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Zhang Y, Pan Y, Mao X, He D, Zhang L, Cheng W, Zhu C, Zhu H, Zhang W, Jin H, Pan H, Wang D. Finite element model reveals the involvement of cartilage endplate in quasi-static biomechanics of intervertebral disc degeneration. Heliyon 2024; 10:e37524. [PMID: 39309961 PMCID: PMC11414571 DOI: 10.1016/j.heliyon.2024.e37524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Revised: 08/27/2024] [Accepted: 09/04/2024] [Indexed: 09/25/2024] Open
Abstract
Background and objective The intrinsic link between the compositional and structural attributes and the biomechanical functionality is evident in intervertebral discs. However, it remains unclear from a biomechanical perspective whether cartilage endplate (CEP) degeneration exacerbates intervertebral disc degeneration. Methods This study developed and quantitatively validated four biphasic swelling-based finite element models. We then applied four quasi-static tests and simulated daily loading scenarios to examine the effects of CEP degradation. Results Under free-swelling conditions, short-term responses were prevalent, with CEP performance changes not significantly impacting response proportionality. The creep test results showed the more than 50 % of the strain was attributed to long-term responses. Stress-relaxation testing indicated that all responses increased with disc degeneration, yet CEP degeneration's impact was minimal. Daily load analyses revealed that disc degeneration significantly reduces nucleus pulposus pressure and disc height, whereas CEP degeneration marginally increases nucleus pressure and slightly decreases disc height. Conclusions Glycosaminoglycan content and CEP permeability are critical to the fluid-dependent viscoelastic response of intervertebral discs. Our findings suggest that CEP contributes to disc degeneration under daily loading conditions.
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Affiliation(s)
- Yujun Zhang
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
| | - Yanli Pan
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
| | - Xinning Mao
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
| | - Du He
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
| | - Liangping Zhang
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
| | - Wei Cheng
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
- Department of Orthopaedics, Hangzhou Dingqiao Hospital, Huanding Road NO 1630, Hangzhou 310021, Zhejiang Province, China
| | - Chengyue Zhu
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
- Department of Orthopaedics, Hangzhou Dingqiao Hospital, Huanding Road NO 1630, Hangzhou 310021, Zhejiang Province, China
- Institute of Orthopaedics and Traumatology, Hangzhou Traditional Chinese Medicine Hospital Affiliated to Zhejiang Chinese Medical University, Tiyuchang Road NO 453, Hangzhou 310007, Zhejiang Province, China
| | - Hang Zhu
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
- Department of Orthopaedics, Hangzhou Dingqiao Hospital, Huanding Road NO 1630, Hangzhou 310021, Zhejiang Province, China
| | - Wei Zhang
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
- Department of Orthopaedics, Hangzhou Dingqiao Hospital, Huanding Road NO 1630, Hangzhou 310021, Zhejiang Province, China
| | - HongTing Jin
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
- Institute of Orthopaedics and Traumatology, The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, China
| | - Hao Pan
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
- Institute of Orthopaedics and Traumatology, Hangzhou Traditional Chinese Medicine Hospital Affiliated to Zhejiang Chinese Medical University, Tiyuchang Road NO 453, Hangzhou 310007, Zhejiang Province, China
| | - Dong Wang
- Department of Orthopaedics, Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University (Hangzhou Hospital of Traditional Chinese Medicine), Hangzhou 310000, Zhejiang Province, China
- Department of Orthopaedics, Hangzhou Dingqiao Hospital, Huanding Road NO 1630, Hangzhou 310021, Zhejiang Province, China
- Institute of Orthopaedics and Traumatology, Hangzhou Traditional Chinese Medicine Hospital Affiliated to Zhejiang Chinese Medical University, Tiyuchang Road NO 453, Hangzhou 310007, Zhejiang Province, China
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Hayward S, Keogh PS, Miles AW, Gheduzzi S. The effect of structural changes on the low strain rate behaviour of the intervertebral disc. Proc Inst Mech Eng H 2024; 238:851-864. [PMID: 39180367 PMCID: PMC11459866 DOI: 10.1177/09544119241272915] [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: 01/12/2024] [Accepted: 06/30/2024] [Indexed: 08/26/2024]
Abstract
The annuus fibrosus (AF) and nucleus pulposus (NP) of the intervertebral disc (IVD) work in conjunction to dissipate spinal loads. In this study we have isolated the contribution of the NP to the overall response of the disc and investigated the effect of extreme structural changes to the disc on the mechanical behaviour. Linear stiffness, overall load range, hysteresis area and total energy were used to evaluate the impact of these changes on the spine and surrounding structures. Six porcine lumbar isolated disc specimens were tested in 6 DOFs with a 400 N compressive axial preload at low strain rates in three conditions: intact (IN), after total nucleotomy (NN) and after the injection of bone cement into the nuclear void (SN). The latter two conditions, NN and SN, were chosen to emulate the effect of extreme changes to the NP on disc behaviour. When comparing with intact specimens, significant changes were noted primarily in axial compression-extension, mediolateral bending and flexion-extension. NN and SN cases demonstrated significant increases in linear stiffness, overall load range and total energy for mediolateral bending and flexion-extension compared to the intact (IN) state. SN also demonstrated a significant increase in total energy for axial compression-extension, and significant decreases in the elastic contribution to total energy in all axes except flexion-extension. These changes to total energy indicate that surrounding spinal structures would incur additional loading to produce the same motion in vivo after structural changes to the disc.
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Affiliation(s)
- Samantha Hayward
- Department of Mechanical Engineering, University of Bath, Bath, UK
| | - Patrick S Keogh
- Department of Mechanical Engineering, University of Bath, Bath, UK
| | - Anthony W Miles
- Department of Mechanical Engineering, University of Bath, Bath, UK
| | - Sabina Gheduzzi
- Department of Mechanical Engineering, University of Bath, Bath, 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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Rahman T, Baxan N, Murray RT, Tavana S, Schaer TP, Smith N, Bull J, Newell N. An in vitro comparison of three nucleus pulposus removal techniques for partial intervertebral disc replacement: An ultra-high resolution MRI study. JOR Spine 2023; 6:e1232. [PMID: 37361334 PMCID: PMC10285766 DOI: 10.1002/jsp2.1232] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 10/03/2022] [Indexed: 10/19/2023] Open
Abstract
Background Nuclectomy, also known as nucleotomy, is a percutaneous surgical procedure performed to remove nucleus material from the center of the disc. Multiple techniques have been considered to perform a nuclectomy, however, the advantages and disadvantages of each are not well understood. Aims This in vitro biomechanical investigation on human cadaveric specimens aimed to quantitatively compare three nuclectomy techniques performed using an automated shaver, rongeurs, and laser. Material & Methods Comparisons were made in terms of mass, volume and location of material removal, changes in disc height, and stiffness. Fifteen vertebra-disc-vertebra lumbar specimens were acquired from six donors (40 ± 13 years) and split into three groups. Before and after nucleotomy axial mechanical tests were performed and T2-weighted 9.4T MRIs were acquired for each specimen. Results When using the automated shaver and rongeurs similar volumes of disc material were removed (2.51 ± 1.10% and 2.76 ± 1.39% of the total disc volume, respectively), while considerably less material was removed using the laser (0.12 ± 0.07%). Nuclectomy using the automated shaver and rongeurs significantly reduced the toe-region stiffness (p = 0.036), while the reduction in the linear region stiffness was significant only for the rongeurs group (p = 0.011). Post-nuclectomy, 60% of the rongeurs group specimens showed changes in the endplate profile while 40% from the laser group showed subchondral marrow changes. Discussion From the MRIs, homogeneous cavities were seen in the center of the disc when using the automated shaver. When using rongeurs, material was removed non-homogeneously both from the nucleus and annulus regions. Laser ablation formed small and localized cavities suggesting that the technique is not suitable to remove large volumes of material unless it is developed and optimized for this application. Conclusion The results demonstrate that both rongeurs and automated shavers can be used to remove large volumes of NP material but the reduced risk of collateral damage to surrounding tissues suggests that the automated shaver may be more suitable.
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Affiliation(s)
- Tamanna Rahman
- Biomechanics Group, Department of Mechanical EngineeringImperial College LondonLondonUK
- Department of BioengineeringImperial College LondonLondonUK
| | - Nicoleta Baxan
- Biological Imaging Centre, Central Biomedical ServicesImperial College London, Hammersmith Hospital CampusLondonUK
| | - Robert T. Murray
- Femtosecond Optics Group, Blackett Laboratory, Department of PhysicsImperial College LondonLondonUK
| | - Saman Tavana
- Biomechanics Group, Department of Mechanical EngineeringImperial College LondonLondonUK
- Department of BioengineeringImperial College LondonLondonUK
| | - Thomas P. Schaer
- Department of Clinical Studies, School of Veterinary Medicine, New Bolton CenterUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Nigel Smith
- Division of Surgery and Interventional ScienceUniversity College LondonStanmoreUK
| | - Jonathan Bull
- Department of NeurosurgeryBARTS Health NHS TrustLondonUK
| | - Nicolas Newell
- Department of BioengineeringImperial College LondonLondonUK
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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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Techens C, Montanari S, Bereczki F, Eltes PE, Lazary A, Cristofolini L. Biomechanical consequences of cement discoplasty: An in vitro study on thoraco-lumbar human spines. Front Bioeng Biotechnol 2022; 10:1040695. [PMID: 36532589 PMCID: PMC9755512 DOI: 10.3389/fbioe.2022.1040695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 11/23/2022] [Indexed: 10/24/2023] Open
Abstract
With the ageing of the population, there is an increasing need for minimally invasive spine surgeries to relieve pain and improve quality of life. Percutaneous Cement Discoplasty is a minimally invasive technique to treat advanced disc degeneration, including vacuum phenomenon. The present study aimed to develop an in vitro model of percutaneous cement discoplasty to investigate its consequences on the spine biomechanics in comparison with the degenerated condition. Human spinal segments (n = 27) were tested at 50% body weight in flexion and extension. Posterior disc height, range of motion, segment stiffness, and strains were measured using Digital Image Correlation. The cement distribution was also studied on CT scans. As main result, percutaneous cement discoplasty restored the posterior disc height by 41% for flexion and 35% for extension. Range of motion was significantly reduced only in flexion by 27%, and stiffness increased accordingly. The injected cement volume was 4.56 ± 1.78 ml (mean ± SD). Some specimens (n = 7) exhibited cement perforation of one endplate. The thickness of the cement mass moderately correlated with the posterior disc height and range of motion with different trends for flexions vs. extension. Finally, extreme strains on the discs were reduced by percutaneous cement discoplasty, with modified patterns of the distribution. To conclude, this study supported clinical observations in term of recovered disc height close to the foramen, while percutaneous cement discoplasty helped stabilize the spine in flexion and did not increase the risk of tissue damage in the annulus.
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Affiliation(s)
- Chloé Techens
- Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum—Università di Bologna, Bologna, Italy
- In Silico Biomechanics Laboratory, National Center for Spinal Disorders, Buda Health Center, Budapest, Hungary
- Department of Spinal Surgery, Department of Orthopaedics, Semmelweis University, Budapest, Hungary
| | - Sara Montanari
- Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum—Università di Bologna, Bologna, Italy
| | - Ferenc Bereczki
- In Silico Biomechanics Laboratory, National Center for Spinal Disorders, Buda Health Center, Budapest, Hungary
- School of PhD Studies, Semmelweis University, Budapest, Hungary
| | - Peter Endre Eltes
- In Silico Biomechanics Laboratory, National Center for Spinal Disorders, Buda Health Center, Budapest, Hungary
- Department of Spinal Surgery, Department of Orthopaedics, Semmelweis University, Budapest, Hungary
| | - Aron Lazary
- In Silico Biomechanics Laboratory, National Center for Spinal Disorders, Buda Health Center, Budapest, Hungary
- Department of Spinal Surgery, Department of Orthopaedics, Semmelweis University, Budapest, Hungary
| | - Luca Cristofolini
- Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum—Università di Bologna, Bologna, Italy
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Whittal MC, Poynter SJ, Samms K, Briar KJ, Sinopoli SI, Millecamps M, Stone LS, DeWitte-Orr SJ, Gregory DE. TAK-242 treatment and its effect on mechanical properties and gene expression associated with IVD degeneration in SPARC-null mice. 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 2022; 31:2801-2811. [PMID: 35816198 DOI: 10.1007/s00586-022-07310-y] [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: 01/10/2022] [Revised: 05/09/2022] [Accepted: 06/24/2022] [Indexed: 06/15/2023]
Abstract
PURPOSE Intervertebral disc (IVD) degeneration is accompanied by mechanical and gene expression changes to IVDs. SPARC-null mice display accelerated IVD degeneration, and treatment with (toll-like receptor 4 (TLR4) inhibitor) TAK-242 decreases proinflammatory cytokines and pain. This study examined if chronic TAK-242 treatment impacts mechanical properties and gene expression associated with IVD degeneration in SPARC-null mice. METHODS Male and female SPARC-null and WT mice aged 7-9 months were given intraperitoneal injections with TAK-242 or an equivalent saline vehicle for 8 weeks (3x/per week, M-W-F). L2-L5 spinal segments were tested in cyclic axial tension and compression. Gene expression analysis (RT-qPCR) was performed on male IVD tissues using Qiagen RT2 PCR arrays. RESULTS SPARC-null mice had decreased NZ length (p = 0.001) and increased NZ stiffness (p < 0.001) compared to WT mice. NZ length was not impacted by TAK-242 treatment (p = 0.967) despite increased hysteresis energy (p = 0.024). Tensile stiffness was greater in SPARC-null mice (p = 0.018), and compressive (p < 0.001) stiffness was reduced from TAK-242 treatment in WT but not SPARC-null mice (p = 0.391). Gene expression analysis found upregulation of 13 ECM and 5 inflammatory genes in SPARC-null mice, and downregulation of 2 inflammatory genes after TAK-242 treatment. CONCLUSIONS TAK-242 had limited impacts on SPARC-null mechanical properties and did not attenuate NZ mechanical changes associated with IVD degeneration. Expression analysis revealed an increase in ECM and inflammatory gene expression in SPARCnull mice with a reduction in inflammatory expression due to TAK-242 treatment. This study provides insight into the role of TLR4 in SPARC-null mediated IVD degeneration.
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Affiliation(s)
- Mitchel C Whittal
- Department of Kinesiology and Physical Education, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON, N2L 3C5, Canada
| | - Sarah J Poynter
- Department of Health Sciences, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON, N2L 3C5, Canada
| | - Kayla Samms
- Department of Health Sciences, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON, N2L 3C5, Canada
| | - K Josh Briar
- Department of Kinesiology and Physical Education, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON, N2L 3C5, Canada
| | - Sabrina I Sinopoli
- Department of Kinesiology and Physical Education, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON, N2L 3C5, Canada
| | - Magali Millecamps
- McGill University, 845 Sherbrooke Street West, Montréal, QC, H3A 0G4, Canada
| | - Laura S Stone
- McGill University, 845 Sherbrooke Street West, Montréal, QC, H3A 0G4, Canada
- University of Minnesota, 321 Church Street SE, Minneapolis, MN, 55455, USA
| | - Stephanie J DeWitte-Orr
- Department of Health Sciences, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON, N2L 3C5, Canada
| | - Diane E Gregory
- Department of Kinesiology and Physical Education, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON, N2L 3C5, Canada.
- Department of Health Sciences, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON, N2L 3C5, Canada.
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Ex vivo biomechanical evaluation of Acute lumbar endplate injury and comparison to annulus fibrosus injury in a rat model. J Mech Behav Biomed Mater 2022; 131:105234. [DOI: 10.1016/j.jmbbm.2022.105234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 03/14/2022] [Accepted: 04/09/2022] [Indexed: 11/20/2022]
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9
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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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Christiani T, Mys K, Dyer K, Kadlowec J, Iftode C, Vernengo AJ. Using embedded alginate microparticles to tune the properties of in situ forming poly( N-isopropylacrylamide)-graft-chondroitin sulfate bioadhesive hydrogels for replacement and repair of the nucleus pulposus of the intervertebral disc. JOR Spine 2021; 4:e1161. [PMID: 34611588 PMCID: PMC8479524 DOI: 10.1002/jsp2.1161] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 04/16/2021] [Accepted: 05/12/2021] [Indexed: 12/25/2022] Open
Abstract
Low back pain is a major public health issue associated with degeneration of the intervertebral disc (IVD). The early stages of degeneration are characterized by the dehydration of the central, gelatinous portion of the IVD, the nucleus pulposus (NP). One possible treatment approach is to replace the NP in the early stages of IVD degeneration with a hydrogel that restores healthy biomechanics while supporting tissue regeneration. The present study evaluates a novel thermosensitive hydrogel based on poly(N-isopropylacrylamide-graft-chondroitin sulfate) (PNIPAAM-g-CS) for NP replacement. The hypothesis was tested that the addition of freeze-dried, calcium crosslinked alginate microparticles (MPs) to aqueous solutions of PNIPAAm-g-CS would enable tuning of the rheological properties of the injectable solution, as well as the bioadhesive and mechanical properties of the thermally precipitated composite gel. Further, we hypothesized that the composite would support encapsulated cell viability and differentiation. Structure-material property relationships were evaluated by varying MP concentration and diameter. The addition of high concentrations (50 mg/mL) of small MPs (20 ± 6 μm) resulted in the greatest improvement in injectability, compressive mechanical properties, and bioadhesive strength of PNIPAAm-g-CS. This combination of PNIPAAM-g-CS and alginate MPs supported the survival, proliferation, and differentiation of adipose derived mesenchymal stem cells toward an NP-like phenotype in the presence of soluble GDF-6. When implanted ex vivo into the intradiscal cavity of degenerated porcine IVDs, the formulation restored the compressive and neutral zone stiffnesses to intact values and resisted expulsion under lateral bending. Overall, results indicate the potential of the hydrogel composite to serve as a scaffold for supporting NP regeneration. This work uniquely demonstrates that encapsulation of re-hydrating polysaccharide-based MPs may be an effective method for improving key functional properties of in situ forming hydrogels for orthopedic tissue engineering applications.
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Affiliation(s)
- Thomas Christiani
- Department of Biomedical Engineering, Rowan UniversityGlassboroNew JerseyUSA
| | - Karen Mys
- AO Research Institute DavosDavosSwitzerland
| | - Karl Dyer
- Department of Mechanical Engineering, Rowan UniversityGlassboroNew JerseyUSA
| | - Jennifer Kadlowec
- Department of Computer Science and Engineering, Baldwin Wallace UniversityBereaOhioUSA
| | - Cristina Iftode
- Department of Molecular and Cellular Biosciences, Rowan UniversityGlassboroNew JerseyUSA
| | - Andrea Jennifer Vernengo
- Department of Biomedical Engineering, Rowan UniversityGlassboroNew JerseyUSA
- AO Research Institute DavosDavosSwitzerland
- Department of Chemical Engineering, Rowan UniversityGlassboroNew JerseyUSA
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11
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Li J, Xu C, Zhang X, Xi Z, Liu M, Fang Z, Wang N, Xie L, Song Y. TELD with limited foraminoplasty has potential biomechanical advantages over TELD with large annuloplasty: an in-silico study. BMC Musculoskelet Disord 2021; 22:616. [PMID: 34246272 PMCID: PMC8272903 DOI: 10.1186/s12891-021-04504-1] [Citation(s) in RCA: 15] [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: 04/16/2021] [Accepted: 06/17/2021] [Indexed: 02/07/2023] Open
Abstract
Background Facetectomy, an important procedure in the in–out and out–in techniques of transforaminal endoscopic lumbar discectomy (TELD), is related to the deterioration of the postoperative biomechanical environment and poor prognosis. Facetectomy may be avoided in TELD with large annuloplasty, but iatrogenic injury of the annulus and a high grade of nucleotomy have been reported as risk factors influencing poor prognosis. These risk factors may be alleviated in TELD with limited foraminoplasty, and the grade of facetectomy in this surgery can be reduced by using an endoscopic dynamic drill. Methods An intact lumbo-sacral finite element (FE) model and the corresponding model with adjacent segment degeneration were constructed and validated to evaluate the risk of biomechanical deterioration and related postoperative complications of TELD with large annuloplasty and TELD with limited foraminoplasty. Changes in various biomechanical indicators were then computed to evaluate the risk of postoperative complications in the surgical segment. Results Compared with the intact FE models, the model of TELD with limited foraminoplasty demonstrated slight biomechanical deterioration, whereas the model of TELD with large annuloplasty revealed obvious biomechanical deterioration. Degenerative changes in adjacent segments magnified, rather than altered, the overall trends of biomechanical change. Conclusions TELD with limited foraminoplasty presents potential biomechanical advantages over TELD with large annuloplasty. Iatrogenic injury of the annulus and a high grade of nucleotomy are risk factors for postoperative biomechanical deterioration and complications of the surgical segment.
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Affiliation(s)
- Jingchi Li
- Department of Orthopedic Surgery and Orthopedic Research Institute, West China Hospital/West China School of Medicine for Sichuan University, 37# Wuhou Guoxue road, Chengdu, Sichuan Province, 610041, P.R. China
| | - Chen Xu
- Department of Spine Surgery, Changzheng Hospital Affiliated to the Naval Medical University, Shanghai, 200041, China
| | - Xiaoyu Zhang
- Department of Spine Surgery, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine for Nanjing University of Chinese Medicine, Nanjing, Jiangsu Province, 210028, P.R. China
| | - Zhipeng Xi
- Department of Spine Surgery, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine for Nanjing University of Chinese Medicine, Nanjing, Jiangsu Province, 210028, P.R. China
| | - Mengnan Liu
- Macau University of Science and Technology, Macau, 999078, China
| | - Zhongxin Fang
- Fluid and Power Machinery Key Laboratory of Ministry of Education, Xihua University, Chengdu, 610039, China
| | - Nan Wang
- Department of Spine Surgery, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine for Nanjing University of Chinese Medicine, Nanjing, Jiangsu Province, 210028, P.R. China
| | - Lin Xie
- Department of Spine Surgery, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine for Nanjing University of Chinese Medicine, Nanjing, Jiangsu Province, 210028, P.R. China.
| | - Yueming Song
- Department of Orthopedic Surgery and Orthopedic Research Institute, West China Hospital/West China School of Medicine for Sichuan University, 37# Wuhou Guoxue road, Chengdu, Sichuan Province, 610041, P.R. China.
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12
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Costi JJ, Ledet EH, O'Connell GD. Spine biomechanical testing methodologies: The controversy of consensus vs scientific evidence. JOR Spine 2021; 4:e1138. [PMID: 33778410 PMCID: PMC7984003 DOI: 10.1002/jsp2.1138] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 12/14/2022] Open
Abstract
Biomechanical testing methodologies for the spine have developed over the past 50 years. During that time, there have been several paradigm shifts with respect to techniques. These techniques evolved by incorporating state-of-the-art engineering principles, in vivo measurements, anatomical structure-function relationships, and the scientific method. Multiple parametric studies have focused on the effects that the experimental technique has on outcomes. As a result, testing methodologies have evolved, but there are no standard testing protocols, which makes the comparison of findings between experiments difficult and conclusions about in vivo performance challenging. In 2019, the international spine research community was surveyed to determine the consensus on spine biomechanical testing and if the consensus opinion was consistent with the scientific evidence. More than 80 responses to the survey were received. The findings of this survey confirmed that while some methods have been commonly adopted, not all are consistent with the scientific evidence. This review summarizes the scientific literature, the current consensus, and the authors' recommendations on best practices based on the compendium of available evidence.
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Affiliation(s)
- John J. Costi
- Biomechanics and Implants Research Group, Medical Device Research Institute, College of Science and EngineeringFlinders UniversityAdelaideAustralia
| | - Eric H. Ledet
- Department of Biomedical EngineeringRensselaer Polytechnic InstituteTroyNew YorkUSA
- Research and Development ServiceStratton VA Medical CenterAlbanyNew YorkUSA
| | - Grace D. O'Connell
- Department of Mechanical EngineeringUniversity of California‐BerkeleyBerkeleyCaliforniaUSA
- Department of Orthopaedic SurgeryUniversity of California‐San FranciscoSan FranciscoCaliforniaUSA
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13
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Whittal MC, Molladavoodi S, Zwambag DP, Millecamps M, Stone LS, Gregory DE. Mechanical Consequence of Induced Intervertebral Disc Degeneration in the SPARC-Null Mouse. J Biomech Eng 2021; 143:024501. [PMID: 32734296 DOI: 10.1115/1.4047995] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Indexed: 11/08/2022]
Abstract
Intervertebral disc (IVD) degeneration is associated with low back pain (LBP) and accompanied by mechanical changes to the spine. Secreted protein acidic and rich in cysteine (SPARC) is a protein that contributes to the functioning and maintenance of the extracellular matrix. SPARC-null mice display accelerated IVD degeneration and pain-associated behaviors. This study examined if SPARC-null mice also display altered spine mechanics as compared to wild-type (WT) mice. Lumbar spines from SPARC-null (n = 36) and WT (n = 18) mice aged 14-25 months were subjected to cyclic axial tension and compression to determine neutral zone (NZ) length and stiffness. Three separate mechanical tests were completed for each spine to determine the effect of the number of IVDs tested in series (one versus two versus three IVDs). SPARC-null spine NZs were both stiffer (p < 0.001) and smaller in length (p < 0.001) than WT spines. There was an effect of the number of IVDs tested in series for NZ length but not NZ stiffness when collapsed across condition (SPARC-null and WT). Correlation analysis revealed a weak negative correlation (r = -0.24) between age and NZ length in SPARC-null mice and a weak positive correlation (r = 0.30) between age and NZ stiffness in WT mice. In conclusion, SPARC-null mice had stiffer and smaller NZs than WT mice, regardless of the number of IVDs in series being tested. The increased stiffness of these IVDs likely influences mobility at these spinal joints thereby potentially contributing to low back pain.
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Affiliation(s)
- Mitchel C Whittal
- Department of Kinesiology and Physical Education, Wilfrid Laurier University, 75 University Avenue W, Waterloo, ON N2 L 3C5, Canada
| | - Sara Molladavoodi
- Department of Kinesiology and Physical Education, Wilfrid Laurier University, 75 University Avenue W, Waterloo, ON N2 L 3C5, Canada
| | - Derek P Zwambag
- Department of Kinesiology and Physical Education, Wilfrid Laurier University, 75 University Avenue W, Waterloo, ON N2 L 3C5, Canada
| | - Magali Millecamps
- Faculty of Dentistry, McGill University, 845 Sherbrooke Street West, Montréal, QC H3A 0G4, Canada
| | - Laura S Stone
- Faculty of Dentistry, McGill University, 845 Sherbrooke Street West, Montréal, QC H3A 0G4, Canada
| | - Diane E Gregory
- Department of Kinesiology and Physical Education/Department of Health Sciences, Wilfrid Laurier University, 75 University Avenue W, Waterloo, ON N2 L 3C5, Canada
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14
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Wang C, Shi Z. [Research progress in creep characteristics of lumbar intervertebral disc]. ZHONGGUO XIU FU CHONG JIAN WAI KE ZA ZHI = ZHONGGUO XIUFU CHONGJIAN WAIKE ZAZHI = CHINESE JOURNAL OF REPARATIVE AND RECONSTRUCTIVE SURGERY 2020; 34:1624-1629. [PMID: 33319547 DOI: 10.7507/1002-1892.202002167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Objective To summarize the research progress in creep characteristics of lumbar intervertebral disc. Methods The relevant literature at home and abroad was systematically searched. Then, the concept and structural basis of lumbar disc creep, the description of creep characteristics, and the latest progress of its influencing factors were summarized and analyzed. Results The intervertebral disc is viscoelastic. After loading, the deformation increases with time. However, the degree of increase is not linear with time. That is creep, which plays an important role in buffering the load generated by human activities and absorbing energy in order to maintain stable movement of the spine. Both experimental and simulation studies can well describe the creep behavior of intervertebral disc. Various models including standard linear solid model and corresponding constitutive equations can quantify and compare the creep characteristics, which can be obviously changed by the degeneration of intervertebral disc and the mode of loading stress. Conclusion Creep is an important mechanical properties of intervertebral discs, and an in-depth understanding of the creep characteristics of lumbar intervertebral discs is of great guiding significance for the intervention and treatment of low back pain.
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Affiliation(s)
- Chao Wang
- Department of Spine Surgery, Changhai Hospital Affiliated to Naval Medical University, Shanghai, 200433, P.R.China
| | - Zhicai Shi
- Department of Spine Surgery, Changhai Hospital Affiliated to Naval Medical University, Shanghai, 200433, P.R.China
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15
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Borem R, Walters J, Madeline A, Madeline L, Gill S, Easley J, Mercuri J. Characterization of chondroitinase-induced lumbar intervertebral disc degeneration in a sheep model intended for assessing biomaterials. J Biomed Mater Res A 2020; 109:1232-1246. [PMID: 33040470 DOI: 10.1002/jbm.a.37117] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 10/04/2020] [Accepted: 10/09/2020] [Indexed: 02/06/2023]
Abstract
Intervertebral disc (IVD) degeneration (IVDD) leads to structural and functional changes. Biomaterials for restoring IVD function and promoting regeneration are currently being investigated; however, such approaches require validation using animal models that recapitulate clinical, biochemical, and biomechanical hallmarks of the human pathology. Herein, we comprehensively characterized a sheep model of chondroitinase-ABC (ChABC) induced IVDD. Briefly, ChABC (1 U) was injected into the L1/2 , L2/3 , and L3/4 IVDs. Degeneration was assessed via longitudinal magnetic resonance (MR) and radiographic imaging. Additionally, kinematic, biochemical, and histological analyses were performed on explanted functional spinal units (FSUs). At 17-weeks, ChABC treated IVDs demonstrated significant reductions in MR index (p = 0.030) and disc height (p = 0.009) compared with pre-operative values. Additionally, ChABC treated IVDs exhibited significantly increased creep displacement (p = 0.004) and axial range of motion (p = 0.007) concomitant with significant decreases in tensile (p = 0.034) and torsional (p = 0.021) stiffnesses and long-term viscoelastic properties (p = 0.016). ChABC treated IVDs also exhibited a significant decrease in NP glycosaminoglycan: hydroxyproline ratio (p = 0.002) and changes in microarchitecture, particularly in the NP and endplates, compared with uninjured IVDs. Taken together, this study demonstrated that intradiscal injection of ChABC induces significant degeneration in sheep lumbar IVDs and the potential for using this model in evaluating biomaterials for IVD repair, regeneration, or fusion.
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Affiliation(s)
- Ryan Borem
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, South Carolina, USA
| | - Joshua Walters
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, South Carolina, USA
| | - Allison Madeline
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, South Carolina, USA
| | - Lee Madeline
- Department of Radiology, Greenville Health System, Greenville, South Carolina, USA
| | - Sanjitpal Gill
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, South Carolina, USA.,Department of Orthopaedic Surgery, Medical Group of the Carolinas-Pelham, Spartanburg Regional Healthcare System, Greer, South Carolina, USA
| | - Jeremiah Easley
- Preclinical Surgical Research Laboratory, Colorado State University, Fort Collins, Colorado, USA
| | - Jeremy Mercuri
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, South Carolina, USA
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16
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Techens C, Palanca M, Éltes PE, Lazáry Á, Cristofolini L. Testing the impact of discoplasty on the biomechanics of the intervertebral disc with simulated degeneration: An in vitro study. Med Eng Phys 2020; 84:51-59. [PMID: 32977922 DOI: 10.1016/j.medengphy.2020.07.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 07/21/2020] [Accepted: 07/26/2020] [Indexed: 11/18/2022]
Abstract
Percutaneous Cement Discoplasty has recently been developed to relieve pain in highly degenerated intervertebral discs presenting a vacuum phenomenon in patients that cannot undergo major surgery. Little is currently known about the biomechanical effects of discoplasty. This study aimed at investigating the feasibility of modelling empty discs and subsequent discoplasty surgery and measuring their impact over the specimen geometry and mechanical behaviour. Ten porcine lumbar spine segments were tested in flexion, extension, and lateral bending under 5.4 Nm (with a 200 N compressive force and a 27 mm offset). Tests were performed in three conditions for each specimen: with intact disc, after nucleotomy and after discoplasty. A 3D Digital Image Correlation (DIC) system was used to measure the surface displacements and strains. The posterior disc height, range of motion (ROM), and stiffness were measured at the peak load. CT scans were performed to confirm that the cement distribution was acceptable. Discoplasty recovered the height loss caused by nucleotomy (p = 0.04) with respect to the intact condition, but it did not impact significantly either the ROM or the stiffness. The strains over the disc surface increased after nucleotomy, while discoplasty concentrated the strains on the endplates. In conclusion, this preliminary study has shown that discoplasty recovered the intervertebral posterior height, opening the neuroforamen as clinically observed, but it did not influence the spine mobility or stiffness. This study confirms that this in vitro approach can be used to investigate discoplasty.
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Affiliation(s)
- Chloé Techens
- Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum - Università di Bologna, Viale Risorgimento, 2, Bologna 40136, Italy
| | - Marco Palanca
- Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum - Università di Bologna, Viale Risorgimento, 2, Bologna 40136, Italy
| | - Peter Endre Éltes
- R&D Department of National Center for Spinal Disorders, Budapest, Hungary
| | - Áron Lazáry
- R&D Department of National Center for Spinal Disorders, Budapest, Hungary
| | - Luca Cristofolini
- Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum - Università di Bologna, Viale Risorgimento, 2, Bologna 40136, Italy.
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Stadelmann MA, Stocker R, Maquer G, Hoppe S, Vermathen P, Alkalay RN, Zysset PK. Finite element models can reproduce the effect of nucleotomy on the multi-axial compliance of human intervertebral discs. Comput Methods Biomech Biomed Engin 2020; 23:934-944. [PMID: 32543225 DOI: 10.1080/10255842.2020.1773808] [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] [Indexed: 01/07/2023]
Abstract
Finite element (FE) models can unravel the link between intervertebral disc (IVD) degeneration and its mechanical behaviour. Nucleotomy may provide the data required for model verification. Three human IVDs were scanned with MRI and tested in multiple loading scenarios, prior and post nucleotomy. The resulting data was used to generate, calibrate, and verify the FE models. Nucleotomy increased the experimental range of motion by 26%, a result reproduced by the FE simulation within a 5% error. This work demonstrates the ability of FE models to reproduce the mechanical compliance of human IVDs prior and post nucleotomy.
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Affiliation(s)
- Marc A Stadelmann
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
| | - Roland Stocker
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
| | - Ghislain Maquer
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
| | - Sven Hoppe
- Department of Orthopedic Surgery, Bern University Hospital, Bern, Switzerland
| | - Peter Vermathen
- Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Ron N Alkalay
- Center for Advanced Orthopedic Studies, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Philippe K Zysset
- Department of Orthopedic Surgery, Bern University Hospital, Bern, Switzerland
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18
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Borem R, Madeline A, Vela R, Gill S, Mercuri J. Multi-laminate annulus fibrosus repair scaffold with an interlamellar matrix enhances impact resistance, prevents herniation and assists in restoring spinal kinematics. J Mech Behav Biomed Mater 2019; 95:41-52. [PMID: 30953808 PMCID: PMC6510600 DOI: 10.1016/j.jmbbm.2019.03.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 03/03/2019] [Accepted: 03/29/2019] [Indexed: 12/19/2022]
Abstract
Focal defects in the annulus fibrosus (AF) of the intervertebral disc (IVD) arising from herniation have detrimental impacts on the IVD's mechanical function. Thus, biomimetic-based repair strategies must restore the mechanical integrity of the AF to help support and restore native spinal loading and motion. Accordingly, an annulus fibrosus repair patch (AFRP); a collagen-based multi-laminate scaffold with an angle-ply architecture has been previously developed, which demonstrates similar mechanical properties to native outer AF (oAF). To further enhance the mimetic nature of the AFRP, interlamellar (ILM) glycosaminoglycan (GAG) was incorporated into the scaffolds. The ability of the scaffolds to withstand simulated impact loading and resist herniation of native IVD tissue while contributing to the restoration of spinal kinematics were assessed separately. The results demonstrate that incorporation of a GAG-based ILM significantly increased (p < 0.001) the impact strength of the AFRP (2.57 ± 0.04 MPa) compared to scaffolds without (1.51 ± 0.13 MPa). Additionally, repair of injured functional spinal units (FSUs) with an AFRP in combination with sequestering native NP tissue and a full-thickness AF tissue plug enabled the restoration of creep displacement (p = 0.134), short-term viscous damping coefficient (p = 0.538), the long-term viscous (p = 0.058) and elastic (p = 0.751) damping coefficients, axial neutral zone (p = 0.908), and axial range of motion (p = 0.476) to an intact state. Lastly, the AFRP scaffolds were able to prevent native IVD tissue herniation upon application of supraphysiologic loads (5.28 ± 1.24 MPa). Together, these results suggest that the AFRP has the strength to sequester native NP and AF tissue and/or implants, and thus, can be used in a composite repair strategy for IVDs with focal annular defects thereby assisting in the restoration of spinal kinematics.
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Affiliation(s)
- Ryan Borem
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, SC, USA
| | - Allison Madeline
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, SC, USA
| | - Ricardo Vela
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, SC, USA
| | - Sanjitpal Gill
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, SC, USA; Department of Orthopaedic Surgery, Medical Group of the Carolinas-Pelham, Spartanburg Regional Healthcare System, Greer, SC, USA
| | - Jeremy Mercuri
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, SC, USA.
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19
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Biomechanical test protocols to detect minor injury effects in intervertebral discs. J Mech Behav Biomed Mater 2019; 95:13-20. [PMID: 30947120 DOI: 10.1016/j.jmbbm.2019.03.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 02/26/2019] [Accepted: 03/22/2019] [Indexed: 01/21/2023]
Abstract
Intervertebral discs (IVDs) maintain flexibility of the spine and bear mechanical load. Annulus fibrosus (AF) defects are associated with IVD degeneration and herniation which disrupt biomechanical function and can cause pain. AF puncture injuries can induce IVD degeneration but are needed to inject therapies. Identifying small AF defects with biomechanical testing can be difficult because IVDs have a complex, composite structure and nonlinear biomechanical properties that are dependent on AF fiber tension. It remains unclear how choice of biomechanical testing protocols affect the sensitivity of biomechanical properties to AF injuries. This study determined whether axial preload or magnitude of cyclic axial or torsional testing affected the ability to detect minor AF defects in rat caudal motion segments using ex vivo biomechanical testing. Intact and injured motion segments were subjected to a repeated measures study design with multiple biomechanical testing protocols that varied axial tension-compression force amplitude (±1.6 N, ±8.0 N, ±16.0 N), axial preload (-1.6 N, -8.0 N, -16.0 N, corresponding to -0.1 MPa, -0.5 MPa, and -1.0 MPa, respectively), and torsional rotation angle (±10°, ±15°, and ±20°). Biomechanical properties obtained from the lowest force testing conditions for axial tension-compression (±1.6 N), axial preload (-1.6 N), and angular rotation (±10°) exhibited the largest differences in biomechanical properties between intact and injured conditions. Biomechanical properties determined under low axial force or torsion amplitudes involve less AF fiber tension and were most sensitive to injury. Low force testing protocols are recommended for detecting minor structural AF defects and may enable more precise assessments of IVD injuries, healing or repair.
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Ji ML, Jiang H, Zhang XJ, Shi PL, Li C, Wu H, Wu XT, Wang YT, Wang C, Lu J. Preclinical development of a microRNA-based therapy for intervertebral disc degeneration. Nat Commun 2018; 9:5051. [PMID: 30487517 PMCID: PMC6262020 DOI: 10.1038/s41467-018-07360-1] [Citation(s) in RCA: 170] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 10/22/2018] [Indexed: 12/13/2022] Open
Abstract
Understanding the molecular mechanisms regulating the maintenance and destruction of intervertebral disc may lead to the development of new therapies for intervertebral disc degeneration (IDD). Here we present evidence from miRNA microarray analyses of clinical data sets along with in vitro and in vivo experiments that miR-141 is a key regulator of IDD. Gain- and loss-of-function studies show that miR-141 drives IDD by inducing nucleus pulposus (NP) apoptosis. Furthermore, miR-141 KO in mice attenuated spontaneous and surgically induced IDD. Mechanistically, miR-141 promotes IDD development by targeting and depleting SIRT1, a negative regulator of NF-κB pathway. Therapeutically, upregulation or downregulation of miR-141 by nanoparticle delivery in IDD model aggravated or alleviated experimental IDD, respectively. Our findings reveal a novel mechanism by which miR-141, in part, promotes IDD progression by interacting with SIRT1/NF-κB pathway. Blockade of miR-141 in vivo may serve as a potential therapeutic approach in the treatment of IDD. Intervertebral disk degeneration (IDD) is characterized by changes in the nucleus pulposus (NP) extra cellular matrix that compromise disk structural integrity. In a miRNA screen of human IDD patient NP tissue, the authors identify deregulated miR-141 and show that direct injection of nanoparticle-coupled miR-141 into the NP alleviates IDD in mice.
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Affiliation(s)
- Ming-Liang Ji
- Department of Orthopaedic Surgery, Zhongda Hospital, School of Medicine, Southeast University, 210009, Nanjing, China
| | - Hua Jiang
- Department of Spine Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530000, China
| | - Xue-Jun Zhang
- Department of Orthopaedic Surgery, Zhongda Hospital, School of Medicine, Southeast University, 210009, Nanjing, China
| | - Pei-Liang Shi
- Key Laboratory of Model Animal for Disease Study of Ministry of Education, Model Animal Research Center, Collaborative Innovation Center of Genetics and Development, Nanjing University, Nanjing, 210093, China
| | - Chao Li
- Department of Orthopaedic Surgery, Zhongda Hospital, School of Medicine, Southeast University, 210009, Nanjing, China
| | - Hao Wu
- Department of Orthopaedic Surgery, Zhongda Hospital, School of Medicine, Southeast University, 210009, Nanjing, China
| | - Xiao-Tao Wu
- Department of Orthopaedic Surgery, Zhongda Hospital, School of Medicine, Southeast University, 210009, Nanjing, China
| | - Yun-Tao Wang
- Department of Orthopaedic Surgery, Zhongda Hospital, School of Medicine, Southeast University, 210009, Nanjing, China
| | - Chen Wang
- Department of Orthopaedic Surgery, Zhongda Hospital, School of Medicine, Southeast University, 210009, Nanjing, China
| | - Jun Lu
- Department of Orthopaedic Surgery, Zhongda Hospital, School of Medicine, Southeast University, 210009, Nanjing, China.
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Varma DM, Lin HA, Long RG, Gold GT, Hecht AC, Iatridis JC, Nicoll SB. Thermoresponsive, redox-polymerized cellulosic hydrogels undergo in situ gelation and restore intervertebral disc biomechanics post discectomy. Eur Cell Mater 2018; 35:300-317. [PMID: 29845998 PMCID: PMC6016390 DOI: 10.22203/ecm.v035a21] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Back and neck pain are commonly associated with intervertebral disc (IVD) degeneration. Structural augmentation of diseased nucleus pulposus (NP) tissue with biomaterials could restore degeneration-related IVD height loss and degraded biomechanical behaviors; however, effective NP replacement biomaterials are not commercially available. This study developed a novel, crosslinked, dual-polymer network (DPN) hydrogel comprised of methacrylated carboxymethylcellulose (CMC) and methylcellulose (MC), and used in vitro, in situ and in vivo testing to assess its efficacy as an injectable, in situ gelling, biocompatible material that matches native NP properties and restores IVD biomechanical behaviors. Thermogelling MC was required to enable consistent and timely gelation of CMC in situ within whole IVDs. The CMC-MC hydrogel was tuned to match compressive and swelling NP tissue properties. When injected into whole IVDs after discectomy injury, CMC-MC restored IVD height and compressive biomechanical behaviors, including range of motion and neutral zone stiffness, to intact levels. Subcutaneous implantation of the hydrogels in rats further demonstrated good biocompatibility of CMC-MC with a relatively thin fibrous capsule, similar to comparable biomaterials. In conclusion, CMC-MC is an injectable, tunable and biocompatible hydrogel with strong potential to be used as an NP replacement biomaterial since it can gel in situ, match NP properties, and restore IVD height and biomechanical function. Future investigations will evaluate herniation risk under severe loading conditions and assess long-term in vivo performance.
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Affiliation(s)
| | | | | | | | | | | | - S B Nicoll
- Department of Biomedical Engineering, The City College of New York, Steinman Hall, Room 401, 160 Convent Avenue, New York, NY 10031,
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Abstract
STUDY DESIGN Disc recovery behavior under hypo- and hyperosmotic pressure. OBJECTIVE To evaluate the effect of osmotic pressure on the unloaded recovery response of healthy discs. SUMMARY OF BACKGROUND DATA The intervertebral disc is a poroviscoelastic material that experiences large fluctuations in water composition throughout a diurnal loading cycle. Fluid flow out of the disc occurs through mechanical loading, whereas fluid flow into the disc occurs through passive diffusion because of an imbalance of ions between the disc and its surrounding environment. Osmotic pressure has been used to alter water uptake and tissue hydration. METHODS Motion segments were prepared from the caudal spine sections of the skeletally mature bovines. A 300-N compressive load was applied for 2 hours before unloaded recovery for 12 hours. Hypo- and hyperosmotic pressure was used to alter the rate of water uptake and disc height recovery during unloaded recovery. A 5-parameter rheological model was used to describe the disc's time-dependent recovery behavior. RESULTS The elastic response was not altered by changes in osmotic pressure; however, viscoelastic recovery was highly dependent on saline osmolarity and recovery time. The fast response of viscoelastic recovery was not dependent on osmotic pressure. The time constant for the slow response decreased whereas the slow response stiffness increased as osmotic pressure increased. CONCLUSION The fast response of viscoelastic recovery is governed by flow-independent recovery, whereas the slow response is related to flow-dependent recovery. The rate and magnitude of flow-dependent recovery are highly sensitive to changes in osmotic pressure of the saline bath. There is an osmotic pressure that reduces disc recovery behavior to an elastic response or flow-independent recovery. LEVEL OF EVIDENCE N/A.
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Sikora SN, Miles DE, Tarsuslugil S, Mengoni M, Wilcox RK. Examination of an in vitro methodology to evaluate the biomechanical performance of nucleus augmentation in axial compression. Proc Inst Mech Eng H 2018; 232:230-240. [PMID: 29332499 PMCID: PMC5846852 DOI: 10.1177/0954411917752027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Intervertebral disc degeneration is one of the leading causes of back pain, but treatment options remain limited. Recently, there have been advances in the development of biomaterials for nucleus augmentation; however, the testing of such materials preclinically has proved challenging. The aim of this study was to develop methods for fabricating and testing bone-disc-bone specimens in vitro for examining the performance of nucleus augmentation procedures. Control, nucleotomy and treated intervertebral disc specimens were fabricated and tested under static load. The nucleus was removed from nucleotomy specimens using a trans-endplate approach with a bone plug used to restore bony integrity. Specimen-specific finite element models were developed to elucidate the reasons for the variations observed between control specimens. Although the computational models predicted a statistically significant difference between the healthy and nucleotomy groups, the differences found experimentally were not significantly different. This is likely due to variations in the material properties, hydration and level of annular collapse. The deformation of the bone was also found to be non-negligible. The study provides a framework for the development of testing protocols for nucleus augmentation materials and highlights the need to control disc hydration and the length of bone retained to reduce inter-specimen variability.
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Affiliation(s)
- Sebastien Nf Sikora
- 1 Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
| | - Danielle E Miles
- 1 Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK.,2 School of Chemistry, University of Leeds, Leeds, UK
| | - Sami Tarsuslugil
- 1 Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
| | - Marlène Mengoni
- 1 Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
| | - Ruth K Wilcox
- 1 Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
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Effects of axial compression and rotation angle on torsional mechanical properties of bovine caudal discs. J Mech Behav Biomed Mater 2018; 77:353-359. [DOI: 10.1016/j.jmbbm.2017.09.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 09/06/2017] [Accepted: 09/15/2017] [Indexed: 12/30/2022]
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Paraspinal Muscle Passive Stiffness Remodels in Direct Response to Spine Stiffness: A Study Using the ENT1-Deficient Mouse. Spine (Phila Pa 1976) 2017; 42:1440-1446. [PMID: 28240653 DOI: 10.1097/brs.0000000000002132] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Basic science study of the relationship between the structural properties of the spine and its surrounding musculature. OBJECTIVE To determine whether an increase in spine stiffness causes an inverse compensatory change in the passive stiffness of the adjacent paraspinal muscles. SUMMARY OF BACKGROUND DATA Intervertebral disc degeneration causes an increase in multifidus passive stiffness; this was hypothesized to compensate for a decrease in spine stiffness associated with disc degeneration. Mice lacking equilibrative nucleoside transporter 1 (ENT1) develop progressive ectopic calcification of the fibrous connective tissues of the spine, which affects the lumbar spine by 6 months of age and likely creates a mechanically stiffer spine. METHODS Experiments were conducted on four groups of mice (n = 8 mice/group): wild-type (WT) and ENT1 knockout (KO) at 2 or 8 months of age. Lumbar spines were removed and tested in cyclic axial compression to determine neutral zone length and stiffness. Single muscle fibers and bundles of fibers were isolated from lumbar multifidus and erector spinae, as well as tibialis anterior (a non-spine-related control) and tested to determine elastic modulus (passive stiffness). RESULTS At 2 months of age, neither spine nor muscle stiffness was different between KO and WT. At 8 months of age, compared with WT the lumbar spines of ENT1 KO mice had a stiffer and shorter neutral zone, and the paraspinal muscle fibers were less stiff; however, fiber bundles were not different. In addition, tibialis anterior was not different between KO and WT. CONCLUSION This work has confirmed that calcification of spinal connective tissues in the ENT1 KO mouse results in a stiffened spine, whereas the concurrent decrease in muscle fiber elastic modulus in the adjacent paraspinal muscles suggests a direct compensatory relationship between the stiffness of the spine and the muscles that are attached to it. LEVEL OF EVIDENCE N/A.
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Borem R, Madeline A, Walters J, Mayo H, Gill S, Mercuri J. Angle-ply biomaterial scaffold for annulus fibrosus repair replicates native tissue mechanical properties, restores spinal kinematics, and supports cell viability. Acta Biomater 2017; 58:254-268. [PMID: 28587986 DOI: 10.1016/j.actbio.2017.06.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 05/26/2017] [Accepted: 06/02/2017] [Indexed: 12/25/2022]
Abstract
Annulus fibrosus (AF) damage commonly occurs due to intervertebral disc (IVD) degeneration/herniation. The dynamic mechanical role of the AF is essential for proper IVD function and thus it is imperative that biomaterials developed to repair the AF withstand the mechanical rigors of the native tissue. Furthermore, these biomaterials must resist accelerated degradation within the proteolytic environment of degenerate IVDs while supporting integration with host tissue. We have previously reported a novel approach for developing collagen-based, multi-laminate AF repair patches (AFRPs) that mimic the angle-ply architecture and basic tensile properties of the human AF. Herein, we further evaluate AFRPs for their: tensile fatigue and impact burst strength, IVD attachment strength, and contribution to functional spinal unit (FSU) kinematics following IVD repair. Additionally, AFRP resistance to collagenase degradation and cytocompatibility were assessed following chemical crosslinking. In summary, AFRPs demonstrated enhanced durability at high applied stress amplitudes compared to human AF and withstood radially-directed biaxial stresses commonly borne by the native tissue prior to failure/detachment from IVDs. Moreover, FSUs repaired with AFRPs and nucleus pulposus (NP) surrogates had their axial kinematic parameters restored to intact levels. Finally, carbodiimide crosslinked AFRPs resisted accelerated collagenase digestion without detrimentally effecting AFRP tensile properties or cytocompatibility. Taken together, AFRPs demonstrate the mechanical robustness and enzymatic stability required for implantation into the damaged/degenerate IVD while supporting AF cell infiltration and viability. STATEMENT OF SIGNIFICANCE The quality of life for millions of individuals globally is detrimentally impacted by IVD degeneration and herniation. These pathologies often result in the structural demise of IVD tissue, particularly the annulus fibrosus (AF). Biomaterials developed for AF repair have yet to demonstrate the mechanical strength and durability required for utilization in the spine. Herein, we demonstrate the development of an angle-ply AF repair patch (AFRP) that can resist the application of physiologically relevant stresses without failure and which contributes to the restoration of functional spinal unit axial kinematics following repair. Furthermore, we show that this biomaterial can resist accelerated degradation in a simulated degenerate environment and supports AF cell viability.
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Affiliation(s)
- Ryan Borem
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, SC, USA
| | - Allison Madeline
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, SC, USA
| | - Joshua Walters
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, SC, USA
| | - Henry Mayo
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, SC, USA
| | - Sanjitpal Gill
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, SC, USA; Department of Orthopaedic Surgery, Medical Group of the Carolinas-Pelham, Spartanburg Regional Healthcare System, Greer, SC, USA
| | - Jeremy Mercuri
- The Laboratory of Orthopaedic Tissue Regeneration & Orthobiologics, Department of Bioengineering, Clemson University, Clemson, SC, USA.
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Pérez-San Vicente A, Peroglio M, Ernst M, Casuso P, Loinaz I, Grande HJ, Alini M, Eglin D, Dupin D. Self-Healing Dynamic Hydrogel as Injectable Shock-Absorbing Artificial Nucleus Pulposus. Biomacromolecules 2017; 18:2360-2370. [DOI: 10.1021/acs.biomac.7b00566] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Adrián Pérez-San Vicente
- Materials
Division, IK4-CIDETEC Research Centre, Paseo Miramón 196, Donostia-San Sebastián 20014, Spain
| | - Marianna Peroglio
- AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland
| | - Manuela Ernst
- AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland
| | - Pablo Casuso
- Materials
Division, IK4-CIDETEC Research Centre, Paseo Miramón 196, Donostia-San Sebastián 20014, Spain
| | - Iraida Loinaz
- Materials
Division, IK4-CIDETEC Research Centre, Paseo Miramón 196, Donostia-San Sebastián 20014, Spain
| | - Hans-Jürgen Grande
- Materials
Division, IK4-CIDETEC Research Centre, Paseo Miramón 196, Donostia-San Sebastián 20014, Spain
| | - Mauro Alini
- AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland
| | - David Eglin
- AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland
| | - Damien Dupin
- Materials
Division, IK4-CIDETEC Research Centre, Paseo Miramón 196, Donostia-San Sebastián 20014, Spain
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Russo F, Hartman RA, Bell KM, Vo N, Sowa GA, Kang JD, Vadalà G, Denaro V. Biomechanical Evaluation of Transpedicular Nucleotomy With Intact Annulus Fibrosus. Spine (Phila Pa 1976) 2017; 42:E193-E201. [PMID: 28207656 DOI: 10.1097/brs.0000000000001762] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Biomechanical testing of partially nucleotomized ovine cadaveric spines. OBJECTIVE To explore how the nucleus pulposus (NP) affects the biomechanical behavior of the intervertebral disc (IVD) by performing a partial nucleotomy via the transpedicular approach. SUMMARY OF BACKGROUND DATA Mechanical loading represents a crucial part of IVD homeostasis. However, traditional regenerative strategies require violation of the annulus fibrosus (AF) resulting in significant alteration of joint mechanics. The transpedicular nucleotomy represents a suitable method to create a cavity into the NP, as a model to study IVD regeneration with intact AF. METHODS A total of 30 ovine-lumbar- functional spinal units (FSUs) (L1-L6) randomly assigned to 5 groups: control; transpedicular tunnel (TT); TT + polymethylmethacrylate (PMMA) to repair the bone tunnel; nucleotomy; nucleotomy + PMMA. Flexion/extension, lateral-bending, and axial-rotation were evaluated under adaptive displacement control. Axial compression was applied for 15 cycles of preconditioning followed by 1 hour of constant compression. Viscoelastic behavior was modeled and parameterized. RESULTS TT has minimal effects on rotational biomechanics. The nucleotomy increases ROM and neutral zone (NZ) displacement width whereas decreasing NZ stiffness. TT + PMMA has small effects in terms of ROM. Nucleotomy + PMMA brings ROM back to the control, increases NZ stiffness, and decreases NZ displacement width. The nucleotomy tends to increase the rate of early creep. TT reduces early and late damping. The use of PMMA increased late elastic stiffness (S2) and reduced viscous damping (η2) culminating in faster resolution of creep. CONCLUSION Biomechanical properties of NP are crucial for IVD repair. This study demonstrated that TT does not affect rotational stability whereas partial nucleotomy with intact AF induce rotational instability, highlighting the central role of NP in early stages of IDD. Therefore, this model represents a successful platform to validate and optimize disc regeneration strategies. LEVEL OF EVIDENCE N/A.
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Affiliation(s)
- Fabrizio Russo
- Department of Orthopedic and Traumatology, University Campus BioMedico of Rome, Rome, Italy
| | - Robert A Hartman
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, USA
| | - Kevin M Bell
- Ferguson Laboratory for Orthopedic and Spine Research, University of Pittsburgh, Pittsburgh, PA
| | - Nam Vo
- Ferguson Laboratory for Orthopedic and Spine Research, University of Pittsburgh, Pittsburgh, PA
| | - Gwendolyn A Sowa
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, USA
| | - James D Kang
- Department of Orthopedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, USA
| | - Gianluca Vadalà
- Department of Orthopedic and Traumatology, University Campus BioMedico of Rome, Rome, Italy
| | - Vincenzo Denaro
- Department of Orthopedic and Traumatology, University Campus BioMedico of Rome, Rome, Italy
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Barrett JM, Gooyers CE, Karakolis T, Callaghan JP. The Impact of Posture on the Mechanical Properties of a Functional Spinal Unit During Cyclic Compressive Loading. J Biomech Eng 2016; 138:2530162. [DOI: 10.1115/1.4033916] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Indexed: 11/08/2022]
Abstract
To assess how posture affects the transmission of mechanical energy up the spinal column during vibration, 18 porcine functional spinal units (FSUs) were exposed to a sinusoidal force (1500 ± 1200 N) at 5 Hz for 120 min in either a flexed, extended, or neutral posture. Force and FSU height were measured continuously throughout the collection. From these data, specimen height loss, dynamic stiffness, hysteresis, and parameters from a standard linear solid (SLS) model were determined and analyzed for differences between postures. Posture had an influence on all of these parameters. In extension, the FSU had higher dynamic stiffness values than when neutral or flexed (p < 0.0001). In flexion, the FSU had higher hysteresis than both an extended or neutral posture (p < 0.0001). Height loss was greatest in a flexed posture and smallest in an extended posture (p < 0.0001). In extension, the series spring element in the SLS model had a stiffness value higher than both flexed and neutral posture conditions, whereas the stiffness in the parallel spring was the same between extension and neutral (p < 0.01), both higher than in flexion. Viscosity coefficients were highest in extension compared to both flexed and neutral (p < 0.01). Based on these results, it was determined that posture had a significant influence in determining the mechanical properties of the spine when exposed to cyclic compressive loading.
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Affiliation(s)
- Jeff M. Barrett
- Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 6P2, Canada e-mail:
| | - Chad E. Gooyers
- Giffin Koerth Forensic Engineering and Science, 40 University Avenue, Toronto, ON M5J 1T1, Canada e-mail:
| | - Thomas Karakolis
- Defence Research and Development Canada, 1133 Sheppard Avenue West, Toronto, ON M3K 2C9, Canada e-mail:
| | - Jack P. Callaghan
- Mem. ASME, Department of Kinesiology, University of Waterloo, Burt Matthews Hall, Room 3122, 200 University Avenue West, Waterloo, ON N2L 6P2, Canada e-mail:
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Bezci SE, Nandy A, O'Connell GD. Effect of Hydration on Healthy Intervertebral Disk Mechanical Stiffness. J Biomech Eng 2016; 137:101007. [PMID: 26300418 DOI: 10.1115/1.4031416] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2014] [Indexed: 11/08/2022]
Abstract
The intervertebral disk has an excellent swelling capacity to absorb water, which is thought to be largely due to the high proteoglycan composition. Injury, aging, degeneration, and diurnal loading are all noted by a significant decrease in water content and tissue hydration. The objective of this study was to evaluate the effect of hydration, through osmotic loading, on tissue swelling and compressive stiffness of healthy intervertebral disks. The wet weight of nucleus pulposus (NP) and annulus fibrosus (AF) explants following swelling was 50% or greater, demonstrating significant ability to absorb water under all osmotic loading conditions (0.015 M-3.0 M phosphate buffered saline (PBS)). Estimated NP residual strains, calculated from the swelling ratio, were approximately 1.5 × greater than AF residual strains. Compressive stiffness increased with hyperosmotic loading, which is thought to be due to material compaction from osmotic-loading and the nonlinear mechanical behavior. Importantly, this study demonstrated that residual strains and material properties are greatly dependent on osmotic loading. The findings of this study support the notion that swelling properties from osmotic loading will be important for accurately describing the effect of degeneration and injury on disk mechanics. Furthermore, the tissue swelling will be an important consideration for developing biological repair strategies aimed at restoring mechanical behavior toward a healthy disk.
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Li Z, Lezuo P, Pattappa G, Collin E, Alini M, Grad S, Peroglio M. Development of an ex vivo cavity model to study repair strategies in loaded intervertebral discs. 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; 25:2898-908. [PMID: 27037921 DOI: 10.1007/s00586-016-4542-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 03/21/2016] [Accepted: 03/21/2016] [Indexed: 12/29/2022]
Abstract
PURPOSE The aim of this study was to compare two approaches for the delivery of biomaterials to partially nucleotomised intervertebral discs in whole organ culture under loading. Such models can help to bridge the gap between in vitro and in vivo studies by assessing (1) suitability of biomaterial delivery and defect closure methods, (2) effect of mechanical loading and (3) tissue response. METHODS Mechanical performance of bovine discs filled with a hyaluronan-based thermoreversible hydrogel delivered through the annulus fibrosus (AF) or the bony endplate (EP) was evaluated under cyclic axial loading in a bioreactor. The loading protocol was optimised to achieve physiological disc height changes in nucleotomised discs. A loading regime of 0.06 ± 0.02 MPa, 0.1 Hz, 6 h daily was applied on the nucleotomised discs. Disc height and stiffness were tracked for 5 days, followed by histological analyses. RESULTS Creation of a defect is less demanding for AF approach, while sealing is superior with the EP approach. Dynamic compressive stiffness is reduced following nucleotomy, with no significant difference between the two approaches. Disc height loss was higher, disc height recovery was lower and region around the defect with reduced cell viability was smaller for AF-approached than EP-approached discs. CONCLUSIONS Two alternative methods for biomaterial testing in whole organ culture under loading were developed. Such models bring insights on the ability of the biomaterial to restore the mechanical behaviour of the discs. From a clinical perspective, the cavity models can simulate treatment of nucleotomy after disc herniation in young patients, whereby the remaining nucleus pulposus is still functional and therefore at high risk of re-herniation, though the defect may differ from the clinical situation.
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Affiliation(s)
- Zhen Li
- AO Research Institute Davos, Clavadelerstrasse 8, 7270, Davos, Switzerland
| | - Patrick Lezuo
- AO Research Institute Davos, Clavadelerstrasse 8, 7270, Davos, Switzerland
| | - Girish Pattappa
- AO Research Institute Davos, Clavadelerstrasse 8, 7270, Davos, Switzerland
| | - Estelle Collin
- Network of Excellence for Functional Biomaterials, National University of Ireland, Galway, Ireland
| | - Mauro Alini
- AO Research Institute Davos, Clavadelerstrasse 8, 7270, Davos, Switzerland
| | - Sibylle Grad
- AO Research Institute Davos, Clavadelerstrasse 8, 7270, Davos, Switzerland
| | - Marianna Peroglio
- AO Research Institute Davos, Clavadelerstrasse 8, 7270, Davos, Switzerland.
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Long RG, Bürki A, Zysset P, Eglin D, Grijpma DW, Blanquer SBG, Hecht AC, Iatridis JC. Mechanical restoration and failure analyses of a hydrogel and scaffold composite strategy for annulus fibrosus repair. Acta Biomater 2016; 30:116-125. [PMID: 26577987 DOI: 10.1016/j.actbio.2015.11.015] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 11/04/2015] [Accepted: 11/10/2015] [Indexed: 01/07/2023]
Abstract
Unrepaired defects in the annulus fibrosus of intervertebral disks are associated with degeneration and persistent back pain. A clinical need exists for a disk repair strategy that can seal annular defects, be easily delivered during surgical procedures, and restore biomechanics with low risk of herniation. Multiple annulus repair strategies were developed using poly(trimethylene carbonate) scaffolds optimized for cell delivery, polyurethane membranes designed to prevent herniation, and fibrin-genipin adhesive tuned to annulus fibrosus shear properties. This three-part study evaluated repair strategies for biomechanical restoration, herniation risk and failure mode in torsion, bending and compression at physiological and hyper-physiological loads using a bovine injury model. Fibrin-genipin hydrogel restored some torsional stiffness, bending ROM and disk height loss, with negligible herniation risk and failure was observed histologically at the fibrin-genipin mid-substance following rigorous loading. Scaffold-based repairs partially restored biomechanics, but had high herniation risk even when stabilized with sutured membranes and failure was observed histologically at the interface between scaffold and fibrin-genipin adhesive. Fibrin-genipin was the simplest annulus fibrosus repair solution evaluated that involved an easily deliverable adhesive that filled irregularly-shaped annular defects and partially restored disk biomechanics with low herniation risk, suggesting further evaluation for disk repair may be warranted. STATEMENT OF SIGNIFICANCE Lower back pain is the leading cause of global disability and commonly caused by defects and failure of intervertebral disk tissues resulting in herniation and compression of adjacent nerves. Annulus fibrosus repair materials and techniques have not been successful due to the challenging mechanical and chemical microenvironment and the needs to restore biomechanical behaviors and promote healing with negligible herniation risk while being delivered during surgical procedures. This work addressed this challenging biomaterial and clinical problem using novel materials including an adhesive hydrogel, a scaffold capable of cell delivery, and a membrane to prevent herniation. Composite repair strategies were evaluated and optimized in quantitative three-part study that rigorously evaluated disk repair and provided a framework for evaluating alternate repair techniques.
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Affiliation(s)
- Rose G Long
- Leni & Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Collaborative Research Partner Annulus Fibrosus Rupture Program of AO Foundation, Davos, Switzerland
| | - Alexander Bürki
- Institute for Surgical Technology & Biomechanics, University of Bern, Bern, Switzerland
| | - Philippe Zysset
- Institute for Surgical Technology & Biomechanics, University of Bern, Bern, Switzerland
| | - David Eglin
- AO Research Institute Davos, Davos, Switzerland; Collaborative Research Partner Annulus Fibrosus Rupture Program of AO Foundation, Davos, Switzerland
| | - Dirk W Grijpma
- Collaborative Research Partner Annulus Fibrosus Rupture Program of AO Foundation, Davos, Switzerland; University of Twente, Department of Biomaterials Science and Technology, PO Box 217, 7500 AE Enschede, The Netherlands; University of Groningen, University Medical Centre Groningen, Department of Biomedical Engineering, PO Box 196, 9700 AD Groningen, The Netherlands
| | - Sebastien B G Blanquer
- Collaborative Research Partner Annulus Fibrosus Rupture Program of AO Foundation, Davos, Switzerland; University of Twente, Department of Biomaterials Science and Technology, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Andrew C Hecht
- Leni & Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - James C Iatridis
- Leni & Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Collaborative Research Partner Annulus Fibrosus Rupture Program of AO Foundation, Davos, Switzerland.
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Oxland TR. Fundamental biomechanics of the spine--What we have learned in the past 25 years and future directions. J Biomech 2015; 49:817-832. [PMID: 26706717 DOI: 10.1016/j.jbiomech.2015.10.035] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 10/10/2015] [Accepted: 10/23/2015] [Indexed: 12/20/2022]
Abstract
Since the publication of the 2nd edition of White and Panjabi׳s textbook, Clinical Biomechanics of the Spine in 1990, there has been considerable research on the biomechanics of the spine. The focus of this manuscript will be to review what we have learned in regards to the fundamentals of spine biomechanics. Topics addressed include the whole spine, the functional spinal unit, and the individual components of the spine (e.g. vertebra, intervertebral disc, spinal ligaments). In these broad categories, our understanding in 1990 is reviewed and the important knowledge or understanding gained through the subsequent 25 years of research is highlighted. Areas where our knowledge is lacking helps to identify promising topics for future research. In this manuscript, as in the White and Panjabi textbook, the emphasis is on experimental research using human material, either in vivo or in vitro. The insights gained from mathematical models and animal experimentation are included where other data are not available. This review is intended to celebrate the substantial gains that have been made in the field over these past 25 years and also to identify future research directions.
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Affiliation(s)
- Thomas R Oxland
- Departments of Orthopaedics and Mechanical Engineering, University of British Columbia, Canada; International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Canada.
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Showalter BL, Elliott DM, Chen W, Malhotra NR. Evaluation of an In Situ Gelable and Injectable Hydrogel Treatment to Preserve Human Disc Mechanical Function Undergoing Physiologic Cyclic Loading Followed by Hydrated Recovery. J Biomech Eng 2015; 137:081008. [PMID: 25950273 DOI: 10.1115/1.4030530] [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: 07/21/2014] [Indexed: 12/21/2022]
Abstract
Despite the prevalence of disc degeneration and its contributions to low back problems, many current treatments are palliative only and ultimately fail. To address this, nucleus pulposus replacements are under development. Previous work on an injectable hydrogel nucleus pulposus replacement composed of n-carboxyethyl chitosan, oxidized dextran, and teleostean has shown that it has properties similar to native nucleus pulposus, can restore compressive range of motion in ovine discs, is biocompatible, and promotes cell proliferation. The objective of this study was to determine if the hydrogel implant will be contained and if it will restore mechanics in human discs undergoing physiologic cyclic compressive loading. Fourteen human lumbar spine segments were tested using physiologic cyclic compressive loading while intact, following nucleotomy, and again following treatment of injecting either phosphate buffered saline (PBS) (sham, n = 7) or hydrogel (implant, n = 7). In each compressive test, mechanical parameters were measured immediately before and after 10,000 cycles of compressive loading and following a period of hydrated recovery. The hydrogel implant was not ejected from the disc during 10,000 cycles of physiological compression testing and appeared undamaged when discs were bisected following all mechanical tests. For sham samples, creep during cyclic loading increased (+15%) from creep during nucleotomy testing, while for implant samples creep strain decreased (-3%) toward normal. There was no difference in compressive modulus or compressive strains between implant and sham samples. These findings demonstrate that the implant interdigitates with the nucleus pulposus, preventing its expulsion during 10,000 cycles of compressive loading and preserves disc creep within human L5-S1 discs. This and previous studies provide a solid foundation for continuing to evaluate the efficacy of the hydrogel implant.
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Likhitpanichkul M, Dreischarf M, Illien-Junger S, Walter BA, Nukaga T, Long RG, Sakai D, Hecht AC, Iatridis JC. Fibrin-genipin adhesive hydrogel for annulus fibrosus repair: performance evaluation with large animal organ culture, in situ biomechanics, and in vivo degradation tests. Eur Cell Mater 2014; 28:25-37; discussion 37-8. [PMID: 25036053 PMCID: PMC4409328 DOI: 10.22203/ecm.v028a03] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Annulus fibrosus (AF) defects from annular tears, herniation, and discectomy procedures are associated with painful conditions and accelerated intervertebral disc (IVD) degeneration. Currently, no effective treatments exist to repair AF damage, restore IVD biomechanics and promote tissue regeneration. An injectable fibrin-genipin adhesive hydrogel (Fib-Gen) was evaluated for its performance repairing large AF defects in a bovine caudal IVD model using ex vivo organ culture and biomechanical testing of motion segments, and for its in vivo longevity and biocompatibility in a rat model by subcutaneous implantation. Fib-Gen sealed AF defects, prevented IVD height loss, and remained well-integrated with native AF tissue following approximately 14,000 cycles of compression in 6-day organ culture experiments. Fib-Gen repair also retained high viability of native AF cells near the repair site, reduced nitric oxide released to the media, and showed evidence of AF cell migration into the gel. Biomechanically, Fib-Gen fully restored compressive stiffness to intact levels validating organ culture findings. However, only partial restoration of tensile and torsional stiffness was obtained, suggesting opportunities to enhance this formulation. Subcutaneous implantation results, when compared with the literature, suggested Fib-Gen exhibited similar biocompatibility behaviour to fibrin alone but degraded much more slowly. We conclude that injectable Fib-Gen successfully sealed large AF defects, promoted functional restoration with improved motion segment biomechanics, and served as a biocompatible adhesive biomaterial that had greatly enhanced in vivo longevity compared to fibrin. Fib-Gen offers promise for AF repairs that may prevent painful conditions and accelerated degeneration of the IVD, and warrants further material development and evaluation.
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Affiliation(s)
- M. Likhitpanichkul
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA,Collaborative Research Partner Annulus Fibrosus Rupture Program of AO Foundation, Davos, Switzerland
| | - M. Dreischarf
- Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - S. Illien-Junger
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA,Collaborative Research Partner Annulus Fibrosus Rupture Program of AO Foundation, Davos, Switzerland
| | - B. A. Walter
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - T. Nukaga
- Collaborative Research Partner Annulus Fibrosus Rupture Program of AO Foundation, Davos, Switzerland,Department of Orthopaedic Surgery, Tokai University School of Medicine, Kanagawa, Japan
| | - R. G Long
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA,Collaborative Research Partner Annulus Fibrosus Rupture Program of AO Foundation, Davos, Switzerland
| | - D. Sakai
- Collaborative Research Partner Annulus Fibrosus Rupture Program of AO Foundation, Davos, Switzerland,Department of Orthopaedic Surgery, Tokai University School of Medicine, Kanagawa, Japan
| | - A. C. Hecht
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - J. C. Iatridis
- Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA,Collaborative Research Partner Annulus Fibrosus Rupture Program of AO Foundation, Davos, Switzerland,Address for correspondence: James C. Iatridis, PhD, Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box1188, New York, NY 10029, USA, Telephone Number: 1-212-241-1517, FAX Number: 1-212-876-3168,
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Shock absorbing function study on denucleated intervertebral disc with or without hydrogel injection through static and dynamic biomechanical tests in vitro. BIOMED RESEARCH INTERNATIONAL 2014; 2014:461724. [PMID: 25045680 PMCID: PMC4090528 DOI: 10.1155/2014/461724] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 04/13/2014] [Accepted: 06/02/2014] [Indexed: 11/17/2022]
Abstract
Hydrogel injection has been recently proposed as a novel therapy for disc degenerative diseases, with the potential to restore the spine motion and the intervertebral disc height. However, it remains unknown whether the new technique could also maintain the shock absorbing property of the treated intervertebral disc. In this study, 18 porcine lumbar bone-disc-bone specimens were collected and randomly divided into three groups: the normal with intact intervertebral discs, the mimic for the injection of disulfide cross-linked hyaluronan hydrogels following discectomy, and the control disc with discectomy only. In the static compression test, specimens in the mimic group exhibited displacements similar to those in the normal discs, whereas the control group showed a significantly larger displacement range in the first two steps (P < 0.05). With the frequency increasing, all specimens generally displayed an increasing storage modulus, decreasing loss modulus, and tanδ. At any frequency point, the control group exhibited the largest value in all the three parameters among three groups while the normal group was the lowest, with the mimic group being mostly close to the normal group. Therefore, the hydrogel injection into the intervertebral discs greatly restored their shock absorbing function, suggesting that the technique could serve as an effective approach to maintaining biomechanical properties of the degenerative intervertebral disc.
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Validation and application of an intervertebral disc finite element model utilizing independently constructed tissue-level constitutive formulations that are nonlinear, anisotropic, and time-dependent. J Biomech 2014; 47:2540-6. [PMID: 24998992 DOI: 10.1016/j.jbiomech.2014.06.008] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 05/05/2014] [Accepted: 06/05/2014] [Indexed: 10/25/2022]
Abstract
Finite element (FE) models are advantageous in the study of intervertebral disc mechanics as the stress-strain distributions can be determined throughout the tissue and the applied loading and material properties can be controlled and modified. However, the complicated nature of the disc presents a challenge in developing an accurate and predictive disc model, which has led to limitations in FE geometry, material constitutive models and properties, and model validation. The objective of this study was to develop a new FE model of the intervertebral disc, to validate the model's nonlinear and time-dependent responses without tuning or calibration, and to evaluate the effect of changes in nucleus pulposus (NP), cartilaginous endplate (CEP), and annulus fibrosus (AF) material properties on the disc mechanical response. The new FE disc model utilized an analytically-based geometry. The model was created from the mean shape of human L4/L5 discs, measured from high-resolution 3D MR images and averaged using signed distance functions. Structural hyperelastic constitutive models were used in conjunction with biphasic-swelling theory to obtain material properties from recent tissue tests in confined compression and uniaxial tension. The FE disc model predictions fit within the experimental range (mean ± 95% confidence interval) of the disc's nonlinear response for compressive slow loading ramp, creep, and stress-relaxation simulations. Changes in NP and CEP properties affected the neutral-zone displacement but had little effect on the final stiffness during slow-ramp compression loading. These results highlight the need to validate FE models using the disc's full nonlinear response in multiple loading scenarios.
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Showalter BL, Malhotra NR, Vresilovic EJ, Elliott DM. Nucleotomy reduces the effects of cyclic compressive loading with unloaded recovery on human intervertebral discs. J Biomech 2014; 47:2633-40. [PMID: 24957922 DOI: 10.1016/j.jbiomech.2014.05.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 04/29/2014] [Accepted: 05/24/2014] [Indexed: 01/06/2023]
Abstract
The first objective of this study was to determine the effects of physiological cyclic loading followed by unloaded recovery on the mechanical response of human intervertebral discs. The second objective was to examine how nucleotomy alters the disc's mechanical response to cyclic loading. To complete these objectives, 15 human L5-S1 discs were tested while intact and subsequent to nucleotomy. The testing consisted of 10,000 cycles of physiological compressive loads followed by unloaded hydrated recovery. Cyclic loading increased compression modulus (3%) and strain (33%), decreased neutral zone modulus (52%), and increased neutral zone strain (31%). Degeneration was not correlated with the effect of cyclic loading in intact discs, but was correlated with cyclic loading effects after nucleotomy, with more degenerate samples experiencing greater increases in both compressive and neutral zone strain following cyclic loading. Partial removal of the nucleus pulposus decreased the compression and neutral zone modulus while increasing strain. These changes correspond to hypermobility, which will alter overall spinal mechanics and may impact low back pain via altered motion throughout the spinal column. Nucleotomy also reduced the effects of cyclic loading on mechanical properties, likely due to altered fluid flow, which may impact cellular mechanotransduction and transport of disc nutrients and waste. Degeneration was not correlated with the acute changes of nucleotomy. Results of this study provide an ideal protocol and control data for evaluating the effectiveness of a mechanically-based disc degeneration treatment, such as a nucleus replacement.
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Affiliation(s)
- Brent L Showalter
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, United States
| | - Neil R Malhotra
- Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA, United States
| | - Edward J Vresilovic
- Hershey Department of Orthopaedics and Rehabilitation, Penn State University, Hershey, PA, United States
| | - Dawn M Elliott
- Department of Biomedical Engineering, University of Delaware, 125 East Delaware Ave, Newark, DE, United States.
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Rodrigues-Pinto R, Richardson SM, Hoyland JA. Identification of novel nucleus pulposus markers: Interspecies variations and implications for cell-based therapiesfor intervertebral disc degeneration. Bone Joint Res 2013; 2:169-78. [PMID: 23958792 PMCID: PMC3747513 DOI: 10.1302/2046-3758.28.2000184] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mesenchymal stem-cell based therapies have been proposed as novel treatments for intervertebral disc degeneration, a prevalent and disabling condition associated with back pain. The development of these treatment strategies, however, has been hindered by the incomplete understanding of the human nucleus pulposus phenotype and by an inaccurate interpretation and translation of animal to human research. This review summarises recent work characterising the nucleus pulposus phenotype in different animal models and in humans and integrates their findings with the anatomical and physiological differences between these species. Understanding this phenotype is paramount to guarantee that implanted cells restore the native functions of the intervertebral disc. Cite this article: Bone Joint Res 2013;2:169-78.
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Affiliation(s)
- R Rodrigues-Pinto
- University of Manchester, CentreFor Regenerative Medicine, Institute of Inflammationand Repair, Faculty of Medical and Human Sciences, StopfordBuilding, Oxford Road, ManchesterM13 9PT, UK, and Departmentof Orthopaedics, Centro Hospitalar do Porto- Hospital de Santo António, Largo Prof. AbelSalazar, 4099-001 Porto, Portugal
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Leckie SK, Sowa GA, Bechara BP, Hartman RA, Coelho JP, Witt WT, Dong QD, Bowman BW, Bell KM, Vo NV, Kramer BC, Kang JD. Injection of human umbilical tissue-derived cells into the nucleus pulposus alters the course of intervertebral disc degeneration in vivo. Spine J 2013; 13:263-72. [PMID: 23384411 PMCID: PMC4868072 DOI: 10.1016/j.spinee.2012.12.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 08/22/2012] [Accepted: 12/09/2012] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Patients often present to spine clinic with evidence of intervertebral disc degeneration (IDD). If conservative management fails, a safe and effective injection directly into the disc might be preferable to the risks and morbidity of surgery. PURPOSE To determine whether injecting human umbilical tissue-derived cells (hUTC) into the nucleus pulposus (NP) might improve the course of IDD. DESIGN Prospective, randomized, blinded placebo-controlled in vivo study. PATIENT SAMPLE Skeletally mature New Zealand white rabbits. OUTCOME MEASURES Degree of IDD based on magnetic resonance imaging (MRI), biomechanics, and histology. METHODS Thirty skeletally mature New Zealand white rabbits were used in a previously validated rabbit annulotomy model for IDD. Discs L2-L3, L3-L4, and L4-L5 were surgically exposed and punctured to induce degeneration and then 3 weeks later the same discs were injected with hUTC with or without a hydrogel carrier. Serial MRIs obtained at 0, 3, 6, and 12 weeks were analyzed for evidence of degeneration qualitatively and quantitatively via NP area and MRI Index. The rabbits were sacrificed at 12 weeks and discs L4-L5 were analyzed histologically. The L3-L4 discs were fixed to a robotic arm and subjected to uniaxial compression, and viscoelastic displacement curves were generated. RESULTS Qualitatively, the MRIs demonstrated no evidence of degeneration in the control group over the course of 12 weeks. The punctured group yielded MRIs with the evidence of disc height loss and darkening, suggestive of degeneration. The three treatment groups (cells alone, carrier alone, or cells+carrier) generated MRIs with less qualitative evidence of degeneration than the punctured group. MRI Index and area for the cell and the cell+carrier groups were significantly distinct from the punctured group at 12 weeks. The carrier group generated MRI data that fell between control and punctured values but failed to reach a statistically significant difference from the punctured values. There were no statistically significant MRI differences among the three treatment groups. The treated groups also demonstrated viscoelastic properties that were distinct from the control and punctured values, with the cell curve more similar to the punctured curve and the carrier curve and carrier+cells curve more similar to the control curve (although no creep differences achieved statistical significance). There was some histological evidence of improved cellularity and disc architecture in the treated discs compared with the punctured discs. CONCLUSIONS Treatment of degenerating rabbit intervertebral discs with hUTC in a hydrogel carrier solution might help restore the MRI, histological, and biomechanical properties toward those of nondegenerated controls. Treatment with cells in saline or a hydrogel carrier devoid of cells also might help restore some imaging, architectural, and physical properties to the degenerating disc. These data support the potential use of therapeutic cells in the treatment of disc degeneration.
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Affiliation(s)
- Steven K Leckie
- Department of Orthopedics, University of Pittsburgh Medical Center, 200 Lothrop St., Pittsburgh, PA 15213, USA.
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Izzo R, Guarnieri G, Guglielmi G, Muto M. Biomechanics of the spine. Part I: spinal stability. Eur J Radiol 2012; 82:118-26. [PMID: 23088879 DOI: 10.1016/j.ejrad.2012.07.024] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 07/21/2012] [Accepted: 07/23/2012] [Indexed: 02/07/2023]
Abstract
Biomechanics, the application of mechanical principles to living organisms, helps us to understand how all the bony and soft spinal components contribute individually and together to ensure spinal stability, and how traumas, tumours and degenerative disorders exert destabilizing effects. Spine stability is the basic requirement to protect nervous structures and prevent the early mechanical deterioration of spinal components. The literature reports a number of biomechanical and clinical definitions of spinal stability, but a consensus definition is lacking. Any vertebra in each spinal motion segment, the smallest functional unit of the spine, can perform various combinations of the main and coupled movements during which a number of bony and soft restraints maintain spine stability. Bones, disks and ligaments contribute by playing a structural role and by acting as transducers through their mechanoreceptors. Mechanoreceptors send proprioceptive impulses to the central nervous system which coordinates muscle tone, movement and reflexes. Damage to any spinal structure gives rise to some degree of instability. Instability is classically considered as a global increase in the movements associated with the occurrence of back and/or nerve root pain. The assessment of spinal instability remains a major challenge for diagnostic imaging experts. Knowledge of biomechanics is essential in view of the increasing involvement of radiologists and neuroradiologists in spinal interventional procedures and the ongoing development of new techniques and devices. Bioengineers and surgeons are currently focusing on mobile stabilization systems. These systems represent a new frontier in the treatment of painful degenerative spine and aim to neutralize noxious forces, restore the normal function of spinal segments and protect the adjacent segments. This review discusses the current concepts of spine stability.
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Affiliation(s)
- Roberto Izzo
- Neuroradiology Department, "A. Cardarelli" Hospital, Napoli, Italy.
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Abstract
STUDY DESIGN Investigation of injectable nucleus pulposus (NP) implant. OBJECTIVE To assess the ability of a recently developed injectable hydrogel implant to restore nondegenerative disc mechanics through support of NP functional mechanics. SUMMARY OF BACKGROUND DATA Although surgical intervention for low back pain is effective for some patients, treated discs undergo altered biomechanics and adjacent levels are at increased risk for accelerated degeneration. One potential treatment as an alternative to surgery for degenerated disc includes the percutaneous delivery of agents to support NP functional mechanics. The implants are delivered in a minimally invasive fashion, potentially on an outpatient basis, and do not preclude later surgical options. One of the challenges in designing such implants includes the need to match key NP mechanical behavior and mimic the role of native nondegenerate NP in spinal motion. METHODS The oxidized hyaluronic acid gelatin implant material was prepared. In vitro mechanical testing was performed in mature ovine bone-disc-bone units in 3 stages: intact, discectomy, and implantation versus sham. Tested samples were cut axially for qualitative structural observations. RESULTS Discectomy increased axial range of motion (ROM) significantly compared with intact. Hydrogel implantation reduced ROM 17% (P < 0.05) compared with discectomy and returned ROM to intact levels (ROM intact 0.71 mm, discectomy 0.87 mm, postimplantation 0.72 mm). Although ROM for the hydrogel implant group was statistically unchanged compared with the intact disc, ROM for sham discs, which received a discectomy and no implant, was significantly increased compared with intact. The compression and tension stiffness were decreased with discectomy and remained unchanged for both implant and sham groups as expected because the annulus fibrosus was not repaired. Gross morphology images confirmed no ejection of NP implant. CONCLUSION An injectable implant that mimics nondegenerate NP has the potential to return motion segment ROM to normal subsequent to injury.
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Leckie SK, Bechara BP, Hartman RA, Sowa GA, Woods BI, Coelho JP, Witt WT, Dong QD, Bowman BW, Bell KM, Vo NV, Wang B, Kang JD. Injection of AAV2-BMP2 and AAV2-TIMP1 into the nucleus pulposus slows the course of intervertebral disc degeneration in an in vivo rabbit model. Spine J 2012; 12:7-20. [PMID: 22023960 PMCID: PMC4896143 DOI: 10.1016/j.spinee.2011.09.011] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 07/27/2011] [Accepted: 09/07/2011] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Intervertebral disc degeneration (IDD) is a common cause of back pain. Patients who fail conservative management may face the morbidity of surgery. Alternative treatment modalities could have a significant impact on disease progression and patients' quality of life. PURPOSE To determine if the injection of a virus vector carrying a therapeutic gene directly into the nucleus pulposus improves the course of IDD. STUDY DESIGN Prospective randomized controlled animal study. METHODS Thirty-four skeletally mature New Zealand white rabbits were used. In the treatment group, L2-L3, L3-L4, and L4-L5 discs were punctured in accordance with a previously validated rabbit annulotomy model for IDD and then subsequently treated with adeno-associated virus serotype 2 (AAV2) vector carrying genes for either bone morphogenetic protein 2 (BMP2) or tissue inhibitor of metalloproteinase 1 (TIMP1). A nonoperative control group, nonpunctured sham surgical group, and punctured control group were also evaluated. Serial magnetic resonance imaging (MRI) studies at 0, 6, and 12 weeks were obtained, and a validated MRI analysis program was used to quantify degeneration. The rabbits were sacrificed at 12 weeks, and L4-L5 discs were analyzed histologically. Viscoelastic properties of the L3-L4 discs were analyzed using uniaxial load-normalized displacement testing. Creep curves were mathematically modeled according to a previously validated two-phase exponential model. Serum samples obtained at 0, 6, and 12 weeks were assayed for biochemical evidence of degeneration. RESULTS The punctured group demonstrated MRI and histologic evidence of degeneration as expected. The treatment groups demonstrated less MRI and histologic evidence of degeneration than the punctured group. The serum biochemical marker C-telopeptide of collagen type II increased rapidly in the punctured group, but the treated groups returned to control values by 12 weeks. The treatment groups demonstrated several viscoelastic properties that were distinct from control and punctured values. CONCLUSIONS Treatment of punctured rabbit intervertebral discs with AAV2-BMP2 or AAV2-TIMP1 helps delay degenerative changes, as seen on MRI, histologic sampling, serum biochemical analysis, and biomechanical testing. Although data from animal models should be extrapolated to the human condition with caution, this study supports the potential use of gene therapy for the treatment of IDD.
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Affiliation(s)
- Steven K. Leckie
- Corresponding author. Department of Orthopedic Surgery, University of Pittsburgh Medical Center, BST E1641, 200 Lothrop St, Pittsburgh, PA 15213, USA. Tel.: (412) 648-1090. (S.K. Leckie)
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The effect of nucleotomy and the dependence of degeneration of human intervertebral disc strain in axial compression. Spine (Phila Pa 1976) 2011; 36:1765-71. [PMID: 21394074 PMCID: PMC3146972 DOI: 10.1097/brs.0b013e318216752f] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Biomechanics of human intervertebral discs before and after nucleotomy. OBJECTIVE To noninvasively quantify the effect of nucleotomy on internal strains under axial compression in flexion, neutral, and extension positions, and to determine whether the change in strains depended on degeneration. SUMMARY OF BACKGROUND DATA Herniation and nucleotomy may accelerate the progression of disc degeneration. Removal of nucleus pulposus (NP) tissue has resulted in altered disc mechanics in vitro, including a decrease in internal pressure and an increase in the deformations at physiologically relevant strains. We recently presented a technique to quantify internal disc strains using magnetic resonance imaging (MRI). METHODS Degeneration was quantitatively assessed by the T1ρ relaxation time in the NP. Samples were prepared from human levels L3-L4 and/or L4-L5. A 1000-N compressive load was applied while in the magnetic resonance scanner. Nucleotomy was performed by removing 2 g of NP through the posterior-lateral annulus fibrosus (AF). The discs were rehydrated, reimaged, and retested. The analyzed parameters include axial deformation, AF radial bulge, and strains. RESULTS.: The axial deformation was more compressive after nucleotomy. In the neutral position, the axial deformation after nucleotomy correlated with degeneration (as quantified by T1ρ in the NP), with minimal alteration in nondegenerated discs. Nucleotomy altered the radial displacements and strains in the neutral position, such that the inner AF radial bulge decreased and the radial strains were more tensile in the lateral AF and less tensile in the posterior AF. In the bending loading positions the radial strains were not affected by nucleotomy. CONCLUSION Nucleotomy alters the internal radial and axial AF strains in the neutral position, which may leave the AF vulnerable to damage and microfractures. In bending, the effects of nucleotomy were minimal, likely due to more of the applied load being directed over the AF. Some of the nucleotomy effects are modulated by degeneration, where the mechanical effect of nucleotomy was magnified in degenerated discs and may further induce mechanical damage and degeneration.
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O’Connell GD, Vresilovic EJ, Elliott DM. Human intervertebral disc internal strain in compression: the effect of disc region, loading position, and degeneration. J Orthop Res 2011; 29:547-55. [PMID: 21337394 PMCID: PMC3428014 DOI: 10.1002/jor.21232] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Accepted: 06/28/2010] [Indexed: 02/04/2023]
Abstract
The primary function of the disc is mechanical; therefore, degenerative changes in disc mechanics and the interactions between the annulus fibrosus (AF) and nucleus pulposus (NP) in nondegenerate and degenerate discs are important to functional evaluation. The disc experiences complex loading conditions, including mechanical interactions between the pressurized NP and the surrounding fiber-reinforced AF. Our objective was to noninvasively evaluate the internal deformations of nondegenerate and degenerate human discs under axial compression with flexion, neutral, and extension positions using magnetic resonance imaging and image correlation. The side of applied bending (e.g., anterior AF in flexion) had higher tensile radial and compressive axial strains, and the opposite side of bending exhibited tensile axial strains even though the disc was loaded under axial compression. Degenerated discs exhibited higher compressive axial and tensile radial strains, which suggest that load distribution through the disc subcomponents are altered with degeneration, likely due to the depressurized NP placing more of the applied load directly on the AF. The posterior AF exhibited higher compressive axial and higher tensile radial strains than the other AF regions, and the strains were not correlated with degeneration, suggesting this region undergoes high strains throughout life, which may predispose it to failure and tears. In addition to understanding internal disc mechanics, this study provides important new data into the changes in internal strain with degeneration, data for validation of finite element models, and provides a technique and baseline data for evaluating surgical treatments.
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Affiliation(s)
- Grace D. O’Connell
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia PA
| | | | - Dawn M. Elliott
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia PA
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Axial creep loading and unloaded recovery of the human intervertebral disc and the effect of degeneration. J Mech Behav Biomed Mater 2011; 4:933-42. [PMID: 21783103 DOI: 10.1016/j.jmbbm.2011.02.002] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 01/27/2011] [Accepted: 02/03/2011] [Indexed: 11/23/2022]
Abstract
The intervertebral disc maintains a balance between externally applied loads and internal osmotic pressure. Fluid flow plays a key role in this process, causing fluctuations in disc hydration and height. The objectives of this study were to quantify and model the axial creep and recovery responses of nondegenerate and degenerate human lumbar discs. Two experiments were performed. First, a slow compressive ramp was applied to 2000 N, unloaded to allow recovery for up to 24 h, and re-applied. The linear-region stiffness and disc height were within 5% of the initial condition for recovery times greater than 8 h. In the second experiment, a 1000 N creep load was applied for four hours, unloaded recovery monitored for 24 h, and the creep load repeated. A viscoelastic model comprised of a "fast" and "slow" exponential response was used to describe the creep and recovery, where the fast response is associated with flow in the nucleus pulposus (NP) and endplate, while the slow response is associated with the annulus fibrosus (AF). The study demonstrated that recovery is 3-4X slower than loading. The fast response was correlated with degeneration, suggesting larger changes in the NP with degeneration compared to the AF. However, the fast response comprised only 10%-15% of the total equilibrium displacement, with the AF-dominated slow response comprising 40%-70%. Finally, the physiological loads and deformations and their associated long equilibrium times confirm that diurnal loading does not represent "equilibrium" in the disc, but that over time the disc is in steady-state.
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Smith LJ, Nerurkar NL, Choi KS, Harfe BD, Elliott DM. Degeneration and regeneration of the intervertebral disc: lessons from development. Dis Model Mech 2010; 4:31-41. [PMID: 21123625 PMCID: PMC3008962 DOI: 10.1242/dmm.006403] [Citation(s) in RCA: 250] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Degeneration of the intervertebral discs, a process characterized by a cascade of cellular, biochemical, structural and functional changes, is strongly implicated as a cause of low back pain. Current treatment strategies for disc degeneration typically address the symptoms of low back pain without treating the underlying cause or restoring mechanical function. A more in-depth understanding of disc degeneration, as well as opportunities for therapeutic intervention, can be obtained by considering aspects of intervertebral disc development. Development of the intervertebral disc involves the coalescence of several different cell types through highly orchestrated and complex molecular interactions. The resulting structures must function synergistically in an environment that is subjected to continuous mechanical perturbation throughout the life of an individual. Early postnatal changes, including altered cellularity, vascular regression and altered extracellular matrix composition, might set the disc on a slow course towards symptomatic degeneration. In this Perspective, we review the pathogenesis and treatment of intervertebral disc degeneration in the context of disc development. Within this scope, we examine how model systems have advanced our understanding of embryonic morphogenesis and associated molecular signaling pathways, in addition to the postnatal changes to the cellular, nutritional and mechanical microenvironment. We also discuss the current status of biological therapeutic strategies that promote disc regeneration and repair, and how lessons from development might provide clues for their refinement.
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Affiliation(s)
- Lachlan J Smith
- Department of Orthopaedic Surgery, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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Abstract
STUDY DESIGN To develop a construction algorithm in which electrospun nanofibrous scaffolds are coupled with a biocompatible hydrogel to engineer a mesenchymal stem cell (MSC)-based disc replacement. OBJECTIVE To engineer a disc-like angle-ply structure (DAPS) that replicates the multiscale architecture of the intervertebral disc. SUMMARY OF BACKGROUND DATA Successful engineering of a replacement for the intervertebral disc requires replication of its mechanical function and anatomic form. Despite many attempts to engineer a replacement for ailing and degenerated discs, no prior study has replicated the multiscale hierarchical architecture of the native disc, and very few have assessed the mechanical function of formed neo-tissues. METHODS A new algorithm for the construction of a disc analogue was developed, using agarose to form a central nucleus pulposus (NP) and oriented electrospun nanofibrous scaffolds to form the anulus fibrosus region (AF). Bovine MSCs were seeded into both regions and biochemical, histologic, and mechanical maturation were evaluated with in vitro culture. RESULTS We show that mechanical testing in compression and torsion, loading methods commonly used to assess disc mechanics, reveal equilibrium and time-dependent behaviors that are qualitatively similar to native tissue, although lesser in magnitude. Further, we demonstrate that cells seeded into both AF and NP regions adopt distinct morphologies that mirror those seen in native tissue, and that, in the AF region, this ordered community of cells deposit matrix that is organized in an angle-ply configuration. Finally, constructs demonstrate functional development with long-term in vitro culture. CONCLUSION These findings provide a new approach for disc tissue engineering that replicates multi-scale form and function of the intervertebral disc, providing a foundation from which to build a multi-scale, biologic, anatomically and hierarchically relevant composite disc analogue for eventual disc replacement.
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Boxberger JI, Orlansky AS, Sen S, Elliott DM. Reduced nucleus pulposus glycosaminoglycan content alters intervertebral disc dynamic viscoelastic mechanics. J Biomech 2009; 42:1941-6. [PMID: 19539936 DOI: 10.1016/j.jbiomech.2009.05.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 05/01/2009] [Accepted: 05/08/2009] [Indexed: 01/11/2023]
Abstract
The intervertebral disc functions over a range of dynamic loading regimes including axial loads applied across a spectrum of frequencies at varying compressive loads. Biochemical changes occurring in early degeneration, including reduced nucleus pulposus glycosaminoglycan content, may alter disc mechanical behavior and thus may contribute to the progression of degeneration. The objective of this study was to determine disc dynamic viscoelastic properties under several equilibrium loads and loading frequencies, and further, to determine how reduced nucleus glycosaminoglycan content alters dynamic mechanics. We hypothesized that (1) dynamic stiffness would be elevated with increasing equilibrium load and increasing frequency, (2) the disc would behave more elastically at higher frequencies, and finally, (3) dynamic stiffness would be reduced at low equilibrium loads under all frequencies due to nucleus glycosaminoglycan loss. We mechanically tested control and chondroitinase ABC injected rat lumbar motion segments at several equilibrium loads using oscillatory loading at frequencies ranging from 0.05 to 5Hz. The rat lumbar disc behaved non-linearly with higher dynamic stiffness at elevated compressive loads irrespective of frequency. Phase angle was not affected by equilibrium load, although it decreased as frequency was increased. Reduced glycosaminoglycan decreased dynamic stiffness at low loads but not at high equilibrium loads and led to increased phase angle at all loads and frequencies. The findings of this study demonstrate the effect of equilibrium load and loading frequencies on dynamic disc mechanics and indicate possible mechanical mechanisms through which disc degeneration can progress.
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Affiliation(s)
- John I Boxberger
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA 19104-6081, USA
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Degenerative anular changes induced by puncture are associated with insufficiency of disc biomechanical function. Spine (Phila Pa 1976) 2009; 34:998-1005. [PMID: 19404174 DOI: 10.1097/brs.0b013e31819c09c4] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN In vivo experiments to examine physiologic consequences and in vitro tests to determine immediate biomechanical effects of anular injury by needle puncture. OBJECTIVE To determine whether a relationship exists between induction of degenerative changes in anulus fibrosus (AF) and compromised disc biomechanical function according to injury size. SUMMARY OF BACKGROUND DATA Various studies in intervertebral disc mechanics, degeneration, and regeneration involve the creation of a defect in the anulus fibrosus (AF). However, the impact of the puncture, itself, on biomechanical function and disc health are not understood. METHODS For in vivo experiments, rat caudal discs subjected to percutaneous anular punctures using different gauge size hypodermic needles (18, 22, 26 g) and nonpunctured controls were examined histologically up to 4 weeks postsurgery. For in vitro biomechanical testing, healthy motion segments were isolated and their creep compression response assessed immediately after needle puncture. RESULTS We found that needle size-dependence of creep compression behavior paralleled the size-dependence of degenerative changes in the AF. Specifically, 18-g punctures resulted in inward bulging of the AF, lamellar disorganization, and cellular changes. These changes were not seen in 22- and 26-g punctured discs. Biomechanical tests showed that only 18-g needle punctures led to significant changes in disc mechanics. Importantly, a statistically significant association was found between needle sizes that caused biomechanical changes and induction of degenerative changes in the AF. CONCLUSION Our findings suggest that injury sizes large enough to disrupt biomechanical function are needed to drive degenerative changes in rat caudal disc AF. Based on the data, we believe that small anular defects become sealed, allowing the disc to function normally and the AF to heal. Larger defects appear to require longer wound closure times, and may prolong the duration of impaired disc function.
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