In Vivo Assessment of Elasticity of Child Rib Cortical Bone Using Quantitative Computed Tomography.

Y Zhu,F Bermond,J.-P Pracros,J Payen De La Garanderie,D Mitton,B Sandoz,D Brizard,F Rongieras,J.-B Pialat,W Skalli

doi:10.1155/2017/2471368

Abstract

Elasticity of the child rib cortical bone is poorly known due to the difficulties in obtaining specimens to perform conventional tests. It was shown on the femoral cortical bone that elasticity is strongly correlated with density for both children and adults through a unique relationship. Thus, it is assumed that the relationships between the elasticity and density of adult rib cortical bones could be expanded to include that of children. This study estimated in vivo the elasticity of the child rib cortical bone using quantitative computed tomography (QCT). Twenty-eight children (from 1 to 18 y.o.) were considered. Calibrated QCT images were prescribed for various thoracic pathologies. The Hounsfield units were converted to bone mineral density (BMD). A relationship between the BMD and the elasticity of the rib cortical bone was applied to estimate the elasticity of children's ribs in vivo. The estimated elasticity increases with growth (7.1 ± 2.5 GPa at 1 y.o. up to 11.6 ± 1.9 GPa at 18 y.o.). This data is in agreement with the few previous values obtained using direct measurements. This methodology paves the way for in vivo assessment of the elasticity of the child cortical bone based on calibrated QCT images.

Highlights

The knowledge of the mechanical properties of the child rib cortical bone could be useful for ribcage models
We provide a regression to convert BMDclin to by high-resolution peripheral quantitative computed tomography HR-pQCT (BMDHR)
Bone mineral density (BMDclin) in mg K2HPO4/cm3 Using a relationship obtained from cross‒calibration of the Model 3CT Calibration Phantom and the CIRS Phantom 062M: BMDclin = 1.08 BMDclin + 55.77 (r2 = 0.99, standard error of estimate (SEE) = 64.26 mg HA/cm3, p < 0.001)

Summary

Introduction

The knowledge of the mechanical properties of the child rib cortical bone could be useful for ribcage models. Such models could be used to assess mechanical loading on the thorax (e.g., for brace treatment or car crash accidents). The mechanical properties of pediatric thoracic tissues have been poorly studied due to difficulties in obtaining specimens to perform conventional tests [1, 2]. Regarding the rib cortical bone of children, mechanical data are extremely limited [1]. To the authors’ knowledge, only a handful of studies exploring pediatric rib mechanical properties can be found in the existing literature [3,4,5]. Some other studies did not focus on children, but the population included donors younger than 18 years [6,7,8,9]

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