Lumbar spine bone density in Argentine children

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.

Normative data and percentile curves for Dual Energy X-ray Absorptiometry in healthy Indian girls and boys aged 5-17 years

For the correct interpretation of Dual Energy X-ray Absorptiometry (DXA) measurements in children, the use of age, gender, height, weight and ethnicity specific reference data is crucially important. In the absence of such a database for Indian children, the present study aimed to provide gender and age specific data on bone parameters and reference percentile curves for the assessment of bone status in 5-17 year old Indian boys and girls. A cross sectional study was conducted from May 2006 to July 2010 on 920 (480 boys) apparently healthy children from schools and colleges in Pune City, India. The GE-Lunar DPX Pro Pencil Beam DXA scanner was used to measure bone mineral content (BMC [g]), bone area (BA [cm(2)]) and bone mineral density (BMD [g/cm(2)]) at total body, lumbar spine and left femur. Reference percentile curves by age were derived separately for boys and girls for the total body BMC (TBBMC), total body BA (TBBA), lumbar spine bone mineral apparent density (BMAD [g/cm(3)]), and left femoral neck BMAD. We have also presented percentile curves for TBBA for height, TBBMC for TBBA, LBM for height and TBBMC for LBM for normalizing bone data for Indian children. Mean TBBMC, TBBA and TBBMD were expressed by age groups and Tanner stages for boys and girls separately. The average increase in TBBMC and TBBA with age was of the order of 8 to 12% at each age group. After 16 years of age, TBBMC and TBBA were significantly higher in boys than in girls (p<0.01). Maximal increase in TBBMD occurred around the age of 13 years in girls and three years later in boys. Reference data provided may be used for the clinical assessment of bone status of Indian children and adolescents.

Response to zolendronic acid in children with type III osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a common genetic disorder that manifests with intrauterine or pre- or postnatal fractures, blue sclera, and deafness. Various treatments for the management of OI have been tried, of which bisphosphonates (BPs) seem to have the maximum benefit in reducing fracture rate and improving bone density. Zolendronic acid is a newer BP tried for several bone diseases, mainly in adults. The objective of our analysis was to study the response to zolendronic acid in children with type III OI. The case records of subjects with type III OI receiving zolendronic acid in the past 3 years between February 2006 and March 2009 were analyzed. Relevant details were recorded on a predesigned chart. Subjective improvement, reduction in number of fractures, and the DEXA scan Z-score were used to judge improvement. Five OI type III cases were followed up in the Genetic clinic. Presentation was from neonatal period to 7 years of age; M:F ratio was 3:2. Average duration of therapy given was 20.4 months. Improvement was noted in all patients, in the form of reduction in frequency of fractures (P = 0.002) and increase in bone density on DEXA scan (P = 0.01). Side effects noted were flu-like symptoms and myalgia. No clinical problems due to hypocalcemia were noted in any of the patients. Thus, zolendronic acid is seen as a safe and effective BP in type III OI children. The exact dose for optimal benefit is yet to be determined. The long-term effects of newer BPs need further long-term trials.

Cyclic pamidronate therapy in children with osteogenesis imperfecta

BACKGROUND

Severe osteogenesis imperfecta (OI) is a disorder characterized by osteopenia, frequent fractures, progressive deformity, loss of mobility, and chronic bone pain. There has been no effective therapy for the disorder until recently. The main objective of this study was to determine the efficacy and safety of pamidronate in improving bone mineralization and reducing fracture incidence in osteogenesis imperfecta.

METHODS

Intravenous pamidronate was administered to 64 children (from 21 months to 10 years old) with severe OI, in a 1 mg/kg single daily dose for 3 sequential days at 4-month intervals, over 24-48 months duration. Clinical status, biochemical characteristics including bone turnover markers, bone mineral density of the lumbar spine and femoral neck, and radiological changes were assessed regularly during treatment.

RESULTS

The number of fractures decreased from a median of 8 (range 4-11) to 0 fractures/year (range 0-4) (p <0.05). After 16 months of treatment, there was significant improvement in bone mineral density (BMD-DEXA) z-score of the lumbar spine from a median of -5.90 (range -7.01 to -4.76) to -2.70 (range -4.46 to -1.98) (p <0.001). Serum alkaline phosphatase (ALP) (bone formation marker) decreased from a median of 731.0 U/l (range 438-998 U/l) to 183 U/l (range 95-286 U/l) (p <0.001), implying a significant reduction in bone turnover and resorption and increase in bone mineralization. There was no improvement in growth velocity or height SDS. Mobility and ambulation improved in all but five children (all five had taken the drug for less than 2.5 years). There was a significant relief of chronic pain and fatigue but no adverse effects in all children using the drug.

CONCLUSION

Cyclic pamidronate administration is effective in improving bone mineralization and reducing fracture incidence in childhood osteogenesis imperfecta.

Treatment and management of osteoporosis-pseudoglioma syndrome

Osteoporosis-pseudoglioma syndrome (OPPG; MIM 259770) is a very rare genetic disorder with an autosomal recessive mode of inheritance, characterized by congenital or infancy-onset visual loss and skeletal fragility, diagnosed during childhood. This syndrome can lead to severe disability and chronic bone pain. Low-density lipoprotein receptor-related protein 5 (LRP5) is the gene mutated and inactivated in OPPG, and plays a pivotal role in bone accrual and skeletal remodeling by controlling bone formation through activators, such as Wnt proteins, or inhibitors, such as DKK1. OPPG should be differentiated from osteogenesis imperfecta and child abuse by clinicians. Eye examination, coupled to bone phenotype and research of LRP5 mutation, are key points to diagnose OPPG. Chronic pain should be managed correctly in this syndrome with severe functional disability. Bisphosphonates allows fracture prevention, the catch-up of bone mineral density and improvement in mobility in children with OPPG. New drugs favoring osteoblast function and osteoclast inhibition are potential candidates in the treatment of OPPG.

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.

Effect of alendronate therapy in children with osteogenesis imperfecta

OBJECTIVE

To evaluate the effect of orally administered alendronate in children with osteogenesis imperfecta.

METHODS

Thirty children (16 girls and 14 boys; mean age at baseline 10.7 +/- 6.0 years; range 4-16 years) with osteogenesis imperfecta type I (n = 22), III (n = 2), or IV (n = 6) were treated with alendronate (5 mg/day in patients aged 4-10 years and 10 mg/day in children >10 years of age) for 3 years.

RESULTS

After 1 year of alendronate therapy we observed a significant increase in areal and volumetric bone mineral density Z-scores (from -2.03 +/- 1.51 to -1.04 +/- 1.20, and from -1.91 +/- 1.38 to -1.33 +/- 1.30, respectively, P < 0.001), together with a significant drop in fracture rate (from 3.77 +/- 1.57 to 0.13 +/- 0.57, P < 0.000001), relief of chronic pain (from 3.83 +/- 1.44 days of pain/week to 0.73 +/- 0.77, P < 0.000001) and improvement in ambulation/mobility (P < 0.00002). After additional 2 years of therapy there were no further significant changes in these parameters, however the improvement was still remarkable in comparison to the pretreatment values (P < 0.003, P < 0.004, P < 0.000001, P < 0.000001 and P < 0.00001, respectively). A significant drop in markers of bone turnover (urinary deoxypyridinoline and serum osteocalcin) occurred after 3 years of therapy (P < 0.003 and 0.004, respectively). No adverse reactions were observed throughout the treatment.

CONCLUSIONS

Alendronate has positively influenced quality of life in paediatric patients with osteogenesis imperfecta. Bisphosphonate therapy should be used only in the context of a well-defined protocol.

Osteoporosis and measurement of bone mass in children and adolescents

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

Bone densitometry in pediatric populations: discrepancies in the diagnosis of osteoporosis by DXA and CT

OBJECTIVES

To test the hypothesis that because of errors associated with growth and development, osteoporosis is frequently overdiagnosed in children when using dual-energy x-ray absorptiometry (DXA). This study compared bone density values obtained by DXA with those from computed tomography (CT), which is not influenced by body or skeletal size.

STUDY DESIGN

Vertebral bone density was measured by using both DXA and CT in 400 children (100 each, healthy and sick boys and girls). Regression analysis was used to compare DXA and CT Z scores, and the agreement between DXA and CT classifications of Z scores below -2.0 was examined.

RESULTS

DXA and CT Z scores were moderately related (r2 = 0.55 after accounting for age and anthropometric measures). DXA Z scores predicted CT Z scores below -2.0 with reasonable sensitivity (72%), specificity (85%), and negative predictive value (98%), but positive predictive value was low (24%). Many more subjects were classified as having bone density lower by DXA (76/400) than by CT (25/400), particularly subjects below the 5 th percentile of height and/or weight for age.

CONCLUSIONS

The inability of DXA to account for the large variability in skeletal size and body composition in growing children greatly diminishes the accuracy of this projection technique for assessing bone acquisition and diagnosing osteoporosis in pediatric populations.

Assessment of bone mass following renal transplantation in children

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

Bone mineral density in girls and boys at different pubertal stages: relation with gonadal steroids, bone formation markers, and growth parameters

Puberty has a key role in bone development. During puberty, several nutritional and hormonal factors play a major role in this process. The aim of this study was to determine the changes in areal bone mineral density (BMD), gonadal steroids, bone formation markers, and growth parameters in healthy Turkish pubertal girls and boys at different pubertal stages. In additional, we aimed to detect the relationship between BMD, sex steroids, and growth parameters, and to reveal the most important determinant of BMD in the pubertal period. BMD of the lumbar spine and total body was performed by dual-energy X-ray absorptiometry (Lunar DPX series) in 174 healthy pubertal children (91 girls, 83 boys), aged 11-15 years. Height and weight were measured. Pubertal stages were assesed. Bone formation markers and gonadal steroids were measured. BMD values significantly increased until stage IV in girls. In boys, BMD values also increased during puberty (P < 0.05), but it was significantly higher in stage IV compared with that in other pubertal stages (P < 0.01). Testosterone levels increased until stage IV in both sexes, particularly in boys. Estrogen levels significantly increased during puberty in girls, whereas it was significantly higher at stage IV in boys (P < 0.001). Bone-specific alkaline phosphatase (BAP) level was higher in early and midpuberty, and decreased in late puberty in girls (P < 0.001). BAP level was higher in stage IV in boys. Osteocalcin level was shown not to change significantly in pubertal stages. There was a modest correlation between BMD values and estrogen and testosterone levels in boys. In girls, there was a correlation between BMD values and estrogen levels only (P < 0.05). Weight was significantly associated with BMD in both sexes (P < 0.05). Estrogen had a significant influence on BMD in boys and girls. In conclusion, bone mass increased throughout puberty in both sexes. Peak bone mass was not achieved in girls, but was obtained at stage IV in boys. Bone formation markers were good predictors of bone mass in girls, but not in boys. Estrogen level made the greatest contribution to bone mineral acquisition in boys and girls. The achievement of peak bone mass was sustained by estrogen in boys. The major independent determinant of BMD in both sexes was weight.

Bone disease in pediatric rheumatologic disorders

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

Effect of cyclical intravenous pamidronate therapy in children with osteogenesis imperfecta. Open-label study in seven patients

OBJECTIVES

To evaluate the efficacy of pamidronate in protecting against fractures, increasing bone mineral density (BMD), and decreasing bone remodeling marker levels in children with osteogenesis imperFecta.

PATIENTS AND METHODS

Seven children (two girls and five boys; mean age, 8.5 years) were given cyclical intravenous pamidronate (Aredia) for 1 to 7 years, with a mean cycle duration of 6 months and a mean dose of 1.86 mg/kg/cycle. Four patients had type III and three type IV disease according to the Sillence classification scheme.

RESULTS

A trend toward a decrease in the fracture rate as compared to the pretreatment period was found, but the difference was not significant in this small sample (P = 0.09). Lumbar spine BMD showed a significant annual increase (+26.7%, P = 0.03) far greater than the expected mean annual increase related to growth. No significant decreases in bone remodeling markers were noted.

CONCLUSION

Pamidronate seems useful in the treatment of osteogenesis imperfecta in children, since it increases BMD and reduces the fracture rate, in keeping with the findings from the larger series studied by Glorieux. Pamidronate is a symptomatic, noncurative treatment that does not correct the genetic abnormalities responsible for the histological bone alterations.

Reference data for bone density and body composition measured with dual energy x ray absorptiometry in white children and young adults

AIMS

To obtain normative data on bone mineral density and body composition measured with dual energy x ray absorptiometry (DXA) from early childhood to young adulthood.

METHODS

Cross sectional results from 444 healthy white volunteers (4-20 years) in the Netherlands were combined with the results from 198 children who agreed to participate in the follow up study approximately four years later. DXA (Lunar, DPXL) of lumbar spine and total body was performed to assess bone density and body composition.

RESULTS

Bone density and lean body mass (LBM) increased with age. Maximal increase in bone density and LBM occurred around the age of 13 years in girls and approximately two years later in boys. Bone density of total body and lumbar spine showed an ongoing slight increase in the third decade. Mean fat percentage in boys remained at 10.5% throughout childhood, but increased in girls.

CONCLUSIONS

Most of the skeletal mass in lumbar spine and total body is reached before the end of the second decade, with a slight increase thereafter. This study provides reference values for bone density and body composition measured with DXA for children and young adults.

Current concepts in pediatric bone disease

It is widely believed that osteoporosis prevention may be best accomplished during childhood and adolescence, when bones are growing rapidly and are most sensitive to environmental influences, such as diet and physical activity. For children with chronic diseases, a variety of factors may influence normal bone mineralization, including altered growth, delayed maturation, inflammation, malabsorption, reduced physical activity, glucocorticoid exposure, and poor dietary intake. In healthy children, maintaining adequate levels of calcium intake, serum vitamin D, and weightbearing physical activity may be sufficient to prevent osteoporosis later in life. Far less is known about effective prevention and treatment of poor bone mineralization in children with chronic illness, such as CF or CD. Osteoporosis prevention and intervention measures during childhood are limited by the paucity of reference data on bone mineralization. Although it is widely recognized that puberty, skeletal maturation, and body size influence BMC and bone density, no reference data for bone mineralization are scaled to these important measures. In children with chronic disease with delayed growth and maturation, the creation of such reference data is of paramount importance. In addition, the dynamic changes that occur during growth and maturation in the structural characteristics of trabecular and cortical bone and the development of the bone-muscle unit may influence current and future fracture risk. Further research is needed to characterize these changes and their use in the assessment of bone health and fracture risk in children. Only then can the impact of treatment strategies be appreciated fully.

Genetic determination of Colles' fracture and differential bone mass in women with and without Colles' fracture

Osteoporotic fractures (OFs) are a major public health problem. Direct evidence of the importance and, particularly, the magnitude of genetic determination of OF per se is essentially nonexistent. Colles' fractures (CFs) are a common type of OF. In a metropolitan white female population in the midwestern United States, we found significant genetic determination of CF. The prevalence (K) of CF is, respectively, 11.8% (+/- SE 0.7%) in 2471 proband women aged 65.55 years (0.21), 4.4% (0.3%) in 3803 sisters of the probands, and 14.6% (0.7%) in their mothers. The recurrence risk (K0), the probability that a woman will suffer CF if her mother has suffered CF is 0.155 (0.017). The recurrence risk (Ks), the probability that a sister of a proband woman will suffer CF given that her proband sister has suffered CF is 0.084 (0.012). The relative risk lambda (the ratio of the recurrence risk to K), which measures the degree of genetic determination of complex diseases such as CF, is 1.312 (0.145; lambda 0) for a woman with an affected mother and 1.885 (0.276; lambda s) for a woman with an affected sister. A lambda-value significantly greater than 1.0 indicates genetic determination of CF. The terms lambda 0 and lambda s are related to the genetic variances of CF. These parameters translate into a significant and moderately high heritability (0.254 [0.118]) for CF. These parameters were estimated by a maximum likelihood method that we developed, which provides a general tool for characterizing genetic determination of complex diseases. In addition, we found that women without CF had significantly higher bone mass (adjusted for important covariates such as age, weight, etc.) than women with CF.

Discrepancies in pediatric bone mineral density reference data: potential for misdiagnosis of osteopenia

OBJECTIVE

To evaluate published pediatric dual-energy x-ray absorptiometry bone mineral density (BMD) reference data by comparing the diagnostic classification of measured BMD in children at risk for osteopenia as healthy or osteopenic according to reference source.

STUDY DESIGN

Spine BMD was measured in 95 children, ages 9 to 15 years, at risk for osteopenia because of childhood disease. The BMD results were converted to age-specific z scores for each of the 5 reference data sets, and the z -score distributions were compared.

RESULTS

Between 11% and 30% of children were classified as osteopenic (z score < -2.0) depending on the reference data set. The 2 sex-specific reference data sets yielded similar diagnostic classification of boys and girls: 10% of boys and 11% to 16% of girls were osteopenic (P =.4). The 3 sex-nonspecific reference data sets classified 9% to 13% of girls and 24% to 44% of boys as osteopenic; the diagnosis of osteopenia was significantly greater in boys (P <.01).

CONCLUSIONS

The use of different published reference data for the assessment of children at risk for osteopenia results in inconsistent diagnostic classification of BMD results. These inconsistencies can be partially attributed to sex-nonspecific reference data that result in misclassification of boys as osteopenic.

Bone mineral density in children and young adults with Crohn's disease

Reduced bone mineral density (BMD) has been reported in adults with Crohn's disease (CD). Less is known about abnormal BMD in children and young adults with CD. The aims of this study are to determine the prevalence of low BMD and to evaluate the effect of growth and pubertal development on BMD in children and young adults with CD. One hundred-nineteen patients with CD underwent dual-energy X-ray absorptiometry (DXA) to determine BMD. Anthropometry and pubertal development were measured. Bone age was measured only in patients older than 8 years of age and who had not grown in height during the last year. One hundred-nineteen patients (72 male, 47 female) were evaluated. Seventy percent of patients had BMD z-scores < or = -1.0 and 32% had z-scores < or = -2.0. Weight and height z-scores were significantly associated with BMD z-scores. BMD z-scores based on bone age and on chronological age were highly correlated, except when the chronological age BMD z-score was < or = -2.0. BMD z-score was significantly different between males and females for the group (-1.75 +/- 1.06 vs. -1.08 +/- 1.00), respectively. Children and young adults with CD have a high prevalence of low BMD and routine evaluation by DXA is indicated. In patients with a chronological age-based BMD z-score < or = -2.0, a bone age-based BMD should be considered.

Cyclic administration of pamidronate in children with severe osteogenesis imperfecta

BACKGROUND

Severe osteogenesis imperfecta is a disorder characterized by osteopenia, frequent fractures, progressive deformity, loss of mobility, and chronic bone pain. There is no effective therapy for the disorder. We assessed the effects of treatment with a bisphosphonate on bone resorption.

METHODS

In an uncontrolled observational study involving 30 children who were 3 to 16 years old and had severe osteogenesis imperfecta, we administered pamidronate intravenously (mean [+/-SD] dose, 6.8+/-1.1 mg per kilogram of body weight per year) at 4-to-6-month intervals for 1.3 to 5.0 years. Clinical status, biochemical characteristics reflecting bone turnover, the bone mineral density of the lumbar spine, and radiologic changes were assessed regularly during treatment.

RESULTS

Administration of pamidronate resulted in sustained reductions in serum alkaline phosphatase concentrations and in the urinary excretion of calcium and type I collagen N-telopeptide. There was a mean annualized increase of 41.9+/-29.0 percent in bone mineral density, and the deviation of bone mineral density from normal, as indicated by the z score, improved from -5.3+/-1.2 to -3.4+/-1.5. The cortical width of the metacarpals increased by 27+/-20.2 percent per year. The increases in the size of the vertebral bodies suggested that new bone had formed. The mean incidence of radiologically confirmed fractures decreased by 1.7 per year (P<0.001). Treatment with pamidronate did not alter the rate of fracture healing, the growth rate, or the appearance of the growth plates. Mobility and ambulation improved in 16 children and remained unchanged in the other 14. All the children reported substantial relief of chronic pain and fatigue.

CONCLUSIONS

In children with severe osteogenesis imperfecta, cyclic administration of intravenous pamidronate improved clinical outcomes, reduced bone resorption, and increased bone density.

Gender-related differences in the relationship between densitometric values of whole-body bone mineral content and lean body mass in humans between 2 and 87 years of age

The mineral, lean, and fat contents of the human body may be not only allometrically but also functionally associated. This report evaluates the influence of muscle mass on bone mass and its age-related changes by investigating these and other variables in both genders in the different stages of reproductive life. We have analyzed the dual-energy X-ray absorptiometry (DEXA)-determined whole-body mineral content (TBMC), lean body mass (LBM), and fat body mass data (FBM) of 778 children and adolescents of both genders, aged 2-20 years [previously reported in Bone 16(Suppl.): 393S-399S; 1995], and of 672 age-matched men and women, aged 20-87 years. Bone mass (as assessed by TBMC) was found to be closely and linearly associated with muscle mass (as reflected by LBM) throughout life. This relationship was similar in slope and intercept in prepubertal boys and girls. However, while keeping the same slope of that relationship (50-54 g increase in TBMC per kilogram LBM): (1) both men and women stored more mineral per unit of LBM within the reproductive period than before puberty (13%-29% and 33%-58%, respectively); (2) women stored more mineral than age-matched men with comparable LBM (17%-29%) until menopause; and (3) postmenopausal women had lower values of bone mineral than premenopausal women, similar to those of men with comparable LBM. Men showed no age effect on the TBMC/LBM relationship after puberty. Multiple regression analyses showed that not only the LBM, but also the FBM and body height (but not body weight), influenced the TBMC, in that decreasing order of determining power. However, neither the FBM nor body height could explain the pre/postpubertal and the gender-related differences in the TBMC/LBM relationship. Accordingly: (1) calculated TBMC/LBM and FBM-adjusted TBMC/LBM ratios were lower in girls and boys from 2-4 years of age until puberty; (2) thereafter, females rapidly reached significantly higher ratios than age-matched men until menopause; and (3) then, ratios for women and age-matched men tended to equalize. A biomechanical explanation of those differences is suggested. Sex hormones or related factors could affect the threshold of the feedback system that controls bone remodeling to adapt bone structure to the strains derived from customary mechanical usage in each region of the skeleton (bone "mechanostat"). Questions concerning whether the mineral accumulation in women during the reproductive period is related or not to an eventual role in pregnancy or lactation, or whether the new bone is stored in mechanically optimal or less optimal regions of the skeleton, are open to discussion.

Bone density in children: a review of the available techniques and indications

The recent development of methods for measuring bone mineral content in children has markedly improved our ability to determine changes in bone mass during growth. Currently, the three most generally accepted techniques for measuring the bones of children are dual-energy X-ray absorbtiometry (DXA), quantitative computed tomography (QCT) and quantitative ultrasound (QUS). These techniques vary considerably in their acquisition of data and comparisons between them are difficult and, more often than not, judgment regarding their value has been, at least partially, subjective. DXA is, by far, the most widely used technique for bone measurements. It is low in cost, accessible, easy to use, and provides an accurate and precise quantitation of bone mass in adults. Unfortunately, DXA is unable to account for the large changes in body and skeletal size that occur during growth, limiting its use in longitudinal studies in children. QCT can asses both the volume and the density of bone in the axial and appendicular skeletons, without influence from body or skeletal size, giving it a major advantage over other modalities for bone measurements in children. The cost and inaccessibility of CT scanners, however, has significantly limited its use for bone measurements. Measuring the bones of children by QUS is appealing because ultrasound is low in cost, portable, easy to use and does not emit radiation. In adults, this technique is able to predict fracture risk independent of bone mass determinations in patients with osteoporosis and, therefore, its measurements must be related to certain aspects of bone strength. However, ultrasound values are dependent on so many structural properties not yet fully understood, that it is difficult to use the information meaningfully in children.