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At least 973 records · Page 54Linked to original sources
PubMed2002

Degenerated lumbar intervertebral disc. A morphological study.

According to many investigators, lumbar disc herniation is formed by the nucleus pulposus displaced to the vertebral canal through the cracks in the annulus fibrosus as a final result of disc degeneration. Specimens obtained during 187 disc surgeries were studied to identify the morphological nature of various forms of disc herniation, especially protrusion and prolapse. In 29% of cases the herniated part was annulus fibrosus and in 21.5% cases the annulus fibrosus was seriously involved. Simultaneously 308 autopsy specimens were studied. On gross examination the signs of degeneration were advanced in 82, and strongly pronounced in 42. In 15 specimens, aged 40 years or older, fibre bundles were reversed to normal convex orientation producing annulus fibrosus bulge. Microscopic examination showed pronounced myxomatous degeneration within the annulus fibrosus. In these circumstances, we believe that general opinion must be verified, because in some herniations the nuclei pulposus are not involved and herniations are solely prolapses of annulus fibrosus. So, the lumbar intervertebral disc herniation should be classified on the basis of histological examinations as a herniation of nucleus pulposus, herniation of annulus fibrosus or as a mixed type herniation where both disc elements are involved.

Female↗
PubMed1999

Height change caused by creep in intervertebral discs: a sagittal plane model.

Changes in spinal column height have been observed in response to different stress environments including vibration, gravity inversion, space flight, traction, and increased loading. Alterations in spinal height are dependent on body forces, externally applied forces, and properties of the discs and are considered relevant to understanding the normal and pathologic behavior of the spine. This study presents a sagittal plane, viscoelastic model of the spine that quantified the height change behavior of the human spine subjected to axial compressive forces similar to those experienced during quiet standing. The two-dimensional spine model was idealized as a collection of 23 rigid vertebral bodies and 23 deformable intervertebral discs. Time-dependent height losses were modeled using axial compressive creep material properties based on in vitro measurements obtained from the literature. The model demonstrated an instantaneous loss in height of 11.7 mm (0.67% of body height) and a height loss of 19.6 mm (1.1% of body height) at the end of 8 h. Changes in sagittal profile were estimated to contribute to 12% of the overall height loss after 8 hours. Discs in the lumbar region lost the most height, but the contribution of the lumbar region to the total height loss was 32%. The height loss contribution of the thoracic region was higher (57%), presumably because of the increased number of discs contributing to the total height loss in this region. For degenerated discs, the model predicted a similar instantaneous height loss but a 28% greater height loss after 8 h. These results suggest that the majority of spinal height loss is a direct result of intervertebral disc deformation and about two thirds of the total height loss occurs immediately on axial loading of the spine. Based on these findings, diurnal height changes in the spine are predicted to be much greater than previously believed.

Biomechanical Phenomena↗
PubMed2005

Internal strains in healthy and degenerated lumbar intervertebral discs.

STUDY DESIGN: A biomechanical study investigating the intradiscal mechanics of human lumbar intervertebral discs (IVDs). OBJECTIVES: To assess the relationship between nucleus pulposus migration and intradiscal strains as a function of degeneration. SUMMARY OF BACKGROUND DATA: Intradiscal deformation studies have documented the nucleus pulposus migration capabilities during bending but without assessing subsequent intradiscal strains of the anulus fibrosus. Degenerated IVDs show higher anular laxity, hypermobility, and, perhaps, segmental instability. It is unknown if nucleus pulposus migration might be the cause of increased intradiscal anular strains and if such a phenomenon is modulated by IVD degeneration. METHODS: Eighteen healthy and degenerated IVDs were subjected to compression, extension, flexion, and lateral bending. Craniocaudal radiographs at unloaded and loaded steps documented positions of wires placed within and beads glued to the external surface in the mid-transverse plane. Circumferential and radial strains from the anterior, lateral, and posterolateral regions during load were compared between healthy and degenerated IVDs. RESULTS: The nucleus pulposus migrated to the opposite side of bending regardless of bending direction and significantly more in degenerated IVDs. The highest nucleus pulposus migration was observed during lateral bending. Circumferential tensile strains were significantly higher in the posterolateral regions of degenerative IVDs during all loads. Degeneration significantly increased radial tensile and compressive strains during all bending loads. CONCLUSIONS: Increased nucleus pulposus migration in degenerated IVDs may result in increased shifting of the IVD pivot point during bending movements as well as intradiscal anular strains, particularly in the posterolateral anulus. This phenomenon may explain the segmental instability observed in degenerated segments as well as the associated anular tears present in the posterolateral region before IVD failure.

Aged↗
PubMed1997

Could sudden increases in physical activity cause degeneration of intervertebral discs?

Epidemiological studies link high repetitive loading of the lower back with degeneration of intervertebral discs, and experiments on cadaver spines confirm that repetitive mechanical loading can disrupt the lumbar discs in a manner characteristic of "degeneration". But why do living discs not just strengthen in response to this stimulus, as other musculo-skeletal tissues do? Our hypothesis proposes that the low metabolic rate of lumbar discs (the largest avascular structures in the body) prevents them from keeping pace with adaptive remodelling changes in adjacent tissues, so that large and abrupt increases in a person's level of physical activity may leave the lumbar discs the weak link in a strengthening and heavily loaded spine. Recent laboratory investigations support the hypothesis, but clinical evidence is required to relate recent disc degeneration with recent increases in physical activity, and so test the hypothesis.

Fatigue↗
PubMed1991

Age changes to the anulus fibrosus in human intervertebral discs.

This study deals with age changes in the anulus fibrosus of the lumbar intervertebral discs of human individuals 21-83 years of age. The anular laminas from individuals less than 40 years of age consisted of obliquely orientated collagen fibers exhibiting a pennate arrangement. These fibers were intensely argyrophilic after silver nitrate impregnation. The fibers and surrounding substance appeared light pink after exposure to the periodic-acid-Schiff (PAS) reaction and blue with alcian blue complex. Beginning during middle age and continuing into the eighth decade, there was a progressive degeneration of the laminas. The breakdown of the intact laminas was characterized by the fraying, splitting, and loss of collagen fibers. The newly formed spaces became filled with intense PAS-positive material. In addition, there was a continual deposition of chondroid substance in the anuluses of the aging discs. This phenomenon was not seen in the young disc. These age related changes lead to a loss of integrity to the disc, which may be a factor in disc pathology.

Adult↗