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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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Vanaclocha A, Vanaclocha V, Atienza CM, Clavel P, Jordá-Gómez P, Barrios C, Vanaclocha L. Bionate ® nucleus disc replacement: bench testing comparing two different designs. J Orthop Traumatol 2023; 24:13. [PMID: 37041425 PMCID: PMC10090247 DOI: 10.1186/s10195-023-00692-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 03/12/2023] [Indexed: 04/13/2023] Open
Abstract
BACKGROUND Intervertebral disc nucleus degeneration initiates a degenerative cascade and can induce chronic low back pain. Nucleus replacement aims to replace the nucleus while the annulus is still intact. Over time, several designs have been introduced, but the definitive solution continues to be elusive. Therefore, we aimed to create a new nucleus replacement that replicates intact intervertebral disc biomechanics, and thus has the potential for clinical applications. MATERIALS AND METHODS Two implants with an outer ring and one (D2) with an additional midline strut were compared. Static and fatigue tests were performed with an INSTRON 8874 following the American Society for Testing and Materials F2267-04, F2346-05, 2077-03, D2990-01, and WK4863. Implant stiffness was analyzed at 0-300 N, 500-2000 N, and 2000-6000 N and implant compression at 300 N, 1000 N, 2000 N, and 6000 N. Wear tests were performed following ISO 18192-1:2008 and 18192-2:2010. GNU Octave software was used to calculate movement angles and parameters. The statistical analysis package R was used with the Deducer user interface. Statistically significant differences between the two designs were analyzed with ANOVA, followed by a post hoc analysis. RESULTS D1 had better behavior in unconfined compression tests, while D2 showed a "jump." D2 deformed 1 mm more than D1. Sterilized implants were more rigid and deformed less. Both designs showed similar behavior under confined compression and when adding shear. A silicone annulus minimized differences between the designs. Wear under compression fatigue was negligible for D1 but permanent for D2. D1 suffered permanent height deformation but kept its width. D2 suffered less height loss than D1 but underwent a permanent width deformation. Both designs showed excellent responses to compression fatigue with no breaks, cracks, or delamination. At 10 million cycles, D2 showed 3-times higher wear than D1. D1 had better and more homogeneous behavior, and its wear was relatively low. It showed good mechanical endurance under dynamic loading conditions, with excellent response to axial compression fatigue loading without functional failure after long-term testing. CONCLUSION D1 performed better than D2. Further studies in cadaveric specimens, and eventually in a clinical setting, are recommended. Level of evidence 2c.
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Affiliation(s)
| | | | - Carlos M Atienza
- Instituto de Biomecánica (IBV), Universitat Politècnica de Valencia, Valencia, Spain
- Grupo de Tecnología Sanitaria (GTS-IBV), Instituto de Biomecánica de Valencia-CIBER BBN, Valencia, Spain
| | - Pablo Clavel
- Instituto Clavel, Hospital Quironsalud Barcelona, Barcelona, Spain
| | | | - Carlos Barrios
- Catholic University of Valencia, Saint Vincent Martyr, Valencia, Spain
| | - Leyre Vanaclocha
- Catholic University of Valencia, Saint Vincent Martyr, Valencia, Spain
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Biphasic Properties of PVAH (Polyvinyl Alcohol Hydrogel) Reflecting Biomechanical Behavior of the Nucleus Pulposus of the Human Intervertebral Disc. MATERIALS 2022; 15:ma15031125. [PMID: 35161069 PMCID: PMC8838070 DOI: 10.3390/ma15031125] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 01/26/2022] [Accepted: 01/27/2022] [Indexed: 11/24/2022]
Abstract
PVAH is a mixture of solid and fluid, but its mechanical behavior has usually been described using solid material models. The purpose of this study was to obtain material properties that can reflect the mechanical behavior of polyvinyl alcohol hydrogel (PVAH) using finite element analysis, a biphasic continuum model, and to optimize the composition ratio of PVAH to replace the nucleus pulposus (NP) of the human intervertebral disc. Six types of PVAH specimens (3, 5, 7, 10, 15, 20 wt%) were prepared, then unconfined compression experiments were performed to acquire their material properties using the Holmes–Mow biphasic model. With an increasing weight percentage of PVA in PVAH, the Young’s modulus increased while the permeability parameter decreased. The Young’s modulus and permeability parameter were similar to those of the NP at 15 wt% and 20 wt%. The range of motion, facet joint force, and NP pressures measured from dynamic motional analysis of the lumbar segments with the NP model also exhibited similar values to those with 15~20 wt% PVAH models. Considering the structural stability and pain of the lumbar segments, it appears that 20 wt% PVAH is most suitable for replacing the NP.
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Ma Z, Bao G, Li J. Multifaceted Design and Emerging Applications of Tissue Adhesives. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2007663. [PMID: 33956371 DOI: 10.1002/adma.202007663] [Citation(s) in RCA: 97] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 12/04/2020] [Indexed: 05/24/2023]
Abstract
Tissue adhesives can form appreciable adhesion with tissues and have found clinical use in a variety of medical settings such as wound closure, surgical sealants, regenerative medicine, and device attachment. The advantages of tissue adhesives include ease of implementation, rapid application, mitigation of tissue damage, and compatibility with minimally invasive procedures. The field of tissue adhesives is rapidly evolving, leading to tissue adhesives with superior mechanical properties and advanced functionality. Such adhesives enable new applications ranging from mobile health to cancer treatment. To provide guidelines for the rational design of tissue adhesives, here, existing strategies for tissue adhesives are synthesized into a multifaceted design, which comprises three design elements: the tissue, the adhesive surface, and the adhesive matrix. The mechanical, chemical, and biological considerations associated with each design element are reviewed. Throughout the report, the limitations of existing tissue adhesives and immediate opportunities for improvement are discussed. The recent progress of tissue adhesives in topical and implantable applications is highlighted, and then future directions toward next-generation tissue adhesives are outlined. The development of tissue adhesives will fuse disciplines and make broad impacts in engineering and medicine.
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Affiliation(s)
- Zhenwei Ma
- Department of Mechanical Engineering, McGill University, Montréal, QC, H3A 0C3, Canada
| | - Guangyu Bao
- Department of Mechanical Engineering, McGill University, Montréal, QC, H3A 0C3, Canada
| | - Jianyu Li
- Department of Mechanical Engineering, McGill University, Montréal, QC, H3A 0C3, Canada
- Department of Biomedical Engineering, McGill University, Montréal, QC, H3A 2B4, Canada
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La Barbera L, Villa T. ISO 12189 standard for the preclinical evaluation of posterior spinal stabilization devices--I: Assembly procedure and validation. Proc Inst Mech Eng H 2015; 230:122-33. [PMID: 26679431 DOI: 10.1177/0954411915621587] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 11/16/2015] [Indexed: 12/29/2022]
Abstract
The International Standardization Organization introduced standard 12189 for the preclinical evaluation of the mechanical reliability of posterior stabilization devices. The well-known vertebrectomy model formalized in standard F1717 by the American Society for Testing and Materials was modified with the introduction of a modular anterior support made up of three calibrated springs, which allows to describe a more realistic scenario, closer to the effective clinical use, as well to test even very flexible and dynamic posterior stabilization implants. Despite these important improvements, ISO 12189 received very little attention in the literature. The aim of the work is to provide a systematic procedure for the assembly and validation of a finite element model capable of describing the experimental test according to ISO 12189. The validated finite element model is able to catch very well the effective stiffness of the unassembled and assembled constructs (percentage differences <2% and <10%, respectively). As concern the assembled construct, the experimentally measured and predicted strains were found in a good agreement (R2 > 0.75, root mean square error < 30%), but the procedure without precompression lead to much better results (R2 > 0.96, root mean square error < 10%). Given the prediction errors of the assembled construct fall within the experimental range of repeatability, the finite element model can be systematically implemented to support the mechanical design of a variety of spinal implants, to quantitatively investigate the load-sharing mechanism, as well as to investigate the loading conditions set by ISO 12189 standard.
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Affiliation(s)
- Luigi La Barbera
- Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering 'Giulio Natta', Politecnico di Milano, Milano, Italy IRCCS Istituto Ortopedico Galeazzi, Milano, Italy
| | - Tomaso Villa
- Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering 'Giulio Natta', Politecnico di Milano, Milano, Italy IRCCS Istituto Ortopedico Galeazzi, Milano, Italy
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The application of fiber-reinforced materials in disc repair. BIOMED RESEARCH INTERNATIONAL 2013; 2013:714103. [PMID: 24383057 PMCID: PMC3870616 DOI: 10.1155/2013/714103] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 11/18/2013] [Indexed: 01/08/2023]
Abstract
The intervertebral disc degeneration and injury are the most common spinal diseases with tremendous financial and social implications. Regenerative therapies for disc repair are promising treatments. Fiber-reinforced materials (FRMs) are a kind of composites by embedding the fibers into the matrix materials. FRMs can maintain the original properties of the matrix and enhance the mechanical properties. By now, there are still some problems for disc repair such as the unsatisfied static strength and dynamic properties for disc implants. The application of FRMs may resolve these problems to some extent. In this review, six parts such as background of FRMs in tissue repair, the comparison of mechanical properties between natural disc and some typical FRMs, the repair standard and FRMs applications in disc repair, and the possible research directions for FRMs' in the future are stated.
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Schmidt H, Bashkuev M, Galbusera F, Wilke HJ, Shirazi-Adl A. Finite element study of human lumbar disc nucleus replacements. Comput Methods Biomech Biomed Engin 2013; 17:1762-76. [PMID: 23477684 DOI: 10.1080/10255842.2013.766722] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Currently, there are a number of nucleus replacements under development. The important concern is how well these implants duplicate the mechanical function of the native nucleus. This finite element model study aimed to investigate the influence of different nucleus replacements on the mechanical response of the disc. Models included partial, full, over-sized, partially saturated, elastic and poroelastic solid replacements. Over-sized nucleus replacements up to 25% yielded results that were comparable to those in the intact state. Differences were much greater in cases with under-sized nucleus replacements. The effect was most pronounced for the 75% under-sized replacement that resembled the condition with a full nucleotomy. Nucleus implants with elastic properties substantially altered load transmission when 10% under-sized and over-sized replacements were considered. Compared to intact, the under-sized implants should be avoided when using biphasic materials with properties similar to the native nucleus, whereas for elastic replacements both under- and over-sized implants should not be used.
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Affiliation(s)
- Hendrik Schmidt
- a Julius Wolff Institut, Charité - Universitätsmedizin Berlin, CVK , Institutsgebäude Süd/Südstraße 2, Augustenburger Platz 1, 13353 Berlin , Germany
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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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Lewis G. Nucleus pulposus replacement and regeneration/repair technologies: present status and future prospects. J Biomed Mater Res B Appl Biomater 2012; 100:1702-20. [PMID: 22566484 DOI: 10.1002/jbm.b.32712] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 02/19/2012] [Accepted: 03/18/2012] [Indexed: 12/28/2022]
Abstract
Degenerative disc disease is implicated in the pathogenesis of many painful conditions of the back, chief among which is low back pain. Acute and/or chronic low back pain (A/CLBP) afflicts a large number of people, thus making it a major healthcare issue with concomitant cost ramifications. When conservative treatments for A/CLBP, such as bed rest, anti-inflammatory medications, and physical therapy, prove to be ineffectual, surgical options are recommended. The most popular of these is discectomy followed by fusion. Although there are many reports of good to excellent outcomes with this method, there are concerns, such as long-term adverse biomechanical consequences to adjacent functional spinal unit(s). A surgical option that has been attracting much attention recently is replacement or regeneration/repair of the nucleus pulposus, an approach that holds the prospect of not compromising either mobility or function and causing no adjacent-level injury. There is a sizeable body of literature highlighting this option, comprising in vitro biomechanical studies, finite element analyses, animal-model studies, and limited clinical evaluations. This work is a review of this body of literature and is organized into four parts, with the focus being on replacement technologies, regeneration/repair technologies, and detailed expositions on 14 areas for future study. This review ends with a summary of the salient points made.
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Affiliation(s)
- Gladius Lewis
- Department of Mechanical Engineering, The University of Memphis, Memphis, Tennessee 38152, USA.
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Sasson A, Patchornik S, Eliasy R, Robinson D, Haj-Ali R. Hyperelastic mechanical behavior of chitosan hydrogels for nucleus pulposus replacement—Experimental testing and constitutive modeling. J Mech Behav Biomed Mater 2012; 8:143-53. [DOI: 10.1016/j.jmbbm.2011.12.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 12/14/2011] [Accepted: 12/18/2011] [Indexed: 10/14/2022]
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Massey CJ, van Donkelaar CC, Vresilovic E, Zavaliangos A, Marcolongo M. Effects of aging and degeneration on the human intervertebral disc during the diurnal cycle: a finite element study. J Orthop Res 2012; 30:122-8. [PMID: 21710607 DOI: 10.1002/jor.21475] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Accepted: 05/16/2011] [Indexed: 02/04/2023]
Abstract
A significant biochemical change that takes place in intervertebral disc degeneration is the loss of proteoglycans in the nucleus pulposus. Proteoglycans attract fluid, which works to reduce mechanical stresses in the solid matrix of the nucleus and provide a hydrostatic pressure to the annulus fibrosus, whose fibrous nature accommodates this stress. Our goals are to develop an osmo-poroelastic finite element model to study the relationship between proteoglycan content and the stress distribution within the disc and to analyze the effects of degeneration on the disc's diurnal mechanical response. Stress in the annulus increased with degeneration from ∼0.2 to 0.4 MPa, and an increase occurred in the center of the nucleus from 1.2 to 1.6 MPa. The osmotic pressure in the central nucleus region decreased the most with degeneration, from ∼0.42 to ∼0.1 MPa in a severely dehydrated disc. A 3% decrease in diurnal fluid lost with degeneration equated to ∼21% decrease in fluid exchange, and hence a decrease in nutrients that require convection to enter the disc. We quantified the increases in internal stresses in the nucleus and annulus throughout the various stages of degeneration, suggesting that these changes lead to further remodeling of the tissue.
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Affiliation(s)
- Christopher J Massey
- Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA
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Fill of the nucleus cavity affects mechanical stability in compression, bending, and torsion of a spine segment, which has undergone nucleus replacement. Spine (Phila Pa 1976) 2010; 35:1128-35. [PMID: 20473120 DOI: 10.1097/brs.0b013e3181bdbb1a] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Axial loading, rotation, and bending were applied to human cadaveric lumbar segments to investigate the changes in disc mechanics with denucleation and incremental delivery of a novel hydrogel nucleus replacement. OBJECTIVE The purpose of this study was to investigate the effect of nucleus implant injection pressure/volume relationships on the quasi-static mechanical behavior of the human cadaveric lumbar intervertebral disc to determine if intact biomechanics could be reproduced with nucleus-implanted discs. SUMMARY OF BACKGROUND DATA Previous studies have shown that volumetric filling of the nucleus cavity with a compliant nucleus replacement device will affect compressive stiffness of the implanted intervertebral disc, but data regarding restoration of mechanics through cavity pressurization are lacking. METHODS A total of 12 intact lumbar anterior column units were loaded in series in axial loading, axial rotation, lateral bending, and flexion/extension (FE). Each segment was fully denucleated and implanted with a hydrogel nucleus replacement using pressurization between 12 psi and 40 psi. Range of motion (ROM), neutral zone (NZ), energy dissipation (HYS), disc height (DH), and stiffness were compared among the intact, denucleated, and implanted conditions. RESULTS Denucleation significantly destabilized the segments compared to intact controls as shown by increased ROM, NZ, and HYS, and decreased DH and stiffness through the NZ. As the nucleus cavity was repressurized with increasing volumes of hydrogel implant, the segments were stabilized and DH was restored to the intact level. No significant differences from intact were observed in any loading direction for ROM, NZ, or DH after the segments were implanted with the nucleus replacement device using inflation pressures between 20 psi and 40 psi. CONCLUSION Compliant nucleus replacement using inflation pressures of 20 to 40 psi resulted in restoration of intact mechanics. Mechanical function was dependent on the volume of implant injected into the nucleus cavity.
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Joshi A, Massey CJ, Karduna A, Vresilovic E, Marcolongo M. The effect of nucleus implant parameters on the compressive mechanics of the lumbar intervertebral disc: a finite element study. J Biomed Mater Res B Appl Biomater 2009; 90:596-607. [PMID: 19180527 DOI: 10.1002/jbm.b.31322] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A simplified finite element model of the human lumbar intervertebral disc was utilized for understanding nucleus pulposus implant mechanics. The model was used to assess the effect of nucleus implant parameter variations on the resulting compressive biomechanics of the lumbar anterior column unit. The effects of nucleus implant material (modulus and Poisson's ratio) and geometrical (height and diameter) parameters on the mechanical behavior of the disc were investigated. The model predicted that variations in implant modulus contribute less to the compressive disc mechanics compared to the implant geometrical parameters, for the ranges examined. It was concluded that some threshold exists for the nucleus implant modulus, below which little variations in load-displacement behavior were shown. Compressive biomechanics were highly affected by implant volume (under-filling the nucleus cavity, line-to-line fit, or over-filling the nucleus cavity) with a greater restoration of compressive mechanics observed with the over-filled implant design. This work indicated the effect of nucleus implant parameter variations on the compressive mechanics of the human lumbar intervertebral disc and importance of the "fit and fill" effect of the nuclear cavity in the restoration of the human intervertebral disc mechanics in compression. These findings may have clinical significance for nucleus implant design.
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Affiliation(s)
- Abhijeet Joshi
- Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania, USA
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Buttermann GR, Beaubien BP. Biomechanical characterization of an annulus-sparing spinal disc prosthesis. Spine J 2009; 9:744-53. [PMID: 19540816 PMCID: PMC2730998 DOI: 10.1016/j.spinee.2009.04.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2008] [Revised: 03/21/2009] [Accepted: 04/20/2009] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Current spine arthroplasty devices require disruption of the annulus fibrosus for implantation. Preliminary studies of a unique annulus-sparing intervertebral prosthetic disc (IPD) found that preservation of the annulus resulted in load sharing of the annulus with the prosthesis. PURPOSE Determine flexibility of the IPD versus fusion constructs in normal and degenerated human spines. STUDY DESIGN/SETTING Biomechanical comparison of motion segments in the intact, fusion and mechanical nucleus replacement states for normal and degenerated states. PATIENT SETTING: Thirty lumbar motion segments. OUTCOMES MEASURES Intervertebral height; motion segment range of motion, neutral zone, stiffness. METHODS Motion segments had multidirectional flexibility testing to 7.5Nm for intact discs, discs reconstructed using the IPD (n=12), or after anterior/posterior fusions (n=18). Interbody height and axial compression stiffness changes were determined for the reconstructed discs by applying axial compression to 1,500N. Analysis included stratifying results to normal mobile versus rigid degenerated intact motion segments. RESULTS The mean interbody height increase was 1.5mm for IPD reconstructed discs versus 3.0mm for fused segments. Axial compression stiffness was 3.0+/-0.9kN/mm for intact compared with 1.2+/-0.4kN/mm for IPD reconstructed segments. Reconstructed disc ROM was 9.0 degrees +/-3.7 degrees in flexion extension, 10.6 degrees +/-3.4 degrees in lateral bending, and 2.8 degrees +/-1.4 degrees in axial torsion that was similar to intact values and significantly greater than respective fusion values (p<.001). Mobile intact segments exhibited significantly greater rotation after fusion versus their more rigid counterparts (p<.05); however, intact motion was not related to motion after IPD reconstruction. The NZ and rotational stiffness followed similar trends. Differences in NZ between mobile and rigid intact specimens tended to decrease in the IPD reconstructed state. CONCLUSION The annulus-sparing IPD generally reproduced the intact segment biomechanics in terms of ROM, NZ, and stiffness. Furthermore, the IPD reconstructed discs imparted stability by maintaining a small neutral zone. The IPD reconstructed discs were significantly less rigid than the fusion constructs and may be an attractive alternative for the treatment of degenerative disc disease.
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Affiliation(s)
- Glenn R Buttermann
- Midwest Spine Institute, Spine Surgery Division, 1950 Curve Crest Boulevard, Stillwater, MN 55082, USA.
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Wang JL, Tsai YC, Wang YH. The leakage pathway and effect of needle gauge on degree of disc injury post anular puncture: a comparative study using aged human and adolescent porcine discs. Spine (Phila Pa 1976) 2007; 32:1809-15. [PMID: 17762287 DOI: 10.1097/brs.0b013e31811ec282] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN An in vitro biomechanical study using aged human and adolescent porcine discs. OBJECTIVES To find the leakage pathway and effect of needle gauge on the degree of disc injury post anular puncture. SUMMARY OF BACKGROUND DATA Spinal needles are widely used for minimal invasive disc surgeries and disc degeneration/regeneration research. Applications of anular puncture require different diameters of spinal needles. However, the effect of needle diameters on the disc injury has not been systematically studied yet. METHODS Four groups of experiments were conducted: 1) porcine thoracic disc, 2) human thoracic disc, 3) porcine thoracic disc with 200 N external loading, and 4) porcine lumbar discs. The disc was punctured consecutively with needles from smaller diameter to larger diameter. After each anular puncture, the quantitative discomanometry technique was conducted to quantify the disc rupture pressure and volume. The association between needle gauge and rupture pressure and volume was analyzed. RESULTS The degree of disc injury increased with the diameter of needle. For an aged human thoracic disc, the anulus fibrosus cannot hold pressure more than 2 MPa after a 21-gauge-needle-anular-puncture. The leakage pathway of injected saline was through the anular fissure but was through the endplate when the disc was next to an osteoporotic vertebrae. The pressure holding power of porcine disc is stronger than of human disc. The rupture pressure of porcine lumbar disc is higher than of porcine thoracic disc. The axial compressive external loading increased the disc rupture pressure. The rupture volumes were not affected by the dimension of injury fissure. The rupture volume was at level of 0.3 mL without external loading and at 0.2 mL with external loading. CONCLUSION A spinal needle of < or = 22 gauge and injection volume of < or = 0.2 mL are recommended to prevent postsurgery leakage.
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Affiliation(s)
- Jaw-Lin Wang
- Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan.
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Cloyd JM, Malhotra NR, Weng L, Chen W, Mauck RL, Elliott DM. Material properties in unconfined compression of human nucleus pulposus, injectable hyaluronic acid-based hydrogels and tissue engineering scaffolds. 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 2007; 16:1892-8. [PMID: 17661094 PMCID: PMC2223355 DOI: 10.1007/s00586-007-0443-6] [Citation(s) in RCA: 191] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Revised: 05/03/2007] [Accepted: 07/03/2007] [Indexed: 12/22/2022]
Abstract
Surgical treatment for lower back pain related to degenerative disc disease commonly includes discectomy and spinal fusion. While surgical intervention may provide short-term pain relief, it results in altered biomechanics of the spine and may lead to further degenerative changes in adjacent segments. One non-fusion technique currently being investigated is nucleus pulposus (NP) support via either an injectable hydrogel or tissue engineered construct. A major challenge for either approach is to mimic the mechanical properties of native NP. Here we adopt an unconfined compression testing configuration to assess toe-region and linear-region modulus and Poisson's ratio, key functional parameters for NP replacement. Human NP, experimental biocompatible hydrogel formulations composed of hyaluronic acid (HA), PEG-g-chitosan, and gelatin, and conventional alginate and agarose gels were investigated as injectable NP replacements or tissue engineering scaffolds. Testing consisted of a stress-relaxation experiment of 5% strain increments followed by 5-min relaxation periods to a total of 25% strain. Human NP had an average linear-region modulus of 5.39 +/- 2.56 kPa and a Poisson's ratio of 0.62 +/- 0.15. The modulus and Poisson's ratio are important parameters for evaluating the design of implant materials and scaffolds. The synthetic HA-based hydrogels approximated NP well and may serve as suitable NP implant materials.
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Affiliation(s)
- Jordan M. Cloyd
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, 424 Stemmler Hall, Philadelphia, PA 19104-6081 USA
| | - Neil R. Malhotra
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, 424 Stemmler Hall, Philadelphia, PA 19104-6081 USA
- Department of Neurological Surgery, University of Pennsylvania, Philadelphia, PA USA
| | - Lihui Weng
- Department of Biomedical Engineering, State University of New York, Stony Brook, NY USA
| | - Weiliam Chen
- Department of Biomedical Engineering, State University of New York, Stony Brook, NY USA
| | - Robert L. Mauck
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, 424 Stemmler Hall, Philadelphia, PA 19104-6081 USA
| | - Dawn M. Elliott
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, 424 Stemmler Hall, Philadelphia, PA 19104-6081 USA
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Wang YH, Kuo TF, Wang JL. The implantation of non-cell-based materials to prevent the recurrent disc herniation: an in vivo porcine model using quantitative discomanometry examination. 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 2007; 16:1021-7. [PMID: 17252217 PMCID: PMC2219663 DOI: 10.1007/s00586-007-0306-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2006] [Revised: 10/27/2006] [Accepted: 12/20/2006] [Indexed: 10/23/2022]
Abstract
Recurrent disc herniation is frequently observed due to leakage of nucleus pulposus through injured anulus fibrosus. There is no effective treatment to prevent recurrent disc herniation yet. In this study, we proposed to implant non-cell-based materials into the porcine disc to stimulate the growth of fibrous tissue and thereby increase the disc functional integrity. The disc herniation was simulated by anular punctures using the spinal needles. Four clinically used implantation materials, i.e., gelfoam, platinum coil, bone cement and tissue glue, were delivered into the discs via percutaneous spinal needles. Two months after the surgery, the swine were killed. The degree of disc integrity of intact, naturally healed and implanted discs, was examined by quantitative discomanometry apparatus. We found the disc injury could not recover after 2 months of healing, and the disc implantation affected the degree of disc integrity. The disc integrity of gelfoam-implanted discs was better than that of coil-, bone cement-, and glue-implanted discs. The implantation of non-cell-based material was proved to be a potentially clinically applicable method to recover the integrity of injured discs and to prevent recurrent disc herniation.
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Affiliation(s)
- Yao-Hung Wang
- Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, ROC
- Department of Medical Imaging, National Taiwan University Hospital, Taipei, Taiwan, ROC
| | - Tzong-Fu Kuo
- Institute of Veterinary Medicine, National Taiwan University, Taipei, Taiwan, ROC
| | - Jaw-Lin Wang
- Institute of Biomedical Engineering, College of Engineering and College of Medicine, National Taiwan University, #1, Section 1, Jen-Ai Road, Taipei, 10051 Taiwan, ROC
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Abstract
UNLABELLED Lumbar disc herniation is among the most common causes of lower-back pain and sciatica. The cause(s) of lumbar disc herniation and the relation of lumbar disc herniation to back pain and sciatica have not been fully elucidated, but most likely comprise a complex combination of mechanical and biologic processes. Furthermore, the natural history of lumbar disc herniation seems generally to be favorable, leaving the optimum treatment for lumbar disc herniation a debate in the literature. Various nonoperative and operative treatment strategies have been tried with varying degrees of success. Treatment often involves patient education, physical therapy, alternative medicine options, and pharmaco-therapy. If these fail, surgical intervention is usually recommended. A literature search was conducted to evaluate the currently known effectiveness of traditional and novel non-operative and surgical techniques for the treatment lumbar disc herniation and to determine if there are substantive new advantages in these newer contemporary treatments or combinations thereof. A structured approach to treatment of a patient who may have a symptomatic lumbar disc herniation is presented, based on analysis of the current literature. No one method of nonoperative or operative treatment would seem definitively to be superior to another. Appropriate multidisciplinary treatment including behavioral analysis and support may offer the hope of improved outcomes for patients with lumbar disc herniation. LEVEL OF EVIDENCE Level V (expert opinion). See the Guidelines for Authors for a complete description of the levels of evidence.
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Affiliation(s)
- John N Awad
- New York University-Hospital for Joint Diseases, New York, NY 10003, USA
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