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

X Ojanen; P Tanska; M K H Malo; H Isaksson; S P Väänänen; A P Koistinen; L Grassi; S P Magnusson; S M Ribel-Madsen; R K Korhonen; J S Jurvelin; J Töyräs

doi:10.1016/j.jbiomech.2017.10.002

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

J Biomech. 2017 Dec 8:65:96-105. doi: 10.1016/j.jbiomech.2017.10.002. Epub 2017 Oct 13.

Authors

X Ojanen¹, P Tanska², M K H Malo², H Isaksson³, S P Väänänen⁴, A P Koistinen⁵, L Grassi³, S P Magnusson⁶, S M Ribel-Madsen⁷, R K Korhonen⁴, J S Jurvelin², J Töyräs⁴

Affiliations

¹ Department of Applied Physics, University of Eastern Finland, POB 1627, FI-70211 Kuopio, Finland. Electronic address: xiaowei.ojanen@uef.fi.
² Department of Applied Physics, University of Eastern Finland, POB 1627, FI-70211 Kuopio, Finland.
³ Department of Biomedical Engineering, Lund University, POB 118, 221 00 Lund, Sweden.
⁴ Department of Applied Physics, University of Eastern Finland, POB 1627, FI-70211 Kuopio, Finland; Diagnostic Imaging Center, Kuopio University Hospital, POB 100, FI-70029 Kuopio, Finland.
⁵ SIB Labs, University of Eastern Finland, PO Box 1627, FI-70211 Kuopio, Finland.
⁶ Department of Physical Therapy, Bispebjerg Hospital, Denmark; Institute of Sports Medicine, Department of Orthopaedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
⁷ Institute of Sports Medicine, Department of Orthopaedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.

PMID: 29108850
DOI: 10.1016/j.jbiomech.2017.10.002

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 (E_eq) 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 E_eq, 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.

Keywords: Collagen crosslink; Composition; Finite element modeling; Trabecular bone; Viscoelasticity.

MeSH terms

Adolescent
Adult
Aged
Cancellous Bone / physiology*
Collagen / metabolism
Computer Simulation
Elastic Modulus
Femur / physiology*
Finite Element Analysis
Humans
Male
Middle Aged
Models, Biological
Viscosity
Young Adult

Substances

Collagen