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Results for “Intervertebral Disc”

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At least 595 records · Page 33Linked to original sources
PubMed2001

Electrochemical measurement of transport into scoliotic intervertebral discs in vivo using nitrous oxide as a tracer.

STUDY DESIGN: An in vivo study measuring nitrous oxide concentrations in scoliotic intervertebral discs during surgery. OBJECTIVES: To determine pathways for nutrient transport into scoliotic human discs in vivo. SUMMARY OF BACKGROUND DATA: The intervertebral disc is the largest avascular structure in the body. Disc cells in the nucleus rely on the blood supply from the vertebral bodies for supply of nutrients and removal of waste. Loss of nutrient supply is thought to lead to disc degeneration, but solute transport has not been measured in vivo in humans. METHODS: We measured solute transport into the disc using N2O as a tracer, in 19 human discs from five patients with neuromuscular scoliosis (6-19 years of age) during surgery for correction of scoliotic deformities. During anesthesia N2O diffuses into the disc at a rate governed by effective permeability of the vertebral body-disc interface. Intradiscal N2O concentrations were measured amperometrically using silver needle microelectrodes, which were inserted into the discs once they were exposed by an anterior approach. RESULTS: For all spines N2O concentrations were very low in the disc at the curve apex (6% those expected from unimpeded diffusion) and, although still low, were significantly higher 2 discs below or above the apex. CONCLUSIONS: Because flux into the apical disc is most restricted, the decrease in solute transport is possibly induced by changes in mechanical stress on the disc; microfocal radiographs of a scoliotic spine suggest that increased endplate calcification could be partly responsible for limiting solute diffusion.

Adolescent↗
PubMed2003

The dorsal portion of the lumbar intervertebral disc is innervated primarily by small peptide-containing dorsal root ganglion neurons in rats.

The intervertebral discs are innervated by the dorsal root ganglion (DRG) neurons. In the present study, we applied Fluoro-Gold (FG) to the dorsal portion of the L5-L6 intervertebral disc to label DRG neurons retrogradely, and then examined whether FG-labeled neurons were substance P (SP)-immunoreactive or isolectin B4 (IB4)-binding. Of the FG-labeled neurons, 44.0% were immunoreactive for SP, whereas only 0.6% were reactive for IB4. The rate of SP-immunoreactive neurons was significantly higher than that of IB4-binding neurons (P<0.001), suggesting that under physiological conditions the dorsal portion of the lumbar disc is mainly innervated by peptide-containing neurons.

Animals↗
PubMed2006

Role of endplates in contributing to compression behaviors of motion segments and intervertebral discs.

The purpose of this study was to gain an improved understanding of the mechanical behavior of the intervertebral disc in the presence and absence of the vertebral endplates. Mechanical behaviors of rat caudal motion segments, vertebrae and isolated disc explants under two different permeability conditions were investigated and viscoelastic behaviors were evaluated using a stretched-exponential function to describe creep and recovery behaviors. The results demonstrated that both vertebrae and discs underwent significant deformations in the motion segment even under relatively low-loading conditions. Secondly, disruption of the collagenous network had minimal impact on equilibrium deformations of disc explants as compared to disc deformations occurring in the motion segments provided that vertebral deformations were accounted for; however, differences in endplate permeability conditions had a significant effect on viscoelastic behaviors. Creep occurred more quickly than recovery for motion segment and explant specimens. In addition, disc explants and motion segments both exhibited non-recoverable deformations under axial compression under low- and high-loading conditions. Results have important implications for interpreting the role of vertebral endplates in contributing to disc mechanical behaviors and direct application to mechanobiology studies involving external loading to rodent tail intervertebral discs.

Animals↗
PubMed2001

Intervertebral disc herniation: studies on a porcine model exposed to highly repetitive flexion/extension motion with compressive force.

OBJECTIVE: To determine whether repeated motion with low magnitude joint forces, and flexion/extension moments consistently produce herniation in a non-degenerated, controlled porcine spine motion segment. DESIGN: Combined loading (flexion/extension motions and compressive forces) was applied to in vitro porcine functional spinal units. Biomechanical and radiographic characteristics were documented. BACKGROUND: While most studies performed in vitro have examined uniaxial or fixed position loading to older specimens, there have been few studies that have examined whether 'healthy' intervertebral discs can be injured by low magnitude repeated combined loading. METHODS: Porcine cervical spine motion segments (C3-C4) were mounted in a custom jig which applied axial compressive loads with pure flexion/extension moments. Dynamic testing was conducted to a maximum of 86400 bending cycles at a rate of 1 Hz with simultaneous torques, angular rotations, axial deformations recorded for the duration of the test. RESULTS: Herniation (posterior and posterior-lateral regions of the annulus) occurred with relatively modest joint compression but with highly repetitive flexion/extension moments. Increased magnitudes of axial compressive force resulted in more frequent and more severe disc injuries. CONCLUSIONS: The results support the notion that intervertebral disc herniation may be more linked to repeated flexion extension motions than applied joint compression, at least with younger, non-degenerated specimens. Relevance. While intervertebral disc herniations are observed clinically, consistent reproduction of this injury in the laboratory has been elusive. This study was designed to examine the biomechanical response and failure mechanics of spine motion segments to highly repetitive low magnitude complex loading.

Animals↗
PubMedDate not supplied

Computed tomography of the normal lumbosacral intervertebral disc in 22 dogs.

Computed tomography of the lumbosacral spine was performed on 22 purpose-bred, medium-sized hound dogs between 1 and 6 years of age. Images were evaluated to determine the degree of disc bulge. All dogs were neurologically normal. Dogs were imaged in dorsal recumbency with the pelvic limbs variably extended. Sagittal reconstructions were made from transverse images. The mean (+/-SD) width of the mid-portion of the L7-S1 intervertebral disc was 0.5 +/- 0.07 cm (range 0.33-0.62 cm). All L7-S1 intervertebral discs were dorsally convex, with the mean bulge measuring 0.25 +/- 0.07 cm (range 0.17-0.50 cm). The height of the vertebral canal at L7-S1 was 0.91 +/- 0.11 cm (range 0.68-1.15 cm). The mean percentage of the vertebral canal occupied by the bulge was 26.89 +/- 5.05% (range 20.74-43.08%). Mild bulging of the L7-S1 intervertebral disc can be present without associated neuropathy in medium-sized dogs.

Animals↗
PubMed2003

ISSLS prize winner: The innervation of the intervertebral disc: a quantitative analysis.

OBJECTIVE: The first quantitative analysis of the innervation of the lumbar intervertebral disc is presented. METHODS: A sheep model was used allowing evaluation of the whole motion segment. Four sheep spines were used. One was processed for PGP 9.5 immunofluorescence and three were processed for PGP 9.5 immunoperoxidase histochemistry. A count was made of the densities of innervation of the endplate and anulus, and these were compared. RESULTS: There is no significant difference between endplate and anulus innervation densities. The endplate innervation is concentrated centrally adjoining the nucleus. The richest area of innervation is in the perianular connective tissue. DISCUSSION: The lumbar intervertebral disc has a meager innervation. This is concentrated in the perianular connective tissue and the central endplate. Although receptor threshold is more closely related to nociceptive function than innervation density, these findings have important implications for any treatment of discogenic pain.

Animals↗
PubMed2005

Alteration of gene expression in intervertebral disc degeneration of passive cigarette- smoking rats: separate quantitation in separated nucleus pulposus and annulus fibrosus.

OBJECTIVE: We constructed a passive cigarette-smoking model with rats to investigate the molecular mechanism of intervertebral disc degeneration, and found by gene expression analysis that passive cigarette smoking stimulated the stress-responsive signal pathway and inhibited the apoptotic pathway. In this study, to clarify that these changes were derived from either nucleus pulposus (NP) or annulus fibrosus (AF), we separately collected NP and AF and quantitatively analyzed gene expression. METHODS: Total RNA was extracted from NP and AF of the lumbar intervertebral discs from rats which were kept in a smoking box for 4 and 8 weeks. Gene expression was measured by real-time PCR of cDNA synthesized from the total RNA. RESULTS: Stress-responsive protein, heat shock protein 70, was expressed similarly in NP and AF, and was upregulated to the same degree after 8 weeks of passive cigarette smoking. The protein tyrosine phosphatase gene was expressed more strongly in AF than in NP, and was upregulated after 8 weeks of smoking in both tissue parts. The type II collagen and aggrecan genes were predominantly expressed in AF and NP, respectively. CONCLUSION: These results indicate that passive cigarette smoking stimulates both NP and AF, and induces the stress-responsible genes such as heat shock protein 70 and protein tyrosine phosphatase in both.

Aggrecans↗
PubMed1998

[The relationship of facet orientation to intervertebral disc protrusion and lateral recess stenosis in lower lumbar spine].

OBJECTIVE: To investigate the relationship of facet orientation to intervertebral disc protrusion and lateral recess stenosis in lower lumbar spine. METHOD: The relationship between facet geometry (joint angle and tropism) and disc protrusion, lateral recess stenosis was investigated with computer tomography (CT) at the vertebral levels L(3 - 4), L(4 - 5), and L(5) - S(1). 772 facet joint angles (386 lower lumbar levels of 136 patients) were measured on coronal CT scans by transverse inter-facet angle (TIFA). RESULT: There was no statistically significant relationship between facet joint asymmetry and disc protrusion (P > 0.05). Disc protrusion occurred more frequently on side of sagittally oriented facet joint than coronal side (P < 0.01). The patients whose lumbar transverse inter-facet angle less than 20 degrees easily suffered from degenerative lumbar lateral recess stenosis in the elderly. The TIFA in Asian less evident than in European may be the important cause for high incidence of lumbar lateral recess syndrome in Asia. CONCLUSION: Stress on the lower lumbar spine leads to disc protrusion. No association is found between facet joint asymmetry and lumbar disc protrusion. The asymmetry of facet joint will influence the direction of intervertebral disc protrusion at level from L(4) - S(1). The patient whose lower lumbar spine inter-facet angle may unlikely suffer from degenerative lumbar lateral recess stenosis.

Adolescent↗
PubMed2003

Internal stress distribution in cervical intervertebral discs: the influence of an artificial cervical joint and simulated anterior interbody fusion.

There is concern that cervical interbody fusion can result in accelerated degenerative changes occurring at adjacent spinal levels. The cervical spine clearly evolved to be mobile. It would seem to be desirable for spinal surgeons to have an alternative to fusion, and spinal arthroplasty is an appealing concept. The Bristol Disc is a mechanical device comprising two articulating components that result in motion with 6 df. It has been shown to have favorable kinematics when compared with intact and fused cadaveric spines. The current study attempts to record changes in the distribution of stresses within cervical intervertebral discs adjacent to the artificial disc or a simulated fusion. The technique used to measure intradiscal stress distributions is based on earlier work by McNally and Adams on lumbar intervertebral discs. The study generated stress profiles through cervical intervertebral discs statically loaded in four different postures in addition to recording changes in intradiscal pressure within both the nucleus and the annulus during flexion. Similar stress profiles were recorded from intact specimens and those with the artificial joint inserted. The artificial joint resulted in reduced stresses in the annulus compared with spines with a simulated fusion. The study demonstrates how different testing conditions can result in researchers being confronted with paradoxical data, and the simulation of muscle forces is recommended.

Adult↗
PubMed2001

In vivo macrophage recruitment by murine intervertebral disc cells.

SUMMARY: An in vivo murine experiment was conducted to measure the capacities of viable intervertebral disc cells to recruit inflammatory cells. The objective was to determine whether compounds secreted from viable cells induce inflammation or whether inflammation in disc herniation simply requires exposure to structural cell or matrix components. Three tissue preparations were inserted into the right lower peritoneal cavity of male mice: tissue with viable annulus fibrosus and nucleus pulposus cells, tissue with viable annulus fibrosus cells, or devitalized annulus fibrosus and nucleus pulposus tissue. Controls included sham-operated and nonoperated groups. Mice were killed 1, 2, or 7 days after surgery. Macrophage recruitment occurred after exposure to viable disc tissue but not after exposure to devitalized disc components; recruitment increased over time. Viable disc cells play a role in the etiology of inflammation in disc herniation.

Animals↗
PubMed1996

Migration of the nucleus pulposus within the intervertebral disc during flexion and extension of the spine.

STUDY DESIGN: Magnetic resonance images were obtained of the lumbar spines of three volunteers in neutral, flexed, and extended postures. OBJECTIVES: To measure migration of the nucleus pulposus within the intervertebral disc during flexion and extension of the spine in living people. SUMMARY OF BACKGROUND DATA: Results of experiments on bisected cadaveric spines have indicated that the nucleus migrates posteriorly during flexion and anteriorly during extension in nondegenerate discs. Degenerate discs may have faults or fissures that result in abnormal motion of the nucleus. METHODS: Proton density weighted, sagittal, magnetic resonance images were obtained from the lumbar spines of three volunteers. Measurements of the positions of the anterior and posterior margins of the nucleus and of flexion and extension angles were made on tracings of the images corresponding to neutral, flexed, and extended postures. RESULTS: The observed frequency (22 of 24 measurements) at which the margins of the nucleus migrated in the directions predicted by results of cadaveric studies was significantly greater than the frequency that would be expected by chance (P < 0.001). The two exceptions may be a result of disc degeneration. There was a significant (P < 0.05) linear correlation between the migration of the anterior margin and the flexion-extension angle and a highly significant (P < 0.001) correlation for the posterior margin and the flexion-extension angle. CONCLUSIONS: Flexion of an intervertebral disc in a living person tends to be accompanied by posteriorly directed migration of the nucleus pulposus within the disc. Extension tends to be accompanied by an anteriorly directed migration.

Adolescent↗
PubMedDate not supplied

Roentgenographic measurement of lumbar intervertebral disc height.

The influences of differences in both intervertebral motion segment orientations and in reader judgments on measurements of the apparent intervertebral disc heights in lateral roentgenographs of the lumbar spine were examined. Forty-nine roentgenographs were obtained of nine discs that were titled laterally up to +/- 10 degrees, and rotated longitudinally up to +/- 20 degrees. Three orthopaedic surgeons and three radiologists measured disc heights from five of these roentgenographs, all using the same measurement method. The differences in apparent height that resulted from the orientation changes and differences in judgments among the six readers were considerable, usually of the order of one half of the nominal disc height. The results show that, while roentgenographic measurements can be used to estimate disc height, accurate measurements cannot readily be made from routine roentgenographs, and the interpretation should always be cautious.

Adult↗
PubMed1986

The effect of posture on diffusion into lumbar intervertebral discs.

The diffusion of small solutes into the intervertebral discs of cadaveric lumbar motion segments was measured using a radioactive tracer technique. The motion segments were wedged and loaded to simulate erect posture and flexed sitting postures. The results show that erect posture favours diffusion into the anterior half of the disc compared to the posterior half. Flexed posture, by deforming the annulus fibrosus, reverses this imbalance.

Adolescent↗
PubMedDate not supplied

MRI analysis of lumbar intervertebral disc height in young and older populations.

Measurements of length and section area on MR images are made conventionally by the manipulation of a tracker ball to move a cursor to define end points or delineate boundaries. This operator-dependent method lacks the objectivity that computer-based image analysis techniques, such as edge-detection algorithms, can give. We describe an image analysis routine, based on earlier work by Vincent and Soille using algorithms of mathematical morphology, for automatically extracting the boundary of lumbar intervertebral discs on MR images. This is applied to the automatic measurement of the maximum disc space height and section area of non-degenerate intervertebral discs on MR images obtained for healthy male subjects of two distinct age ranges, ie, twenty 20- to 30-year-olds and twenty 50- to 60-year-olds. Throughout the levels L1 to L4, intervertebral disc height is found to be significantly greater (P = .0003 to .0161) in the older than in the younger age group. The data support a model of the spine in which the disc adopts a more concave form as a result of microfracturing of the end plates during adult life.

Adult↗
PubMed2000

The micromechanical environment of intervertebral disc cells: effect of matrix anisotropy and cell geometry predicted by a linear model.

Cells of the intervertebral disc exhibit spatial variations in phenotype and morphology that may be related to differences in their local mechanical environments. In this study, the stresses, strains, and dilatations in and around cells of the intervertebral disc were studied with an analytical model of the cell as a mechanical inclusion embedded in a transversely isotropic matrix. In response to tensile loading of the matrix, the local mechanical environment of the cell differed among the anatomic regions of the disc and was strongly influenced by changes in both matrix anisotropy and parameters of cell geometry. The results of this study suggest that the local cellular mechanical environment may play a role in determining both cell morphology in situ and the inhomogeneous response to mechanical loading observed in cells of the disc.

Animals↗
PubMed1991

A hyperelastic and almost incompressible material model as an approach to intervertebral disc analysis.

The literature contains many references to intervertebral disc analysis using experimental techniques which represent a basis for analytical and numerical approaches. The scatter of experimental results may be one reason for difficulties in interpretation. Apart from analytical approaches, which often seem inadequate to deal with the peculiar complexities of the problem, numerical techniques are reliable and can lead to significant results. In this work, a formulation based on the finite element method is described, adopting a nonlinear model with hyperelastic material configuration. Particular attention is paid to modelling the material constituting the nucleus, involving incompressibility characteristics and avoiding simulation techniques. This approach allows the mechanical behavior of the real configuration of the disc to be investigated and also provides a reliable analysis of disc degeneration phenomena. The theoretical and operational aspects of the formulation are reported. The results obtained are compared with responses from various numerical and experimental data.

Animals↗