Mapping of Intervertebral Disk Annulus Fibrosus Compressive Properties Is Sensitive to Specimen Boundary Conditions

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Sarah E. Duclos ◽  
Arthur J. Michalek
Keyword(s):  
Residual Strain ◽  
Annulus Fibrosus ◽  
Intervertebral Disk ◽  
Transverse Plane ◽  
The State ◽  
Compressive Properties ◽  
Spatial Homogeneity ◽  
Matrix Deposition ◽  
Residual Strains

Predicting the mechanical behavior of the intervertebral disk (IVD) in health and in disease requires accurate spatial mapping of its compressive mechanical properties. Previous studies confirmed that residual strains in the annulus fibrosus (AF) of the IVD, which result from nonuniform extracellular matrix deposition in response to in vivo loads, vary by anatomical regions (anterior, posterior, and lateral) and zones (inner, middle, and outer). We hypothesized that as the AF is composed of a nonlinear, anisotropic, viscoelastic material, the state of residual strain in the transverse plane would influence the apparent values of axial compressive properties. To test this hypothesis, axial creep indentation tests were performed, using a 1.6 mm spherical probe, at nine different anatomical locations on bovine caudal AFs in both the intact (residual strain present) and strain relieved states. The results showed a shift toward increased spatial homogeneity in all measured parameters, particularly instantaneous strain. This shift was not observed in control AFs, which were tested twice in the intact state. Our results confirm that time-dependent axial compressive properties of the AF are sensitive to the state of residual strain in the transverse plane, to a degree that is likely to affect whole disk behavior.

A Comparison of Uniaxial and Biaxial Mechanical Properties of the Annulus Fibrosus: A Porcine Model

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Diane E. Gregory ◽  
Jack P. Callaghan
Keyword(s):  
Mechanical Properties ◽  
Annulus Fibrosus ◽  
Axial Direction ◽  
Stretch Ratio ◽  
Intervertebral Disk ◽  
Circumferential Direction ◽  
Biaxial Tests ◽  
Maximal Stress ◽  
Biaxial Mechanical Properties

The annulus fibrosus of the intervertebral disk experiences multidirectional tension in vivo, yet the majority of mechanical property testing has been uniaxial. Therefore, our understanding of how this complex multilayered tissue responds to loading may be deficient. This study aimed to determine the mechanical properties of porcine annular samples under uniaxial and biaxial tensile loading. Two-layer annulus samples were isolated from porcine disks from four locations: anterior superficial, anterior deep, posterior superficial, and posterior deep. These tissues were then subjected to three deformation conditions each to a maximal stretch ratio of 1.23: uniaxial, constrained uniaxial, and biaxial. Uniaxial deformation was applied in the circumferential direction, while biaxial deformation was applied simultaneously in the circumferential and compressive directions. Constrained uniaxial consisted of a stretch ratio of 1.23 in the circumferential direction while holding the tissue stationary in the axial direction. The maximal stress and stress-stretch ratio (S-S) moduli determined from the biaxial tests were significantly higher than those observed during both the uniaxial tests (maximal stress, 97.1% higher during biaxial; p=0.002; S-S moduli, 117.9% higher during biaxial; p=0.0004) and the constrained uniaxial tests (maximal stress, 46.8% higher during biaxial; S-S moduli, 82.9% higher during biaxial). These findings suggest that the annulus is subjected to higher stresses in vivo when under multidirectional tension.

scholarly journals Effects of elastin haploinsufficiency on the mechanical behavior of mouse arteries

2005 ◽  
Vol 289 (3) ◽  
pp. H1209-H1217 ◽  
Author(s):  
Jessica E. Wagenseil ◽  
Nandan L. Nerurkar ◽  
Russell H. Knutsen ◽  
Ruth J. Okamoto ◽  
Dean Y. Li ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Residual Strain ◽  
Arterial Compliance ◽  
Circumferential Stress ◽  
Ascending Aorta ◽  
Longitudinal Stress ◽  
Wild Type ◽  
Residual Strains ◽  
Longitudinal Stretch

Supravalvular aortic stenosis (SVAS) is associated with decreased elastin and altered arterial mechanics. Mice with a single deletion in the elastin gene (ELN+/−) are models for SVAS. Previous studies have shown that elastin haploinsufficiency in these mice causes hypertension, decreased arterial compliance, and changes in arterial wall structure. Despite these differences, ELN+/− mice have a normal life span, suggesting that the arteries remodel and adapt to the decreased amount of elastin. To test this hypothesis, we performed in vitro mechanical tests on abdominal aorta, ascending aorta, and left common carotid artery from ELN+/− and wild-type (C57BL/6J) mice. We compared the circumferential and longitudinal stress-stretch relationships and residual strains. The circumferential stress-stretch relationship is similar between genotypes and changes <3% with longitudinal stretch at lengths within 10% of the in vivo value. At mean arterial pressure, the circumferential stress in the ascending aorta is higher in ELN+/− than in wild type. Although arterial pressures are higher, the increased number of elastic lamellae in ELN+/− arteries results in similar tension/lamellae compared with wild type. The longitudinal stress-stretch relationship is similar between genotypes for most arteries. Compared with wild type, the in vivo longitudinal stretch is lower in ELN+/− abdominal and carotid arteries and the circumferential residual strain is higher in ELN+/− ascending aorta. The increased circumferential residual strain brings the transmural strain distribution in ELN+/− ascending aorta close to wild-type values. The mechanical behavior of ELN+/− arteries is likely due to the reduced elastin content combined with adaptive remodeling during vascular development.

scholarly journals Residual strains estimation in the annulus fibrosus through digital image correlation

2021 ◽  
Author(s):  
Gilles Dusfour ◽  
Dominique Ambard ◽  
Patrick Cañadas ◽  
Simon Lefloch
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Annulus Fibrosus ◽  
Ex Vivo ◽  
Image Correlation ◽  
Radial Incision ◽  
Deformation State ◽  
Residual Strains ◽  
The Mean

Up-to-date, back pain is among the most prevalent health issues and generally takes its origins from lesions of the annulus fibrosus (AF). While the AF ex vivo mechanical properties are increasingly well understood, in vivo data are still missing. In particular, very few studies have precisely measured the residual strains within the AF and thus the in vivo deformation state of the AF is still miss-interpreted and miss-evaluated. In this work, we propose an original and robust method for the AF residual strains quantification via digital image correlation technics. Ten pig annulus fibrosus were extracted from adjacent vertebrae followed by a radial incision to release the residual strains. The operations were filmed and then analyzed by a custom digital image correlation software in order to quantify the circumferential, radial and shear residual deformations. Our results show that residual strains are of the same order of magnitude than the in vivo one. The average circumferential strains are in tension on the outer periphery ([3.32; 5.94]%) and in compression on the inner periphery ([−6.4; −1.69]%). The mean radial residual strains are essentially in compression ([−10.4; 2.29]%). Locally, radial and circumferential residual strains can reach really large values up to 40% of compression. The mean shear strains remain very small (−0.04% ± 2.88%). This study also shows that circumferential and radial residual strains evolve linearly along the radius and non-linearly along the angle. We propose a simple model to predict their spatial variations. Our results and methods will allow the quantification of more realistic in vivo strains and stresses within the human intervertebral disc.

Noninvasive In Vivo Determination of Residual Strains and Stresses

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Samir Donmazov ◽  
Senol Piskin ◽  
Kerem Pekkan
Keyword(s):  
Experimental Data ◽  
Residual Stress ◽  
Residual Strain ◽  
Analytical Approach ◽  
Measurement Techniques ◽  
Data Sets ◽  
Residual Strains ◽  
Loading And Unloading

Vascular growth and remodeling during embryonic development are associated with blood flow and pressure induced stress distribution, in which residual strains and stresses play a central role. Residual strains are typically measured by performing in vitro tests on the excised vascular tissue. In this paper, we investigated the possibility of estimating residual strains and stresses using physiological pressure–radius data obtained through in vivo noninvasive measurement techniques, such as optical coherence tomography or ultrasound modalities. This analytical approach first tested with in vitro results using experimental data sets for three different arteries such as rabbit carotid artery, rabbit thoracic artery, and human carotid artery based on Fung’s pseudostrain energy function and Delfino’s exponential strain energy function (SEF). We also examined residual strains and stresses in the human swine iliac artery using the in vivo experimental ultrasound data sets corresponding to the systolic-to-diastolic region only. This allowed computation of the in vivo residual stress information for loading and unloading states separately. Residual strain parameters as well as the material parameters were successfully computed with high accuracy, where the relative errors are introduced in the range of 0–7.5%. Corresponding residual stress distributions demonstrated global errors all in acceptable ranges. A slight discrepancy was observed in the computed reduced axial force. Results of computations performed based on in vivo experimental data obtained from loading and unloading states of the artery exhibited alterations in material properties and residual strain parameters as well. Emerging noninvasive measurement techniques combined with the present analytical approach can be used to estimate residual strains and stresses in vascular tissues as a precursor for growth estimates. This approach is also validated with a finite element model of a general two-layered artery, where the material remodeling states and residual strain generation are investigated.

scholarly journals Design Requirements for Annulus Fibrosus Repair: Review of Forces, Displacements, and Material Properties of the Intervertebral Disk and a Summary of Candidate Hydrogels for Repair

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Rose G. Long ◽  
Olivia M. Torre ◽  
Warren W. Hom ◽  
Dylan J. Assael ◽  
James C. Iatridis
Keyword(s):  
Material Properties ◽  
Annulus Fibrosus ◽  
Intervertebral Disk ◽  
Screening Tests ◽  
Pubmed Database ◽  
Design Requirements ◽  
Validation Tests ◽  
In Vivo Validation

There is currently a lack of clinically available solutions to restore functionality to the intervertebral disk (IVD) following herniation injury to the annulus fibrosus (AF). Microdiscectomy is a commonly performed surgical procedure to alleviate pain caused by herniation; however, AF defects remain and can lead to accelerated degeneration and painful conditions. Currently available AF closure techniques do not restore mechanical functionality or promote tissue regeneration, and have risk of reherniation. This review determined quantitative design requirements for AF repair materials and summarized currently available hydrogels capable of meeting these design requirements by using a series of systematic PubMed database searches to yield 1500+ papers that were screened and analyzed for relevance to human lumbar in vivo measurements, motion segment behaviors, and tissue level properties. We propose a testing paradigm involving screening tests as well as more involved in situ and in vivo validation tests to efficiently identify promising biomaterials for AF repair. We suggest that successful materials must have high adhesion strength (∼0.2 MPa), match as many AF material properties as possible (e.g., approximately 1 MPa, 0. 3 MPa, and 30 MPa for compressive, shear, and tensile moduli, respectively), and have high tensile failure strain (∼65%) to advance to in situ and in vivo validation tests. While many biomaterials exist for AF repair, few undergo extensive mechanical characterization. A few hydrogels show promise for AF repair since they can match at least one material property of the AF while also adhering to AF tissue and are capable of easy implantation during surgical procedures to warrant additional optimization and validation.

Tocotrienols and Cancer: From the State of the Art to Promising Novel Patents

2019 ◽  
Vol 14 (1) ◽  
pp. 5-18 ◽  
Author(s):  
Fabrizio Fontana ◽  
Michela Raimondi ◽  
Monica Marzagalli ◽  
Roberta M. Moretti ◽  
Marina Montagnani Marelli ◽  
...  
Keyword(s):  
Cancer Prevention ◽  
State Of The Art ◽  
Synergistic Effects ◽  
The State ◽  
Therapeutic Interventions ◽  
Multiple Tumor ◽  
Anti Cancer ◽  
Important Health

Background: Tocotrienols (TTs) are vitamin E derivatives naturally occurring in several plants and vegetable oils. Like Tocopherols (TPs), they comprise four isoforms, α, β, γ and δ, but unlike TPs, they present an unsaturated isoprenoid chain. Recent studies indicate that TTs provide important health benefits, including neuroprotective, anti-inflammatory, anti-oxidant, cholesterol lowering and immunomodulatory effects. Moreover, they have been found to possess unique anti-cancer properties.Objective:The purpose of this review is to present an overview of the state of the art of TTs role in cancer prevention and treatment, as well as to describe recent patents proposing new methods for TTs isolation, chemical modification and use in cancer prevention and/or therapy.Methods:Recent literature and patents focusing on TTs anti-cancer applications have been identified and reviewed, with special regard to their scientific impact and novelty.Results:TTs have demonstrated significant anti-cancer activity in multiple tumor types, both in vitro and in vivo. Furthermore, they have shown synergistic effects when given in combination with standard anti-cancer agents or other anti-tumor natural compounds. Finally, new purification processes and transgenic sources have been designed in order to improve TTs production, and novel TTs formulations and synthetic derivatives have been developed to enhance their solubility and bioavailability.Conclusion:The promising anti-cancer effects shown by TTs in several preclinical studies may open new opportunities for therapeutic interventions in different tumors. Thus, clinical trials aimed at confirming TTs chemopreventive and tumor-suppressing activity, particularly in combination with standard therapies, are urgently needed.

Hybrid Rigid-Deformable Model for Prediction of Neighboring Intervertebral Disk Loads During Flexion Movement After Lumbar Interbody Fusion at L3–4 Level

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Tien Tuan Dao
Keyword(s):  
Lumbar Spine ◽  
Computational Models ◽  
Interbody Fusion ◽  
Clinical Decision ◽  
Intervertebral Disk ◽  
Design Guideline ◽  
Spinal Loads ◽  
Stress Changes ◽  
Stress Behaviors

Knowledge of spinal loads in neighboring disks after interbody fusion plays an important role in the clinical decision of this treatment as well as in the elucidation of its effect. However, controversial findings are still noted in the literature. Moreover, there are no existing models for efficient prediction of intervertebral disk stresses within annulus fibrosus (AF) and nucleus pulposus (NP) regions. In this present study, a new hybrid rigid-deformable modeling workflow was established to quantify the mechanical stress behaviors within AF and NP regions of the L1–2, L2–3, and L4–5 disks after interbody fusion at L3–4 level. The changes in spinal loads were compared with results of the intact model without interbody fusion. The fusion outcomes revealed maximal stress changes (10%) in AF region of L1–2 disk and in NP region of L2–3 disk. The minimal stress change (1%) is noted at the NP region of the L1–2 disk. The validation of simulation outcomes of fused and intact lumbar spine models against those of other computational models and in vivo measurements showed good agreements. Thus, this present study may be used as a novel design guideline for a specific implant and surgical scenario of the lumbar spine disorders.

Sign in / Sign up

Export Citation Format

Share Document