Radial bulging of the annulus fibrosus during compression of the intervertebral disc

Klein, Jeremy A.; Hickey, D. S.; Hukins, D.W.L.

doi:10.1016/0021-9290(83)90128-8

Cited by 53 publications

(33 citation statements)

References 12 publications

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“…The findings in compressive loading were characterized by very little surface strain (as also indicated by the measurements of rabbit disc deformations by Klein et al [20]) and very large differences in the measures obtained by the bone-to-bone and disc-only measures. Similar findings were obtained from the model discs, although in the models the magnitude of the surface strain was generally greater.…”

Section: Discussionmentioning

confidence: 65%

Surface strain on human intervertebral discs

Stokes

1987

Journal Orthopaedic Research

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The biomechanical functions of the internal components of the intervertebral disc are not well understood. The surface deformation of 17 human cadaveric lumbar intervertebral discs was studied by photogrammetry by adhering small optical targets to the disc surface and thereby recording the length, bulge, and vertical height of lines on the disc surface representing annular fibers. Discs were studied in pure compression, flexion and extension, axial rotation, and shear. Two definitions of a fiber were investigated: first with the end-points of the fiber on the vertebra ("bone-to-bone" definition), second, where the end points of the fiber were just before the disc vertebra junction (the "disc-only" definition). Measurements were compared with a "constant-volume" physical model and with a mathematical model of the intervertebral disc. Fiber strains were 6% or less under physiological conditions. Comparison of results from the two definitions of fiber length showed greater strains for the disc-only definition in compressive loading. Fiber strains were less than in the constant-volume model of comparable dimensions in compressive loading by a factor of about two, thus suggesting fluid loss or end-plate deformations in the physiologic conditions. The mathematical model indicated that the surface strain for intervertebral discs is very sensitive to the disc-height: diameter ratio and to fluid loss from the disc but is less sensitive to the helix angle of the fibers.

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Section: Discussionmentioning

confidence: 65%

Surface strain on human intervertebral discs

Stokes

1987

Journal Orthopaedic Research

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“…10 % elongation was applied in this series of experiments as it has previously been shown that the OAF region of the IVD is subjected to a strain of between 1 and 13 % (Broberg, 1983;Klein et al, 1983;Ebara et al, 1996;Rannou et al, 2003;Gilbert et al, 2010). Clearly, NP cells are not normally exposed to tensile force, predominantly experiencing compressive and/or hydrostatic pressure in vivo.…”

Section: Discussionmentioning

confidence: 99%

“…The IVD can be divided into three anatomically distinct areas: the outer region that is the annulus fi brosus (AF) which can be further categorised into inner (IAF) and outer (OAF) annulus fi brosus, the central nucleus pulposus (NP), and the cartilaginous endplates (CEP) on the superior and inferior surface. The NP functions to resist compressive loads, whilst the AF, and in particular the OAF, primarily withstands tensional forces applied to the spine (Klein et al, 1983).…”

Section: Introductionmentioning

confidence: 99%

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The effects of cyclic tensile strain on the organisation and expression of cytoskeletal elements in bovine intervertebral disc cells: an in vitro study

Liu

Jia²,

Duance³

et al. 2011

eCM

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It is still relatively unclear how intervertebral disc (IVD) cells sense a mechanical stimulus and convert this signal into a biochemical response. Previous studies demonstrated that the cytoskeletal elements are mechano-responsive in many cell types and may contribute to mechano-signalling pathways. The objective of this study was to determine the response of cells from the outer annulus fi brosus (OAF) to physiological levels of cyclic tensile strain; further, cells from the nucleus pulposus (NP) were also subjected to an identical loading regime to compare biological responses across the IVD populations. We determined whether the organisation and expression of the major cytoskeletal elements and their associated accessory proteins are responsive to mechanical stimulation in these cells, and whether these changes correlated with either a catabolic or anabolic phenotype. OAF and NP cells from immature bovine IVD were seeded onto Flexcell® type I collagen coated plates. Cells were subjected to cyclic tensile strain (10 %, 1 Hz) for 60 minutes. Post-loading, cells were processed for immunofluorescence microscopy, RNA extracted for quantitative PCR and protein extracted for Western blotting analysis. F-actin reorganisation was evident in OAF and NP cells subjected to tensile strain; strain induced β-actin at the transcriptional and translational level in OAF cells. β-tubulin mRNA and protein synthesis increased in strained OAF cells, but vimentin expression was signifi cantly inhibited. Cytoskeletal element organisation and expression were less responsive to strain in NP cells. Tensile strain increased type I collagen and differentially regulated extracellular matrix (ECM)-degrading enzymes' mRNA levels in OAF cells. Strain induced type II collagen transcription in NP cells, but had no effect on the transcription of any other genes analysed. Tensile strain induces different mechano-responses in the organisation and/or expression of cytoskeletal elements and on markers of IVD metabolism. Differential mechano-regulation of anabolic and catabolic ECM components in the OAF and NP populations refl ects their respective mechanical environments in situ.

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“…In the lumbar spine this pattern of orientation is established when the fibres are first laid down prenatally and is retained during ageing [10,11]. A simple analysis suggests that the tilt angle must exceed 54.7 ~ if the fibres are to reinforce the annulus in withstanding the internal pressure exerted by the nucleus pulposus [9]; a more thorough analysis, which takes into account bulging of the annulus and end-plates, suggests that in reality the tilt is likely to be nearer to 65 ~ in the living disc [15]. The regional difference we have observed is difficult to explain.…”

Section: Discussionmentioning

confidence: 99%

Comparison of the structure of human intervertebral discs in the cervical, thoracic and lumbar regions of the spine

et al. 1986

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Posterior and anterior heights, cross-sectional area and shape were measured for all the intervertebral discs in four spines from elderly human cadavers. Disc height was a minimum at the T4-5 level; thoracic discs were less wedge-shaped than those in the cervical and lumbar regions. Cross-sectional area increased from the cranial to caudal extremity; at the L5-S1 level the nucleus pulposus occupied a high proportion of this area. Cervical discs tended to have an elliptical cross-sectional shape, thoracic discs were more circular and lumbar discs tended to have an elliptical cross-section which was flattened or re-entrant posteriorly. This shape distribution was quantified by defining a shape index which had a maximum value of 1 for a circular cross-section. Orientations of the reinforcing fibres in the outer lamellae of the anterior annulus fibrosus were measured from 27 discs by X-ray diffraction. For these measurements, C3-4, T7-8 and L2-3 were chosen as representative of cervical, thoracic and lumbar discs. The fibre tilt, with respect to the axis of the spine, was significantly less in the cervical discs (at 65 degrees) than in the thoracic and lumbar discs (about 70 degrees). These findings are interpreted in relation to differing functional requirements and possible mechanisms of failure in the cervical, thoracic and lumbar regions of the spine in the light of current knowledge on the biomechanics of the intervertebral disc.

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Radial bulging of the annulus fibrosus during compression of the intervertebral disc

Cited by 53 publications

References 12 publications

Surface strain on human intervertebral discs

Surface strain on human intervertebral discs

The effects of cyclic tensile strain on the organisation and expression of cytoskeletal elements in bovine intervertebral disc cells: an in vitro study

Comparison of the structure of human intervertebral discs in the cervical, thoracic and lumbar regions of the spine

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