Pressure distribution under an intervertebral disc—An experimental study

Ranu, Harcharan Singh; Denton, Robert A.; King, Albert I.

doi:10.1016/0021-9290(79)90166-0

Cited by 32 publications

(12 citation statements)

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“…This is attributed to the disc design, wherein the annulus contains the NP. This dependency of E on p i , and hence on F and the disc annulus stress state represented by σ z was also reported by Shirazi-Adl [14] and Ranu [17,18], based on the experimental and finite element analysis of the annulus. The following procedure is followed to determine the disc deformation in response to compressive load.…”

Section: Mechanism and Computation Of Disc Deformationsupporting

confidence: 82%

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The optimal structural design of the human spinal intervertebral disc

Ghista¹,

Fan²,

Sridhar³

et al. 2007

Int. J. D&N

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The intervertebral disc (IVD) acts as a shock-absorbing unit and effectively contains its lateral and axial deformations while providing the necessary flexibility to the spine. These attributes are due to the stress-stiffening material (elastic modulus) property of the annulus, caused by the pressure developed in the nucleus pulposus (NP). Hence, one of the biomechanical roles of the NP in the IVD is to stress the annulus while the IVD is loaded. In this paper, a closed-form solution of the IVD (with NP, i.e. a healthy IVD, and without NP, i.e. a nucleotomized IVD) under compressive loading is developed. Based on the analysis, it is observed that the deformations of the IVD do not increase in proportion to the load. Rather, the rate of increase in deformation decreases as the load increases. This is a key optimal feature because it means that deformations are contained and therefore stability is maintained. Further, it is shown that the nucleotomized IVD deforms more than the healthy IVD. This means that the nucleotomized IVD will have higher chances of collapse than the healthy IVD for the same level of loading. This result is a contra-indication for nucleotomy. Our proposal is to place a biocompatible gel-filled balloon to simulate the beneficial effects of the NP.

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Section: Mechanism and Computation Of Disc Deformationsupporting

confidence: 82%

“…From eqns (18) and (12c), by equating the expressions for F, we get the radial deformation at the inner surface as…”

Section: Stress Analysis Of the Healthy Disc Under Compressionmentioning

confidence: 99%

The optimal structural design of the human spinal intervertebral disc

Ghista¹,

Fan²,

Sridhar³

et al. 2007

Int. J. D&N

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“…The initial distribution of the vertical stress appeared fairly uniform with the exclusion of the outer rim of the endplate and vertebra. This ®nding corresponds with the data provided by Horst and Brinckmann [14], but contrasts with the data presented by Ranu et al [15]. The latter may be due to the placement of the transducers in the study by Ranu et al which was close to the outer rim of the vertebra.…”

Section: Discussionsupporting

confidence: 59%

“…Under eccentric loading the stress in the anulus increased in the degenerated specimens. Ranu et al [15,16] tested specimens at higher compression forces after placing pressure transducers within 10 mm from the anterior and lateral edges of the vertebra. They report linear relations between compression force and pressure with marked inhomogeneities of the distribution.…”

Section: Introductionmentioning

confidence: 99%

Stress distribution changes in bovine vertebrae just below the endplate after sustained loading

Dieën¹,

Kingma²,

Meijer³

et al. 2001

Clinical Biomechanics

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Objective. To describe the pattern of stress distribution in the vertebral body just behind the endplate, and to document its changes due to sustained loading.Methods. Twelve fresh bovine coccygeal motion segments were dissected and tested. Each specimen was axially loaded with a sustained compressive force of 50% of its estimated compressive strength. Before loading, after 1.5 h and after 3 h of loading, the distribution of the axial pressure under the bottom vertebra (i.e., just below its top endplate) was recorded at three force levels (25%, 37.5% and 50% of the estimated compressive strength), using pressure-sensitive ®lm.Results. Stress distribution over the endplate was found to be fairly uniform. At low compression forces, the stress was the highest centrally. With increased compression and after sustained compression the uniformity improved through a signi®cant redistribution of stress to the periphery. No stress peaks were found to occur after sustained loading.Conclusion. Stress peaks after sustained loading cannot explain the occurrence of endplate fractures in sustained cyclic compression in non-degenerated discs. Competing explanations, such as creep, and fatigue failure, would appear more likely candidates. RelevanceIt has been hypothesised that compression induced fractures of the lumbar vertebral endplate constitute an important etiological factor for low back pain. Competing theories exist on the fracture mechanism in sustained loading and these would have di erent implications with respect to prevention. The present study evaluated one of these theories. Ó

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“…Mathematical models of the intervertebral disc structure have been used to predict the distribution of stress and strain in response to external loadings and deformation (3,5,6,21,22,33,34). These theoretical models, combined with measurements of intradiscal pressure (25,26,29), confirm that the intervertebral disc is a structure that supports compressive load by generation of high pressure within the radially confined nucleus pulposus. The annulus fibrosus contains fibers that are aligned at approximately 57" to the axial direction (13).…”

mentioning

confidence: 99%

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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Pressure distribution under an intervertebral disc—An experimental study

Cited by 32 publications

References 0 publications

The optimal structural design of the human spinal intervertebral disc

The optimal structural design of the human spinal intervertebral disc

Stress distribution changes in bovine vertebrae just below the endplate after sustained loading

Surface strain on human intervertebral discs

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