Advanced finite element analysis of L4–L5 implanted spine segment

Abstract

In the paper finite element (FE) analysis of implanted lumbar spine segment is presented. The segment model consists of two lumbar vertebrae L4 and L5 and the prosthesis. The model of the intervertebral disc prosthesis consists of two metallic plates and a polyurethane core. Bone tissue is modelled as a linear viscoelastic material. The prosthesis core is made of a polyurethane nanocomposite. It is modelled as a non-linear viscoelastic material. The constitutive law of the core, derived in one of the previous papers, is implemented into the FE software Abaqus . It was done by means of the User-supplied procedure UMAT. The metallic plates are elastic. The most important parts of the paper include: description of the prosthesis geometrical and numerical modelling, mathematical derivation of stiffness tensor and Kirchhoff stress and implementation of the constitutive model of the polyurethane core into Abaqus software. Two load cases were considered, i.e. compression and stress relaxation under constant displacement. The goal of the paper is to numerically validate the constitutive law, which was previously formulated, and to perform advanced FE analyses of the implanted L4-L5 spine segment in which non-standard constitutive law for one of the model materials, i.e. the prosthesis core, is implemented.

Effect of graded posterior element and ligament removal on annulus stress and segmental stability in lumbar spine stenosis: a finite element analysis study

“…This spring was attached to the upper surface of the L2 endplate and connected to a floating rigid body, which simulated muscle power using the “joint” command. Several authors have previously conducted finite element analyses on the lumbar spine, focusing on the functional spinal unit or specific levels ( Goel et al, 1993 ; Pawlikowski et al, 2015 ). Our model exhibited consistent intradiscal pressure results with those of previous studies, such as Xu’s flexion and extension intradiscal pressures ( Xu et al, 2017 ).…”

“…Finite Element Analysis (FEA) is a commonly used method for investigating the biomechanics of the human lumbar spine ( Eberlein et al, 2004 ; Dreischarf et al, 2014 ; Pawlikowski et al, 2015 ; Xu et al, 2017 ; Zhang et al, 2018 ). FEA allows researchers and clinicians to gain insights into the biomechanical behavior of the spine affected by stenosis.…”

Finite element modeling to predict the influence of anatomic variation and implant placement on performance of biological intervertebral disc implants

“…FE analysis is particularly attractive in this case to test a range of parameters that may be critical to surgically implanted TE‐IVDs 31,32 . Previous attempts at modeling cage structures with simplified geometries have been performed to analyze stress distribution and displacement, but none have focused on predicting the mechanical performance and failure of cage structures in the cervical spine 27,31–37 . Furthermore, to the best of our knowledge, there has not been any simulations which utilized the unique geometry of the porcine cervical spine to understand the mechanical behavior of the cage in vivo.…”

“… 31 , 32 Previous attempts at modeling cage structures with simplified geometries have been performed to analyze stress distribution and displacement, but none have focused on predicting the mechanical performance and failure of cage structures in the cervical spine. 27 , 31 , 32 , 33 , 34 , 35 , 36 , 37 Furthermore, to the best of our knowledge, there has not been any simulations which utilized the unique geometry of the porcine cervical spine to understand the mechanical behavior of the cage in vivo. Therefore, capturing the anatomical geometry and simulating in vivo loading achieves a model that closely evaluates cage stability under non‐uniform loading.…”

“…1,23,26 While in vivo experimentation is valuable in providing insight on implant behavior and performance, surgical testing is often expensive and time-consuming. Computational simulations utilizing finite element (FE) analysis can aid in our understanding of material properties and systems of high complex geometry, [27][28][29] and provide biomechanical insight into the feasibility of materials as implants. 28,30 FE analysis is particularly attractive in this case to test a range of parameters that may be critical to surgically implanted TE-IVDs.…”