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

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.

Resumption of school after lockdown in COVID-19 pandemic: Three case reports

BACKGROUND

Students in the 9^th grade of junior high school in Changsha were under a 75 d lockdown due to the coronavirus disease 2019 (COVID-19) pandemic. After the resumption of school post-lockdown, the 9^th grade students in Changsha faced the entrance physical examination test for senior high school.

CASE SUMMARY

We report on 3 cases of occult fracture on the same site in adolescents of the same grade since resumption of school after the lockdown from the COVID-19 pandemic. Three students in the 9^th grade of junior high school who were facing the physical examination in 2 wk were diagnosed with an occult fracture of the distal femur.

CONCLUSION

It is recommended that the students, parents, education providers and policy makers should all pay attention to the physical exercise of students when the resumption of school after lockdown occurs and they should be aware of occult fractures when the adolescents have pain after physical exercise.

Goldilocks Days: optimising children's time use for health and well-being

BACKGROUND

One size rarely fits all in population health. Differing outcomes may compete for best allocations of time. Among children aged 11-12 years, we aimed to (1) describe optimal 24-hour time use for diverse physical, cognitive/academic and well-being outcomes, (2) pinpoint the 'Goldilocks Day' that optimises all outcomes and (3) develop a tool to customise time-use recommendations.

METHODS

In 2004, the Longitudinal Study of Australian Children recruited a nationally-representative cohort of 5107 infants with biennial follow-up waves. We used data from the cross-sectional Child Health CheckPoint module (2015-2016, n=1874, 11-12 years, 51% males). Time use was from 7-day 24-hour accelerometry. Outcomes included life satisfaction, psychosocial health, depressive symptoms, emotional problems, non-verbal IQ; vocabulary, academic performance, adiposity, fitness, blood pressure, inflammatory biomarkers, bone strength. Relationships between time use and outcomes were modelled using compositional regression.

RESULTS

Optimal daily durations varied widely for different health outcomes (sleep: 8.3-11.4 hours; sedentary: 7.3-12.2 hours; light physical activity: 1.7-5.1 hours; moderate-to-vigorous physical activity (MVPA): 0.3-2.7 hours, all models p≤0.04). In general, days with highest physical activity (predominantly MVPA) and low sedentary time were optimal for physical health, while days with highest sleep and lowest sedentary time were optimal for mental health. Days with highest sedentary time and lowest physical activity were optimal for cognitive health. The overall Goldilocks Day had 10 hours 21 min sleep, 9 hours 44 min sedentary time, 2 hours 26 min light physical activity and 1 hour 29 min MVPA. Our interactive interface allows personalisation of Goldilocks Days to an individual's outcome priorities.

CONCLUSION

'Goldilocks Days' necessitate compromises based on hierarchies of priorities for health, social and economic outcomes.

The importance of maternal pregnancy vitamin D for offspring bone health: learnings from the MAVIDOS trial

Optimisation of skeletal mineralisation in childhood is important to reduce childhood fracture and the long-term risk of osteoporosis and fracture in later life. One approach to achieving this is antenatal vitamin D supplementation. The Maternal Vitamin D Osteoporosis Study is a randomised placebo-controlled trial, the aim of which was to assess the effect of antenatal vitamin D supplementation (1000 IU/day cholecalciferol) on offspring bone mass at birth. The study has since extended the follow up into childhood and diversified to assess demographic, lifestyle and genetic factors that determine the biochemical response to antenatal vitamin D supplementation, and to understand the mechanisms underpinning the effects of vitamin D supplementation on offspring bone development, including epigenetics. The demonstration of positive effects of maternal pregnancy vitamin D supplementation on offspring bone development and the delineation of underlying biological mechanisms inform clinical care and future public-health policies.

Prediction of maturity offset and age at peak height velocity in a longitudinal series of boys and girls

BACKGROUND

Predicted maturity offset, defined as time before peak height velocity (PHV) is increasingly used as an indicator of maturity status in studies of physical activity, fitness, and sport.

OBJECTIVE

To validate maturity offset prediction equations in longitudinal samples of boys and girls.

METHODS

The original and modified maturity offset prediction equations were applied to serial data for 266 boys (8-17 years) and 147 girls (8-16 years) from the Cracow Growth Study. Actual age at PHV for each youngster was estimated with the SITAR protocol. In addition to maturity offset, the difference between CA at prediction and maturity offset provided an estimate of predicted age at PHV.

RESULTS

Predicted maturity offset and age at PHV increased, on average, with CA at prediction. Variation in predictions was reduced compared to that in observed ages at offset and at PHV, and was more apparent with the modified equations. Relatively few predicted ages at PHV approximated observed age at PHV in early and late maturing youth of both sexes; predictions were later than observed among the former, and earlier than observed among the latter.

CONCLUSION

Predicted maturity offset and ages at PHV with the original and modified equations increase with CA at prediction, have reduced variation, and have major limitations with early and late maturing boys and girls.

The Utility of DXA Assessment at the Forearm, Proximal Femur, and Lateral Distal Femur, and Vertebral Fracture Assessment in the Pediatric Population: 2019 ISCD Official Position

Dual-energy X-ray absorptiometry (DXA) is widely used in the evaluation of bone fragility in children. Previous recommendations emphasized total body less head and lumbar spine DXA scans for clinical bone health assessment. However, these scan sites may not be possible or optimal for all groups of children with conditions that threaten bone health. The utility of DXA scans of the proximal femur, forearm, and radius were evaluated for adequacy of reference data, precision, ability of predict fracture, and applicability to all, or select groups of children. In addition, the strengths and limitations of vertebral fracture assessment by DXA were evaluated. The new Pediatric Positions provide guidelines on the use of these additional measures in the assessment of skeletal health in children.

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.

Fat and bone in children - where are we now?

The risk of fracture secondary to low-impact trauma is greater in obese children, suggesting obese children are at risk of skeletal fragility. However, despite this finding, there is a lack of agreement about the impact of excessive adiposity on skeletal development. The combination of poor diet, sedentary lifestyle, greater force generated on impact through falls, and greater propensity to falls may in part explain the increased risk of fracture in obese children. To date, evidence suggests that in early childhood years, obesity confers a structural advantage to the developing skeleton. However, in time, this relationship attenuates and then reverses, such that there is a critical period during skeletal development when obesity has a detrimental effect on skeletal structure and strength. Fat mass may be important to the developing cortical and trabecular bone compartments, provided that gains in fat mass are not excessive. However, when fat accumulation reaches excessive levels, unfavorable metabolic changes may impede skeletal development. Evidence from studies examining bone microstructure suggests skeletal adaption to excessive load fails, and bone strength is relatively diminished in relation to body size in obese children. Mechanisms that may explain these changes include changes in the hormonal environment, particularly in relation to alterations in adipokines and fat distribution. Given the concomitant rise in the prevalence of childhood obesity and fractures, as well as adult osteoporosis, further work is required to understand the relationship between obesity and skeletal development.

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.

Fracture Prospectively Recorded From Prepuberty to Young Adulthood: Are They Markers of Peak Bone Mass and Strength in Males?

Fractures are common in otherwise healthy children and adolescents. They result from trauma of varying severity. Some reflect a greater skeletal fragility. A long-term implication of these fractures is their potentiality to predict adult bone fragility and increased risk of osteoporosis in later life. Using dual-energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HR-pQCT), and micro-finite element analysis (μFEA) measurements, we previously found in 124 healthy females, followed from the age of 7.9 to 20.4 years, substantial deficits in both structural and strength components of the radius in the 42 girls who sustained a fracture during skeletal development. The objective of the current study was to assess in healthy males the relationship between fracture during development and expression of bone fragility in adulthood. A cohort of 152 boys was followed from age 7.4 ± 04 (mean ± SD) to 22.6 ± 0.7 years, ie, when peak bone mass is attained. Ninety participants (59.2%) sustained at least one fracture during growth, with highest incidence within the 10- to 13-year age range. Forearm was the most frequent site of fractures. At 7.4 years, several bone DXA-measured variables (areal bone mineral density [aBMD], bone mineral content [BMC]) were lower in the group with a positive fracture history during skeletal development compared with the non-fractured group. In contrast, at 22.6 years, no DXA-measured sites, including forearm, indicated a deficit in the fractured group compared with the non-fractured group. Likewise, at 22.6 years, neither HR-pQCT nor μFEA measurements, including distal radius, showed a structural or strength deficit in the fractured group. These results markedly contrast with a similar prospective study using the same technical and clinical design in 124 healthy girls. In conclusion, our prospective studies suggest a sex difference in the predictability of bone fragility in young adults who sustained fractures during childhood and adolescence. This difference might be related to the degree of trauma severity, usually lower in girls than in boys. © 2017 American Society for Bone and Mineral Research.

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.

Prevalence of Fracture in Healthy Iranian Children Aged 9-18 Years and Associated Risk Factors; A Population Based Study

OBJECTIVE

To determine the prevalence of fractures and associated risk factors in healthy Iranian children and adolescents.

METHODS

In this cross sectional population based study, 478 healthy Iranian children and adolescents aged 9-18 years old participated. Baseline data and bone mineral content and density have been determined. One questionnaire was completed for all individuals including previous history of fracture, its location, and level of trauma. Albumin, calcium, phosphorus, alkaline phosphatase, and vitamin D levels were measured.

RESULTS

We found a prevalence of 12.9% for fracture. (34.5% for girls and 65.5% for boys); about 71% suffered long bone fracture with distal forearm as the most common site. Totally 58% of the boys and 54% of the girls had fracture with low-energy trauma. The fracture group had lower bone mineral apparent density in the lumbar spine (0.19±0.04 vs. 0.20±0.03, p=0.04), lower serum albumin (4.6±0.5 vs 4.8±0.4, p=0.02), and higher serum alkaline phosphatase level (446±174 vs. 361±188, p=0.02) compared with non-fracture subjects. By logistic regression analysis, we found a significant association for sex, and bone mineral content of the lumbar spine with fracture (p=0.003, p=0.039).

CONCLUSION

Compared to other studies, our subjects had lower rate of fracture. We found an association between low bone density and fracture in children and adolescents. This finding has important implications for public health. Further research may contribute to recognition of preventive measures.

Forearm bone mineralization in recently diagnosed female adolescents with a premenarchal onset of anorexia nervosa

OBJECTIVE

Data available on bone mineralization by peripheral quantitative computed tomography (pQCT) in adolescents with an early onset anorexia nervosa (AN) is limited. We investigated whether a disturbed bone mineralization can be observed at the distal radius in recently diagnosed female adolescents with AN and a premenarchal onset of this disease.

METHOD

Twenty-four premenarchal patients with AN and 22 healthy females which were age and height matched, were selected from our reference database; both groups underwent a pQCT bone assessment at the distal radius of the nondominant arm.

RESULTS

The patients age ranged between 13.3 and 18.4 years. Their percent weight loss ranged between 5 and 36% (median 23%) and occurred within the preceding 3 to 44 months. Trabecular volumetric bone mineral density of the patient group was significantly lower than the comparison group (185.6 ± 30.2 vs.209.3 ± 34.0 mm(2) ; p = 0.02). Bone cross-sectional area, bone mineral content, total volumetric bone mineral density and periosteal circumference were also lower, albeit not significantly. The bone parameters were unrelated to the under nutrition severity and duration.

DISCUSSION

In premenarchal patients with AN the trabecular bone mineralization of the forearm is significantly reduced, this might be an early indicator of altered bone mineral accrual. © 2016 Wiley Periodicals, Inc.(Int J Eat Disord 2016; 49:809-812).

Bone material strength is associated with areal BMD but not with prevalent fractures in older women

Reference point indentation is a novel method to assess bone material strength index (BMSi) in vivo. We found that BMSi at the mid-tibia was weakly associated with spine and hip areal bone mineral density but not with prevalent fracture in a population-based cohort of 211 older women.

INTRODUCTION

Reference point indentation is a novel method to assess BMSi in vivo. Lower BMSi has been observed in patients with prior fracture than in controls, but no association between BMSi and areal bone mineral density (aBMD) has been found. Population-based association studies and prospective studies with BMSi and fractures are lacking. We hypothesized that BMSi would be associated with prevalent fractures in older Swedish women. The aim was to investigate the associations between BMSi, aBMD, and prevalent fracture in older women.

METHODS

Two hundred eleven women, mean age 78.3 ± 1.1 years, were included in this cross-sectional, population-based study. BMSi was assessed using the OsteoProbe device at the mid-tibia. Areal BMD of the hip, spine, and non-dominant radius was measured using dual-energy X-ray absorptiometry (DXA). Fracture history was retrieved using questionnaires, and vertebral fractures were identified using vertebral fracture assessment (VFA) by DXA.

RESULTS

One hundred ninety-eight previous fractures in 109 subjects were reported. A total of 106 women had a vertebral fracture, of which 58 women had moderate or severe fractures. An inverse correlation between BMSi and weight (r = -0.14, p = 0.04) was seen, and BMSi differed according to operator (ANOVA p < 0.01). Adjusting for weight and operator in a linear regression model, we found that BMSi was positively associated with aBMD of the total hip (β = 0.14, p = 0.04), non-dominant radius (β = 0.17, p = 0.02), and lumbar spine (L1-L4) (β = 0.14, p < 0.05). Using logistic regression, we could not find any association in crude or adjusted BMSi (for age, weight, height, walking speed, calcium intake, smoking, bisphosphonate and glucocorticoid use, and operator) with prevalent fractures.

CONCLUSION

We conclude that BMSi is associated with aBMD but not with prevalent fracture in a population-based cohort of 211 older women.

The muscle-bone interaction in Turner syndrome

OBJECTIVES

Turner syndrome (TS) is associated with an increased fracture rate due to reduced bone strength, which is mainly determined by skeletal muscle force. This study aimed to assess the muscle force-bone strength relationship in TS and to compare it with that of healthy controls.

METHODS

This study included 39 girls with TS and 67 healthy control girls. Maximum muscle force (Fmax) was assessed through multiple one-legged hopping with jumping mechanography. Peripheral quantitative computerized tomography assessed the bone strength index at the tibial metaphysis (BSI 4) and the polar strength-strain index at the diaphysis (SSI polar 66). The effect of TS on the muscle-bone unit was tested using multiple linear regression.

RESULTS

TS had no impact on Fmax (p=0.14); however, a negative effect on bone strength (p<0.001 for BSI 4 and p<0.01 for SSI polar 66) was observed compared with healthy controls. Bone strength was lower in the TS group (by 18%, p<0.01, for BSI 4 and by 7%, p=0.027, for SSI polar 66), even after correcting for Fmax.

CONCLUSIONS

Similar muscle force induces lower bone strength in TS compared with healthy controls, which suggests altered bone-loading sensitivity in TS.

Prior fracture as a risk factor for future fracture in an Australian cohort

SUMMARY

This study investigated the influence of prior fracture on the risk of subsequent fracture. There was a higher risk of subsequent fracture in both young and older adult age groups when Australian males or females had already sustained a prior fracture. Fracture prevention is important throughout life for both sexes.

INTRODUCTION

The purpose of this study was to determine the impact of prior fracture on the risk of subsequent fracture across the adult age range in Australian males and females.

METHODS

All-cause fractures were grouped into age categories for males and females enrolled in the Geelong Osteoporosis Study (Australia) using retrospective self-report data and prospective radiology-confirmed data. For all age categories, the relative risk (RR and 95% confidence interval (CI)) of subsequent fracture in a later age category was compared between those with prior fracture and those without.

RESULTS

For both sexes, childhood fracture increased the risk of subsequent fracture in adolescence (males: RR 21.7; 95% CI 16.0, 27.4; females: RR 8.1; 3.5, 12.8). Males with adolescent fracture had increased risk of subsequent fracture in early adulthood (RR 11.5; 5.7, 17.3) and mid-adulthood (RR 13.0; 6.3, 19.7). Additionally, males with young adulthood or mid-adulthood fracture had increased risk of subsequent fracture in the following age group (RR 11.2; 4.4, 17.9, and RR 6.2; 0.8, 11.7, respectively). Mid-adult fractures increased the risk of subsequent fracture in older adulthood (RR 6.2; 0.8, 11.7). Females with childhood or adolescent fracture had an increased risk of fracture in young adulthood (RR 4.3; 0.7, 7.9, and RR 10.5; 4.4, 16.6), and prior fracture in older adult life increased the risk of subsequent fracture in old age (RR 14.9; 6.4. 23.3).

CONCLUSIONS

Fracture prevention strategies may be more effective if attention is directed towards individuals with prior fracture at any age as they have a higher likelihood of sustaining a subsequent fracture later in life.

Age- and sex-related patterns of first fracture and fracture prevalence

There are few data documenting the pattern of prevalent fracture across the entire adult age range, so we aimed to address this gap by investigating the prevalence of fractures in an Australian cohort. All-cause (ever) fractures were identified for males and females enrolled in the Geelong Osteoporosis Study (Australia) using a combination of radiology-confirmed and self-reported data. First fractures were used to generate age-related frequencies of individuals who had ever sustained a fracture. Of 1,538 males and 1,731 females, 927 males and 856 females had sustained at least one fracture since birth. The proportion of all prevalent fractures in the 0-10 year age group was similar for both sexes (~10%). In males, the proportion with prevalent fracture increased to 34.1% for age 11-20 year. Smaller increases were observed into mid-life, reaching a plateau at ~50% from mid to late life. The age-related prevalence of fracture for females showed a more gradual increase until mid-life. For adulthood prevalent fractures, approximately 20% of males had sustained a first adulthood fracture in the 20-30 year age group, with a gradual increase up to the oldest age group (49.1%), while females showed an exponential pattern of increase from the 20-30 year age group (6.8%) to the oldest age group (60.4%). In both sexes, those who had not sustained a fracture in childhood or early adulthood generally appeared to remain fracture-free until at least the sixth decade. When considering the prevalence of adulthood fractures across the age groups, males showed a gradual increase while females showed an exponential increase.

Vitamin D and skeletal health in infancy and childhood

During growth, severe vitamin D deficiency in childhood can result in symptomatic hypocalcaemia and rickets. Despite the suggestion from some studies of a secular increase in the incidence of rickets, this observation may be driven more by changes in population demographics than a true alteration to age, sex and ethnicity-specific incidence rates; indeed, rickets remains uncommon overall and is rarely seen in fair-skinned children. Additionally, the impact of less severe vitamin D deficiency and insufficiency has received much interest in recent years, and in this review, we consider the evidence relating vitamin D status to fracture risk and bone mineral density (BMD) in childhood and adolescence. We conclude that there is insufficient evidence to support the suggestion that low serum 25-hydroxyvitamin D [25(OH)D] increases childhood fracture risk. Overall, the relationship between 25(OH)D and BMD is inconsistent across studies and across skeletal sites within the same study; however, there is evidence to suggest that vitamin D supplementation in children with the lowest levels of 25(OH)D might improve BMD. High-quality randomised trials are now required to confirm this benefit.

Bone densitometry in children and adolescents

PURPOSE OF REVIEW

Abnormalities in bone health are increasingly recognized in the pediatric population. Although the methodologies for assessing bone mineral density were originally developed for adults, great strides have been made in recent years, improving their applicability to children. Understanding these technologies, their interpretation, utility, and limitations is critical when assessing a child or adolescent with a suspected abnormality in bone mineral density.

RECENT FINDINGS

Improved normative databases that address some of the confounding variables in the growing and maturing child have solidified dual-energy X-ray absorptiometry as the preferred method for the assessment of bone mineral density in children. Consensus statements by expert panels now provide specific guidance to clinicians seeking to evaluate children with fractures or at risk for fractures. Although still primarily a research tool, continued development of quantitative computed tomography applications in pediatrics suggests there may be a complementary role for clinical use in the future.

SUMMARY

In the child or adolescent with a significant fracture history or a potential for fractures because of an underlying cause, clinicians now have guidelines and normative data to better focus their evaluation. Likewise, researchers can use this information to improve clinical trial design and interpretation of results.

Muscle density predicts changes in bone density and strength: a prospective study in girls

OBJECTIVE

We sought to determine whether muscle density, an index of skeletal muscle fat content, was predictive of 2-year changes in weight-bearing bone parameters in young girls.

METHODS

Two-year prospective data from 248 girls, aged 8-13 years at baseline. Peripheral quantitative computed tomography was used to measure changes in bone strength indices (bone strength index [BSI, mg(2)/mm(4)] and strength-strain index [SSIp, mm(3)]) and volumetric bone mineral density [vBMD, mg/cm(3)] at distal metaphyseal and diaphyseal regions of the femur and tibia, as well as calf and thigh muscle density (mg/cm(3)), and muscle cross-sectional area (MCSA, mm(2)), indices of skeletal muscle fat content and muscle force production, respectively.

RESULTS

After controlling for potential confounders, greater gains in femur BSI (44%, P<0.002), total femur vBMD (114%, P<0.04) and femur trabecular vBMD (306%, P<0.002) occurred in girls in the lowest versus the highest groups of baseline thigh muscle density. Greater gains in tibial BSI (25%, P<0.03) and trabecular vBMD (190%, P<0.002) were also observed in the lowest versus the highest baseline calf muscle density groups.

CONCLUSION

Baseline muscle density is a significant predictor of changes in bone density and bone strength in young girls during a period of rapid skeletal development.

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.

Standardizing evaluation of pQCT image quality in the presence of subject movement: qualitative versus quantitative assessment

Peripheral quantitative computed tomography (pQCT) is an essential tool for assessing bone parameters of the limbs, but subject movement and its impact on image quality remains a challenge to manage. The current approach to determine image viability is by visual inspection, but pQCT lacks a quantitative evaluation. Therefore, the aims of this study were to (1) examine the reliability of a qualitative visual inspection scale and (2) establish a quantitative motion assessment methodology. Scans were performed on 506 healthy girls (9-13 years) at diaphyseal regions of the femur and tibia. Scans were rated for movement independently by three technicians using a linear, nominal scale. Quantitatively, a ratio of movement to limb size (%Move) provided a measure of movement artifact. A repeat-scan subsample (n = 46) was examined to determine %Move's impact on bone parameters. Agreement between measurers was strong (intraclass correlation coefficient = 0.732 for tibia, 0.812 for femur), but greater variability was observed in scans rated 3 or 4, the delineation between repeat and no repeat. The quantitative approach found ≥95% of subjects had %Move <25 %. Comparison of initial and repeat scans by groups above and below 25% initial movement showed significant differences in the >25 % grouping. A pQCT visual inspection scale can be a reliable metric of image quality, but technicians may periodically mischaracterize subject motion. The presented quantitative methodology yields more consistent movement assessment and could unify procedure across laboratories. Data suggest a delineation of 25% movement for determining whether a diaphyseal scan is viable or requires repeat.

Physical activity is associated with bone geometry of premenarcheal girls in a dose-dependent manner

OBJECTIVE

To determine the relationship between habitual physical activity (PA) level and peripheral qualitative computed tomography-determined quantitative tibia characteristics of premenarcheal girls.

METHODS

Premenarcheal girls matched for age (10-13 years), bone age and maturity level were assigned into: a) low PA group (LPA, n=25), b) moderate PA group (MPA, n=17), and c) high PA group (HPA, n=18). Participants' daily dietary intake, tibia's geometry and serum levels of calcium and vitamin D were assessed.

RESULTS

Premenarcheal girls demonstrating HPA exhibited greater pericortical thickness, cross-sectional area (CSA) and bone mineral content (BMC) (p<.001) in cortical bone, greater BMC, volumetric bone density (vBMD) and polar stress strength index (SSIp) in trabecular bone (p<0.001-0.05) and greater total BMC (p<.05) and vBMD (p<.01) when compared to their physically inactive or moderately active counterparts. MPA exhibited greater values of cortical BMC (p<.01) and SSIp (p<.05) than LPA. Partial correlation analysis (adjusted for BMI) revealed modest associations between PA score and bone geometry parameters (r=0.36-0.49, p<.05) at 38% of tibia length.

CONCLUSIONS

Habitual PA affects geometry of both cortical and trabecular areas of a long bone of premenarcheal girls in a dose-dependent manner. Specifically, PA increases both the density and size of cortical bone but only the density of trabecular bone during preadolescence. Given the importance of peak bone mass for future fracture risk, high levels of PA during childhood could be a major target for public health interventions aimed at optimising bone health in prepubertal children when the greatest bone gains occur.

X-ray-verified fractures are associated with finite element analysis-derived bone strength and trabecular microstructure in young adult men

It has been suggested that fracture during childhood could be a predictor of low peak bone mass and thereby a potential risk factor for osteoporosis and fragility fractures later in life. The aim of this cross-sectional, population-based study was to investigate whether prevalent fractures, occurring from birth to young adulthood, were related to high-resolution peripheral quantitative computed tomography (HR-pQCT)-derived trabecular and cortical microstructure, as well as bone strength estimated by finite element (FEA) analysis of the radius and tibia in 833 young adult men around the time of peak bone mass (ages 23 to 25 years). In total, 292 subjects with prevalent X-ray-verified fractures were found. Men with prevalent fractures had lower trabecular bone volume fraction (BV/TV) at the radius (5.5%, p < 0.001) and tibia (3.7%, p < 0.001), as well as lower cortical thickness (5.1%, p < 0.01) and cortical cross-sectional area (4.1%, p < 0.01) at the tibia. No significant differences were seen for the cortical porosity or mean pore diameter. Using a logistic regression model (including age, smoking, physical activity, calcium intake, height, and weight as covariates), every SD decrease of FEA-estimated failure load was associated with an increased prevalence of fractures at both the radius (odds ratio [OR] 1.22 [1.03-1.45]) and tibia (OR 1.32 [1.11-1.56]). Including dual-energy X-ray absorptiometry (DXA)-derived radius areal bone mineral density (aBMD), cortical thickness, and trabecular BV/TV simultaneously in a logistic regression model (with age, smoking, physical activity, calcium intake, height, and weight as covariates), BV/TV was inversely and independently associated with prevalent fractures (OR 1.28 [1.04-1.59]), whereas aBMD and cortical thickness were not (OR 1.19 [0.92-1.55] and OR 0.91 [0.73-1.12], respectively). In conclusion, prevalent fractures in young adult men were associated with impaired trabecular BV/TV at the radius, independently of aBMD and cortical thickness, indicating that primarily trabecular bone deficits are of greatest importance for prevalent fracture in this population.

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.

Selective reduction in trabecular volumetric bone mineral density during treatment for childhood acute lymphoblastic leukemia

During treatment of childhood acute lymphoblastic leukemia (ALL) fracture incidence is increased. Studies using DXA, which measures a composite of both trabecular and cortical BMD, have shown reduced BMD during treatment. We investigated changes in compartmental (cortical and trabecular) volumetric BMD (vBMD) and bone geometry using peripheral quantitative computed tomography. These outcomes were also analysed in relation to adiposity and treatment factors. Thirty nine patients with ALL (64% male, median age 7.2 years (4.1-16.9)) were compared to 34 healthy controls (50% male, median age 9.1 years (4.4-18.7)). DXA-derived age-specific standard deviation scores (SDS) of the lumbar spine (LS) and femoral neck (FN) were reduced in subjects with ALL compared to controls (p ≤ 0.01). This persisted following adjustment for body size using height-specific SDS (LS -0.72 ± 1.02 vs -0.18 ± 0.72, p=0.01; FN -1.53 ± 0.96 vs -0.74 ± 0.74, p=0.001) and bone mineral apparent density (BMAD) SDS (LS -0.76 ± 1.14 vs 0.04 ± 1.08, p=0.01; FN -1.63 ± 1.38 vs -0.16 ± 1.20, p<0.001). Radial and tibial trabecular vBMD was also reduced (196.5 ± 54.9 mg/cm(3) vs 215.2 ± 39.9 mg/cm(3), p=0.03 and 232.8 ± 60.3mg/cm(3) vs 267.5 ± 60.2mg/cm(3), p=0.002, respectively), but cortical vBMD at the radius and tibia was similar in patients and controls. A lowered tibial bone strength index (BSI) was identified in patients with ALL (53.9 ± 23.1mg/mm(4) vs 82.5 ± 27.8 mg/mm(4), p<0.001) suggesting lower fracture threshold from compressive forces. No relationships with measures of adiposity, duration of treatment or cumulative corticosteroid dose were identified. Our findings therefore suggest that reduction in trabecular vBMD during childhood ALL treatment may contribute to the observed increased fracture incidence and bony morbidity in this group.

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.

Skeletal muscle fat content is inversely associated with bone strength in young girls

Childhood obesity is an established risk factor for metabolic disease. The influence of obesity on bone development, however, remains controversial and may depend on the pattern of regional fat deposition. Therefore, we examined the associations of regional fat compartments of the calf and thigh with weight-bearing bone parameters in girls. Data from 444 girls aged 9 to 12 years from the Jump-In: Building Better Bones study were analyzed. Peripheral quantitative computed tomography (pQCT) was used to assess bone parameters at metaphyseal and diaphyseal sites of the femur and tibia along with subcutaneous adipose tissue (SAT, mm(2) ) and muscle density (mg/cm(3) ), an index of skeletal muscle fat content. As expected, SAT was positively correlated with total-body fat mass (r = 0.87-0.89, p < .001), and muscle density was inversely correlated with total-body fat mass (r = -0.24 to -0.28, p < .001). Multiple linear regression analyses with SAT, muscle density, muscle cross-sectional area, bone length, maturity, and ethnicity as independent variables showed significant associations between muscle density and indices of bone strength at metaphyseal (β = 0.13-0.19, p < .001) and diaphyseal (β = 0.06-0.09, p < .01) regions of the femur and tibia. Associations between SAT and indices of bone strength were nonsignificant at all skeletal sites (β = 0.03-0.05, p > .05), except the distal tibia (β = 0.09, p = .03). In conclusion, skeletal muscle fat content of the calf and thigh is inversely associated with weight-bearing bone strength in young girls.

Boys with haemophilia have low trabecular bone mineral density and sarcopenia, but normal bone strength at the radius

Although a decreased areal bone mineral density (BMD) has been reported in patients with haemophilia, data are lacking that would reflect the three-dimensional structure of the bone and the muscle-bone relationship. We aimed to assess volumetric BMD, bone geometry and muscle-bone phenotype in boys with haemophilia, and to describe the association between clinical characteristics of haemophilia and bone quality and structure. A cross-sectional study was conducted in 41 boys with haemophilia (mean age 12.4, range 6.6-19.8 years) using peripheral quantitative CT (pQCT) at the nondominant forearm. Results were transformed into Z-scores using previously published reference data. Significant differences were tested by one-sample t-test or sign test. Two-sample t-test and anova were used to compare results between subgroups of patients divided according to the severity of the disease, the fracture history and the number of joint and muscle bleedings. Boys with haemophilia had a decreased trabecular volumetric BMD (mean Z-score -0.5, P < 0.01), while their cortical volumetric BMD was increased (mean Z-score 0.4, P < 0.05). The volumetric bone mineral content and the bone geometry at the radial diaphysis were normal when adjusted for patients' shorter body height. Muscle area was decreased (mean Z-score -1.0, P < 0.001), irrespective of age. No association was observed of bone quality parameters and bone geometry with the disease severity, fracture history or number of bleedings. Bone strength measured at the diaphysis of the radius is not impaired in boys with haemophilia. The finding of the decreased trabecular bone density can be most likely attributed to their sarcopenia.