title: The poro-viscoelastic properties of trabecular bone: a micro computed tomography-based finite element study.
abstract: Bone is a porous structure with a solid phase that contains hydroxyapatite and collagen. Due to its composition, bone is often represented either as a poroelastic or as a viscoelastic material; however, the poro-viscoelastic formulation that allows integrating the effect of both the fluid flow and the collagen on the mechanical response of the tissue, has not been applied yet. The objective of this study was to develop a micro computed tomography (µCT)-based finite element (FE) model of trabecular bone that includes both the poroelastic and the viscoelastic nature of the tissue. Cubes of trabecular bone (N=25) from human distal tibia were scanned with µCT and stress relaxation experiments were conducted. The µCT images were the basis for sample specific FE models, and the stress relaxation experiments were simulated applying a poro-viscoelastic formulation. The model considers two scales of the tissue: the intertrabecular pore and the lacunar-canalicular pore scales. Independent viscoelastic and poroelastic models were also developed to determine their contribution to the poro-viscoelastic model. All the experiments exhibited a similar relaxation trend. The average reaction force before relaxation was 9.28 × 10(2)N (SD ± 5.11 × 10(2)N), and after relaxation was 4.69 × 10(2)N (SD ± 2.88 × 10(2)N). The slope of the regression line between the force before and after relaxation was 1.92 (R(2)=0.96). The poro-viscoelastic models captured 49% of the variability of the experimental data before relaxation and 33% after relaxation. The relaxation predicted with viscoelastic models was similar to the poro-viscoelastic ones; however, the poroelastic formulation underestimated the reaction force before relaxation. These data suggest that the contribution of viscoelasticity (fluid flow-independent mechanism) to the mechanical response of the tissue is significantly greater than the contribution of the poroelasticity (fluid flow-dependent mechanism).
authors.affiliation: McCaig Institute for Bone and Joint Health, University of Calgary, Canada; Department of Radiology, Faculty of Medicine, University of Calgary, Canada.
authors.forename: Clara
authors.initials: C
authors.lastname: Sandino
authors.affiliation: McCaig Institute for Bone and Joint Health, University of Calgary, Canada; Department of Radiology, Faculty of Medicine, University of Calgary, Canada.
authors.forename: David D
authors.initials: DD
authors.lastname: McErlain
authors.affiliation: McCaig Institute for Bone and Joint Health, University of Calgary, Canada; Roger Jackson Centre for Health and Wellness Research, University of Calgary, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Schipilow
authors.affiliation: McCaig Institute for Bone and Joint Health, University of Calgary, Canada; Department of Radiology, Faculty of Medicine, University of Calgary, Canada; Roger Jackson Centre for Health and Wellness Research, University of Calgary, Canada; Schulich School of Engineering, University of Calgary, Canada. Electronic address: skboyd@ucalgary.ca.
authors.forename: Steven K
authors.initials: SK
authors.lastname: Boyd
mesh_terms: D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D016062:Porosity; D013977:Tibia / Q000166:cytology / Q000000981:diagnostic imaging*; D014783:Viscosity; D055114:X-Ray Microtomography
keywords: Finite element models; Micro computed tomography; Poro-viscoelasticity; Trabecular bone