Geometric indices of hip bone strength in obese, overweight, and normal-weight adolescent boys.

UNLABELLED: The aim of this study was to compare hip bone strength indices in obese, overweight, and normal-weight adolescent boys using hip structure analysis. After adjusting for weight, obese boys displayed lower intertrochanteric cross-sectional moment of inertia and femoral shaft cross-sectional moment of inertia and section modulus in comparison to normal-weight and overweight boys. This study suggests that in obese adolescent boys, femoral shaft bending strength is not adapted to the increased body weight.

INTRODUCTION: The influence of being obese or overweight on bone strength in adolescents remains controversial. The main aim of this study was to compare hip bone strength indices in obese, overweight, and normal-weight adolescent boys using hip structure analysis. The second aim of this study was to explore the influence of lean mass and fat mass on hip bone strength indices in the same population.

METHODS: This study included 70 adolescent boys (25 obese, 25 normal weight, and 20 overweight). The three groups (obese, overweight, and normal weight) were matched for maturity (Tanner stage) and age. Body composition and bone mineral density (BMD) were assessed by dual-energy X-ray absorptiometry (DXA). To evaluate hip bone strength, DXA scans were analyzed at the femoral neck (FN), the intertochanteric (IT), and the femoral shaft (FS) by the Hip Structure Analysis (HSA) program. Cross-sectional area (CSA), an index of axial compression strength, section modulus (Z), an index of bending strength, and cross-sectional moment of inertia (CSMI), an index of structural rigidity were measured from bone mass profiles.

RESULTS: Body weight, lean mass, fat mass and BMI were significantly higher in obese and overweight boys in comparison to normal-weight boys (P < 0.05). Total hip (TH) BMD and femoral neck (FN) BMD were significantly higher in obese and overweight boys in comparison to normal-weight boys (P < 0.05). After adjusting for age or maturation index, obese and overweight boys displayed significantly higher TH and FN BMD, CSA, CSMI, and Z of the three sites (FN, IT, and FS) in comparison to normal-weight boys (P < 0.05). However, after adjusting for weight, obese boys displayed significantly lower IT CSMI and FS CSMI and Z in comparison to normal-weight and overweight boys (P < 0.05).

CONCLUSIONS: This study suggests that in obese adolescent boys, intertrochanteric structural rigidity and femoral shaft structural rigidity and bending strength are not adapted to the increased body weight.