Bone density interpretation and relevance in Caucasian children aged 9-17 years of age: insights from a population-based fracture study

Factors associated with low bone mineral density in Turner syndrome: a multicenter prospective observational study

Turner syndrome (TS) is associated with a high risk of fracture due to low bone mineral density (BMD). While hypogonadism is known to play a role in decreasing BMD, other factors have not been studied well. Focusing on diet, exercise, and bone metabolism markers, the present, multicentric, prospective, observational study aimed to identify factors contributing to decreased BMD in TS. In total, 48 patients with TS aged between 5 and 49 years comprising a pre-pubertal group (n = 9), a cyclical menstruation group (n = 6), and a hormone replacement therapy (HRT) group (n = 33) were enrolled. The cyclical menstruation group and the HRT group were referred to collectively as the post-pubertal group. The bone mineral apparent density (BMAD) Z-score was higher in the pre-pubertal group than in the post-pubertal group (-0.3 SD vs. -1.8 SD; p = 0.014). Within the post-pubertal group, the median BMAD Z-score was -0.2 SD in the cyclical menstruation group and -2.3 SD in the HRT group (p = 0.016). Spearman's rank correlation revealed no correlation between the BMAD Z-score and bone metabolism markers. No significant relationship was observed between the BMAD Z-score and either the vitamin D sufficiency rate or the step sufficiency rate. A negative correlation was found between BMAD Z-score and serum sclerostin in the pre-pubertal group and serum FSH in the post-pubertal group. In conclusion, the present study found no relationship between the vertebral BMAD Z-score and diet or exercise habits in TS, indicating that estrogen deficiency is the chief reason for low BMD in TS.

Reference-Class Problems Are Real: Health-Adjusted Reference Classes and Low Bone Mineral Density

Elselijn Kingma argues that Christopher Boorse's biostatistical theory (the BST) does not show how the reference classes it uses are objective and naturalistic. Recently, philosophers of medicine have attempted to rebut Kingma's concerns. I argue that these rebuttals are theoretically unconvincing, and that there are clear examples of physicians adjusting their reference classes according to their prior knowledge of health and disease. I focus on the use of age-adjusted reference classes to diagnose low bone mineral density in children. In addition to using the BST's age, sex, and species, physicians also choose to use other factors to define reference classes, such as pubertal status, bone age, body size, and muscle mass. I show that physicians calibrate the reference classes they use according to their prior knowledge of health and disease. Reference classes are also chosen for pragmatic reasons, such as to predict fragility fractures.

Diagnostic Evaluation of the Functional Muscle-Bone Unit in Children With Cerebral Palsy With and Without Low Trauma Fractures

Children and adolescents with cerebral palsy (CP) are at increased risk of low trauma fractures (LTF) due to low bone mineral content (BMC). The risk of LTFs might be overestimated by only age - and sex adjusted Z-scores for BMC because Z-score based DXA techniques do not take into account other relevant parameters like height, muscle and fat mass. This study aimed to present an update of the functional muscle-bone unit-algorithm (uFMBU-A) to evaluate bone health in children with CP in order to predict the risk of LTF taking into account the parameters sex, age, height, muscle and fat mass. We performed a monocentric retrospective analysis of 177 DXA-scans of children and adolescents with CP aged 8-19. Six of these 177 patients had sustained at least 1 LTF. Age-, sex- and size adjusted Z-scores of total body less head (TBLH)-BMC, lean body mass and fat mass were calculated. The uFMBU-A was applied to the study group and results were compared with established Z-score based DXA-measurements and algorithm based diagnostic techniques concerning the prediction of LTF risk. The uFMBU-A had the greatest diagnostic odds ratio (13.3 [95% CI 2.41; 72.9]) of the evaluated predictors with a sensitivity of 50.0% (95% CI 11.8; 88.2), specifity of 93% (95% CI 88.1; 96.3). The uFMBU-A was the most accurate method of the evaluated parameters to predict LTF in children with CP and is recommended when evaluating bone health.

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.

The impact of IGF-I, puberty and obesity on early retinopathy in children: a cross-sectional study

Background

Childhood obesity has been correlated with coronary heart disease, but the correlation with microvascular disease remains unclear. The retinal microcirculation is affected early in the process of atherosclerosis and it offers the opportunity to indirectly study the effects of obesity on small brain vessels. Insulin-like growth factor 1 (IGF-I) is involved in angiogenesis and it has a crucial role in retinal vascularization.

Methods

A single-centre cross-sectional study was performed in 268 children and adolescents (116 males; mean age 13.03 ± 1.9 years,) with overweight/obesity, in order to identify risk factors for early retinopathy.

Results

Nine patients (3.3%) showed signs of retinopathy, defined as arteriovenous crossings and/or papilledema. Body mass index and fat mass, analysed by Dual X-ray Absorptiometry, were not different in patients with or without retinopathy. Patients with retinopathy were pubertal and showed higher waist circumference (107.78 ± 15.83 versus 99.46 ± 10.85 cm; p: 0.027), waist circumference/height ratio (0.66 ± 0.07 versus 0.62 ± 0.05; p: 0.04) and IGF-I SDS (0.03 ± 1.3 versus − 0.66 ± 0.9; p: 0.04). Multivariate analysis (after correction for sex, age, family history of type 2 diabetes mellitus, obesity, cardiovascular disease, hypertension and dyslipidaemia) showed that waist circumference/height ratio and IGF-I SDS were the only variables independently correlated with the presence of retinopathy.

Conclusions

Retinal vascular changes may become evident as an early complication of overweight and obesity, even during childhood and adolescence. Relatively high levels of IGF-I during this phase may act as an additional risk factor for microvascular damage. The screening for retinopathy should be proposed to all children and adolescents with overweight/obesity.

Individualized evaluation of lumbar bone mineral density and bone mineral apparent density in children and adolescents

Lumbar spine bone mineral density (LS-BMD) assessed by dual-energy X-ray absorptiometry (DXA) is used in children to evaluate bone health. LS-BMD results in children are influenced significantly by height and BMI. An adjustment for these parameters may improve the clinical use of the method.

PURPOSE/INTRODUCTION

DXA evaluation is considered useful in children to assess bone health. For this purpose, lumbar spine bone mineral density (LS-BMD) and bone mineral apparent density (LS-BMAD) are often used. The aim of the study was to estimate the effect of height and BMI on LS-BMD and LS-BMAD in children and adolescents and to develop a method to adjust individual results for these factors.

METHODS

As part of the National Health and Nutrition Examination Survey (NHANES) study, between the years 2005 and 2010 lumbar DXA scans on randomly selected Americans from 8 to 20 years of age were carried out. From all eligible DXA scans, three major US ethnic groups were evaluated (Non-Hispanic Whites, Non-Hispanic Blacks, and Mexican Americans) for further statistical analysis. The relationship between height as well as BMI for age Z-scores and age-adjusted LS-BMD and LS-BMAD Z-scores was analyzed.

RESULTS

For the statistical analysis, the DXA scans of 1799 non-Hispanic White children (823 females), of 1696 non-Hispanic Black children (817 females), and of 1839 Mexican American children (884 females) were eligible. The statistical analysis showed that taller and heavier children had significantly (p < 0.001) higher age-adjusted LS-BMD Z-scores than shorter and lighter children. But on LS-BMAD, only BMI and not height had a significant influence.

CONCLUSIONS

LS-BMD results in children were influenced significantly by their height and BMI, the LS-BMAD results were only influenced by their BMI. For the first time, the proposed method adjusts LS-BMD and LS-BMAD to BMI. An adjustment of the LS-BMD and LS-BMAD results to these factors might improve the clinical significance of an individual result.

The Role of Overweight and Obesity on Bone Health in Korean Adolescents with a Focus on Lean and Fat Mass

As the associations between pediatric overweight/obesity and bone health remain controversial, we investigated the effects of overweight/obesity as well as lean mass (LM) and fat mass (FM) on bone parameters in adolescents. Bone parameters were evaluated using dual-energy X-ray absorptiometry (DXA) data of 982 adolescents (aged 12-19 years) from the Korea National Health and Nutrition Examination Survey (2009-2010). Z-scores for LM, FM, bone mass, bone mineral density (BMD), and bone mineral apparent density (BMAD) using Korean pediatric reference values were used for analysis. Adolescents with overweight/obesity had significantly higher bone mass and density of the total-body-less-head (TBLH), lumbar spine, and femur neck than underweight or normal-weight adolescents (P < 0.001) after adjusting for vitamin D deficiency, calcium intake, and insulin resistance in both sexes. LM was positively associated with bone parameters at all skeletal sites in both sexes (P < 0.001). FM was negatively related to TBLH BMD in boys (P = 0.018) but was positively associated to BMD and BMAD of the lumbar spine and femur neck in girls. In conclusion, overweight/obesity and LM play a positive role in bone health in adolescents. The effect of FM on bone parameters is sex- and site-specific.

Amalgamated Reference Data for Size-Adjusted Bone Densitometry Measurements in 3598 Children and Young Adults-the ALPHABET Study

The increasing use of dual-energy X-ray absorptiometry (DXA) in children has led to the need for robust reference data for interpretation of scans in daily clinical practice. Such data need to be representative of the population being studied and be "future-proofed" to software and hardware upgrades. The aim was to combine all available pediatric DXA reference data from seven UK centers to create reference curves adjusted for age, sex, ethnicity, and body size to enable clinical application, using in vivo cross-calibration and making data back and forward compatible. Seven UK sites collected data on GE Lunar or Hologic Scanners between 1996 and 2012. Males and females aged 4 to 20 years were recruited (n = 3598). The split by ethnic group was white 2887; South Asian 385; black Afro-Caribbean 286; and mixed heritage 40. Scans of the total body and lumbar spine (L₁ to L₄ ) were obtained. The European Spine Phantom was used to cross-calibrate the 7 centers and 11 scanners. Reference curves were produced for L₁ to L₄ bone mineral apparent density (BMAD) and total body less head (TBLH) and L₁ to L₄ areal bone mineral density (aBMD) for GE Lunar Prodigy and iDXA (sex- and ethnic-specific) and for Hologic (sex-specific). Regression equations for TBLH BMC were produced using stepwise linear regression. Scans of 100 children were randomly selected to test backward and forward compatibility of software versions, up to version 15.0 for GE Lunar and Apex 4.1 for Hologic. For the first time, sex- and ethnic-specific reference curves for lumbar spine BMAD, aBMD, and TBLH aBMD are provided for both GE Lunar and Hologic scanners. These curves will facilitate interpretation of DXA data in children using methods recommended in ISCD guidelines. The databases have been created to allow future updates and analysis when more definitive evidence for the best method of fracture prediction in children is agreed. © 2016 American Society for Bone and Mineral Research.

The impact of LRP5 polymorphism (rs556442) on calcium homeostasis, bone mineral density, and body composition in Iranian children

Failure to achieve optimal bone mass in childhood is the primary cause of decreased adult bone mineral density (BMD) and increased bone fragility in later life. Activating and inactivating LRP5 gene mutations has been associated with extreme bone-related phenotypes. Our aim was to investigate the role of LRP5 polymorphism on BMD, mineral biochemical parameters, and body composition in Iranian children. This cross-sectional study was performed on 9-18 years old children (125 boys, 137 girls). The serum level of calcium, phosphorous, alkaline phosphatase, and vitamin D parameters were checked. The body composition and BMD variables were measured by the Hologic system DXA. The rs566442 (V1119V) coding polymorphism in exon 15 of LRP5 was performed using PCR-RFLP method. Linear regression analysis, with adjustment for age, gender, body size parameters, and pubertal status was used to determine the association between LRP5 polymorphism (rs556442) and bone and body composition parameters. The allele frequency of the rs566442 gene was 35.5 % A and 63.9 % G. Our study revealed that LRP5 (rs556442) has not any significant influence on serum calcium, phosphorus, 25OHvitD, and serum alkaline phosphatase (P > 0.05). Total lean mass was greater in GG genotype (P = 0.028). Total body less head area (P = 0.044), spine BMD (P = 0.04), and total femoral BMC (P = 0.049) were lower in AG heterozygote genotype. This study show LRP5 polymorphism may associate with body composition and BMD in Iranian children. However, further investigations should be done to evaluate the role of other polymorphism.

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

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

Fracture prediction and the definition of osteoporosis in children and adolescents: the ISCD 2013 Pediatric Official Positions

The ISCD 2007 Pediatric Official Positions define osteoporosis in children on the basis of fracture history and low bone density, adjusted as appropriate for age, gender, and body size. The task force on fracture prediction and osteoporosis definition has reviewed these positions and suggests modifications with respect to vertebral fracture and the definition of a significant fracture history and draws attention to the need to consider degree of trauma as a factor that may modify fracture risk prediction.

Bone health in adolescent females with anorexia nervosa: what is a clinician to do?

The objective of this case report is to present a pharmacologic strategy for treatment of adolescents with anorexia nervosa (AN) and low bone mineral density (BMD). We present a 17.5-year-old girl with a 3-year history of AN and longstanding inability to optimize nutrition and gain weight, and a decrease over time in her already low BMD. A year after treatment with the 17-β estradiol patch (100 mcg twice weekly) with cyclic oral progesterone (2.5 mg medroxyprogesterone acetate daily for days 1-10 of every month), her spine and hip BMD Z-scores improved, and a further decrease was prevented. This novel treatment is a consideration for girls with AN at greatest risk for low BMD. Adolescents with AN are at risk for low BMD, and the most effective treatment is weight and menses restoration, which can be difficult to attain and to sustain. Recent studies have shown promising results with pharmacological therapy for low BMD in AN. This article discusses current concepts related to bone loss in AN, and new pharmacologic considerations for adolescents at greatest risk for low BMD.

Diagnostic evaluation of bone densitometric size adjustment techniques in children with and without low trauma fractures

Several established methods are used to size adjust dual-energy X-ray absorptiometry (DXA) measurements in children. However, there is no consensus as to which method is most diagnostically accurate. All size-adjusted bone mineral density (BMD) values were more diagnostically accurate than non-size-adjusted values. The greatest odds ratio was estimated volumetric BMD for vertebral fracture.

INTRODUCTION

The size dependence of areal bone density (BMDa) complicates the use of DXA in children with abnormal stature. Despite several size adjustment techniques being proposed, there is no consensus as to the most appropriate size adjustment technique for estimating fracture risk in children. The aim of this study was to establish whether size adjustment techniques improve the diagnostic ability of DXA in a cohort of children with chronic diseases.

METHODS

DXA measurements were performed on 450 children, 181 of whom had sustained at least one low trauma fracture. Lumbar spine (L2-L4) and total body less head (TBLH) Z-scores were calculated using different size adjustment techniques, namely BMDa and volumetric BMD for age (bone mineral apparent density (BMAD)); bone mineral content (BMC) and bone area for height; BMC for bone area; BMC for lean mass (adjusted for height); and BMC for bone and body size.

RESULTS

Unadjusted L2-L4 and TBLH BMDa were most sensitive but least specific at distinguishing children with fracture. All size adjustments reduced sensitivity but increased post-test probabilities, from a pre-test probability of 40 % to between 58 and 77 %. The greatest odds ratio for fracture was L2-L4 BMAD for a vertebral fracture and TBLH for lean body mass (LBM) (adjusted for height) for a long bone fracture with diagnostic odds ratios of 9.3 (5.8-14.9) and 6.5 (4.1-10.2), respectively.

CONCLUSION

All size adjustment techniques improved the predictive ability of DXA. The most accurate method for assessing vertebral fracture was BMAD for age. The most accurate method for assessing long bone fracture was TBLH for LBM adjusted for height.

Normative data and percentile curves of bone mineral density in healthy Iranian children aged 9-18 years

We provide the first reference values for bone mineral content and bone mineral density according to age and sex in Iranian children and adolescents. The prevalence of hypovitaminosis D was high, and levels of physical activity were low in our sample. Multiple regression analyses showed age, BMI, and Tanner stage to be the main indicators of bone mineral apparent density.

PURPOSE

Normal bone structure is formed in childhood and adolescence. The potential determinants which interact with genetic factors to influence bone density include gender, nutritional, lifestyle, and hormonal factors. This study aimed to evaluate bone mineral content (BMC) and the bone mineral density (BMD) and factors that may interfere with it in Iranian children.

METHODS

In this cross-sectional study, 476 healthy Iranian children and adolescents (235 girls and 241 boys) aged 9-18 years old participated. BMC and BMD of the lumbar spine, femoral neck, and total body were measured by dual-energy X-ray absorptiometry using a Hologic Discovery device, and bone mineral apparent density (BMAD) of the lumbar spine and the femoral neck were calculated.

RESULTS

We present percentile curves by age derived separately for BMC, BMD, and BMAD of the lumbar spine, left femoral neck, and total body excluding the head for boys and girls. Maximum accretion of BMC and BMD was observed at ages of 11-13 years (girls) and 12-15 years (boys).The prevalence of hypovitaminosis D was high and physical activity was low in our participants. However, in multiple regression analyses, age, BMI, and Tanner stage were the main indicators of BMD and BMAD CONCLUSION: These normative data aid in the evaluation of bone density in Iranian children and adolescents. Further research to evaluate the evolution of BMD in Iranian children and adolescents is needed to identify the reasons for significant differences in bone density values between Iranian populations and their Western counterparts.

Bone mineral density in male adolescents with autism spectrum disorders and disruptive behavior disorder with or without antipsychotic treatment

OBJECTIVE

To investigate the long-term effects of antipsychotic (AP) treatment and AP-induced hyperprolactinemia on bone mineral density (BMD) and body composition in male adolescents with autism spectrum disorders (ASDs) and/or disruptive behavior disorder (DBD).

DESIGN

Physically healthy 10- to 20-year-old boys with ASD and/or DBD, chronically treated (n=56; mean 52 months, range 16-126 months) or not treated (n=47) with an AP, were recruited to this observational study. Prolactin levels and biochemical bone parameters were measured and BMD of the lumbar spine and total body, and body composition were assessed by dual-energy X-ray absorptiometry, and volumetric BMD of the lumbar spine calculated. Group differences were tested with Student's t-test, χ(2) test, Fisher exact test, and logistic regression analysis.

RESULTS

Forty-nine percent of the boys treated with an AP had hyperprolactinemia. The mean volumetric lumbar spine BMD z-score was lower (P=0.043), the total percentage of body fat z-score was higher (P=0.042), and biochemical bone marker carboxyterminal cross-linking telopeptide of bone collagen was lower in the AP-treated boys with hyperprolactinemia than in the AP-treated boys without hyperprolactinemia. Seven to 11% of the hyperprolactinemic boys had low BMD. The mean lumbar spine and total body BMD z-scores and body composition were similar in the boys who were or were not treated with an AP. The total study population had a lower mean lean tissue mass (mean z-score -0.37, P=0.004) and a higher percentage of total body fat (mean z-score 1.16, P<0.001) than healthy controls (normative data); biochemical bone parameters were within normal limits.

CONCLUSION

AP-induced hyperprolactinemia in boys with ASD or DBD may have a negative effect on lumbar spine BMD. Longitudinal studies are needed to confirm this finding and further disentangle the effects of the disorder, lifestyle, treatment, and hyperprolactinemia.

Is bone mineral mass truly decreased in teenagers with a first episode of forearm fracture? A prospective longitudinal study

BACKGROUND

Forearm fractures are common in the pediatric population and are mostly treated by cast immobilization. The purposes of this study were first to determine whether forearm fractures in adolescents are associated with abnormal bone mineral density (BMD) or content (BMC) at the time of fracture, and second, to quantify the bone mineral loss at various sites due to cast-mediated immobilization.

METHODS

This longitudinal case-control study recruited 50 adolescents (age, 12.8 ± 1.8 y) who underwent cast-mediated immobilization for a forearm fracture and 50 healthy controls (13.0 ± 1.8 y). Using 2 dual-energy x-ray absorptiometries, BMD and BMC were measured at various skeletal sites (total body, lumbar spine, total upper limb, and forearm) at fracture time and at cast removal.

RESULTS

At the fracture time, BMD/BMC Z-scores at the lumbar spine and areal BMD at the peripheral wrist were not different among the injured and the healthy subjects. At cast removal, significant BMD decreases were observed in adolescents with fracture at the level of the radial and the ulnar diaphyses (-5.6% and -3.8%, respectively) and the total upper limb (-5.6%) compared with the noninjured side. Significant decreases in the BMC values were observed at the level of the radial diaphysis (-6.4%), ultradistal ulna (-10.2%), total upper limb, and total ulna (-8.2% and -4.9%, respectively).

CONCLUSIONS

These data demonstrate that total body, lumbar spine, or wrist bone mineral mass and density (BMC and BMD) are not reduced at the fracture time in adolescents sustaining a first episode of upper limb fracture when compared with healthy subjects. These findings suggest that forearm fractures are not related to osteopenia in youth. In addition, cast-mediated immobilization results in a significant bone mineral loss at the upper limb, which may explain the increased risk of sustaining a second fracture. Finally, bone callus formation may interfere when assessing bone mineral mass after cast removal and may lead to an erroneous underestimation of bone mineral mass decrease.

LEVEL OF EVIDENCE

Level IV.

Dual-energy X-ray absorptiometry interpretation: a simple equation for height correction in preteenage children

Dual-energy X-ray absorptiometry (DXA) results, even when corrected for age, gender, and ethnicity, can lead clinicians to erroneously diagnose osteoporosis in short healthy children and underdiagnose osteoporosis in tall children. We derived 2 simple equations for preteenagers <Tanner 3 to "height-correct" any DXA instrument having pediatric reference ranges. Our equations to find "height-age" (HA) are based on Center for Disease Control and Prevention growth tables. The equations calculate HA; i.e., the age a child would be if he/she were 50th percentile for height. For girls (ages 2-12 yr, heights 85-151 cm): HA(yr)=21.53+0.447 × height(cm)-6.2415 × height(cm). For boys (ages 2-13 yr, heights 86-156 cm): HA(yr)=8.23+0.3264 × height(cm)-3.7 × height(cm). Next, we applied our 2 equations to DXA results acquired from 102 children with untreated hypophosphatasia (HPP), a disorder that impairs bone mineralization and compromises height. Our height-adjusted bone mineral density and bone mineral content Z-scores were concordant with the multistep methods of Zemel et al for the overlapping age ranges. Thus, we validated, using HPP patients, our equations (and, by extension, the visual inspection method) and the method of Zemel et al for use in children in bone disease. Our equations remove a height-effect for both pediatric spine and total hip DXA Z-scores. They help to correct for bone size in American children <Tanner 3 without using growth tables or statistical software, apply to all DXA instruments, and evaluate even young children. Similar equations could be derived for any pediatric population for which sufficient growth data are available.

Effects of cast-mediated immobilization on bone mineral mass at various sites in adolescents with lower-extremity fracture

BACKGROUND

Leg or ankle fractures occur commonly in the pediatric population and are primarily treated with closed reduction and cast immobilization. The most predictable consequences of immobilization and subsequent weight-bearing restriction are loss of bone mineral mass, substantial muscle atrophy, and functional limitations. The purposes of this study were to determine if lower-limb fractures in adolescents are associated with abnormal bone mineral density or content at the time of fracture, and to quantify bone mineral loss at various sites due to cast-mediated immobilization and limited weight-bearing.

METHODS

We recruited fifty adolescents aged ten to sixteen years who had undergone cast immobilization for a leg or ankle fracture. Dual x-ray absorptiometry scans of the total body, lumbar spine, hip, leg, and calcaneus were performed at the time of fracture and at cast removal. Patients with a fracture were paired with healthy controls according to sex and age. Values at baseline and at cast removal, or at equivalent time intervals in the control group, were compared between groups and between the injured and uninjured legs of the adolescents with the fracture.

RESULTS

At the time of fracture, there were no observed differences in the bone mineral density or bone mineral content Z-scores of the total body or the lumbar spine, or in the bone mineral density Z-scores of the calcaneus, between the injured and healthy subjects. At cast removal, bone mineral parameters on the injured side were significantly lower than those on the uninjured side in the injured group. Differences ranged from -5.8% to -31.7% for bone mineral density and from -5.2% to -19.4% for bone mineral content. During the cast period, the injured adolescents had a significant decrease of bone mineral density at the hip, greater trochanter, calcaneus, and total lower limb as compared with the healthy controls.

CONCLUSIONS

Lower-limb fractures are not related to osteopenia in adolescents at the time of fracture. However, osteopenia does develop in the injured limb during cast immobilization for fracture treatment. Further investigation is required to determine if the bone mineral mass will return to normal or if a permanent decrease is to be expected, which may constitute a hypothetical risk of sustaining a second fracture.

Altered bone composition in children with vertebral fracture

Primary osteoporosis in children often leads to vertebral fractures, but it remains unknown whether these fractures associate with changes in bone composition. This study aimed to determine the differences in bone composition in fracture-prone children with and without vertebral fractures, as assessed by Fourier transform infrared spectroscopic imaging (FTIRI) and bone histomorphometry. Iliac crest bone biopsies (n = 24) were obtained from children who were suspected of primary osteoporosis based on evidence from the fracture history and/or low bone mineral density (BMD) by dual-energy X-ray absorptiometry. Vertebral morphology was determined by radiography. Bone biopsies were analyzed using histomorphometry and FTIRI. Phosphate-to-amide I, carbonate-to-phosphate, carbonate-to-amide I, and cross-link ratio (collagen maturity) were calculated. Children with (n = 14) and without (n = 10) vertebral fracture were compared. Low cancellous bone volume (BV/TV) was detected by histomorphometry in 36% of the children with vertebral fracture, and bone turnover rate was abnormal in 64% of them. Children with vertebral fractures had lower carbonate-to-phosphate ratios (p < .05) and higher collagen maturity (p < .05) than children without vertebral fracture. The children with low BV/TV in biopsy showed lower carbonate-to-amide I ratios (p < .05) than the children with normal bone volume. This study showed changes in bone composition among fracture-prone children who had sustained a vertebral fracture. The observed changes in bone composition in these children may contribute to their greater propensity to sustain vertebral fractures.

Correlation of insulin sensitivity with bone mineral status in obese adolescents with nonalcoholic fatty liver disease

AIM

The aim of this study was to investigate the relationships between bone mineral density (BMD) vs insulin resistance and metabolic risk factors in obese adolescents with nonalcoholic fatty liver disease (NAFLD).

PATIENTS AND METHODS

Eighty-two obese adolescents [45 girls and 37 boys, mean age: 12·3 ± 1·7 years, mean body mass index-standard deviation score (BMI-SDS): 1·9 ± 0·2] and 30 control subjects (15 girls and 15 boys, mean age: 12·3 ± 1·45 years, mean BMI-SDS: 0·5 ± 0·7) were enrolled the study. The obese subjects were divided into two groups based on the presence or absence of liver steatosis with high transaminases (NAFLD group and non-NAFLD group). Insulin resistance was evaluated by homeostasis model assessment (HOMA-IR) from fasting samples. BMD was determined by dual-energy X-ray absorptiometry.

RESULTS

Fasting insulin levels in the NAFLD group were significantly higher than in the non-NAFLD obese (32·3 ± 24·0 vs 11·02 ± 2·95 mU/l, P < 0·001) and control groups (8·4 ± 2·4 mU/l, P< 0·001). The NAFLD group had higher values of HOMA-IR than the non-NAFLD obese (7·3 ± 0·1 vs 2·3 ± 0·7, P < 0·001) and control groups (1·8 ± 0·5, P < 0·001). BMD-SDS measurements were lower in the NAFLD group than in the non-NAFLD (0·56 ± 0·3 vs 1·02 ± 0·9, P < 0·001) and control groups (0·56 ± 0·3 vs 1·37 ± 1·04, P < 0·001). BMD-SDS was positively correlated with BMI-SDS (r = 0·530, P = 0·004) and negatively correlated with HOMA-IR (r = -0·628, P = 0·017) in the NAFLD obese group.

CONCLUSION

This study reports the association between BMD-SDS and insulin resistance in obese adolescents both with and without NAFLD, although the NAFLD group had a lower BMD-SDS than the non-NAFLD group. We suggest that NAFLD has a detrimental effect on bone health in adolescents, and it is correlated with increased insulin resistance.

Approach to the child with fractures

Evaluation of the child with fractures is challenging, as no clear guidelines exist to distinguish traumatic from pathological fractures. Although most fractures in childhood are benign, recurrent fractures may be associated with a wide variety of primary skeletal diseases as well as secondary causes, necessitating a careful history and physical exam to guide the evaluation. There is no "gold standard" for the evaluation and treatment of children with fractures and low bone mineral density (BMD); therefore, the diagnosis of osteoporosis in a pediatric patient should be made using a combination of clinical and radiographic features. Interpretation of bone densitometry in growing patients presents a unique set of challenges because areal BMD measured by dual-energy x-ray absorptiometry depends on multiple dynamic variables. Interpretation of pediatric dual-energy x-ray absorptiometry should be based on Z-scores (sd scores compared to age, sex, and ethnicity-matched controls), using normative databases specific to the brand of densitometer and the patient population. Given the skeleton's ability to recover from low BMD through modeling and remodeling, optimizing management of underlying conditions leading to bone fragility is the initial step. Conservative measures including calcium and vitamin D supplementation and weight-bearing physical activity are important interventions that should not be overlooked. The use of bisphosphonates in children and adolescents is controversial due to lack of long-term efficacy and safety data and should be limited to clinical trials and compassionate therapy in children with significantly compromised quality of life. Close monitoring is required, and further study is necessary to assess their long-term safety and efficacy in children.

Gender differences in bone mineral density in obese children during pubertal development

OBJECTIVE

To investigate whether body mass index (BMI) and body composition can affect peak bone mass in a population of obese (OB) (BMI SDS>2.0) and normal weight (NORM) (BMI-SD score <2.0) pubertal subjects (Tanner stage T3 to T5).

PATIENTS AND METHODS

151 subjects (81 OB, age 14.5±2.4 yr) were analyzed using dual-X-ray absorbiometry technique to study Lumbar and whole body bone mineral density (BMD) (areal, normalized for height) and Z-score, lean mass (LM) and lean/fat ratio.

RESULTS

As a whole group, OB males did not show any significant difference in bone parameters vs NORM, while OB females showed higher bone density parameters (p<0.05). When grouped according to T, while OB males showed higher bone density at T3-4 stage (p<0.01), and lower at T5 (p<0.01) compared to NORM, OB females showed a tendency through increased BMD at T3-4 and T5 although statistically different only at T5. BMD was independently correlated to LM, lean/fat ratio, and testosterone in NORM males and, at lower level, in OB males, while to LM in NORM females and only to age in OB females.

CONCLUSION

Our data seem to confirm the possible negative influence of obesity on bone density in boys, a possible explanation could be an unfavorable body composition during sexual maturation that seems not to affect bone development in adolescents girls.

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

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Osteoporosis in anorexia nervosa

Anorexia nervosa is a condition associated with reduced bone mass and increased bone fragility, for which there is no known effective treatment. Anorexia nervosa usually has its onset during adolescence, the critical time when peak bone mass is accrued. Low bone mass is caused by reduced bone formation, as well as accelerated bone resorption. The etiology is multifactorial and includes poor nutrition, low bodyweight, sex hormone deficiency and hypercortisolism. Weight gain and resumption of menses is accompanied by some improvement in bone mass, but may not restore it to normal levels. Oral estrogen-replacement therapy is not effective in increasing bone mass in this disorder. The bisphosphonates, used in conjunction with nutritional rehabilitation and weight gain, have shown promise, but concerns about safety have limited their use. The aim of this article is to highlight recent recommendations regarding the assessment of fracture risk in children and adolescents, summarize the evidence for low bone mass and increased fracture risk in anorexia nervosa, and discuss approaches to the management of low bone mass in this disorder.

Female reproductive system and bone

The female reproductive system plays a major role in regulating the acquisition and loss of bone by the skeleton from menarche through senescence. Onset of gonadal sex steroid secretion at puberty is the major factor responsible for skeletal longitudinal and radial growth, as well as significant gain in bone density, until peak bone density is achieved in third decade of life. Gonadal sex steroids then help maintain peak bone density until menopause, including during the transient changes in skeletal mineral content associated with pregnancy and lactation. At menopause, decreased gonadal sex steroid production normally leads to rapid bone loss. The most rapid bone loss associated with decreased estrogen levels occurs in the first 8-10 years after menopause, with slower age-related bone loss occurring during later life. Age-related bone loss in women after the early menopausal phase of bone loss is caused by ongoing gonadal sex steroid deficiency, vitamin D deficiency, and secondary hyperparathyroidism. Other factors also contribute to age-related bone loss, including intrinsic defects in osteoblast function, impairment of the GH/IGF axis, reduced peak bone mass, age-associated sarcopenia, and various sporadic secondary causes. Further understanding of the relative contributions of the female reproductive system and each of the other factors to development and maintenance of the female skeleton, bone loss, and fracture risk will lead to improved approaches for prevention and treatment of osteoporosis.

The relationship between fractures and DXA measures of BMD in the distal femur of children and adolescents with cerebral palsy or muscular dystrophy

Children with limited or no ability to ambulate frequently sustain fragility fractures. Joint contractures, scoliosis, hip dysplasia, and metallic implants often prevent reliable measures of bone mineral density (BMD) in the proximal femur and lumbar spine, where BMD is commonly measured. Further, the relevance of lumbar spine BMD to fracture risk in this population is questionable. In an effort to obtain bone density measures that are both technically feasible and clinically relevant, a technique was developed involving dual-energy X-ray absorptiometry (DXA) measures of the distal femur projected in the lateral plane. The purpose of this study is to test the hypothesis that these new measures of BMD correlate with fractures in children with limited or no ability to ambulate. The relationship between distal femur BMD Z-scores and fracture history was assessed in a cross-sectional study of 619 children aged 6 to 18 years with muscular dystrophy or moderate to severe cerebral palsy compiled from eight centers. There was a strong correlation between fracture history and BMD Z-scores in the distal femur; 35% to 42% of those with BMD Z-scores less than -5 had fractured compared with 13% to 15% of those with BMD Z-scores greater than -1. Risk ratios were 1.06 to 1.15 (95% confidence interval 1.04-1.22), meaning a 6% to 15% increased risk of fracture with each 1.0 decrease in BMD Z-score. In clinical practice, DXA measure of BMD in the distal femur is the technique of choice for the assessment of children with impaired mobility.

Official positions of the International Society for Clinical Densitometry (ISCD) on DXA evaluation in children and adolescents

Dual-energy X-ray absorptiometry (DXA) is the most widely used technical instrument for evaluating bone mineral content (BMC) and density (BMD) in patients of all ages. However, its use in pediatric patients, during growth and development, poses a much more complex problem in terms of both the technical aspects and the interpretation of the results. For the adults population, there is a well-defined term of reference: the peak value of BMD attained by young healthy subjects at the end of skeletal growth. During childhood and adolescence, the comparison can be made only with healthy subjects of the same age, sex and ethnicity, but the situation is compounded by the wide individual variation in the process of skeletal growth (pubertal development, hormone action, body size and bone size). The International Society for Clinical Densitometry (ISCD) organized a Pediatric Position Development Conference to discuss the specific problems of bone densitometry in growing subjects (9-19 years of age) and to provide essential recommendations for its clinical use.

Peptide YY in adolescent athletes with amenorrhea, eumenorrheic athletes and non-athletic controls

BACKGROUND

Bone mineral density (BMD) is lower in amenorrheic athletes (AA) compared with eumenorrheic athletes (EA). Decreased energy availability and altered levels of appetite regulating hormones (ghrelin and leptin) in AA contribute to hypogonadism, an important cause of low BMD. The role of other nutritionally regulated hormones such as peptide YY (PYY) and adiponectin in mediating gonadal status and bone metabolism remains to be determined.

OBJECTIVES

Our objective was to determine whether PYY and adiponectin are higher in AA compared with EA and contribute to hypogonadism and impaired bone metabolism in AA.

METHODS

We determined PYY and adiponectin in 16 AA, 15 EA and 16 non-athletic controls 12-18 years old, and other nutritionally dependent hormones including ghrelin, leptin and IGF-1. We also measured testosterone, estradiol, PINP and NTX (markers of bone formation and resorption) and BMD.

RESULTS

PYY was higher in AA than EA (111+/-52 vs. 61+/-29 pg/ml, p<0.05), whereas adiponectin did not differ between groups. Although activity scores did not differ, BMI was lower in AA than EA and a larger proportion (62.5% vs. 6.7%) reported disordered eating, indicating lower energy availability. PYY and adiponectin were independent predictors of testosterone in a regression model (p=0.01 and 0.04), but did not predict estradiol. PYY, but not adiponectin, was an independent and negative predictor of PINP (p=0.002) and lumbar bone mineral apparent density Z-scores (p=0.045) in this model.

CONCLUSION

High PYY levels (but not adiponectin) differentiate AA from EA, and may be an important factor contributing to low bone density in athletes.

Clinical review 1: Bisphosphonate use in childhood osteoporosis

CONTEXT

As awareness of osteoporosis in childhood has increased, so have pressures to consider use of the pharmacological agents used to treat osteoporosis in adults. This review examines available research on the efficacy and safety of bisphosphonate therapy for pediatric osteoporosis.

EVIDENCE ACQUISITION

We reviewed the medical literature for key articles and consensus statements on the use of bisphosphonates in children through June 2008.

EVIDENCE SYNTHESIS

We compared reports using varying bisphosphonate agents, doses, and duration of therapy to treat osteogenesis imperfecta and a variety of secondary causes of osteoporosis in children. Conclusions drawn from a recently published Cochrane analysis and the consensus statements from experts in the field were considered as well.

CONCLUSIONS

Use of bisphosphonate therapy in pediatric patients remains controversial because of inadequate long-term efficacy and safety data. For this reason, many experts recommend limiting use of these agents to those children with recurrent extremity fractures, symptomatic vertebral collapse, and reduced bone mass. Current data are inadequate to support the use of bisphosphonates in children to treat reductions in bone mass/density alone. More research is needed to define appropriate indications for bisphosphonate therapy and the optimal agent, dose, and duration of use in pediatric patients.

Accounting for body size deviations when reporting bone mineral density variables in children

In a child, bone mineral density (BMD) may differ from an age-expected normal value, not only because of the presence of disease, but also because of deviations of height or weight from population averages. Appropriate adjustment for body size deviations simplifies interpretation of BMD measurements.

INTRODUCTION

For children, a bone mineral density (BMD) measurement is normally expressed as a Z score. Interpretation is complicated when weight or height distinctly differ from age-matched children. We develop a procedure to allow for the influence of body size deviations upon measured BMD.

METHODS

We examined the relation between body size deviation and spine, hip and whole body BMD deviation in 179 normal children (91 girls). Expressions were developed that allowed derivation of an expected BMD based on age, gender and body size deviation. The difference between measured and expected BMD was expressed as a HAW score (Height-, Age-, Weight-adjusted score).

RESULTS

In a second independent sample of 26 normal children (14 girls), measured spine, total femur and whole body BMD all fell within the same single normal range after accounting for age, gender and body size deviations. When traditional Z scores and HAW scores were compared in 154 children, 17.5% showed differences of more than 1 unit and such differences were associated with height and weight deviations.

CONCLUSION

For almost 1 in 5 children, body size deviations influence BMD to an extent that could alter clinical management.

Fracture prediction and the definition of osteoporosis in children and adolescents: the ISCD 2007 Pediatric Official Positions

Osteoporosis in adults has been defined on the basis of densitometric criteria, but at present the term osteoporosis does not have a widely recognized definition in pediatrics. Consequently, the International Society for Clinical Densitometry (ISCD) 2007 Position Development Conference reviewed the literature describing the relationship between bone densitometric studies and fractures in apparently healthy children and adolescents, and prepared Official Positions regarding the definition of osteoporosis in children and adolescents. The ISCD Official Positions with respect to the above issues, as well as the rationale and evidence used to derive these positions, are presented here.

Dual energy X-ray absorptiometry interpretation and reporting in children and adolescents: the 2007 ISCD Pediatric Official Positions

The International Society for Clinical Densitometry Official Positions on reporting of densitometry results in children represent an effort to consolidate opinions to assist healthcare providers determine which skeletal sites should be assessed, which adjustments should be made in these assessments, appropriate pediatric reference databases, and elements to include in a dual energy X-ray absorptiometry (DXA) report. Skeletal sites recommended for assessment are the lumbar spine and total body less head, the latter being valuable as it provides information on soft tissue, as well as bone. Interpretation of DXA findings in children with growth or maturational delay requires special consideration; adjustments are required to prevent erroneous interpretation. Normative databases used as a reference should be based on a large sample of healthy children that characterizes the variability in bone measures relative to gender, age, and race/ethnicity, and should be specific for each manufacturer and model of densitometer and software. Pediatric DXA reports should provide relevant demographic and health information, technical details of the scan, Z-scores, and should not include T-scores. The rationale and evidence for development of the Official Positions are provided. Given the sparse data currently available in many of these areas, it is likely that these positions will change over time as new data become available.

Bone metabolism in adolescent boys with anorexia nervosa

BACKGROUND

Anorexia nervosa (AN) is a condition of severe undernutrition associated with low bone mineral density (BMD) in adolescent females with this disorder. Although primarily a disease in females, AN is increasingly being recognized in males. However, there are few or no data regarding BMD, bone turnover markers or their predictors in adolescent AN boys.

HYPOTHESES

We hypothesized that BMD would be low in adolescent boys with AN compared with controls associated with a decrease in bone turnover markers, and that the gonadal steroids, testosterone and estradiol, and levels of IGF-I and the appetite regulatory hormones leptin, ghrelin, and peptide YY would predict BMD and bone turnover markers.

METHODS

We assessed BMD using dual-energy x-ray absorptiometry and measured fasting testosterone, estradiol, IGF-I, leptin, ghrelin, and peptide YY and a bone formation (aminoterminal propeptide of type 1 procollagen) and bone resorption (N-telopeptide of type 1 collagen) marker in 17 AN boys and 17 controls 12-19 yr old.

RESULTS

Boys with AN had lower BMD and corresponding Z-scores at the spine, hip, femoral neck, trochanter, intertrochanteric region, and whole body, compared with controls. Height-adjusted measures (lumbar bone mineral apparent density and whole body bone mineral content/height) were also lower. Bone formation and resorption markers were reduced in AN, indicating decreased bone turnover. Testosterone and lean mass predicted BMD. IGF-I was an important predictor of bone turnover markers.

CONCLUSION

AN boys have low BMD at multiple sites associated with decreased bone turnover markers at a time when bone mass accrual is critical for attainment of peak bone mass.

Measures of childhood fitness and body mass index are associated with bone mass in adulthood: a 20-year prospective study

The long-term effects of childhood exercise and body mass index (BMI) on bone mass remain uncertain. We measured 1434 children, 7-15 yr of age, as part of the Australian Schools Health and Fitness Survey in 1985 and approximately 20 yr later (mean age, 31 yr). Fitness measures included a 1.6-km run and a 50-m sprint (childhood only), leg strength, standing long jump, and physical work capacity at 170 beats/min (PWC(170); childhood and adulthood). BMI was assessed at both time points. A single Sahara bone ultrasound densitometer was used to determine heel bone mass. We found, in females, there were modest but significant beneficial relationships between the childhood 1.6-km run, 50-m sprint, standing long jump, and adult bone mass. In both sexes, PWC(170) at 9 yr of age had a greater influence on adult bone mass (r(2) = 5-8%, all p < 0.05) than it did for 15 yr olds (r(2) = <1%, all p > 0.05), independent of adult performance. In the 12 yr olds, childhood PWC(170) was also associated with female adult bone mass (broadband ultrasound attenuation: r(2) = 6%, p = 0.045). In males, childhood BMI (but no performance measures) was positively associated with adult bone mass after adjustment for adult BMI. In conclusion, childhood fitness levels, particularly in females and in the early pubertal years, are predictive of adult skeletal status as measured by quantitative ultrasound, whereas BMI is predictive in males only. These results suggest that increased skeletal loading in childhood leads to an increase in peak bone mass independent of current loading.

Weight gain and restoration of menses as predictors of bone mineral density change in adolescent girls with anorexia nervosa-1

CONTEXT

Adolescents with anorexia nervosa (AN) have low bone mineral density. However, the effect of disease recovery, first, on bone density measures assessed using the Molgaard approach, which differentiates between reported low bone density resulting from short bones (based on height Z-scores) and that resulting from thin bones [based on measures of bone area (BA) for height] or light bones [based on measures of bone mineral content (BMC) for BA]; and second, on height-adjusted bone density measures, has not been well characterized. We hypothesized that menstrual recovery and weight gain (> or =10% increase in body mass index) would predict an increase in these measures of bone density.

METHODS

In a prospective observational study, lumbar and whole-body (WB) bone density was measured at 0, 6, and 12 months in 34 AN girls aged 12-18 yr and 33 controls. Using Ward's modification of the Molgaard approach, we determined measures of BMC for BA and BA for height at the lumbar spine and WB and also determined spine bone mineral apparent density and WB BMC adjusted for height.

RESULTS

Girls with AN had lower spine BMC for BA Z-scores (P = 0.0009), and lower WB BA for height Z (P < 0.0001), compared with controls. Menstrual recovery and weight gain in AN (AN-recovered) (median 9 months) resulted in a stabilization of BMD measures, whereas BMD continued to decrease in AN who did not gain weight and recover menses (AN-not recovered). AN-recovered also predicted greater increases in spine BMC for BA and WB BA for height, compared with AN-not recovered (P < 0.05).

CONCLUSIONS

Even short-term weight gain with menstrual recovery is associated with a stabilization of BMD measures.

Cancer treatment-induced bone loss

PURPOSE OF REVIEW

Patients treated for cancer may be at risk for osteoporosis and fracture. Evaluation and treatment of patients with cancer treatment-induced bone loss should lead to fewer fractures. This review will help clinicians learn to identify, evaluate and treat cancer patients at risk.

RECENT FINDINGS

Survivors of childhood cancers and patients made hypogonadal by treatment for breast or prostate cancer are clearly at risk for osteoporosis and fracture. Use of aromatase inhibitors rather than tamoxifen for breast cancer will likely lead to more osteoporosis. Bisphosphonates prevent bone loss in many patients at risk.

SUMMARY

For many cancer patients, treatment with calcium, vitamin D, and bisphosphonates will likely decrease the consequences of cancer treatment-induced bone loss, namely fractures.

Osteoporosis in children and adolescents

In recent years, the issue of low bone density in children and adolescents has attracted much attention. The classical definition of osteoporosis should be valid at any age, yet its practical applicability to children and adolescents remains a matter of debate and there is no consensus on a diagnosis based solely on the BMD value. The clinical relevance of uncomplicated low bone density in the young and its long-term consequences remain difficult to evaluate and there is only preliminary evidence that the BMD value is a predictor of fracture risk in growing subjects. Moreover, the interpretation of densitometric data in the young is difficult because the "normal" BMD values to be used for comparison are continuously changing with age, and in addition, depend on several variables, such as gender, body size, pubertal stage, skeletal maturation and ethnicity. Although Z-score values below -2 are generally considered a serious warning, most bone specialists make a diagnosis of osteoporosis in children and adolescents only in the presence of low BMD and at least one fragility fracture. The scope of this review is limited to presenting a picture of the available knowledge. The literature on fractures will be presented in detail, since fractures are one of the key elements in the debate. There are countless papers on fractures in childhood and adolescence, but very few of them attempt to identify fragility fractures, and still fewer develop the concept of osteoporosis in the young in relation to fractures. The different forms of primary and secondary osteoporosis, the more technical aspects of bone densitometry in pediatrics, and the delicate issue of treatment will be discussed only briefly.

Pediatric bone density and fracture

As children grow, they accumulate bone mineral, which serves as a "bone bank" for the future. Any condition that interferes with normal bone mineral accrual during childhood has the potential to reduce peak bone mass and subsequently increase future risk for fracture. In contrast to adults, for whom dual-energy x-ray absorptiometry (DXA) has become the standard clinical instrument for assessing bone mineral density and criteria have been developed to define osteopenia and osteoporosis, information for children is still limited. Numerous issues confound the interpretation of DXA-derived bone mineral density measurements in children, and clinicians often find themselves caught between the limitations of these methods and the practical issue of taking care of their pediatric patient. The explosion of treatment options for postmenopausal osteoporosis has resulted in new options for the treatment of children and adolescents. However, most of these agents have not been sufficiently well studied in children to permit the development of standardized treatment guidelines.

Can BMD assessed by DXA at age 8 predict fracture risk in boys and girls during puberty?: an eight-year prospective study

This study reports on the association between DXA at age 8 and subsequent fractures in both male and female children. Bone densitometry at the total body and spine (but not hip) is a strong predictor of fracture (especially upper limb) during puberty.

INTRODUCTION

The aim of this study was to determine if prepubertal DXA can predict fracture risk during puberty.

MATERIALS AND METHODS

We studied 183 children who were followed for 8 yr (1460 person-years). Bone densitometry was measured at the total body, hip, and spine by DXA and reported as BMC, BMD, and bone mineral apparent density (BMAD). Fractures were self-reported at age 16 with X-ray confirmation,

RESULTS

There were a total of 63 fractures (43 upper limb). In unadjusted analysis, only total body BMD showed an inverse relationship with upper limb fracture risk (p = 0.03). However, after adjustment for height, weight, age (all at age 8), and sex, total body BMC (HR/SD, 2.47; 95% CI, 1.52-4.02), spine BMC (HR/SD, 1.97: 95% CI, 1.30-2.98), total body BMD (HR/SD, 1.67; 95% CI, 1.18-2.36), total body BMAD (HR/SD, 1.54; 95% CI, 1.01-2.37), and spine BMD (HR/SD, 1.53; 95% CI, 1.10, 2.22) were all significantly associated with upper limb fracture risk. Similar, but weaker associations were present for total fractures. There was a trend for overweight/obesity to be associated with increased upper limb fracture risk (HR, 1.53/category; p = 0.08).

CONCLUSIONS

Measurement of bone mass by DXA is a good predictor of upper limb fracture risk during puberty. Although we did not measure true BMD, the constancy of fracture prediction after a single measure suggests bone strength remains relatively constant during puberty despite the large changes in bone size.

The bone mineral density in childhood study: bone mineral content and density according to age, sex, and race

CONTEXT

Low bone mass may increase risk of fracture. Several chronic medical conditions, medications, and lifestyle factors affect bone mineral accrual. Appropriate reference values are essential for identification of children with bone deficits.

OBJECTIVE

Our objective was to establish reference curves for bone mineral content (BMC) and density (BMD) in children.

DESIGN AND SETTING

The Bone Mineral Density in Childhood Study is an ongoing longitudinal study in which measurements are obtained annually at five clinical centers in the United States.

PARTICIPANTS

Participants included 1554 healthy children (761 male, 793 female), ages 6-16 yr, of all ethnicities.

MAIN OUTCOME MEASURES

Scans of the whole body, lumbar spine, hip, and forearm were obtained using dual-energy x-ray absorptiometry. Percentile curves based on three annual measurements were generated using the LMS statistical procedure.

RESULTS

BMC of the whole body and lumbar spine and BMD of the whole body, lumbar spine, total hip, femoral neck, and forearm are given for specific percentiles by sex, age, and race (Black vs. non-Black). BMC and BMD were higher for Blacks at all skeletal sites (P < 0.0001). BMC and BMD increased with age, and a plateau was not evident by age 16 (girls) or age 17 (boys). The variation in BMC and BMD also increased with age.

CONCLUSIONS

Age-, race-, and sex-specific reference curves can be used to help identify children with bone deficits and for monitoring changes in bone in response to chronic diseases or therapies.

Osteopenia and cancer in children and adolescents: the fragility of success

The attainment of a satisfactory peak bone mass, which is accomplished largely by the end of adolescence, is the best protection against excessive bone mineral loss in late adulthood. Factors that influence this process include age, race, sex, body size, pubertal status, diet, physical activity, and other lifestyle elements. Cancer and its treatment in children and teenagers adversely impact bone mineralization. In particular, chemotherapy (especially glucocorticosteroids and methotrexate) and cranial irradiation (apparently by reducing growth hormone secretion and by causing hypogonadotropic hypogonadism) interfere with normal bone turnover. Resorption often exceeds formation, resulting in net bone mineral loss and providing a rational basis for the use of antiresorptive drugs. Such osteopenia may be symptomatic, with pain and abnormal gait, and increases the risk of fractures several fold. The disorder is compounded by reduced physical activity, so programs to reduce this deficit are of measurable benefit. All of those engaged in the care of children and adolescents with cancer have an opportunity to improve the bone health of these young people and to limit their risk of developing osteoporosis and fragility fractures in adult life.

Consensus and Controversy Regarding Osteoporosis in the Pediatric Population

OBJECTIVE

To review current consensus and controversy surrounding the diagnosis and treatment of osteoporosis in childhood and adolescence.

METHODS

The medical literature was reviewed with emphasis on the importance of early skeletal health, risk factors for bone fragility, and the diagnosis and management of children at risk for osteoporosis.

RESULTS

Childhood and adolescence are critical periods for optimizing bone growth and mineral accrual. Bone strength is determined by bone size, geometry, quality, and mass-variables that are influenced by genetic factors, activity, nutrition, and hormones. For children with genetic skeletal disorders or chronic disease, bone growth and mineral accrual may be compromised, increasing the lifetime risk of osteoporosis. The goal for the clinician is to identify children at greatest risk for future fragility fracture. Bone densitometry and turnover markers are challenging to interpret in children. Prevention and treatment of bone fragility in children are less well established than in adults. Optimizing nutrition and activity may not restore bone health, but the drug armamentarium is limited. Sex steroid replacement has not proven effective in restoring bone mass in patients with anorexia nervosa or exercise-associated amenorrhea. Bisphosphonates can increase bone mass and may reduce bone pain and fractures, most convincingly in patients with osteogenesis imperfecta. Further studies are needed to establish the safety, efficacy, and optimal drug, duration, and dosage in pediatric patients.

CONCLUSION

Bone health during the first 2 decades contributes to the lifetime risk of osteoporosis. Further research is needed to develop evidence-based recommendations for the diagnosis and treatment of osteoporosis in childhood.