Volumetric bone mineral density--a potential role in paediatrics

Reference values for bone mineral density in healthy Mexican children and adolescents

INTRODUCTION

Clinical assessment of bone health by Dual-Energy X-ray Absorptiometry (DXA) in the paediatric population requires robust reference values. The International Society for Clinical Densitometry (ISCD) recommends that country/regional reference values ideally should be used to improve precision in bone health assessment.

OBJECTIVE

The aim of this study was to provide reference values for relevant bone health variables for healthy Mexican children and adolescents aged 5 to 18 years.

METHODS

This was a cross-sectional, stratified and population-based study, that measured a representative sample of healthy Mexican children and adolescents with DXA. We constructed age- and sex-smoothed reference values for areal bone mineral density (aBMD) of total body less head (TBLH), total body (TB), lumbar spine (LS), and bone mineral apparent density (BMAD) for LS, by means of Generalized Additive Models for Location, Scale and Shape (GAMLSS).

RESULTS

Reference data including the 3th, 5th, 10th, 25th, 50th, 75th, 90th, 95th and 97th centiles, along with lambda (L), mu (M) and sigma (S) values, are given for each variable of interest for each sex at 0.25 years intervals. Reference values relative to height and Tanner-stage for both sexes are also provided. Finally, formulas to enable Z score estimation for clinical use are also presented CONCLUSIONS: The sex, age, height, Tanner-stage and ethnic-specific reference data provided in this study should enable more precise assessment of bone health in the Mexican paediatric population. The data presented may also allow for future evaluation of potential similarities and differences across different ethnic groups.

Pubertal abnormalities in adolescents with chronic disease

Pubertal disorders in the context of chronic disease especially in those with chronic inflammatory disorders or those requiring prolonged periods of treatment with glucocorticoid are common reasons for referral to the paediatric endocrine clinic. Disorders of puberty are also common in adolescents with disability requiring management by paediatric endocrinologists. In these adolescents, impaired skeletal development is also observed and this can be associated with fragility fractures. Chronic inflammation, glucocorticoid and sub-optimal nutrition all impact on the hypothalamic-pituitary gonadal axis, and can also impact on skeletal development locally by their effects on the growth plate and bone. Addressing pubertal disorders is important to ensure adolescents with chronic disease are matched with their peers, promote adequate bone mass accrual and linear growth. Careful discussion with primary clinicians, the young person and the family is needed when instituting endocrine therapies to address puberty and manage bone health.

Osteoporosis in paediatric patients with spina bifida

The prevalence and morbidity associated with osteoporosis and fractures in patients with spina bifida (SB) highlight the importance of osteoporosis prevention and treatment in early childhood; however, the issue has received little attention. The method for the selection of appropriate patients for drug treatment has not been clarified.

OBJECTIVE

To review the literature concerning fracture risks and low bone density in paediatric patients with SB. We looked for studies describing state-of-the-art treatments and for prevention of secondary osteoporosis.

METHODS

Articles were identified through a search in the electronic database (PUBMED) supplemented with reviews of the reference lists of selected papers. The main outcome measures were incidence of fractures and risk factors for fracture, an association between bone mineral density (BMD) and occurrence of fracture, risk factors of low BMD, and effects of pharmacological and non-pharmacological treatments on BMD and on the incidence of fractures. We considered as a secondary outcome the occurrence of fractures in relation to the mechanism of injury.

RESULTS

Results indicated that patients with SB are at increased risk for fractures and low BMD. Risk factors that may predispose patients to fractures include higher levels of neurological involvement, non-ambulatory status, physical inactivity, hypercalciuria, higher body fat levels, contractures, and a previous spontaneous fracture. Limitations were observed in the number and quality of studies concerning osteoporosis prevention and treatment in paediatric patients with SB. The safety and efficiency of drugs to treat osteoporosis in adults have not been evaluated satisfactorily in children with SB.

A long-term study of bone mineral density in patients with phenylketonuria under diet therapy

INTRODUCTION

Dietary control of classic phenylketonuria (PKU) needs restriction of natural proteins; adequate protein intake is achieved by adding low phenylalanine (phe) formulae. The adequacy of this diet for normal bone mineralization had not been sufficiently evaluated. Our aim was to evaluate and follow up bone mineral density (BMD) in children and adolescents with PKU within a 2-year time interval to assess the adequacy of a phenylalanine restricted diet for bone mineralization and to search for a possible relationship between BMD, dietary control and blood phenylalanine (phe) concentrations.

MATERIAL AND METHODS

Thirty-two patients with classic PKU (3-19 years) were evaluated for their bone mineral status using dual energy X-ray absorptiometry (DEXA) both at the beginning (baseline) and the end (follow-up) of the study.

RESULTS

Low BMD was detected in 31.25% at the start and in 6.25% of patients after 2 years follows-up. No relationship was found between BMD and the duration of diet compliance and phe level as well.

CONCLUSIONS

In this study the low BMD detected in our patients was both at baseline and follow-up independent of diet restriction. A yearly DEXA would be highly beneficial for early detection and treatment, thus preventing osteoporosis and decreasing the risk of fractures. We also suggest the importance of searching for new emerging therapies such as enzyme substitution or gene therapy as low protein diet compliance was not enough to maintain normal bone mineral density.

Bone metabolism and the muscle-bone relationship in children, adolescents and young adults with phenylketonuria

The aim of the study was to assess body composition in subjects with phenylketonuria (PKU). Forty-five patients aged 13.8 ± 5.2 years were evaluated. Among them, 15 patients had not reached sexual maturity, showing normal serum values of phenylalanine (Phe) (subgroup 1), and 30 subjects were sexually mature (Tanner 5 stage), showing either normal serum Phe (18 cases; subgroup 2a) or increased serum Phe (12 cases; subgroup 2b). DXA-assessed spine and total body (TB) measurements [bone mineral density (BMD), bone mineral content (BMC), lean body mass (LBM) and the calculated ratios BMC/LBM] as well as laboratory parameters (serum carboxyterminal telopeptide of type I collagen, bone alkaline phosphatase, osteocalcin, parathormone, calcitonin, total and ionized calcium) were analyzed. Statistically significant differences were revealed between subgroup 1 versus 2a for TB BMC/LBM ratio SD scores and between subgroup 2a versus 2b for TB BMD, spine BMD, TB BMC/LBM ratio and spine BMC/LBM ratio SD scores. Stepwise multiple regression analysis revealed that serum Phe negatively affected bone status. The skeletal status in children with PKU is impaired by the disease. Applying body composition parameters instead of BMD alone may reflect the level of impairment in a new, different way.

Bone density in cerebral palsy

This article discusses the problem of osteoporosis in cerebral palsy. Osteoporosis remains a major health problem worldwide. Cerebral palsy is the most prevalent childhood condition associated with osteoporosis. Bone density is significantly decreased. Children with cerebral palsy often sustain painful fractures with minimal trauma that impair their function and quality of life. This article addresses the anatomy and structure of bone and bone metabolism, the clinical assessment of bone mass, the causes of osteoporosis and its evaluation and treatment in children with cerebral palsy.

Methods for measurement of pediatric bone

Many experts believe that optimizing bone mineral accrual early in life may prevent childhood fractures and possibly delay the development of osteoporosis later in life. Adequate nutrition and physical activity are environmental factors important in determining whether or not children acquire an appropriate amount of bone for their body size. Pediatric diseases, or therapeutic interventions used in their treatment, may interfere with normal bone development. Although there are specific methods available for assessing pediatric bone, there is no one method that can adequately assess bone health and identify the specific bone deficits that may be occurring. Understanding the biological basis for bone deficits and the ability of various bone assessment methods to discriminate or measure these deficits is important in understanding normal bone development and how to prevent and treat pediatric bone disease. The purpose of this review is to briefly describe changes in bone with growth, to define "bone density" in biological terms, to discuss some of the issues with pediatric bone measurements, and to review the three main methods for assessing bone parameters in pediatric populations. These methods, including dual energy X-ray absorptiometry (DXA), quantitative ultrasound (QUS) and peripheral quantitative computed tomography (pQCT) will be described, the advantages and disadvantages discussed, and the relationship between bone parameters and fracture risk presented for each of the methods.

A one-year exercise intervention program in pre-pubertal girls does not influence hip structure

Background

We have previously reported that a one-year school-based exercise intervention program influences the accrual of bone mineral in pre-pubertal girls. This report aims to evaluate if also hip structure is affected, as geometry independent of bone mineral influences fracture risk.

Methods

Fifty-three girls aged 7 – 9 years were included in a curriculum-based exercise intervention program comprising 40 minutes of general physical activity per school day (200 minutes/week). Fifty healthy age-matched girls who participated in the general Swedish physical education curriculum (60 minutes/week) served as controls. The hip was scanned by dual X-ray absorptiometry (DXA) and the hip structural analysis (HSA) software was applied to evaluate bone mineral content (BMC), areal bone mineral density (aBMD), periosteal and endosteal diameter, cortical thickness, cross-sectional moment of inertia (CSMI), section modulus (Z) and cross-sectional area (CSA) of the femoral neck (FN). Annual changes were compared. Group comparisons were done by independent student's t-test between means and analyses of covariance (ANCOVA). Pearson's correlation test was used to evaluate associations between activity level and annual changes in FN. All children remained at Tanner stage 1 throughout the study.

Results

No between-group differences were found during the 12 months study period for changes in the FN variables. The total duration of exercise during the year was not correlated with the changes in the FN traits.

Conclusion

Evaluated by the DXA technique and the HSA software, a general one-year school-based exercise program for 7–9-year-old pre-pubertal girls seems not to influence the structure of the hip.

Bone changes in adolescent girls with anorexia nervosa

PURPOSE

To clarify the effect of chronological age, height, lean tissue mass, and menstrual status on standard reported DXA (dual-energy x-ray absorptiometry) measures.

METHODS

Growth and DXA data from a retrospective longitudinal cohort of 30 adolescent females with anorexia nervosa (AN) were examined. Areal bone mineral density (aBMD), total body bone mineral content (BMC) and total body bone area were measured and standardized for age, height, lean tissue mass, and total bone area. We then examined the changes in these parameters after 12 months of multidisciplinary treatment.

RESULTS

The subjects had lower BMC and aBMD than the age- and height-matched reference population at baseline, there were further decreases in these parameters with treatment. BMC adjusted for lean tissue mass and bone area were normal at baseline and there was no significant change with treatment. Bone area adjusted for height was low at baseline and decreased despite treatment.

CONCLUSION

Our data suggest that the low age- and height-adjusted bone mineral content and bone mineral density in females with AN is secondary to poor bone growth leading to low bone area. These subjects had relatively normal bone mineral content for their bone size and lean tissue mass. Changes in bone size were proportional to changes in lean tissue mass.

Exercise, bone mass and bone size in prepubertal boys: one-year data from the pediatric osteoporosis prevention study

This non-randomized prospective controlled study evaluates a daily school-based exercise intervention program of 40 min/school day for 1 year in a population-based cohort of 81 boys aged 7-9 years. Controls were 57 age-matched boys assigned to the general school curriculum of 60 min/week. Bone mineral content (BMC; g) and areal bone mineral density (aBMD; g/cm(2)) were measured with dual X-ray absorptiometry (DXA) of the total body, the third lumbar vertebra (L3) and the femoral neck (FN). Bone width for L3 and FN was calculated from the lumbar spine and hip scan. No differences between the groups were found at baseline in age, anthropometrics or bone parameters. The mean annual gain in L3 BMC was 5.9 percentage points higher (P<0.001), L3 aBMD a mean 2.1 percentage points higher (P=0.01) and L3 width a mean 2.3 percentage points higher (P=0.001) in the cases than in the controls. When all individuals were included in one cohort, the total duration of exercise including both school-based and spare-time training correlated with L3 BMC (r=0.26, P=0.003), L3 aBMD (r=0.18, P=0.04) and L3 width (r=0.24, P=0.006). The study suggests that exercise in pre-pubertal boys influences the accrual of bone mineral and bone width and that a 1-year school-based exercise program confers skeletal benefits, at least in the lumbar spine.

A school curriculum-based exercise program increases bone mineral accrual and bone size in prepubertal girls: two-year data from the pediatric osteoporosis prevention (POP) study

This 2-year prospective controlled exercise intervention trial in 99 girls at Tanner stage 1, evaluating a school curriculum-based training program on a population-based level, showed that the annual gain in BMC, aBMD, and bone size was greater in the intervention group than in the controls.

INTRODUCTION

Most exercise intervention studies in children, evaluating the accrual of BMD, include volunteers and use specifically designed osteogenic exercise programs. The aim of this study was to evaluate a 2-year general school-based exercise intervention program in a population-based cohort of girls at Tanner stage 1.

MATERIALS AND METHODS

Forty-nine girls 7-9 years of age in grades 1 and 2 in one school were included in a school curriculum-based exercise intervention program of general physical activity for 40 minutes per school day (200 minutes/week). Fifty healthy age-matched girls in three neighboring schools, assigned to the general Swedish school curriculum of physical activity (60 minutes/week), served as controls. All girls were premenarchal, remaining in Tanner stage 1 during the study. BMC (g) and areal BMD (aBMD; g/cm2) were measured with DXA of the total body (TB), the lumbar spine (L2-L4 vertebrae), the third lumbar vertebra (L3), the femoral neck (FN), and the leg. Volumetric BMD (vBMD; g/cm3) and bone size were calculated at L3 and FN. Total lean body mass and total fat mass were estimated from the total body scan. Height and weight were also registered. Baseline measurements were performed before the intervention was initiated. Follow-up was done after 2 years.

RESULTS

No differences between the groups were found at baseline in age, anthropometrics, or bone parameters. The annual gain in BMC was greater in the intervention group than in the controls: L2-L4, mean 3.8 percentage points (p = 0.007); L3 vertebra, mean 7.2 percentage points (p < 0.001); legs, mean 3.0 percentage points (p = 0.07). The intervention group had a greater annual gain in aBMD: total body, mean 0.6 percentage points (p = 0.006), L2-L4, mean 1.2 percentage points (p = 0.02), L3 vertebra, mean 1.6 percentage points (p = 0.006); legs, mean 1.2 percentage points (p = 0.007). There was also a greater mean annual gain in bone size in the L3 vertebra (mean 1.8 percentage points; p < 0.001) and in the FN (mean 0.3 percentage points; p = 0.02).

CONCLUSIONS

A general school-based exercise program for 2 years for 7- to 9-year-old girls (baseline) enhances the accrual of BMC and BMD and increases bone size.

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

The interpretation of bone density measurement in children is difficult due to a number of factors including rapid change in body size and uncertain clinical significance of bone density in children. This study asked two questions. (1) Is there a preferred bone density measurement site or type for fracture risk in children? (2) What is the best way to interpret bone density in children? This population-based case control study included 321 upper limb fracture cases and 321 class- and sex- matched randomly selected controls. Bone density at the hip, spine, and total body (including the arm) was measured by a Hologic QDR2000 densitometer (Waltham, MA) and examined as bone area (BA), bone mineral content (BMC), bone mineral density (BMD), bone mineral apparent density (BMAD), and BMC/lean mass (BMCLM). The only dual-energy X-ray absorptiometry (DXA) variables that were consistently associated with fracture risk in both boys and girls were spine BMD and BMAD for total upper limb fractures, and spine and hip BMAD for wrist and forearm fractures. No significant associations were observed for BA and BMCLM and inconsistent associations for BMC and other BMD sites. Five-yr fracture risk varied from 15-24% depending on site and gender in a child with a Z-score of -3. In the controls, all DXA variables were associated with age, height, and weight, but the weakest associations were with BMAD. In conclusion, in this study the spine BMAD had the strongest and most consistent association with upper limb fracture risk in children. The associations with age and body size imply that age specific Z-scores will be the most convenient for interpretation of DXA measures in children. Five-yr wrist and forearm fracture risk has potential as a clinical endpoint of immediate relevance.

Daily physical education in the school curriculum in prepubertal girls during 1 year is followed by an increase in bone mineral accrual and bone width--data from the prospective controlled Malmö pediatric osteoporosis prevention study

The aim of this study was to evaluate a general school-based 1-year exercise intervention program in a population-based cohort of girls at Tanner stage I. Fifty-three girls aged 7-9 years were included. The school curriculum-based exercise intervention program included 40 minutes/school day. Fifty healthy age-matched girls assigned to the general school curriculum of 60 minutes physical activity/week served as controls. Bone mineral content (BMC, g) and areal bone mineral density (aBMD, g/cm(2)) were measured with dual X-ray absorptiometry (DXA) of the total body (TB), lumbar spine (L2-L4 vertebrae), third lumbar vertebra (L3), femoral neck (FN), and leg. Volumetric bone mineral density (g/cm(3)) and bone width were calculated at L3 and FN. Total lean body mass and total fat mass were estimated from the TB scan. No differences at baseline were found in age, anthropometrics, or bone parameters when the groups were compared. The annual gain in BMC was 4.7 percentage points higher in the lumbar spine and 9.5 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in aBMD was 2.8 percentage points higher in the lumbar spine and 3.1 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in bone width was 2.9 percentage points higher in L3 in cases than in controls (P < 0.001). A general school-based exercise program in girls aged 7-9 years enhances the accrual of BMC and aBMD and increases bone width.

Physical activity in the post-pubertal period is associated with maintenance of pre-pubertal high bone density - a 5-year follow-up

OBJECTIVE

To evaluate the association between physical activity (PA) and skeletal growth in girls during adolescence.

DESIGN

A 5-year, observational, population-based study (Reykjavik, Iceland).

SUBJECTS

Seventy-eight Caucasian girls, mean age 13.4+/-1.0 (mean+/-SD) years at baseline.

METHODS

Bone mineral density (BMD, g/cm2) and bone width (cm) were measured in the forearm by single-photon absorptiometry at baseline and with dual-energy X-ray absorptiometry after 3 and 5 years, when lumbar spine, femoral neck (FN) and total body were also evaluated. Half of the physically active girls were compared with the other half of less active girls.

RESULTS

BMD in physically active girls was higher in the forearm at both baseline (P=0.001) and after 5 years (P=0.04) in comparison with less active girls. BMD was higher for the total body (P=0.0001), spine L2-L4 (P=0.02) and FN (P=0.002) in the active girls at age 18. The accrual of forearm BMD and bone width from age 13 to 18 was no different when comparing the two groups.

CONCLUSIONS

Pre-pubertal PA is associated with high BMD at age 13 and continued PA is associated with maintenance of high BMD until age 18.

Longitudinal changes in bone density in children and adolescents with moderate to severe cerebral palsy

OBJECTIVE

To assess the natural history of "growth" in bone mineral density (BMD) in children and adolescents with moderate to severe cerebral palsy (CP).

STUDY DESIGN

A prospective, longitudinal, observational study of BMD in 69 subjects with moderate to severe spastic CP ages 2.0 to 17.7 years. Fifty-five subjects were observed for more than 2 years and 40 subjects for more than 3 years. Each evaluation also included assessments of growth, nutritional status, Tanner stage, general health, and various clinical features of CP.

RESULTS

Lower BMD z-scores at the initial evaluation were associated with greater severity of CP as judged by gross motor function and feeding difficulty, and with poorer growth and nutrition as judged by weight z-scores. BMD increased an average of 2% to 5%/y in the distal femur and lumbar spine, but ranged widely from +42%/y to -31%. In spite of increases in BMD, distal femur BMD z-scores decrease with age in this population.

CONCLUSIONS

Children with severe CP develop over the course of their lives clinically significant osteopenia. Unlike elderly adults, this is not primarily from true losses in bone mineral, but from a rate of growth in bone mineral that is diminished relative to healthy children. The efficacy of interventions to increase BMD can truly be assessed only with a clear understanding of the expected changes in BMD without intervention.

Bone metabolism in galactosemia

Classical galactosemia is an autosomal recessively inherited disorder of galactose metabolism. Treatment consists of life-long dietary restriction of galactose. Despite treatment, long-term complications occur such as a decreased bone mineral density (BMD). A decreased BMD might be the result of either dietary deficiencies secondary to the galactose-restricted diet or unknown intrinsic factors. In this study, 40 children with classical galactosemia (13 males and 27 females, aged 3-17 years) on dietary treatment were included to gain insight in the bone metabolism of galactosemics. We found weight and height Z scores significantly decreased in galactosemics. Mean areal BMD Z scores of lumbar spine and of femoral neck as measured by Dual energy X-ray Absorptiometry (DXA) were -0.6 (P < 0.001) and -0.3 (P = 0.066), respectively. Mean volumetric BMD of the femoral neck was significant lower in galactosemics (P < 0.001). The recommended dietary allowances (RDA) for calcium, magnesium, zinc, vitamin D, and protein were met in all patients. Mean serum levels of calcium, phosphate, magnesium, zinc, 1,25-dihydroxy vitamin D (1,25OHD), parathormone (PTH), 17-beta estradiol, bone alkaline phosphatase (BAP), and under-carboxylated osteocalcin (ucOC) were normal. Serum levels of IGF-1 Z score, carboxylated osteocalcin (cOC), N-terminal telopeptide (NTX), and C-terminal telopeptide (CTX) were significantly lower in galactosemics than in control subjects. The different bone markers were strongly correlated. The low levels of IGF-1 Z score, formation marker cOC, and resorption markers NTX and CTX suggest a decreased bone metabolism in galactosemics.

Sex steroid replacement during and after the induction of puberty

The main aim of sex steroid replacement during induction of puberty is to obtain a balance between healthy psychological and somatic development and optimal final height and peak bone mass (PBM). At present, the age at which it is considered appropriate to begin inducing puberty is younger than it was in the past. This trend aims for optimisation of prepubertal and pubertal growth through earlier onset of growth hormone (GH) therapy and administration of higher doses during puberty as necessary. Adequate initiation of puberty should ensure not only optimal final height and psychological balance, but also normal body proportions, appropriate bone formation and preservation of fertility for children with GH and gonadotropin deficiencies.

Pubertal bone growth in the femoral neck is predominantly characterized by increased bone size and not by increased bone density--a 4-year longitudinal study

Fragility fractures are correlated to reduced bone size and/or reduced volumetric bone density (vBMD). These region-specific deficits may originate from reduced mineral accrual and/or reduced skeletal growth during the first 2 decades of life. Before pathological development can be defined, normal skeletal growth must be described. To evaluate growth of bone size, accrual of bone mineral content (BMC), areal bone mineral density (aBMD) and vBMD in a population-based cohort, 44 boys and 42 girls were followed by annual measurements from the age of 12 to 16 (attendance rates 90-100%). Segmental bone length, bone width, BMC, aBMD and vBMD were measured by dual-energy X-ray absorptiometry (DXA). Data were compared with predicted adult peak, as determined in 36 men aged 27.7+/-4.6 years and 44 women aged 26.8+/-4.9 years. Growth in width of the femoral neck precedes accrual of BMC in the femoral neck in both genders up to age 15. The girls were at all ages closer to their predicted adult peak in both bone width and BMC compared with the boys except in the femoral neck. As femoral neck vBMD had reached its predicted adult peak already at 12 years in both genders, the increase in femoral neck BMC and femoral neck aBMD from age 12 to 16 was most likely to be explained by the increase in bone size. In boys the peak velocity growth was recorded at ~14 years for BMC, height, width and lean mass. Growth from the age of 12 to 16 seems to build a bigger but not a denser skeleton in the femoral neck.

Treatment of symptomatic pediatric osteoporosis with cyclic single-day intravenous pamidronate infusions

OBJECTIVES

To examine the response to single-day intravenous pamidronate in a heterogeneous population with symptomatic osteoporosis.

STUDY DESIGN

Patients (n = 18) 6 to 21 years of age, meeting treatment criteria were offered treatment with a single-day infusion of pamidronate every 3 months. Baseline and follow-up data were recorded and compared between persons with risk factors of progressive chronic illness or ongoing glucocorticoid usage (group 1) and persons with neither risk factor (group 2). We also examined the association between changes in urinary N-telopeptide percentile and spinal bone mineral density (BMD).

RESULTS

Spinal BMD Z score increased in all patients after 6 months of treatment. Although patients had an average of 1.9 fractures in the year preceding treatment, only 2 patients had fractures once treatment began. No significant differences in baseline data were noted between the two groups. However, group 1 had significantly less gain in BMD (P =.04) than group 2. No evidence of growth impairment was seen, and no association between changes in urinary N-telopeptide percentile and changes in BMD were noted.

CONCLUSIONS

Single-day intravenous infusion of pamidronate is efficacious and well tolerated in a heterogeneous group of pediatric patients with symptomatic osteoporosis.

Bisphosphonates to treat osteopenia in children with quadriplegic cerebral palsy: a randomized, placebo-controlled clinical trial

OBJECTIVE

To evaluate in a double-blind, placebo-controlled clinical trial the safety and efficacy of intravenous pamidronate to treat osteopenia in nonambulatory children with cerebral palsy.

STUDY DESIGN

Six pairs of subjects generally matched within each pair for age, sex, and race completed the protocol. One member of each pair randomly received plain saline placebo, the other pamidronate. Drug/placebo was administered intravenously daily for 3 consecutive days, and this 3-day dosing session was repeated at 3-month intervals for one year. Evaluations were continued for 6 months after the year of treatment. Bone mineral density (BMD) was measured in the distal femur, a site specifically developed for use in this contracted population, and the lumbar spine.

RESULTS

In the metaphyseal region of the distal femur, BMD increased 89% +/- 21% (mean +/- SEM) over the 18-month study period in the pamidronate group compared with 9% +/- 6% in the control group. Age-normalized z scores increased from -4.0 +/- 0.6 to -1.8 +/- 1.0 in the pamidronate group and did not significantly change in the control group (-4.2 +/- 0.3 to -4.0 +/- 0.3). The first dosing with pamidronate caused a transient drop in serum calcium that was asymptomatic and not treated. No other potentially adverse effects were noted.

CONCLUSIONS

In this small controlled clinical trial, pamidronate was found to be a safe and very effective agent to increase BMD in nonambulatory children with cerebral palsy.

Bone density and metabolism in children and adolescents with moderate to severe cerebral palsy

OBJECTIVES

Diminished bone density and a propensity to fracture with minimal trauma are common in children and adolescents with moderate to severe cerebral palsy (CP). The purpose of this study was to provide a detailed evaluation of bone mineral density (BMD) and metabolism in this population and to assess the relationship of these measures to multiple other clinical, growth, and nutrition variables.

METHODS

The study group consisted of 117 subjects ages 2 to 19 years (mean: 9.7 years) with moderate to severe CP as defined by the Gross Motor Functional Classification scale. Population-based sampling was used to recruit 62 of the participants, which allows for estimations of prevalence. The remaining 55 subjects were a convenience sampling from both hospital- and school-based sources. The evaluation included measures of BMD, a detailed anthropometric assessment of growth and nutritional status, medical and surgical history, the Child Health Status Questionnaire, and multiple serum analyses. BMD was measured in the distal femur, a site specifically developed for use in this contracted population, and the lumbar spine. BMD measures were converted to age and gender normalized z scores based on our own previously published control series (n > 250).

RESULTS

Osteopenia (BMD z score <-2.0) was found in the femur of 77% of the population-based cohort and in 97% of all study participants who were unable to stand and were older than 9 years. BMD was not as low in the lumbar spine (population-based cohort mean +/- standard error z score: -1.8 +/- 0.1) as in the distal femur (mean z score: -3.1 +/- 0.2). Fractures had occurred in 26% of the children who were older than 10 years. Multiple clinical and nutritional variables correlated with BMD z scores, but interpretation of these findings is complicated by covariance among variables. In stepwise regression analyses, it was found that severity of neurologic impairment as graded by Gross Motor Functional Classification level, increasing difficulty feeding the child, use of anticonvulsants, and lower triceps skinfold z scores (in decreasing order of importance) all independently contribute to lower BMD z scores in the femur.

CONCLUSIONS

Low BMD is prevalent in children with moderate to severe CP and is associated with significant fracture risk. The underlying pathophysiology is complex, with multiple factors contributing to the problem and significant variation between different regions of the skeleton.

Bone mineral density in patients with classic galactosaemia

BACKGROUND

Diminished bone mineral density (BMD) is a well known complication in women with classic galactosaemia caused by premature ovarian failure. Diminished BMD in prepubertal patients of either sex has, however, only been reported once.

AIM

To assess BMD in children with classic galactosaemia.

METHODS

Eleven treated patients (five males, six females, aged 2-18 years) had BMD determined by dual energy x ray absorptiometry. Two measurements were performed, an areal measurement of the total body and a volumetric measurement of the femoral neck. Results were expressed as Z scores. Dietary calcium intake, blood calcium, phosphate, vitamin D, parathormone, and markers of bone formation (bone alkaline phosphatase, osteocalcin) and bone resorption (NTX) were determined.

RESULTS

All patients had a significantly diminished BMD. Mean Z score of the volumetric BMD was -1.76 (range -0.7 to -3.3), and of the areal BMD -0.99 (range -0.5 to -1.4). Dietary calcium intake and calcium, phosphate, parathormone, bone alkaline phosphatase, vitamin D metabolites, and osteocalcin (free and carboxylated) were normal in all patients. NTX levels in blood were significantly lower (p < 0.001) than in control subjects.

CONCLUSION

BMD in this group of children of both sexes with classic galactosaemia under dietary treatment was decreased. Lower NTX levels in galactosaemics point to an apparent decreased bone resorption.

Bone metabolism in children with epidermolysis bullosa

We evaluated bone mineral density, vitamin D status, and biochemical markers of bone turnover in seven children with epidermolysis bullosa (EB). Four had osteopenia (Z score, -1.5) and four 25(OH) vitamin D <34 nmol/L (14 ng/mL), two of which had hyperparathyroidism. Children with severe EB should have evaluation of bone metabolism.

Assessment of forearm volumetric bone mineral density from standard areal densitometry data

The common bone density measurement procedures produce areal bone mineral density data (BMD) alone. Volumetric bone density is thought to offer a different diagnostic perspective and is usually measured by peripheral quantitative computed tomography. We developed a calculation procedure for radial and ulnar volumetric densities based on single X-ray absorptiometry. The study consisted of 418 healthy Bulgarian females (ages 20 83 yr). Forearm bone density was measured on a DTX-100 densitometer at the 8-mm distal site, and the total volumetric bone densities of radius and ulna were calculated. The accuracy error determined on cadaveric bones was 10 14%. The in vivo precision error was 1.0 1.1%. Age-matched reference curves for volumetric BMD (vBMD) were built. Peak values were registered in the age 30 34 group: 0.403 (radius) and 0.469 g/cm(3) (ulna). Ulnar volumetric density exceeded the radial one, representing an interesting finding to be further investigated. For the age 70 74 group, vBMD was reduced by approx 30% compared with the age 30 34 group. Our data confirmed the fact that volumetric density was much less affected by age and menopause. Correlations between forearm vBMD and axial BMD were moderate. The proposed calculation procedure could become an extra option in forearm bone densitometry to be applied in pediatric populations or adults of extremely large or small body size.

Total body bone mineral content and tibial cortical bone measures in preschool children

This study was undertaken to identify factors that influence total body bone area (TBBA), total body bone mineral content (TBBMC), and tibial cortical bone measures in 239 children aged 3-5 years. We obtained information on demographic and anthropometric characteristics and measurements of diet, physical activity, and strength. In multiple regression analysis, TBBA correlated with height (p < 0.001), weight (p < 0.001), percent body fat (p < 0.001), and calcium intake (p = 0.02). TBBMC correlated with TBBA (p < 0.001), age (p = 0.001), and weight (p = 0.02) and inversely correlated with height (p < 0.001) and percent body fat (p < 0.001). Children born preterm had lower TBBMC compared with children born at term (p = 0.02). Both periosteal and endosteal circumferences were correlated with weight (both,p < 0.001) and inversely correlated with age (p = 0.006 and p = 0.003, respectively) and percent body fat (p = 0.002 and p = 0.005 respectively). Endosteal circumference was greater and cortical bone area was lower in children born preterm compared with those born at term (both, p = 0.04). Findings of higher TBBA and lower TBBMC in children with high percent body fat indicate undermineralization of bone and suggest that obesity in preschool children may have detrimental effects on total body bone mass accretion. A smaller tibial periosteal circumference and thus cross-sectional area in children with the same weight but higher percent body fat also would lead to a biomechanical disadvantage in these children. Findings of low TBBMC and cortical bone area among children born preterm need to be confirmed in other populations. We speculate that differences in these measurements between children born preterm and at term may be caused by differences in activity.

Normal bone mineral density in cystic fibrosis

BACKGROUND

Osteoporosis has been reported as a complication of cystic fibrosis (CF).

AIMS

To measure bone mineral density (BMD) in non-acutely ill adults and bone mineral content (BMC) in children with CF.

METHODS

We analysed data from 28 adults and 13 children with CF. Corticosteroid use was minimal for the year prior to study in both groups. Dual x ray absorptiometry was used to measure total body and regional bone mineral density in adults. In children, whole body BMC was measured. Lean tissue mass (LTM) was also measured in all subjects. There were two control groups: A (matched for LTM and height, in addition to age and gender); and B (matched for age and gender only).

RESULTS

There was no difference in whole body or regional BMD density between adult CF patients and control A subjects. Both whole body and regional BMD were significantly lower in adult CF patients than in control B subjects. Total body BMD was correlated with body mass index, LTM, and percent fat in both CF and control subjects. There was no significant correlation between total body BMD or regional BMD and either NIH clinical status scores, or pulmonary function tests in adults. There was no difference in total body BMC between CF children and control A subjects. Total body BMC was significantly lower in CF children than in control B subjects. There was no correlation between pulmonary function results and BMC in children.

CONCLUSION

Osteopenia and osteoporosis in CF may be caused more by malnutrition and chronic use of intravenous or oral corticosteroids than by a CF related inherent defect in BMD. Appropriate "normal" data should be selected when determining whether or not osteoporosis is present in a CF patient.

Reproducibility of volume-adjusted bone mineral density of spine and hip from dual X-ray absorptiometry

Skeletal size has a confounding effect on areal bone mineral density (aBMD) related to differences in skeletal volume. Several methods have been proposed for calculating volumetric BMD (vBMD), but in vivo precision data are limited for the spine and have not been published for the hip. We prospectively performed duplicate dual X-ray absorptiometry measurements of the anteroposterior spine and hip (n = 121) in a diverse female population referred for initial clinical BMD testing. Each scan pair was performed and analyzed by two different technologists (mean interval of 4 d) to obtain standard aBMD. Scan data were reprocessed at a later date to calculate vBMD for the lumbar spine (L2-L4), femoral neck, and total hip in the 87 spines and 82 hips for which we had complete analyzable scan data. We found much worse precision in femoral neck volume (5.2% coefficient of variation [CV]) than in spine volume (2.6% CV; p < 0.003). This contributed to greater error in femoral neck vBMD (3.9% CV) than aBMD (2.3= CV; p < 10(-6)). Total hip aBMD had better precision than vBMD (1.0 and 1.3-2.5% CV; p < 10(-5)). The reverse pattern was seen in the spine with slightly better precision for vBMD than aBMD (1.1 and 1.5% CV; p < 0.002). Volumetric measures of lumbar spine density can be obtained with high precision. Because of poor reproducibility in the femoral neck, the total hip region may be preferable for measuring volumetric bone density in the proximal femur.

Bone mineral density in adolescent females with recently diagnosed anorexia nervosa

Anorexia nervosa (AN) can lead to osteoporosis and fractures.

OBJECTIVE

This study evaluated adolescent females with AN diagnosed within the previous 12 months to determine whether there is bone mass reduction and to investigate relationships between nutritional indices (weight, body mass index [BMI], lean mass, fat mass, and percentage fat) and total body (TB) and lumbar spine (LS) bone mineral densities (BMD) and content (BMC).

METHOD

TB and LS BMD and BMC and body composition were measured in 24 adolescent females with AN.

RESULTS

There was no significant reduction in TB or LS BMD. Regression analysis shows significant correlation (p < 0.001) between lean mass and TB BMD (r = +0.83), TB BMC (r = +0.92), LS BMD (r = +0.81), and LS BMC (r = +0.92). There was also a significant relationship between weight percentile and LS BMD z score (p < 0.005; r = +0.60).

DISCUSSION

Adolescent females with early AN do not appear to have reduced bone mass. Lean mass is correlated to BMD and BMC.

Role of calcium in bone health during childhood

A discussion of observational and longitudinal studies examining the effect of early-life calcium intake on bone health is provided. A critical analysis of pediatric calcium supplementation trials is conducted by determining annualized percent changes in bone mineral density (BMD). The focus of the analysis is to identify consistent findings at specific bone sites, determine whether effects differed by the age of children studied, and establish the relationship between bone changes and baseline calcium intake. We found that increases in BMD owing to higher calcium intake among children appear to occur primarily in cortical bone sites, are most apparent among populations with low baseline calcium intakes, and do not seem to persist beyond the calcium supplementation period. Older (e.g., pubertal) children appear to have greater annual increases in lumbar BMD than younger (e.g., prepubertal) children. The annual percent increase in midradius BMD appears to be greater at higher intakes among the older children, but such a relationship is less apparent among the younger children.

Growth, development and differentiation: a functional food science approach

Few other aspects of food supply and metabolism are of greater biological importance than the feeding of mothers during pregnancy and lactation, and of their infants and young children. Nutritional factors during early development not only have short-term effects on growth, body composition and body functions but also exert long-term effects on health, disease and mortality risks in adulthood, as well as development of neural functions and behaviour, a phenomenon called 'metabolic programming'. The interaction of nutrients and gene expression may form the basis of many of these programming effects and needs to be investigated in more detail. The relation between availability of food ingredients and cell and tissue differentiation and its possible uses for promoting health and development requires further exploration. The course of pregnancy, childbirth and lactation as well as human milk composition and the short- and long-term outcome of the child are influenced by the intake of foods and particularly micronutrients, e.g. polyunsaturated fatty acids, Fe, Zn and I. Folic acid supplementation from before conception through the first weeks of pregnancy can markedly reduce the occurrence of severe embryonic malformations; other potential benefits of modulating nutrient supply on maternal and child health should be further evaluated. The evaluation of dietary effects on child growth requires epidemiological and field studies as well as evaluation of specific cell and tissue growth. Novel substrates, growth factors and conditionally essential nutrients (e.g. growth factors, amino acids, polyunsaturated fatty acids) may be potentially useful as ingredients in functional foods and need to be assessed carefully. Intestinal growth, maturation, and adaptation as well as long-term function may be influenced by food ingredients such as oligosaccharides, gangliosides, high-molecular-mass glycoproteins, bile salt-activated lipase, pre- and probiotics. There are indications for some beneficial effects of functional foods on the developing immune response, for example induced by antioxidant vitamins, trace elements, fatty acids, arginine, nucleotides, and altered antigen contents in infant foods. Peak bone mass at the end of adolescence can be increased by dietary means, which is expected to be of long-term importance for the prevention of osteoporosis at older ages. Future studies should be directed to the combined effects of Ca and other constituents of growing bone, such as P, Mg and Zn, as well as vitamins D and K, and the trace elements F and B. Pregnancy and the first postnatal months are critical time periods for the growth and development of the human nervous system, processes for which adequate substrate supplies are essential. Early diet seems to have long-term effects on sensory and cognitive abilities as well as behaviour. The potential beneficial effects of a balanced supply of nutrients such as I, Fe, Zn and polyunsaturated fatty acids should be further evaluated. Possible long-term effects of early exposure to tastes and flavours on later food choice preferences may have a major impact on public health and need to be further elucidated. The use of biotechnology and recombinant techniques may offer the opportunity to include various bioactive substances in special dietary products, such as human milk proteins, peptides, growth factors, which may have beneficial physiological effects, particularly in infancy and early childhood.