Longitudinal Bone Mineralization Assessment in Children Treated With Long-Term Parenteral Nutrition for Severe Intestinal Failure.

BACKGROUND: Metabolic bone disease is common in children receiving home parenteral nutrition (HPN) for intestinal failure (IF). Long-term evolution of bone mass in pediatric IF is poorly documented. The aims of this study were (1) to determine the prevalence of low bone mass (LBM) in children receiving HPN for IF, (2) to evaluate the evolution of total bone mineral content (TBMC) during HPN with dual-energy x-ray absorptiometry (DXA), and (3) to identify related factors. METHODS: All children referred in our HPN center from 2004 to 2014 were eligible. Inclusion criteria were HPN dependence due to noninflammatory IF, at least 2 TBMC assessments, and HPN duration of at least 2 years at last DXA. TBMC was expressed in z score for ideal weight for height (WFH). LBM was defined by a TBMC WFH z score ≤-2 standard deviations (SD). RESULTS: A total of 175 DXAs for 31 children were performed, mean of 5.6 ± 2.9 assessments per child. The median time between first and last DXA recorded was 6.2 years (0.7-16.6). At the first DXA, 14 children (45%) had a LBM. TBMC increased by +0.1 ± 0.04 SD per year of HPN (P = .012). The risk of LBM decreased with an odds ratio of 0.9 per year of HPN (95% confidence interval, 0.92-0.99; P = .018). Lean mass z score and calcium parenteral intakes were related to the TBMC improvement. CONCLUSION: LBM is common in pediatric IF, but bone status could improve during HPN in these children.

Influence of a two-year steroid treatment on body composition as measured by dual X-ray absorptiometry in boys with Duchenne muscular dystrophy.

Steroids are nowadays routinely used as a long-term treatment in Duchenne muscular dystrophy (DMD). Their effects on body composition were assessed using dual X-ray absorptiometry. The study followed over 2 years 29 genetically confirmed DMD patients: 21 in the steroid-treated group and 8 in the steroid-naïve group. After 2 years of steroid treatment, the lean tissue mass values increased significantly (p<0.0001), the percentage of body fat mass remained practically constant (p=0.94) in comparison with the initial visit. In the steroid-naïve patients, there were no significant increases in the lean tissue mass but deterioration in body composition confirmed by a significant increase in the percentage of body fat mass. Besides, significant negative correlations were found between the percentage of body fat mass and the MFM total score (R=-0.79, n=76, p<0.0001). A 2-year steroid treatment improves significantly body composition of boys with DMD through a significant increase in lean tissue mass. We suggest that a thorough check of body composition should be carried out before steroid treatment discontinuation in case of overweight gain.

The Official Positions of the International Society for Clinical Densitometry: acquisition of dual-energy X-ray absorptiometry body composition and considerations regarding analysis and repeatability of measures.

In preparation for the International Society for Clinical Densitometry Position Development Conference of 2013 in Tampa, Florida, Task Force 2 was created as 1 of 3 task forces in the area of body composition assessment by dual-energy X-ray absorptiometry (DXA). The assignment was to review the literature, summarize the relevant findings, and formulate positions covering (1) accuracy and precision assessment, (2) acquisition of DXA body composition measures in patients, and (3) considerations regarding analysis and repeatability of measures. There were 6 primary questions proposed to the task force by the International Society for Clinical Densitometry board and expert panel. Based on a series of systematic reviews, 14 new positions were developed, which are intended to augment and define good clinical practice in quantitative assessment of body composition by DXA.

Bone mineral and body composition alterations in paediatric cystic fibrosis patients.

BACKGROUND: With the increased life span of cystic fibrosis (CF) patients, CF-related bone diseases could have an increased prevalence and morbidity in this group. In children, previous retrospective and prospective studies have yielded conflicting results on bone mineralization. OBJECTIVE: To monitor body composition and bone mineral status of children with CF. MATERIALS AND METHODS: We reviewed the dual-energy X-ray absorptiometry (DXA) data of 161 children with CF (age 10 +/- 4.8 years). Total body bone mineral content (BMCt), total lean tissue mass (LTMt) and total fat mass (FMt) were measured and compared to expected data calculated from ideal weight for height (Wi; e.g. BMCti, LTMti, FMti). The bt (BMCt/BMCti), lt (LTMt/LTMti) and ft (FMt/FMti) ratios were used as quantitative variables. RESULTS: Low bt ratio was found at all ages (mean bt ratio 0.94 +/- 0.10; P < 0.001), even in children <6 years of age. However, the children's BMCt was satisfactorily adapted to their weight. lt and ft ratios were not constant across age groups. Children <10 years had 8% reduction of their lt ratio, maintaining normal levels thereafter. The opposite trend was found for ft ratio. Poor clinical, nutritional status and vitamin A levels were correlated with bt and lt ratios. CONCLUSION: Our results indicate that children with CF could have early alterations in their bone status and that lt and ft ratios did not have constant values across ages. Interpreting DXA data using this approach is suitable in children with CF.

Bone stiffness in children: part I. In vivo assessment of the stiffness of femur and tibia in children.

Although there are many publications concerning the mechanical behavior of adult bone, there are few data about mechanical properties of children's bone. In vivo bone stiffness measurement with Orthometer device has been validated and extensively used in adults to assess bone healing after fracture or lengthening. We hypothesized that in vivo stiffness measurement with Orthometer was applicable in children and was correlated with age, height, body weight, and corpulence index. The purpose was to establish baseline stiffness values for femur and tibia in growing children.Sixteen bone measurements (7 femurs and 9 tibias) were obtained during application of an external fixator for leg lengthening in 11 children aged between 5.5 and 16.7 years. A 3-point bending test with an Orthometer was carried out on the intact bone (before osteotomy) under general anesthesia. The anteroposterior stiffness measurement was successful in all children of the series, aged from 5.5 to 16.7 years. A wide variation of femoral and tibial bone stiffness values were observed. The use of a unique value as in adults as the end point of bending stiffness during bone healing process is not possible for children. The anteroposterior bone stiffness was found to have linear correlation with children's height and body weight, but not with age and corpulence indexes. The original data obtained by this study will give a stiffness reference for height and weight and could be useful as reference values for monitoring of healing process after fracture or limb lengthening.

Bone stiffness in children: part II. Objectives criteria for children to assess healing during leg lengthening.

BACKGROUND: The decision when to remove the frame after limb lengthening through standard distraction osteogenesis remains a challenge. Multiple studies have attempted to find objective criteria to assess bone healing after fracture or bone lengthening. However, there is a paucity of such data for the pediatric population. The purpose of this study was to correlate data obtained after dual-energy x-ray absorptiometry (DXA) measurement and bending stiffness in children to find an end-point value for the safe removal of an external fixation device. METHODS: We investigated 16 consecutive children aged between 5.5 and 16.7 years who had 22 lengthenings by callotasis. Twelve femurs and 10 tibiae were lengthened with a monoplane Orthofix external fixator. Fifty simultaneous measurements of bending bone stiffness measured with an Orthometer and DXA scans (bone mineral content [BMC], bone mineral density, volumetric bone mineral density, BMC/1 cm, Area/1 cm, BMC/1 cm, Area) were obtained during healing process. Four femoral fractures were reported after the removal of the external fixation device. Linear regression analysis was used to calculate the squared correlation coefficients for the relation between the DXA scans and the mechanical tests measuring bone stiffness. RESULTS: The bone stiffness measurement of the intact bone was compared with consecutive measurements of the bone stiffness of the regenerate, and it was expressed as a percentage (coefficient). We compared the BMC of the regenerate with the same bone area of the opposite limb. The best correlation was observed for anteroposterior (AP) bone stiffness coefficient and BMC coefficient (R = 0.82). The linear equation was BMC coefficient = 0.5 x AP stiffness coefficient + 30. The end point of 75% of BMC of the regenerate corresponds to 75% of the AP stiffness on DXA scanning; this is the time when we should consider safe removal of the fixator. CONCLUSIONS: Our method of comparing bone stiffness and DXA measurements gives an objective healing end point for every patient irrespective of his or her size. This method could allow noninvasive measurement of the end point and identified at-risk population of children, reducing regenerate fracture after bone lengthening.

Dual-energy X-ray aborptiometry assessment in children and adolescents with diseases that may affect the skeleton: the 2007 ISCD Pediatric Official Positions.

The Task Force focusing on the use of dual energy X-ray absorptiometry (DXA) in children and adolescents with diseases that may affect the skeleton reviewed over 300 articles to establish the basis for the Official Positions. A significant number of studies used DXA-based outcome measures to assess the effects of specific interventions and charted the natural history of incremental changes in bone size and mass in specific disease states in children. However, the utility of DXA in clinical practice has not been evaluated systematically, in large part due to the lack of a workable definition for childhood osteoporosis. Thus, in combination with the Official Positions addressing the diagnosis of osteoporosis in children, and the reporting of DXA results in children, this document presents clear guidelines from which clinicians and researchers alike can work. This report delineates a set of disorders in which it is appropriate to use DXA as part of the comprehensive assessment of skeletal health in children and adolescents, and provides guidance concerning the initiation of assessment and the frequency of monitoring. Importantly, this document also highlights significant gaps in our knowledge, emphasizing areas for future research.

Estimation of stature and length of limb segments in children and adolescents from whole-body dual-energy X-ray absorptiometry scans.

BACKGROUND: Anthropometric standards vary among different populations, and renewal of these reference values is necessary. OBJECTIVE: To produce formulae for the assessment of limb segment lengths. MATERIALS AND METHODS: Whole-body dual-energy X-ray absorptiometry scans of 413 Caucasian children and adolescents (170 boys, 243 girls) aged from 6 to 18 years were retrospectively analysed. Body height and the lengths of four long bones (humerus, radius, femur and tibia) were measured. The validity (concurrent validity) and reproducibility (intraobserver reliability) of the measurement technique were tested. RESULTS: High linear correlations (r > 0.9) were found between the mentioned five longitudinal measures. Corresponding linear regression equations for the most important relationships were derived. The tests of validity and reproducibility revealed a good degree of precision of the applied technique. CONCLUSION: The reference formulae obtained from the analysis of whole-body DEXA scans will be useful for anthropologists, and forensic and nutrition specialists, as well as for prosthetists and paediatric orthopaedic surgeons.

Bone mineral content and body composition in overweight children and adolescents.

The aim of this study was to analyze the bone mineral content (BMC) of the skeleton and the body composition in lean and fat masses in a population of young overweight subjects, before diet or medical intervention. A total of 496 white youths (298 females, 198 males) were studied. Their body mass index (BMI) values were 29.2+/-5.5 kg/m2 in females and 28.3+/-5.1 kg/m2 in males, corresponding to relative weights (wts) [actual wt, W, divided by the mean wt normal for height (ht), Wi] of 1.55+/-0.24 and 1.53+/-0.24, respectively. Whole-body dual-energy x-ray absorptiometry (DXA) scans were performed (Norland XR36 DXA system) to obtain the total BMC (BMCt), lean tissue mass (LTMt) and fat mass (FMt), as well as the values of the corresponding parameters in arms (a), legs (l), and abdomen (ab). The measured data were compared with theoretical values calculated for Wi. The differences with reference values in LTMt and FMt were sex dependent, and the accretion in FMt, greater in males than in females, yielded a similar FMt/LTMt ratio in both sexes. The wt corresponding to the BMC of the bearing skeleton, lower than the actual wt by about 20%, seemed a reasonable first step to consider in the wt management of these youths.

Bone mineral content and soft-tissue assessment in limb segments by dual-energy X-ray absorptiometry: optimal scan speed and pixel size.

The aim of this study was to define the best scanning parameters to assess bone mineral content (BMC) and bone mineral density (BMD) in specific dual-energy X-ray absorptiometry (DXA) applications, such as those encountered in orthopedics for the measurements of the peripheral skeleton. To simulate soft tissues and bones in a limb, we used simple phantoms made with plastic bottles (500 mL and 1500 mL) filled with tap water and cylinders of hydroxyapatite (HAP) powder set in a polymer at various concentrations (range, 0.150-1.500 g HAP/cm3). Data obtained from 204 measurements of these phantoms with different scanning speeds and pixel sizes showed that the best compromise for obtaining precise measurements in the shortest scan time was a scanning speed of 50 mm/s and a pixel size of 1.5 mm x 1.5 mm.

Quantitative computed tomography precision and accuracy for long-term follow-up of bone mineral density measurements: a five year in vitro assessment.

The purpose of this work was to test the long-term precision of quantitative computed tomography (QCT) on a CT scanner partly used for the measurement of bone mineral density (BMD). A spine phantom (ESP), which simulates three lumbar vertebrae (Li, i = 2-4) with given mineral densities of 50, 100, and 200 mg hydroxyapatite equivalents (HAP)/cm(3), respectively, was measured periodically over more than 5 yr on a Elscint-Marconi CT-Twin scanner. A total of 80 measurements were taken. The measured BMDi values were 48.4 +/- 1.2, 101.3 +/- 1.1, and 212.6 +/- 1.7 mg HAP/cm3, respectively (coefficient of variation [CV%] = 2.4, 1.1, and 0.8), and they were linearly correlated with the given density values (r > 0.99). The mean BMD value of the three simulated vertebrae was 120.8 +/- 1.1 mg HAP/cms(3) (CV% = 0.9), a value that corresponds to the mean lumbar BMD value in normal 65-yr-old women. We concluded that QCT is a precise and accurate method for long-term follow-up of BMD assessment in the population affected by osteoporosis.

Skeletal and total body volumes of human fetuses: assessment of reference data by spiral CT.

OBJECTIVE: To define reference data for skeletal and total body volumes of normal human fetuses. MATERIALS AND METHODS: Spiral CT was used to assess the skeletal and total body volumes of 31 normal human stillborn infants with gestational age (GA) and body weight (BW) ranging from 14 to 41.5 weeks and 22 to 3,760 g, respectively. CT scans (slice thickness 2.7 mm, pitch 0.7) were performed within the first 24 h after delivery. Precise bone and soft-tissue windows were defined from analysis of the density along the diaphysis of the fetal long bones and from the measurement of a phantom that mimics soft tissues. Lengths and volumes were obtained from 3D reconstructions. The femur lengths measured from CT images (FLct) were compared with those provided by US studies (FLus). RESULTS: Significant correlations ( r>0.9) were found between BW, measured volumes of the entire skeleton or head, long-bone lengths, biparietal diameter and GA. Strong linear correlations ( r>0.98) were observed between FLct and FLus. CONCLUSIONS: Skeletal and total body volume values obtained using spiral CT were significantly correlated with fetal biometric measurements. These data could complement those obtained in obstetric investigations with US.