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.

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.

Mechanical Damage to the Intervertebral Disc Annulus Fibrosus Subjected to Cyclic Tensile Loading

2003 ◽  
Author(s):  
David A. Ryan ◽  
Jeffrey J. MacLean ◽  
James C. Iatridis
Keyword(s):  
Cyclic Loading ◽  
Material Properties ◽  
Annulus Fibrosus ◽  
Permanent Deformation ◽  
Mechanical Damage ◽  
Quantitative Relationship ◽  
Peak Stress ◽  
Tensile Loading ◽  
Number Of Cycles

Damage progression in the circumferential direction of the disc annulus is likely to occur in vivo in response to cyclic loading with associated degradation in tensile material properties, yet this information is not available in the literature. We hypothesize that damage of the annulus will be increased by the number of cycles and magnitude of strain applied to the tissue. Therefore, the objective of this study is to obtain a quantitative relationship between number of cycles and magnitude of tensile strain and damage on the annulus fibrosus. Damage to the annulus is assessed through measurement of permanent deformation (% elongation) and peak stress in the tissue under cyclic loading conditions.

scholarly journals Efficacy of casein derivate CPP-ACP1

2014 ◽  
Vol 62 (3) ◽  
pp. 243-252
Author(s):  
Renata Faria PEREIRA ◽  
Soraya Coelho LEAL
Keyword(s):  
Calcium Phosphate ◽  
Randomized Controlled Trials ◽  
Systematic Reviews ◽  
Amorphous Calcium Phosphate ◽  
Controlled Trials ◽  
Randomized Controlled ◽  
Pubmed Database ◽  
Casein Phosphopeptide

OBJECTIVE: A literature review of systematic reviews and in situ and in vivo randomized controlled trials was conducted in order to assess the role of casein phosphopeptide - amorphous calcium phosphate in providing caries-preventive effect superior to any intervention or placebo. METHODS: Initially, Pubmed database was searched for systematic reviews. Two systematic reviews were identified, which concluded that the quantity and quality of randomized controlled trials were insufficient to recommend the clinical use of the product. After this, Pubmed database was searched for in situ and in vivo randomized controlled trials that were not included in the reviews identified. In vivo and in situ studies yielded mixed results. RESULTS: In situ studies indicated greater efficacy of casein phosphopeptide - amorphous calcium phosphate in comparison with placebo. Whereas, in vivo studies demonstrated different findings CONCLUSION: Casein phosphopeptide - amorphous calcium phosphate had a performance equivalent to or greater efficacy than placebo; fluoride was more effective than the casein complex; casein phosphopeptide - amorphous calcium phosphate associated with fluoride showed better or equivalent performance to that of placebo. In view of available evidence, it was not possible to generalize the indication of casein phosphopeptide - amorphous calcium phosphate for preventing dental caries. Further studies on the preventive effect and longer treatment applications are recommended.

Apparatus to Determine the Macroscopic and Microscopic Biaxial Swelling Response of the Annulus Fibrosus

2002 ◽  
Author(s):  
Paul Hulme ◽  
Sabina Bruehlmann ◽  
Neil A. Duncan
Keyword(s):  
Annulus Fibrosus ◽  
Biaxial Loading ◽  
Mechanical Response ◽  
Swelling Behaviour ◽  
Vertebral Bodies ◽  
And Control ◽  
Bearing Structure ◽  
Outer Annulus Fibrosus

The intervertebral disc (IVD) is a “hydrostatic load-bearing structure” [1], found between the vertebral bodies of the spine. The IVD is composed of the inner and outer annulus fibrosus and a gelatinous center, the nucleus pulposus. Fluid is the largest component of the IVD. Swelling affects the macroscopic mechanical response of the tissue, as well as the microscopic nutrient and solute transport to the cells of the IVD. Previous studies describing the macroscopic swelling behaviour of the annulus fibrosus have been uniaxial in nature [2,3]. However, the behaviour of the annulus is markedly affected by its geometry [3]. By examining a biaxial section of annulus fibrosus with a portion of the bone attachment present, the structure of the annular test section will be maintained and by inference so should its function [4]. Therefore, the objective of this study was to develop an apparatus to investigate simultaneously both the macroscopic and microscopic swelling behaviour of the annulus fibrosus subjected to realistic biaxial loading. The biaxial loading device should maintain the annulus fibrosus in vivo geometry and environment, monitor stress and control tissue strain, while positioning the tissue in a manner that allows for in situ visualization of the cells.

In Vitro and In Vivo Validation Tests for Total Artificial Heart

1994 ◽  
Vol 18 (1) ◽  
pp. 54-72 ◽  
Author(s):  
Yukihiko Orime ◽  
Setsuo Takatani ◽  
Kimitaka Tasai ◽  
Yasuhisa Ohara ◽  
Kozo Naito ◽  
...  
Keyword(s):  
Artificial Heart ◽  
Total Artificial Heart ◽  
Validation Tests ◽  
In Vivo Validation

In vitro and in vivo polysaccharides assembly: ultrastructural and cytochemical study of growing plant cell wall components.

1978 ◽  
Vol 36 (2) ◽  
pp. 434-435
Author(s):  
D. Reis ◽  
B. Vian ◽  
J. C. Roland
Keyword(s):  
Cell Wall ◽  
Self Assembly ◽  
Plant Cell Wall ◽  
Higher Plants ◽  
Three Dimensional ◽  
Cytochemical Study ◽  
Wall Components

Wall morphogenesis in higher plants is a problem still open to controversy. Until now the possibility of a transmembrane control and the involvement of microtubules were mostly envisaged. Self-assembly processes have been observed in the case of walls of Chlamydomonas and bacteria. Spontaneous gelling interactions between xanthan and galactomannan from Ceratonia have been analyzed very recently. The present work provides indications that some processes of spontaneous aggregation could occur in higher plants during the formation and expansion of cell wall.Observations were performed on hypocotyl of mung bean (Phaseolus aureus) for which growth characteristics and wall composition have been previously defined.In situ, the walls of actively growing cells (primary walls) show an ordered three-dimensional organization (fig. 1). The wall is typically polylamellate with multifibrillar layers alternately transverse and longitudinal. Between these layers intermediate strata exist in which the orientation of microfibrils progressively rotates. Thus a progressive change in the morphogenetic activity occurs.

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