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Sapiee NH, Thambyah A, Robertson PA, Broom ND. New evidence for structural integration across the cartilage-vertebral endplate junction and its relation to herniation. Spine J 2019; 19:532-544. [PMID: 30176283 DOI: 10.1016/j.spinee.2018.08.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 08/24/2018] [Accepted: 08/27/2018] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT The cartilaginous and bony material that can be present in herniated tissue suggests that failure can involve both cartilaginous and vertebral-endplates. How structural integration is achieved across the junction between these two distinct tissue regions via its fibril and mineral components is clearly relevant to the modes of endplate failure that occur. PURPOSE To understand how structural integration is achieved across the cartilaginous-vertebral endplate junction. STUDY DESIGN A micro- and fibril-level structural analysis of the cartilage-vertebral endplate region was carried out using healthy, mature ovine motion segments. METHODS Oblique vertebra-annulus-vertebra samples were prepared such that alternate layers of lamellar fibers extended from vertebra to vertebra. The endplate region of each sample was then decalcified in a targeted manner before being loaded in tension along the fiber direction to achieve incomplete rupture within the region of the endplate. The failure regions were then analyzed with differential interference contrast microscopy and scanning electron microscopy. RESULTS Microstructural analysis revealed that failure within the endplate region was not confined to the cement line. Instead, rupture continued into the underlying vertebral endplate with bony material still attached to the now unanchored annular bundles. Ultrastructural analysis of the partially ruptured regions of the cement line revealed clear evidence of blending/interweaving relationships between the fibrils of the annular bundles, the calcified cartilage and the bone with no one pattern of association appearing dominant. These findings suggest that fibril-based structural cohesion exists across the cement line at the site of annular insertion, with strengthening via a mechanism somewhat analogous to steel-reinforced concrete. The fibrils are brought into a close intermingling association with interfibril forces mediated via the mineral component. CONCLUSIONS This study provides clear evidence of structural connectivity across the cartilaginous-vertebral endplate junction by the intermingling of their fibrillar components and mediated by the mineral phase. This is consistent with the clinical observation that in some disc herniations bony material can be still attached to the extruded soft tissue.
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Affiliation(s)
- Nurul Haiza Sapiee
- Experimental Tissue Mechanics Laboratory, Department of Chemical and Materials Engineering, The University of Auckland, 20 Symonds St, 1010 Auckland, New Zealand
| | - Ashvin Thambyah
- Experimental Tissue Mechanics Laboratory, Department of Chemical and Materials Engineering, The University of Auckland, 20 Symonds St, 1010 Auckland, New Zealand
| | - Peter A Robertson
- Department of Orthopaedic Surgery, Auckland City Hospital, 2 Park Road, 1023 Auckland, New Zealand
| | - Neil D Broom
- Experimental Tissue Mechanics Laboratory, Department of Chemical and Materials Engineering, The University of Auckland, 20 Symonds St, 1010 Auckland, New Zealand.
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Three-dimensional microstructural reconstruction of the ovine intervertebral disc using ultrahigh field MRI. Spine J 2018; 18:2119-2127. [PMID: 29969731 DOI: 10.1016/j.spinee.2018.06.356] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 06/22/2018] [Accepted: 06/22/2018] [Indexed: 02/03/2023]
Abstract
BACKGROUND The intervertebral disc (IVD) is a complex organ that acts as a flexible coupling between two adjacent vertebral bodies and must therefore accommodate compression, bending, and torsion. It consists of three main components, which are elegantly structured to allow this: the annulus fibrosus (AF), the nucleus pulposus (NP), and the end-plates (EP). PURPOSE Thus far, it has not been possible to examine the microarchitecture of the disc directly in three dimensions in its unaltered state and thus knowledge of the overall architecture of the disc has been inferred from a range of imaging sources, or by using destructive methods. STUDY DESIGN A nondestructive ultrahigh field Magnetic Resonance Imaging (MRI) of 11.7 T was used together with image analysis to visualize the ovine IVDs. METHODS Three-dimensional image stacks from eight IVDs harvested from sheep, half of which were 4 to 5 years old and the others approximately 2 years old were reconstructed and examined, and their microstructure were imaged. The overall structure of the disc, including the average of 14 AF lamellae (9-28), NP, and EP was then visualized with particular attention given to integrating elements as radial translamellar cross-links, AF-NP transition zone EP-AF integration and EP-NP insertion nodes (ie the connecting junctions between the EP and NP). Moreover, collagen fiber orientation was determined at different depths and locations throughout the annulus. RESULTS It was found that there was a clearer demarcation in the AF-NP transition zone of the younger discs compared with the older ones. This difference was reflected in the visibility of AF-NP and EP-AF integration. It was also possible to view the fiber architecture of the AF-NP integration in greater depth than was possible previously with histological techniques. These fibers were mainly observed in the younger discs and their length was measured to be of 2.6 ± 0.2 mm. CONCLUSIONS The present results provide a substantial advance in visualization of the three-dimensional architecture of an intact IVD and the integration of its components.
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Casaroli G, Villa T, Bassani T, Berger-Roscher N, Wilke HJ, Galbusera F. Numerical Prediction of the Mechanical Failure of the Intervertebral Disc under Complex Loading Conditions. MATERIALS (BASEL, SWITZERLAND) 2017; 10:E31. [PMID: 28772392 PMCID: PMC5344546 DOI: 10.3390/ma10010031] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 12/06/2016] [Accepted: 12/20/2016] [Indexed: 11/16/2022]
Abstract
Finite element modeling has been widely used to simulate the mechanical behavior of the intervertebral disc. Previous models have been generally limited to the prediction of the disc behavior under simple loading conditions, thus neglecting its response to complex loads, which may induce its failure. The aim of this study was to generate a finite element model of the ovine lumbar intervertebral disc, in which the annulus was characterized by an anisotropic hyperelastic formulation, and to use it to define which mechanical condition was unsafe for the disc. Based on published in vitro results, numerical analyses under combined flexion, lateral bending, and axial rotation with a magnitude double that of the physiological ones were performed. The simulations showed that flexion was the most unsafe load and an axial tensile stress greater than 10 MPa can cause disc failure. The numerical model here presented can be used to predict the failure of the disc under all loading conditions, which may support indications about the degree of safety of specific motions and daily activities, such as weight lifting.
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Affiliation(s)
- Gloria Casaroli
- Laboratory of Biological Structure Mechanics (LaBS), Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, 20133 Milan, Italy.
| | - Tomaso Villa
- Laboratory of Biological Structure Mechanics (LaBS), Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, 20133 Milan, Italy.
- IRCCS Istituto Ortopedico Galeazzi, 20161 Milan, Italy.
| | - Tito Bassani
- IRCCS Istituto Ortopedico Galeazzi, 20161 Milan, Italy.
| | - Nikolaus Berger-Roscher
- Institute of Orthopedic Research and Biomechanics, Trauma Research Center Ulm (ZTF), Ulm University, D-89081 Ulm, Germany.
| | - Hans-Joachim Wilke
- Institute of Orthopedic Research and Biomechanics, Trauma Research Center Ulm (ZTF), Ulm University, D-89081 Ulm, Germany.
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Vo NV, Hartman RA, Patil PR, Risbud MV, Kletsas D, Iatridis JC, Hoyland JA, Le Maitre CL, Sowa GA, Kang JD. Molecular mechanisms of biological aging in intervertebral discs. J Orthop Res 2016; 34:1289-306. [PMID: 26890203 PMCID: PMC4988945 DOI: 10.1002/jor.23195] [Citation(s) in RCA: 240] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 02/03/2016] [Indexed: 02/04/2023]
Abstract
Advanced age is the greatest risk factor for the majority of human ailments, including spine-related chronic disability and back pain, which stem from age-associated intervertebral disc degeneration (IDD). Given the rapid global rise in the aging population, understanding the biology of intervertebral disc aging in order to develop effective therapeutic interventions to combat the adverse effects of aging on disc health is now imperative. Fortunately, recent advances in aging research have begun to shed light on the basic biological process of aging. Here we review some of these insights and organize the complex process of disc aging into three different phases to guide research efforts to understand the biology of disc aging. The objective of this review is to provide an overview of the current knowledge and the recent progress made to elucidate specific molecular mechanisms underlying disc aging. In particular, studies over the last few years have uncovered cellular senescence and genomic instability as important drivers of disc aging. Supporting evidence comes from DNA repair-deficient animal models that show increased disc cellular senescence and accelerated disc aging. Additionally, stress-induced senescent cells have now been well documented to secrete catabolic factors, which can negatively impact the physiology of neighboring cells and ECM. These along with other molecular drivers of aging are reviewed in depth to shed crucial insights into the underlying mechanisms of age-related disc degeneration. We also highlight molecular targets for novel therapies and emerging candidate therapeutics that may mitigate age-associated IDD. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1289-1306, 2016.
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Affiliation(s)
- Nam V. Vo
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Robert A. Hartman
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Prashanti R. Patil
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Makarand V. Risbud
- Department of Orthopaedic Surgery, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Dimitris Kletsas
- Laboratory of Cell Proliferation and Ageing, Institute of Biosciences and Applications, National Centre for Scientific Research “Demokritos”, Athens, Greece
| | - James C. Iatridis
- Leni & Peter W May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Judith A. Hoyland
- Centre for Tissue Injury and Repair, Faculty of Medical and Human Sciences, University of Manchester M13 9PT and NIHR Manchester Musculoskeletal Biomedical Research Unit, Manchester Academic Health Science Centre, Manchester, UK
| | - Christine L. Le Maitre
- Musculoskeletal and Regenerative Medicine Research Group, Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, S1 1WB, UK
| | - Gwendolyn A. Sowa
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - James D. Kang
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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Noguchi M, Gooyers CE, Karakolis T, Noguchi K, Callaghan JP. Is intervertebral disc pressure linked to herniation?: An in-vitro study using a porcine model. J Biomech 2016; 49:1824-1830. [PMID: 27157242 DOI: 10.1016/j.jbiomech.2016.04.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 04/14/2016] [Accepted: 04/18/2016] [Indexed: 10/21/2022]
Abstract
Approximately 40% of low back pain cases have been attributed to internal disc disruption. This disruption mechanism may be linked to intradiscal pressure changes, since mechanical loading directly affects the pressure and the stresses that the inner annulus fibrosus experiences. The objective of this study was to characterize cycle-varying changes in four dependent measures (intradiscal pressure, flexion-extension moments, specimen height loss, and specimen rotation angle) using a cyclic flexion-extension (CFE) loading protocol known to induce internal disc disruption. A novel bore-screw pressure sensor system was used to instrument 14 porcine functional spinal units. The CFE loading protocol consisted of 3600 cycles of flexion-extension range of motion (average 18.30 (SD 3.76) degrees) at 1Hz with 1500N of compressive load. On average, intradiscal pressure and specimen height decreased by 47% and 62%, respectively, and peak moments increased by 102%. From 900 to 2100 cycles, all variables exhibited significant changes between successive time points, except for the specimen posture at maximum pressure, which demonstrated a significant shift towards flexion limit after 2700 cycles. There were no further changes in pressure range after 2100 cycles, whereas peak moments and height loss were significantly different from prior time points throughout the CFE protocol. Twelve of the 14 specimens showed partial herniation; however, injury type was not significantly correlated to any of the dependent measures. Although change in pressure was not predictive of damage type, the increase in pressure range seen during this protocol supports the premise that repetitive combined loading (i.e., radial compression, tension and shear) imposes damage to the inner annulus fibrosus, and its failure mechanism may be linked to fatigue.
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Affiliation(s)
- Mamiko Noguchi
- Department of Kinesiology, University of Waterloo, 200 University Avenue West Waterloo, Ontario, Canada N2L 3G1
| | - Chad E Gooyers
- Department of Kinesiology, University of Waterloo, 200 University Avenue West Waterloo, Ontario, Canada N2L 3G1; Giffin Koerth Forensic Engineering & Science, 40 University Avenue Toronto, Ontario, Canada M5J 1T1
| | - Thomas Karakolis
- Defense Research and Development Canada, 1133 Sheppard Avenue West Toronto, Ontario, Canada M3K 2C9
| | - Kimihiro Noguchi
- Department of Mathematics, Western Washington University, 516 High Street Bellingham, Washington 98225, USA
| | - Jack P Callaghan
- Department of Kinesiology, University of Waterloo, 200 University Avenue West Waterloo, Ontario, Canada N2L 3G1.
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Staying connected: structural integration at the intervertebral disc–vertebra interface of human lumbar spines. 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; 26:248-258. [DOI: 10.1007/s00586-016-4560-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 03/30/2016] [Accepted: 03/30/2016] [Indexed: 02/07/2023]
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