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. (8th December 2017)

• Record Type: Journal Article
• Authors: Ojanen, X.; Tanska, P.; Malo, M.K.H.; Isaksson, H.; Väänänen, S.P.; Koistinen, A.P.; Grassi, L.; Magnusson, S.P.; Ribel-Madsen, S.M.; Korhonen, R.K.; Jurvelin, J.S.; Töyräs, J.
• Is Part Of: Journal of biomechanics. Volume 65(2017)
• Page Start: 96
• Page End: 105
• Publication Date: 2017-12-08
• Subjects: Trabecular bone -- Viscoelasticity -- Composition -- Collagen crosslink -- Finite element modeling; Animal mechanics -- Periodicals; Biomechanics -- Periodicals; Biomechanics -- Periodicals; Mécanique animale -- Périodiques; Biomécanique -- Périodiques; Electronic journals; 571.4305
• DOI: 10.1016/j.jbiomech.2017.10.002
• Languages: English
• ISSNs: 0021-9290

Abstract

Abstract: 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.