Tissue viscoelasticity is related to tissue composition but may not fully predict the apparent-level viscoelasticity in human trabecular bone – An experimental and finite element study

TY - JOUR

T1 - Tissue viscoelasticity is related to tissue composition but may not fully predict the apparent-level viscoelasticity in human trabecular bone – An experimental and finite element study

AU - Ojanen, X.

AU - Tanska, P.

AU - Malo, M. K.H.

AU - Isaksson, H.

AU - Väänänen, S. P.

AU - Koistinen, A. P.

AU - Grassi, L.

AU - Magnusson, S. P.

AU - Ribel-Madsen, S. M.

AU - Korhonen, R. K.

AU - Jurvelin, J. S.

AU - Töyräs, J.

PY - 2017/12/8

Y1 - 2017/12/8

N2 - Trabecular bone is viscoelastic under dynamic loading. However, it is unclear how tissue viscoelasticity controls viscoelasticity at the apparent-level. In this study, viscoelasticity of cylindrical human trabecular bone samples (n = 11, male, age 18–78 years) from 11 proximal femurs were characterized using dynamic and stress-relaxation testing at the apparent-level and with creep nanoindentation at the tissue-level. In addition, bone tissue elasticity was determined using scanning acoustic microscope (SAM). Tissue composition and collagen crosslinks were assessed using Raman micro-spectroscopy and high performance liquid chromatography (HPLC), respectively. Values of material parameters were obtained from finite element (FE) models by optimizing tissue-level creep and apparent-level stress-relaxation to experimental nanoindentation and unconfined compression testing values, respectively, utilizing the second order Prony series to depict viscoelasticity. FE simulations showed that tissue-level equilibrium elastic modulus (Eeq) increased with increasing crystallinity (r = 0.730, p =.011) while at the apparent-level it increased with increasing hydroxylysyl pyridinoline content (r = 0.718, p =.019). In addition, the normalized shear modulus g1 (r = −0.780, p =.005) decreased with increasing collagen ratio (amide III/CH2) at the tissue-level, but increased (r = 0.696, p =.025) with increasing collagen ratio at the apparent-level. No significant relations were found between the measured or simulated viscoelastic parameters at the tissue- and apparent-levels nor were the parameters related to tissue elasticity determined with SAM. However, only Eeq, g2 and relaxation time τ1 from simulated viscoelastic values were statistically different between tissue- and apparent-levels (p <.01). These findings indicate that bone tissue viscoelasticity is affected by tissue composition but may not fully predict the macroscale viscoelasticity in human trabecular bone.

AB - Trabecular bone is viscoelastic under dynamic loading. However, it is unclear how tissue viscoelasticity controls viscoelasticity at the apparent-level. In this study, viscoelasticity of cylindrical human trabecular bone samples (n = 11, male, age 18–78 years) from 11 proximal femurs were characterized using dynamic and stress-relaxation testing at the apparent-level and with creep nanoindentation at the tissue-level. In addition, bone tissue elasticity was determined using scanning acoustic microscope (SAM). Tissue composition and collagen crosslinks were assessed using Raman micro-spectroscopy and high performance liquid chromatography (HPLC), respectively. Values of material parameters were obtained from finite element (FE) models by optimizing tissue-level creep and apparent-level stress-relaxation to experimental nanoindentation and unconfined compression testing values, respectively, utilizing the second order Prony series to depict viscoelasticity. FE simulations showed that tissue-level equilibrium elastic modulus (Eeq) increased with increasing crystallinity (r = 0.730, p =.011) while at the apparent-level it increased with increasing hydroxylysyl pyridinoline content (r = 0.718, p =.019). In addition, the normalized shear modulus g1 (r = −0.780, p =.005) decreased with increasing collagen ratio (amide III/CH2) at the tissue-level, but increased (r = 0.696, p =.025) with increasing collagen ratio at the apparent-level. No significant relations were found between the measured or simulated viscoelastic parameters at the tissue- and apparent-levels nor were the parameters related to tissue elasticity determined with SAM. However, only Eeq, g2 and relaxation time τ1 from simulated viscoelastic values were statistically different between tissue- and apparent-levels (p <.01). These findings indicate that bone tissue viscoelasticity is affected by tissue composition but may not fully predict the macroscale viscoelasticity in human trabecular bone.

KW - Collagen crosslink

KW - Composition

KW - Finite element modeling

KW - Trabecular bone

KW - Viscoelasticity

U2 - 10.1016/j.jbiomech.2017.10.002

DO - 10.1016/j.jbiomech.2017.10.002

M3 - Journal article

C2 - 29108850

AN - SCOPUS:85032936687

SN - 0021-9290

VL - 65

SP - 96

EP - 105

JO - Journal of Biomechanics

JF - Journal of Biomechanics

ER -