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Computational Modelling of the Intervertebral Disc Using Abaqus
Published in J. Middleton, M. L. Jones, G. N. Pande, Computer Methods in Biomechanics & Biomedical Engineering – 2, 2020
J. S. Tan, S. H. Teoh, G. W. Hastings, C. T. Tan, Y. S. Choo
The intervertebral disc is made up of two constituents, the nucleus pulposus and the annulus fibrosus which are sandwiched between two endplates. It is the disc that allows for the movement of a vertebral body, and at the same time restricts the movements allowed. It also transmits forces from one vertebral body to another. Each of these two constituents of the intervertebral disc performs a different role under different loading conditions. From the mechanical point of view, the nucleus pulposus, which can be considered as a ball of fluid, transmits forces exerted on it hydraulically and evenly in all directions. The annulus fibrosus, with its uniquely orientated fibers, opposes the axial rotation of one endplate with respect to the other. It surrounds the nucleus like a rubber band to restrict its bulge. As a whole, the intervertebral disc is able to sustain different kinds of loading conditions, thus allowing for the motion of the adjoining vertebral bodies. Under axial compressive load, the force is absorbed by the nucleus, which is in turn transmitted hydraulically to the annulus fibrosus. Under torsion, the fibers resist the force exerted in the circumferential direction and hence restricting the relative motion of the adjacent vertebrals.
Spine
Published in David A Lisle, Imaging for Students, 2012
Sciatica is usually caused by herniation of intervertebral disc, or by spinal stenosis due to degenerative disease. Each intervertebral disc is composed of a tough outer layer, the annulus fibrosis, and a softer semifluid centre, the nucleus pulposus. With degeneration of the disc, small microtears appear in the annulus fibrosis allowing generalized bulging of the nucleus pulposus. This causes the disc to bulge beyond the margins of the vertebral bodies causing narrowing of the spinal canal. Secondary effects of degenerative disc disease include abnormal stresses on the vertebral bodies leading to osteophyte formation, as well as facet joint sclerosis and hypertrophy. These changes may lead to further narrowing of the spinal canal producing spinal canal stenosis.
Computer-Aided Diagnosis of Spinal Abnormalities
Published in de Azevedo-Marques Paulo Mazzoncini, Mencattini Arianna, Salmeri Marcello, Rangayyan Rangaraj M., Medical Image Analysis and Informatics: Computer-Aided Diagnosis and Therapy, 2018
Marcello H. Nogueira-Barbosa, Paulo Mazzoncini de Azevedo-Marques
The intervertebral disc is a fibrocartilaginous structure connecting and articulating two adjacent vertebral bodies, being also responsible for significant absorption of mechanical load. Intervertebral disc histology comprises two distinct regions named nucleus pulposus and annulus fibrosus. Nucleus pulposus is the central intervertebral disc region, composed mainly by glycosaminoglycans and collagen type II fibers, and typically with a strongly hydrated extracellular matrix. Annulus fibrosus is composed by several concentric ring layers of fibrocartilage with type I and type II collagen, and represents the peripheral intervertebral disc region.
Biomechanical response of lumbar intervertebral disc in daily sitting postures: a poroelastic finite element analysis
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Liang-dong Zheng, Yu-ting Cao, Yi-ting Yang, Meng-lei Xu, Hui-zi Zeng, Shi-jie Zhu, Antonio Candito, Yuhang Chen, Rui Zhu, Li-ming Cheng
Intervertebral disc degeneration is a clinical degenerative disease closely related to mechanical loads (Adams and Roughley 2006). The disc sustains the compressive load for prolonged periods, exhibiting a creep behavior, where its compressive deformation often worsens (Adams et al. 1987; Adams et al. 1996). The increased deformation of the disc often causes higher stress, which may lead to mechanical damage accumulation and initiate the disc degeneration (Adams et al. 2000). Meanwhile, the disc gradually becomes less hydrated due to severe efflux of fluid (McMillan et al. 1996) and could have more significant elastic behavior than viscoelasticity. As a result, a declined energy dissipation capacity of the disc could lead to the increasing risk of disc failure (Jamison and Marcolongo 2014). Upright, flexed and extended sittings are three most common postures during daily life (Wong et al. 2019), and maintaining a sustained sitting posture over a prolonged period of time may put the disc under a physiologically unfavorable mechanical environment, further increasing the likelihood of disc degeneration.
Biomechanical effect of intervertebral disc degeneration on the lower lumbar spine
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Hongkun Wang, Nan Li, Huiwen Huang, Peng Xu, Yubo Fan
The FE model of the lumbar was developed based on the CT images with a thickness of 0.625 mm. In this case, CT information from a healthy male subject(age: 30 years, weight: 68 kg, height:173 cm). Mimics (Materialise Technologies, Belgium)、Geomagic (Geomagic, USA)、 Hypermesh (Altair Engineering Corp, USA) and Abaqus (SIMULIA, USA) have been used to establish 3D finite element model successively. The modeling process is to process the CT images by Mimics and Geomagic to generate a 3 D model, then use Hypermesh for mesh division, and finally perform simulation calculation in Abaqus (Xu et al., 2021). The normal lumbar L2∼S1 segment model is set up as shown in Figure 1, the complete FE model includes cortical bone, cancellous bone, articular cartilage, intervertebral disc, and endplate and ligament. Ligament including anterior longitudinal ligament (ALL), and longitudinal ligament (PLL), the transverse process after ligament (TL), spine ligament (SSL), spine ligament (ISL) and ligament models are incompressible linear units (Liu et al. 2022; Wang et al. 2018). Cortical bone thickness was set at 0.5 mm. The thickness of articular cartilage is 0.5 mm, which is defined as a two-dimensional shell element. The contact between articular cartilage is set as the surface contact with friction, and the friction coefficient is 0.1 (Zhou et al. 2022). The intervertebral disc consists of the nucleus pulposus, annulus fibrosus, and annulus fibre substance. Normal model element types and material parameters are shown in Table 1 (Elfering et al. 2002; Du et al. 2014).
Topology optimization and dynamic characteristic evaluation of W-shaped interspinous process device
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
A three-dimensional finite element (FE) model of L1–L5 segments was established based on computed tomography scan images of a healthy adult female (48 years old, 58 kg and 162 cm) with no spine diseases. The software ANSA (Version 15.2.0, International AG, Switzerland) was utilized for meshing in this study. Then the FE model of L1–L5 was input into ABAQUS (Version 6.14-5,Dassault Systèmes, USA) to define loads and conduct FE analyses. The intact FE model of the lumbar spine consisted of vertebrae, intervertebral discs, endplates, and seven ligaments: supraspinous, interspinous, ligamentum flavum, transverse, posterior longitudinal, anterior longitudinal, and capsular. The vertebrae were divided into cortical bone (0.5–1.0 mm thickness) and internal cancellous bone due to accounting for the difference in material properties. The intervertebral discs were composed of the nucleus pulposus and the annulus ground substance. The six-layer annular fibers were embedded in the ground substance and placed in an anatomic orientation modeled using two-node link elements with tension resistance only. The seven major spinal ligaments were simulated by 2-node tension-only truss elements. The intact FE model of the lumbar spine included 140,068 solid elements and 9600 truss elements. The material properties of each part were obtained from previous studies (Fan and Guo 2018; Sharma et al. 1995; Schmidt et al. 2006; Kong and Goel 2001). A more detailed description on material properties is displayed in Table 1.