Biomechanics of spinal trauma
Youlian Hong, Roger Bartlett in Routledge Handbook of Biomechanics and Human Movement Science, 2008
As indicated, soft tissues interconnect vertebrae and consist of intervertebral discs and ligaments. Discs are located between C2 and S1 bodies and consist of annulus fibrosus and nucleus pulposus. Disc height varies by spinal region. The annulus fibrosus, the outer portion of the disc, is made up of concentric rings of fibrous tissue. Adjacent rings are approximately perpendicular. Fibres are oriented at 45° relative to the vertebral body in one ring and at 135° relative to the vertebral body in the adjacent ring. The nucleus pulposus residing at approximately the center of the disc, consists of gelatinous material. The size of the nucleus varies with the spinal region. While more prominent in cervical and lumbar regions, the nucleus is smaller in the thoracic region.
Intervertebral disk prolapse
Jacques Corcos, David Ginsberg, Gilles Karsenty in Textbook of the Neurogenic Bladder, 2015
The intervertebral disk in the adult is a complex avascular structure (Figure 22.1). The nucleus pulposus is composed of embryologically distinct chondrocyte-like cells and a loose collagen framework embedded in a gelatinous matrix of various glycosaminoglycans, water, and salts. In a healthy intervertebral disk, this material is under significant pressure and is restrained by dense collagenous annulus fibrosis. The annulus fibrosus is composed of numerous concentric layers of fibrocartilaginous tissue. Collagen fibers extend from the annulus to the surrounding tissues into both the longitudinal ligaments and the hyaline cartilage vertebral endplates superiorly and inferiorly. At the cranial and caudal ends of each disk, the vertebral endplates separate the vertebral bone from the disk and prevent the nucleus pulposus from bulging into the adjacent vertebrae. The disk absorbs the considerable hydrostatic pressure that results from mechanical loading of the spine. Endplate tissue is rich hyaline cartilage, which acts to bind the disk to the overlying vertebral bones. The endplates are typically less than 1 mm thick and are often thinnest in the central region adjacent to the nucleus.2–4 Herniated disks in the lower lumbar spine most often result from avulsion of the vertebral endplate junction between the disk and the spinal bone, rather than rupture of the annulus fibrosus itself.5
Acute low back pain
Michael Y. Wang, Andrea L. Strayer, Odette A. Harris, Cathy M. Rosenberg, Praveen V. Mummaneni in Handbook of Neurosurgery, Neurology, and Spinal Medicine for Nurses and Advanced Practice Health Professionals, 2017
Low back pain is localized to the lumbosacral region. There may be a radicular component if there is compression on an exiting nerve root. Typically, there are five lumbar vertebrae and five respective intervertebral discs between those vertebrae. (The bottom lumbar vertebra is connected via a disc to the sacrum.) The posterior aspect of the spine consists of the spinous process, lamina, transverse process, pars interarticularis, and facet joint. The intervertebral disc has a tough annulus fibrosus surrounding the softer nucleus pulposus. The nerve root exits the intervertebral foramen (where it lies close to the disc) and innervates a specific dermatome.
Parametric study of anterior percutaneous endoscopic cervical discectomy (APECD)
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Meng-Si Sun, Chen-Xi Yuchi, Xin-Yi Cai, Cheng-Fei Du, Zhong-Jun Mo
Following APECD surgery, stability of the surgical segment is among the most important outcomes for patients, as it is also for clinicians. That is because instability of the surgical segment is usually accompanied by various complications, such as a reduction in disc height and acceleration of degeneration of adjacent segments, causing the patient to suffer additional pain and requiring revision surgery which can increase financial pressure on the patient (Carrier et al. 2013). The nucleus pulposus plays a major role in sagittal stability of the cervical spine. From a mechanical point of view, when the cervical vertebral segment moves, the nucleus pulposus immediately participates in supporting the load and ensures that the height of the disc is maintained. The structure allows stress to be evenly distributed around the annulus fibrosus. When the nucleus pulposus becomes degenerated, the fulcrum for this support instantly disappears, reducing the height of the intervertebral disc and providing uneven stress around the ring of fibers, causing it to become easily damaged, and inititating segmental instability.
Numerical simulation of lateral and transforaminal lumbar interbody fusion, two minimally invasive surgical approaches
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
B. Areias, S. C. Caetano, L. C. Sousa, M. Parente, R. N. Jorge, H. Sousa, J. M. Gonçalves
Particular attention is necessary regarding the modelling of the nucleus material, which possesses incompressibility characteristics. The nucleus pulposus, mainly composed of water, is confined in its totality, acting as an incompressible material without fluid flow (del Palomar et al. 2008). Therefore, to characterise its behaviour, a hyperelastic model was considered, in particular, the Neo-Hookean model with 2008) (Moramarco et al. 2010). The annulus fibrosus was modelled as an anisotropic hyperelastic material, according to the HGO constitutive model, with 2012; Momeni Shahraki et al. 2015).
Accurate simulation of the herniated cervical intervertebral disc using controllable expansion: a finite element study
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Dong Liang, Guan-Jun Tu, Ya-Xin Han, Da-Wei Guo
In healthy adults, the cervical intervertebral disc mainly comprises the annulus fibrosus and nucleus pulposus. With increasing age, the chemical composition of above tissues deteriorates (Baptiste and Fehlings 2006). Horizontally or vertically cleaving emerges in the posterior part of the disc. Part of the nucleus pulposus is prolapsed through the annulus into the epidural space and results in myelopathy by pinching the spinal cord. Cervical spondylotic myelopathy (CSM) is largely accepted to be a degenerative disease characterized as dysfunction of the cervical spinal cord caused by progressive and chronic compression. Neurological symptoms caused by CSM vary from individual to individual, which can be as mild as hand numbness or be as severe as full tetraplegia. The difference in symptoms is mainly due to the degree of spinal cord compression and the cross-sectional cord deformed shape (Nouri et al. 2015). The influence of mechanical load on the extent of spinal cord injury is presently undisputed.
Related Knowledge Centers
- Fibrocartilage
- Notochord
- Symphysis
- Type I Collagen
- Type II Collagen
- Vertebra
- Ligament
- Vertebral Column
- Joint
- Type II Collagen
- Atlas