Anisotropic shear behavior of the annulus fibrosus: effect of harvest site and tissue prestrain

Fujita, Yoshi; Wagner, Diane R.; Biviji, A.A.; Duncan, Neil A.; Lotz, Jeffrey C.

doi:10.1016/s1350-4533(00)00053-9

Cited by 64 publications

(57 citation statements)

References 23 publications

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“…Mass density was assumed to be known and constant to obtain this value; this property, however, might change with disc compression and it might not be homogeneous in the annulus. Still, this acoustic shear modulus is similar to the shear modulus measured by mechanical testing in unloaded human annulus fibrosus (32.12 ± 18.4 kPa) [46].…”

Section: Discussionsupporting

confidence: 83%

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Intervertebral disc characterization by shear wave elastography: An in vitro preliminary study

Vergari

Rouch

Dubois

et al. 2014

Proc Inst Mech Eng H

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Science Arts & Métiers (SAM)is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. properties remains a challenge. Ultrasound elastography is a relatively recent measurement technique allowing the evaluation of soft tissue's elastic modulus through the measurement of shear wave speed (SWS). The aim of this study was to determine the feasibility of elastographic measurements in intervertebral disc (IVD). An in-vitro approach was chosen to test the hypothesis that SWS can be used to evaluate IVD mechanical properties and to assess measurement repeatability. Eleven oxtail IVDs were tested in compression to determine their stiffness and apparent elastic modulus at rest and at 400 N. Elastographic measurements were performed in these two conditions and compared to these mechanical parameters. The protocol was repeated six times to determine elastographic measurement repeatability. Average SWS over all samples was 5.3 ± 1.0 m/s, with a repeatability of 7 % at rest and 4.6 % at 400 N; stiffness and apparent elastic modulus were 266.3 ± 70.5 N/mm and 5.4 ± 1.1 MPa at rest, respectively, while at 400 N they were 781.0 ± 153.8 N/mm and 13.2 ± 2.4 MPa. Correlations were found between elastographic measurements and IVD mechanical properties; these preliminary results are promising for further in-vivo application.

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Section: Discussionsupporting

confidence: 83%

“…Still, data showed correlations between SWS in the transverse plane and axial stiffness and apparent elastic modulus in loaded IVD (Table 2). SWS values were expected to increase with the load applied to the IVD, since shear modulus generally increases in loaded soft tissues [46], but the global average remained unchanged at (Table 1).…”

Section: Discussionmentioning

confidence: 99%

Intervertebral disc characterization by shear wave elastography: An in vitro preliminary study

Vergari

Rouch

Dubois

et al. 2014

Proc Inst Mech Eng H

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“…Adjacent lamellae are composed by collagen fiber bundles inclined, with respect to the vertical axis of the spine, with angles varying from ±62°to ±45°. 13 This peculiar structure is responsible for an anisotropic behavior of AF observed in experiments, such as mechanical stiffness, 16,19 hydraulic permeability, 22 water diffusion, 15,27,36 and electrical conductivity. 29 Thus, it is reasonable to hypothesize that the diffusion of solutes within the AF is anisotropic.…”

Section: Introductionmentioning

confidence: 98%

Anisotropic Diffusive Transport in Annulus Fibrosus: Experimental Determination of the Diffusion Tensor by FRAP Technique

Travascio

2007

Ann Biomed Eng

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The annulus fibrosus (AF) of the intervertebral disc (IVD) exhibits a fiber-organized structure which is responsible for anisotropic and inhomogeneous mechanical and transport properties. Due to its particular morphology, nutrient transport within AF is regulated by complex transport kinetics. This work investigates the diffusive transport of a small solute in the posterior and anterior regions of AF since diffusion is the major transport mechanism for low molecular weight nutrients (e.g., oxygen and glucose) in IVD. Diffusion coefficient (D) of fluorescein (332 Da) in bovine coccygeal AF was measured in the three major (axial, circumferential, and radial) directions of the IVD by means of fluorescence recovery after photobleaching (FRAP) technique. It was found that the diffusion coefficient was anisotropic and inhomogeneous. In both anterior and posterior regions, the diffusion coefficient in the radial direction was found to be the lowest. Circumferential and axial diffusion coefficients were not significantly different in both posterior and anterior regions and their values were about 130% and 150% the value of the radial diffusion coefficient, respectively. The values of diffusion coefficients in the anterior region were in general higher than those of corresponding diffusion coefficients in the posterior region. This study represents the first quantitative analysis of anisotropic diffusion transport in AF by means of FRAP technique and provides additional knowledge on understanding the pathways of nutritional supply into IVD.

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“…Some of these studies have tested specimens in the 9th decade or older. 1,3,10,15 In contrast, the present study used specimens younger than 50 years, and hence it is expected that age-based variations are minimal for this relatively narrow sample. From this perspective, the present data can be used as a normative set for investigating the biomechanical properties of young and normal spines.…”

Section: Discussionmentioning

confidence: 87%

Mechanical yield of the lumbar annulus: a possible contributor to instability

Stemper

Baisden

Yoganandan

et al. 2014

SPI

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Object Segmental instability in the lumbar spine can result from a number of mechanisms including intervertebral disc degeneration and facet joint degradation. Under traumatic circumstances, elevated loading may lead to mechanical yield of the annular fibers, which can decrease load-carrying capacity and contribute to instability. The purpose of this study was to quantify the biomechanics of intervertebral annular yield during tensile loading with respect to spinal level and anatomical region within the intervertebral disc. Methods This laboratory-based study incorporated isolated lumbar spine annular specimens from younger and normal or mildly degenerated intervertebral discs. Specimens were quasi-statically distracted to failure in an environmentally controlled chamber. Stress and strain associated with yield and ultimate failure were quantified, as was stiffness in the elastic and postyield regions. Analysis of variance was used to determine statistically significant differences based on lumbar spine level, radial position, and anatomical region of the disc. Results Annular specimens demonstrated a nonlinear response consisting of the following: toe region, linear elastic region, yield point, postyield region, and ultimate failure point. Regional dependency was identified between deep and superficial fibers. Mechanical yield was evident prior to ultimate failure in 98% of the specimens and occurred at approximately 80% and 74% of the stress and strain, respectively, to ultimate failure. Fiber modulus decreased by 34% following yield. Conclusions Data in this study demonstrated that yielding of intervertebral disc fibers occurs relatively early in the mechanical response of the tissues and that stiffness is considerably decreased following yield. Therefore, yielding of annular fibers may result in decreased segmental stability, contributing to accelerated degeneration of bony components and possible idiopathic pain.

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Anisotropic shear behavior of the annulus fibrosus: effect of harvest site and tissue prestrain

Cited by 64 publications

References 23 publications

Intervertebral disc characterization by shear wave elastography: An in vitro preliminary study

Intervertebral disc characterization by shear wave elastography: An in vitro preliminary study

Anisotropic Diffusive Transport in Annulus Fibrosus: Experimental Determination of the Diffusion Tensor by FRAP Technique

Mechanical yield of the lumbar annulus: a possible contributor to instability

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