal children, by estimating the agreement between peripheral and central measures and the ability to predict fracture history.

METHODS

In 2012/2014, we assessed 1177 seven-year-old children from the Generation XXI cohort who were recruited at birth in all five public hospitals with maternity wards in Porto, Portugal. Subtotal and lumbar spine bone mineral density (BMD) and content, left-arm BMD and peripheral forearm BMD were measured. Parents reported the child's lifetime fracture history. We estimated agreement using Bland-Altman's method and Cohen's kappa. Fracture prediction ability was calculated using area under the receiver operator characteristic curve (ROC-AUC).

RESULTS

The limits of agreement were very wide, ranging from -2.20/2.20 to -1.87/1.87 standard deviations for the comparison between peripheral and central measures. Categorical agreement was also poor, with all kappa values below 0.40. In addition, none of the measures predicted fractures, because all the ROC-AUCs were close to 0.50.

CONCLUSION

This study suggests that forearm BMD has limited use for bone health research or as a basis for clinical decisions in prepubertal children.

Bone Mineralization and Fracture Risk Assessment in the Pediatric Population

Identifying children most susceptible to clinically significant fragility fractures (low trauma fractures or vertebral compression fractures) or recurrent fractures is an important issue facing general pediatricians and subspecialists alike. Over the last decade, several imaging technologies, including dual-energy X-ray absorptiometry and peripheral quantitative computed tomography, have become useful to identify abnormal bone mineralization in children and in adolescents. This review aimed to summarize the latest literature on the utility of these modalities as they pertain to use in pediatrics. In addition, we review several disease states associated with poor bone health and increased fracture risk in children, and discuss the implications of low bone mineral density in these patients. Finally, we will highlight the gaps in knowledge with regard to pediatric bone health and make recommendations for future areas of research.

Neonatal vitamin D status from archived dried blood spots and future risk of fractures in childhood: results from the D-tect study, a population-based case-cohort study

Background: Whether antenatal and neonatal vitamin D status have clinical relevance in fracture prevention has not been examined extensively, although observational studies indicate that fetal life may be a sensitive period in relation to bone growth and mineralization during childhood.Objective: We examined whether 25-hydroxyvitamin D₃ [25(OH)D₃] concentrations in stored neonatal dried blood spot (DBS) samples are associated with pediatric fracture risk. We hypothesized that in particular, low neonatal vitamin D status may be a risk factor for fracture incidence among children.Design: In a register-based case-cohort study design, the case group was composed of 1039 individuals who were randomly selected from a total of 82,154 individuals who were born during 1989-1999 and admitted to a Danish hospital with a fracture of the forearm, wrist, scaphoid bone, clavicle, or ankle at age 6-13 y. The subcohort was composed of 1600 individuals randomly selected from all Danish children born during 1989-1999. The neonatal 25(OH)D₃ concentrations in DBS samples were assessed by using highly sensitive chromatography-tandem mass spectrometry.Results: The mean ± SD 25(OH)D₃ concentration for all subjects was 27.7 ± 18.9 nmol/L [median (IQR): 23.5 nmol/L (13.3, 37.3 nmol/L)] and showed significant monthly variation (P < 0.0001) with the highest values in July and August. Individuals in the middle quintile of neonatal 25(OH)D₃ had lower odds of sustaining a fracture than did those in the lowest quintile (adjusted OR: 0.75; 95% CI: 0.58, 0.96), but a global test did not show any significant overall association (adjusted P = 0.13).Conclusions: This study suggested that neonatal vitamin D status does not influence subsequent fracture risk in childhood. This is in accordance with studies that report no association between antenatal maternal vitamin D status and childhood fractures. Further studies are needed to examine fracture risk in relation to prenatal vitamin D status in a randomized controlled setting.

Bone marrow fat content is correlated with hepatic fat content in paediatric non-alcoholic fatty liver disease

AIM

To investigate the relationship between bone marrow fat content and hepatic fat content in children with known or suspected non-alcoholic fatty liver disease (NAFLD).

MATERIALS AND METHODS

This was an institutional review board-approved, Health Insurance Portability and Accountability Act (HIPAA)-compliant, cross-sectional, prospective analysis of data collected between October 2010 to March 2013 in 125 children with known or suspected NAFLD. Written informed consent was obtained for same-day research magnetic resonance imaging (MRI) of the lumbar spine, liver, and abdominal adiposity. Lumbar spine bone marrow proton density fat fraction (PDFF) and hepatic PDFF were estimated using complex-based MRI (C-MRI) techniques and magnitude-based MRI (M-MRI), respectively. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SCAT) were quantified using high-resolution MRI. All images were acquired by two MRI technologists. Hepatic M-MRI images were analysed by an image analyst; all other images were analysed by a single investigator. The relationship between lumbar spine bone marrow PDFF and hepatic PDFF was assessed with and without adjusting for the presence of covariates using correlation and regression analysis.

RESULTS

Lumbar spine bone marrow PDFF was positively associated with hepatic PDFF in children with known or suspected NAFLD prior to adjusting for covariates (r=0.33, p=0.0002). Lumbar spine bone marrow PDFF was positively associated with hepatic PDFF in children with known or suspected NAFLD (r=0.24, p=0.0079) after adjusting for age, sex, body mass index z-score, VAT, and SCAT in a multivariable regression analysis.

CONCLUSION

Bone marrow fat content is positively associated with hepatic fat content in children with known or suspected NAFLD. Further research is needed to confirm these results and understand their clinical and biological implications.

Prenatal exposure to vitamin D from fortified margarine and risk of fractures in late childhood: period and cohort results from 222 000 subjects in the D-tect observational study

Prenatal low vitamin D may have consequences for bone health. By means of a nationwide mandatory vitamin D fortification programme, we examined the risk of fractures among 10-18-year-old children from proximate birth cohorts born around the date of the termination of the programme. For all subjects born in Denmark during 1983-1988, civil registration numbers were linked to the Danish National Patient Registry for incident and recurrent fractures occurring at ages 10-18 years. Multiplicative Poisson models were used to examine the association between birth cohort and fracture rates. The variation in fracture rates across birth cohorts was analysed by fitting an age-cohort model to the data. We addressed the potential modification of the effect of vitamin D availability by season of birth. The risk of fractures was increased among both girls and boys who were born before the vitamin D fortification terminated in 1985 (rate ratio (RR) exposed v. non-exposed girls: 1·15 (95 % CI 1·11, 1·20); RR exposed v. non-exposed boys: 1·11 (95 % CI 1·07, 1·14). However, these associations no longer persisted after including the period effects. There was no interaction between season of birth and vitamin D availability in relation to fracture risk. The study did not provide evidence that prenatal exposure to extra vitamin D from a mandatory fortification programme of 1·25 µg vitamin D/100 g margarine was sufficient to influence the risk of fractures in late childhood, regardless of season of birth. Replication studies are needed.

Correlation Between Central and Peripheral Bone Mineral Density Around the Elbow Measured by Dual-Energy X-Ray Absorptiometry in Healthy Children and Adolescents

This pilot study was performed to evaluate the correlation between central bone mineral density (BMD) and peripheral BMD around the elbow in children and adolescents and to compare BMD values across skeletal sites. Twenty-seven healthy volunteers between 5 and 18 yr of age were recruited for the study. Anthropometric measurements including height and weight were performed. Central BMD at the lumbar spine and left femur and peripheral BMD at the supracondylar area, medial condyle, lateral condyle, and olecranon were measured using dual-energy X-ray absorptiometry (DXA). Higher BMD levels were found in the central skeleton (lumbar spine and femur) than in peripheral sites around the elbow (p < 0.001). BMD values around the elbow ranged from 44.4% to 63.2% compared to the BMD values of the central skeleton. Among the peripheral sites around the elbow, the highest BMD was observed at the supracondylar area and olecranon, and the lowest BMD was found at the lateral condyle. Peripheral DXA measurements around the elbow were significantly correlated with central DXA measurements at the lumbar spine and femur. In conclusion, this study demonstrated that the measurements of BMD around the elbow were correlated with BMD at central sites. Given the small sample size in this pilot study, further study with a large cohort is required to use the BMD measurements around the elbow as a valid clinical tool for fracture risk assessment and population-based epidemiological studies.

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.

Diminished bone strength is observed in adult women and men who sustained a mild trauma distal forearm fracture during childhood

Children and adolescents who sustain a distal forearm fracture (DFF) owing to mild, but not moderate, trauma have reduced bone strength and cortical thinning at the distal radius and tibia. Whether these skeletal deficits track into adulthood is unknown. Therefore, we studied 75 women and 75 men (age range, 20 to 40 years) with a childhood (age < 18 years) DFF and 150 sex-matched controls with no history of fracture using high-resolution peripheral quantitative computed tomography (HRpQCT) to examine bone strength (ie, failure load) by micro-finite element (µFE) analysis, as well as cortical and trabecular bone parameters at the distal radius and tibia. Level of trauma (mild versus moderate) was assigned using a validated classification scheme, blind to imaging results. When compared to sex-matched, nonfracture controls, women and men with a mild trauma childhood DFF (eg, fall from standing height) had significant reductions in failure load (p < 0.05) of the distal radius, whereas women and men with a moderate trauma childhood DFF (eg, fall while riding a bicycle) had values similar to controls. Consistent findings were observed at the distal tibia. Furthermore, women and men with a mild trauma childhood DFF had significant deficits in distal radius cortical area (p < 0.05), and significantly lower dual-energy X-ray absorptiometry (DXA)-derived bone density at the radius, hip, and total body regions compared to controls (all p < 0.05). By contrast, women and men with a moderate trauma childhood DFF had bone density, structure, and strength that did not differ significantly from controls. These findings in young adults are consistent with our observations in children/adolescents with DFF, and they suggest that a mild trauma childhood DFF may presage suboptimal peak bone density, structure, and strength in young adulthood. Children and adolescents who suffer mild trauma DFFs may need to be targeted for lifestyle interventions to help achieve improved skeletal health.

The epidemiology of fractures in otherwise healthy children

Fractures in otherwise healthy children are important because they are common, impact on daily activity, and may identify those who may have an increased fracture risk as adults. This review covers the descriptive epidemiology of fractures in healthy children (aged 0-16) and provides an overview of what is known about the child-related determinants of fractures, dividing associations into those that are potentially modifiable and those that are not. Maternal-related influences during pregnancy have not been covered, nor have determinants related to the injury such as trauma level, landing surface, injury type, the physical environment, or societal impacts. Age, gender, low bone mass, and exposure to injury are the child-related determinants of fractures with the highest quality research showing a convincing association.

Quantitative computer tomography in children and adolescents: the 2013 ISCD Pediatric Official Positions

In 2007, International Society of Clinical Densitometry Pediatric Positions Task Forces reviewed the evidence for the clinical application of peripheral quantitative computed tomography (pQCT) in children and adolescents. At that time, numerous limitations regarding the clinical application of pQCT were identified, although its use as a research modality for investigation of bone strength was highlighted. The present report provides an updated review of evidence for the clinical application of pQCT, as well as additional reviews of whole body QCT scans of the central and peripheral skeletons, and high-resolution pQCT in children. Although these techniques remain in the domain of research, this report summarizes the recent literature and evidence of the clinical applicability and offers general recommendations regarding the use of these modalities in pediatric bone health assessment.

Fracture patterns and bone mass in South African adolescent-mother pairs: the Birth to Twenty cohort

The associations of fracture prevalence and bone mass in adolescents with maternal fracture history and bone mass have not been investigated previously in South Africa. Maternal bone mass has a significant inverse association with their adolescents' fracture rates and bone mass across all ethnic groups.

INTRODUCTION

Differences in fracture rates and bone mass between families and individuals of different ethnic origins may be due to differing lifestyles and/or genetic backgrounds. This study aimed to assess associations of fracture prevalence and bone mass in adolescents with maternal fracture history and bone mass, and sibling fracture history.

METHODS

Data from 1,389 adolescent-biological mother pairs from the Birth to Twenty longitudinal study were obtained. Questionnaires were completed on adolescent fractures until 17/18 years of age and on sibling fractures. Biological mothers completed questionnaires on their own fractures prior to the age of 18 years. Anthropometric and bone mass data on adolescent-biological mother pairs were collected.

RESULTS

An adolescent's risk of lifetime fracture decreased with increasing maternal lumbar spine (LS) bone mineral content (BMC; 24 % reduction in fracture risk for every unit increase in maternal LS BMC Z-score) and increased if they were white, male, or had a sibling with a history of fracture. Adolescent height, weight, male gender, maternal bone area and BMC, and white ethnicity were positive predictors of adolescent bone mass. White adolescents and their mothers had a higher fracture prevalence (adolescents 42 %, mothers 31 %) compared to the black (adolescents 20 %, mothers 6 %) and mixed ancestry (adolescents 20 %, mothers 16 %) groups.

CONCLUSION

Maternal bone mass has a significant inverse association with their adolescent off-springs' fracture risk and bone mass. Furthermore, there is a strong familial component in fracture patterns among South African adolescents and their siblings.

Fractures in hospitalized children

Hospitalized children have multiple risk factors for fragility fractures, related to disease pathophysiology, treatments, nutritional status and immobilization. Recognition and treatment of these risk factors are important to prevent morbidity associated with fractures and to promote current and future bone health. Many knowledge gaps remain regarding the ideal nutrition, physical activity, and medication regimens needed to optimize bone health and reduce the risk of fractures over the life course. This article reviews the pathogenesis, risk factors, treatment and prevention strategies for fractures in hospitalized infants and children.

Non-alcoholic fatty liver disease is associated with low bone mineral density in obese children

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in children. Liver disease can be a cause of low bone mineral density. Whether or not NAFLD influences bone health is not known.

AIM

To evaluate bone mineral density in obese children with and without NAFLD.

METHODS

Thirty-eight children with biopsy-proven NAFLD were matched for age, gender, race, ethnicity, height and weight to children without evidence of liver disease from the National Health and Nutrition Examination Survey. Bone mineral density was measured by dual energy X-ray absorptiometry. Age and gender-specific bone mineral density Z-scores were calculated and compared between children with and without NAFLD. After controlling for age, gender, race, ethnicity and total per cent body fat, the relationship between bone mineral density and the severity of histology was analysed in children with NAFLD.

RESULTS

Obese children with NAFLD had significantly (P < 0.0001) lower bone mineral density Z-scores (-1.98) than obese children without NAFLD (0.48). Forty-five per cent of children with NAFLD had low-bone mineral density for age, compared to none of the children without NAFLD (P < 0.0001). Among those children with NAFLD, children with NASH had a significantly (P < 0.05) lower bone mineral density Z-score (-2.37) than children with NAFLD who did not have NASH (-1.58).

CONCLUSIONS

The NAFLD was associated with poor bone health in obese children. More severe disease was associated with lower bone mineralisation. Further studies are needed to evaluate the underlying mechanisms and consequences of poor bone mineralisation in children with NAFLD.

Quantitative computed tomography and computed tomography in children

Quantitative computed tomography (QCT) methodologies have been instrumental in deepening our understanding of bone acquisition and strength during childhood. Important publications in the last year have drawn attention to the functional muscle-bone unit, showing that factors such as population ancestry, bone size, and muscle composition are additional dimensions of bone strength that affect muscle-bone relationships. The role of adiposity in pediatric bone health is complex and may vary by sex, puberty stage, and degree of obesity. Several new studies have demonstrated the association of peripheral QCT (pQCT) outcomes with fracture, although pQCT outcomes are not superior to dual-energy x-ray absorptiometry measures in this regard. New high-resolution pQCT studies document transient weakness in mid-puberty that coincides developmentally with the period of peak fracture incidence. These new studies will ultimately help us understand the development of sex differences in bone strength that emerge in adolescence.

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

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

Lower trabecular volumetric BMD at metaphyseal regions of weight-bearing bones is associated with prior fracture in young girls

Understanding the etiology of skeletal fragility during growth is critical for the development of treatments and prevention strategies aimed at reducing the burden of childhood fractures. Thus we evaluated the relationship between prior fracture and bone parameters in young girls. Data from 465 girls aged 8 to 13 years from the Jump-In: Building Better Bones study were analyzed. Bone parameters were assessed at metaphyseal and diaphyseal sites of the nondominant femur and tibia using peripheral quantitative computed tomography (pQCT). Dual-energy X-ray absorptiometry (DXA) was used to assess femur, tibia, lumbar spine, and total body less head bone mineral content. Binary logistic regression was used to evaluate the relationship between prior fracture and bone parameters, controlling for maturity, body mass, leg length, ethnicity, and physical activity. Associations between prior fracture and all DXA and pQCT bone parameters at diaphyseal sites were nonsignificant. In contrast, lower trabecular volumetric BMD (vBMD) at distal metaphyseal sites of the femur and tibia was significantly associated with prior fracture. After adjustment for covariates, every SD decrease in trabecular vBMD at metaphyseal sites of the distal femur and tibia was associated with 1.4 (1.1-1.9) and 1.3 (1.0-1.7) times higher fracture prevalence, respectively. Prior fracture was not associated with metaphyseal bone size (ie, periosteal circumference). In conclusion, fractures in girls are associated with lower trabecular vBMD, but not bone size, at metaphyseal sites of the femur and tibia. Lower trabecular vBMD at metaphyseal sites of long bones may be an early marker of skeletal fragility in girls.

Fracture risk in children with a forearm injury is associated with volumetric bone density and cortical area (by peripheral QCT) and areal bone density (by DXA)

Children who sustain a forearm fracture when injured have lower bone density throughout their skeleton, and have a smaller cortical area and a lower strength index in their radius. Odds ratios per SD decrease in bone characteristics measured by peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA) were similar (1.28 to 1.41).

INTRODUCTION

Forearm fractures are common in children. Bone strength is affected by bone mineral density (BMD) and bone geometry, including cross-sectional dimensions and distribution of mineral. Our objective was to identify bone characteristics that differed between children who sustained a forearm fracture compared to those who did not fracture when injured.

METHODS

Children (5-16 years) with a forearm fracture (cases, n = 224) and injured controls without fracture (n = 200) were enrolled 28 ± 8 days following injury. Peripheral QCT scans of the radius (4% and 20% sites) were obtained to measure volumetric BMD (vBMD) of total, trabecular and cortical bone compartments, and bone geometry (area, cortical thickness, and strength strain index [SSI]). DXA scans (forearm, spine, and hip) were obtained to measure areal BMD (aBMD) and bone area. Receiver operating characteristic (ROC) analyses were used to assess screening performance of bone measurements.

RESULTS

At the 4% pQCT site, total vBMD, but not trabecular vBMD or bone area, was lower (-3.4%; p = 0.02) in cases than controls. At the 20% site, cases had lower cortical vBMD (-0.9%), cortical area (-2.8%), and SSI (-4.6%) (p < 0.05). aBMD, but not bone area, at the 1/3 radius, spine, and hip were 2.7-3.3% lower for cases (p < 0.01). Odds ratios per 1 SD decrease in bone measures (1.28-1.41) and areas under the ROC curves (0.56-0.59) were similar for all bone measures.

CONCLUSIONS

Low vBMD, aBMD, cortical area, and SSI of the distal radius were associated with an increased fracture risk. Interventions to increase these characteristics are needed to help reduce forearm fracture occurrence.

Forearm fractures in children and bone health

PURPOSE OF REVIEW

Summary highlighting the evidence that bone health may affect forearm fracture risk in children.

RECENT FINDINGS

Although the incidence of other fractures and injuries are decreasing, the incidence of forearm fractures is increasing in otherwise healthy children. There is a growing volume of research that forearm fracture risk in children may be related to deficiencies in parameters of bone health. Available evidence of this relationship was summarized and included direct links to bone health (measurement of bone properties), indirect links to bone health (diet, vitamin D status, BMI), and genetic analyses.

SUMMARY

There is consistent and convincing evidence of an association between bone mineral density and forearm fracture risk in children. Studies of calcium intake and supplementation are less extensive in scope but suggest that effects of calcium deficiency on the radius may contribute to childhood forearm fracture risk. Forearm fracture risk in obese children is likely to reflect a combination of suboptimal bone health status and behavioral characteristics. Published data on the role of vitamin D status and genetic factors are limited but merit further consideration. Further investigation is needed to better understand the factors contributing to forearm fracture risk in children and translate this knowledge into effective clinical prevention and practice.

Decreasing incidence and changing pattern of childhood fractures: A population-based study

Fractures are common in children, and some studies suggest an increasing incidence. Data on population-based long-term trends are scarce. In order to establish fracture incidence and epidemiologic patterns, we carried out a population-based study in Helsinki, Finland. All fractures in children aged 0 to 15 years were recorded from public health care institutions during a 12-month period in 2005. Details regarding patient demographics, fracture site, and trauma mechanism were collected. All fractures were confirmed from radiographs. Similar data from 1967, 1978, and 1983 were used for comparison. In 2005, altogether 1396 fractures were recorded, 63% in boys. The overall fracture incidence was 163 per 10,000. Causative injuries consisted of mainly falls when running or walking or from heights less than 1.5 m. Fracture incidence peaked at 10 years in girls and 14 years in boys. An increase in fracture incidence was seen from 1967 to 1983 (24%, p < .0001), but a significant decrease (18%, p < .0001) was seen from 1983 to 2005. This reduction was largest in children between the ages of 10 and 13 years. Despite the overall decrease and marked decrease in hand (-39%, p < .0001) and foot (-48%, p < .0001) fractures, the incidence of forearm and upper arm fractures increased significantly by 31% (p < .0001) and 39% (p = .021), respectively. Based on these findings, the overall incidence of childhood fractures has decreased significantly during the last two decades. Concurrently, the incidence of forearm and upper arm fractures has increased by one-third. The reasons for these epidemiologic changes remain to be elucidated in future studies.

Fat mass accumulation compromises bone adaptation to load in Finnish women: a cross-sectional study spanning three generations

Body weight and lean mass correlate with bone mass, but the relationship between fat mass and bone remains elusive. The study population consisted of 396 girls and 138 premenopausal mothers and 114 postmenopausal grandmothers of these girls. Body composition and tibial length were assessed using dual-energy X-ray absorptiometry (DXA), and bone traits were determined at the tibia using peripheral quantitative computed tomography (pQCT) in the girls at the ages of 11.2 ± 0.8, 13.2 ± 0.9, and 18.3 ± 1.0 years and in the mothers (44.7 ± 4.1 years) and grandmothers (70.7 ± 6.3 years). The values of relative bone strength index (RBSI), an index reflecting the ratio of bone strength to the load applied on the tibia, were correlated among family members (all p < .05). The mean values of RBSI were similar among 11- and 18-year-old girls and premenopausal women but significantly lower in 13-year-old girls and postmenopausal women. However, in each age group, subjects in the highest BMI tertiles had the lowest RBSI values (all p < .01). RBSI was inversely associated with body weight (all p < .01), indicating a deficit in bone strength relative to the applied load from greater body weight. RBSI was inversely associated with fat mass (all p < .001) across age groups and generations but remained relatively constant with increasing lean mass in girls and premenopausal women (all p > .05), indicating that the bone-strength deficit was attributable to increased fat mass, not lean mass. Moreover, the adverse effect of fat mass was age-dependent, with every unit increase in fat mass associated with a greater decrease in RBSI in pre- and postmenopausal women than in girls (all p < .001). This is largely due to the different capacity of young and adult bones to increase diaphyseal width by periosteal apposition in response to increased load. In summary, increasing body weight with fat accumulation is accompanied by an age-dependent relative bone-strength deficit in women because the beneficial effects of increased fat mass on bone, if any, do not compensate for the mechanical burden that it imposes.

Bone and body segment lengthening and widening: a 7-year follow-up study in pubertal girls

During growth bone increases in length and width as does the body size. The aim of this paper was to examine the growth pattern of body height and weight, and the width and length of various body segments, and to establish the timing of peak growth velocity (PV) in relation to time of menarche in a cohort of Finnish girls followed from age 10 until 18. The study was a 7-year longitudinal cohort study. Widths and lengths of body segments and bones were measured from DXA scan images using bone landmarks in 396 girls aged 10 to 13 years at baseline, and in 255 mothers and 159 grandmothers. The girls' growth velocities (rate of change with time) peaked at 13.5 months prior to menarche for height, 14.4 months for weight, and 15.4 months for BMI. Shoulder width peaked at 18.2 months, lesser pelvis width at 13.5 months and greater pelvis width at 11.6 months prior to menarche. The PV of various body segment lengths showed that the femur peaked earliest at 20.7 months prior to menarche, followed by the humerus (at 18.0 months), radius (at 17.4 months), tibia (at 17.5 months), and trunk (at 11.8 months), respectively. All the long bones were linearly correlated with height while the flat and irregular bones had a nonlinear growth relationship with height (r(2)=0.73-0.88). By the age of 18 years the girls had reached their mothers' height (101%) and humerus, radius, femur and tibia lengths (100-101%), but not their mothers' shoulder, great pelvis and lesser pelvis widths (98%, 95% and 93%, respectively). Our data confirmed that, after bone elongation had ceased, segment width continued to increase, although at a slower speed, into early adulthood. The wide variations in growth velocity of these anthropomorphic measurements underscore the need to optimize nutrition and physical activity from early puberty onward in order to maximize bone development.

Familial resemblance and diversity in bone mass and strength in the population are established during the first year of postnatal life

Familial resemblance and diversity in bone structure and strength in adulthood are determined in part during growth. Whether these characteristics are established during gestation or shortly after birth is not known. Total-body, lumbar spine, and femoral neck size and mass and indices of tibial bending strength and distal radial compressive strength were measured using bone densitometry and quantitative computed tomography in 236 girls at 18.5 years of age. Among them, 219, 141, and 105 girls had crown-heel length (CHL) and weight recorded at birth and at 6 and 12 months of age, and then height and weight were recorded at 3, 5, 10, 13, and 15 years of age in 181, 176, 127, 111, and 228 girls, respectively. Of these girls, 101 and 93 girls also had bone structure assessed at 11 and 13 years of age, respectively. Similar bone measurements were made once in 78 mother-father pairs. CHL and weight at birth did not correlate or did so weakly with bone traits in girls at 18 years of age. By contrast, CHL at 6 months correlated with the height, bone traits, and strength at puberty and at 18 years of age (r = 0.24-0.56, p < .001) in girls and with their parents' height and bone traits (r = 0.15-0.37, p < .05). When the girls' CHL at 6 months was stratified into quartiles, the absolute and relative differences in bone traits observed at puberty (approximately 11.5 years) were maintained as these traits tracked during the ensuing 7 years. Similarly, weight at 6 months correlated with the girls' bone traits at puberty and 18 years of age (r = 0.22-0.55, p < .05). During puberty and at 18 years of age, the girls' bone traits correlated with the corresponding traits in their parents (r = 0.32-0.43, p < .01). It is concluded that familial resemblance in bone structural strength and the position of an individual's bone traits relative to others in adulthood are likely to be established during the first year of life. Thus susceptibility to bone fragility late in life has its antecedents established early in life.