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Montanari S, Serchi E, Conti A, Barbanti Bròdano G, Stagni R, Cristofolini L. Effect of two-level decompressive procedures on the biomechanics of the lumbo-sacral spine: an ex vivo study. Front Bioeng Biotechnol 2024; 12:1400508. [PMID: 39045539 PMCID: PMC11263119 DOI: 10.3389/fbioe.2024.1400508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Accepted: 06/17/2024] [Indexed: 07/25/2024] Open
Abstract
Hemilaminectomy and laminectomy are decompressive procedures commonly used in case of lumbar spinal stenosis, which involve the removal of the posterior elements of the spine. These procedures may compromise the stability of the spine segment and create critical strains in the intervertebral discs. Thus, this study aimed to investigate if decompressive procedures could alter the biomechanics of the lumbar spine. The focus was on the changes in the range of motion and strain distribution of the discs after two-level hemilaminectomy and laminectomy. Twelve L2-S1 cadaver specimens were prepared and mechanically tested in flexion, extension and both left and right lateral bending, in the intact condition, after a two-level hemilaminectomy on L4 and L5 vertebrae, and a full laminectomy. The range of motion (ROM) of the entire segment was assessed in all the conditions and loading configurations. In addition, Digital Image Correlation was used to measure the strain distribution on the surface of each specimen during the mechanical tests, focusing on the disc between the two decompressed vertebrae and in the two adjacent discs. Hemilaminectomy did not significantly affect the ROM, nor the strain on the discs. Laminectomy significantly increased the ROM in flexion, compared to the intact state. Laminectomy significantly increased the tensile strains on both L3-L4 and L4-L5 disc (p = 0.028 and p = 0.014) in ipsilateral bending, and the compressive strains on L4-L5 intervertebral disc, in both ipsilateral and contralateral bending (p = 0.014 and p = 0.0066), with respect to the intact condition. In conclusion, this study found out that hemilaminectomy did not significantly impact the biomechanics of the lumbar spine. Conversely, after the full laminectomy, flexion significantly increased the range of motion and lateral bending was the most critical configuration for largest principal strain.
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Affiliation(s)
- Sara Montanari
- Department of Industrial Engineering, Alma Mater Studiorum—Università di Bologna, Bologna, Italy
| | - Elena Serchi
- Neurosurgery Unit, IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
| | - Alfredo Conti
- Neurosurgery Unit, IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
- Department of Biomedical and Neuromotor Sciences (DIBINEM), Alma Mater Studiorum—Università di Bologna, Bologna, Italy
| | | | - Rita Stagni
- Department of Electrical, Electronic and Information Engineering “Guglielmo Marconi”, Alma Mater Studiorum—Università di Bologna, Bologna, Italy
| | - Luca Cristofolini
- Department of Industrial Engineering, Alma Mater Studiorum—Università di Bologna, Bologna, Italy
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2
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Buchweitz N, Sun Y, Cisewski Porto S, Kelley J, Niu Y, Wang S, Meng Z, Reitman C, Slate E, Yao H, Wu Y. Regional structure-function relationships of lumbar cartilage endplates. J Biomech 2024; 169:112131. [PMID: 38739987 PMCID: PMC11182561 DOI: 10.1016/j.jbiomech.2024.112131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Revised: 04/17/2024] [Accepted: 05/02/2024] [Indexed: 05/16/2024]
Abstract
Cartilage endplates (CEPs) act as protective mechanical barriers for intervertebral discs (IVDs), yet their heterogeneous structure-function relationships are poorly understood. This study addressed this gap by characterizing and correlating the regional biphasic mechanical properties and biochemical composition of human lumbar CEPs. Samples from central, lateral, anterior, and posterior portions of the disc (n = 8/region) were mechanically tested under confined compression to quantify swelling pressure, equilibrium aggregate modulus, and hydraulic permeability. These properties were correlated with CEP porosity and glycosaminoglycan (s-GAG) content, which were obtained by biochemical assays of the same specimens. Both swelling pressure (142.79 ± 85.89 kPa) and aggregate modulus (1864.10 ± 1240.99 kPa) were found to be regionally dependent (p = 0.0001 and p = 0.0067, respectively) in the CEP and trended lowest in the central location. No significant regional dependence was observed for CEP permeability (1.35 ± 0.97 * 10-16 m4/Ns). Porosity measurements correlated significantly with swelling pressure (r = -0.40, p = 0.0227), aggregate modulus (r = -0.49, p = 0.0046), and permeability (r = 0.36, p = 0.0421), and appeared to be the primary indicator of CEP biphasic mechanical properties. Second harmonic generation microscopy also revealed regional patterns of collagen fiber anchoring, with fibers inserting the CEP perpendicularly in the central region and at off-axial directions in peripheral regions. These results suggest that CEP tissue has regionally dependent mechanical properties which are likely due to the regional variation in porosity and matrix structure. This work advances our understanding of healthy baseline endplate biomechanics and lays a groundwork for further understanding the role of CEPs in IVD degeneration.
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Affiliation(s)
- Nathan Buchweitz
- Department of Bioengineering, Clemson University, Clemson, SC, USA.
| | - Yi Sun
- Department of Orthopaedics, The 2nd Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Sarah Cisewski Porto
- Department of Bioengineering, Clemson University, Clemson, SC, USA; School of Health Sciences, College of Charleston, Charleston, SC, USA.
| | - Joshua Kelley
- Department of Bioengineering, Clemson University, Clemson, SC, USA.
| | - Yipeng Niu
- College of Art and Science, New York University, New York City, NY, USA.
| | - Shangping Wang
- Department of Bioengineering, Clemson University, Clemson, SC, USA.
| | - Zhaoxu Meng
- Department of Mechanical Engineering, Clemson University, Clemson, SC, USA.
| | - Charles Reitman
- Department of Orthopaedics and Physical Medicine, Medical University of South Carolina, Charleston, SC, USA.
| | - Elizabeth Slate
- Department of Statistics, Florida State University, Tallahassee, FL, USA.
| | - Hai Yao
- Department of Bioengineering, Clemson University, Clemson, SC, USA; Department of Orthopaedics and Physical Medicine, Medical University of South Carolina, Charleston, SC, USA.
| | - Yongren Wu
- Department of Bioengineering, Clemson University, Clemson, SC, USA; Department of Orthopaedics and Physical Medicine, Medical University of South Carolina, Charleston, SC, USA.
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3
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Middendorf JM, Barocas VH. An Approach to Quantify Anisotropic Multiaxial Failure of the Annulus Fibrosus. J Biomech Eng 2024; 146:014501. [PMID: 37851527 PMCID: PMC10680983 DOI: 10.1115/1.4063822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 10/12/2023] [Accepted: 10/13/2023] [Indexed: 10/20/2023]
Abstract
Tears in the annulus fibrosus (AF) of the intervertebral disk (IVD) occur due to multiaxial loading on the spine. However, most existing AF failure studies measure uniaxial stress, not the multiaxial stress at failure. Delamination theory, which requires advanced structural knowledge and knowledge about the interactions between the AF fibers and matrix, has historically been used to understand and predict AF failure. Alternatively, a simple method, the Tsai-Hill yield criteria, could describe multiaxial failure of the AF. This yield criteria uses the known tissue fiber orientation and an equation to establish the multiaxial failure stresses that cause failure. This paper presents a method to test the multiaxial failure stress of the AF experimentally and evaluate the potential for the Tsai-Hill model to predict these failure stresses. Porcine AF was cut into a dogbone shape at three distinct angles relative to the primary lamella direction (parallel, transverse, and oblique). Then, each dogbone was pulled to complete rupture. The Cauchy stress in the material's fiber coordinates was calculated. These multiaxial stress parameters were used to optimize the coefficients of the Tsai-Hill yield. The coefficients obtained for the Tsai-Hill model vary by an order of magnitude between the fiber and transverse directions, and these coefficients provide a good description of the AF multiaxial failure stress. These results establish both an experimental approach and the use of the Tsai-Hill model to explain the anisotropic failure behavior of the tissue.
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Affiliation(s)
- Jill M Middendorf
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218
| | - Victor H Barocas
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455
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4
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Bhattacharya S, Dubey DK. A multiscale investigation into the role of collagen-hyaluronan interface shear on the mechanical behaviour of collagen fibers in annulus fibrosus - Molecular dynamics-cohesive finite element-based study. J Mech Behav Biomed Mater 2023; 147:106147. [PMID: 37812947 DOI: 10.1016/j.jmbbm.2023.106147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 06/30/2023] [Accepted: 09/23/2023] [Indexed: 10/11/2023]
Abstract
Multi-directional deformation exhibited by annulus fibrosus (AF) is contributed by chemo-mechanical interactions among its biomolecular constituents' collagen type I (COL-I), collagen type II (COL-II), proteoglycans (aggrecan and hyaluronan) and water. However, the nature and role of such interactions on AF mechanics are unclear. This work employs a molecular dynamics-cohesive finite element-based multiscale approach to investigate role of COL-I-COL-II interchanging distribution and water concentration (WC) variations from outer annulus (OA) to inner annulus (IA) on collagen-hyaluronan (COL-HYL) interface shear, and the mechanisms by which interface shear impacts fibril sliding during collagen fiber deformation. At first, COL-HYL interface atomistic models are constructed by interchanging COL-I with COL-II and increasing COL-II and WC from 0 to 75%, and 65%-75% respectively. Thereafter, a multiscale approach is employed to develop representative volume elements (RVEs) of collagen fibers by incorporating COL-HYL shear as traction-separation behaviour at fibril-hyaluronan contact. Results show that increasing COL-II and WC increases interface stiffness from 0.6 GPa/nm to 1.2 GPa/nm and reduces interface strength from 155 MPa to 58 MPa from OA to IA, contributed by local hydration alterations. A stiffer and weaker interface enhances fibril sliding with increased straining at the contact - thereby contributing to reduction in modulus from 298 MPa to 198 MPa from OA to IA. Such reduction further contributes to softer mechanical response towards IA, as reported by earlier studies. Presented multiscale analysis provides deeper understanding of hierarchical structure-mechanics relationships in AF and can further aid in developing better substitutes for AF repair.
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Affiliation(s)
- Shambo Bhattacharya
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, Haus Khas, New Delhi, 110016, India
| | - Devendra K Dubey
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, Haus Khas, New Delhi, 110016, India.
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5
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Luetkemeyer CM, Neu CP, Calve S. A method for defining tissue injury criteria reveals that ligament deformation thresholds are multimodal. Acta Biomater 2023; 168:252-263. [PMID: 37433358 PMCID: PMC10530537 DOI: 10.1016/j.actbio.2023.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 07/05/2023] [Accepted: 07/06/2023] [Indexed: 07/13/2023]
Abstract
Soft tissue injuries (such as ligament, tendon, and meniscus tears) are the result of extracellular matrix damage from excessive tissue stretching. Deformation thresholds for soft tissues, however, remain largely unknown due to a lack of methods that can measure and compare the spatially heterogeneous damage and deformation that occurs in these materials. Here, we propose a full-field method for defining tissue injury criteria: multimodal strain limits for biological tissues analogous to yield criteria that exist for crystalline materials. Specifically, we developed a method for defining strain thresholds for mechanically-driven fibrillar collagen denaturation in soft tissues, using regional multimodal deformation and damage data. We established this new method using the murine medial collateral ligament (MCL) as our model tissue. Our findings revealed that multiple modes of deformation contribute to collagen denaturation in the murine MCL, contrary to the common assumption that collagen damage is driven only by strain in the direction of fibers. Remarkably, hydrostatic strain (computed here with an assumption of plane strain) was the best predictor of mechanically-driven collagen denaturation in ligament tissue, suggesting crosslink-mediated stress transfer plays a role in molecular damage accumulation. This work demonstrates that collagen denaturation can be driven by multiple modes of deformation and provides a method for defining deformation thresholds, or injury criteria, from spatially heterogeneous data. STATEMENT OF SIGNIFICANCE: Understanding the mechanics of soft tissue injuries is crucial for the development of new technology for injury detection, prevention, and treatment. Yet, tissue-level deformation thresholds for injury are unknown, due to a lack of methods that combine full-field measurements of multimodal deformation and damage in mechanically loaded soft tissues. Here, we propose a method for defining tissue injury criteria: multimodal strain thresholds for biological tissues. Our findings reveal that multiple modes of deformation contribute to collagen denaturation, contrary to the common assumption that collagen damage is driven by strain in the fiber direction alone. The method will inform the development of new mechanics-based diagnostic imaging, improve computational modeling of injury, and be employed to study the role of tissue composition in injury susceptibility.
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Affiliation(s)
- Callan M Luetkemeyer
- Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO, United States; Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL, United States.
| | - Corey P Neu
- Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO, United States; Biomedical Engineering Program, University of Colorado Boulder, Boulder, CO, United States; BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, United States
| | - Sarah Calve
- Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO, United States; Biomedical Engineering Program, University of Colorado Boulder, Boulder, CO, United States; BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, United States; Materials Science and Engineering Program, University of Colorado Boulder, Boulder, CO, United States
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6
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Luetkemeyer CM, Neu CP, Calve S. A method for defining tissue injury criteria reveals ligament deformation thresholds are multimodal. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.31.526318. [PMID: 36778317 PMCID: PMC9915655 DOI: 10.1101/2023.01.31.526318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Soft tissue injuries (such as ligament, tendon, and meniscus tears) are the result of extracellular matrix damage from excessive tissue stretching. Deformation thresholds for soft tissues, however, remain largely unknown due to a lack of methods that can measure and compare the spatially heterogeneous damage and deformation that occurs in these materials. Here, we propose a method for defining tissue injury criteria : multimodal strain limits for biological tissues analogous to yield criteria that exist for crystalline materials. Specifically, we developed a method for defining injury criteria for mechanically-driven fibrillar collagen denaturation in soft tissues, using regional multimodal deformation and damage data. We established this new method using the murine medial collateral ligament (MCL) as our model tissue. Our findings revealed that multiple modes of deformation contribute to collagen denaturation in the murine MCL, contrary to the common assumption that collagen damage is driven by strain in the fiber direction alone. Remarkably, our results indicated that hydrostatic strain, or volumetric expansion, may be the best predictor of mechanically-driven collagen denaturation in ligament tissue, suggesting crosslink-mediated stress transfer plays a role in molecular damage accumulation. This work demonstrates that collagen denaturation can be driven by multiple modes of deformation and provides a method for defining deformation thresholds, or injury criteria, from spatially heterogeneous data.
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7
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Cardoso L, Khadka N, Dmochowski JP, Meneses E, Lee K, Kim S, Jin Y, Bikson M. Computational modeling of posteroanterior lumbar traction by an automated massage bed: predicting intervertebral disc stresses and deformation. FRONTIERS IN REHABILITATION SCIENCES 2022; 3:931274. [PMID: 36189059 PMCID: PMC9397988 DOI: 10.3389/fresc.2022.931274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 06/27/2022] [Indexed: 11/23/2022]
Abstract
Spinal traction is a physical intervention that provides constant or intermittent stretching axial force to the lumbar vertebrae to gradually distract spinal tissues into better alignment, reduce intervertebral disc (IVD) pressure, and manage lower back pain (LBP). However, such axial traction may change the normal lordotic curvature, and result in unwanted side effects and/or inefficient reduction of the IVD pressure. An alternative to axial traction has been recently tested, consisting of posteroanterior (PA) traction in supine posture, which was recently shown effective to increase the intervertebral space and lordotic angle using MRI. PA traction aims to maintain the lumbar lordosis curvature throughout the spinal traction therapy while reducing the intradiscal pressure. In this study, we developed finite element simulations of mechanical therapy produced by a commercial thermo-mechanical massage bed capable of spinal PA traction. The stress relief produced on the lumbar discs by the posteroanterior traction system was investigated on human subject models with different BMI (normal, overweight, moderate obese and extreme obese BMI cases). We predict typical traction levels lead to significant distraction stresses in the lumbar discs, thus producing a stress relief by reducing the compression stresses normally experienced by these tissues. Also, the stress relief experienced by the lumbar discs was effective in all BMI models, and it was found maximal in the normal BMI model. These results are consistent with prior observations of therapeutic benefits derived from spinal AP traction.
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Affiliation(s)
- Luis Cardoso
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States
- *Correspondence: Luis Cardoso
| | - Niranjan Khadka
- Division of Neuropsychiatry and Neuromodulation, Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
| | - Jacek P. Dmochowski
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States
| | - Edson Meneses
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States
| | - Kiwon Lee
- Clinical Research Institute, Ceragem Clinical Inc., Seoul, South Korea
| | - Sungjin Kim
- Clinical Research Institute, Ceragem Clinical Inc., Seoul, South Korea
| | - Youngsoo Jin
- Clinical Research Institute, Ceragem Clinical Inc., Seoul, South Korea
- Asan Medical Center, Seoul, South Korea
| | - Marom Bikson
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States
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8
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Bhattacharya S, Dubey DK. Impact of Variations in Water Concentration on the Nanomechanical Behavior of Type I Collagen Microfibrils in Annulus Fibrosus. J Biomech Eng 2022; 144:1120715. [PMID: 34820681 DOI: 10.1115/1.4052563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Indexed: 11/08/2022]
Abstract
Radial variation in water concentration from outer to inner lamellae is one of the characteristic features of annulus fibrosus (AF). In addition, water concentration changes are also associated with intervertebral disc (IVD) degeneration. Such changes alter the chemo-mechanical interactions among the biomolecular constituents at molecular level, affecting the load-bearing nature of IVD. This study investigates mechanistic impacts of water concentration on the collagen type I microfibrils in AF using molecular dynamics simulations. Results show, in axial tension, that increase in water concentration (WC) from 0% to 50% increases the elastic modulus from 2.7 GPa to 3.9 GPa. This is attributed to combination of shift in deformation from backbone straightening to combined backbone stretching- intermolecular sliding and subsequent strengthening of tropocollagen-water (TC-water-TC) interfaces through water bridges and intermolecular electrostatic attractions. Further increase in WC to 75% reduces the modulus to 1.8 GPa due to shift in deformation to polypeptide straightening and weakening of TC-water-TC interface due to reduced electrostatic attraction and increase in the number of water molecules in a water bridge. During axial compression, increase in WC to 50% results in increase in modulus from 0.8 GPa to 4.5 GPa. This is attributed to the combination of the development of hydrostatic pressure and strengthening of the TC-water-TC interface. Further increase in WC to 75% shifts load-bearing characteristic from collagen to water, resulting in a decrease in elastic modulus to 2.8 GPa. Such water-mediated alteration in load-bearing properties acts as foundations toward AF mechanics and provides insights toward understanding degeneration-mediated altered spinal stiffness.
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Affiliation(s)
- Shambo Bhattacharya
- Department of Mechanical Engineering, Indian Institute of Technology, Delhi, New Delhi 110016, India
| | - Devendra K Dubey
- Department of Mechanical Engineering, Indian Institute of Technology, Delhi, New Delhi 110016, India
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9
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Li M, Pan G, Zhang H, Guo B. Hydrogel adhesives for generalized wound treatment: Design and applications. JOURNAL OF POLYMER SCIENCE 2022. [DOI: 10.1002/pol.20210916] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Meng Li
- State Key Laboratory for Mechanical Behavior of Materials, and Frontier Institute of Science and Technology Xi'an Jiaotong University Xi'an China
| | - Guoying Pan
- State Key Laboratory for Mechanical Behavior of Materials, and Frontier Institute of Science and Technology Xi'an Jiaotong University Xi'an China
| | - Hualei Zhang
- State Key Laboratory for Mechanical Behavior of Materials, and Frontier Institute of Science and Technology Xi'an Jiaotong University Xi'an China
| | - Baolin Guo
- State Key Laboratory for Mechanical Behavior of Materials, and Frontier Institute of Science and Technology Xi'an Jiaotong University Xi'an China
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research College of Stomatology, Xi'an Jiaotong University Xi'an China
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10
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Modeling multiaxial damage regional variation in human annulus fibrosus. Acta Biomater 2021; 136:375-388. [PMID: 34547514 DOI: 10.1016/j.actbio.2021.09.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 09/08/2021] [Accepted: 09/13/2021] [Indexed: 01/03/2023]
Abstract
In the present article, a fully three-dimensional human annulus fibrosus model is developed by considering the regional variation of the complex structural organization of collagen network at different scales to predict the regional anisotropic multiaxial damage of the intervertebral disc. The model parameters are identified using experimental data considering as elementary structural unit, the single annulus lamellae stretched till failure along the micro-sized collagen fibers. The multi-layered lamellar/inter-lamellar annulus model is constructed by considering the effective interactions between adjacent layers and the chemical-induced volumetric strain. The regional dependent model predictions are analyzed under various loading modes and compared to experimental data when available. The stretching along the circumferential and radial directions till failure serves to check the predictive capacities of the annulus model. Model results under simple shear, biaxial stretching and plane-strain compression are further presented and discussed. Finally, a full disc model is constructed using the regional annulus model and simulations are presented to assess the most likely failed areas under disc axial compression. STATEMENT OF SIGNIFICANCE: The damage in annulus soft tissues is a complex multiscale phenomenon due to a complex structural arrangement of collagen network at different scales of hierarchical organization. A fully three-dimensional constitutive representation that considers the regional variation of the structural complexity to estimate annulus multiaxial mechanics till failure has not yet been developed. Here, a model is developed to predict deformation-induced damage and failure of annulus under multiaxial loading histories considering as time-dependent physical process both chemical-induced volumetric effects and damage accumulation. After model identification using single lamellae extracted from different disc regions, the model predictability is verified for various multiaxial elementary loading modes representative of the spine movement. The heterogeneous mechanics of a full human disc model is finally presented.
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11
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Zhou M, Lim S, O’Connell GD. A Robust Multiscale and Multiphasic Structure-Based Modeling Framework for the Intervertebral Disc. Front Bioeng Biotechnol 2021; 9:685799. [PMID: 34164388 PMCID: PMC8215504 DOI: 10.3389/fbioe.2021.685799] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 05/10/2021] [Indexed: 12/11/2022] Open
Abstract
A comprehensive understanding of multiscale and multiphasic intervertebral disc mechanics is crucial for designing advanced tissue engineered structures aiming to recapitulate native tissue behavior. The bovine caudal disc is a commonly used human disc analog due to its availability, large disc height and area, and similarities in biochemical and mechanical properties to the human disc. Because of challenges in directly measuring subtissue-level mechanics, such as in situ fiber mechanics, finite element models have been widely employed in spinal biomechanics research. However, many previous models use homogenization theory and describe each model element as a homogenized combination of fibers and the extrafibrillar matrix while ignoring the role of water content or osmotic behavior. Thus, these models are limited in their ability in investigating subtissue-level mechanics and stress-bearing mechanisms through fluid pressure. The objective of this study was to develop and validate a structure-based bovine caudal disc model, and to evaluate multiscale and multiphasic intervertebral disc mechanics under different loading conditions and with degeneration. The structure-based model was developed based on native disc structure, where fibers and matrix in the annulus fibrosus were described as distinct materials occupying separate volumes. Model parameters were directly obtained from experimental studies without calibration. Under the multiscale validation framework, the model was validated across the joint-, tissue-, and subtissue-levels. Our model accurately predicted multiscale disc responses for 15 of 16 cases, emphasizing the accuracy of the model, as well as the effectiveness and robustness of the multiscale structure-based modeling-validation framework. The model also demonstrated the rim as a weak link for disc failure, highlighting the importance of keeping the cartilage endplate intact when evaluating disc failure mechanisms in vitro. Importantly, results from this study elucidated important fluid-based load-bearing mechanisms and fiber-matrix interactions that are important for understanding disease progression and regeneration in intervertebral discs. In conclusion, the methods presented in this study can be used in conjunction with experimental work to simultaneously investigate disc joint-, tissue-, and subtissue-level mechanics with degeneration, disease, and injury.
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Affiliation(s)
- Minhao Zhou
- Berkeley Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA, United States
| | - Shiyin Lim
- Berkeley Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA, United States
| | - Grace D. O’Connell
- Berkeley Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA, United States
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, United States
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12
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Kirnaz S, Capadona C, Lintz M, Kim B, Yerden R, Goldberg JL, Medary B, Sommer F, McGrath LB, Bonassar LJ, Härtl R. Pathomechanism and Biomechanics of Degenerative Disc Disease: Features of Healthy and Degenerated Discs. Int J Spine Surg 2021; 15:10-25. [PMID: 34376493 DOI: 10.14444/8052] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The human intervertebral disc (IVD) is a complex organ composed of fibrous and cartilaginous connective tissues, and it serves as a boundary between 2 adjacent vertebrae. It provides a limited range of motion in the torso as well as stability during axial compression, rotation, and bending. Adult IVDs have poor innate healing potential due to low vascularity and cellularity. Degenerative disc disease (DDD) generally arises from the disruption of the homeostasis maintained by the structures of the IVD, and genetic and environmental factors can accelerate the progression of the disease. Impaired cell metabolism due to pH alteration and poor nutrition may lead to autophagy and disruption of the homeostasis within the IVD and thus plays a key role in DDD etiology. To develop regenerative therapies for degenerated discs, future studies must aim to restore both anatomical and biomechanical properties of the IVDs. The objective of this review is to give a detailed overview about anatomical, radiological, and biomechanical features of the IVDs as well as discuss the structural and functional changes that occur during the degeneration process.
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Affiliation(s)
- Sertac Kirnaz
- Department of Neurological Surgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York Presbyterian Hospital, New York, New York
| | - Charisse Capadona
- Department of Neurological Surgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York Presbyterian Hospital, New York, New York
| | - Marianne Lintz
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York
| | - Byumsu Kim
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York
| | - Rachel Yerden
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York
| | - Jacob L Goldberg
- Department of Neurological Surgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York Presbyterian Hospital, New York, New York
| | - Branden Medary
- Department of Neurological Surgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York Presbyterian Hospital, New York, New York
| | - Fabian Sommer
- Department of Neurological Surgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York Presbyterian Hospital, New York, New York
| | - Lynn B McGrath
- Department of Neurological Surgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York Presbyterian Hospital, New York, New York
| | - Lawrence J Bonassar
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York.,Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York
| | - Roger Härtl
- Department of Neurological Surgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York Presbyterian Hospital, New York, New York
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13
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Sabouri P, Hashemi A. Influence of crack length and anatomical location on the fracture toughness of annulus fibrosus. Med Eng Phys 2021; 88:1-8. [PMID: 33485508 DOI: 10.1016/j.medengphy.2020.11.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 10/16/2020] [Accepted: 11/21/2020] [Indexed: 01/07/2023]
Abstract
Fracture toughness (Jc) of a soft biological tissue is an important mechanical property that characterizes its resistance to crack or tear extension. To date, no information is available on fracture toughness of annulus fibrosus (AF); therefore, its defect tolerance is not known. The present study modified a previously introduced method to determine Jc of ovine AF. Then, the effect of the notch length on the failure pattern and Jc was investigated. Also, the test samples of anterior and lateral regions were collected to determine the effect of the location on Jc. Results showed that for a notch length of less than 45% of total width, no crack extension occurred, but for a notch length above 45% of the width, crack propagation and ultimately the failure of the AF were observed. However, statistical analysis indicated no significant difference on Jc (p = 0.5) for the initial notch length of 50% and 70% of total width. The fracture toughness was significantly higher for the samples extracted from the lateral site than those from the anterior site (p < 0.05). Dissimilar failure patterns were observed for different initial notch lengths. Among the parameters studied, the defect tolerance of AF was dependent on the initial tear size.
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Affiliation(s)
- Pouya Sabouri
- Biomechanical Engineering Group, Biomedical Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413, Iran
| | - Ata Hashemi
- Biomechanical Engineering Group, Biomedical Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413, Iran.
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14
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Maria Luisa R, Luca C. The Effect of the Loading Rate on the Full-Field Strain Distribution on the Surface on the Intervertebral Discs. J Biomech Eng 2021; 143:011005. [PMID: 32601688 DOI: 10.1115/1.4047662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Indexed: 11/08/2022]
Abstract
Contrasting results are reported when the spine is tested at different strain rates. Tissue specimens from the ligaments or the intervertebral discs (IVD, including annulus fibrosus and nucleus pulposus) exhibit higher stiffness and lower dissipation at high strain rates. Counterintuitively, when spine segments are tested at high rates, the hysteresis area and loop width increase. It is unclear how the load is shared between the different structures at different loading rates. The hypotheses of this study were: (i) As the IVD stiffens at higher loading rates, the strain distribution around the disc would be different depending on the loading rate; (ii) Preconditioning attenuates the strain-rate dependency of the IVD, thus making differences in strain distribution smaller at the different rates. Six segments of three vertebrae (L4-L6) were extracted from porcine spines and tested in presso-flexion at different loading rates (reaching full load in 0.67, 6.7, and 67 s). The full-field strain maps were measured using digital image correlation on the surface of the IVDs from lateral. The posterior-to-anterior trends of the strain were computed in detail for each IVD, and compared between loading rates. The values and the direction of principal strain on the surface of the IVDs, vertebrae, and endplates remained unchanged at different rates. In the transition zone between IVD and vertebra, only slight differences due to the loading rate appeared but with no statistical significance. These findings will allow better understanding of the rate-dependent behavior and failure of the IVD.
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Affiliation(s)
- Ruspi Maria Luisa
- Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum - Università di Bologna, Via Umberto Terracini 24-28, Bologna 40131, Italy
| | - Cristofolini Luca
- Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum - Università di Bologna, Via Umberto Terracini 24-28, Bologna 40131, Italy
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15
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Zhou Z, Cui S, Du J, Richards RG, Alini M, Grad S, Li Z. One strike loading organ culture model to investigate the post-traumatic disc degenerative condition. J Orthop Translat 2020; 26:141-150. [PMID: 33437633 PMCID: PMC7773974 DOI: 10.1016/j.jot.2020.08.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/01/2020] [Accepted: 08/09/2020] [Indexed: 02/06/2023] Open
Abstract
Background Acute trauma on intervertebral discs (IVDs) is thought to be one of the risk factors for IVD degeneration. The pathophysiology of IVD degeneration induced by single high impact mechanical injury is not very well understood. The aim of this study was using a post-traumatic IVD model in a whole organ culture system to analyze the biological and biomechanical consequences of the single high-impact loading event on the cultured IVDs. Methods Isolated healthy bovine IVDs were loaded with a physiological loading protocol in the control group or with injurious loading (compression at 50% of IVD height) in the one strike loading (OSL) group. After another 1 day (short term) or 8 days (long term) of whole organ culture within a bioreactor, the samples were collected to analyze the cell viability, histological morphology and gene expression. The conditioned medium was collected daily to analyze the release of glycosaminoglycan (GAG) and nitric oxide (NO). Results The OSL IVD injury group showed signs of early degeneration including reduction of dynamic compressive stiffness, annulus fibrosus (AF) fissures and extracellular matrix degradation. Compared to the control group, the OSL model group showed more severe cell death (P < 0.01) and higher GAG release in the culture medium (P < 0.05). The MMP and ADAMTS families were up-regulated in both nucleus pulposus (NP) and AF tissues from the OSL model group (P < 0.05). The OSL injury model induced a traumatic degenerative cascade in the whole organ cultured IVD. Conclusions The present study shows a single hyperphysiological mechanical compression applied to healthy bovine IVDs caused significant drop of cell viability, altered the mRNA expression in the IVD, and increased ECM degradation. The OSL IVD model could provide new insights into the mechanism of mechanical injury induced early IVD degeneration. The translational potential of this article This model has a high potential for investigation of the degeneration mechanism in post-traumatic IVD disease, identification of novel biomarkers and therapeutic targets, as well as screening of treatment therapies.
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Affiliation(s)
- Zhiyu Zhou
- The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China.,AO Research Institute Davos, Davos, Switzerland.,Guangdong Provincial Key Laboratory of Orthopedics and Traumatology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Shangbin Cui
- AO Research Institute Davos, Davos, Switzerland.,Guangdong Provincial Key Laboratory of Orthopedics and Traumatology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Jie Du
- AO Research Institute Davos, Davos, Switzerland
| | - R Geoff Richards
- AO Research Institute Davos, Davos, Switzerland.,Guangdong Provincial Key Laboratory of Orthopedics and Traumatology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Mauro Alini
- AO Research Institute Davos, Davos, Switzerland
| | | | - Zhen Li
- AO Research Institute Davos, Davos, Switzerland
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16
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Derrouiche A, Zaouali A, Zaïri F, Ismail J, Qu Z, Chaabane M, Zaïri F. Osmo-inelastic response of the intervertebral disc annulus fibrosus tissue. Proc Inst Mech Eng H 2020; 234:1000-1010. [PMID: 32615851 DOI: 10.1177/0954411920936047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The aim of this article is to provide some insights on the osmo-inelastic response under stretching of annulus fibrosus of the intervertebral disc. Circumferentially oriented specimens of square cross section, extracted from different regions of bovine cervical discs (ventral-lateral and dorsal-lateral), are tested under different strain-rates and saline concentrations within normal range of strains. An accurate optical strain measuring technique, based upon digital image correlation, is used in order to determine the full-field displacements in the lamellae and fibers planes of the layered soft tissue. Annulus stress-stretch relationships are measured along with full-field transversal strains in the two planes. The mechanical response is found hysteretic, rate-dependent and osmolarity-dependent with a Poisson's ratio higher than 0.5 in the fibers plane and negative (auxeticity) in the lamellae plane. While the stiffness presents a regional-dependency due to variations in collagen fibers content/orientation, the strain-rate sensitivity of the response is found independent on the region. A significant osmotic effect is found on both the auxetic response in the lamellae plane and the stiffness rate-sensitivity. These local experimental observations will result in more accurate chemo-mechanical modeling of the disc annulus and a clearer multi-scale understanding of the disc intervertebral function.
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Affiliation(s)
- Amil Derrouiche
- Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), Lille University, Lille, France
| | - Ameni Zaouali
- Mechanical Engineering Laboratory, ENIM, Monastir University, Monastir, Tunisia
| | - Fahmi Zaïri
- Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), Lille University, Lille, France
| | - Jewan Ismail
- Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), Lille University, Lille, France
| | - Zhengwei Qu
- Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), Lille University, Lille, France
| | - Makram Chaabane
- Mechanical Engineering Laboratory, ENIM, Monastir University, Monastir, Tunisia
| | - Fahed Zaïri
- Hôpital privé Le Bois, Ramsay Générale de Santé, Lille, France
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17
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Effect of aggrecan degradation on the nanomechanics of hyaluronan in extra-fibrillar matrix of annulus fibrosus: A molecular dynamics investigation. J Mech Behav Biomed Mater 2020; 107:103752. [PMID: 32278311 DOI: 10.1016/j.jmbbm.2020.103752] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 03/18/2020] [Accepted: 03/20/2020] [Indexed: 12/19/2022]
Abstract
Intervertebral Disc (IVD) Degeneration is one of the primary causes of low back pain among the adult population - the most significant cause being the degradation of aggrecan present in the extra-fibrillar matrix (EFM). Aggrecan degradation is closely associated with loss of water content leading to an alteration in the mechanical behaviour of the IVD. The loss in water content has a significant impact on the chemo-mechanical interplay of IVD biochemical constituents at the fundamental level. This work presents a mechanistic understanding of the effect of hydration, closely associated with aggrecan degradation, on the nanoscale mechanical behaviour of the hyaluronan present in the EFM of the Annulus Fibrosus. For this purpose, explicit three-dimensional molecular dynamics analyses of tensile and compressive tests are performed on a representative atomistic model of the hyaluronan present in the EFM. To account for the degradation of aggrecan, hydration levels are varied from 0 to 75% by weight of water. Analyses show that an increase in the hydration levels decreases the elastic modulus of hyaluronan in tension from ~4.6 GPa to ~2.1 GPa. On the other hand, the increase in hydration level increases the elastic moduli in axial compression from ~1.6 GPa in un-hydrated condition to ~6 GPa in 50% hydrated condition. But as the hydration levels increase to 75%, the elastic modulus reduces to ~3.5 GPa signifying a shift in load-bearing characteristic, from the solid hyaluronan component to the fluid component. Furthermore, analyses show a reduction in the intermolecular energy between hyaluronan and water, under axial tensile loading, indicating a nanoscale intermolecular debonding between hyaluronan and water molecules. This is attributed to the ability of hyaluronan to form stabilizing intra-molecular hydrogen bonds between adjacent residues. Compressive loading, on the other hand, causes intensive coiling of hyaluronan molecule, which traps more water through hydrogen bonding and aids in bearing compressive loads. Overall, study shows that hydration level has a strong influence on the atomistic level interactions between hyaluronan molecules and hyaluronan and water molecules in the EFM which influences the nanoscale mechanics of the Annulus Fibrosus.
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18
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Ghezelbash F, Shirazi-Adl A, Baghani M, Eskandari AH. On the modeling of human intervertebral disc annulus fibrosus: Elastic, permanent deformation and failure responses. J Biomech 2020; 102:109463. [DOI: 10.1016/j.jbiomech.2019.109463] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 10/20/2019] [Accepted: 10/22/2019] [Indexed: 11/26/2022]
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19
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Multiscale composite model of fiber-reinforced tissues with direct representation of sub-tissue properties. Biomech Model Mechanobiol 2019; 19:745-759. [PMID: 31686304 PMCID: PMC7105449 DOI: 10.1007/s10237-019-01246-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Accepted: 10/25/2019] [Indexed: 01/28/2023]
Abstract
In many fiber-reinforced tissues, collagen fibers are embedded within a glycosaminoglycan-rich extrafibrillar matrix. Knowledge of the structure-function relationship between the sub-tissue properties and bulk tissue mechanics is important for understanding tissue failure mechanics and developing biological repair strategies. Difficulties in directly measuring sub-tissue properties led to a growing interest in employing finite element modeling approaches. However, most models are homogeneous and are therefore not sufficient for investigating multiscale tissue mechanics, such as stress distributions between sub-tissue structures. To address this limitation, we developed a structure-based model informed by the native annulus fibrosus structure, where fibers and the matrix were described as distinct materials occupying separate volumes. A multiscale framework was applied such that the model was calibrated at the sub-tissue scale using single-lamellar uniaxial mechanical test data, while validated at the bulk scale by predicting tissue multiaxial mechanics for uniaxial tension, biaxial tension, and simple shear (13 cases). Structure-based model validation results were compared to experimental observations and homogeneous models. While homogeneous models only accurately predicted bulk tissue mechanics for one case, structure-based models accurately predicted bulk tissue mechanics for 12 of 13 cases, demonstrating accuracy and robustness. Additionally, six of eight structure-based model parameters were directly linked to tissue physical properties, further broadening its future applicability. In conclusion, the structure-based model provides a powerful multiscale modeling approach for simultaneously investigating the structure-function relationship at the sub-tissue and bulk tissue scale, which is important for studying multiscale tissue mechanics with degeneration, disease, or injury.
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20
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Mechanical Function of the Nucleus Pulposus of the Intervertebral Disc Under High Rates of Loading. Spine (Phila Pa 1976) 2019; 44:1035-1041. [PMID: 31095121 DOI: 10.1097/brs.0000000000003092] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Bovine motion segments were used to investigate the high-rate compression response of intervertebral discs (IVD) before and after depressurising the nucleus pulposus (NP) by drilling a hole through the cranial endplate into it. OBJECTIVE To investigate the effect of depressurising the NP on the force-displacement response, and the energy absorption in IVDs when compressed at high strain rates. SUMMARY OF BACKGROUND DATA The mechanical function of the gelatinous NP located in the center of the IVDs of the spine is unclear. Removal of the NP has been shown to affect the direction of bulge of the inner anulus fibrosus (AF), but at low loading rates removal of the NP pressure does not affect the IVD's stiffness. During sports or injurious events, IVDs are commonly exposed to high loading rates, however, no studies have investigated the mechanical function of the NP at these rates. METHODS Eight bovine motion segments were used to quantify the change in pressure caused by a hole drilled through the cranial endplate into the NP, and eight segments were used to investigate the high-rate response before and after a hole was drilled into the NP. RESULTS The hole caused a 28.5% drop in the NP pressure. No statistically significant difference was seen in peak force, peak displacement, or energy-absorption of the intact, and depressurized NP groups under impact loading. The IVDs absorbed 72% of the input energy, and there was no rate dependency in the percentage energy absorbed. CONCLUSION These results demonstrate that the NP pressure does not affect the transfer of load through, or energy absorbed by, the IVD at high loading rates and the AF, rather than the NP, may play the most important role in transferring load, and absorbing energy at these rates. This should be considered when attempting surgically to restore IVD function. LEVEL OF EVIDENCE N/A.
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21
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Amin DB, Moawad CM, Costi JJ. New Findings Confirm Regional Internal Disc Strain Changes During Simulation of Repetitive Lifting Motions. Ann Biomed Eng 2019; 47:1378-1390. [PMID: 30923984 DOI: 10.1007/s10439-019-02250-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 03/20/2019] [Indexed: 10/27/2022]
Abstract
To understand the mechanisms of disc injuries that result from repetitive loading, it is important to measure disc deformations and use MRI to quantify disc damage. The aim of this study was to measure internal disc strains during simulated repetitive lifting and their relation to disc injury. Eight cadaveric lumbar segments underwent a pre-test MRI and 20,000 cycles of loading under combined compression (1.0 MPa), hyperflexion, and right axial rotation (2°), which simulated bending and twisting while lifting a 20 kg box. The remaining eight segments had a grid of tantalum wires inserted and used stereoradiography to calculate maximum shear strain (MSS) at increasing cycles. Post-test MRI revealed that 73% of specimens were injured after repetitive loading (annular protrusion, endplate failure, or lumbar disc herniation). MSS at cycle 20,000 was significantly larger than all earlier cycles (p < 0.003). MSS in the anterior, left posterolateral, and left lateral regions was significantly greater than the nucleus region (p < 0.006). Large strains, annular protrusion and herniation in the posterolateral regions were found in this study, which is consistent with clinical observations. In vitro strains can be used to develop more-robust computational models for understanding of the specimen-specific effects of repetitive lifting on disc tissue.
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Affiliation(s)
- D B Amin
- Biomechanics and Implants Research Group, Medical Device Research Institute, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, SA, 5001, Australia
| | - C M Moawad
- Biomechanics and Implants Research Group, Medical Device Research Institute, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, SA, 5001, Australia
| | - J J Costi
- Biomechanics and Implants Research Group, Medical Device Research Institute, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, SA, 5001, Australia.
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22
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Gluais M, Clouet J, Fusellier M, Decante C, Moraru C, Dutilleul M, Veziers J, Lesoeur J, Dumas D, Abadie J, Hamel A, Bord E, Chew SY, Guicheux J, Le Visage C. In vitro and in vivo evaluation of an electrospun-aligned microfibrous implant for Annulus fibrosus repair. Biomaterials 2019; 205:81-93. [PMID: 30909111 DOI: 10.1016/j.biomaterials.2019.03.010] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 02/21/2019] [Accepted: 03/11/2019] [Indexed: 12/29/2022]
Abstract
Annulus fibrosus (AF) impairment is associated with reherniation, discogenic pain, and disc degeneration after surgical partial discectomy. Due to a limited intrinsic healing capacity, defects in the AF persist over time and it is hence necessary to adopt an appropriate strategy to close and repair the damaged AF. In this study, a cell-free biodegradable scaffold made of polycaprolactone (PCL), electrospun, aligned microfibers exhibited high levels of cell colonization, alignment, and AF-like extracellular matrix deposition when evaluated in an explant culture model. The biomimetic multilayer fibrous scaffold was then assessed in an ovine model of AF impairment. After 4 weeks, no dislocation of the implants was detected, and only one sample out of six showed a partial delamination. Histological and immunohistochemical analyses revealed integration of the implant with the surrounding tissue as well as homogeneously aligned collagen fiber organization within each lamella compared to the disorganized and scarcer fibrous tissue in a randomly organized control fibrous scaffold. In conclusion, this biomimetic electrospun implant exhibited promising properties in terms of AF defect closure, with AF-like neotissue formation that fully integrated with the surrounding ovine tissue.
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Affiliation(s)
- Maude Gluais
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; Université de Nantes, UFR Odontologie, Nantes, F-44042, France
| | - Johann Clouet
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; Université de Nantes, UFR Odontologie, Nantes, F-44042, France; CHU Nantes, Pharmacie Centrale, PHU 11, Nantes, F-44093, France; Université de Nantes, UFR Sciences Biologiques et Pharmaceutiques, Nantes, F-44035, France
| | - Marion Fusellier
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; Department of Diagnostic Imaging, CRIP, ONIRIS, College of Veterinary Medicine, Food Science and Engineering, Nantes, F-44307, France
| | - Cyrille Decante
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; CHU Nantes, Service de Chirurgie Infantile, PHU5, Nantes, F-44093, France
| | - Constantin Moraru
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; CHU Nantes, Service de Neurotraumatologie, PHU4 OTONN, Nantes, F-44093, France
| | - Maeva Dutilleul
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; Université de Nantes, UFR Odontologie, Nantes, F-44042, France; INSERM, UMS 016, CNRS 3556, Structure Fédérative de Recherche François Bonamy, SC3M Facility, CHU Nantes, Université de Nantes, Nantes, F-44042, France
| | - Joëlle Veziers
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; Université de Nantes, UFR Odontologie, Nantes, F-44042, France; INSERM, UMS 016, CNRS 3556, Structure Fédérative de Recherche François Bonamy, SC3M Facility, CHU Nantes, Université de Nantes, Nantes, F-44042, France; CHU Nantes, PHU4 OTONN, Nantes, F-44093, France
| | - Julie Lesoeur
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; Université de Nantes, UFR Odontologie, Nantes, F-44042, France; INSERM, UMS 016, CNRS 3556, Structure Fédérative de Recherche François Bonamy, SC3M Facility, CHU Nantes, Université de Nantes, Nantes, F-44042, France
| | - Dominique Dumas
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), UMR 7365 CNRS - Université de Lorraine, Vandœuvre-lès-Nancy, F54505, France; UMS2008 IBSLor - CNRS-UL-INSERM Plateforme d'Imagerie et de Biophysique Cellulaire PTIBC-IBISA, Vandœuvre-lès-Nancy, F54505, France
| | - Jérôme Abadie
- Animal Cancers as Models for Research in Comparative Oncology (AMaROC), ONIRIS, College of Veterinary Medicine, Food Science and Engineering, Nantes, F-44307, France
| | - Antoine Hamel
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; CHU Nantes, Service de Chirurgie Infantile, PHU5, Nantes, F-44093, France
| | - Eric Bord
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; CHU Nantes, Service de Neurotraumatologie, PHU4 OTONN, Nantes, F-44093, France
| | - Sing Yian Chew
- School of Chemical and Biomedical Engineering, Nanyang Technological University, 637459, Singapore; Lee Kong Chian School of Medicine, Nanyang Technological University, 308232, Singapore
| | - Jérôme Guicheux
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; Université de Nantes, UFR Odontologie, Nantes, F-44042, France; CHU Nantes, PHU4 OTONN, Nantes, F-44093, France
| | - Catherine Le Visage
- Inserm, UMR 1229, RMeS, Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, Nantes, F-44042, France; Université de Nantes, UFR Odontologie, Nantes, F-44042, France.
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23
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Derrouiche A, Zaouali A, Zaïri F, Ismail J, Chaabane M, Qu Z, Zaïri F. Osmo-inelastic response of the intervertebral disc. Proc Inst Mech Eng H 2019; 233:332-341. [DOI: 10.1177/0954411919827983] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The intervertebral disc exhibits a complex inelastic response characterized by relaxation, hysteresis during cyclic loading and rate dependency. All these inelastic phenomena depend on osmotic interactions between disc tissues and their surrounding chemical environment. Coupling between osmotic and inelastic effects is not fully understood, so this article aimed to study the influence of chemical conditions on the inelastic behaviour of the intervertebral disc in response to different modes of loading. A total of 18 non-frozen ‘motion segments’ (two vertebrae and the intervening soft tissues) were dissected from the cervical spines of mature sheep. The motion segments were loaded in tension, compression and torsion at various loading rates and saline concentrations. Analysis of variance showed that saline concentration significantly influenced inelastic effects in tension and especially in compression (p < 0.05), but not in torsion. Opposite effects were seen in tension and compression. An interpretation of the underlying osmo-inelastic mechanisms is proposed in which two sources of inelastic effects are identified, that is, extracellular matrix rearrangements and fluid exchange created by osmosis.
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Affiliation(s)
- Amil Derrouiche
- Civil Engineering and geo-Environmental Laboratory (LGCgE) – EA 4515, University of Lille, Lille, France
| | - Ameni Zaouali
- Mechanical Engineering Laboratory, ENIM, University of Monastir, Monastir, Tunisia
| | - Fahmi Zaïri
- Civil Engineering and geo-Environmental Laboratory (LGCgE) – EA 4515, University of Lille, Lille, France
| | - Jewan Ismail
- Civil Engineering and geo-Environmental Laboratory (LGCgE) – EA 4515, University of Lille, Lille, France
| | - Makram Chaabane
- Mechanical Engineering Laboratory, ENIM, University of Monastir, Monastir, Tunisia
| | - Zhengwei Qu
- Civil Engineering and geo-Environmental Laboratory (LGCgE) – EA 4515, University of Lille, Lille, France
| | - Fahed Zaïri
- Hôpital privé Le Bois, Ramsay Générale de Santé, Lille, France
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Abstract
STUDY DESIGN In-vitro study of the tissue mechanics of annulus fibrosus. OBJECTIVE To determine the effect of axial torsion on the mechanical properties of the inter- and intralamellar matrices. SUMMARY OF BACKGROUND DATA Axial torsion, when combined with repetitive flexion, has been associated with an increased risk of intervertebral disc herniation. However, the mechanisms behind this relationship are poorly understood. METHODS Bovine intervertebral discs (IVDs) from the caudal region were exposed to a combination of either 0° or 12° of static axial torsion and 0 N or 1000 N of compression for 2 hours in an attempt to created micro-damage to the IVD. Following the loading protocol, one multilayered sample and two single layer samples were dissected from the annulus fibrosus to undergo tensile testing of the inter- and intralamellar matrices. Histological staining was also performed. RESULTS The strength of the interlamellar matrix was not affected by axial torsion or compression, suggesting that torsion did not damage the interlamellar matrix. However, intralamellar matrix strength of samples exposed to axial torsion, regardless of compressive loading magnitude, was 48% lower than those from samples that were not exposed to torsion (P < 0.001). Similarly, intralamellar matrix stiffness of samples exposed to axial torsion was 42% lower than from samples that were not exposed to torsion (P = 0.010). Additionally, histological analysis demonstrated more disruption within individual lamellae of the samples exposed to axial torsion compared with samples that were not. CONCLUSION This study suggests that axial torsion damages the components of the intralamellar matrix as a result of the strain it puts on the matrix, thus making the intervertebral disc more susceptible to herniation. LEVEL OF EVIDENCE N/A.
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Torre OM, Mroz V, Bartelstein MK, Huang AH, Iatridis JC. Annulus fibrosus cell phenotypes in homeostasis and injury: implications for regenerative strategies. Ann N Y Acad Sci 2018; 1442:61-78. [PMID: 30604562 DOI: 10.1111/nyas.13964] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 08/05/2018] [Accepted: 08/15/2018] [Indexed: 12/11/2022]
Abstract
Despite considerable efforts to develop cellular, molecular, and structural repair strategies and restore intervertebral disk function after injury, the basic biology underlying intervertebral disk healing remains poorly understood. Remarkably, little is known about the origins of cell populations residing within the annulus fibrosus, or their phenotypes, heterogeneity, and roles during healing. This review focuses on recent literature highlighting the intrinsic and extrinsic cell types of the annulus fibrosus in the context of the injury and healing environment. Spatial, morphological, functional, and transcriptional signatures of annulus fibrosus cells are reviewed, including inner and outer annulus fibrosus cells, which we propose to be referred to as annulocytes. The annulus also contains peripheral cells, interlamellar cells, and potential resident stem/progenitor cells, as well as macrophages, T lymphocytes, and mast cells following injury. Phases of annulus fibrosus healing include inflammation and recruitment of immune cells, cell proliferation, granulation tissue formation, and matrix remodeling. However, annulus fibrosus healing commonly involves limited remodeling, with granulation tissues remaining, and the development of chronic inflammatory states. Identifying annulus fibrosus cell phenotypes during health, injury, and degeneration will inform reparative regeneration strategies aimed at improving annulus fibrosus healing.
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Affiliation(s)
- Olivia M Torre
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Victoria Mroz
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Meredith K Bartelstein
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Alice H Huang
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, New York
| | - James C Iatridis
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, New York
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Werbner B, Zhou M, O'Connell G. A Novel Method for Repeatable Failure Testing of Annulus Fibrosus. J Biomech Eng 2017; 139:2653977. [DOI: 10.1115/1.4037855] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Indexed: 11/08/2022]
Abstract
Tears in the annulus fibrosus (AF) of the intervertebral disk can result in disk herniation and progressive degeneration. Understanding AF failure mechanics is important as research moves toward developing biological repair strategies for herniated disks. Unfortunately, failure mechanics of fiber-reinforced tissues, particularly tissues with fibers oriented off-axis from the applied load, is not well understood, partly due to the high variability in reported mechanical properties and a lack of standard techniques ensuring repeatable failure behavior. Therefore, the objective of this study was to investigate the effectiveness of midlength (ML) notch geometries in producing repeatable and consistent tissue failure within the gauge region of AF mechanical test specimens. Finite element models (FEMs) representing several notch geometries were created to predict the location of bulk tissue failure using a local strain-based criterion. FEM results were validated by experimentally testing a subset of the modeled specimen geometries. Mechanical testing data agreed with model predictions (∼90% agreement), validating the model's predictive power. Two of the modified dog-bone geometries (“half” and “quarter”) effectively ensured tissue failure at the ML for specimens oriented along the circumferential-radial and circumferential-axial directions. The variance of measured mechanical properties was significantly lower for notched samples that failed at the ML, suggesting that ML notch geometries result in more consistent and reliable data. In addition, the approach developed in this study provides a framework for evaluating failure properties of other fiber-reinforced tissues, such as tendons and meniscus.
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Affiliation(s)
- Benjamin Werbner
- Mechanical Engineering Department, University of California, Berkeley, 2162 Etcheverry Hall, #1740, Berkeley, CA 94720-1740 e-mail:
| | - Minhao Zhou
- Mechanical Engineering Department, University of California, Berkeley, 2162 Etcheverry Hall, #1740, Berkeley, CA 94720-1740 e-mail:
| | - Grace O'Connell
- Mechanical Engineering Department, University of California, Berkeley, 5122 Etcheverry Hall, #1740, Berkeley, CA 94720-1740 e-mail:
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Grunert P, Moriguchi Y, Grossbard BP, Ricart Arbona RJ, Bonassar LJ, Härtl R. Degenerative changes of the canine cervical spine after discectomy procedures, an in vivo study. BMC Vet Res 2017. [PMID: 28645289 PMCID: PMC5481861 DOI: 10.1186/s12917-017-1105-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Discectomies are a common surgical treatment for disc herniations in the canine spine. However, the effect of these procedures on intervertebral disc tissue is not fully understood. The objective of this study was to assess degenerative changes of cervical spinal segments undergoing discectomy procedures, in vivo. RESULTS Discectomies led to a 60% drop in disc height and 24% drop in foraminal height. Segments did not fuse but showed osteophyte formation as well as endplate sclerosis. MR imaging revealed terminal degenerative changes with collapse of the disc space and loss of T2 signal intensity. The endplates showed degenerative type II Modic changes. Quantitative MR imaging revealed that over 95% of Nucleus Pulposus tissue was extracted and that the nuclear as well as overall disc hydration significantly decreased. Histology confirmed terminal degenerative changes with loss of NP tissue, loss of Annulus Fibrosus organization and loss of cartilage endplate tissue. The bony endplate displayed sclerotic changes. CONCLUSION Discectomies lead to terminal degenerative changes. Therefore, these procedures should be indicated with caution specifically when performed for prophylactic purposes.
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Affiliation(s)
- Peter Grunert
- Department of Neurological Surgery, Weill Cornell Medicine, New York-Presbyterian Hospital, Weill Cornell Brain and Spine Institute
- , 525 East 68th Street, Box 99, New York, NY, 10065, USA.,Department of Neurological Surgery, Swedish Neuroscience Institute, Seattle, WA, USA
| | - Yu Moriguchi
- Department of Neurological Surgery, Weill Cornell Medicine, New York-Presbyterian Hospital, Weill Cornell Brain and Spine Institute
- , 525 East 68th Street, Box 99, New York, NY, 10065, USA
| | - Brian P Grossbard
- Department of Orthopedics and Neurosurgery VCA-Animal Specialty, Yonkers, NY, USA
| | - Rodolfo J Ricart Arbona
- Center of Comparative Medicine and Pathology, Memorial Sloan Kettering Cancer Center & Weill Cornell Medicine, New York City, NY, USA
| | | | - Roger Härtl
- Department of Neurological Surgery, Weill Cornell Medicine, New York-Presbyterian Hospital, Weill Cornell Brain and Spine Institute
- , 525 East 68th Street, Box 99, New York, NY, 10065, USA.
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Tourell MC, Kirkwood M, Pearcy MJ, Momot KI, Little JP. Load-induced changes in the diffusion tensor of ovine anulus fibrosus: A pilot MRI study. J Magn Reson Imaging 2016; 45:1723-1735. [PMID: 28500665 DOI: 10.1002/jmri.25531] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 10/07/2016] [Indexed: 12/22/2022] Open
Abstract
PURPOSE To assess the feasibility of diffusion tensor imaging (DTI) for evaluating changes in anulus fibrosus (AF) microstructure following uniaxial compression. MATERIALS AND METHODS Six axially aligned samples of AF were obtained from a merino sheep disc; two each from the anterior, lateral, and posterior regions. The samples were mechanically loaded in axial compression during five cycles at a rate and maximum compressive strain that reflected physiological conditions. DTI was conducted at 7T for each sample before and after mechanical testing. RESULTS The mechanical response of all samples in unconfined compression was nonlinear. A stiffer response during the first loading cycle, compared to the remaining cycles, was observed. Change in diffusion parameters appeared to be region-dependent. The mean fractional anisotropy increased following mechanical testing. This was smallest in the lateral (2% and 9%) and largest in the anterior and posterior samples (17-25%). The mean average diffusivity remained relatively constant (<2%) after mechanical testing in the lateral and posterior samples, but increased (by 5%) in the anterior samples. The mean angle made by the principal eigenvector with the spine axis in the lateral samples was 73° and remained relatively constant (<2%) following mechanical testing. This angle was smaller in the anterior (55°) and posterior (47°) regions and increased by 6-16° following mechanical testing. CONCLUSION These preliminary results suggest that axial compression reorients the collagen fibers, such that they become more consistently aligned parallel to the plane of the endplates. LEVEL OF EVIDENCE 1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;45:1723-1735.
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Affiliation(s)
- Monique C Tourell
- School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Australia
| | - Margaret Kirkwood
- School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Australia
| | - Mark J Pearcy
- Paediatric Spine Research Group, Centre for Children's Health Research @ IHBI, School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Australia
| | - Konstantin I Momot
- School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Australia
| | - J Paige Little
- Paediatric Spine Research Group, Centre for Children's Health Research @ IHBI, School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Australia
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Muiznieks LD, Keeley FW. Biomechanical Design of Elastic Protein Biomaterials: A Balance of Protein Structure and Conformational Disorder. ACS Biomater Sci Eng 2016; 3:661-679. [DOI: 10.1021/acsbiomaterials.6b00469] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Lisa D. Muiznieks
- Molecular
Structure and Function Program, Research Institute, The Hospital for Sick Children, 686 Bay Street, Toronto, Ontario, Canada M5G 0A4
| | - Fred W. Keeley
- Molecular
Structure and Function Program, Research Institute, The Hospital for Sick Children, 686 Bay Street, Toronto, Ontario, Canada M5G 0A4
- Department
of Biochemistry and Department of Laboratory Medicine and Pathobiology, 1 King’s College Circle, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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Gruevski KM, Gooyers CE, Karakolis T, Callaghan JP. The Effect of Local Hydration Environment on the Mechanical Properties and Unloaded Temporal Changes of Isolated Porcine Annular Samples. J Biomech Eng 2016; 138:2542303. [PMID: 27479500 DOI: 10.1115/1.4034335] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Indexed: 11/08/2022]
Abstract
Preventing dehydration during in vitro testing of isolated layers of annulus fibrosus tissue may require different test conditions than functional spine units. The purpose of the study was twofold: (A) to quantify changes in mass and thickness of multilayer annulus samples in four hydration environments over 120 min; and (B) to quantify cycle-varying biaxial tensile properties of annulus samples in the four environments. The environments included a saline bath, air, relative humidity control, and misting combined with controlled humidity. The loading protocol implemented 24 cycles of biaxial tensile loading to 20% strain at a rate of 2%/s with 3-, 8-, and 13-min of intermittent rest. Specimen mass increased an average (standard deviation) 72% (11) when immersed for 120 min (p < 0.0001). The air condition and the combined mist and relative humidity conditions reduced mass by 45% (15) and 25% (23), respectively, after 120 min (p < 0.0014). Stress at 16% stretch in the air condition was higher at cycle 18 (18 min of exposure) and cycle 24 (33 min of exposure) compared to all other environments in both the axial and circumferential directions (p < 0.0460). There was no significant change in mass or thickness over time in the relative humidity condition and the change in circumferential stress at 16% stretch between cycles 6 and 24 was a maximum of 0.099 MPa and not statistically significant. Implementation of a controlled relative humidity environment is recommended to maintain hydration of isolated annulus layers during cyclic tensile testing.
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Affiliation(s)
- Kristina M. Gruevski
- Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada e-mail:
| | - Chad E. Gooyers
- Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada e-mail:
| | - Thomas Karakolis
- Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada e-mail:
| | - Jack P. Callaghan
- Professor Canada Research Chair in Spine Biomechanics and Injury Prevention, Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada e-mail:
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Stewart DM, Monaco LA, Gregory DE. The aging disc: using an ovine model to examine age-related differences in the biomechanical properties of the intralamellar matrix of single lamellae. EUROPEAN SPINE JOURNAL : OFFICIAL PUBLICATION OF THE EUROPEAN SPINE SOCIETY, THE EUROPEAN SPINAL DEFORMITY SOCIETY, AND THE EUROPEAN SECTION OF THE CERVICAL SPINE RESEARCH SOCIETY 2016; 26:259-266. [DOI: 10.1007/s00586-016-4603-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Revised: 05/03/2016] [Accepted: 05/03/2016] [Indexed: 01/07/2023]
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Gooyers CE, Callaghan JP. Peak Stress in the Annulus Fibrosus Under Cyclic Biaxial Tensile Loading. J Biomech Eng 2016; 138:051006. [PMID: 26974403 DOI: 10.1115/1.4032996] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Indexed: 11/08/2022]
Abstract
Numerous in vitro studies have examined the initiation and propagation of fatigue injury pathways in the annulus fibrosus (AF) using isolated motion segments; however, the cycle-varying changes to the AF under cyclic biaxial tensile loading conditions have yet to be examined. Therefore, the primary objective of this study was to characterize the cycle-varying changes in peak tensile stress in multilayer AF tissue samples within a range of physiologically relevant loading conditions at subacute magnitudes of tissue stretch up to 100 loading cycles. A secondary aim was to examine whether the stress-relaxation response would be different across loading axes (axial and circumferential) and whether this response would vary across regions of the intervertebral disk (IVD) (anterior and posterior-lateral). The results from the study demonstrate that several significant interactions emerged between independent factors that were examined in the study. Specifically, a three-way interaction between the radial location, magnitude of peak tissue stretch, and cycle rate (p = 0.0053) emerged. Significant two-way interactions between the magnitude of tissue stretch and cycle number (p < 0.0001) and the magnitude of tissue stretch and loading axis (p < 0.0001) were also observed. These findings are discussed in the context of known mechanisms for structural damage, which have been linked to fatigue loading in the IVD (e.g., cleft formation, radial tearing, increased neutral zone, disk bulging, and loss of intradiscal pressure).
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Cardwell RD, Kluge JA, Thayer PS, Guelcher SA, Dahlgren LA, Kaplan DL, Goldstein AS. Static and cyclic mechanical loading of mesenchymal stem cells on elastomeric, electrospun polyurethane meshes. J Biomech Eng 2015; 137:2279318. [PMID: 25902471 DOI: 10.1115/1.4030404] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Indexed: 11/08/2022]
Abstract
Biomaterial substrates composed of semi-aligned electrospun fibers are attractive supports for the regeneration of connective tissues because the fibers are durable under cyclic tensile loads and can guide cell adhesion, orientation, and gene expression. Previous studies on supported electrospun substrates have shown that both fiber diameter and mechanical deformation can independently influence cell morphology and gene expression. However, no studies have examined the effect of mechanical deformation and fiber diameter on unsupported meshes. Semi-aligned large (1.75 μm) and small (0.60 μm) diameter fiber meshes were prepared from degradable elastomeric poly(esterurethane urea) (PEUUR) meshes and characterized by tensile testing and scanning electron microscopy (SEM). Next, unsupported meshes were aligned between custom grips (with the stretch axis oriented parallel to axis of fiber alignment), seeded with C3H10T1/2 cells, and subjected to a static load (50 mN, adjusted daily), a cyclic load (4% strain at 0.25 Hz for 30 min, followed by a static tensile loading of 50 mN, daily), or no load. After 3 days of mechanical stimulation, confocal imaging was used to characterize cell shape, while measurements of deoxyribonucleic acid (DNA) content and messenger ribonucleic acid (mRNA) expression were used to characterize cell retention on unsupported meshes and expression of the connective tissue phenotype. Mechanical testing confirmed that these materials deform elastically to at least 10%. Cells adhered to unsupported meshes under all conditions and aligned with the direction of fiber orientation. Application of static and cyclic loads increased cell alignment. Cell density and mRNA expression of connective tissue proteins were not statistically different between experimental groups. However, on large diameter fiber meshes, static loading slightly elevated tenomodulin expression relative to the no load group, and tenascin-C and tenomodulin expression relative to the cyclic load group. These results demonstrate the feasibility of maintaining cell adhesion and alignment on semi-aligned fibrous elastomeric substrates under different mechanical conditions. The study confirms that cell morphology is sensitive to the mechanical environment and suggests that expression of select connective tissue genes may be enhanced on large diameter fiber meshes under static tensile loads.
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Repair using conventional implant for ruptured annulus fibrosus after lumbar discectomy: surgical technique and case series. Asian Spine J 2015; 9:14-21. [PMID: 25705330 PMCID: PMC4330210 DOI: 10.4184/asj.2015.9.1.14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 09/07/2014] [Accepted: 09/09/2014] [Indexed: 12/14/2022] Open
Abstract
Study Design A retrospective review of annulus fibrosus repair (AR) using a novel technique with a conventional implant. Purpose The purpose of this study was to present the feasibility and clinico-radiological outcomes of a novel AR technique using a conventional implant to minimize recurrence following a lumbar discectomy (LD). Overview of Literature Conventional repair techniques to prevent recurrence following LD have several drawbacks. The AR surgical technique has received little attention as an adjunct to LD. Methods A total of 19 patients who underwent novel AR following LD, and who were available for follow-up for at least three years, were enrolled in this study. Several variables, including the type and size of disc herniation, and the degree of disc degeneration, were evaluated preoperatively. Postoperatively, the presence of clinical and radiological recurrence of disc herniation was evaluated from pain intensity and functional statuses, as well as an enhanced L-spine magnetic resonance imaging at the final follow-up. The presence of a peripheral hollow rim and inserted anchor mobilization were also evaluated during the follow-up. Results During follow-ups, there were no recurrences of disc herniation or complications, including neurovascular complications. Pain and functional disability improved significantly after surgery, and the improvement was maintained throughout the three-year follow-up period. No mobilization or implant peripheral hollow rim was observed during the follow-up. Conclusions This study examined the feasibility of a novel and easily available annulus implant technique following LD. These results suggest performing AR with this technique may be a valuable alternative for optimizing outcomes, if the procedure is performed in proper candidates.
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Anderst W, Donaldson W, Lee J, Kang J. Cervical disc deformation during flexion-extension in asymptomatic controls and single-level arthrodesis patients. J Orthop Res 2013; 31:1881-9. [PMID: 23861160 PMCID: PMC4843113 DOI: 10.1002/jor.22437] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 06/18/2013] [Indexed: 02/04/2023]
Abstract
The aim of this study was to characterize cervical disc deformation in asymptomatic subjects and single-level arthrodesis patients during in vivo functional motion. A validated model-based tracking technique determined vertebral motion from biplane radiographs collected during dynamic flexion-extension. Level-dependent differences in disc compression-distraction and shear deformation were identified within the anterior and posterior annulus (PA) and the nucleus of 20 asymptomatic subjects and 15 arthrodesis patients using a mixed-model statistical analysis. In asymptomatic subjects, disc compression and shear deformation per degree of flexion-extension progressively decreased from C23 to C67. The anterior and PA experienced compression-distraction deformation of up to 20%, while the nucleus region was compressed between 0% (C67) and 12% (C23). Peak shear deformation ranged from 16% (at C67) to 33% (at C45). In the C5-C6 arthrodesis group, C45 discs were significantly less compressed than in the control group in all disc regions (all p ≤ 0.026). In the C6-C7 arthrodesis group, C56 discs were significantly less compressed than the control group in the nucleus (p = 0.023) and PA (p = 0.014), but not the anterior annulus (AA; p = 0.137). These results indicate in vivo disc deformation is level-dependent, and single-level anterior arthrodesis alters the compression-distraction deformation in the disc immediately superior to the arthrodesis.
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Affiliation(s)
- William Anderst
- Orthopaedic Surgery; University of Pittsburgh, Biodynamics Lab; 3820 South Water Street Pittsburgh Pennsylvania
| | - William Donaldson
- Orthopaedic Surgery; University of Pittsburgh, Biodynamics Lab; 3820 South Water Street Pittsburgh Pennsylvania
| | - Joon Lee
- Orthopaedic Surgery; University of Pittsburgh, Biodynamics Lab; 3820 South Water Street Pittsburgh Pennsylvania
| | - James Kang
- Orthopaedic Surgery; University of Pittsburgh, Biodynamics Lab; 3820 South Water Street Pittsburgh Pennsylvania
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Baldit A, Ambard D, Cherblanc F, Royer P. Experimental analysis of the transverse mechanical behaviour of annulus fibrosus tissue. Biomech Model Mechanobiol 2013; 13:643-52. [DOI: 10.1007/s10237-013-0524-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 08/10/2013] [Indexed: 11/24/2022]
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Ito K, Creemers L. Mechanisms of intervertebral disk degeneration/injury and pain: a review. Global Spine J 2013; 3:145-52. [PMID: 24436865 PMCID: PMC3854582 DOI: 10.1055/s-0033-1347300] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 04/19/2013] [Indexed: 12/31/2022] Open
Abstract
Degeneration of the intervertebral disk and its treatments are currently intensely investigated topics. Back pain is a condition whose chronic and debilitating nature combined with its prevalence make it a major health issue of substantial socioeconomic importance. Although researchers, and even sometimes clinicians, focus on the degenerated disk as the problem, to most patients, pain is the factor that limits their function and impacts their well-being. The purpose of this review is to delineate the changes associated with disk degeneration and to outline mechanisms by which they could be the source of back pain. Although the healthy disk is only innervated in the external layer of its annulus fibrosus, adjacent structures are plentiful with nociceptive receptors. Stimulation of such structures as a consequence of processes initiated by disk degeneration is explored. The concept of discogenic pain and possible mechanisms such as neoinnervation and solute transport are discussed. Finally, how such pain mechanisms may relate to current and proposed treatment strategies is discussed.
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Affiliation(s)
- Keita Ito
- Orthopaedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands,Address for correspondence Prof. Keita Ito, MD, ScD Orthopaedic Biomechanics, GEM-Z 4.115, Department of Biomedical EngineeringP.O. Box 513, 5600 MB EindhovenThe Netherlands
| | - Laura Creemers
- Department of Orthopaedics, University Medical Center Utrecht, Utrecht, The Netherlands
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MacBarb RF, Makris EA, Hu JC, Athanasiou KA. A chondroitinase-ABC and TGF-β1 treatment regimen for enhancing the mechanical properties of tissue-engineered fibrocartilage. Acta Biomater 2013; 9:4626-34. [PMID: 23041782 DOI: 10.1016/j.actbio.2012.09.037] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 08/24/2012] [Accepted: 09/27/2012] [Indexed: 10/27/2022]
Abstract
The development of functionally equivalent fibrocartilage remains elusive despite efforts to engineer tissues such as knee meniscus, intervertebral disc and temporomandibular joint disc. Attempts to engineer these structures often fail to create tissues with mechanical properties on a par with native tissue, resulting in constructs unsuitable for clinical applications. The objective of this study was to engineer a spectrum of biomimetic fibrocartilages representative of the distinct functional properties found in native tissues. Using the self-assembly process, different co-cultures of meniscus cells and articular chondrocytes were seeded into agarose wells and treated with the catabolic agent chondroitinase-ABC (C-ABC) and the anabolic agent transforming growth factor-β1 (TGF-β1) via a two-factor (cell ratio and bioactive treatment), full factorial study design. Application of both C-ABC and TGF-β1 resulted in a beneficial or positive increase in the collagen content of treated constructs compared to controls. Significant increases in both the collagen density and fiber diameter were also seen with this treatment, increasing these values by 32 and 15%, respectively, over control values. Mechanical testing found the combined bioactive treatment to synergistically increase the Young's modulus and ultimate tensile strength of the engineered fibrocartilages compared to controls, with values reaching the lower spectrum of those found in native tissues. Together, these data demonstrate that C-ABC and TGF-β1 interact to develop a denser collagen matrix better able to withstand tensile loading. This study highlights a way to optimize the tensile properties of engineered fibrocartilage using a biochemical and a biophysical agent together to create distinct fibrocartilages with functional properties mimicking those of native tissue.
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Han WM, Nerurkar NL, Smith LJ, Jacobs NT, Mauck RL, Elliott DM. Multi-scale structural and tensile mechanical response of annulus fibrosus to osmotic loading. Ann Biomed Eng 2012; 40:1610-21. [PMID: 22314837 DOI: 10.1007/s10439-012-0525-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 01/27/2012] [Indexed: 01/04/2023]
Abstract
This study investigates differential multi-scale structure and function relationships of the outer and inner annulus fibrosus (AF) to osmotic swelling in different buffer solutions by quantifying tensile mechanics, glycoasamino-glycan(GAG) content, water content and tissue swelling, and collagen fibril ultrastructure. In the outer AF, the tensile modulus decreased by over 70% with 0.15 M PBS treatment but was unchanged with 2 M PBS treatment. Moreover, the modulus loss following 0.15 M PBS treatment was reversed when followed by 2 M PBS treatment, potentially from increased interfibrillar and interlamellar shearing associated with fibril swelling. In contrast, the inner AF tensile modulus was unchanged by 0.15 M PBS treatment and increased following 2 M treatment. Transmission electron microscopy revealed that the mean collagen fibril diameters of the untreated outer and inner AF were 87.8 ± 27.9 and 71.0 ± 26.9 nm, respectively. In the outer AF, collagen fibril swelling was observed with both 0.15 M and 2 M PBS treatments, but inherently low GAG content remained unchanged. In the inner AF, 2 M PBS treatment caused fibril swelling and GAG loss, suggesting that GAG plays a role in maintaining the structure of collagen fibrils leading to modulation of the native tissue mechanical properties. These results demonstrate important regional variations in structure and composition, and their influence on the heterogeneous mechanics of the AF. Moreover, because the composition and structure is altered as a consequence of progressive disk degeneration, quantification of these interactions is critical for study of the AF pathogenesis of degeneration and tissue engineering
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Affiliation(s)
- Woojin M Han
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA 19104, USA
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40
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Bhattacharjee M, Miot S, Gorecka A, Singha K, Loparic M, Dickinson S, Das A, Bhavesh NS, Ray AR, Martin I, Ghosh S. Oriented lamellar silk fibrous scaffolds to drive cartilage matrix orientation: towards annulus fibrosus tissue engineering. Acta Biomater 2012; 8:3313-25. [PMID: 22641105 DOI: 10.1016/j.actbio.2012.05.023] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2012] [Revised: 04/03/2012] [Accepted: 05/18/2012] [Indexed: 11/20/2022]
Abstract
A novel design of silk-based scaffold is developed using a custom-made winding machine, with fiber alignment resembling the anatomical criss-cross lamellar fibrous orientation features of the annulus fibrosus of the intervertebral disc. Crosslinking of silk fibroin fibers with chondroitin sulphate (CS) was introduced to impart superior biological functionality. The scaffolds, with or without CS, instructed alignment of expanded human chondrocytes and of the deposited extracellular matrix while supporting their chondrogenic redifferentiation. The presence of CS crosslinking could not induce statistically significant changes in the measured collagen or glycosaminoglycan content, but resulted in an increased construct stiffness. By offering the combined effect of cell/matrix alignment and chondrogenic support, the silk fibroin scaffolds developed with precise fiber orientation in lamellar form represent a suitable substrate for tissue engineering of the annulus fibrosus part of the intervertebral disc.
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41
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DeWit JA, Cronin DS. Cervical spine segment finite element model for traumatic injury prediction. J Mech Behav Biomed Mater 2012; 10:138-50. [DOI: 10.1016/j.jmbbm.2012.02.015] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 02/14/2012] [Accepted: 02/22/2012] [Indexed: 10/28/2022]
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Ordway NR, Rim BC, Tan R, Hickman R, Fayyazi AH. Anterior cervical interbody constructs: effect of a repetitive compressive force on the endplate. J Orthop Res 2012; 30:587-92. [PMID: 22002745 DOI: 10.1002/jor.21566] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 09/19/2011] [Indexed: 02/04/2023]
Abstract
Graft subsidence following anterior cervical reconstruction can result in the loss of sagittal balance and recurring foraminal stenosis. This study examined the implant-endplate interface using a cyclic fatigue loading protocol in an attempt to model the subsidence seen in vivo. The superior endplate from 30 cervical vertebrae (C3 to T1) were harvested and biomechanically tested in axial compression with one of three implants: Fibular allograft; titanium mesh cage packed with cancellous chips; and trabecular metal. Each construct was cyclically loaded from 50 to 250 N for 10,000 cycles. Nondestructive cyclic loading of the cervical endplate-implant construct resulted in a stiffer construct independent of the type of the interbody implant tested. The trabecular metal construct demonstrated significantly more axial stability and significantly less subsidence in comparison to the titanium mesh construct. Although the allograft construct resulted in more subsidence than the trabecular metal construct, the difference was not significant and no difference was found when comparing axial stability. For all constructs, the majority of the subsidence during the cyclic testing occurred during the first 500 cycles and was followed by a more gradual settling in the remaining 9,500 cycles.
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Affiliation(s)
- Nathaniel R Ordway
- Department of Orthopedic Surgery, SUNY Upstate Medical University, 750 East Adams Streets, Syracuse, 13201 New York, USA.
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43
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Heuer F, Schmidt H, Käfer W, Graf N, Wilke HJ. Posterior motion preserving implants evaluated by means of intervertebral disc bulging and annular fiber strains. Clin Biomech (Bristol, Avon) 2012; 27:218-25. [PMID: 21983522 DOI: 10.1016/j.clinbiomech.2011.09.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 09/13/2011] [Accepted: 09/13/2011] [Indexed: 02/07/2023]
Abstract
BACKGROUND The aims of motion preserving implants are to ensure sufficient stability to the spine, to release facet joints by also allowing a physiological loading to the intervertebral disc. The aim of this study was to assess disc load contribution by means of annular fiber strains and disc bulging of intact and stiffened segments. This was compared to the segments treated with various motion preserving implants. METHODS A laser scanning device was used to obtain three-dimensional disc bulging and annular fiber strains of six lumbar intervertebral discs (L2-3). Specimens were loaded with 500N or 7.5Nm moments in a spine tester. Each specimen was treated with four different implants; DSS™, internal fixator, Coflex™, and TOPS™. FINDINGS In axial compression, all implants performed in a similar way. In flexion, the Coflex decreased range of motion by 13%, whereas bulging and fiber strains were similar to intact. The DSS stabilized segments by 54% compared to intact. TOPS showed a slight decrease in fiber strains (5%) with a range of motion similar to intact. The rigid fixator allowed strains up to 2%. In lateral bending, TOPS yielded range of motion values similar to intact, but maximum fiber strains doubled from 6.5% (intact) to 13.8%. Coflex showed range of motion, bulging and strain values similar to intact. The DSS and the rigid fixator reduced these values. The implants produced only minor changes in axial rotation. INTERPRETATION This study introduces an in vitro method, which was employed to evaluate spinal implants other than standard biomechanical methods. We could demonstrate that dynamic stabilization methods are able to keep fiber strains and disc bulging in a physiological range.
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Affiliation(s)
- Frank Heuer
- Institute of Orthopaedic Research and Biomechanics, Director Prof. Lutz Claes, University of Ulm, Helmholtzstrasse 14, Ulm, Germany
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Park SH, Gil ES, Mandal BB, Cho H, Kluge JA, Min BH, Kaplan DL. Annulus fibrosus tissue engineering using lamellar silk scaffolds. J Tissue Eng Regen Med 2012; 6 Suppl 3:s24-33. [PMID: 22311816 DOI: 10.1002/term.541] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2010] [Revised: 08/05/2011] [Accepted: 11/03/2011] [Indexed: 01/01/2023]
Abstract
Degeneration of the intervertebral disc (IVD) represents a significant muscular skeletal disease. Recently, scaffolds composed of synthetic, natural and hybrid biomaterials have been investigated as options to restore the IVD; however, they lack the hallmark lamellar morphological features of annulus fibrosus (AF) tissue. The goal of regenerating the disc is to achieve anatomical morphology as well as restoration of mechanical and biological function. In this study, two types of scaffold morphology formed from silk fibroin were investigated towards the goal of AF tissue restoration. The first design mimics the lamellar features of the IVD that are associated with the AF region. The second is a porous spongy scaffold that serves as a control. Toroidal scaffolds were formed from the lamellar and porous silk material systems to generate structures with an outer diameter of 8 mm, inner diameter of 3.5 mm and a height of 3 mm. The inter-lamellar spacing in the lamellar scaffold was 150-250 µm and the average pore sizes in the porous scaffolds were 100-250 µm. The scaffolds were seeded with porcine AF cells and, after growth over defined time frames in vitro, histology, biochemical assays, mechanical testing and gene expression indicated that the lamellar scaffold generated results that were more favourable in terms of ECM expression and tissue function than the porous scaffold for AF tissue. Further, the seeded porcine AF cells supported the native shape of AF tissue in the lamellar silk scaffolds. The lamellar silk scaffolds were effective in the formation of AF-like tissue in vitro.
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Affiliation(s)
- Sang-Hyug Park
- Biomedical Engineering, Tufts University, Medford, MA 02155, USA
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45
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Abstract
STUDY DESIGN In vitro study of the biological response of the intervertebral disc (IVD) to cyclic torsion by using bovine caudal IVDs. OBJECTIVE To evaluate the biological response of the IVD to repetitive cyclic torsion of varying magnitudes at a physiological frequency. SUMMARY OF BACKGROUND DATA Mechanical loading is known to be a risk factor for disc degeneration (DD) but the role of torsion in DD is controversial. It has been suggested that a small magnitude of spinal rotation decreases spinal pressure, increases spinal length, and enhances nutrition exchange in the IVD. However, athletes who participate actively in sports involving torsional movement of the spine are frequently diagnosed with DD and/or disc prolapse. METHODS Bovine caudal discs with end plates were harvested and kept in custom-made chambers for in vitro culture and mechanical stimulation. Torsion was applied to the explants for 1 hour/day over four consecutive days by using a servohydraulic testing machine. The biological response was evaluated by cell viability, metabolic activity, gene expression, glycosaminoglycan content, and histological evaluation. RESULTS A significantly higher cell viability was found in the inner annulus of the 2˚ torsion group than in the static control group. A trend of decreasing metabolic activity in the nucleus pulposus with increasing torsion magnitude was observed. Apoptotic activity in the nucleus pulposus significantly increased with 5˚ torsion. No statistical significant difference in gene expression was found between the three torsion angles. No visible change in matrix organization could be observed by histological evaluation. CONCLUSION The IVD can tolerate short-term repetitive cyclic torsion, as tested in this study. A small angle of cyclic torsion can be beneficial to the IVD in organ culture, possibly by improving nutrition and waste exchange, whereas large torsion angle may cause damage to disc in the long term.
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Ramakrishnan PS, Hong J, Martin JA, Kurriger GL, Buckwalter JA, Lim TH. Biomechanical disc culture system: feasibility study using rat intervertebral discs. Proc Inst Mech Eng H 2011; 225:611-20. [PMID: 22034744 DOI: 10.1177/2041303310394919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A small-scale biomechanical disc culture system was designed to stimulate intervertebral disc (IVD) 'motion segment' in culture environment with load-controlled compression and combined load (compression+shear). After 7 days of diurnal mechanical loading, cell viability of discs stimulated with static compression load (0.25 MPa) and static combined load (compression (0.25 MPa)+shear (1.5N)) were similar (>90 per cent) to unloaded controls. Mechanically stimulated discs showed decrease in static/dynamic moduli, early stress relaxation, and loss of disc height after 7 days of diurnal loading. Histological data of discs indicated load-induced transformations that were not apparent in controls. The feasibility of studying the mechanobiology of intact IVD as a motion segment was demonstrated. Media conditioning (improve tissue stability in long-term culture) and application of biochemical gene expression assays (differential tissue response to types of mechanical stimulation) are proposed as future improvements. The study suggests that the limitations in studying mechanobiology of IVD pathology in vitro can be overcome and it is possible to understand the physiologically relevant mechanism of IVD pathology.
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Affiliation(s)
- P S Ramakrishnan
- Department of Orthopaedic Surgery, University of Iowa, Iowa City, IA, USA
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Panzer MB, Fice JB, Cronin DS. Cervical spine response in frontal crash. Med Eng Phys 2011; 33:1147-59. [DOI: 10.1016/j.medengphy.2011.05.004] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Revised: 05/11/2011] [Accepted: 05/11/2011] [Indexed: 10/18/2022]
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Park SH, Gil ES, Cho H, Mandal BB, Tien LW, Min BH, Kaplan DL. Intervertebral disk tissue engineering using biphasic silk composite scaffolds. Tissue Eng Part A 2011; 18:447-58. [PMID: 21919790 DOI: 10.1089/ten.tea.2011.0195] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Scaffolds composed of synthetic, natural, and hybrid materials have been investigated as options to restore intervertebral disk (IVD) tissue function. These systems fall short of the lamellar features of the native annulus fibrosus (AF) tissue or focus only on the nucleus pulposus (NP) tissue. However, successful regeneration of the entire IVD requires a combination approach to restore functions of both the AF and NP. To address this need, a biphasic biomaterial structure was generated by using silk protein for the AF and fibrin/hyaluronic acid (HA) gels for the NP. Two cell types, porcine AF cells and chondrocytes, were utilized. For the AF tissue, two types of scaffold morphologies, lamellar and porous, were studied with the porous system serving as a control. Toroidal scaffolds formed out of the lamellar, and porous silk materials were used to generate structures with an outer diameter of 8 mm, inner diameter of 3.5 mm, and a height of 3 mm (the interlamellar distance in the lamellar scaffold was 150-250 μm, and the average pore sizes in the porous scaffolds were 100-250 μm). The scaffolds were seeded with porcine AF cells to form AF tissue, whereas porcine chondrocytes were encapsulated in fibrin/HA hydrogels for the NP tissue and embedded in the center of the toroidal disk. Histology, biochemical assays, and gene expression indicated that the lamellar scaffolds supported AF-like tissue over 2 weeks. Porcine chondrocytes formed the NP phenotype within the hydrogel after 4 weeks of culture with the AF tissue that had been previously cultured for 2 weeks, for a total of 6 weeks of cultivation. This biphasic scaffold simulating in combination of both AF and NP tissues was effective in the formation of the total IVD in vitro.
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Affiliation(s)
- Sang-Hyug Park
- Department of Biomedical Engineering, Tufts University, Medford, MA 02155, USA
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Detection of Altered Collagen Fiber Alignment in the Cervical Facet Capsule After Whiplash-Like Joint Retraction. Ann Biomed Eng 2011; 39:2163-73. [DOI: 10.1007/s10439-011-0316-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Accepted: 04/19/2011] [Indexed: 10/18/2022]
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Smith LJ, Elliott DM. Formation of lamellar cross bridges in the annulus fibrosus of the intervertebral disc is a consequence of vascular regression. Matrix Biol 2011; 30:267-74. [PMID: 21504791 DOI: 10.1016/j.matbio.2011.03.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Revised: 03/30/2011] [Accepted: 03/31/2011] [Indexed: 11/30/2022]
Abstract
Cross bridges are radial structures within the highly organized lamellar structure of the annulus fibrosus of the intervertebral disc that connect two or more non-consecutive lamellae. Their origin and function are unknown. During fetal development, blood vessels penetrate deep within the AF and recede during postnatal growth. We hypothesized that cross bridges are the pathways left by these receding blood vessels. Initially, the presence of cross bridges was confirmed in cadaveric human discs aged 25 and 53 years. Next, L1-L2 intervertebral discs (n=4) from sheep ranging in age from 75 days fetal gestation to adult were processed for paraffin histology. Mid-sagittal sections were immunostained for endothelial cell marker PECAM-1. The anterior and posterior AF were imaged using differential interference contrast microscopy, and the following parameters were quantified: total number of distinct lamellae, total number of cross bridges, percentage of cross bridges staining positive for PECAM-1, cross bridge penetration depth (% total lamellae), and PECAM-1 positive cross bridge penetration depth. Cross bridges were first observed at 100 days fetal gestation. The overall number peaked in neonates then remained relatively unchanged. The percentage of PECAM-1 positive cross bridges declined progressively from almost 100% at 100 days gestation to less than 10% in adults. Cross bridge penetration depth peaked in neonates then remained unchanged at subsequent ages. Depth of PECAM-1 positive cross bridges decreased progressively after birth. Findings were similar for both the anterior and posterior. The AF lamellar architecture is established early in development. It later becomes disrupted as a consequence of vascularization. Blood vessels then recede, perhaps due to increasing mechanical stresses in the surrounding matrix. In this study we present evidence that the pathways left by receding blood vessels remain as lamellar cross bridges. It is unclear whether the presence of cross bridges in the aging and degenerating intervertebral disc would be advantageous or detrimental, and this question should be addressed by future studies.
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Affiliation(s)
- Lachlan J Smith
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA 19104, USA
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