Lumbar bone mineral content measured by dual energy X-ray absorptiometry in newborns and infants

Bone mineral density and geometric morphometrics: Indicators of growth in the immature pars basilaris

The pars basilaris forms a central component of the immature basicranium and owing to its resilience to post-mortem and taphonomic changes, holds significance across evolutionary, clinical, and forensic contexts. While size and shape parameters of the pars basilaris have been investigated, little is known about the influence of the underlying bone mineral density on the morphometry of this bone during growth. This study aimed to investigate the development and growth of the pars basilaris with specific reference to changes in bone density patterning and development of osteological features, during the prenatal and early postnatal periods of life. A total of 109 pars basilari were sourced from the Johannesburg Forensic Paediatric Collection, University of the Witwatersrand, South Africa. The study sample was subdivided into early prenatal (<30 gestational weeks), prenatal (30-40 gestational weeks) and postnatal (birth to 7.5 months) groups and micro-CT scanned to assess bone mineral density patterns across seven regions of interest. Size and shape changes were analysed using 11 digitized landmarks and geometric morphometrics. When comparing across age groups, the assessed dimensions increased with growth manifesting as a deepening at the anterior border of the foramen magnum, development of the lateral angles and widening of the bone at the lateral projections and spheno-occipital synchondrosis. However, no significant changes in the distribution of bone mineral density were observed. An appreciation of morphological changes and bone quality at specific growth sites in the pars basilaris is essential when analyzing remains of unknown provenance for the purposes of identification in disaster victim settings.

Assessing the morphology and bone mineral density of the immature pars lateralis as an indicator of age

Age estimation is crucial when the state of personhood is a mitigating factor in the identification of immature human remains. The maturation sequence of immature bones is a valuable alternative to dental development and eruption standards. Bordering the foramen magnum and pars basilaris, the pars lateralis is somewhat understudied. The aim of this study was to comprehensively describe the morphology of the immature human pars lateralis bone. Human pars laterali were sourced from the crania of 103 immature individuals of unknown provenance from the Johannesburg Forensic Paediatric Collection (JFPC), University of the Witwatersrand (HREC-Medical: M210855). The study sample was subdivided into early prenatal (younger than 30 gestational weeks; n = 32), prenatal (30-40 gestational weeks, n = 41) and postnatal (birth to 7.5 months, n = 30) age groups. The morphology of the pars laterali was studied using a combination of bone mineral density pattern assessments, geometric morphometrics and stereomicroscopy. Bone mineral density in postnatal individuals was lower when compared with the prenatal individuals. No statistically significant differences between density points were noted. The overall shape of the pars lateralis changed from a triangular shape in the early prenatal individuals to a fan-like quadrilateral bone in postnatal individuals. The angulation of the medial border for the foramen magnum highlighted a change in shape between straight in the early prenatal cohort to V-shaped in the postnatal individuals. The various technical approaches used in the current study provided detailed descriptions of the pars lateralis which establishes a valuable foundation for diagnostic criteria employing morphological predictors for biological profiling.

Calvarial doughnut lesions with bone fragility in a French-Canadian family; case report and review of the literature

Calvarial Doughnut Lesions with Bone Fragility (CDL) is an autosomal dominant genetic disease, characterized by low bone mineral density, multiple fractures starting in childhood, and sclerotic doughnut-shaped lesions in the cranial bones. Aubé and colleagues described in 1988 a French-Canadian family of 12 affected members who had a clinical diagnosis of doughnut lesions of the skull, with pathological fractures, osteopenia, "bone in bone" in the vertebral bodies and squaring of metatarsal and metacarpal bones. Herein we study new members of this family. Sequential genetic testing identified a nonsense variant c.148C>T, p. Arg50^⁎ in SGMS2 previously reported in other families. SGMS2 encodes Sphingomyelin Synthase 2, which produces Sphingomyelin (SM), a major lipid component of the plasma membrane that plays a role in bone mineralization. The nonsense variant is associated with milder phenotype. The proband presents with bone in bone vertebral appearance that had been defined uniquely in the first cases described in the same family. The proband's son was identified to carry the same variant, which makes him the sixth generation with the diagnosis of CDL. We also report that the same pathogenic variant was identified in another previously described family, from France. These reports further confirm the genetic basis of CDL, the recurrence of the same variant (p.Arg50*) in individuals of the same ancestry, and the variable penetrance of some of the clinical findings.

Analysis of Circulating Mediators of Bone Remodeling in Prader-Willi Syndrome

We tested the hypothesis that the levels of bone remodeling mediators may be altered in Prader-Willi syndrome (PWS). We assessed RANKL, OPG, sclerostin, DKK-1 serum levels, and bone metabolism markers in 12 PWS children (7.8 ± 4.3 years), 14 PWS adults (29.5 ± 7.2 years), and 31 healthy controls matched for sex and age. Instrumental parameters of bone mineral density (BMD) were also evaluated. Lumbar spine BMD Z-scores were reduced in PWS children (P < 0.01), reaching osteopenic levels in PWS adults. PWS patients showed lower 25(OH)-vitamin D serum levels than controls (P < 0.001). Osteocalcin was increased in PWS children but reduced in adults respect to controls (P < 0.005 and P < 0.01, respectively). RANKL levels were higher in both pediatric and PWS adults than controls (P < 0.004), while OPG levels were significantly reduced (P < 0.004 and P < 0.006, respectively). Sclerostin levels were increased in children (P < 0.04) but reduced in adults compared to controls (P < 0.01). DKK-1 levels did not show significant difference between patients and controls. In PWS patients, RANKL, OPG, and sclerostin significantly correlated with metabolic and bone instrumental parameters. Consistently, with adjustment for age, multiple linear regression analysis showed that BMD and osteocalcin were the most important predictors for RANKL, OPG, and sclerostin in children, and GH and sex steroid replacement treatment in PWS adults. We demonstrated the involvement of RANKL, OPG, and sclerostin in the altered bone turnover of PWS subjects suggesting these molecules as markers of bone disease and new potential pharmacological targets to improve bone health in PWS.

Sexual Dimorphism and the Origins of Human Spinal Health

Recent observations indicate that the cross-sectional area (CSA) of vertebral bodies is on average 10% smaller in healthy newborn girls than in newborn boys, a striking difference that increases during infancy and puberty and is greatest by the time of sexual and skeletal maturity. The smaller CSA of female vertebrae is associated with greater spinal flexibility and could represent the human adaptation to fetal load in bipedal posture. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities. This review summarizes the potential endocrine, genetic, and environmental determinants of vertebral cross-sectional growth and current knowledge of the association between the small female vertebrae and greater risk for a broad array of spinal conditions across the lifespan.

Long-term follow-up in osteogenesis imperfecta type VI

This retrospective study on long-term outcomes in osteogenesis imperfecta type VI found that patients who received intravenous bisphosphonate treatment had an increase in lumbar spine areal bone mineral density, a higher final height z-score, and some reshaping of vertebral bodies.

INTRODUCTION

Osteogenesis imperfecta (OI) type VI is an ultra-rare bone fragility disorder caused by recessive mutations in SERPINF1. Here, we describe long-term outcomes in OI type VI and compare the clinical phenotypes caused by different types of SERPINF1 mutations.

METHODS

This study includes a retrospective chart review of 13 individuals with OI type VI.

RESULTS

In the absence of therapy, lumbar spine areal bone mineral density (BMD) did not increase during childhood and longitudinal growth seemed to stall after the age of 6 to 8 years. The phenotype was similar between individuals with different types of SERPINF1 mutations. Intravenous bisphosphonate treatment was associated with an increase in lumbar spine areal BMD and some reshaping of compressed vertebral bodies. Patients who had started bisphosphonate treatment early (before the age of 6 years) were taller than patients who had received bisphosphonate treatment later during their growing years. Lower extremity fractures were frequent despite bisphosphonate treatment and scoliosis was present in all patients who had reached the final height. Most patients had restricted mobility. In four patients, intravenous bisphosphonate treatment was eventually substituted by subcutaneous injections of denosumab, without clear changes in the clinical picture.

CONCLUSIONS

Patients with OI type VI who received intravenous bisphosphonate treatment during growth had an increase in lumbar spine areal BMD, a higher final height z-score, and presented some reshaping of vertebral bodies. More effective treatment modalities are clearly required in OI type VI.

Risk factors of metabolic bone disease of prematurity

OBJECTIVE

To identify the factors that increase risk of metabolic bone disease of prematurity (MBD).

STUDY DESIGN

A retrospective case-control study of infants born between January 2013-April 2014 with gestation age <30weeks and birth weight <1000g. MBD was defined as serum alkaline phosphatase above 500U/L and characteristic radiographic changes. Information was obtained on the presence of specific comorbidities.

RESULTS

Of 76 infants evaluated, 40 met criteria for MBD. Median gestational age was 25weeks in both groups (p=0.512). Median birth weight of infants with MBD was significantly lower than that of controls (560 vs. 765g, p<0.01). Longer period of parenteral nutrition and dexamethasone use was observed in MBD group. Cholestasis was associated with the highest likelihood of MBD (OR 16.6, 95% CI 4.8-56.9). Seizures (OR 5.2, 95% CI 1.3-20.5) and the prolonged use of diuretics (OR 2.6, 95% CI 1.0-7.0) also significantly increased the likelihood of MBD. Only cholestasis remained significant (OR 9.6, 95% CI 2.1-45.3) after multiple regression analysis.

CONCLUSION

Cholestasis is a significant risk factor for the development of MBD. Our future studies will be directed towards determining the causal relationship between cholestasis and MBD.

Vertebral cross-sectional area: an orphan phenotype with potential implications for female spinal health

A high priority in imaging-based research is the identification of the structural basis that confers greater risk for spinal disorders. New evidence indicates that factors related to sex influence the fetal development of the axial skeleton. Girls are born with smaller vertebral cross-sectional area compared to boys-a sexual dimorphism that is present throughout life and independent of body size. The smaller female vertebra is associated with greater flexibility of the spine that could represent the human adaptation to fetal load. It also likely contributes to the higher prevalence of spinal deformities, such as exaggerated lordosis and progressive scoliosis in adolescent girls when compared to boys, and to the greater susceptibility for spinal osteoporosis and vertebral fractures in elderly women than men.

Bone status in preterm infant: influences of different nutritional regimens and possible markers of bone disease

OBJECTIVE

The objective of this study was to evaluate possible influences of parenteral nutrition on growth and bone development in preterms and to search for markers of bone status.

STUDY DESIGN

Metacarpus bone transmission time (mc-BTT) was performed at birth, 21 days and 36 weeks of gestational age (GA) in preterms, receiving two different nutritional regimens, together with biochemical analysis.

RESULT

A total of 234 patients were studied. Newborns with aggressive nutrition had significantly better growth rate and higher values of mc-BTT until discharge. Mc-BTT at day 21 correlates positively with nutritional intakes and phosphatemia; lower limb length positively correlated with mc-BTT (P<0.01). Newborns with low energy intake in the first week of life (<70 kcal kg(-1) per day) and low serum phosphate level (<1.4 mmol l(-1)) at 21 days had lower mc-BTT at 36 weeks of GA (P<0.01).

CONCLUSION

Aggressive parenteral intakes in preterms improve growth and bone status in the short-medium term, suggesting that early nutrition could influence bone development.

Bone Mineral Content in Infants With Myelomeningocele, With and Without Treadmill Stepping Practice

PURPOSE

To study development of bone mineral content (BMC) in infants with myelomeningocele (MMC) who did or did not receive upright supported stepping practice (USSP) and in infants with typical development (TD).

METHODS

We tested 36 infants across the ages of 1 to 18 months. Dual-energy x-ray absorptiometry was used to collect raw BMC data for the whole body, legs, and arms, which were normalized using anthropometrics.

RESULTS

Whole-body BMC generally increased with age; values for infants with MMC were slightly lower than those for infants with TD. Bone mineral content for legs and arms was lower for infants with MMC than for infants with TD. Between MMC groups, the group receiving USSP showed increases in BMC with age.

CONCLUSION

Bone mineralization in infants with MMC begins to lag compared with infants with TD across infancy, and daily USSP can improve BMC as early as the first year of life.

Supplemented vs. unsupplemented human milk on bone mineralization in very low birth weight preterm infants: a randomized clinical trial

Very low birth weight preterm newborns weighing less than 1500 g were randomized to receive human milk supplemented with FM 85® or not. They have similar bone mineral content (BMC) at baseline, but, at the end of study, BMC was increasingly higher in the FM 85® group.

INTRODUCTION

The purpose of this study is to evaluate the effectiveness of a human milk supplement (FM 85®; Nestlé, Vevey, Switzerland) developed for the purpose of improving nutrition, including bone mineralization, in very low birth weight preterm newborns.

METHODS

Preterm infants weighing less than 1500 g at birth admitted to the neonatal intensive care unit of a university hospital were studied. During hospitalization, they were fed at least 50 % of human milk. Newborns with ≥20 days of age were randomly assigned to the intervention group (n = 19) to receive human milk supplemented with FM 85® or to a control group (n = 19) to receive human milk only. Anthropometric measurements, whole-body bone densitometry (DXA), and biochemical tests were performed at study entry and at the end of the study (shortly before discharge when the infant had reached 2000 g).

RESULTS

There were no start- or end-of-study differences between the two groups, except for daily increase in length (p = 0.010). At baseline, both groups had similar BMC: 5.49 ± 3.65 vs. 4.34 ± 2.98 g (p = 0.39) for the intervention and control group, respectively. However, at the end of the study, BMC was higher in the intervention group: 10.3 ± 4.71 vs. 6.19 ± 3.23 g (p = 0.003). The mean increase in BMC during the observation period was 4.90 ± 4.46 g for the intervention group and 1.86 ± 3.17 g for the control group (p = 0.020). Serum alkaline phosphatase levels were higher in the control group (720 ± 465 vs. 391 ± 177 IU/L; p = 0.007).

CONCLUSIONS

Our data suggest that supplementation of human milk with FM 85® leads to improved bone mineralization in very low birth weight preterm newborns.

Sexual Dimorphism in Newborn Vertebrae and Its Potential Implications

OBJECTIVE

To examine whether the sex-related differences in vertebral cross-sectional area (CSA) found in children and at the timing of peak bone mass-a major determinant of osteoporosis and future fracture risk-are also present at birth.

STUDY DESIGN

Vertebral CSA, vertebral height, and intervertebral disc height were measured using magnetic resonance imaging in 70 healthy full-term newborns (35 males and 35 females). The length and CSA of the humerus, musculature, and adiposity were measured as well.

RESULTS

Weight, body length, and head and waist circumferences did not differ significantly between males and females (P ≥ .06 for all). Compared with newborn boys, girls had significantly smaller mean vertebral cross-sectional dimensions (1.47 ± 0.11 vs 1.31 ± 0.12; P < .0001). Multiple linear regression analysis identified sex as a predictor of vertebral CSA independent of gestational age, birth weight, and body length. In contrast, the sexes were monomorphic with regard to vertebral height, intervertebral disc height, and spinal length (P ≥ .11 for all). There were also no sex differences in the length or cross-sectional dimensions of the humerus or in measures of musculature and adiposity (P ≥ .10 for all).

CONCLUSION

Factors related to sex influence fetal development of the axial skeleton. The smaller vertebral CSA in females is associated with greater flexibility of the spine, which could represent the human adaptation to fetal load. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities and increases the susceptibility to fragility fractures later in life.

Circulating sclerostin in children and young adults with heritable bone disorders

CONTEXT

Sclerostin is an inhibitor of bone formation and is an important determinant of bone mass. The role of sclerostin in heritable metabolic bone disorders has not been studied in detail.

OBJECTIVE

We evaluated serum sclerostin levels in patients with X-linked hypophosphatemic rickets (XLH) and osteogenesis imperfecta (OI) and analyzed the relationship of circulating sclerostin concentrations with lumbar spine areal bone mineral density (LS-aBMD).

SETTING

The study was conducted in the metabolic bone clinic of a pediatric orthopedic hospital.

PATIENTS

Participants were 128 individuals, including 30 patients with XLH, 76 patients with OI types I, III, and IV, and 22 healthy subjects.

MAIN OUTCOME MEASURES

Sclerostin was quantified in serum samples.

RESULTS

Patients with XLH had higher circulating sclerostin concentrations (mean [SD]: 30.2 [16.7] pmol/L) than healthy control subjects (21.4 [9.2] ng/mL) (P = .02), as well as relatively high LS-aBMD Z-scores (+1.1 [1.7]). In the XLH cohort, serum sclerostin levels were positively associated with the LS-aBMD Z-score (r = 0.56; P < .002) and with alkaline phosphatase (r = 0.45; P = .01). In patients with OI, sclerostin serum levels were similar to those of healthy control subjects despite low LS-aBMD.

CONCLUSIONS

The elevated sclerostin serum levels in XLH and the normal concentrations in OI suggest that the bone mass abnormalities in these disorders are not caused by primary sclerostin dysregulation.

Physical activity programs for promoting bone mineralization and growth in preterm infants

BACKGROUND

Lack of physical stimulation may contribute to metabolic bone disease of preterm infants, resulting in poor bone mineralization and growth. Physical activity programs combined with adequate nutrition might help to promote bone mineralization and growth.

OBJECTIVES

The primary objective was to assess whether physical activity programs in preterm infants improve bone mineralization and growth and reduce the risk of fracture.The secondary objectives included other potential benefits in terms of length of hospital stay, skeletal deformities and neurodevelopmental outcomes, and adverse events.Subgroup analysis:• Given that the smallest infants are most vulnerable for developing osteopenia (Bishop 1999), a subgroup analysis was planned for infants with birth weight < 1000 g.• Calcium and phosphorus intake may affect an infant's ability to increase bone mineral content (Kuschel 2004). Therefore, an additional subgroup analysis was planned for infants receiving different amounts of calcium and phosphorus, along with full enteral feeds as follows. ∘ Below 100 mg/60 mg calcium/phosphorus or equal to/above 100 mg/60 mg calcium/phosphorus per 100 mL milk. ∘ Supplementation of calcium without phosphorus. ∘ Supplementation of phosphorus without calcium.

SEARCH METHODS

The standard search strategy of the Cochrane Neonatal Review Group (CNRG) was used. The search included the Cochrane Central Register of Controlled Trials (CENTRAL) (2012, Issue 9), MEDLINE, EMBASE, CINAHL (1966 to March 2013), and cross-references, as well as handsearching of abstracts of the Society for Pediatric Research and the International Journal of Sports Medicine.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials comparing physical activity programs (extension and flexion, range-of-motion exercises) versus no organized physical activity programs in preterm infants.

DATA COLLECTION AND ANALYSIS

Data collection, study selection, and data analysis were performed according to the methods of the CNRG.

MAIN RESULTS

Eleven trials enrolling 324 preterm infants (gestational age 26 to 34 weeks) were included in this review. All were small (N = 16 to 50) single-center studies that evaluated daily physical activity for three and one-half to eight weeks during initial hospitalization. Methodological quality and reporting of included trials were variable.Four trials demonstrated moderate short-term benefits of physical activity for bone mineralization at completion of the physical activity program. The only trial assessing long-term effects on bone mineralization showed no effect of physical activity administered during initial hospitalization on bone mineralization at 12 months corrected age. Meta-analysis from four trials demonstrated a positive effect of physical activity on daily weight gain (weighted mean difference (WMD) 2.21 g/kg/d, 95% confidence interval (CI) 1.23 to 3.19). Data from four trials showed a positive effect on linear growth (WMD 0.12 cm/wk, 95% CI 0.01 to 0.24) but not on head growth (WMD -0.03 cm/wk, 95% CI -0.14 to 0.08) during the study period. Only one trial reported on fractures (this outcome did not occur in intervention and control groups) and complications of preterm birth (no significant differences between intervention and control groups). None of the trials assessed other outcomes relevant to this review.

AUTHORS' CONCLUSIONS

Some evidence suggests that physical activity programs might promote short-term weight gain and bone mineralization in preterm infants. Data are inadequate to allow assessment of harm or long-term effects. Current evidence does not support the routine use of physical activity programs in preterm infants. Further trials incorporating infants with a high baseline risk of osteopenia are required. These trials should address adverse events, long-term outcomes, and the effects of nutritional intake (calories, protein, calcium, phosphorus).

Bone densitometry in infants and young children: the 2013 ISCD Pediatric Official Positions

Infants and children <5 yr were not included in the 2007 International Society for Clinical Densitometry Official Positions regarding Skeletal Health Assessment of Children and Adolescents. To advance clinical care of very young children, the International Society for Clinical Densitometry 2013 Position Development Conference reviewed the literature addressing appropriate methods and skeletal sites for clinical dual-energy X-ray absorptiometry (DXA) measurements in infants and young children and how results should be reported. DXA whole-body bone mineral content and bone mineral density for children ≥3 yr and DXA lumbar spine measurements for infants and young children 0-5 yr were identified as feasible and reproducible. There was insufficient information regarding methodology, reproducibility, and reference data to recommended forearm and femur measurements at this time. Appropriate methods to account for growth delay when interpreting DXA results for children <5 yr are currently unknown. Reference data for children 0-5 yr at multiple skeletal sites are insufficient and are needed to enable interpretation of DXA measurements. Given the current scarcity of evidence in many areas, it is likely that these positions will change over time as new data become available.

Growth and bone mineralization in small-for-gestational-age preterm infants

BACKGROUND

Preterm infants are at risk for metabolic bone disease and suboptimal growth. This study examined the hypothesis that, apart from prematurity, intrauterine growth status (expressed as gestational age-specific birthweight standard deviation score) influences bone mineralization and body composition in early infancy.

METHODS

In this retrospective study, the groups consisted of preterm small-for-gestational-age (SGA) infants (n = 18; SGA group) and preterm appropriate-for-gestational-age (AGA) infants (n = 24; AGA group). Postnatal bone mineralization was measured at term-adjusted age (postmenstrual age, 37-42 weeks). Bone mineral content (BMC) and body composition were determined on dual-energy X-ray absorptiometry of the whole body.

RESULTS

BMC and lean mass were significantly lower in the SGA group than in the AGA group at term-adjusted age (37-42 weeks postmenstrual age). Stepwise regression analysis identified weight at examination as the most significant factor, accounting for 51% of the variance in BMC.

CONCLUSION

Bodyweight at term-adjusted age, rather than intrauterine growth, may affect postnatal bone mineralization in preterm low-birthweight infants. Therefore, promoting an increase in body size might increase postnatal bone mineralization in preterm SGA infants.

Skeletal clinical characteristics of osteogenesis imperfecta caused by haploinsufficiency mutations in COL1A1

COL1A1 haploinsufficiency mutations lead to the mildest form of osteogenesis imperfecta (OI), OI type I. The skeletal clinical characteristics resulting from such mutations have not been characterized in detail. In this study we assessed 86 patients (36 male, 50 female; mean age 13.3 years; range, 0.6 to 54 years) with COL1A1 haploinsufficiency mutations, of whom 70 were aged 21 years or less ("pediatric" patients). Birth history was positive for fracture or long-bone deformity in 12% of patients. The average rate of long-bone fracture (femur, tibia/fibula, humerus, radius/ulna) in pediatric patients was 0.62 fractures per year, one-half of which affected the tibia/fibula. Long-bone fracture rate was negatively associated with age and lumbar spine areal bone mineral density. Vertebral compression fractures were observed in 71% of the 58 pediatric patients who had lateral spine radiographs. The median number of vertebral fractures was higher for females (median 4; range, 0 to 14) than for males (median 1; range, 0 to 8) (p = 0.03). Lumbar spine areal bone mineral density was negatively associated with the severity of vertebral compression fractures, as reflected in the spine deformity index. Scoliosis was present in about 30% of pediatric patients but the Cobb angle was <30 degrees in all cases. The average final height Z-score was -1.1, representing a deficit of 8 to 10 cm compared to the general population. In summary, OI patients with COL1A1 haploinsufficiency mutations have high rates of significant skeletal involvement. Systematic follow-up of growing patients with COL1A1 haploinsufficiency mutations including radiographic screening for vertebral compression fractures and scoliosis is warranted.

Bone mineral content and density of the lumbar spine of infants and toddlers: influence of age, sex, race, growth, and human milk feeding

Little is known about factors that affect bone mass and density of infants and toddlers and the means to assess their bone health owing to challenges in studying this population. The objectives of this study were to describe age, sex, race, growth, and human milk feeding effects on bone mineral content (BMC) and areal density (aBMD) of the lumbar spine, and determine precision of BMC and aBMD measurements. We conducted a cross-sectional study of 307 healthy participants (63 black), ages 1 to 36 months. BMC and aBMD of the lumbar spine were measured by dual-energy X-ray absorptiometry. Duplicate scans were obtained on 76 participants for precision determination. Age-specific Z-scores for aBMD, weight, and length (BMDZ, WAZ, LAZ) were calculated. Information on human milk feeding duration was ascertained by questionnaire. Between ages 1 and 36 months, lumbar spine BMC increased about fivefold and aBMD increased twofold (p < 0.0001). BMC was greater (5.8%) in males than in females (p = 0.001), but there was no difference in aBMD (p = 0.37). There was no difference in BMC or aBMD between whites and blacks (p ≥ 0.16). WAZ and LAZ were positively associated with BMDZ (r = 0.34 and 0.24, p < 0.001). Duration of human milk feeding was negatively associated with BMDZ in infants <12 months of age (r = -0.42, p < 0.001). Precision of BMC and aBMD measurements was good, 2.20% and 1.84%, respectively. Dramatic increases in BMC and aBMD of the lumbar spine occur in the first 36 months of life. We provide age-specific values for aBMD of healthy infants and toddlers that can be used to evaluate bone deficits. Future studies are needed to identify the age when sex and race differences in aBMD occur, and how best to account for delayed or accelerated growth in the context of bone health assessment of infants and toddlers.

Serum 24,25-dihydroxyvitamin D concentrations in osteogenesis imperfecta: relationship to bone parameters

BACKGROUND

Several studies suggest that 24,25-dihydroxyvitamin D [24,25(OH)₂D] may have an effect on bone mass and metabolism.

OBJECTIVE

We evaluated the relationship between serum 24,25(OH)₂D levels and bone density and bone metabolism in children with a primary bone disorder-osteogenesis imperfecta (OI).

MATERIALS AND METHODS

The study included 132 patients (age, 1.1 to 17.9 yr; 67 girls) with OI types I, III, or IV who had not received bisphosphonate treatment at the time of analysis.

RESULTS

Serum 24,25(OH)₂D levels were significantly higher in OI type III than in OI type I or IV. Serum 24,25(OH)₂D concentrations were positively correlated with serum 25-hydroxyvitamin D (25OHD) levels and negatively correlated with serum PTH levels, and were not correlated with serum 1α,25-dihydroxyvitamin D [1,25(OH)₂D]. The ratio between serum 24,25(OH)₂D and 25OHD was negatively correlated with age and was independent of serum 25OHD concentrations. Regression analysis revealed that OI severity (P = 0.04), serum 25OHD levels (P < 0.001), and serum PTH concentrations (P = 0.045), but not age, gender, or serum 1,25(OH)₂D, were independent predictors of serum 24,25(OH)₂D levels. No correlation was found between serum 24,25(OH)₂D levels or the ratio between serum 24,25(OH)₂D and 25OHD and lumbar spine bone mineral density z-scores or bone marker levels (serum osteocalcin and urinary collagen type I N-telopeptide) after adjusting for OI type, age, and gender.

CONCLUSION

Patients with more severe OI type had higher 24,25(OH)₂D serum levels and higher serum 24,25(OH)₂D to 25OHD ratios, suggesting an increased 25OHD-24-hydroxylase activity.

Ultrasound for the assessment of bone quality in preterm and term infants

OBJECTIVE

As 80% of intrauterine bone mineralization takes place during the last trimester of pregnancy, preterm infants should be supplemented postnatally with optimal doses of calcium, phosphate and vitamin D. Calcium and phosphate excretion in the urine may be used to monitor individual mineral requirements, but are sometimes difficult to interpret. The objective of this study was to assess the value of quantitative ultrasound (QUS) for the analysis of bone status in neonates.

STUDY DESIGN

All admissions to three independent tertiary neonatal intensive care units were studied. In 172 preterm and term infants with a gestational age between 23 and 42 weeks (mean 33.8±5.0) and a birth weight from 405 to 5130 g (mean 2132±1091 g) bone status was evaluated prospectively by quantitative ultrasound velocity using a standardized protocol. Infants were followed in regular intervals up to their first discharge home. While measurements were conducted in weekly intervals initially (n=55), 2-week intervals were regarded as sufficient thereafter due to limited changes in QUS values within the shorter period. Infants with a birth weight below 1500 g were followed during outpatient visits until up to 17 months of age.

RESULT

The intra-individual day-to-day reproducibility was 0.62%. QUS-values from the first week of life correlated significantly with gestational age and birth weight (r=0.5 and r=0.6; P<0.001). Small-for-gestational-age infants showed lower values for QUS than appropriate-for-gestational-age infants allowing for their gestational age. Follow-up measurements correlated positively with age and weight during the week of measurement (r=0.2 and r=0.4; P=0.001). Comparing bone quality at 40 weeks of age in infants born at term versus infants born at 24 to 28 weeks, preterm infants showed significantly lower QUS than term infants (P<.0001).There was a significant correlation of QUS with serum alkaline phosphatase (P=0.003), the supplementation with calcium, phosphate and vitamin D (P< 0.001 each), as well as risk factors for a reduced bone mineralization. No correlation was found between QUS and calcium or phosphate concentration in serum or urine.

CONCLUSION

QUS is a highly reproducible, easily applicable and radiation-free technique that can be used to monitor bone quality in individual newborns. Further prospective randomized-trials are necessary to evaluate, if therapeutic interventions based on QUS are able to prevent osteopenia of prematurity.

Prematurity and related biochemical outcomes: study of bone mineralization and renal function parameters in preterm infants

Preterm is defined as a baby with a gestation of less than 37 completed weeks. In this study, serum calcium, phosphorus, ALP, creatinine, and electrolytes were measured in preterm babies. The present study comprised of 75 preterm babies of which 25 were of 28-30 weeks, 25 were of 30-32 weeks, and remaining 25 were of 34-36 weeks (controls) of gestational age. Serum calcium and phosphorus levels were found to be significantly decreased, and serum ALP, creatinine, and electrolytes were found to be significantly increased (P < 0.001) at 28-30 weeks as compared to controls, but serum calcium and phosphorous levels were found to be insignificantly decreased, whereas serum ALP activities were found to be insignificantly increased at 28-30 weeks as compared to 30-32 weeks of gestational age in preterm babies. It can be concluded that high serum ALP activity and low serum calcium and phosphorus levels are associated with preterm babies. A significant difference in the mean values of these renal function parameters was also obtained, except for serum sodium and potassium.

Severe osteogenesis imperfecta caused by a small in-frame deletion in CRTAP

Mutations of proteins involved in posttranslational modification of collagen type I can cause osteogenesis imperfecta (OI) inherited in a recessive pattern. The cartilage-associated protein (CRTAP) is part of a heterotrimeric complex (together with prolyl-3-hydroxylase-1 [P3H1] and cyclophilin B) that 3-hydroxylates the alpha 1 chain of collagen type I at proline residue 986 and plays a collagen chaperon role. CRTAP mutations usually cause severe OI. We report on a patient with OI and a homozygous in-frame deletion in CRTAP and a severe form of OI. The girl was born with markedly deformed long bones. Despite intravenous bisphosphonate treatment, she developed multiple vertebral compression fractures and severe scoliosis and at 4 years of age was able to sit only with support. Although CRTAP transcript levels were normal in the patient's fibroblasts, protein levels of both CRTAP and P3H1 were severely reduced. The degree of 3-hydroxylation at proline residue 986 was also decreased. This report characterizes a patient with a CRTAP small in-frame deletion. We are unaware of prior reports of this finding. We suggest that this deletion affects crucial amino acids that are important for the interaction and/or stabilization of CRTAP and P3H1.

Relationship between vitamin D status and bone mineralization, mass, and metabolism in children with osteogenesis imperfecta: histomorphometric study

The effect of low vitamin D levels in children with bone fragility disorders has not been examined in detail. In this study, we evaluated the relationship between vitamin D status and parameters of skeletal mineralization, mass, and metabolism in a group of pediatric osteogenesis imperfecta (OI) patients. This retrospective study consisted of 71 patients with a diagnosis of OI type I, III, or IV (ages 1.4 to 17.5 years; 36 girls) who had not received bisphosphonate treatment before iliac bone biopsy. Serum 25-hydroxyvitamin D [25(OH)D] levels ranged from 13 to 103 nmol/L and were less than 50 nmol/L in 37 patients (52%). None of the OI patients had radiologic signs of rickets or fulfilled the histomorphometric criteria for the diagnosis of osteomalacia (ie, elevated results for both osteoid thickness and mineralization lag time). Serum 25(OH)D levels were negatively correlated with age and serum parathyroid hormone levels but were not correlated with any parameter of bone mineralization (ie, osteoid thickness, mineralization lag time, or bone-formation rate per bone surface) or bone mass (ie, lumbar spine areal bone mineral density, iliac bone volume per tissue volume, or iliac cortical width). We found no evidence that serum 25(OH)D levels in the range from 13 to 103 nmol/L were associated with measures of bone mineralization, metabolism, or mass in children with OI.

Elevated Bone Turnover in an Infantile Patient with Mucolipidosis II; No Association with Hyperparathyroidism

This present report concerns an infantile patient with mucolipidosis II, who showed transient cortical bone hyperostosis followed by severe osteopenia. The diagnosis of mucolipidosis II was made based on the leakage of lysosomal enzymes in serum and conditioned media of the patient's skin fibroblasts, low activity of lysosomal enzymes of the fibroblasts and mutation of c.2086_2089insC (p.L697fs) and c.3565C>T (p.R1189X) in the GNPTAB gene. Bone X-ray analysis demonstrated a periosteal reaction and elevated bone resorption at the age of 2 mo. Bone markers, including alkaline phosphatase, osteocalcin and urine deoxypyridinoline, also indicated a high turnover of bone metabolism; however, no apparent rickets-like changes and no increased levels of PTH were observed. Elevated bone resorption is possibly associated with the leakage of lysosomal enzyme from osteoclasts into bone matrices. Bone formation gradually reduced, and increased bone resorption persisted. This led to severe osteopenia at the age of 6 mo. Characteristic bone findings may contribute to early diagnosis of mucolipidosis II, but their pathogenesis remains to be clarified.

Cranial base abnormalities in osteogenesis imperfecta: phenotypic and genotypic determinants

Cranial base abnormalities are an important complication of osteogenesis imperfecta (OI), a hereditary bone fragility disorder that in most patients is caused by mutations affecting collagen type I. To elucidate which clinical characteristics are associated with the occurrence of cranial base abnormalities in OI, we compared cephalometric results of 187 OI patients (median age 12.0 years, range 3.4 to 47 years; 96 female) with those of 191 healthy subjects and related findings to clinical descriptors of the disease. Overall, 41 patients (22%) had at least one unambiguously abnormal skull base measure. Multivariate logistic regression analysis in patients with OI types I, III, and IV (n = 169) revealed that height Z-score [odds ratio (OR) = 0.53, 95% confidence interval (CI) 0.43-0.66, p < .001]--but not age, gender, scleral hue, lumbar spine areal bone mineral density, or a history of bisphosphonate treatment--was a significant independent determinant of skull base abnormalities. Among patients with a height Z-score below -3, 48% had a skull base abnormality regardless of whether they had received bisphosphonate treatment in the first year of life or not. Genotype-phenotype correlations were evaluated in patients with detectable mutations in COL1A1 or COL1A2, the genes coding for collagen type I (n = 140). Skull base abnormalities were present in 6% of patients with haploinsufficiency (frameshift or nonsense) mutations, in 43% of patients with helical glycine substitutions caused by COL1A1 mutations, in 32% of patients with helical glycine substitutions owing to COL1A2 mutations, and in 17% of patients with splice-site mutations affecting either COL1A1 or COL1A2. However, multivariate logistic regression analysis showed that height Z-score but not the type of collagen type I mutation was independently associated with the prevalence of skull base abnormalities. In conclusion, this study shows that clinical severity of OI, as expressed by the height Z-score, was the strongest predictor of skull base abnormalities. We did not find evidence for the hypothesis that bisphosphonate treatment protects against skull base abnormalities.

Zoledronic acid for the treatment of osteopenia in pediatric Crohn's disease

BACKGROUND

Pediatric patients with Crohn's disease often have low bone mass (osteopenia) for age. No randomized, placebo-controlled trials using zoledronic acid have ever been performed in this population. The objective of this study was to assess the efficacy of zoledronic acid in children with Crohn's disease and osteopenia.

METHODS

A double-blind, randomized, placebo-controlled design was used. Thirteen adolescents received either a single intravenous dose of zoledronic acid (0.066 mg/kg, max 4 mg, n= 7) or saline placebo (n= 6). The primary outcome was change in lumbar spine bone mineral density (LSBMD) z-score at 6 months. Secondary outcomes included bone markers and adverse events.

RESULTS

At 6 months, the change in LSBMD z-score was significantly higher in the zoledronic acid group compared to placebo (0.7 vs 0.1, P < 0.001). Volumetrically adjusted LSBMD z-score also significantly increased in the treated group. This significant difference persisted until 12 months. With zoledronic acid, urinary C-telopeptide excretion decreased by 50% at 6 months and remained suppressed at 12 months (P= 0.02), but no changes were observed with placebo. Both groups had similar adverse events which included transient fever, arthralgias, and nausea (3/7 treated, 2/6 placebo, P= NS).

CONCLUSIONS

In this study, zoledronic acid demonstrated a significant increase in LSBMD at 6 and 12 months following a well-tolerated infusion.

Wormian bones in osteogenesis imperfecta: Correlation to clinical findings and genotype

The presence of a larger than usual number of Wormian bones (accessory skull bones completely surrounded by a suture line) is a well-known radiographic sign of osteogenesis imperfecta (OI), but the phenotypic and genotypic correlates are not well characterized. In the present study we retrospectively analyzed skull radiographs of 195 OI patients (median age 11.8 years, range 0.4-48 years; 100 female). A significant number of Wormian bones (SNWB, defined as the presence of 10 or more Wormian bones) were found in at least one patient in all of the OI types studied (I, III to VII). SNWB were observed in 35% of patients with OI type I, in 96% of patients with OI type III and 78% of patients with OI type IV. SNWB were present in 28% of patients with haploinsufficiency (nonsense and frameshift) mutations in COL1A1, in 96% of patients with helical glycine substitutions in the alpha 1 chain of collagen type I and in 72% of patients with helical glycine substitutions in the alpha 2 chain of collagen type I. Stepwise multivariate logistic regression analysis showed that height z-score, an indicator of disease severity, was inversely related with the prevalence of SNWB. SNWB were visible in 19 of the 26 patients who had skull radiographs in the first year of life, including a 2-week-old newborn. Thus, it appears that SNWB occur more frequently in more severely affected OI patients and seem to develop mostly in utero.

Intravenous pamidronate in osteogenesis imperfecta type VII

Cyclical intravenous treatment with pamidronate is widely used to treat osteogenesis imperfecta (OI) types I, III, and IV, which are due to dominant mutations affecting collagen type I alpha chains. There is no information about the effects of pamidronate in children with OI type VII, an autosomal-recessive form of OI caused by a mutation in the cartilage-associated protein gene. In this retrospective single-center study, we compared the effects of pamidronate in four girls with OI type VII (age range 3.9-12.7 years) to those in eight girls with OI types caused by collagen type I mutations who were matched for age and disease severity. During 3 years of pamidronate therapy, lumbar spine areal bone mineral density increased and lumbar vertebral bodies improved in shape in patients with OI type VII. Other outcomes such as fracture rates and mobility scores did not show statistically significant changes in this small study cohort. There were no significant side effects noted during the time of follow-up. Thus, intravenous treatment with pamidronate seems to be safe and of some benefit in patients with OI type VII.

Quantitative micro-computed tomography: a non-invasive method to assess equivalent bone mineral density

One of the many applications of micro computed tomography (microCT) is to accurately visualize and quantify cancellous bone microstructure. However, microCT based assessment of bone mineral density has yet to be thoroughly investigated. Specifically, the effects of varying imaging parameters, such as tube voltage (kVp), current (microA), integration time (ms), object to X-ray source distance (mm), projection number, detector array size and imaging media (surrounding the specimen), on the relationship between equivalent tissue density (rhoEQ) and its linear attenuation coefficient (micro) have received little attention. In this study, in house manufactured, hydrogen dipotassium phosphate liquid calibration phantoms (K2HPO4) were employed in addition to a resin embedded hydroxyapatite solid calibration phantoms supplied by Scanco Medical AG Company. Variations in current, integration time and projection number had no effect on the conversion relationship between micro and rhoEQ for the K2HPO4 and Scanco calibration phantoms [p>0.05 for all cases]. However, as expected, variations in scanning tube voltage, object to X-ray source distance, detector array size and imaging media (referring to the solution that surrounds the specimen in the imaging vial) significantly affected the conversion relationship between mu and rhoEQ for K2HPO4 and Scanco calibration phantoms [p<0.05 for all cases]. A multivariate linear regression approach was used to estimate rhoEQ based on attenuation coefficient, tube voltage, object to X-ray source distance, detector array size and imaging media for K2HPO4 liquid calibration phantoms, explaining 90% of the variation in rhoEQ. Furthermore, equivalent density values of bovine cortical bone (converted from attenuation coefficient to equivalent density using the K2HPO4 liquid calibration phantoms) samples highly correlated [R2=0.92] with the ash densities of the samples. In conclusion, Scanco calibration phantoms can be used to assess equivalent bone mineral density; however, they cannot be scanned with a specimen or submerged in a different imaging media. The K2HPO4 liquid calibration phantoms provide a cost effective, easy to prepare and convenient means to perform quantitative microCT analysis using any microCT system, with the ability to choose different imaging media according to study needs. However, as with any liquid calibration phantom, they are susceptible to degradation over time.

Successful results of pamidronate treatment in children with osteogenesis imperfecta with emphasis on the interpretation of bone mineral density for local standards

AIM

To assess the long-term effect of pamidronate therapy on bone mineral metabolism and bone mineral density (BMD) in children with osteogenesis imperfecta (OI) and to evaluate BMD results with respect to national standards.

METHODS

Pamidronate was administered intravenously on 3 consecutive days every 3 to 4 months at a dose of 1 mg/kg/d in 35 patients. Infusion cycles ranged from 4 to 17. Serum calcium, phosphorus, bone turnover markers, L1-L4 areal BMD (aBMD), and fracture rate were evaluated. Areal BMD Z scores were compared with national sex-specific reference data and volumetric BMD Z scores.

RESULTS

In all children, linear growth continued along the same percentile during treatment. All parameters of bone turnover showed a decrease. L1 to L4 aBMD and Z score increased markedly, and fracture rate decreased in all patients during therapy. The mean annual percent gain in aBMD was highest in the first year and slowed down in subsequent years. Mean L1 to L4 aBMD Z scores according to Turkish reference data were higher than that of manufacturer values (P = 0.004). Correction of L1 to L4 vertebrae for bone size yielded to a decrease in osteoporosis in OI patients (41.5% vs 22.3%).

CONCLUSIONS

Bone mineral density increased and fracture rate decreased in children and infants with OI during pamidronate treatment. Prevalence of osteoporosis decreased after correction for national standard and volumetric BMD. Use of an appropriate reference database and method of data analysis are very important for correct evaluation of osteoporosis.

Pediatric dual-energy X-ray absorptiometry: technique, interpretation, and clinical applications

This article reviews the dual-energy x-ray absorptiometry (DXA) technique, its interpretation, and clinical applications with emphasis on the considerations unique to pediatrics. Specifically, the use of DXA in children requires the radiologist to be a "clinical pathologist," monitoring the technical aspects of the DXA acquisition, a "statistician" knowledgeable in the concepts of Z-scores and least significant changes, and a "bone specialist," aware of the DXA findings in a large number of clinical diseases, providing the referring clinician with a meaningful context for the numeric result obtained with DXA.

Physical activity programs for promoting bone mineralization and growth in preterm infants

BACKGROUND

Lack of physical stimulation may contribute to metabolic bone disease of preterm infants resulting in poor bone mineralization and growth. Physical activity programs in the presence of adequate nutrition might help to promote bone mineralization and growth.

OBJECTIVES

The primary objective of this review was to assess whether physical activity programs in preterm infants improve bone mineralization and growth and reduce the risk of fractures.

SEARCH STRATEGY

Following the standard search strategy of the Cochrane Neonatal Review Group, a search was conducted in September 2006 including PubMed, EMBASE, CINAHL, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2006), cross-references and handsearching of abstracts of the Society for Pediatric Research and the International Journal of Sports Medicine. No language restrictions were applied.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials comparing physical activity programs (extension and flexion, range-of-motion exercises for several minutes a day several days per week for at least two weeks) to no organized physical activity programs in preterm infants. Eligible studies included those that provided physical activity for the experimental group, with or without massage and/or tactile stimulation for both experimental and control groups, as well as information on at least one outcome of interest.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed searches and extracted data. All three review authors were involved in selection and assessment of quality of studies. The statistical methods included relative risk (RR), risk difference (RD) and number needed to treat (NNT) for dichotomous outcomes and weighted mean difference (WMD) for continuous outcomes, reported with 95% confidence intervals (CI). Heterogeneity was estimated by the I(2) statistic. A fixed effect model was used to pool data for meta-analyses.

MAIN RESULTS

Six trials enrolling 169 preterm infants (gestational age 26 to 34 weeks) were included in this review. All were small (N = 20 - 49) single center studies evaluating daily physical activity for 3.5 to 4 weeks during initial hospitalization. The methodological quality and reporting of all trials was poor. None of them stated the methods of concealment of patient allocation, the method of randomization or attempted blinding of the intervention. Only two trials attempted blinding of outcome assessors for outcomes relevant to this review. Two trials (N = 55) demonstrated moderate short-term benefits of physical activity on bone mineralization at completion of the physical activity program. Data was not pooled for meta-analyses due to methodological differences. The only trial (N = 20) assessing long-term effects on bone mineralization showed no effect of physical activity administered during initial hospitalization on bone mineralization at 12 months corrected age. Meta-analysis from three trials (N = 78) demonstrated an effect of physical activity on daily weight gain (WMD 2.77 g/kg/d, 95% CI 1.62, 3.92). Data from two trials (N = 58) showed no effect on linear growth (WMD -0.04 cm/week, 95% CI -0.19, 0.11) or head growth (WMD -0.03 cm/week, 95% CI -0.14, 0.09) during the study period. The I(2) statistic suggested heterogeneity on the analysis of linear growth (p = 0.006, I(2) = 86.9%). None of the trials assessed fractures or other outcomes relevant to this review. Data was insufficient for subgroup analyses based on birth weight and calcium/phosphorus intake.

AUTHORS' CONCLUSIONS

There is weak evidence from six small randomized trials of poor methodological and reporting quality that physical activity programs might promote moderate short-term weight gain and bone mineralization in preterm infants. The clinical importance of these findings is questionable given the small effect size and low baseline risk of poor bone mineralization and growth in study participants. Data is inadequate to assess harm or long term effects. Current evidence does not justify the standard use of physical activity programs in preterm infants. Further evaluation of this intervention in well designed trials incorporating extremely low birth weight infants who are at high risk of osteopenia is required. Future trials should report on adverse events and long term outcomes including fractures, growth, bone mineralization, skeletal deformities and neurodevelopmental impairment. These trials should address the possibility that nutritional intake (calories, protein, calcium, phosphorus) might modify the effects of physical activity.

Osteogenesis imperfecta type VI in childhood and adolescence: effects of cyclical intravenous pamidronate treatment

Cyclical intravenous treatment with pamidronate is of clinical benefit in children with moderate to severe osteogenesis imperfecta (OI) types I, III and IV, but there is no information on the effects of this treatment on the newly described OI type VI. Here, we report on the results of 3 years of pamidronate treatment in 10 children and adolescents with OI type VI (age range 0.8 to 14.5 years, three girls). Treatment effects were compared to those of 10 patients with OI types I, III, and IV, who were matched for age and disease severity (based on height and lumbar spine areal bone mineral density). During pamidronate therapy, lumbar spine areal bone mineral density z scores increased and lumbar spine vertebral bodies improved in shape. Iliac bone histomorphometry showed a tendency to higher cortical thickness (+53%, P=0.06) but the mineralization defect, a characteristic feature of OI type VI, did not change during pamidronate treatment. Annualized fracture incidence decreased from 3.1 per year before treatment to 1.4 fractures per year during treatment (P<0.05). Regarding mobility, the Pediatric Evaluation of Disability Inventory gross motor score increased by 42% during pamidronate treatment (P<0.005). Significant improvements were also found for age-related z scores of maximal isometric grip force. In comparison to the OI control group, the fracture incidence was higher and the gross motor scores were lower in OI type VI, both before and after pamidronate treatment (P<0.05 for each parameter). No differences were found between the groups for changes in densitometric measures and cortical thickness during pamidronate treatment. Our results suggest that 3 years of intravenous pamidronate therapy led to improvements in bone mineral mass, gross motor function, muscle force and fracture incidence in patients with OI type VI. However, the gains in mobility scores and reductions in fracture incidence during pamidronate treatment are less than in other OI types.

Pediatric DXA: technique and interpretation

This article reviews dual X-ray absorptiometry (DXA) technique and interpretation with emphasis on the considerations unique to pediatrics. Specifically, the use of DXA in children requires the radiologist to be a "clinical pathologist" monitoring the technical aspects of the DXA acquisition, a "statistician" knowledgeable in the concepts of Z-scores and least significant changes, and a "bone specialist" providing the referring clinician a meaningful context for the numeric result generated by DXA. The patient factors that most significantly influence bone mineral density are discussed and are reviewed with respect to available normative databases. The effects the growing skeleton has on the DXA result are also presented. Most important, the need for the radiologist to be actively involved in the technical and interpretive aspects of DXA is stressed. Finally, the diagnosis of osteoporosis should not be made on DXA results alone but should take into account other patient factors.

Vertebral morphometry in children and adolescents with osteogenesis imperfecta: effect of intravenous pamidronate treatment

Results in small patient series suggest that cyclical intravenous treatment with pamidronate can lead to reshaping of compressed vertebral bodies in children and adolescents with osteogenesis imperfecta (OI), but more detailed analyses are lacking. In this study of patients with moderate to severe OI (age range 0.1 to 16.7 years), we used vertebral morphometry to longitudinally assess changes in lumbar vertebral shape before (n = 17 patients) and during 2 to 4 years of pamidronate treatment (n = 72 patients). Anterior, posterior and midpoint vertebral heights of lumbar vertebrae L1 to L4 were determined on lateral lumbar spine X-rays and were related to vertebral body length in the antero-posterior direction. Before pamidronate treatment, vertebral body height ratios did not change significantly, but the mean concavity index (defined as the ratio between midpoint and posterior vertebral body heights) decreased by 22% (P = 0.002). Pamidronate treatment was associated with an increase in vertebral height ratio at each of the 12 sites that were analyzed. Consequently, patients who had received pamidronate for an average of 3 years had less compressed vertebrae than a historical control group of patients who had the same OI type, age and sex but who had not received pamidronate. Multiple regression analysis revealed that age was negatively and lumbar spine areal bone mineral density z score was positively associated with vertebral shape at baseline. The main determinant of treatment response was the severity of vertebral deformities at baseline. These results suggest that vertebral deformations worsen in patients with moderate to severe OI who do not receive medical treatment and that pamidronate helps to reverse this trend. In moderate to severe forms of OI, pamidronate should be started as early as possible to treat or to prevent vertebral deformations.

Effect of intravenous pamidronate therapy on functional abilities and level of ambulation in children with osteogenesis imperfecta

OBJECTIVE

To evaluate the functional abilities and the level of ambulation during pamidronate therapy in children with moderate to severe osteogenesis imperfecta.

STUDY DESIGN

Functional abilities, ambulation, and grip force were assessed in 59 patients (mean age, 6.1 years; range, 0.5-15.7 years; 30 girls) during 3 years of pamidronate treatment. Functional skills (mobility and self-care) were both assessed by using the Pediatric Evaluation of Disability Inventory. Ambulation level was assessed by using the modified Bleck score. For 48 patients, results after 3 years of pamidronate treatment could be matched to those of patients with similar age and disease severity who had not received pamidronate.

RESULTS

Mobility and self-care scores increased during the study period (+43% and +30%, respectively). The average ambulation score changed from 0.8 to 1.9. Maximal isometric grip force increased by 63%. Mobility and ambulation scores and grip force measures were significantly higher than in patients who had not received pamidronate. The difference in self-care scores did not reach significance.

CONCLUSION

This study suggests that cyclical pamidronate treatment improves mobility, ambulation level, and muscle force in children with moderate to severe osteogenesis imperfecta.

Cyclical intravenous pamidronate treatment affects metaphyseal modeling in growing patients with osteogenesis imperfecta

This analysis of 50 growing patients with osteogenesis imperfecta revealed that 2-4 years of pamidronate treatment lead to abnormalities in the shape of the distal femoral metaphyses.

INTRODUCTION

Cyclical intravenous pamidronate therapy is of clinical benefit in children and adolescents with moderate to severe osteogenesis imperfecta (OI) but might interfere with the shaping of long bone metaphyses during growth.

MATERIALS AND METHODS

We evaluated the distal femur in 50 growing children with moderate to severe OI (mean age, 6.7 +/- 3.4 years; 26 girls) who had received 2-4 years of pamidronate therapy (annual dose, 9 mg/kg body weight). The mediolateral width of the distal femoral growth plate and of the metaphysis, as well as the ratio between these two measures (called metaphyseal index), were determined on lower limb radiographs.

RESULTS

Compared with untreated OI patients who were matched for OI type and age, pamidronate-treated patients had similar growth plate width but wider metaphyses, resulting in a 26% higher metaphyseal index (p < 0.001). Apart from the effect on bone shape, each pamidronate cycle induces a transverse line in metaphyses that are adjacent to active growth plates. Analyses of these transverse lines revealed that they persist for an average time of approximately 4 years, with a range from 2 to 8 years.

CONCLUSIONS

Pamidronate interferes with the process of periosteal resorption that is normally responsible for shaping the distal femoral metaphysis. Pamidronate-induced transverse lines disappear with time, supporting the view that these lines represent horizontal trabeculae that undergo remodeling. There is no evidence at present that these treatment induced morphological changes have any clinical implications.

The effect of cyclical intravenous pamidronate in children and adolescents with osteogenesis imperfecta type V

Intravenous treatment with pamidronate is beneficial in children and adolescents with moderate to severe forms of osteogenesis imperfecta (OI) types I, III and IV, but there is little information on the effects of this treatment on the newly described OI type V. Here, we describe the results of 2 years of pamidronate treatment in 11 children and adolescents with OI type V (age at start of therapy 1.8 to 15.0 years; 6 girls). Pamidronate was given in intravenous cycles at a cumulative yearly dose of 9 mg/kg. The first infusion cycle was associated with fever and mild hypocalcemia in most patients, but no other short-term side effects were noted. Two years of pamidronate treatment led to a decrease in the urinary excretion of N-terminal telopeptide of type I collagen to 50% of baseline levels. Both the size and volumetric bone mineral density of lumbar vertebrae increased compared to age- and sex-matched reference data (P < 0.05 in both cases). Histomorphometry of transiliac bone samples showed an average increase of 86% in cortical thickness (N = 7; P = 0.005). No significant changes with treatment were observed in the age-related z scores of isometric maximal grip force and height. Fracture incidence decreased from 1.5 fractures per year before treatment to 0.5 fractures per year during the fist 2 years of treatment. Ambulation status improved in four patients and remained unchanged in the others. In conclusion, the intravenous pamidronate therapy has a similar effect in OI type V as it has in the other OI types.

Maternal and cord blood long-chain polyunsaturated fatty acids are predictive of bone mass at birth in healthy term-born infants

Long-chain polyunsaturated fatty acids (LC PUFA) are associated with bone mass in animals and human adults, yet no data exist for human infants. Thus, the objective of this study was to establish that LC PUFA status is associated with bone mass in healthy infants. Thirty mother-infant pairs were studied for LC PUFA status by measuring maternal and cord blood red blood cells (RBC) for arachidonic acid (AA), eicosapentaenoic acid (EPA), and DHA. Infant anthropometry and lumbar spine 1-4, femur and whole-body bone mineral content (BMC) were measured within 15 d of delivery. Maternal and infant LC PUFA were tested for their relationship to BMC using Pearson correlation and backward step-wise regression analyses. At birth, the average gestational age was 39.3+/-1.1 wk and body weight was 3433+/-430 g. Cord RBC AA was positively correlated with whole-body BMC, AA:EPA positively correlated with lumbar spine 1-4 BMC and femur BMC. Maternal RBC AA was positively correlated with whole-body BMC. After accounting for infant weight using regression, whole-body BMC was positively predicted by cord RBC AA but none of the maternal LC PUFA; lumbar spine 1-4 BMC was positively predicted by cord RBCAA:EPA ratio but negatively by maternal DHA; and femur BMC was not predicted by cord LC PUFA but was negatively predicted by maternal DHA. Imbalances among the n-6 and n-3 LC PUFA by term gestation are associated with lower bone mass, suggesting that the maternal diet should be balanced in n-6 and n-3 LC PUFA.

Effects of intravenous pamidronate treatment in infants with osteogenesis imperfecta: clinical and histomorphometric outcome

Clinical and histomorphometric outcome was compared between children with OI who had received pamidronate since infancy and age-matched patients who had never received pamidronate. Pamidronate was associated with improved vertebral shape and mass, higher cortical width, increased cancellous bone volume, and suppressed bone turnover.

INTRODUCTION

Observations in small patient series indicate that infants with severe osteogenesis imperfecta (OI) benefit from treatment with cyclical intravenous pamidronate. However, detailed analyses of outcome are lacking for this age group.

MATERIALS AND METHODS

Clinical outcome was evaluated in 29 children with OI types I (n = 3), III (n = 14), or IV (n = 12) who started pamidronate therapy before 2 years of age (age at treatment onset: median, 6 months; range, 2 weeks to 23 months) and who had completed 3 years of treatment (total annual pamidronate dose, 9 mg/kg). They were compared with a historical control group of 29 untreated children with severe OI who were matched for OI type and age at the 3-year treatment time-point. In addition, iliac bone histomorphometry was compared between 24 pamidronate-treated patients and 24 age-matched OI patients who had not received pamidronate.

RESULTS

Morphometric evaluation of lumbar vertebrae (L(1)-L(4)) showed that the shape of vertebral bodies was better preserved in pamidronate-treated patients. This was accompanied by significantly higher lumbar spine areal and volumetric BMD (+110 and +96%, respectively) and a larger vertebral bone volume (+26%) on densitometry. Regarding mobility function, the Pediatric Evaluation of Disability Inventory gross motor score was 50% greater in the pamidronate group (p < 0.001). Iliac bone histomorphometry showed 61% higher cortical width and 89% higher cancellous bone volume in pamidronate-treated patients. Bone formation rate per bone surface in the pamidronate group was only 17% that of untreated patients.

CONCLUSIONS

In conclusion, this study suggests that cyclical pamidronate treatment started in infancy leads to improved bone strength and better gross motor function but also suppresses bone turnover markedly. It is therefore prudent to reserve pamidronate treatment to infant OI patients who present with a moderate to severe phenotype.

Bone mineralization and growth are enhanced in preterm infants fed an isocaloric, nutrient-enriched preterm formula through term

BACKGROUND

Because recent data on the effects of mineral concentrations in preterm infant formula on bone mineralization are lacking, recommendations for the mineral content of preterm infant formula differ greatly between committees.

OBJECTIVE

The goal of the study was to assess the effects of an isocaloric, nutrient-enriched preterm formula, which was fed from the age when full enteral feedings were tolerated through expected term, on bone mineralization in preterm infants.

DESIGN

We conducted a prospective, randomized, double-blind study in healthy, preterm infants (gestational age of 28-32 wk) who were fed either a control preterm formula (n=20) or an isocaloric, nutrient-enriched preterm formula (n=21) until 3 mo of age (ie, approximate expected term). Serum calcium indexes were taken throughout the study, and bone mass was determined by using dual-energy X-ray absorptiometry at hospital discharge and expected term.

RESULTS

A total of 37 infants (experimental formula, n=19; control formula, n=18) completed the study. Compared with control subjects, infants fed the experimental formula had 25% and 40% higher intakes of calcium and phosphorus, respectively. Serum calcium, phosphorus, osteocalcin, and alkaline phosphatase concentrations and urinary collagen type I cross-linked N-telopetide concentrations were not significantly different between the groups at any time point. The bone mineral content of infants fed the experimental formula was 23% (P=0.039) and 35% (P=0.002) higher at hospital discharge and expected term, respectively.

CONCLUSIONS

Bone mineralization at hospital discharge and expected term was significantly higher in preterm infants fed the isocaloric, nutrient-enriched formula than in those fed control formula. Continuation of the experimental formula beyond hospital discharge, through expected term, further improved bone mineralization.

Three children with lower limb fractures and a mineralization defect: a novel bone fragility disorder?

In this report, we describe three unrelated children with an apparently novel bone fragility disorder that is associated with an idiopathic mineralization defect. Recurrent lower limb fractures started with weight bearing. The patients had none of the phenotypic, radiological, or histomorphometric features classically associated with known bone fragility disorders such as osteogenesis imperfecta (OI), idiopathic juvenile osteoporosis (IJO), or mild autosomal dominant osteopetrosis. Radiologically, there was increased metaphyseal trabeculation, normal to increased cortical thickness, and no evidence of rickets or osteomalacia. Areal and volumetric bone mineral density (BMD) of the lumbar spine did not show any major alteration. Peripheral quantitative computed tomography of the radius showed elevated cortical thickness and total and trabecular volumetric bone mineral density in one patient. Qualitative histology of iliac bone biopsy specimens showed a paucity of the birefringent pattern of normal lamellar bone. Quantitative histomorphometric analysis demonstrated osteomalacia with a prolonged mineralization lag time in the presence of a decreased mineral apposition rate. There was no biochemical evidence of abnormal calcium or phosphate metabolism. Type I collagen mutation analysis was negative. We conclude that this is a bone fragility disorder of moderate severity that tends to cause fractures in the lower extremities and is associated with the accumulation of osteoid due to an intrinsic mineralization defect. The pathogenetic basis for this disorder remains to be elucidated.

Maternal and fetal outcome after long-term pamidronate treatment before conception: a report of two cases

The pregnancies of two women with osteogenesis imperfecta who received intravenous pamidronate before conception are reported. The mothers suffered no ill effects. One baby had transient asymptomatic hypocalcemia and one had bilateral talipes equinovarus. This report documents the pregnancy outcomes of two women with osteogenesis imperfecta (OI), types I and IV, who received intravenous pamidronate as part of an observational trial before conception. Pamidronate was not administered after conception. Other than hyperemesis in one woman, the pregnancies and deliveries were uneventful. Both babies inherited OI from their mothers. The baby with OI type IV also had bilateral talipes equinovarus. Biochemical evaluation of the mothers and babies at 24 h and/or 2 weeks postpartum was normal, apart from one baby with asymptomatic hypocalcemia at 24 h of age that had resolved when next measured on day 11 of life. No biochemistry was available on the second child until 13 days of age. Neither baby had skeletal modeling abnormalities consistent with in utero pamidronate exposure. The lumbar spine (L1-L4) areal BMD and anterior to posterior height ratios of lumbar vertebral bodies of both women remained constant during pregnancy. Both the mothers and babies remain well and free of fracture 14 and 16 months postpartum.

Pre- and post-discharge feeding of very preterm infants: impact on growth and bone mineralization

In this prospective study we examined (1) how the nutritional status of very preterm infants, judged by growth measures and biochemical values, evolved during the initial hospitalization; (2) the effect of feeding on growth after discharge from hospital; and (3) the risk factors associated with low lumbar bone mineral content (BMC) later in infancy. Sixty-four former preterm infants had their lumbar spine (L2-L4) BMC assessed by dual energy X-ray absorptiometry when they weighed between 5 and 7 kg. Predicted BMC values were calculated based on our previously reported reference lumbar BMC data. These values were used to convert the preterm infants' BMC values into percentages. The extremely preterm group (gestational age < or =28 weeks) had significantly more respiratory morbidity and longer duration of hospital stay than the more mature infants. Both groups developed growth retardation and malnutrition during the hospital stay. Exclusive breastfeeding after discharge from hospital supported linear catch-up growth and weight gain but was associated with a 7.0 (1.2-41.7)-fold risk of having low BMC values. The other factors associated with the risk of having low BMC values later in infancy were low serum phosphate levels at 6 weeks, with a 7.8 (1.6-37.0)-fold risk, and male gender, with a 4.3 (1.2-16.1)-fold risk. Appropriately designed interventional studies are needed to improve the growth and nutrition of these infants during initial hospitalization. In order to improve the postdischarge nutrition, we suggest that the amount and duration of multicomponent human milk fortification should be studied further to provide individualized nutrition throughout the catch-up growth period until the end of the first year of life.

Bone mass, size, and density in children and adolescents with osteogenesis imperfecta: effect of intravenous pamidronate therapy

Cyclical intravenous therapy with pamidronate improves the clinical course in children and adolescents with osteogenesis imperfecta (OI). In this study, we evaluated the effect of this therapy on lumbar spine bone mass (bone mineral content [BMC]), size (bone volume [BV]), and density (volumetric bone mineral density [vBMD]). Results from 56 patients (age, 0.2-15.9 years; 25 girls) on long-term pamidronate treatment were compared with those of 167 patients who had not received pamidronate before densitometry. In all patients who received pamidronate, BMC, BV, and vBMD increased above levels expected for untreated patients (p < 0.001 in each case). After 4 years of treatment, BMC, BV, and vBMD were 154%, 44%, and 65% higher, respectively, in treated than in untreated patients who were matched for age and OI type. A multiple regression model showed that baseline BMC was negatively associated with the increase in BMC. In conclusion, the bone mass increase in pediatric OI patients receiving pamidronate is caused by increases in both bone size and density. Patients with larger deficits in bone mass at baseline have a more marked bone mass gain during therapy.