Original Article
Bone Mineral Density, Hip Bone Geometry, and Calcaneus Trabecular Bone Texture in Obese and Normal-Weight Children

https://doi.org/10.1016/j.jocd.2013.02.001Get rights and content

Abstract

Our study aimed at comparing bone mineral density (BMD), geometric indices of hip bone strength, and indices of trabecular bone texture at the calcaneus in obese and normal-weight children. Fifty-three obese children (10.3 ± 1.4 yr) and 24 normal-weight children (10.4 ± 1.5 yr) participated in this study. Body composition, bone mineral content, and BMD at whole body (WB), lumbar spine (L2–L4), total forearm, and proximal femur (total hip [TH] and femoral neck [FN]) were measured by dual-energy X-ray absorptiometry (DXA). Bone geometry of the hip was evaluated by the hip structure analysis (HSA) program. DXA scans were analyzed at the FN at its narrowest region and the femoral shaft (FS) by the HSA program. Cross-sectional area (CSA) and section modulus (Z) were measured from hip BMD profiles. Texture analysis was performed on digitized radiographs of the calcaneus to assess trabecular bone microarchitecture, and the result was expressed as Hmean. WB BMD, L2–L4 BMD, TH BMD, and FN BMD were significantly higher in obese children compared with normal-weight peers (p < 0.05). FN Z and FS Z were not significantly different between the 2 groups, whereas Hmean parameter was significantly lower in obese children compared with normal-weight peers (p < 0.001). After adjustment for body weight, obese children displayed lower WB BMD, FN CSA, FN Z, FS CSA, and FS Z compared with normal-weight children. This study suggests that BMD of WB and geometric indices of hip bone strength are not adapted to the increased body weight in obese children.

Introduction

Childhood obesity has been linked to an increase in fracture risk at the upper extremities 1, 2, 3. Dual-energy X-ray absorptiometry (DXA) is an accurate method to assess body composition and bone mass in normal-weight and obese children 4, 5. To date, several studies have aimed at studying the skeleton of obese children and adolescents 6, 7, 8, 9, 10, 11, 12, 13. It has been shown that obese children have either lower 6, 7, 8, 9, greater 10, 11, or equivalent (13) bone mass than healthy weight children. These differences could be related to differing approaches for the assessment of 2-dimensional (2D) projected DXA bone measures relative to age, bone size, and body size 10, 11. Furthermore, the influence of being obese on bone parameters in growing children may be influenced by gender and maturity 10, 11.

Although bone mineral density (BMD) is a strong predictor of fracture risk, it only explains a part of bone strength 14, 15. In reality, the organization of the trabecular bone (microarchitecture), shape and geometry of bones (macroarchitecture), and intrinsic properties of the matrix (mineral and collagen) also contribute to bone strength 14, 15. Interestingly, Benhamou et al (16) have validated an approach to evaluate bone microarchitecture from radiographs by measuring the Hmean parameter determining the fractal dimension. Hmean measurement is related to trabecular bone structure properties, such as porosity, connectivity, and bone strength 16, 17, 18, 19, 20. This method has also been used in children (19). Bone strength is also related to bone geometry 21, 22, 23. Proximal femur DXA scan images have been used to assess femoral bone geometry using the method previously described by Martin and Burr (21) and later modified by Beck et al (22). We have recently demonstrated that proximal femur bone geometry is well adapted to body weight in overweight adolescent boys but not in obese adolescent boys (24). However, the influence of being obese on BMD, bone geometry, and microarchitecture in prepubertal children and early pubertal is not completely understood. The aim of this study was to compare BMD, geometric indices of hip bone strength, and indices of trabecular bone texture at the calcaneus in obese and normal-weight children.

Section snippets

Subjects and Study Design

The study participants were recruited from primary schools in Orleans area, France, via information meetings, flyers, or newspaper advertisements. Inclusion criteria were male or female from 7 to 11 yr, Tanner stages I or II, being without endocrine or genetic abnormalities, no diagnosis of comorbidity, and no history of fracture. These criteria were checked during a previous medical examination. The subjects were not under any medication known to affect bone metabolism. Children were divided

Subject Characteristics and Body Composition

Gender distribution, Tanner stage, age, bone age, height, total energy expenditure, time spent in the sport club, daily calcium intake (DCI), and serum 25(OH)D were not statistically different between the 2 groups. Body weight, fat mass, fat mass percentage, lean mass, BMI, and serum leptin were significantly higher in obese children compared with controls. Serum osteocalcin and cross-laps (CTX) were significantly lower in obese children compared with controls (Table 1).

DXA Measurements

WB BMD, L2–L4 BMD, total

Discussion

In this study, we showed that obese children displayed lower WB BMD, FN CSA, FN Z, FS CSA, and FS Z values compared with normal-weight children after adjustment for body weight. Thus, this study suggests that BMD of WB and geometric indices of hip bone strength are not adapted to the increased body weight in obese children.

In our study, obese children had significantly lower CTX and osteocalcin levels compared with normal-weight peers. Thus, it seems that pediatric obesity slows bone remodeling

Acknowledgments

We thank the Danone Institute and The Foundation for the Medical Research for their financial support.

Conflicts of interest: Claude-Laurent Benhamou has regularly worked with several pharmaceutical laboratories on different topics (clinical research, conferences, postuniversity teaching, and boards): Amgen, GSK, Lilly, Merck Sharp Dohme, Novartis, Roche/Roche Chugai, Servier, UCB Pharma, and Wyeth. Besides, Claude Laurent Benhamou has directed the PhD thesis of Emilie Rocher that has been

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