Finite element modeling of hyper-viscoelasticity of peripheral nerve ultrastructures

• Published in: Journal of biomechanics Vol. 48; no. 10; pp. 1982 - 1987
• Main Authors: Chang, Cheng-Tao, Chen, Yu-Hsing, Lin, Chou-Ching K., Ju, Ming-Shaung
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 16.07.2015; Elsevier Limited
• Subjects: Animals; Biomechanical Phenomena; Cross-Sectional Studies; Diabetes; Dynamics; Elasticity; Finite Element Analysis; Finite element method; Hyper-viscoelasticity; Inverse finite element; Materials Testing; Mathematical analysis; Mathematical models; Nerves; Nervous system; Nonlinear Dynamics; Optical coherence tomography; Peripheral nerve tissues; Peripheral nerves; Peripheral Nerves - ultrastructure; Physical Medicine and Rehabilitation; Rats; Stress relaxation; Studies; Tissue engineering; Tomography, Optical Coherence; Viscoelasticity; Viscosity; Peripheral nerve tissues; Inverse finite element; Hyper-viscoelasticity; Optical coherence tomography; Tissue engineering
• ISSN: 0021-9290; 1873-2380; 1873-2380
• DOI: 10.1016/j.jbiomech.2015.04.004

The mechanical characteristics of ultrastructures of rat sciatic nerves were investigated through animal experiments and finite element analyses. A custom-designed dynamic testing apparatus was used to conduct in vitro transverse compression experiments on the nerves. The optical coherence tomography (OCT) was utilized to record the cross-sectional images of nerve during the dynamic testing. Two-dimensional finite element models of the nerves were built based on their OCT images. A hyper-viscoelastic model was employed to describe the elastic and stress relaxation response of each ultrastructure of the nerve, namely the endoneurium, the perineurium and the epineurium. The first-order Ogden model was employed to describe the elasticity of each ultrastructure and a generalized Maxwell model for the relaxation. The inverse finite element analysis was used to estimate the material parameters of the ultrastructures. The results show the instantaneous shear modulus of the ultrastructures in decreasing order is perineurium, endoneurium, and epineurium. The FE model combined with the first-order Ogden model and the second-order Prony series is good enough for describing the compress-and-hold response of the nerve ultrastructures. The integration of OCT and the nonlinear finite element modeling may be applicable to study the viscoelasticity of peripheral nerve down to the ultrastructural level.