More broken bones: a 4-year double cohort study of young girls with and without distal forearm fractures

Systematic review of effectiveness of bisphosphonates in treatment of low bone mineral density and fragility fractures in juvenile idiopathic arthritis

AIMS

To evaluate the currently available evidence for the effectiveness of bisphosphonates in children with low bone mineral density (BMD) and fragility fractures associated with juvenile idiopathic arthritis (JIA), and the safety of bisphosphonates in JIA and other conditions.

METHODS

Literature databases were searched using a structured search strategy. The effectiveness review included any studies of children with JIA treated with bisphosphonates. The safety review also included studies of osteogenesis imperfecta. Quantitative data analysis was not undertaken because of the heterogeneity of the studies; findings were summarised using tables and narrative synthesis.

RESULTS

Ninety four studies were identified. Sixteen studies (78 JIA children) were included in the effectiveness review: one randomised controlled trial, three controlled cohort studies, 11 case series, and one case report. At baseline, children had low BMD below the expected values for age and sex matched children. In all studies, treatment with bisphosphonates increased BMD compared with baseline: the mean percentage increase in spine BMD ranged from 4.5% to 19.1%. Overall, studies were heterogeneous and of variable quality. A total of 59 papers were included in the safety review; treatment durations were up to three years. The most common side effect was a flu-like reaction with intravenous treatment. This occurred during the first infusion and was transient; the symptoms were managed with paracetamol and did not occur during subsequent cycles.

CONCLUSIONS

Bisphosphonates are a promising treatment for low BMD and fragility fractures in children with JIA. However, the quality of the current evidence is variable and better studies are needed to more clearly assess their role.

A genetic approach to fracture epidemiology in childhood

The purpose of this report is to provide a review of both childhood fracture epidemiology and known heritable causes for fracture predisposition to the Medical Geneticist, who is frequently consulted to assess children with multiple or unexplained fractures for a physiologic etiology. A detailed knowledge of the clinical and laboratory evaluation for osteogenesis imperfecta (OI) and other single-gene disorders is obviously essential to complete a useful evaluation of such children. The experienced clinician will immediately recognize that single gene disorders represent only a small fraction of these patients. In infants, non-accidental trauma (NAT) unfortunately is the likely explanation for the fracture pattern, but in some infants, and certainly in older children with recurrent fractures, no medical explanations can be found. Recent studies in which bone mineral density (BMD) has been associated with genetic variation at a number of candidate genes are promising but these studies are too premature yet to be used clinically. Nonetheless, we do expect that in the future whole-genome approaches in conjunction with key clinical and epidemiological variables may be combined through an informatics approach to create better predictors of fracture susceptibility for these populations of patients.

Musculoskeletal disorders associated with obesity: a biomechanical perspective

Despite the multifactorial nature of musculoskeletal disease, obesity consistently emerges as a key and potentially modifiable risk factor in the onset and progression of musculoskeletal conditions of the hip, knee, ankle, foot and shoulder. To date, the majority of research has focused on the impact of obesity on bone and joint disorders, such as the risk of fracture and osteoarthritis. However, emerging evidence indicates that obesity may also have a profound effect on soft-tissue structures, such as tendon, fascia and cartilage. Although the mechanism remains unclear, the functional and structural limitations imposed by the additional loading of the locomotor system in obesity have been almost universally accepted to produce aberrant mechanics during locomotor tasks, thereby unduly raising stress within connective-tissue structures and the potential for musculoskeletal injury. While such mechanical theories abound, there is surprisingly little scientific evidence directly linking musculoskeletal injury to altered biomechanics in the obese. For the most part, even the biomechanical effects of obesity on the locomotor system remain unknown. Given the global increase in obesity and the rapid rise in musculoskeletal disorders, there is a need to determine the physical consequences of continued repetitive loading of major structures of the locomotor system in the obese and to establish how obesity may interact with other factors to potentially increase the risk of musculoskeletal disease.

Childhood onset arthritis is associated with an increased risk of fracture: a population based study using the General Practice Research Database

BACKGROUND

Childhood onset arthritis is associated with low bone mass and strength.

OBJECTIVE

To determine whether childhood onset arthritis is associated with greater fracture risk.

METHODS

In a retrospective cohort study all subjects with onset of arthritis between 1 and 19 years of age in the United Kingdom General Practice Research Database were identified. As controls, all sex and age matched subjects from a practice that included a subject with arthritis were included. Incidence rate ratios (IRRs) for first fracture were generated using Mantel-Haenszel methods and Poisson regression.

RESULTS

1939 subjects with arthritis (51% female) and 207 072 controls (53% female) were identified. The median age at arthritis diagnosis was 10.9 years. A total of 129 (6.7%) first fractures were noted in subjects with arthritis compared with 6910 (3.3%) in controls over a median follow up of 3.90 and 3.95 years in the subjects with arthritis and controls, respectively. The IRR (95% confidence interval) for first fracture among subjects with arthritis, compared with controls, according to the age at the start of follow up were 1.49 (0.91 to 2.31) for age <10 years, 3.13 (2.21 to 4.33) at 10-15 years, 1.75 (1.18 to 2.51) at 15-20 years, 1.40 (0.91 to 2.08) at 20-45 years, and 3.97 (2.23 to 6.59) at >45 years.

CONCLUSIONS

Childhood onset arthritis is associated with a clinically significant increased risk of fracture in children, adolescents and, possibly, adults. Studies are urgently needed to characterise the determinants of structural bone abnormalities in childhood arthritis and devise prevention and treatment strategies.

Measuring bone mass in children: can we really do it?

Bone densitometry is used to assess skeletal health in clinical and research settings, with the goal of achieving reproducible measurements of bone mass that help to identify individuals predisposed to fracture. The search is now on for better methods of capturing additional factors that contribute to bone strength, including bone size, geometry, microarchitecture, and turnover rates. This has proved particularly challenging in growing children, whose bones continually change in size, shape, and mass. Dual energy X-ray absorptiometry is the preferred method for measuring bone mass in children, but the technique has several limitations, and interpreting the findings can be problematic. Peripheral quantitative computed tomography is a promising method for assessing bone mass and other indices correlating with bone strength, but a lack of precision and paediatric norms currently restricts its clinical utility. Although bone mineral density is predictive of future fracture risk in adults, the evidence in children is less conclusive, and a diagnosis of osteoporosis in a child should not be made on densitometric findings alone. Developing a clearer understanding of how measures of bone mass and strength correlate with bone fracture in children will help target preventive strategies for those in greatest need.

Adipose tissue stimulates bone growth in prepubertal children

CONTEXT

Fat mass represents a positive influence on bone mass in adults, independently of other factors such as lean mass, but whether a similar action occurs in children is unclear.

OBJECTIVE

Our objective was to examine the relationship between fat mass and bone mass in children.

DESIGN AND SETTING

We conducted combined cross-sectional and prospective analyses at university research clinics.

PARTICIPANTS

Participants included children aged 9.9 yr from a large population-based birth cohort in southwest England.

OUTCOMES

Relationships between total body fat mass were measured by dual-energy x-ray absorptiometry at age 9.9 yr, and 1) total-body-less-head bone mass and area at age 9.9 and 2) increase in bone mass and area over the following 2 yr.

RESULTS

There was a strong positive relationship between total body fat mass and total-body-less-head bone mass and area, even after adjustment for height and/or lean mass (P < 0.001). There was a similar positive association between total body fat mass and increase in bone mass and area over the following 2 yr in boys and Tanner stage 1 girls. In contrast, no association was present between fat mass and gain in bone mass and size in Tanner stage 2 girls, whereas a negative association was seen in Tanner stage 3 girls (puberty-fat mass interaction, P < 0.001).

CONCLUSIONS

In prepubertal children, fat mass is a positive independent determinant of bone mass and size and of increases in these parameters over the following 2 yr, suggesting that adipose tissue acts to stimulate bone growth. However, this relationship is attenuated by puberty.

The impact of childhood obesity on musculoskeletal form

Despite the greater prevalence of musculoskeletal disorders in obese adults, the consequences of childhood obesity on the development and function of the musculoskeletal system have received comparatively little attention within the literature. Of the limited number of studies performed to date, the majority have focused on the impact of childhood obesity on skeletal structure and alignment, and to a lesser extent its influence on clinical tests of motor performance including muscular strength, balance and locomotion. Although collectively these studies imply that the functional and structural limitations imposed by obesity may result in aberrant lower limb mechanics and the potential for musculoskeletal injury, empirical verification is currently lacking. The delineation of the effects of childhood obesity on musculoskeletal structure in terms of mass, adiposity, anthropometry, metabolic effects and physical inactivity, or their combination, has not been established. More specifically, there is a lack of research regarding the effect of childhood obesity on the properties of connective tissue structures, such as tendons and ligaments. Given the global increase in childhood obesity, there is a need to ascertain the consequences of persistent obesity on musculoskeletal structure and function. A better understanding of the implications of childhood obesity on the development and function of the musculoskeletal system would assist in the provision of more meaningful support in the prevention, treatment and management of the musculoskeletal consequences of the condition.

Sex difference in the effect of puberty on the relationship between fat mass and bone mass in 926 healthy subjects, 6 to 18 years old

OBJECTIVE

Understanding factors influencing bone mineral accrual is critical to optimize peak bone mass during childhood. The epidemic of pediatric obesity and reported higher incident of fracture risk in obese children led us to study the influence of fat mass on bone mineral content (BMC) in children.

RESEARCH METHODS AND PROCEDURES

Height; weight; pubertal stage; and BMC, non-bone fat-free mass (nbFFM), and fat mass (FM) by DXA were obtained in a multiethnic group of healthy children (444 girls/482 boys; 6 to 18 years old) recruited in the New York metropolitan area. Regression techniques were used to explore the relationship between BMC and FM, with age, height, nbFFM, pubertal stage, sex, and ethnicity as covariates.

RESULTS

Because there were significant sex interactions, separate regression analyses were performed for girls and boys. Although ln(nbFFM) was the greatest predictor of ln(BMC), ln(FM) was also a significant predictor in prepubertal boys and all girls but not in pubertal boys. This effect was independent of ethnicity.

DISCUSSION

FM was a determinant of BMC in all girls but in only prepubertal boys. Our study confirms nbFFM as the greatest predictor of BMC but is the first to find a sex difference in the effect of puberty on the relationship of FM to BMC. Our results suggest that, in two individuals of the same sex and weight, the one with greater fat mass will have lower BMC, especially pubertal boys. The implications of these findings for achievement of optimal peak bone mass in a pediatric population with an unprecedented incidence of overweight and "overfat" status remain to be seen.

Childhood fractures are associated with decreased bone mass gain during puberty: an early marker of persistent bone fragility?

Whether peak bone mass is low among children with fractures remains uncertain. In a cohort of 125 girls followed over 8.5 years, 42 subjects reported 58 fractures. Among those, BMC gain at multiple sites and vertebral bone size at pubertal maturity were significantly decreased. Hence, childhood fractures may be markers of low peak bone mass acquisition and persistent skeletal fragility.

INTRODUCTION

Fractures in childhood may result from a deficit in bone mass accrual during rapid longitudinal growth. Whether low bone mass persists beyond this period however remains unknown.

MATERIALS AND METHODS

BMC at the spine, radius, hip, and femur diaphysis was prospectively measured over 8.5 years in 125 girls using DXA. Differences in bone mass and size between girls with and without fractures were analyzed using nonparametric tests. The contribution of genetic factors was evaluated by mother-daughter correlations and that of calcium intake by Cox proportional hazard models.

RESULTS

Fifty-eight fractures occurred in 42 among 125 girls (cumulative incidence, 46.4%), one-half of all fractures affecting the forearm and wrist. Girls with and without fractures had similar age, height, weight. and calcium intake at all time-points. Before and during early puberty, BMC and width of the radius diaphysis was lower in the fracture compared with no-fracture group (p < 0.05), whereas aBMD and BMAD were similar in the two groups. At pubertal maturity (Tanner's stage 5, mean age +/- SD, 16.4 +/- 0.5 years), BMC at the ultradistal radius (UD Rad.), femur trochanter, and lumbar spine (LS), and LS projected bone area were all significantly lower in girls with fractures. Throughout puberty, BMC gain at these sites was also decreased in the fracture group (LS, -8.0%, p = 0.015; UD Rad., -12.0%, p = 0.004; trochanter, -8.4%, p = 0.05 versus no fractures). BMC was highly correlated between prepuberty and pubertal maturity (R = 0.54-0.81) and between mature daughters and their mothers (R = 0.32-0.46). Calcium intake was not related to fracture risk.

CONCLUSIONS

Girls with fractures have decreased bone mass gain in the axial and appendicular skeleton and reduced vertebral bone size when reaching pubertal maturity. Taken together with the evidence of tracking and heritability for BMC, these observations indicate that childhood fractures may be markers for low peak bone mass and persistent bone fragility.

How to manage osteoporosis in children

Osteoporosis is increasingly being seen in young people. The primitive forms are relatively rare, but the secondary forms--particularly in long-term corticosteroid therapy--are a relevant problem given the much longer survival in chronic diseases such as cystic fibrosis, chronic renal insufficiency, leukaemia, and Duchenne muscular dystrophy. Controlled, prospective studies to evaluate the results of prevention and therapy in children are still lacking. The basis of therapy is the correct daily intake of calcium and the use of vitamin D (or active metabolites). This helps the growing skeleton to restore its equilibrium in many cases. Restraining the long-term use of corticosteroids to the minimum effective dose and shorter duration is essential. In severe cases, particularly in the presence of fractures, bisphosphonates can be remarkably effective. In some cases, such as idiopathic juvenile osteoporosis, the rule is spontaneous resolution, and the advisability of an aggressive drug therapy is discussed.

Association between bone density and fractures in children: a systematic review and meta-analysis

OBJECTIVE

The objective of this article was to systematically review all published studies that investigated the association between bone density and fractures in children.

DESIGN

Potentially relevant articles were identified by searching electronic databases. Duplicates were removed, abstracts were inspected, and relevant articles were obtained. Studies were included in the systematic review if participants were <16.0 years old, were healthy, had extractable data on bone mass, and had fractures as the outcome.

RESULTS

Ten case-control studies were identified. No prospective studies were found. There was no evidence of heterogeneity between studies or of funnel-plot asymmetry. Eight of the studies were included in the meta-analysis, because they presented results as means and standard deviations of bone density in cases and controls. The pooled standardized mean difference for bone mass in children with and without fractures, from a fixed-effects model, was -0.32 (95% confidence interval: -0.43 to -0.21).

CONCLUSIONS

Evidence for an association between bone density and fractures in children is limited. The results from this meta-analysis suggest that there is an association between low bone density and fractures in children. Although there was no evidence of heterogeneity or publication bias, this meta-analysis is based on case-control studies that are prone to bias. Large, well-conducted prospective cohort studies are required to confirm the association between bone density and fractures in children.

Children who experience their first fracture at a young age have high rates of fracture

Rate of fracture was examined according to age at first fracture in 313 New Zealand children (145 girls, 168 boys) under l3 years of age (95.4% of a consecutive series of children treated at one hospital for a recent confirmed fracture at any site). In their lifetimes they had experienced 468 separate fracture events, over half (54.7%) occurring in the 32.3% of children breaking bones on more than one occasion. Children experiencing a first fracture before 4 years of age had 36.7 (95%CI 30.7-44.1) fractures per l00 years of exposure: this was a significantly higher rate than that of children experiencing their first fracture later in life. Thus, using the <4.0 year age group as a reference, we found that rate ratios (adjusted for gender) for groups that had suffered the first fracture at later ages were: first fracture between 4.0 and 6.99 years, 0.77 (95%CI 0.58-1.03); first fracture between 7.0 and 9.99 years, 0.63 (95%CI 0.42-0.94); first fracture between 10.0 and 12.99 years, 0.48 (95% CI 0.32-0.72). Asthma was over-represented (31% seen, 25% expected), and a high proportion of the sample (32.9%) used corticosteroid medications; however, neither characteristic affected age at first fracture. In contrast, the large number (n= 42) of youngsters (13.4% of the sample) reporting adverse reactions to milk were younger at first fracture than children without reactions to milk (P<0.05). We conclude that children experiencing their first fracture at a young age have high rates of fracture and should be targeted for advice to improve their bone strength.

Optimizing bone health and calcium intakes of infants, children, and adolescents

Most older children and adolescents in the United States currently do not achieve the recommended intake of calcium. Maintaining adequate calcium intake during childhood and adolescence is necessary for the development of peak bone mass, which may be important in reducing the risk of fractures and osteoporosis later in life. Optimal calcium intake is especially relevant during adolescence, when most bone mineral accretion occurs. Because of the influence of the family's diet on the diet of children and adolescents, adequate calcium intake by all members of the family is important. Assessment of calcium intake can be performed in the physician's office. A well-rounded diet including low-fat dairy products, fruits, and vegetables and appropriate physical activity are important for achieving good bone health. Establishing these practices in childhood is important so that they will be followed throughout the life span.

Osteoporosis in children and adolescents: etiology and management

Bone mass increases progressively during childhood, but mainly during adolescence when approximately 40% of total bone mass is accumulated. Peak bone mass is reached in late adolescence, and is a well recognised risk factor for osteoporosis later in life. Thus, increasing peak bone mass can prevent osteoporosis. The critical interpretation of bone mass measurements is a crucial factor for the diagnosis of osteopenia/osteoporosis in children and adolescents. To date, there are insufficient data to formally define osteopenia/osteoporosis in this patient group, and the guidelines used for adult patients are not applicable. In males and females aged <20 years the terminology 'low bone density for chronologic age' may be used if the Z-score is less than -2. For children and adolescents, this terminology is more appropriate than osteopenia/osteoporosis. Moreover, the T-score should not be used in children and adolescents. Many disorders, by various mechanisms, may affect the acquisition of bone mass during childhood and adolescence. Indeed, the number of disorders that have been identified as affecting bone mass in this age group is increasing as a consequence of the wide use of bone mass measurements. The increased survival of children and adolescents with chronic diseases or malignancies, as well as the use of some treatment regimens has resulted in an increase in the incidence of reduced bone mass in this age group. Experience in treating the various disorders associated with osteoporosis in childhood is limited at present. The first approach to osteoporosis management in children and adolescents should be aimed at treating the underlying disease. The use of bisphosphonates in children and adolescents with osteoporosis is increasing and their positive effect in improving bone mineral density is encouraging. Osteoporosis prevention is a key factor and it should begin in childhood. Pediatricians should have a fundamental role in the prevention of osteoporosis, suggesting strategies to achieve an optimal peak bone mass.

Adaptation of the Carter method to adjust lumbar spine bone mineral content for age and body size: application to children who were born preterm

In adults, the Carter method allows the separation of the lumbar spine bone mineral content (BMC) into its constituents; bone volume (BV) and volumetric density (bone mineral apparent density [BMAD]). However, this method is not widely used in pediatric studies and does not account for the effects of body habitus on bone mass. The aims of this study were to modify the Carter method for use in children by developing an approach that adjusts separately for age and body height, and to test whether lumbar spine bone mass is normal in children born who were born preterm. Twenty-five preterm-born children were matched to a term-born child. Lumbar spine bone mass was measured using dual-energy X-ray absorptiometry. The BV and BMAD were calculated. Z-scores based on age and height were calculated. The preterm group had reduced absolute height, weight, BMC, BV, and BMAD, and reduced height, weight, and BMC for their age. The BMC was appropriate for height. The BV was appropriate for age. The BMAD was reduced for age but appropriate for height. In preterm children, the major abnormality at the lumbar spine is a decrease in volumetric density; however, this decrease is proportional with their reduced stature, and we speculate that there is no reduction in the strength of the lumbar spine.

Effects of long-term calcium intake on body weight, body fat and bone in growing rats

Increased calcium intake may reduce body weight and fat in non-growing individuals. This study explored the long-term effects of high versus low calcium intake on body weight, body fat, BMC, BMD and bone size in growing male and female rats. Ninety male and 90 female Sprague-Dawley rats were randomly assigned either to a high calcium (1%) or low calcium (0.25%) diet from age 3 weeks until 40 weeks. Half of the animals were fed ad libitum, and half of the animals were on an adjusted feeding schedule (the food intake of the low calcium animals was reduced to maintain equal body weight with high calcium animals of the same gender). DXA and radiographic measurements (femur and skull length and width) were collected at the age of 4, 13 and 34 weeks. Growing male rats fed the low calcium diet ad libitum gained more weight and more fat than rats on a high calcium diet. When food intake was controlled, male rats on the low calcium diet still had a greater fat mass (despite their similar body weight) and smaller skeletal measurements than the high calcium animals. Growing female rats initially responded like the males: when fed ad libitum low calcium animals had an increased body weight and fat mass; when food intake was controlled the low calcium animals had a greater fat mass and smaller skeletal measurements. However, these differences were found at 13 weeks and not at 34 weeks, suggesting a transient effect with no long-term differences between high and low calcium intake in the growing female rats.

Comparison of phalangeal ultrasound and dual energy X-ray absorptiometry in healthy male and female adolescents

The aims of this study were to determine if there is a correlation between dual energy X-ray absorptiometry (DXA) and phalangeal quantitative ultrasound (QUS) in identifying children and adolescents with low bone density, and to assess if body size influences the results of the two techniques to the same degree. Measurements were performed in 67 girls and 83 boys aged 14 to 19 y using DBM Sonic 1200 (IGEA, Carpi, Italy) and the DXA equipment (LUNAR Radiation Corp., Madison, WI, USA). Twelve adolescents (eight males and four females) reported a past history of nonosteoporotic fractures. Lumbar spine bone mineral density (LS BMD), total body bone mineral density (TB BMD) and total body bone mineral content (TB BMC) correlated positively with age, height, BMI and weight, in both genders. Amplitude-dependent speed of sound (Ad-SOS) was positively correlated with age, height and Tanner stages in both genders and negatively correlated with BMI in females. TB BMD, TB BMC and LS BMD positively correlated with Ad-SOS only in males. In females, there were no significant correlations between Ad-SOS, TB BMD, TB BMC and LS BMD measurements. Twelve teenagers with previous fractures (high impact fractures) were found to have lower DXA and QUS values than age-matched teenagers without fractures but the statistical significance was found only in relation to TB BMD values (p = 0.02). In conclusion, we obtained results similar to those that have been reported by other authors using different QUS techniques. Furthermore, the Ad-SOS measurements taken at the distal metaphysis of the proximal phalanges correlate poorly with LS BMD and TB BMD measured by DXA in growing subjects.

Bone and body composition of children and adolescents with repeated forearm fractures

DXA measurements in 90 children and adolescents with repeated forearm fractures showed reduced ultradistal radius BMC and BMD values and elevated adiposity, suggesting site-specific bone weakness and high body weight increase fracture risk. Symptoms to cow milk, low calcium intakes, early age of first fracture, and overweight were over-represented in the sample.

INTRODUCTION

Although many apparently healthy children fracture their forearms repeatedly during growth, no previous studies of their bone health and body composition have been undertaken. Nor has the prevalence of established risk factors for fracture in such a population been assessed.

MATERIALS AND METHODS

Ninety children and adolescents (47 girls and 43 boys) 5-19 years of age, who had experienced at least two fractures of the forearm, were studied. Bone size and mineralization were assessed using DXA at the ultradistal radius, one-third radius, neck of femur, hip trochanter, lumbar spine, and total body. Total body lean mass and fat mass were also determined. The prevalence of six risk factors for fracture were also examined, and their influence on ultradistal BMC Z scores was assessed.

RESULTS

Participants experienced 295 fractures (74.9% forearm). Children with an early age of first fracture had higher rates of fracture per l00 years of exposure than those fracturing later. Four risk factors for fracture were over-represented in observed versus expected percentages: early age of first fracture (27.7% versus 11.3%), adverse symptoms to cow milk (22.2% versus 6.7%), low dietary calcium intake (20% versus 4.5%), and overweight (33.3% versus 15.5%). However, physical activity levels were similar to the reference population. Z scores for BMC and BMD were reduced, particularly at the ultradistal radius, whereas Z scores for weight, body mass index, fat mass, and body fat percentage were increased. Mean (SD) BMC Z scores were lowest at the ultradistal radius, -0.66 (1.22), where symptoms to milk were associated with reduced values (p < 0.009) and overweight with increased values (p < 0.003).

CONCLUSIONS

Our results suggest site-specific weakness and high body weight contribute to fracture risk in children and adolescents who fracture their forearms repeatedly. These findings are consonant with work showing adult Colles fractures increase as ultradistal radius BMD falls and with evidence that overweight children and adolescents are fracture prone.

The characteristics of fractures in Polish adolescents aged 16-20 years

The aim of the study was to identify associations between fractures in childhood and family, anthropometric and lifestyle factors. Among 1,246 subjects aged 16.3-20.6 years (539 boys, 707 girls), based on a questionnaire, 869 were fracture-free while 377 (30.26%) had fractures. Of those reporting fractures, 146 reported multiple fractures (12% of studied population, 39% of all fractures). More boys had fractures than girls (35.6% vs 24.9%, p < 0.001). Fracture sites included: forearm (37%), fingers (23%) wrist (16%), ankle (14%), humerus (10%), tibia (8%) clavicle (7%) and femoral shaft / neck (3%). Among adolescents with multiple fractures, 52% also reported fractures in at least one family member, compared with 29% of those without a fracture history. Fractures in siblings and mothers (but not fathers) accounted for 44% of the liability in adolescents' fractures. Subjects with multiple fractures reported more time at the computer than those without fractures and reported more time participating in team sports, and 18.6% avoided milk, whereas 12.4% of those without fractures reported milk-free diets. Using a logistic regression model, none of the lifestyle factors, except for computer use, were independently associated with fractures. Fractures, particularly multiple fractures, are common in childhood and adolescence. Familial clustering of fractures suggests shared genetic and environmental factors are responsible.

The relative contributions of lean tissue mass and fat mass to bone density in young women

Although obesity is associated with increased risk of many chronic diseases including cardiovascular disease, diabetes, hypertension, and cancer, there is little evidence to suggest that obesity increases risk of osteoporosis. In fact, both weight and body mass index (BMI) are positive predictors of bone mass in adults, suggesting that those who are overweight or obese may be at lower risk of osteoporosis. However, recent evidence suggests that in children and adolescents, obesity may be associated with lower rather than higher bone mass. To understand the relation of fat mass to bone mass, we examined data gathered from an ethnically diverse group of 921 young women, aged 20-25 years (317 African Americans, 154 Asians, 322 Caucasians, and 128 Latinas) to determine how fat mass (FM) as well as lean tissue mass (LTM) is associated with bone mass. Bone mass, FM, and LTM were measured using dual energy X-ray absorptiometry (GE Lunar Corp, Madison, WI). Bone mass was expressed as bone mineral density (BMD; g/cm2) and bone mineral apparent density (BMAD; g/cm3) for the spine and femoral neck, and as BMD and bone mineral content (BMC; g) for the whole body. Regression techniques were used to examine the following: (1) in separate equations, the associations of LTM and FM with each bone mass parameter; and (2) in the same equation, the independent contributions of LTM and FM to bone mass. LTM and FM were positively correlated with BMD at all skeletal sites. When the contributions of FM and LTM were examined simultaneously, both FM and LTM continued to be positively associated with bone mass parameters but the effect of FM was noted to be smaller than that of LTM. We conclude that in young women, LTM has a greater effect than fat mass on bone density per kg of tissue mass.

Two-year changes in bone and body composition in young children with a history of prolonged milk avoidance

No previous longitudinal studies of calcium intake, anthropometry and bone health in young children with a history of avoiding cow's milk have been undertaken. We report the 2-year changes of a group of 46 Caucasian children (28 girls, l8 boys) aged 8.1+/-2.0 years (mean +/- SD) who had low calcium intakes at baseline and were short in stature, with elevated body mass index, poor skeletons and lower Z scores for both areal bone mineral density (BMD, in grams per square centimeter) and volumetric density (bone mineral apparent density, BMAD, in grams per cubic centimeter), compared with a reference population of milk drinkers. At follow-up, adverse symptoms to milk had diminished and modest increases in milk consumption and calcium intake had occurred. Total body bone mineral content (BMC) and bone area assessed by dual energy X-ray absorptiometry had increased (P<0.05), and calcium intake from all sources was associated with both these measures (P<0.05). However, although some catch-up in height had taken place, the group remained significantly shorter than the reference population (Z scores -0.39+/-1.14), with elevated body mass index (Z scores 0.46+/-1.0). The ultradistal radius BMC Z scores remained low (-0.31+/-0.98). The Z scores for BMD had improved to lie within the normal range at predominantly cortical sites (33% radius, neck of femur and hip trochanter) but had worsened at predominantly trabecular sites (ultradistal radius and lumbar spine), where values lay below those of the reference group (P<0.05). Similarly, although volumetric BMAD Z scores at the 33% radius had normalized, BMAD Z scores at the lumbar spine remained below the reference population at follow-up (-0.67+/-1.12, P<0.001). Our results demonstrate persisting height reduction, overweight and osteopenia at the ultradistal radius and lumbar spine in young milk avoiders over 2 years of follow-up.

Osteoporosis and measurement of bone mass in children and adolescents

Osteoporosis increasingly is recognized as a pediatric concern. Fragility fractures occur in children and adolescents with genetic disorders and those with a variety of chronic diseases. Others may not fracture in childhood but reach adulthood with a reduced peak bone mass and increased lifelong risk of osteoporosis. This article reviews the indications for pediatric bone density testing, the strengths and limitations of densitometry methods, and the challenges of interpreting the results. The goals are to demystify the densitometry report and to clarify the role of bone density tests in assessing and managing skeletal health in children.

Bone mass acquisition in healthy children

Although 80% of the variance in bone mass is determined genetically, there are many other factors which influence the accumulation of bone in early life and affect future risks of osteoporosis. This review considers the genetic, fetal, and environmental influences on bone mass acquisition in healthy children, and highlights important areas where paediatricians may have a role by counselling children and their families to adopt a healthy lifestyle which promotes bone health.

Adverse effects of antiretroviral therapy: focus on bone density

Osteopenia and osteoporosis are the most important bone disorders affecting patients with HIV infection. The available data indicate that HIV-infected patients have a high prevalence of low bone mineral density. Reduced bone mass and alterations of bone metabolism have been found in HIV-infected children, adolescents and adults. The variety and complexity of changes in bone metabolism in patients with HIV infection and the different possible mechanisms triggering bone mineral loss, as well as the different stages of disease and cumulative exposure to antiretroviral drugs at the time of clinical evaluation, may contribute to the wide range of mineral loss observed and to the uncertainty of the role of specific antiretroviral medications.

Assessment of bone mass following renal transplantation in children

Throughout childhood and adolescence, skeletal growth results in site-specific increases in trabecular and cortical dimensions and density. Childhood osteoporosis can be defined as a skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture. Pediatric renal transplant recipients have multiple risk factors for impaired bone density and bone strength, including pre-existing renal osteodystrophy, delayed growth and development, malnutrition, decreased weight-bearing activity, inflammation, and immunosuppressive therapies. Dual energy X-ray absorptiometry (DXA) is the most-common method for the assessment of skeletal status in children and adults. However, DXA has many important limitations that are unique to the assessment of bone health in children. Furthermore, DXA is limited in its ability to distinguish between the distinct, and sometimes opposing, effects of renal disease on cortical and trabecular bone. This review summarizes these limitations and the difficulties in assessing and interpreting bone measures in pediatric transplantation are highlighted in a review of select studies. Alternative strategies are presented for clinical and research applications.

(n-3) fatty acids reduce the release of prostaglandin E2 from bone but do not affect bone mass in obese (fa/fa) and lean Zucker rats

Childhood obesity is prevalent and linked to the development of Type 2 diabetes mellitus (DM) and poor bone health. Some PUFA enhance bone mass and thus may improve bone health in obese children. The study objective was to determine the effects of dietary (n-6) compared with (n-3) essential PUFA and long-chain PUFA (LCPUFA) on bone in an obese and insulin-resistant state. Male fa/fa (n = 48) and lean Zucker rats (n = 48) were fed diets containing safflower oil [SO, high (n-6) PUFA], flaxseed oil [FXO, high (n-3) PUFA], or menhaden oil [MO, high (n-3) LCPUFA] for 9 wk. Measurements included the following: femur bone area (BA), mineral content (BMC), density (BMD), morphometry and ex vivo release of prostaglandin E(2) (PGE(2)); plasma osteocalcin and C-terminal telopeptides of type I collagen. Differences among groups were detected using 2-way ANOVA. Genotype effects in the fa/fa rats included lower femoral weight, length, BA, and BMC, as well as femoral head and proximal epiphysis widths compared with the lean rats, but BMD was not affected. Femur BA, BMC, and BMD did not differ among the dietary groups, but diaphysis width was elevated in the MO group and PGE(2) release was reduced by the FXO and MO diets. No genotype x diet interactions were observed. These data indicate that the fa/fa Zucker rat is at risk for low bone mass and that dietary (n-3) FA effectively reduce PGE(2) release. Whether reduced PGE(2) will support optimal peak bone mass during childhood and conserve bone mass with aging warrants investigation.

Proximal femur bone geometry is appropriately adapted to lean mass in overweight children and adolescents

It is unclear if the bones of overweight children are appropriately adapted to increased loads. The objective of this study was to compare bone geometry in 40 overweight (body mass index [BMI] > 85th percentile) and 94 healthy weight (BMI < or = 85th percentile) subjects, ages 4-20 years. Dual energy X-ray absorptiometry (Hologic QDR 2000) scans were analyzed at the femoral shaft (FS) and narrow neck (NN) by the Hip Structure Analysis program. Subperiosteal width, cortical thickness and indices of bone axial and bending strength (bone cross-sectional area [CSA] and section modulus [Z]) were measured from bone mass profiles. Multivariate regression models were used to compare overweight and healthy weight subjects. Z was 11 (95% CI 5, 19) and 13 (7, 20) percent higher at the FS and NN, respectively, in overweight subjects (P < 0.001), adjusted for height, maturation and gender. At the NN, higher Z was due to greater subperiosteal width [4% (2, 7)] and bone CSA [10% (5, 16]) and at the FS, to higher bone CSA [10% (5, 16)] and thicker cortices [9% (3, 15)]. When lean mass was added to the models, bone variables did not differ between overweight and healthy weight subjects (P > 0.22), with the exception of NN subperiosteal width [3% (0, 6), P = 0.04]. Fat mass did not contribute significantly to any model. In summary, proximal femur bone geometric strength in overweight children was appropriately adapted to lean mass and height but greater weight in the form of fat mass did not have an independent effect on bone bending strength. These geometric adaptations are consistent with the mechanostat hypothesis that bone strength adapts primarily to muscle forces, not to static loads represented by body weight.

First fracture is associated with increased risk of new fractures during growth

Prior fracture was associated with increased risk of new fracture in 601 members of a cohort studied between birth and l8 years. Hazard ratios for new fracture in data adjusted for age and sex were l.90 (95%CI l.51-2.39) after first fracture and 3.04 (95% CI 2.23-4.15) after second fracture.

Premenopausal bone health assessment

The World Health Organization criteria for classification of bone mineral density (BMD) cannot be applied to premenopausal women because the relationship between BMD and fracture risk is not the same as in postmenopausal women. Approximately 2.5% of premenopausal women have BMD that is more than 2.0 standard deviations below the mean BMD of an age-, gender-, and ethnicity-matched reference population. Most premenopausal women with low BMD have low peak bone mass and low 5- to 10-year probability of fracture. The management of these patients involves nonpharmacologic lifestyle measures and reassurances that fracture risk is low. A minority of premenopausal women with low BMD have significant elevation of fracture risk, usually a result of contributing diseases, conditions, or medications that may be identified and treated. Premenopausal women with fractures are at increased risk for postmenopausal osteoporosis and fractures later in life.

Bone density at the os calcis: reference values, reproducibility, and effects of fracture history and physical activity

AIMS

To establish reference values for bone mineral density (BMD) measured at the os calcis (OC) in healthy UK Caucasian children. Secondary objectives were to assess the reproducibility of the measurement and the effects of fracture history and habitual physical activity.

METHODS

A total of 403 children aged 5-18 were studied. Main outcome measures were: BMDoc measured by peripheral DXA, total BMD measured by whole body axial scanner, age, anthropometry, pubertal status, self-reported fracture history, and physical activity (PA) expressed as a three point score.

RESULTS

Complete data were available on 171 girls and 123 boys free of a history of fracture. BMDoc was related positively to age, body size, and total BMD, and could be predicted using a proportional model based on height alone (R2: 65% girls, 77% boys). Mean BMDoc appears to plateau in girls at 15 years and attain a value that concurs with the mean peak value in adult women. The 95% limits of agreement in repeated measures were -0.029 to 0.029 g/cm2 (n = 53). Compared with sedentary children, those doing regular sports or PA for more than five hours a week had an increased BMDoc (by about 0.03 g/cm2 or about 7% of the overall mean). A history of fracture (n = 81) was associated with a reduced BMDoc in boys but not in girls, though our study may have been underpowered for a subgroup analysis.

CONCLUSIONS

BMDoc can be measured easily and quickly in children older than 5 years and provides an objective measure of areal bone density for clinical and research studies using a reference range derived from its relation to height.

Stochastic-rheological simulation of free-fall arm impact in children: application to playground injuries

The aim of this study was to develop and pilot a stochastic-rheological biomechanical model to investigate the mechanics of impact fractures in the upper limbs of children who fall in everyday situations, such as when playing on playground equipment. The rheological aspect of the model characterises musculo-skeletal tissues in terms of inertial, elastic and viscous parameters. The stochastic aspect of the model allows natural variation of children's musculo-skeletal mechanical properties to be accounted for in the analysis. The relationship of risk factors, such as fall height, impact surface, child mass and bone density, to the probability of sustaining an injury in playground equipment falls were examined and found to closely match findings in epidemiological, clinical and biomechanical literature. These results suggest that the stochastic-rheological model is a useful tool for the evaluation of arm fracture risk in children. Once fully developed, information from this model will provide the basis for recommendations for modifications to playground equipment and surface standards.

Are inhaled corticosteroids associated with an increased risk of fracture in children?

Inhaled corticosteroids are widely used in the long-term management of asthma in children. Data on the relationship between inhaled corticosteroid therapy and osteoporotic fracture are inconsistent. We address this issue in a large population-based cohort of children aged 4-17 years in the UK (the General Practice Research Database). The incidence rates of fracture among children aged 4-17 years taking inhaled corticosteroids (n=97,387), taking bronchodilators only (n=70 984) and a reference group (n=345,758) were estimated. Each child with a non-vertebral fracture (n=23,984) was subsequently matched by age, sex, practice, and calendar time to one child without a fracture. Fracture incidence was increased in children using inhaled corticosteroids, as well as in those receiving bronchodilators alone. With an average daily beclomethasone dose of 200 microg or less, the crude fracture risk relative to nonusers was 1.10 [95% confidence interval (CI), 0.96-1.26]; with dosage of 201-400 microg, it was 1.23 (95% CI, 1.08-1.39); and with dosages over 400 microg, it was 1.36 (95% CI, 1.11-1.67). This excess risk disappeared after adjustment for indicators of asthma severity. The increased risk of fracture associated with use of inhaled corticosteroids is likely to be the result of the underlying illness, rather than being directly attributable to inhaled corticosteroid therapy.

Girls on a high-calcium diet gain weight at the same rate as girls on a normal diet: A pilot study

OBJECTIVE

To determine whether pubertal girls assigned to calcium-rich diets or their usual calcium intakes differ significantly in weight gain.

DESIGN

This is a pilot study conducted on data from an experimental research project.

SUBJECTS/SETTING

The sample included 59 girls, 9 years of age, from Omaha metropolitan communities.

INTERVENTION

Participants were randomly assigned to a calcium-rich diet supplying at least 1,500 mg of calcium per day or their usual diet.

MAIN OUTCOME MEASURE

The outcome measure was change in weight during 2 years of study.

STATISTICAL ANALYSES

Data were analyzed using descriptive statistics, Mann-Whitney U, t tests of paired and independent samples, and analysis of covariance.

RESULTS

The girls in the calcium-rich diet group had a mean (+/-standard deviation) calcium intake of 1,656+/-191 mg/day, whereas the girls on their usual diets averaged 961+/-268 mg/day. Although the participants in the treatment group consumed nearly twice as much dietary calcium--primarily from dairy foods--they did not have greater increases in body weight, body mass index, or fat or lean mass than the control group. These findings held when the data were grouped by tertile of calcium intake. Compared with girls on their usual diets, the girls who consumed the calcium-rich diet also significantly increased their intake of essential nutrients.

CONCLUSION

We conclude that calcium-rich diets do not cause excessive weight gain in pubertal girls but do contribute positively to overall nutrition. These findings provide support for programs to promote calcium-rich diets, which are critical for attaining peak bone mass.

Growth, children, and fractures

Fractures in childhood have long been considered an unavoidable consequence of growth. Studies in recent years have documented the epidemiology of these very common fractures and have also documented considerable variation by fracture type and from country to country. There have also been a number of studies aimed at identifying risk factors particularly for the most common distal forearm fracture. These studies have consistently associated bone mineral density with these fractures. Other possible risk factors include obesity, physical inactivity, sports, cola beverages, calcium intake, risk taking, and coordination. While prospective studies are required to confirm these risk factors, accumulating evidence now suggests that a substantial proportion of fractures in children are preventable.

Low bone mineral density in premenopausal women

With the proliferation of bone densitometers, an increasing number of premenopausal women are having their bone density tested. Approximately 15% of premenopausal women have bone mineral density that is more than 1 standard deviation less than the young-adult mean, and approximately 0.6% are more than 2.5 standard deviation below young-adult mean bone density. Most premenopausal women with low bone density have low peak bone mass, stable bone density, and low short-term absolute risk of fracture. The management of these patients involves nonpharmacologic lifestyle measures and reassurances that fracture risk is low. A minority of premenopausal women with low bone density have increased short-term absolute fracture risk with contributing diseases, conditions, or medications that should be identified and treated. Premenopausal women with fractures are at increased risk for fractures later in life. Methods for evaluating these patients and selecting those who require additional care are reviewed.

Strategic approaches to osteoporosis in transplantation

Recipients of stem cell transplantation are at risk for osteopenia and osteoporosis. Longitudinal studies performed in adults have shown that significant bone demineralization occurs following myeloablative therapy and subsequent immune suppression. Among children and adolescents, cross-sectional analyses indicate that younger patients are also at risk for long-term bone toxicity. Strategies to detect and manage this disorder in pediatric SCT recipients are presented.

A randomised controlled trial of standing programme on bone mineral density in non-ambulant children with cerebral palsy

BACKGROUND

Severely disabled children with cerebral palsy (CP) are prone to low trauma fractures, which are associated with reduced bone mineral density.

AIMS

To determine whether participation in 50% longer periods of standing (in either upright or semi-prone standing frames) would lead to an increase in the vertebral and proximal tibial volumetric trabecular bone mineral density (vTBMD) of non-ambulant children with CP.

METHODS

A heterogeneous group of 26 pre-pubertal children with CP (14 boys, 12 girls; age 4.3-10.8 years) participated in this randomised controlled trial. Subjects were matched into pairs using baseline vertebral vTBMD standard deviation scores. Children within the pairs were randomly allocated to either intervention (50% increase in the regular standing duration) or control (no increase in the regular standing duration) groups. Pre- and post-trial vertebral and proximal tibial vTBMD was measured by quantitative computed tomography (QCT).

RESULTS

The median standing duration was 80.5% (9.5-102%) and 140.6% (108.7-152.2%) of the baseline standing duration in the control group and intervention group respectively. The mean vertebral vTBMD in the intervention group showed an increase of 8.16 mg/cm3 representing a 6% mean increase in vertebral vTBMD. No change was observed in the mean proximal tibial vTBMD.

CONCLUSION

A longer period of standing in non-ambulant children with CP improves vertebral but not proximal tibial vTBMD. Such an intervention might reduce the risk of vertebral fractures but is unlikely to reduce the risk of lower limb fractures in children with CP.

Children who avoid drinking cow’s milk are at increased risk for prepubertal bone fractures

The full fracture histories of 50 children (30 girls and 20 boys, age range 3 to 13 years) who had avoided drinking cow's milk for prolonged periods were compared with those in a birth cohort of more than 1,000 children from the same city. Children who avoided milk did not use calcium-rich food substitutes appropriately and had low dietary calcium intakes and low bone mineral density values. Many were overweight (22 of 50). Significantly more of the children who avoided milk reported fractures (16 observed vs 6 expected, chi(2)=31.0, P<.001, df=5). They also experienced more total fractures than the birth cohort population (22 observed vs 8 expected, chi(2)=33.6, P<.001, df=5). All of the fractures occurred before puberty, the majority (18 of 22) being associated with only slight trauma. Forearm fractures were especially common (12 fractures). We conclude that young children avoiding milk are prone to fracture.

Bone disease in pediatric rheumatologic disorders

Children with rheumatic disorders have multiple risk factors for impaired bone health, including delayed growth and development, malnutrition, decreased weight-bearing activity, inflammation, and glucocorticoid therapy. The impact of rheumatic disease during childhood may be immediate, resulting in fragility fractures, or delayed, because of suboptimal peak bone mass accrual. Recent years have seen increased interest in the effects of pediatric rheumatic disorders on bone mineralization, such as juvenile rheumatoid arthritis, systemic lupus erythematosus, and juvenile dermatomyositis. This review outlines the expected gains in bone size and mass during childhood and adolescence, and summarizes the advantages and disadvantages of available technologies for the assessment of skeletal growth and fragility in children. The varied threats to bone health in pediatric rheumatic disorders are reviewed, with emphasis on recent insights into the molecular mechanisms of inflammation-induced bone resorption. The literature assessing bone deficits and risk factors for impaired bone health in pediatric rheumatic disorders is reviewed, with consideration of the strengths and limitations of prior studies. Finally, future research directions are proposed.