Poroelastic analysis of vertebral trabecular bone

Junghwa Hong, Marquette University

Abstract

Trabecular bone is a composite material consisting of a porous solid phase and a fluid phase. Fluid in bone is known to perform complex functions such as active biological transport and playing a role in the remodeling process. The presence intraosseous fluid is postulated to contribute to the energy absorbing properties and time-dependent behavior. The theory of poroelasticity has been used to simulate the bone behavior incorporating the intraosseous fluid flow. Results of these analytical studies demonstrated the significance of including the fluid phase in bone mechanics. Limitations in these studies, however, are the use of assumed values of poroelastic properties of bone and the lack of experimental validation of their model predictions. The theory of poroelasticity shows that five poroelastic properties, drained shear modulus (G), drained and undrained Poisson's ratio (v and $v\rm\sb{u}$), Skempton's coefficient (B), and permeability coefficient ($\kappa$), are needed for a complete isotropic characterization of a poroelastic material. In this study, experimental protocols were developed for the measurement of the poroelastic properties of trabecular bone. The measured G and v were similar to measured values of other trabecular bone. The values of $v\rm\sb{u}$ and B measured are within the theoretical ranges. The measured $\kappa$ values were also reasonable based on the Kozeny-Carman equation. A 2-D poroelastic model was developed and solved numerically to investigate the effect of the strain rate on the mechanical behavior of trabecular bone in the uniaxial stress condition. The compressibility of the porous solid and fluid phases of trabecular bone was incorporated for the numerical solutions. Compression tests in the uniaxial stress were performed to validate the poroelastic model. Both predicted and observed mechanical behavior showed enhancement of elastic modulus with increasing strain rate input and good agreement. All predicted elastic moduli were within the standard error range of the experimental results. This suggested that trabecular bone is a poroelastic material that its mechanical behavior is significantly affected by the fluid phase, and the poroelastic modeling would be useful for studying the effect of intraosseous fluid on the mechanical behavior at the continuum level.

Recommended Citation

Junghwa Hong, "Poroelastic analysis of vertebral trabecular bone" (January 1, 1996). Dissertations (1962 - 2010) Access via Proquest Digital Dissertations. Paper AAI9634268.
http://epublications.marquette.edu/dissertations/AAI9634268

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