An anisotropic multiphysics damage model with application to annulus fibrosus

Abstract

An anisotropic multiphysics damage model is developed to characterize the couplings among multiple physical fields within soft tissues and the tissue damage based on thermodynamic principles. This anisotropic multiphysics damage model integrates the continuum mixture theory and a continuum damage model, and the anisotropic damage is considered by evolution of internal damage variables governing the anisotropic mechanical behaviors of tissues. The energy dissipation associated with the transport of fluid and ions is generally related to tissue damage. The anisotropic multiphysics damage model is applied to simulate a case of annulus fibrosus (AF) damage in an isolated intervertebral disc under compression, to understand the damage initiation and propagation. It is found that, for this case (with 1000 N/s of compression rate and neglected ground matrix damage), the damage initiated in the outer and middle posterior regions of AF at about 700 N of disc compression. The region-dependent yield stretch ratio predicted by this model is consistent with experimental findings. A sensitive study on the damage parameters is also presented. This study provides an additional insight into AF damage in the isolated disc under mechanical compression.

A Review on Damage and Rupture Modelling for Soft Tissues

“…The model proposed by Ghasemi et al [ 35 ] also captured soft tissue rupture. In addition, to circumvent the mesh dependency in CDM, a local gradient enhancement [ 66 , 74 ] and nonlocal integrals were applied [ 70 , 76 ]. While most of the reviewed models used a stretch-based damage evolution, Mousavi et al [ 71 ] have used a fracture energy-based damage evolution.…”

“…For instance, simulation of the sutured condition of the vascular or skin grafts to evaluate the near in-vivo fracture toughness would help design artificial grafts. Further, the damage model of Gao et al [ 70 ] can be extended to simulate ocular infections as this model captures the softening and tissue hydration. Moreover, corneal ectasia, where localised progressive softening occurs, can be studied by extending the model of Volokh to the cornea [ 88 ].…”

“…An anisotropic multi-physics damage model to capture damage initiation and propagation in annulus fibrosus was proposed by Gao et al [ 70 ]. This model was derived based on the damage model proposed by Balzini et al [ 37 ] by integrating continuum mixture theory and CDM.…”