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Smit TH. On growth and scoliosis. 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 2024; 33:2439-2450. [PMID: 38705903 DOI: 10.1007/s00586-024-08276-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 03/15/2024] [Accepted: 04/15/2024] [Indexed: 05/07/2024]
Abstract
PURPOSE To describe the physiology of spinal growth in patients with adolescent idiopathic scoliosis (AIS). METHODS Narrative review of the literature with a focus on mechanisms of growth. RESULTS In his landmark publication On Growth and Form, D'Arcy Thompson wrote that the anatomy of an organism reflects the forces it is subjected to. This means that mechanical forces underlie the shape of tissues, organs and organisms, whether healthy or diseased. AIS is called idiopathic because the underlying cause of the deformation is unknown, although many factors are associated. Eventually, however, any deformity is due to mechanical forces. It has long been shown that the typical curvature and rotation of the scoliotic spine could result from vertebrae and intervertebral discs growing faster than the ligaments attached to them. This raises the question why in AIS the ligaments do not keep up with the speed of spinal growth. The spine of an AIS patient deviates from healthy spines in various ways. Growth is later but faster, resulting in higher vertebrae and intervertebral discs. Vertebral bone density is lower, which suggests less spinal compression. This also preserves the notochordal cells and the swelling pressure in the nucleus pulposus. Less spinal compression is due to limited muscular activity, and low muscle mass indeed underlies the lower body mass index (BMI) in AIS patients. Thus, AIS spines grow faster because there is less spinal compression that counteracts the force of growth (Hueter-Volkmann Law). Ligaments consist of collagen fibres that grow by tension, fibrillar sliding and the remodelling of cross-links. Growth and remodelling are enhanced by dynamic loading and by hormones like estrogen. However, they are opposed by static loading. CONCLUSION Increased spinal elongation and reduced ligamental growth result in differential strain and a vicious circle of scoliotic deformation. Recognising the physical and biological cues that contribute to differential growth allows earlier diagnosis of AIS and prevention in children at risk.
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Affiliation(s)
- Theodoor H Smit
- Department of Orthopaedic Surgery and Sports Medicine, Amsterdam University Medical Centres, Amsterdam Movement Sciences, Amsterdam, The Netherlands.
- Department of Medical Biology, Amsterdam University Medical Centres, Meibergdreef 9, Room K2-140, 1105 AZ, Amsterdam, The Netherlands.
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2
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Feki F, Taktak R, Haddar N, Moulart M, Zaïri F, Zaïri F. Overloading effect on the osmo-viscoelastic and recovery behavior of the intervertebral disc. Proc Inst Mech Eng H 2024; 238:430-437. [PMID: 38480472 DOI: 10.1177/09544119241232286] [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] [Indexed: 04/12/2024]
Abstract
In vitro studies investigating the effect of high physiological compressive loads on the intervertebral disc mechanics as well as on its recovery are rare. Moreover, the osmolarity effect on the disc viscoelastic behavior following an overloading is far from being studied. This study aims to determine whether a compressive loading-unloading cycle exceeding physiological limits could be detrimental to the cervical disc, and to examine the chemo-mechanical dependence of this overloading effect. Cervical functional spine units were subjected to a compressive loading-unloading cycle at a high physiological level (displacement of 2.5 mm). The overloading effect on the disc viscoelastic behavior was evaluated through two relaxation tests conducted before and after cyclic loading. Afterward, the disc was unloaded in a saline bath during a rest period, and its recovery response was assessed by a third relaxation test. The chemo-mechanical coupling in the disc response was further examined by repeating this protocol with three different saline concentrations in the external fluid bath. It was found that overloading significantly alters the disc viscoelastic response, with changes statistically dependent on osmolarity conditions. The applied hyper-physiological compressive cycle does not cause damage since the disc recovers its original viscoelastic behavior following a rest period. Osmotic loading only influences the loading-unloading response; specifically, increasing fluid osmolarity leads to a decrease in disc relaxation after the applied cycle. However, the disc recovery is not impacted by the osmolarity of the external fluid.
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Affiliation(s)
- Faten Feki
- Materials Engineering and Environment Laboratory (LGME), ENIS, Sfax University, Sfax, Tunisia
| | - Rym Taktak
- Laboratory of Advanced Material (LMA), ENIS, Sfax University, Sfax, Tunisia
| | - Nader Haddar
- Materials Engineering and Environment Laboratory (LGME), ENIS, Sfax University, Sfax, Tunisia
| | | | - Fahmi Zaïri
- Université de Lille, IMT Nord Europe, JUNIA, Université d'Artois, ULR 4515 - Laboratoire de Génie Civil et géo-Environnement, Lille, France
| | - Fahed Zaïri
- Ramsay Générale de Santé, Hôpital privé Le Bois, Lille, France
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Cherif H, Li L, Snuggs J, Li X, Sammon C, Li J, Beckman L, Haglund L, Le Maitre CL. Injectable hydrogel induces regeneration of naturally degenerate human intervertebral discs in a loaded organ culture model. Acta Biomater 2024; 176:201-220. [PMID: 38160855 DOI: 10.1016/j.actbio.2023.12.041] [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: 10/02/2023] [Revised: 11/30/2023] [Accepted: 12/22/2023] [Indexed: 01/03/2024]
Abstract
Low back pain resulting from disc degeneration is a leading cause of disability worldwide. However, to date few therapies target the cause and fail to repair the intervertebral disc (IVD). This study investigates the ability of an injectable hydrogel (NPgel), to inhibit catabolic protein expression and promote matrix expression in human nucleus pulposus (NP) cells within a tissue explant culture model isolated from degenerate discs. Furthermore, the injection capacity of NPgel into naturally degenerate whole human discs, effects on mechanical function, and resistance to extrusion during loading were investigated. Finally, the induction of potential regenerative effects in a physiologically loaded human organ culture system was investigated following injection of NPgel with or without bone marrow progenitor cells. Injection of NPgel into naturally degenerate human IVDs increased disc height and Young's modulus, and was retained during extrusion testing. Injection into cadaveric discs followed by culture under physiological loading increased MRI signal intensity, restored natural biomechanical properties and showed evidence of increased anabolism and decreased catabolism with tissue integration observed. These results provide essential proof of concept data supporting the use of NPgel as an injectable therapy for disc regeneration. STATEMENT OF SIGNIFICANCE: Low back pain resulting from disc degeneration is a leading cause of disability worldwide. However, to date few therapies target the cause and fail to repair the intervertebral disc. This study investigated the potential regenerative properties of an injectable hydrogel system (NPgel) within human tissue samples. To mimic the human in vivo conditions and the unique IVD niche, a dynamically loaded intact human disc culture system was utilised. NPgel improved the biomechanical properties, increased MRI intensity and decreased degree of degeneration. Furthermore, NPgel induced matrix production and decreased catabolic factors by the native cells of the disc. This manuscript provides evidence for the potential use of NPgel as a regenerative biomaterial for intervertebral disc degeneration.
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Affiliation(s)
- Hosni Cherif
- Department of Surgery, McGill University, Montreal, QC H3G 1A4, Canada
| | - Li Li
- Department of Surgery, McGill University, Montreal, QC H3G 1A4, Canada
| | - Joseph Snuggs
- Oncology and Metabolism Department, Medical School, & INSIGNEO Institute, University of Sheffield, Sheffield, UK; Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK
| | - Xuan Li
- Department of Mechanical Engineering, McGill University, Montreal, QC H3A 0C3, Canada
| | - Christopher Sammon
- Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield, UK
| | - Jianyu Li
- Department of Surgery, McGill University, Montreal, QC H3G 1A4, Canada; Department of Mechanical Engineering, McGill University, Montreal, QC H3A 0C3, Canada; Department of Biomedical Engineering, McGill University, Montreal, QC H3A 2B4, Canada
| | - Lorne Beckman
- Department of Surgery, McGill University, Montreal, QC H3G 1A4, Canada
| | - Lisbet Haglund
- Department of Surgery, McGill University, Montreal, QC H3G 1A4, Canada; Shriners Hospital for Children, Montreal, QC H4A 0A9, Canada
| | - Christine L Le Maitre
- Oncology and Metabolism Department, Medical School, & INSIGNEO Institute, University of Sheffield, Sheffield, UK; Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK.
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Raftery K, Rahman T, Smith N, Schaer T, Newell N. The role of the nucleus pulposus in intervertebral disc recovery: Towards improved specifications for nucleus replacement devices. J Biomech 2024; 166:111990. [PMID: 38383232 DOI: 10.1016/j.jbiomech.2024.111990] [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: 06/07/2023] [Revised: 01/26/2024] [Accepted: 02/07/2024] [Indexed: 02/23/2024]
Abstract
Nucleus replacement devices (NRDs) have potential to treat degenerated or herniated intervertebral discs (IVDs). However, IVD height loss is a post-treatment complication. IVD height recovery involves the nucleus pulposus (NP), but the mechanism of this in response to physiological loads is not fully elucidated. This study aimed to characterise the non-linear recovery behaviour of the IVD in intact, post-nuclectomy, and post-NRD treatment states, under physiological loading. 36 bovine IVDs (12 intact, 12 post-nuclectomy, 12 post-treatment) underwent creep-recovery protocols simulating Sitting, Walking or Running, followed by 12 h of recovery. A rheological model decoupled the fluid-independent (elastic, fast) and fluid-dependent (slow) recovery phases. In post-nuclectomy and post-treatment groups, nuclectomy efficiency (ratio of NP removed to remaining NP) was quantified following post-test sectioning. Relative to intact, post-nuclectomy recovery significantly decreased in Sitting (-0.3 ± 0.4 mm, p < 0.05) and Walking (-0.6 ± 0.3 mm, p < 0.001) coupled with significant decreases to the slow response (p < 0.05). Post-nuclectomy, the fast and slow responses negatively correlated with nuclectomy efficiency (p < 0.05). In all protocols, the post-treatment group performed significantly worse in recovery (-0.5 ± 0.3 mm, p < 0.01) and the slow response (p < 0.05). Results suggest the NP mainly facilitates slow-phase recovery, linearly dependent on the amount of NP present. Failure of this NRD to recover is attributed to poor fluid imbibition. Additionally, unconfined NRD performance cannot be extrapolated to the in vitro response. This knowledge informs NRD design criteria to provide high osmotic pressure, and encourages testing standards to incorporate long-term recovery protocols.
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Affiliation(s)
- K Raftery
- Department of Bioengineering, Imperial College London, London, UK
| | - T Rahman
- Department of Bioengineering, Imperial College London, London, UK; Biomechanics Group, Department of Mechanical Engineering, Imperial College London, London, UK
| | - N Smith
- Division of Surgery and Interventional Science, University College London, Stanmore, UK
| | - T Schaer
- Department of Clinical Studies New Bolton Center, University of Pennsylvania School of Veterinary Medicine, Kennett Square, PA, USA
| | - N Newell
- Department of Bioengineering, Imperial College London, London, UK.
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Sun Z, Sun Y, Lu T, Li J, Mi C. A swelling-based biphasic analysis on the quasi-static biomechanical behaviors of healthy and degenerative intervertebral discs. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2023; 235:107513. [PMID: 37030175 DOI: 10.1016/j.cmpb.2023.107513] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 03/18/2023] [Accepted: 03/26/2023] [Indexed: 05/08/2023]
Abstract
BACKGROUND AND OBJECTIVE The degeneration of intervertebral discs is significantly dependent of the changes in tissue composition ratio and tissue structure. Up to the present, the effects of degeneration on the quasi-static biomechanical responses of discs have not been well understood. The goal of this study is to quantitatively analyze the quasi-static responses of healthy and degenerative discs. METHODS Four biphasic swelling-based finite element models are developed and quantitatively validated. Four quasi-static test protocols, including the free-swelling, slow-ramp, creep and stress-relaxation, are implemented. The double Voigt and double Maxwell models are further used to extract the immediate (or residual), short-term and long-term responses of these tests. RESULTS Simulation results show that both the swelling-induced pressure in the nucleus pulposus and the initial modulus decrease with degeneration. In the free-swelling test of discs possessing healthy cartilage endplates, simulation results show that over 80% of the total strain is contributed by the short-term response. The long-term response is dominant for discs with degenerated permeability in cartilage endplates. For the creep test, over 50% of the deformation is contributed by the long-term response. In the stress-relaxation test, the long-term stress contribution occupies approximately 31% of total response and is independent of degeneration. Both the residual and short-term responses vary monotonically with degeneration. In addition, both the glycosaminoglycan content and permeability affect the engineering equilibrium time constants of the rheologic models, in which the determining factor is the permeability. CONCLUSIONS The content of glycosaminoglycan in intervertebral soft tissues and the permeability of cartilage endplates are two critical factors that affect the fluid-dependent viscoelastic responses of intervertebral discs. The component proportions of the fluid-dependent viscoelastic responses depend also strongly on test protocols. In the slow-ramp test, the glycosaminoglycan content is responsible for the changes of the initial modulus. Since existing computational models simulate disc degenerations only by altering disc height, boundary conditions and material stiffness, the current work highlights the significance of biochemical composition and cartilage endplates permeability in the biomechanical behaviors of degenerated discs.
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Affiliation(s)
- Zhongwei Sun
- Jiangsu Key Laboratory of Engineering Mechanics, School of Civil Engineering, Southeast University, 2 Sipailou Street, Nanjing, 210096, Jiangsu, China
| | - Yueli Sun
- Longhua Hospital, Shanghai University of Traditional Chinese Medicine, 725 South Wanping Road, Shanghai, 200032, Shanghai, China
| | - Teng Lu
- Department of Orthopedics, Second Affiliated Hospital of Xi'an Jiaotong University, 30 Huangcheng West Road, Xi'an, 710004, Shaanxi, China
| | - Jialiang Li
- Department of Orthopedics, Second Affiliated Hospital of Xi'an Jiaotong University, 30 Huangcheng West Road, Xi'an, 710004, Shaanxi, China
| | - Changwen Mi
- Jiangsu Key Laboratory of Engineering Mechanics, School of Civil Engineering, Southeast University, 2 Sipailou Street, Nanjing, 210096, Jiangsu, China.
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AKINCI SALIHAZEYNEB, ARSLAN YUNUSZIYA. FINITE ELEMENT SPINE MODELS AND SPINAL INSTRUMENTS: A REVIEW. J MECH MED BIOL 2022. [DOI: 10.1142/s0219519422300010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
There is considerable biomechanics literature on finite element modeling and analysis of the spine. To accurately mimic the biomechanical behavior of the vertebral column, a generated computational model has to include anatomical structures that are consistent with physiological reality. In this review article, we focused on the finite element spine models that have been developed by various approaches in the literature. Firstly, the anatomical features of the spine and the spinal components have been briefly explained. We then focused on the modeling stages of vertebrae, ligaments, facet joints, intervertebral discs, and spinal instruments. With this paper, we expect to provide a comprehensive resource regarding the modeling preferences used in spine modeling.
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Affiliation(s)
- SALIHA ZEYNEB AKINCI
- Department of Biomedical Engineering and Bioinformatics, Graduate School of Engineering and Natural Sciences, Istanbul Medipol University, 34810 Beykoz, Istanbul, Turkey
| | - YUNUS ZIYA ARSLAN
- Department of Robotics and Intelligent Systems, Institute of Graduate Studies in Science and Engineering, Turkish-German University, Beykoz, Istanbul 34820, Turkey
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7
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Yang M, Xiang D, Wang S, Liu W. In Vitro Studies for Investigating Creep of Intervertebral Discs under Axial Compression: A Review of Testing Environment and Results. MATERIALS 2022; 15:ma15072500. [PMID: 35407833 PMCID: PMC9000064 DOI: 10.3390/ma15072500] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 03/14/2022] [Accepted: 03/22/2022] [Indexed: 01/06/2023]
Abstract
Creep responses of intervertebral discs (IVDs) are essential for spinal biomechanics clarification. Yet, there still lacks a well-recognized investigation protocol for this phenomenon. Current work aims at providing researchers with an overview of the in vitro creep tests reported by previous studies, specifically specimen species, testing environment, loading regimes and major results, based on which a preliminary consensus that may guide future creep studies is proposed. Specimens used in creep studies can be simplified as a “bone–disc–bone” structure where three mathematical models can be adopted for describing IVDs’ responses. The preload of 10–50 N for 30 min or three cycles followed by 4 h-creep under constant compression is recommended for ex vivo simulation of physiological condition of long-time sitting or lying. It is worth noticing that species of specimens, environment temperature and humidity all have influences on biomechanical behaviors, and thus are summarized and compared through the literature review. All factors should be carefully set according to a guideline before tests are conducted to urge comparable results across studies. To this end, this review also provides a guideline, as mentioned before, and specific steps that might facilitate the community of biomechanics to obtain more repeatable and comparable results from both natural specimens and novel biomaterials.
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Affiliation(s)
- Mengying Yang
- Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China;
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China;
- Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China
- Biomechanics and Biotechnology Lab, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057, China
| | - Dingding Xiang
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China;
- School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110819, China
| | - Song Wang
- Biomechanics and Biotechnology Lab, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057, China
- Correspondence: (S.W.); (W.L.)
| | - Weiqiang Liu
- Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China;
- Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China
- Biomechanics and Biotechnology Lab, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057, China
- Correspondence: (S.W.); (W.L.)
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Rasoulian A, Vakili-Tahami F, Smit TH. Linear and Nonlinear Biphasic Mechanical Properties of Goat IVDs Under Different Swelling Conditions in Confined Compression. Ann Biomed Eng 2021; 49:3296-3309. [PMID: 34480262 DOI: 10.1007/s10439-021-02856-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 08/18/2021] [Indexed: 11/25/2022]
Abstract
To define technical specifications for artificial substitutes, it is necessary to model their mechanical behaviour. Here we studied the linear and nonlinear biphasic models for Nucleus Pulposus (NP) and Annulus Fibrosus (AF). The associated material parameters were obtained using confined compression stress relaxation tests on goat intervertebral disc (IVD) samples. The first parameter, aggregate modulus HA0, which essentially describes load-bearing capacity of the solid phase, was larger for AF (HA0 = 0.53 ± 0.06 MPa) than for NP (HA0 = 0.26 ± 0.04 MPa). For hydraulic permeability, which quantifies the ability to transmit interstitial fluid, it was the opposite (k0 = (0.20 ± 0.07) × 10-15 m4/Ns for AF and k0 = (0.67 ± 0.08)×10-15 m4/Ns for NP). The values of nonlinearity coefficients, nonlinear stiffening coefficient β and non-dimensional nonlinear permeability coefficient M, reflected that these tissues had nonlinear elastic behaviour and permeability. Also, investigating the effect of swelling conditions in sample preparation showed that for both AF and NP, confined-swollen samples had higher aggregate modulus and lower permeability values compared to the free-swollen ones. The quantitative description of the nonlinear properties of AF and NP provided a better understanding of IVD behaviour as well as technical specifications for their artificial substitutes.
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Affiliation(s)
- Akbar Rasoulian
- Department of Mechanical Engineering, University of Tabriz, 29 Bahman Blvd., 5166616471, Tabriz, Iran.,Department of Orthopedic Surgery, Amsterdam Movement Sciences, Amsterdam UMC, University of Amsterdam, De Boelelaan 1117, Amsterdam, 1081 HV, The Netherlands
| | - Farid Vakili-Tahami
- Department of Mechanical Engineering, University of Tabriz, 29 Bahman Blvd., 5166616471, Tabriz, Iran.
| | - Theodoor H Smit
- Department of Orthopedic Surgery, Amsterdam Movement Sciences, Amsterdam UMC, University of Amsterdam, De Boelelaan 1117, Amsterdam, 1081 HV, The Netherlands.,Department of Medical Biology, Amsterdam Movement Sciences, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, Amsterdam, 1085 AZ, The Netherlands
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Kandil K, Zaïri F, Messager T, Zaïri F. A microstructure-based model for a full lamellar-interlamellar displacement and shear strain mapping inside human intervertebral disc core. Comput Biol Med 2021; 135:104629. [PMID: 34274895 DOI: 10.1016/j.compbiomed.2021.104629] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 07/02/2021] [Accepted: 07/02/2021] [Indexed: 12/30/2022]
Abstract
The determinant role of the annulus fibrosus interlamellar zones in the intervertebral disc transversal and volumetric responses and hence on their corresponding three-dimensional conducts have been only revealed and appreciated recently. Their consideration in disc modeling strategies has been proven to be essential for the reproduction of correct local strain and displacement fields inside the disc especially in the unconstrained directions of the disc. In addition, these zones are known to be the starting areas of annulus fibrosus circumferential tears and disc delamination failure mode, which is often judged as one of the most dangerous disc failure modes that could evolve with time leading to disc hernia. For this latter reason, the main goal of the current contribution is to incorporate physically for the first time, the interlamellar zones, at the scale of a complete human lumbar intervertebral disc, in order to allow a correct local vision and replication of the different lamellar-interlamellar interactions and an identification of the interlamellar critical zones. By means of a fully tridimensional chemo-viscoelastic constitutive model, which we implemented into a finite element code, the physical, mechanical and chemical contribution of the interlamellar zones is added to the disc. The chemical-induced volumetric response is accounted by the model for both the interlamellar zones and the lamellae using experimentally-based fluid kinetics. Computational simulations are performed and critically discussed upon different simple and complex physiological movements. The disc core and the interlamellar zones are numerically accessed, allowing the observation of the displacement and shear strain fields that are compared to direct MRI experiments from the literature. Important conclusions about the correct lamellar-interlamellar-nucleus interactions are provided thanks to the developed model. The critical interlamellar spots with the highest delamination potentials are defined, analyzed and related to the local kinetics and microstructure.
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Affiliation(s)
- Karim Kandil
- ICAM Site de Lille, 6 Rue Auber, 59016, Lille, France; Univ. Lille, IMT Lille Douai, Univ. Artois, JUNIA, ULR 4515 - LGCgE, Laboratoire de Génie Civil et géo-Environnement, 59000, Lille, France
| | - Fahmi Zaïri
- Univ. Lille, IMT Lille Douai, Univ. Artois, JUNIA, ULR 4515 - LGCgE, Laboratoire de Génie Civil et géo-Environnement, 59000, Lille, France.
| | - Tanguy Messager
- Univ. Lille, Unité de Mécanique de Lille (EA 7572 UML), 59000, Lille, France
| | - Fahed Zaïri
- Ramsay Générale de Santé, Hôpital Privé Le Bois, 59000, Lille, France
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10
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Lee NN, Salzer E, Bach FC, Bonilla AF, Cook JL, Gazit Z, Grad S, Ito K, Smith LJ, Vernengo A, Wilke H, Engiles JB, Tryfonidou MA. A comprehensive tool box for large animal studies of intervertebral disc degeneration. JOR Spine 2021; 4:e1162. [PMID: 34337336 PMCID: PMC8313180 DOI: 10.1002/jsp2.1162] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 05/25/2021] [Accepted: 05/26/2021] [Indexed: 12/12/2022] Open
Abstract
Preclinical studies involving large animal models aim to recapitulate the clinical situation as much as possible and bridge the gap from benchtop to bedside. To date, studies investigating intervertebral disc (IVD) degeneration and regeneration in large animal models have utilized a wide spectrum of methodologies for outcome evaluation. This paper aims to consolidate available knowledge, expertise, and experience in large animal preclinical models of IVD degeneration to create a comprehensive tool box of anatomical and functional outcomes. Herein, we present a Large Animal IVD Scoring Algorithm based on three scales: macroscopic (gross morphology, imaging, and biomechanics), microscopic (histological, biochemical, and biomolecular analyses), and clinical (neurologic state, mobility, and pain). The proposed algorithm encompasses a stepwise evaluation on all three scales, including spinal pain assessment, and relevant structural and functional components of IVD health and disease. This comprehensive tool box was designed for four commonly used preclinical large animal models (dog, pig, goat, and sheep) in order to facilitate standardization and applicability. Furthermore, it is intended to facilitate comparison across studies while discerning relevant differences between species within the context of outcomes with the goal to enhance veterinary clinical relevance as well. Current major challenges in pre-clinical large animal models for IVD regeneration are highlighted and insights into future directions that may improve the understanding of the underlying pathologies are discussed. As such, the IVD research community can deepen its exploration of the molecular, cellular, structural, and biomechanical changes that occur with IVD degeneration and regeneration, paving the path for clinically relevant therapeutic strategies.
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Affiliation(s)
- Naomi N. Lee
- Thompson Laboratory for Regenerative OrthopaedicsUniversity of MissouriColumbiaMissouriUSA
| | - Elias Salzer
- Orthopaedic Biomechanics, Department of Biomedical EngineeringEindhoven University of TechnologyEindhovenThe Netherlands
| | - Frances C. Bach
- Department of Clinical Sciences, Faculty of Veterinary MedicineUtrecht UniversityUtrechtThe Netherlands
| | - Andres F. Bonilla
- Preclinical Surgical Research Laboratory, Department of Clinical SciencesColorado State UniversityColoradoUSA
| | - James L. Cook
- Thompson Laboratory for Regenerative OrthopaedicsUniversity of MissouriColumbiaMissouriUSA
| | - Zulma Gazit
- Department of SurgeryCedars‐Sinai Medical CenterLos AngelesCaliforniaUSA
| | | | - Keita Ito
- Orthopaedic Biomechanics, Department of Biomedical EngineeringEindhoven University of TechnologyEindhovenThe Netherlands
| | - Lachlan J. Smith
- Departments of Neurosurgery and Orthopaedic SurgeryUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Andrea Vernengo
- AO Research Institute DavosDavosSwitzerland
- Department of Chemical EngineeringRowan UniversityGlassboroNew JerseyUSA
| | - Hans‐Joachim Wilke
- Institute of Orthopaedic Research and BiomechanicsUniversity Hospital UlmUlmGermany
| | - Julie B. Engiles
- Department of Pathobiology, New Bolton Center, School of Veterinary MedicineUniversity of PennsylvaniaKennett SquarePennsylvaniaUSA
| | - Marianna A. Tryfonidou
- Department of Clinical Sciences, Faculty of Veterinary MedicineUtrecht UniversityUtrechtThe Netherlands
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11
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Komeili A, Rasoulian A, Moghaddam F, El-Rich M, Li LP. The importance of intervertebral disc material model on the prediction of mechanical function of the cervical spine. BMC Musculoskelet Disord 2021; 22:324. [PMID: 33794848 PMCID: PMC8017640 DOI: 10.1186/s12891-021-04172-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 03/10/2021] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND Linear elastic, hyperelastic, and multiphasic material constitutive models are frequently used for spinal intervertebral disc simulations. While the characteristics of each model are known, their effect on spine mechanical response requires a careful investigation. The use of advanced material models may not be applicable when material constants are not available, model convergence is unlikely, and computational time is a concern. On the other hand, poor estimations of tissue's mechanical response are likely if the spine model is oversimplified. In this study, discrepancies in load response introduced by material models will be investigated. METHODS Three fiber-reinforced C2-C3 disc models were developed with linear elastic, hyperelastic, and biphasic behaviors. Three different loading modes were investigated: compression, flexion and extension in quasi-static and dynamic conditions. The deformed disc height, disc fluid pressure, range of motion, and stresses were compared. RESULTS Results indicated that the intervertebral disc material model has a strong effect on load-sharing and disc height change when compression and flexion were applied. The predicted mechanical response of three models under extension had less discrepancy than its counterparts under flexion and compression. The fluid-solid interaction showed more relevance in dynamic than quasi-static loading conditions. The fiber-reinforced linear elastic and hyperelastic material models underestimated the load-sharing of the intervertebral disc annular collagen fibers. CONCLUSION This study confirmed the central role of the disc fluid pressure in spinal load-sharing and highlighted loading conditions where linear elastic and hyperelastic models predicted energy distribution different than that of the biphasic model.
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Affiliation(s)
- Amin Komeili
- School of Engineering, University of Guelph, Guelph, Canada.
| | | | | | - Marwan El-Rich
- Healthcare Engineering Innovation Center, Department of Mechanical Engineering, Khalifa University, Abu Dhabi, United Arab Emirates
| | - Le Ping Li
- Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Canada
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Smit TH. Adolescent idiopathic scoliosis: The mechanobiology of differential growth. JOR Spine 2020; 3:e1115. [PMID: 33392452 PMCID: PMC7770204 DOI: 10.1002/jsp2.1115] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 07/02/2020] [Indexed: 12/16/2022] Open
Abstract
Adolescent idiopathic scoliosis (AIS) has been linked to neurological, genetic, hormonal, microbial, and environmental cues. Physically, however, AIS is a structural deformation, hence an adequate theory of etiology must provide an explanation for the forces involved. Earlier, we proposed differential growth as a possible mechanism for the slow, three-dimensional deformations observed in AIS. In the current perspective paper, the underlying mechanobiology of cells and tissues is explored. The musculoskeletal system is presented as a tensegrity-like structure, in which the skeletal compressive elements are stabilized by tensile muscles, ligaments, and fasciae. The upright posture of the human spine requires minimal muscular energy, resulting in less compression, and stability than in quadrupeds. Following Hueter-Volkmann Law, less compression allows for faster growth of vertebrae and intervertebral discs. The substantially larger intervertebral disc height observed in AIS patients suggests high intradiscal pressure, a condition favorable for notochordal cells; this promotes the production of proteoglycans and thereby osmotic pressure. Intradiscal pressure overstrains annulus fibrosus and longitudinal ligaments, which are then no longer able to remodel and grow, and consequently induce differential growth. Intradiscal pressure thus is proposed as the driver of AIS and may therefore be a promising target for prevention and treatment.
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Affiliation(s)
- Theodoor H. Smit
- Department of Orthopaedic SurgeryAmsterdam Movement Sciences, Amsterdam University Medical CentresAmsterdamNetherlands
- Department of Medical BiologyAmsterdam University Medical CentresAmsterdamNetherlands
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Feki F, Taktak R, Kandil K, Derrouiche A, Moulart M, Haddar N, Zaïri F, Zaïri F. How Osmoviscoelastic Coupling Affects Recovery of Cyclically Compressed Intervertebral Disc. Spine (Phila Pa 1976) 2020; 45:E1376-E1385. [PMID: 33031252 DOI: 10.1097/brs.0000000000003593] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Osmoviscoelastic behavior of cyclically loaded cervical intervertebral disc. OBJECTIVE The aim of this study was to evaluate in vitro the effects of physiologic compressive cyclic loading on the viscoelastic properties of cervical intervertebral disc and, examine how the osmoviscoelastic coupling affects time-dependent recovery of these properties following a long period of unloading. SUMMARY OF BACKGROUND DATA The human neck supports repetitive loadings during daily activities and recovery of disc mechanics is essential for normal mechanical function. However, the response of cervical intervertebral disc to cyclic loading is still not very well defined. Moreover, how loading history conditions could affect the time-dependent recovery is still unclear. METHODS Ten thousand cycles of compressive loading, with different magnitudes and saline concentrations of the surrounding fluid bath, are applied to 8 motion segments (composed by 2 adjacent vertebrae and the intervening disc) extracted from the cervical spines of mature sheep. Subsequently, specimens are hydrated during 18 hours of unloading. The viscoelastic disc responses, after cyclic loading and recovery phase, are characterized by relaxation tests. RESULTS Viscoelastic behaviors are significantly altered following large number of cyclic loads. Moreover, after 18-hour recovery period in saline solution at reference concentration (0.15 mol/L), relaxation behaviors were fully restored. Nonetheless, full recovery is not obtained whether the concentration of the surrounding fluid, that is, hypo-, iso-, or hyper-osmotic conditions. CONCLUSION Cyclic loading effects and full recovery of viscoelastic behavior after hydration at iso-osmotic condition (0.15 mol/L) are governed by osmotic attraction of fluid content in the disc due to imbalance between the external load and the swelling pressure of the disc. After removal of the load, the disc recovers its viscoelastic properties following period of rest. Nevertheless, the viscoelastic recovery is a chemically activated process and its dependency on saline concentration is governed by fluid flow due to imbalance of ions between the disc tissues and the surrounding fluid. LEVEL OF EVIDENCE 3.
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Affiliation(s)
- Faten Feki
- ENIS, Materials Engineering and Environment Laboratory (LGME), Sfax, Tunisia
| | - Rym Taktak
- ENIS, Materials Engineering and Environment Laboratory (LGME), Sfax, Tunisia
| | - Karim Kandil
- Lille University, Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), Lille, France
| | - Amil Derrouiche
- Lille University, Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), Lille, France
| | | | - Nader Haddar
- ENIS, Materials Engineering and Environment Laboratory (LGME), Sfax, Tunisia
| | - Fahmi Zaïri
- Lille University, Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), Lille, France
| | - Fahed Zaïri
- Ramsay Générale de Santé, Hôpital privé Le Bois, Lille, France
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Development of a multiscale model of the human lumbar spine for investigation of tissue loads in people with and without a transtibial amputation during sit-to-stand. Biomech Model Mechanobiol 2020; 20:339-358. [PMID: 33026565 DOI: 10.1007/s10237-020-01389-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 09/19/2020] [Indexed: 01/14/2023]
Abstract
Quantification of lumbar spine load transfer is important for understanding low back pain, especially among persons with a lower limb amputation. Computational modeling provides a helpful solution for obtaining estimates of in vivo loads. A multiscale model was constructed by combining musculoskeletal and finite element (FE) models of the lumbar spine to determine tissue loading during daily activities. Three-dimensional kinematic and ground reaction force data were collected from participants with ([Formula: see text]) and without ([Formula: see text]) a unilateral transtibial amputation (TTA) during 5 sit-to-stand trials. We estimated tissue-level load transfer from the multiscale model by controlling the FE model with intervertebral kinematics and muscle forces predicted by the musculoskeletal model. Annulus fibrosis stress, intradiscal pressure (IDP), and facet contact forces were calculated using the FE model. Differences in whole-body kinematics, muscle forces, and tissue-level loads were found between participant groups. Notably, participants with TTA had greater axial rotation toward their intact limb ([Formula: see text]), greater abdominal muscle activity ([Formula: see text]), and greater overall tissue loading throughout sit-to-stand ([Formula: see text]) compared to able-bodied participants. Both normalized (to upright standing) and absolute estimates of L4-L5 IDP were close to in vivo values reported in the literature. The multiscale model can be used to estimate the distribution of loads within different lumbar spine tissue structures and can be adapted for use with different activities, populations, and spinal geometries.
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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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Derrouiche A, Feki F, Zaïri F, Taktak R, Moulart M, Qu Z, Ismail J, Charfi S, Haddar N, Zaïri F. How pre-strain affects the chemo-torsional response of the intervertebral disc. Clin Biomech (Bristol, Avon) 2020; 76:105020. [PMID: 32416404 DOI: 10.1016/j.clinbiomech.2020.105020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 04/22/2020] [Accepted: 04/26/2020] [Indexed: 02/07/2023]
Abstract
BACKGROUND The role of the axial pre-strain on the torsional response of the intervertebral disc remains largely undefined. Moreover, the chemo-mechanical interactions in disc tissues are still unclear and corresponding data are rare in the literature. The paper deals with an in-vitro study of the pre-strain effect on the chemical sensitivity of the disc torsional response. METHODS Fifteen non-frozen 'motion segments' (two vertebrae and the intervening soft tissues) were extracted from the cervical spines of mature sheep. The motion segments were loaded in torsion at various saline concentrations and axial pre-strain levels in order to modulate the intradiscal pressure. After preconditioning with successive low-strain compressions at a magnitude of 0.1 mm (10 cycles at 0.05 mm/s), the motion segment was subjected to a cyclic torsion until a twisting level of 2 deg. at 0.05 deg./s while a constant axial pre-strain (in compression or in tension) is maintained, the saline concentration of the surrounding fluid bath being changed from hypo-osmotic condition to hyper-osmotic condition. FINDINGS Analysis of variance shows that the saline concentration influences the torsional response only when the motion segments are pre-compressed (p < .001) with significant differences between hypo-osmotic condition and hyper-osmotic condition. INTERPRETATION The combination of a compressive pre-strain with twisting amplifies the nucleus hydrostatic pressure on the annulus and the annulus collagen fibers tensions. The proteoglycans density increases with the compressive pre-strain and leads to higher chemical imbalances, which would explain the increase in chemical sensitivity of the disc torsional response.
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Affiliation(s)
- Amil Derrouiche
- Lille University, Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), 59000 Lille, France
| | - Faten Feki
- Sfax University, ENIS, Materials Engineering and Environment Laboratory (LGME), 3038 Sfax, Tunisia
| | - Fahmi Zaïri
- Lille University, Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), 59000 Lille, France.
| | - Rym Taktak
- Sfax University, ENIS, Materials Engineering and Environment Laboratory (LGME), 3038 Sfax, Tunisia
| | | | - Zhengwei Qu
- Lille University, Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), 59000 Lille, France
| | - Jewan Ismail
- Lille University, Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), 59000 Lille, France
| | - Slim Charfi
- Habib Bourguiba Hospital, Pathology department, 3038 Sfax, Tunisia
| | - Nader Haddar
- Sfax University, ENIS, Materials Engineering and Environment Laboratory (LGME), 3038 Sfax, Tunisia
| | - Fahed Zaïri
- Ramsay Générale de Santé, Hôpital privé Le Bois, 59000 Lille, France
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Nonlinear stress-dependent recovery behavior of the intervertebral disc. J Mech Behav Biomed Mater 2020; 110:103881. [PMID: 32957189 DOI: 10.1016/j.jmbbm.2020.103881] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 04/22/2020] [Accepted: 05/23/2020] [Indexed: 12/17/2022]
Abstract
The intervertebral disc exhibits complex mechanics due to its heterogeneous structure, inherent viscoelasticity, and interstitial fluid-matrix interactions. Sufficient fluid flow into the disc during low loading periods is important for maintaining mechanics and nutrient transport. However, there is a lack of knowledge on the effect of loading magnitude on time-dependent recovery behavior and the relative contribution of multiple recovery mechanisms during recovery. In most studies that have evaluated disc recovery behavior, a single load condition has been considered, making it difficult to compare findings across studies. Hence, the objective of this study was to quantify unloaded disc recovery behavior after compressive creep loading under a wide range of physiologically relevant stresses (0.2-2 MPa). First, the repeatability of disc recovery behavior was assessed. Once repeatable recovery behavior was confirmed, each motion segment was subject to three cycles of creep-recovery loading, where each cycle consisted of a 24-h creep at a pre-assigned load (100, 200, 300, 600, 900, or 1200 N), followed by an 18-h recovery period at a nominal load (10 N). Results showed that disc recovery behavior was strongly influenced by the magnitude of loading. The magnitude of instantaneous and time-dependent recovery deformations increased nonlinearly with an increase in compressive stress during creep. In conclusion, this study highlights that elastic deformation, intrinsic viscoelasticity, and poroelasticity all have substantial contributions to disc height recovery during low loading periods. However, their relative contributions to disc height recovery largely depend on the magnitude of loading. While loading history does not influence the contribution of the short-term recovery, the contribution of long-term recovery is highly sensitive to loading magnitude.
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18
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The two Poisson’s ratios in annulus fibrosus: relation with the osmo-inelastic features. ACTA ACUST UNITED AC 2020. [DOI: 10.1007/s42558-019-0016-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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19
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Interlamellar-induced time-dependent response of intervertebral disc annulus: A microstructure-based chemo-viscoelastic model. Acta Biomater 2019; 100:75-91. [PMID: 31586727 DOI: 10.1016/j.actbio.2019.10.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 09/27/2019] [Accepted: 10/02/2019] [Indexed: 01/07/2023]
Abstract
The annulus fibrosus of the intervertebral disc exhibits an unusual transversal behavior for which a constitutive representation that considers as well regional effect, chemical sensitivity and time-dependency has not yet been developed, and it is hence the aim of the present contribution. A physically-based model is proposed by introducing a free energy function that takes into account the actual disc annulus structure in relation with the surrounding biochemical environment. The response is assumed to be dominated by the viscoelastic contribution of the extracellular matrix, the elastic contribution of the oriented collagen fibers and the osmo-induced volumetric contribution of the internal fluid content variation. The regional dependence of the disc annulus response due to variation in fibers content/orientation allows a micromechanical treatment of the soft tissue. A finite element model of the annulus specimen is designed while taking into consideration the 'interlamellar' ground substance zone between lamellae of the layered soft tissue. The kinetics is designed using full-field strain measurements performed on specimens extracted from two disc annulus regions and tested under different osmotic conditions. The time-dependency of the tissue response is reported on stress-free volumetric changes, on hysteretic stress and transversal strains during quasi-static stretching at different strain-rates and on their temporal changes during an interrupted stretching. Considering the effective contributions of the internal fluid transfer and the extracellular matrix viscosity, the microstructure-based chemo-mechanical model is found able to successfully reproduce the significant features of the macro-response and the unusual transversal behavior including the strong regional dependency from inner to outer parts of the disc: Poisson's ratio lesser than 0 (auxetic) in lamellae plane, higher than 0.5 in fibers plane, and their temporal changes towards usual values (between 0 and 0.5) at chemo-mechanical equilibrium. The underlying time-dependent mechanisms occurring in the tissue are analyzed via the local numerical fields and important insights about the effective role of the interlamellar zone are revealed for the different disc localizations. STATEMENT OF SIGNIFICANCE: The structural complexity of the annulus fibrosus has only been appreciated through recent experimental contributions and a constitutive representation that considers as well regional effect, chemical sensitivity and time-dependency of the unusual transversal behavior has not yet been developed. Here, a microstructure-based chemo-viscoelastic model is developed to highlight the interlamellar-induced time-dependent response by means of a two-scale strategy. The model provides important insights about the origin of the time-dependent phenomena in disc annulus along with regional dependency, essential for understanding disc functionality.
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Wang K, Wang L, Deng Z, Jiang C, Niu W, Zhang M. Influence of passive elements on prediction of intradiscal pressure and muscle activation in lumbar musculoskeletal models. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2019; 177:39-46. [PMID: 31319959 DOI: 10.1016/j.cmpb.2019.05.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 05/17/2019] [Accepted: 05/17/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND AND OBJECTIVE The objective of this study was to investigate the effect of incorporating various passive elements, which could represent combined or individual effects of intervertebral disc, facet articulation and ligaments, on the prediction of lumbar muscle activation and L4-L5 intradiscal pressure. METHODS The passive elements representing the intervertebral disc, facet articulations, and ligaments were added to the existed lumbar musculoskeletal model with nonlinear rotational stiffness or force-strain relationships. The model was fed with kinematics of trunk flexion, extension, axial rotation and lateral bending to calculate muscle activation and L4-L5 intradiscal pressure. RESULTS In the trunk axial rotation, the intradiscal pressure values predicted by the models with elements representing facet articulation were much higher than that predicated by models removing these elements. In the trunk flexion, the models with passive elements showed lower muscle activation of extensors than model with no passive elements. At the end of trunk flexion, extension, axial rotation and lateral bending, the intradiscal pressure values predicted by model with intact passive elements were 120.6%, 92.5%, 334.8% and 74.9% of the values predicted by model with no passive elements, respectively. CONCLUSIONS Caution must be taken while modeling facet articulation as elements with rotational stiffness, as they may lead to overestimation of intradiscal pressure in trunk axial rotation. The inclusion of ligaments as spring-like elements may improve the simulation of flexion-relaxation phenomenon in trunk flexion. Future models considering detailed properties of passive elements are needed to allow more access to understanding the mechanics of the lumbar spine.
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Affiliation(s)
- Kuan Wang
- Yangzhi Rehabilitation Hospital, Sunshine Rehabilitation Centre, Tongji University School of Medicine, Shanghai 201619, China; Department of Rehabilitation Sciences, Tongji University School of Medicine, Shanghai 200092, China
| | - Lejun Wang
- Sport and Health Research Center, Physical Education Department, Tongji University, Shanghai 200092, China
| | - Zhen Deng
- Baoshan Branch, Shuguang Hospital Affiliated to Shanghai University of TCM, Shanghai, China
| | - Chenghua Jiang
- Department of Rehabilitation Sciences, Tongji University School of Medicine, Shanghai 200092, China
| | - Wenxin Niu
- Department of Rehabilitation Sciences, Tongji University School of Medicine, Shanghai 200092, China.
| | - Ming Zhang
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China
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A chemo-mechanical model for osmo-inelastic effects in the annulus fibrosus. Biomech Model Mechanobiol 2019; 18:1773-1790. [DOI: 10.1007/s10237-019-01176-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 05/27/2019] [Indexed: 10/26/2022]
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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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Yuan D, Chen Z, Xiang X, Deng S, Liu K, Xiao D, Deng L, Feng G. The establishment and biological assessment of a whole tissue-engineered intervertebral disc with PBST fibers and a chitosan hydrogel in vitro and in vivo. J Biomed Mater Res B Appl Biomater 2019; 107:2305-2316. [PMID: 30680915 DOI: 10.1002/jbm.b.34323] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 12/29/2018] [Accepted: 01/02/2019] [Indexed: 12/27/2022]
Abstract
Intervertebral disc (IVD) degeneration (IDD) is the main cause of low back pain in the clinic. In the advanced stage of IDD, both cell transplantation and gene therapy have obvious limitations. At this stage, tissue-engineered IVDs (TE-IVDs) provide new hope for the treatment of this disease. We aimed to construct a TE-IVD with a relatively complete structure. The inner annulus fibrosus (AF) was constructed using poly (butylene succinate-co-terephthalate) copolyester (PBST) electrospun fibers, and the outer AF consisted of solid PBST. The nucleus pulposus (NP) scaffold was constructed using a chitosan hydrogel, as reported in our previous research. The three components were assembled in vitro, and the mechanical properties were analyzed. AF and NP cells were implanted on the corresponding scaffolds. Then, the cell-seeded scaffolds were implanted subcutaneously in nude mice and cultured for 4 weeks; then they were removed and implanted into New Zealand white rabbits. After 4 weeks, their properties were analyzed. The PBST outer AF provided mechanical support for the whole TE-IVD. The electrospun film and chitosan hydrogel simulated the natural structure of the IVD well. Its mechanical property could meet the requirement of the normal IVD. Four weeks later, X-ray and MR imaging examination results suggested that the height of the intervertebral space was retained. The cells on the TE-IVD expressed extracellular matrix, which indicated that the cells maintained their biological function. Therefore, we conclude that the whole TE-IVD has biological and biomechanical properties to some extent, which is a promising candidate for IVD replacement therapies. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2305-2316, 2019.
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Affiliation(s)
- Dechao Yuan
- Institute of Tissue Engineering and Stem Cells, Nanchong Central Hospital, The Second Clinical Medical College, North Sichuan Medical College, Nanchong, Sichuan, 637000, People's Republic of China.,Department of Orthopedics, Zigong No.4 People's Hospital, Zigong, Sichuan, 643000, People's Republic of China
| | - Zhu Chen
- Institute of Tissue Engineering and Stem Cells, Nanchong Central Hospital, The Second Clinical Medical College, North Sichuan Medical College, Nanchong, Sichuan, 637000, People's Republic of China
| | - Xiaocong Xiang
- Institute of Tissue Engineering and Stem Cells, Nanchong Central Hospital, The Second Clinical Medical College, North Sichuan Medical College, Nanchong, Sichuan, 637000, People's Republic of China
| | - Shang Deng
- Institute of Tissue Engineering and Stem Cells, Nanchong Central Hospital, The Second Clinical Medical College, North Sichuan Medical College, Nanchong, Sichuan, 637000, People's Republic of China
| | - Kang Liu
- Institute of Tissue Engineering and Stem Cells, Nanchong Central Hospital, The Second Clinical Medical College, North Sichuan Medical College, Nanchong, Sichuan, 637000, People's Republic of China
| | - Donqin Xiao
- Institute of Tissue Engineering and Stem Cells, Nanchong Central Hospital, The Second Clinical Medical College, North Sichuan Medical College, Nanchong, Sichuan, 637000, People's Republic of China
| | - Li Deng
- Institute of Tissue Engineering and Stem Cells, Nanchong Central Hospital, The Second Clinical Medical College, North Sichuan Medical College, Nanchong, Sichuan, 637000, People's Republic of China
| | - Gang Feng
- Institute of Tissue Engineering and Stem Cells, Nanchong Central Hospital, The Second Clinical Medical College, North Sichuan Medical College, Nanchong, Sichuan, 637000, People's Republic of China
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GAG content, fiber stiffness, and fiber angle affect swelling-based residual stress in the intact annulus fibrosus. Biomech Model Mechanobiol 2018; 18:617-630. [DOI: 10.1007/s10237-018-1105-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 11/29/2018] [Indexed: 12/16/2022]
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Emanuel KS, Mader KT, Peeters M, Kingma I, Rustenburg CME, Vergroesen PPA, Sammon C, Smit TH. Early changes in the extracellular matrix of the degenerating intervertebral disc, assessed by Fourier transform infrared imaging. Osteoarthritis Cartilage 2018; 26:1400-1408. [PMID: 29935308 DOI: 10.1016/j.joca.2018.06.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 05/09/2018] [Accepted: 06/07/2018] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Mechanical overloading induces a degenerative cell response in the intervertebral disc. However, early changes in the extracellular matrix (ECM) are challenging to assess with conventional techniques. Fourier Transform Infrared (FTIR) imaging allows visualization and quantification of the ECM. We aim to identify markers for disc degeneration and apply these to investigate early degenerative changes due to overloading and katabolic cell activity. DESIGN Three experiments were conducted; Exp 1.: In vivo, lumbar spines of seven goats were operated: one disc was injected with chondroitinase ABC [cABC (mild degeneration)] and compared to the adjacent disc (control) after 24 weeks. Exp 2a: Ex vivo, caprine discs received physiological loading (n = 10) or overloading (n = 10) in a bioreactor. Exp 2b: Cell activity was diminished prior to testing by freeze-thaw cycles, 18 discs were then tested as in Exp 2a. In all experiments, FTIR images (spectral region: 1000-1300 cm-1) of mid-sagittal slices were analyzed using multivariate curve resolution. RESULTS In vivo, FTIR was more sensitive than biochemical and histological analysis in identifying reduced proteoglycan content (P = 0.046) and increased collagen content in degenerated discs (P < 0.01). Notably, FTIR analysis additionally showed disorganization of the ECM, indicated by increased collagen entropy (P = 0.011). Ex vivo, the proteoglycan/collagen ratio decreased due to overloading (P = 0.047) and collagen entropy increased (P = 0.047). Cell activity affected collagen content only (P = 0.044). CONCLUSION FTIR imaging allows a more detailed investigation of early disc degeneration than traditional measures. Changes due to mild overloading could be assessed and quantified. Matrix remodeling is the first detectable step towards intervertebral disc degeneration.
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Affiliation(s)
- K S Emanuel
- Department of Orthopaedic Surgery, Academic Medical Center, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands; Department of Orthopedic Surgery, VU University Medical Center, Amsterdam Movement Sciences, The Netherlands.
| | - K T Mader
- Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield, UK.
| | - M Peeters
- Department of Orthopedic Surgery, VU University Medical Center, Amsterdam Movement Sciences, The Netherlands.
| | - I Kingma
- Department of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, The Netherlands.
| | - C M E Rustenburg
- Department of Orthopaedic Surgery, Academic Medical Center, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands; Department of Orthopedic Surgery, VU University Medical Center, Amsterdam Movement Sciences, The Netherlands.
| | - P-P A Vergroesen
- Department of Orthopedic Surgery, VU University Medical Center, Amsterdam Movement Sciences, The Netherlands; Department of Orthopaedic Surgery, NoordWest Ziekenhuisgroep, Alkmaar, The Netherlands.
| | - C Sammon
- Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield, UK.
| | - T H Smit
- Department of Orthopaedic Surgery, Academic Medical Center, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands; Department of Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands.
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Beekmans SV, Emanuel KS, Smit TH, Iannuzzi D. Stiffening of the nucleus pulposus upon axial loading of the intervertebral disc: An experimental in situ study. JOR Spine 2018; 1:e1005. [PMID: 31463437 PMCID: PMC6686818 DOI: 10.1002/jsp2.1005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 01/30/2018] [Accepted: 02/12/2018] [Indexed: 01/07/2023] Open
Abstract
Mechanical loading is inherently related to the function and degeneration of the intervertebral disc. We present a series of experiments aimed at measuring the effect of a loading/unloading cycle of the intervertebral disc on the mechanical properties of the nucleus pulposus. The study relies on our new minimally invasive microindenter, which allows us to quantify the storage and loss moduli of the nucleus pulposus by inserting an optomechanical probe in an intact (resected) intervertebral disk through the annulus fibrosis via a small needle. Our results indicate that, under the influence of compressive loading, the nucleus pulposus exhibits a more solid-like behavior.
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Affiliation(s)
- Steven V. Beekmans
- Department of Physics and AstronomyVrije Universiteit AmsterdamAmsterdamNetherlands
- LaserLab AmsterdamVrije Universiteit AmsterdamAmsterdamNetherlands
| | - Kaj S. Emanuel
- Department of Orthopaedic SurgeryVU University Medical Center (VUmc)AmsterdamNetherlands
- Amsterdam Movement SciencesVU University Medical Center (VUmc)AmsterdamNetherlands
| | - Theodoor H. Smit
- Department of Medical BiologyAcademic Medical Center (AMC)AmsterdamNetherlands
- Department of Orthopedic SurgeryAcademic Medical Center (AMC)AmsterdamNetherlands
| | - Davide Iannuzzi
- Department of Physics and AstronomyVrije Universiteit AmsterdamAmsterdamNetherlands
- LaserLab AmsterdamVrije Universiteit AmsterdamAmsterdamNetherlands
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