Biomechanics of the Spine
Manoj Ramachandran, Tom Nunn in Basic Orthopaedic Sciences, 2018
In the lumbar region, the facets are oriented at right angles to the transverse plane and at 45° to the frontal plane. This permits flexion, extension and lateral flexion but no rotation. The facets and the discs have a coupled function in load bearing. The disc is loaded in flexion and the facets take more than 30% of the load in hyperextension. Spinal ligaments are static stabilizers of the spine. All spinal ligaments except the ligamentum flavum have high collagen content, and this limits their extensibility during spinal motion. The ligamentum flavum primarily attaches to the posterior arches of adjacent vertebrae. It is rich in elastin content and hence contracts in extension and expands in flexion. This also helps maintain spinal canal dimensions during motion. The ligaments farthest away from the centre of rotation bear the maximum stress and maximally limit the motion. Thus the anterior longitudinal ligament is maximally stressed in extension, the interspinous and supraspinous ligaments in forward flexion and the transverse ligaments in lateral flexion. The range of flexion gradually increases in the lumbar motion segments and reaches 20° at L5–S1. Lateral flexion is limited to about 30° in the lumbar spine. Lateral rotation is 20° in the upper lumbar spine and increases to 50° in the lumbosacral junction.
Neuroanatomy: Age-related changes
Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor in Essentials of Geriatric Neuroanesthesia, 2019
The segmental instability due to disc degeneration increases the load on the facet joints, leading to their subluxation and cartilage degradation. Spinal canal stenosis may be caused by facet hypertrophy, osteophyte formation, and apophyseal malalignment. Degenerative spondylolisthesis may occur due to destabilization of the joint. The ligaments surrounding the spine become increasingly weak due to chemical and macroscopic changes with age. The degeneration of ligamentum flavum leads to its increased thickness and bulging. All these factors further contribute to spinal stenosis, and if present in the cervical spine, may progress to myelopathy (27).
Spinal Cord Disease
Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw in Hankey's Clinical Neurology, 2020
Nondegenerative process: Congenital central spinal stenosis.Hypertrophic ligamentum flavum.Posterior longitudinal ligament ossification.Epidural lipomatosis.
Bilateral laminotomy through a unilateral approach (minimally invasive) versus open laminectomy for lumbar spinal stenosis
Published in British Journal of Neurosurgery, 2021
Jack Horan, Mohammed Ben Husien, Ciaran Bolger
The patient is positioned in the prone position under general anaesthesia. Local anaesthesia and epinephrine are injected into the incision site. An incision over the midline is performed on the side that is more symptomatic. The retractor is then placed. Correct position of the retractor is confirmed by fluoroscopy. The microscope is brought in and the ipsilateral lamina is viewed. An ipsilateral hemilaminectomy is performed using a high-speed drill bit. The spinous process and contralateral lamina are then undercut and drilled, enabling visualization and access to the contralateral side. The ligamentum flavum is identified. It is left in situ during removal of the contralateral bone as it serves to protect the dura during this stage of bone removal. Following the removal of contralateral bone the ligamentum flavum is then removed. When adequate decompression is achieved, the retractors are removed with care and the incision is closed.
Hypertrophic cervical spine pachymeningitis due to sarcoidosis: a case report
Published in Hospital Practice, 2019
Hussam A. Yacoub, P. Mark Li, Joshua A. Bemporad, Dmitry Khaitov, Daniel F. Brown
Given the rapid progression of neurological symptoms and the MRI findings, the patient underwent an urgent C3–7 laminectomy. The spinal processes were resected and the laminae was thinned at the C3–7 level. The laminae at C3–C7 were drilled until eggshell-thin. The spinal canal was exposed and the laminectomy widened until normal dura and ligamentum flavum were seen. The thickened dura was decompressed by peeling away multiple laminations of inflammatory tissue until more normal dura mater was seen. The hypertrophied ligamentum flavum was resected. A fibrous pink-tanned mass was seen to be arising from the spinal dura which was thickened and partially calcified. The softer portion of the mass was initially resected, the thickened dura then cut and, finally, the outer thickened part of the dura was stripped away from the normal dura underneath and sent for pathological analysis. After decompression, the dura became much more pliable and the diameter of the dural sac expanded to normal caliber, and therefore it was not essential to open the dura nor perform a duraplasty in order to relieve the spinal cord compression.
Neuro-urological sequelae of lumbar spinal stenosis
Published in International Journal of Neuroscience, 2018
Jason Gandhi, Janki Shah, Gargi Joshi, Sohrab Vatsia, Andrew DiMatteo, Gunjan Joshi, Noel L. Smith, Sardar Ali Khan
Computed tomography (CT) or magnetic resonance imaging (MRI) can confirm the presence or absence of LSS, exclude differential diagnoses and can pinpoint the exact location of LSS for accurate surgical planning. Different imaging techniques can help visualize morphological alterations such as loss of disc height, disc signal, bulging discs, disc herniation, as well as reactive endplate and bone marrow changes. Increased stress on facet joints and hypertrophic facet and ligamentum flavum all lead to central, lateral or foraminal stenosis [7]. While bony findings like facet arthropathy may be more evident on CT, MRI is preferred for identifying soft tissue lesions in the ligaments and discs [8]. MRI is the imaging modality of choice for the radiological assessment of LSS and makes use of T1- and T2-weighted images. MRI can visualize images from the thecal sac, the intrathecal and intraforaminal nerve roots, and the spinal cord. CT scans can also be readily performed to allow for the precise evaluation of the spinal canal and differentiation between spinal compression caused by discs, ligaments and bony structures. However, a limitation of the CT scan is that intrathecal nerve roots and the spine cannot be adequately distinguished due to similar densities of cerebrospinal fluid. This issue may be avoided by using CT myelography, which uses spiral CT imaging in addition to intrathecal administration of iodine [7]. Studies revealed that MRI had a sensitivity of 87%–96% and a specificity of 68%–75% [2,55].