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Ganko R, Madhavan A, Hamouda W, Muthu S, Jain A, Yoon ST, El-Rozz H, Cyril D, Pabbruwe M, Tipper JL, Tavakoli J. Spinal implant wear particles: Generation, characterization, biological impacts, and future considerations. iScience 2025; 28:112193. [PMID: 40212584 PMCID: PMC11982499 DOI: 10.1016/j.isci.2025.112193] [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] [Indexed: 04/02/2025] Open
Abstract
The generation of wear debris from orthopedic implants is a known cause of implant failure, particularly in joint replacements. While much research has focused on wear particles from knee and hip implants, spinal implants, such as total disc replacements (TDRs), have received less attention despite their increasing clinical use. Spinal implants face unique biomechanical challenges, including a wider range of motion and higher loads, leading to complex tissue interactions. Studies reveal that TDR wear particles, though similar in size to those from knee implants, cause a stronger immune response, with more macrophages and giant cells found in the surrounding tissue. This may explain the high revision rates seen in spinal surgeries, with some interventions failing in over 30% of cases within 10 years. The younger population undergoing spinal surgery, combined with the productivity losses associated with implant failure, underscores the need for greater understanding. This review discusses recent research on the generation, characterization, and biological impacts of spinal implant wear debris. It draws on retrieval analysis, wear simulation, in vivo models, and a survey conducted with the AO Spine Knowledge Forum Degenerative to assess current clinical practices and highlight gaps in knowledge. Additionally, this critical review explores future strategies to reduce the biological impact of wear particles and improve the safety and longevity of spinal implants through better therapeutics and design innovations. By combining literature and clinical insights, this paper aims to guide future research in addressing the complexities of spinal implant wear and its biological consequences.
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Affiliation(s)
- Renata Ganko
- School of Biomedical Engineering, Faculty of Eng and Information Technology, University of Technology Sydney, Ultimo, NSW, Australia
| | - Aswini Madhavan
- School of Biomedical Engineering, Faculty of Eng and Information Technology, University of Technology Sydney, Ultimo, NSW, Australia
| | - Waeel Hamouda
- Department of Neurosurgery, Kasr Alainy Faculty of Medicine, Research, and Teaching Hospitals, Cairo University, Cairo, Egypt
- Department of Neurosurgery, Security Forces Hospital, Dammam, Saudi Arabia
| | - Sathish Muthu
- Department of Orthopaedics, Government Medical College, Karur, India
- Orthopaedic Research Group, Coimbatore, Tamil Nadu, India
- Department of Biotechnology, Karpagam Academy of Higher Education, Coimbatore, Tamil Nadu, India
| | - Amit Jain
- Department of Orthopaedic Surgery, Johns Hopkins University, Baltimore, MD, USA
| | - S. Tim Yoon
- Department of Orthopaedic Surgery, Emory University, Atlanta, GA, USA
| | - Hiba El-Rozz
- School of Biomedical Engineering, Faculty of Eng and Information Technology, University of Technology Sydney, Ultimo, NSW, Australia
| | - Divya Cyril
- School of Biomedical Engineering, Faculty of Eng and Information Technology, University of Technology Sydney, Ultimo, NSW, Australia
| | - Moreica Pabbruwe
- Centre for Implant Retrieval and Analysis, Royal Perth Hospital, Perth, WA, Australia
| | - Joanne L. Tipper
- School of Biomedical Engineering, Faculty of Eng and Information Technology, University of Technology Sydney, Ultimo, NSW, Australia
- School of Engineering, RMIT University, Melbourne, VIC 3001, Australia
- School of Mechanical Engineering, University of Leeds, Leads, UK
| | - Javad Tavakoli
- School of Biomedical Engineering, Faculty of Eng and Information Technology, University of Technology Sydney, Ultimo, NSW, Australia
- School of Engineering, RMIT University, Melbourne, VIC 3001, Australia
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Yang S, Sun T, Zhang L, Cong M, Guo A, Liu D, Song M. Stress Distribution of Different Pedicle Screw Insertion Techniques Following Single-Segment TLIF: A Finite Element Analysis Study. Orthop Surg 2023; 15:1153-1164. [PMID: 36855914 PMCID: PMC10102325 DOI: 10.1111/os.13671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 12/28/2022] [Accepted: 01/03/2023] [Indexed: 03/02/2023] Open
Abstract
OBJECTIVES At present, a variety of posterior lumbar internal fixation implantation methods have been developed, which makes it difficult for spine surgeons to choose. The stress distribution of the internal fixation system is one of the important indexes to evaluate these technologies. Common insertion technologies include Roy Camille, Magerl, Krag, AO, and Weinstein insertion techniques. This study aimed to compare the distribution of von Mises stresses in different screw fixation systems established by these insertion technologies. METHODS Here, the three-dimensional finite element (FE) method was selected to evaluate the postoperative stress distribution of internal fixation. Following different pedicle screw insertion techniques, five single-segment transforaminal lumbar interbody fusion (TLIF) models were established after modeling and validation of the L1-S1 vertebrae FE model. RESULTS By analyzing the data, we found that stress concentration phenomenon was in all the models. Additionally, Roy-Camille, Krag, AO, and Weinstein insertion techniques led to the great stress on lumbar vertebra, intervertebral disc, and screw-rod fixation systems. Therefore, we hope that the results can provide ideas for clinical work and development of pedicle screws in the future. It is worth noting that flexion, unaffected side lateral bending, and affected side axial rotation should be limited for the patients with cages implanted. CONCLUSIONS Overall, our method obtained the results that Magerl insertion technique was the relatively safe approach for pedicle screw implantation due to its relatively dispersive stress in TLIF models.
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Affiliation(s)
- Simengge Yang
- Department of Orthopaedics, The First Affiliated Hospital of Dalian Medical University, Dalian, China.,Department of Orthopedics, The Second Xiangya Hospital of Central South University, Changsha, China
| | - Tianze Sun
- Department of Orthopaedics, The First Affiliated Hospital of Dalian Medical University, Dalian, China
| | - Liwen Zhang
- Department of Orthopaedics, The First Affiliated Hospital of Dalian Medical University, Dalian, China
| | - Menglin Cong
- Department of Orthopedics, Qilu Hospital of Shandong University, Jinan, China
| | - Anyun Guo
- Department of Joint Trauma, General Hospital of Shenzhen University, Shenzhen, China
| | - Dakai Liu
- Department of Orthopaedics, The Second People's Hospital of Dalian, Dalian, China
| | - Mingzhi Song
- Department of Orthopaedics, The First Affiliated Hospital of Dalian Medical University, Dalian, China.,Department of Orthopaedics, The Third Affiliated Hospital of Dalian Medical University, Dalian, China
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Vanaclocha-Saiz A, Vanaclocha V, Atienza C, Jorda-Gomez P, Primo-Capella V, Barrios C, Vanaclocha L. Bionate Biocompatibility: In Vivo Study in Rabbits. ACS OMEGA 2022; 7:29647-29654. [PMID: 36061708 PMCID: PMC9435029 DOI: 10.1021/acsomega.2c01690] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Accepted: 08/10/2022] [Indexed: 06/15/2023]
Abstract
Response to foreign materials includes local tissue reaction, osteolysis, implant loosening, and migration to lymph nodes and organs. Bionate 80A human explants show minor wear and slight local tissue reaction, but we do not know the response at the spinal cord, nerve roots, lymph nodes, or distant organs. This study aims to figure out reactions against Bionate 80A when implanted at the spinal epidural space of 24 20-week-old New Zealand white rabbits. In one group of 12 rabbits, we implanted Bionate 80A on the spinal epidural space, and another group of 12 rabbits was used as the control group. We studied tissues, organs, and tissue damage markers on blood biochemistry, urine tests, and necropsy. The animals' clinical parameters and weight showed no statistically significant differences. At 3 months, the basophils increased slightly in the implant group, platelets decreased in all, and at 6 months, implanted animals showed slight eosinophilia, but none of these changes was statistically significant. External, organ, and spinal tissue examination showed neither toxic reaction, inflammatory changes, or noticeable differences between groups or survival periods. Under microscopic examination, the Bionate 80A particles induced a chronic granulomatous response always outside the dura mater, with giant multinucleated cells holding phagocytized particles and no particle migration to lymph nodes or organs. Thus, it was concluded that Bionate particles, when implanted in the rabbit lumbar epidural space, do not generate a significant reaction limited to the surrounding soft tissues with giant multinucleated cells. In addition, the particles did not cross the dura mater or migrate to lymph nodes or organs.
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Affiliation(s)
- Amparo Vanaclocha-Saiz
- Instituto de Biomecánica (IBV), Universitat Politècnica de Valencia, Valencia 46022, Spain
| | | | - Carlos Atienza
- Instituto de Biomecánica (IBV), Universitat Politècnica de Valencia, Valencia 46022, Spain
| | - Pablo Jorda-Gomez
- Hospital General Universitario de Castellón, Castellón de la Plana 12004, Spain
| | - Víctor Primo-Capella
- Instituto de Biomecánica (IBV), Universitat Politècnica de Valencia, Valencia 46022, Spain
| | - Carlos Barrios
- Catholic University of Valencia, Saint Vincent Martyr, Valencia 46001, Spain
| | - Leyre Vanaclocha
- Medius Klinik, Ostfildern-Ruit Klinik für Urologie, Hedelfinger Strasse 166, 73760 Ostfildern, Germany
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Biomechanical Comparison between Isobar and Dynamic-Transitional Optima (DTO) Hybrid Lumbar Fixators: A Lumbosacral Finite Element and Intersegmental Motion Analysis. BIOMED RESEARCH INTERNATIONAL 2022; 2022:8273853. [PMID: 35845942 PMCID: PMC9286886 DOI: 10.1155/2022/8273853] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 06/27/2022] [Indexed: 11/18/2022]
Abstract
Biomechanical performance of longitudinal component in dynamic hybrid devices was evaluated to display the load-transfer effects of Dynesys cord spacer or Isobar damper-joint dynamic stabilizer on junctional problem based on various disc degenerations. The dynamic component was adapted at the mildly degenerative L3–L4 segment, and the static component was fixed at the moderately degenerative L4–L5 segment under a displacement-controlled mode for the finite element study. Furthermore, an intersegmental motion behavior was analyzed experimentally on the synthetic model under a load-controlled mode. Isobar or DTO hybrid fixator could reduce stress/motion at transition segment, but compensation was affected at the cephalic adjacent segment more than the caudal one. Within the trade-off region (as a motion-preserving balance between the transition and adjacent segments), the stiffness-related problem was reduced mostly in flexion by a flexible Dynesys cord. In contrast, Isobar damper afforded the effect of maximal allowable displacement (more than peak axial stiffness) to reduce stress within the pedicle and at facet joint. Pedicle-screw travel at transition level was related to the extent of disc degeneration in Isobar damper-joint (more than Dynesys cord spacer) attributing to the design effect of axial displacement and angular rotation under motion. In biomechanical characteristics relevant to clinical use, longitudinal cord/damper of dynamic hybrid lumbar fixators should be designed with less interface stress occurring at the screw-vertebral junction and facet joint to decrease pedicle screw loosening/breakage under various disc degenerations.
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Ford A, Hua Z, Ferguson SJ, Pruitt LA, Gao L. A 3D-transient elastohydrodynamic lubrication hip implant model to compare ultra high molecular weight polyethylene with more compliant polycarbonate polyurethane acetabular cups. J Mech Behav Biomed Mater 2021; 119:104472. [PMID: 33813334 DOI: 10.1016/j.jmbbm.2021.104472] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 10/20/2020] [Accepted: 03/14/2021] [Indexed: 10/21/2022]
Abstract
Wear remains a significant challenge in the design of orthopedic implants such as total hip replacements. Early elastohydrodynamic lubrication modeling has predicted thicker lubrication films in hip replacement designs with compliant polycarbonate polyurethane (PCU) bearing materials compared to stiffer materials like ultra-high molecular weight polyethylene (UHMWPE). The predicted thicker lubrication films suggest improved friction and wear performance. However, when compared to the model predictions, experimental wear studies showed mixed results. The mismatch between the model and experimental results may lie in the simplifying assumptions of the early models such as: steady state conditions, one dimensional rotation and loading, and high viscosities. This study applies a 3D-transient elastohydrodynamic model based on an ISO standard gait cycle to better understand the interaction between material stiffness and film thickness in total hip arthroplasty material couples. Similar to previous, simplified models, we show that the average and central film thickness of PCU (∼0.4μm) is higher than that of UHMWPE (∼0.2μm). However, in the 3D-transient model, the film thickness distribution was largely asymmetric and the minimum film thickness occurred outside of the central axis. Although the overall film thickness of PCU was higher than UHMWPE, the minimum film thickness of PCU was lower than UHMPWE for the majority of the gait cycle. The minimum film thickness of PCU also had a larger range throughout the gait cycle. Both materials were found to be operating between boundary and mixed lubrication regimes. This 3D-transient model reveals a more nuanced interaction between bearing material stiffness and film thickness that supports the mixed results found in experimental wear studies of PCU hip implant designs.
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Affiliation(s)
- Audrey Ford
- Department of Mechanical Engineering, 6141 Etcheverry Hall, Mail Code 1740, University of California Berkeley, Berkeley, CA 94720-1740, USA
| | - Zikai Hua
- School of Mechatronics Engineering and Automation, Shanghai University, 266 Jufengyuan Rd, Baoshan, Shanghai, China
| | - Stephen J Ferguson
- Institute for Biomechanics, ETH Zurich, Leopold-Ruzicka-Weg 4, 8093 Zurich, Switzerland
| | - Lisa A Pruitt
- Department of Mechanical Engineering, 6141 Etcheverry Hall, Mail Code 1740, University of California Berkeley, Berkeley, CA 94720-1740, USA
| | - Leiming Gao
- Engineering Department, School of Science and Technology, Nottingham Trent University, 50 Shakespeare Street, Nottingham, NG1 4FG, United Kingdom.
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Dorrepaal RM, Lawless BM, Burton HE, Espino DM, Shepherd DE, Gowen AA. Hyperspectral chemical imaging reveals spatially varied degradation of polycarbonate urethane (PCU) biomaterials. Acta Biomater 2018; 73:81-89. [PMID: 29626697 DOI: 10.1016/j.actbio.2018.03.045] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 03/12/2018] [Accepted: 03/28/2018] [Indexed: 11/26/2022]
Abstract
Hyperspectral chemical imaging (HCI) is an emerging technique which combines spectroscopy with imaging. Unlike traditional point spectroscopy, which is used in the majority of polymer biomaterial degradation studies, HCI enables the acquisition of spatially localised spectra across the surface of a material in an objective manner. Here, we demonstrate that attenuated total reflectance Fourier transform infra-red (ATR-FTIR) HCI reveals spatial variation in the degradation of implantable polycarbonate urethane (PCU) biomaterials. It is also shown that HCI can detect possible defects in biomaterial formulation or specimen production; these spatially resolved images reveal regional or scattered spatial heterogeneity. Further, we demonstrate a map sampling method, which can be used in time-sensitive scenarios, allowing for the investigation of degradation across a larger component or component area. Unlike imaging, mapping does not produce a contiguous image, yet grants an insight into the spatial heterogeneity of the biomaterial across a larger area. These novel applications of HCI demonstrate its ability to assist in the detection of defective manufacturing components and lead to a deeper understanding of how a biomaterial's chemical structure changes due to implantation. STATEMENT OF SIGNIFICANCE The human body is an aggressive environment for implantable devices and their biomaterial components. Polycarbonate urethane (PCU) biomaterials in particular were investigated in this study. Traditionally one or a few points on the PCU surface are analysed using ATR-FTIR spectroscopy. However the selection of acquisition points is susceptible to operator bias and critical information can be lost. This study utilises hyperspectral chemical imaging (HCI) to demonstrate that the degradation of a biomaterial varies spatially. Further, HCI revealed spatial variations of biomaterials that were not subjected to oxidative degradation leading to the possibility of HCI being used in the assessment of biomaterial formulation and/or component production.
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Kanca Y, Milner P, Dini D, Amis AA. Tribological evaluation of biomedical polycarbonate urethanes against articular cartilage. J Mech Behav Biomed Mater 2018; 82:394-402. [DOI: 10.1016/j.jmbbm.2018.04.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 04/01/2018] [Accepted: 04/03/2018] [Indexed: 01/17/2023]
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Ford AC, Gramling H, Li SC, Sov JV, Srinivasan A, Pruitt LA. Micromechanisms of fatigue crack growth in polycarbonate polyurethane: Time dependent and hydration effects. J Mech Behav Biomed Mater 2018; 79:324-331. [DOI: 10.1016/j.jmbbm.2018.01.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 01/03/2018] [Accepted: 01/09/2018] [Indexed: 11/30/2022]
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Lawless BM, Espino DM, Shepherd DET. In vitro oxidative degradation of a spinal posterior dynamic stabilization device. J Biomed Mater Res B Appl Biomater 2017; 106:1237-1244. [PMID: 28580771 DOI: 10.1002/jbm.b.33913] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 03/27/2017] [Accepted: 04/22/2017] [Indexed: 11/10/2022]
Abstract
This study quantified the changes of the frequency-dependant viscoelastic properties of the BDyn (S14 Implants, Pessac, France) spinal posterior dynamic stabilization (PDS) device due to in vitro oxidation. Six polycarbonate urethane (PCU) rings and six silicone cushions were degraded using a 20% hydrogen peroxide/0.1 M cobalt (II) chloride hexahydrate, at 37°C, for 24 days. The viscoelastic properties of the individual components and the components assembled into the BDyn PDS device were determined using Dynamic Mechanical Analysis at frequencies from 0.01 to 30 Hz. Attenuated Total Reflectance Fourier Transform Infra-Red spectra demonstrated chemical structure changes, of the PCU, associated with oxidation while Scanning Electron Microscope images revealed surface pitting. No chemical structure or surface morphology changes were observed for the silicone cushion. The BDyn device storage and loss stiffness ranged between 84.46 N/mm to 99.36 N/mm and 8.13 N/mm to 21.99 N/mm, respectively. The storage and loss stiffness for the components and BDyn device increased logarithmically with respect to frequency. Viscoelastic properties, between normal and degraded components, were significantly different for specific frequencies only. This study demonstrates the importance of analyzing changes of viscoelastic properties of degraded biomaterials and medical devices into which they are incorporated, using a frequency sweep. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1237-1244, 2018.
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Affiliation(s)
- Bernard M Lawless
- Department of Mechanical Engineering, School of Engineering, University of Birmingham, Birmingham, UK
| | - Daniel M Espino
- Department of Mechanical Engineering, School of Engineering, University of Birmingham, Birmingham, UK
| | - Duncan E T Shepherd
- Department of Mechanical Engineering, School of Engineering, University of Birmingham, Birmingham, UK
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Park WM, Kim CH, Kim YH, Chung CK, Jahng TA. The Change of Sagittal Alignment of the Lumbar Spine after Dynesys Stabilization and Proposal of a Refinement. J Korean Neurosurg Soc 2015; 58:43-9. [PMID: 26279812 PMCID: PMC4534738 DOI: 10.3340/jkns.2015.58.1.43] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 02/22/2015] [Accepted: 02/27/2015] [Indexed: 11/27/2022] Open
Abstract
Objective Dynesys® is one of the pedicle-based dynamic lumbar stabilization systems and good clinical outcome has been reported. However, the cylindrical spacer between the heads of the screws undergoes deformation during assembly of the system. The pre-strain probably change the angle of instrumented spine with time and oblique-shaped spacer may reduce the pre-strain. We analyzed patients with single-level stabilization with Dynesys® and simulated oblique-shaped spacer with finite element (FE) model analysis. Methods Consecutive 14 patients, who underwent surgery for single-level lumbar spinal stenosis and were followed-up more than 24 months (M : F=6 : 8; age, 58.7±8.0 years), were analyzed. Lumbar lordosis and segmental angle at the index level were compared between preoperation and postoperative month 24. The von Mises stresses on the obliquely-cut spacer (5°, 10°, 15°, 20°, 25°, and 30°) were calculated under the compressive force of 400 N and 10 Nm of moment with validated FE model of the L4-5 spinal motion segment with segmental angle of 16°. Results Lumbar lordosis was not changed, while segmental angle was changed significantly from -8.1±7.2° to -5.9±6.7° (p<0.01) at postoperative month 24. The maximum von Mises stresses were markedly decreased with increased angle of the spacer up to 20°. The stress on the spacer was uneven with cylindrical spacer but it became even with the 15° oblique spacer. Conclusion The decreased segmental lordosis may be partially related to the pre-strain of Dynesys. Further clinical and biomechanical studies are required for relevant use of the system.
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Affiliation(s)
- Won Man Park
- Department of Mechanical Engineering, Kyung Hee University, Yongin, Korea
| | - Chi Heon Kim
- Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea. ; Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea. ; Neuroscience Research Institute, Seoul National University Medical Research Center, Seoul, Korea. ; Clinical Research Institute, Seoul National University Hospital, Seoul, Korea
| | - Yoon Hyuk Kim
- Department of Mechanical Engineering, Kyung Hee University, Yongin, Korea
| | - Chun Kee Chung
- Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea. ; Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea. ; Neuroscience Research Institute, Seoul National University Medical Research Center, Seoul, Korea. ; Clinical Research Institute, Seoul National University Hospital, Seoul, Korea. ; Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea
| | - Tae-Ahn Jahng
- Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea. ; Department of Neurosurgery, Seoul National University Bundang Hospital, Seongnam, Korea
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Gibson JNA, Depreitere B, Pflugmacher R, Schnake KJ, Fielding LC, Alamin TF, Goffin J. Decompression and paraspinous tension band: a novel treatment method for patients with lumbar spinal stenosis and degenerative spondylolisthesis. Spine J 2015; 15:S23-S32. [PMID: 25579423 DOI: 10.1016/j.spinee.2015.01.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 12/29/2014] [Accepted: 01/02/2015] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Prior studies have demonstrated the superiority of decompression and fusion over decompression alone for the treatment of lumbar degenerative spondylolisthesis with spinal stenosis. More recent studies have investigated whether nonfusion stabilization could provide durable clinical improvement after decompression and fusion. PURPOSE To examine the clinical safety and effectiveness of decompression and implantation of a novel flexion restricting paraspinous tension band (PTB) for patients with degenerative spondylolisthesis. STUDY DESIGN A prospective clinical study. PATIENT SAMPLE Forty-one patients (7 men and 34 women) aged 45 to 83 years (68.2 ± 9.0) were recruited with symptomatic spinal stenosis and Meyerding Grade 1 or 2 degenerative spondylolisthesis at L3-L4 (8) or L4-L5 (33). OUTCOME MEASURES Self-reported measures included visual analog scale (VAS) for leg, back, and hip pain and the Oswestry Disability Index (ODI). Physiologic measures included quantitative and qualitative radiographic analysis performed by an independent core laboratory. METHODS Patients with lumbar degenerative spondylolisthesis and stenosis were prospectively enrolled at four European spine centers with independent monitoring of data. Clinical and radiographic outcome data collected preoperatively were compared with data collected at 3, 6, 12, and 24 months after surgery. This study was sponsored by the PTB manufacturer (Simpirica Spine, Inc., San Carlos, CA, USA), including institutional research support grants to the participating centers totaling approximately US $172,000. RESULTS Statistically significant improvements and clinically important effect sizes were seen for all pain and disability measurements. At 24 months follow-up, ODI scores were reduced by an average of 25.4 points (59%) and maximum leg pain on VAS by 48.1 mm (65%). Back pain VAS scores improved from 54.1 by an average of 28.5 points (53%). There was one postoperative wound infection (2.4%) and an overall reoperation rate of 12%. Eighty-two percent patients available for 24 months follow-up with a PTB in situ had a reduction in ODI of greater than 15 points and 74% had a reduction in maximum leg pain VAS of greater than 20 mm. According to Odom criteria, most of these patients (82%) had an excellent or good outcome with all except one patient satisfied with surgery. As measured by the independent core laboratory, there was no significant increase in spondylolisthesis, segmental flexion-extension range of motion, or translation and no loss of lordosis in the patients with PTB at the 2 years follow-up. CONCLUSIONS Patients with degenerative spondylolisthesis and spinal stenosis treated with decompression and PTB demonstrated no progressive instability at 2 years follow-up. Excellent/good outcomes and significant improvements in patient-reported pain and disability scores were still observed at 2 years, with no evidence of implant failure or migration. Further study of this treatment method is warranted to validate these findings.
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Affiliation(s)
- J N Alastair Gibson
- Department of Orthopaedic Surgery, Spinal Unit, Royal Infirmary of Edinburgh, University of Edinburgh, Spire Murrayfield Hospital, The Edinburgh Clinic 122 Corstorphine Road, 40 Colinton Road, Edinburgh EH12 6UD EH10 5BT, Scotland
| | - Bart Depreitere
- Department of Neurosciences, Universitaire Ziekenhuizen KU Leuven, UZ Leuven campus, Gasthuisberg Dienst neurochirurgie Herestraat, 49 3000 Leuven, Belgium
| | - Robert Pflugmacher
- Klinik und Poliklinik für Orthopädie und Unfallchirurgie, Universitätsklinikum Bonn, Charite Universitatsmedizin Berlin, Augustenburger Platz 1, Berlin, Germany 13353
| | - Klaus J Schnake
- Zentrum für Wirbelsäulentherapie, Schön Klinik Nürnberg Fürth, Center for Spinal Surgery and Neurotraumatology, Friedberger Landstr. 430 60389, Frankfurt am Main, Germany
| | - Louis C Fielding
- Simpirica Spine, Inc.,1680 Bayport Ave., San Carlos, CA 94070, USA
| | - Todd F Alamin
- Department of Orthopaedic Surgery, Stanford University School of Medicine, 450 Broadway St, Pavillion A FL 1 MC6110, Redwood City, CA 94063, USA.
| | - Jan Goffin
- Department of Neurosciences, Universitaire Ziekenhuizen KU Leuven, UZ Leuven campus, Gasthuisberg Dienst neurochirurgie Herestraat, 49 3000 Leuven, Belgium
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Sparrey CJ, Bailey JF, Safaee M, Clark AJ, Lafage V, Schwab F, Smith JS, Ames CP. Etiology of lumbar lordosis and its pathophysiology: a review of the evolution of lumbar lordosis, and the mechanics and biology of lumbar degeneration. Neurosurg Focus 2015; 36:E1. [PMID: 24785474 DOI: 10.3171/2014.1.focus13551] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The goal of this review is to discuss the mechanisms of postural degeneration, particularly the loss of lumbar lordosis commonly observed in the elderly in the context of evolution, mechanical, and biological studies of the human spine and to synthesize recent research findings to clinical management of postural malalignment. Lumbar lordosis is unique to the human spine and is necessary to facilitate our upright posture. However, decreased lumbar lordosis and increased thoracic kyphosis are hallmarks of an aging human spinal column. The unique upright posture and lordotic lumbar curvature of the human spine suggest that an understanding of the evolution of the human spinal column, and the unique anatomical features that support lumbar lordosis may provide insight into spine health and degeneration. Considering evolution of the skeleton in isolation from other scientific studies provides a limited picture for clinicians. The evolution and development of human lumbar lordosis highlight the interdependence of pelvic structure and lumbar lordosis. Studies of fossils of human lineage demonstrate a convergence on the degree of lumbar lordosis and the number of lumbar vertebrae in modern Homo sapiens. Evolution and spine mechanics research show that lumbar lordosis is dictated by pelvic incidence, spinal musculature, vertebral wedging, and disc health. The evolution, mechanics, and biology research all point to the importance of spinal posture and flexibility in supporting optimal health. However, surgical management of postural deformity has focused on restoring posture at the expense of flexibility. It is possible that the need for complex and costly spinal fixation can be eliminated by developing tools for early identification of patients at risk for postural deformities through patient history (genetics, mechanics, and environmental exposure) and tracking postural changes over time.
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Affiliation(s)
- Carolyn J Sparrey
- Mechatronic Systems Engineering, Simon Fraser University, Surrey, British Columbia, Canada
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Erbulut DU, Kiapour A, Oktenoglu T, Ozer AF, Goel VK. A computational biomechanical investigation of posterior dynamic instrumentation: combination of dynamic rod and hinged (dynamic) screw. J Biomech Eng 2015; 136:051007. [PMID: 24599026 DOI: 10.1115/1.4027060] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 03/06/2014] [Indexed: 11/08/2022]
Abstract
Currently, rigid fixation systems are the gold standard for degenerative disk disease treatment. Dynamic fixation systems have been proposed as alternatives for the treatment of a variety of spinal disorders. These systems address the main drawbacks of traditional rigid fixation systems, such as adjacent segment degeneration and instrumentation failure. Pedicle-screw-based dynamic stabilization (PDS) is one type of these alternative systems. The aim of this study was to simulate the biomechanical effect of a novel posterior dynamic stabilization system, which is comprised of dynamic (hinged) screws interconnected with a coiled, spring-based dynamic rod (DSDR), and compare it to semirigid (DSRR and RSRR) and rigid stabilization (RSRR) systems. A validated finite element (FE) model of L1-S1 was used to quantify the biomechanical parameters of the spine, such as range of motion, intradiskal pressure, stresses and facet loads after single-level instrumentation with different posterior stabilization systems. The results obtained from in vitro experimental intact and instrumented spines were used to validate the FE model, and the validated model was then used to compare the biomechanical effects of different fixation and stabilization constructs with intact under a hybrid loading protocol. The segmental motion at L4-L5 increased by 9.5% and 16.3% in flexion and left rotation, respectively, in DSDR with respect to the intact spine, whereas it was reduced by 6.4% and 10.9% in extension and left-bending loads, respectively. After instrumentation-induced intradiskal pressure at adjacent segments, L3-L4 and L5-S1 became less than the intact in dynamic rod constructs (DSDR and RSDR) except in the RSDR model in extension where the motion was higher than intact by 9.7% at L3-L4 and 11.3% at L5-S1. The facet loads were insignificant, not exceeding 12N in any of the instrumented cases in flexion. In extension, the facet load in DSDR case was similar to that in intact spine. The dynamic rod constructions (DSDR and RSDR) led to a lesser peak stress at screws compared with rigid rod constructions (DSRR and RSRR) in all loading cases. A dynamic construct consisting of a dynamic rod and a dynamic screw did protect the adjacent level from excessive motion.
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In vivo compatibility of Dynesys® spinal implants: a case series of five retrieved periprosthetic tissue samples and corresponding implants. 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 2014; 24:1074-84. [DOI: 10.1007/s00586-014-3705-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 11/24/2014] [Accepted: 11/26/2014] [Indexed: 12/28/2022]
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The use of polyurethane materials in the surgery of the spine: a review. Spine J 2014; 14:3038-47. [PMID: 25151132 DOI: 10.1016/j.spinee.2014.08.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 02/26/2014] [Accepted: 08/13/2014] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT The spine contains intervertebral discs and the interspinous and longitudinal ligaments. These structures are elastomeric or viscoelastic in their mechanical properties and serve to allow and control the movement of the bony elements of the spine. The use of metallic or hard polymeric devices to replace the intervertebral discs and the creation of fusion masses to replace discs and/or vertebral bodies changes the load transfer characteristics of the spine and the range of motion of segments of the spine. PURPOSE The purpose of the study was to survey the literature, regulatory information available on the Web, and industry-reported device development found on the Web to ascertain the usage and outcomes of the use of polyurethane polymers in the design and clinical use of devices for spine surgery. STUDY DESIGN/SETTING A systematic review of the available information from all sources concerning the subject materials' usage in spinal devices was conducted. METHODS A search of the peer-reviewed literature combining spinal surgery with polyurethane or specific types and trade names of medical polyurethanes was performed. Additionally, information available on the Food and Drug Administration Web site and for corporate Web sites was reviewed in an attempt to identify pertinent information. RESULTS The review captured devices that are in testing or have entered clinical practice that use elastomeric polyurethane polymers as disc replacements, dynamic stabilization of spinal movement, or motion limitation to relieve nerve root compression and pain and as complete a listing as possible of such devices that have been designed or tested but appear to no longer be pursued. This review summarizes the available information about the uses to which polyurethanes have been tested or are being used in spinal surgery. CONCLUSIONS The use of polyurethanes in medicine has expanded as modifications to the stability of the polymers in the physiological environment have been improved. The potential for the use of elastomeric materials to more closely match the mechanical properties of the structures being replaced and to maintain motion between spinal segments appears to hold promise. The published results from the use of the devices that are discussed show early success with these applications of elastomeric materials.
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Abstract
STUDY DESIGN The biomechanical effects of Dynesys and Cosmic fixators on transition and adjacent segments were evaluated using the finite-element method. OBJECTIVE This study investigated the load-transferring mechanisms of 2 dynamic fixators and the fixator-induced effects on the junctional problem of the adjacent segments. SUMMARY OF BACKGROUND DATA The mobility and flexibility of Dynesys screw-spacer and Cosmic screw-hinge joints preserve motion and share loads for the transition segment. However, the differences in tissue responses and fixator mechanisms among these 2 fixators have not been investigated extensively. METHODS A lumbosacral model from L1 to S1 levels was developed and subjected to muscular contraction, ligamentous interconnection, compressive force, and trunk moment. A static fixator was instrumented at the moderately degenerative L4-L5 segment to serve as a comparison baseline. Subsequently, the 2 fixators were instrumented at the mildly degenerative L3-L4 segment. The tissue responses of the adjacent segments and the load transmission at the screw-spacer and bone-screw interfaces were compared. RESULTS Both systems show the ability to protect the transition segment but deteriorate the adjacent segments. The screw-hinge joint and the stiffer rod of the Cosmic system significantly constrained the motion pattern of the transition segment. Comparatively, the Dynesys screw-spacer interfaces make contact with and depart from each other during motion; thus providing higher mobility to the transition segment. However, the highly stressed distribution at the Cosmic bone-screw causes the screw and hinge prone to pullout and fatigue failures. CONCLUSION Cosmic fixation can better protect the disc and facet joint of the transition segment than can the Dynesys. However, the screw-hinge joint strictly constrains intersegmental motion and deteriorates the junctional problem. The Cosmic system can be chosen to treat more severely degenerative transition segments. With higher flexibility, the Dynesys system is recommended for the transition segment that is healthy or mildly degenerative. LEVEL OF EVIDENCE N/A.
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Chamoli U, Diwan AD, Tsafnat N. Pedicle screw-based posterior dynamic stabilizers for degenerative spine:In vitrobiomechanical testing and clinical outcomes. J Biomed Mater Res A 2013; 102:3324-40. [DOI: 10.1002/jbm.a.34986] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 09/25/2013] [Accepted: 09/30/2013] [Indexed: 01/28/2023]
Affiliation(s)
- Uphar Chamoli
- Spine Service, Department of Orthopaedic Surgery, St. George Hospital Clinical School; University of New South Wales; Kogarah Sydney NSW 2217 Australia
- School of Mechanical and Manufacturing Engineering; University of New South Wales; Kensington Campus Sydney NSW 2052 Australia
| | - Ashish D. Diwan
- Spine Service, Department of Orthopaedic Surgery, St. George Hospital Clinical School; University of New South Wales; Kogarah Sydney NSW 2217 Australia
| | - Naomi Tsafnat
- School of Mechanical and Manufacturing Engineering; University of New South Wales; Kensington Campus Sydney NSW 2052 Australia
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Kurtz SM, Lanman TH, Higgs G, Macdonald DW, Berven SH, Isaza JE, Phillips E, Steinbeck MJ. Retrieval analysis of PEEK rods for posterior fusion and motion preservation. 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 2013; 22:2752-9. [PMID: 23887771 DOI: 10.1007/s00586-013-2920-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 06/25/2013] [Accepted: 07/14/2013] [Indexed: 01/30/2023]
Abstract
INTRODUCTION The purpose of this study was to analyze explanted PEEK rod spinal systems in the context of their clinical indications. We evaluated damage to the implant and histological changes in explanted periprosthetic tissues. METHODS 12 patients implanted with 23 PEEK rods were revised between 2008 and 2012. PEEK rods were of the same design (CD Horizon Legacy, Medtronic, Memphis TN, USA). Retrieved components were assessed for surface damage mechanisms, including plastic deformation, scratching, burnishing, and fracture. Patient history and indications for PEEK rod implantation were obtained from analysis of the medical records. RESULTS 11/12 PEEK rod systems were employed for fusion at one level, and motion preservation at the adjacent level. Surgical complications in the PEEK cohort included a small dural tear in one case that was immediately repaired. There were no cases of PEEK rod fracture or pedicle screw fracture. Retrieved PEEK rods exhibited scratching, as well as impressions from the set screws and pedicle screw saddles. PEEK debris was observed in two patient tissues, which were located adjacent to PEEK rods with evidence of scratching and burnishing. CONCLUSION This study documents the surface changes and tissue reactions for retrieved PEEK rod stabilization systems. Permanent indentations by the set screws and pedicle screws were the most prevalent observations on the surface of explanted PEEK rods.
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Affiliation(s)
- Steven M Kurtz
- Drexel University, 3401 Market St, Suite 345, Philadelphia, PA, 19104, USA,
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Landi A. Elastic resistance of the spine: Why does motion preservation surgery almost fail? World J Clin Cases 2013; 1:134-139. [PMID: 24303484 PMCID: PMC3845953 DOI: 10.12998/wjcc.v1.i4.134] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 04/11/2013] [Accepted: 06/10/2013] [Indexed: 02/05/2023] Open
Abstract
Single metamere motility should not be interpreted merely as a movement on the 3 planes but also, and above all, as elastic resistance to dynamic stress on these 3 planes. In the light of this consideration, the aim of motion preservation is to neutralize excessive movements while preserving the physiological biomechanical properties of the metamere involved to interrupt the progression of degenerative processes and to prevent adjacent segment disease. Despite the fact that a myriad of devices have been developed with the purpose of achieving dynamic neutralization of the spine, there are now some doubts regarding the true efficacy of these devices.
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Cipriani E, Bracco P, Kurtz SM, Costa L, Zanetti M. In-vivo degradation of poly(carbonate-urethane) based spine implants. Polym Degrad Stab 2013; 98:1225-1235. [PMID: 24043907 DOI: 10.1016/j.polymdegradstab.2013.03.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Fourteen explanted Dynesys® spinal devices were analyzed for biostability and compared with a reference, never implanted, control. Both poly(carbonate-urethane) (PCU) spacers and polyethylene-terephthalate (PET) cords were analyzed. The effect of implantation was evaluated through the observation of physical alterations of the device surfaces, evaluation of the chemical degradation and fluids absorption on the devices and examination of the morphological and mechanical features. PCU spacers exhibited a variety of surface damage mechanisms, the most significant being abrasion and localized, microscopic surface cracks. Evidence of oxidation and chain scission were detected on PCU spacers ATR-FTIR. ATR-FTIR, DSC and hardness measurements also showed a slight heterogeneity in the composition of PCU. The extraction carried out on the PCU spacers revealed the presence of extractable polycarbonate segments. One spacer and all PET cords visually exhibited the presence of adherent biological material (proteins), confirmed by the ATR-FTIR results. GC/MS analyses of the extracts from PET cords revealed the presence of biological fluids residues, mainly cholesterol derivatives and fatty acids, probably trapped into the fiber network. No further chemical alterations were observed on the PET cords. Although the observed physical and chemical damage can be considered superficial, greater attention must be paid to the chemical degradation mechanisms of PCU and to the effect of byproducts on the body.
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Affiliation(s)
- E Cipriani
- Dipartimento di Chimica and NIS Centre of Excellence, University of Torino, Via Pietro Giuria 7, 10125 Torino, Italy
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Pretension effects of the Dynesys cord on the tissue responses and screw-spacer behaviors of the lumbosacral construct with hybrid fixation. Spine (Phila Pa 1976) 2013; 38:E775-82. [PMID: 23486410 DOI: 10.1097/brs.0b013e318290fb2e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN The pretension of the Dynesys cord was varied to evaluate its effects on both tissue responses and screw-spacer behaviors by the finite-element method. OBJECTIVE This study aimed to provide detailed information about the motion-preserving and load-shielding mechanisms of the Dynesys screw-spacer joint. SUMMARY OF BACKGROUND DATA Intuitively, higher cord pretension aims to ensure the occurrence of screw-spacer contact, thus making the spacer the transmitter of the vertebral loads. However, detailed investigations of the cord-pretension effects have not yet been carried out. METHODS.: Using a validated lumbosacral model, the moderately degenerative L4-L5 segment was instrumented by a static fixator and the Dynesys fixator was further used to bridge a mildly degenerative L3-L4 segment. The pre-tended cord was modeled as an elastic spring with 0- and 300-N pretensions. The disc range-of-motion, disc stress, facet force, bone-screw stress, and screw-spacer force were chosen as comparison indices. RESULTS.: At the transition and adjacent segments, the range-of-motion differences between the 2 pretensions were 7.7% and 2.0% on average, respectively. The mechanical differences at the transition and adjacent segments were 9.0% and 5.2% (disc stress) and 9.4% and 9.1% (facet force), respectively. The results indicated that the cord pretension has a minor effect on the adjacent segments in comparison with the transition segment. However, the stress at the screw hub and force of the screw-spacer contact of the 300-N pretension were increased by 33.7% and 316.5% on average than without pretension, respectively. CONCLUSION The moment arm from the screw-cord center to the fulcrum is significantly less than that of vertebral loads. This leads to the minor effect of increasing the cord pretension on the responses of the adjacent segments. However, the cord pretension can significantly affect both screw-spacer force and bone-screw stress. LEVEL OF EVIDENCE 4.
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Sequestrectomy with additional transpedicular dynamic stabilization for the treatment of lumbar disc herniation: no clinical benefit after 10 years follow-up. Spine (Phila Pa 1976) 2013; 38:887-95. [PMID: 23232214 DOI: 10.1097/brs.0b013e31828150a6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Single-center prospective study. OBJECTIVE Clinical and radiological long-term evaluation of the effects of transpedicular dynamic stabilization after sequestrectomy. SUMMARY OF BACKGROUND DATA Short- and mid-term investigations have shown that additional dynamic stabilization is appropriate to prevent progression of initial segment degeneration after sequestrectomy and associated with superior clinical outcome compared with sequestrectomy alone. Long-term data are missing. METHODS Eighty-four patients with symptomatic disc herniation and initial osteochondrosis (Modic = I°) of the lumbar spine underwent sequestrectomy. Additional dynamic stabilization was performed in 35 subjects (group D); the remaining 49 subjects were treated with sequestrectomy alone (group S). Clinical (Oswestry Low Back Pain Disability Questionnaire, Version 2.0; visual analogue scale) and radiological (plain and extension-flexion radiographs and magnetic resonance images) parameters were collected preoperatively, at 3 months postoperatively, as well as at a mean follow-up of 2.8 and 10.2 years. RESULTS Twenty-nine of 35 (83%, group D) and 38 of 49 (78%, group S) patients were available at the final follow-up. Reoperation rate in group D was 34% (10/29) due to implant failures or progression of degeneration at the index or the adjacent segments. In group S, 5 of 38 (13%) underwent further operation because of a reprolapse or progression of degeneration of the index level. In the remaining patients, clinical scores (Oswestry Low Back Pain Disability Questionnaire, Version 2.0; and visual analogue scale) improved significantly, with similar results in both groups at the final follow-up. The rate of progression of disc degeneration was lower when the patients were also dynamically stabilized than sequestrectomy alone, but the rate of adjacent segment degeneration superior to the operated segment was significantly higher in group D. CONCLUSION Additional dynamic stabilization does not lead to a clinical benefit in patients with symptomatic disc herniation and initial segment degeneration compared with sequestrectomy alone after a long-term follow-up. Because of this and the high rate of necessary reoperations, we do not recommend this surgical strategy for this indication. LEVEL OF EVIDENCE 4.
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Histomorphometric and radiographical changes after lumbar implantation of the PEEK nonfusion interspinous device in the BB.4S rat model. Spine (Phila Pa 1976) 2013; 38:E263-9. [PMID: 23222648 DOI: 10.1097/brs.0b013e318280c710] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
STUDY DESIGN An experimental animal study. OBJECTIVE To investigate histomorphometric and radiographical changes in the BB.4S rat model after PEEK (polyetheretherketone) nonfusion interspinous device implantation. SUMMARY OF BACKGROUND DATA Clinical effectiveness of the PEEK nonfusion spine implant Wallis (Abbott, Bordeaux, France; now Zimmer, Warsaw, IN) is well documented. However, there is a lack of evidence on the long-term effects of this implant on bone, in particular its influence on structural changes of bone elements of the lumbar spine. METHODS Twenty-four male BB.4S rats aged 11 weeks underwent surgery for implantation of a PEEK nonfusion interspinous device or for a sham procedure in 3 groups of 8 animals each: (1) implantation at level L4-L5; (2) implantation at level L5-L6; and (3) sham surgery. Eleven weeks postoperatively osteolyses at the implant-bone interface were measured via radiograph, bone mineral density of vertebral bodies was analyzed using osteodensitometry, and bone mineral content as well as resorption of the spinous processes were examined by histomorphometry. RESULTS.: Resorption of the spinous processes at the site of the interspinous implant was found in all treated segments. There was no significant difference in either bone density of vertebral bodies or histomorphometric structure of the spinous processes between adjacent vertebral bodies, between treated and untreated segments and between groups. CONCLUSION These findings indicate that resorption of spinous processes because of a result of implant loosening, inhibit the targeted load redistribution through the PEEK nonfusion interspinous device in the lumbar spinal segment of the rat. This leads to reduced long-term stability of the implant in the animal model. These results suggest that PEEK nonfusion interspinous devices like the Wallis implants may have time-limited effects and should only be used for specified indications.
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Schmoelz W, Erhart S, Unger S, Disch AC. Biomechanical evaluation of a posterior non-fusion instrumentation of the lumbar spine. 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 2011; 21:939-45. [PMID: 22205112 DOI: 10.1007/s00586-011-2121-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 11/07/2011] [Accepted: 12/06/2011] [Indexed: 11/24/2022]
Abstract
PURPOSE Numerous posterior non-fusion systems have been developed within the past decade to resolve the disadvantages of rigid instrumentations and preserve spinal motion. The aim of this study was to investigate the effect of a new dynamic stabilization device, to measure the screw anchorage after flexibility testing and compare it with data reported in the literature. METHODS Six human lumbar spine motion segments (L2-5) were loaded in a spine tester with pure moments of 7.5 Nm in lateral bending, flexion/extension and axial rotation. Specimens were tested intact, after instrumentation of the intact segment, after destabilization by a nucleotomy and after instrumentation of the destabilised segment with the new non-fusion device (Elaspine). After flexibility testing all screws were subjected to a pull-out test. RESULTS Instrumentation of the intact segment significantly reduced the RoM (p < 0.002) in flexion, extension and lateral bending to 49.7, 44.6 and 53% of the intact state, respectively. In axial rotation, the instrumentation resulted in a non-significant RoM reduction to 95% of the intact state. Compared to the intact segment, instrumentation of the destabilized segment significantly (p < 0.05) reduced the RoM to 69.8, 62.3 and 79.1% in flexion, extension and lateral bending, respectively. In axial rotation, the instrumented segment showed a significantly higher RoM than the intact segment (137.6% of the intact state (p < 0.01)). The pull-out test showed a maximum pull-out force of 855.1 N (±334) with a displacement of 6.1 mm (±2.8) at maximum pull-out force. CONCLUSIONS The effect of the investigated motion preservation device on the RoM of treated segments is in the range of other devices reported in the literature. Compared to the most implanted and investigated device, the Dynesys, the Elaspine has a less pronounced motion restricting effect in lateral bending and flexion/extension, while being less effective in limiting axial rotation. The pull-out force of the pedicle screws demonstrated anchorage comparable to other screw designs reported in the literature.
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Affiliation(s)
- Werner Schmoelz
- Department of Trauma Surgery, Medical University Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria.
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In vivo preclinical evaluation of the influence of osteoporosis on the anchorage of different pedicle screw designs. 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 2011; 20:1289-96. [PMID: 21544593 DOI: 10.1007/s00586-011-1831-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 03/09/2011] [Accepted: 04/20/2011] [Indexed: 10/18/2022]
Abstract
We investigate the anchorage of pedicle screws with different surface treatments in osteoporotic bone. Eight ewes were divided into two groups of four animals each: four sheep underwent bilateral ovariectomy (OVX Group), whereas the operation was simulated in the remaining group (SHAM Group). Eighteen months after the first operation, the Dynesys(®) System was fitted to the sheep using pedicle screws with three different surface treatments: untreated, rough blasted (uncoated) and bioactive coated (bioactive). Uncoated screws showed a significantly higher bone ingrowth value compared with the untreated screws in the OVX group (9.3%, p < 0.005) and a significantly lower bone ingrowth value in the SHAM group (-11.0%, p < 0.05). Furthermore, the bioactive pedicle screws had a significant lower bone ingrowth value than the untreated screws in the SHAM group (-12.1%, p < 0.05). These results suggest that both tested surface treatments of pedicular screws may provide an advantage in terms of bone quality and osseointegration, when implanted in osteoporotic vertebrae.
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26
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Shen M, Zhang K, Koettig P, Welch WC, Dawson JM. In vivo biostability of polymeric spine implants: retrieval analyses from a United States investigational device exemption study. 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 2011; 20:1837-49. [PMID: 21538208 DOI: 10.1007/s00586-011-1812-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 03/25/2011] [Accepted: 04/12/2011] [Indexed: 11/27/2022]
Abstract
The Dynesys System for stabilizing the lumbar spine was first surgically implanted in Europe in 1994. In 2003, a prospective, randomized, investigational device exemption clinical trial of the system for non-fusion dynamic stabilization began. Polycarbonate urethane (PCU) and polyethylene terephthalate (PET) components explanted from four patients who had participated in the study were analyzed for biostability. Components had been implanted 9-19 months. The explanted components were visually inspected and digitally photographed. Scanning electron microscopy was used to analyze the surface of the spacers. The chemical and molecular properties of the retrieved spacers and cords were quantitatively compared with lot-matched, shelf-aged, components that had not been implanted using attenuated total reflection Fourier transform infrared (FTIR) and gel permeation chromatography (GPC). FTIR analyses suggested that the explanted spacers exhibited slight surface chemical changes but were chemically unchanged below the surface and in the center. New peaks that could be attributed to biodegradation of PCU were not observed. The spectral analyses for the cords revealed that the PET cords were chemically unchanged at both the surface and the interior. Peaks associated with the PET biodegradation were not detected. GPC results did not identify changes to the distributions of molecular weights that might be attributed to biodegradation of either PCU spacers or PET cords. The explanted condition of the retrieved components demonstrated the biostability of both PCU spacers and PET cords that had been in vivo for up to 19 months.
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Affiliation(s)
- Ming Shen
- Zimmer Inc, 1800 West Center St, Warsaw, IN 4658, USA.
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Kurtz SM, Steinbeck M, Ianuzzi A, van Ooij A, Punt IM, Isaza J, Ross ERS. Retrieval analysis of motion preserving spinal devices and periprosthetic tissues. SAS JOURNAL 2009; 3:161-77. [PMID: 25802641 PMCID: PMC4365601 DOI: 10.1016/j.esas.2009.11.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
This article reviews certain practical aspects of retrieval analysis for motion preserving spinal implants and periprosthetic tissues as an essential component of the overall revision strategy for these implants. At our institution, we established an international repository for motion-preserving spine implants in 2004. Our repository is currently open to all spine surgeons, and is intended to be inclusive of all cervical and lumbar implant designs such as artificial discs and posterior dynamic stabilization devices. Although a wide range of alternative materials is being investigated for nonfusion spine implants, many of the examples in this review are drawn from our existing repository of metal-on-polyethylene, metal-on-metal lumbar total disc replacements (TDRs), and polyurethane-based dynamic motion preservation devices. These devices are already approved or nearing approval for use in the United States, and hence are the most clinically relevant at the present time. This article summarizes the current literature on the retrieval analysis of these implants and concludes with recommendations for the development of new test methods that are based on the current state of knowledge of in vivo wear and damage mechanisms. Furthermore, the relevance and need to evaluate the surrounding tissue to obtain a complete understanding of the biological reaction to implant component corrosion and wear is reviewed.
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Affiliation(s)
- Steven M Kurtz
- Implant Research Center, School of Biomedical Engineering, Science, and Health Systems and Department of Materials Engineering, Drexel University, Philadelphia, PA ; Exponent, Inc., 3401 Market St., Suite 300, Philadelphia, PA
| | - Marla Steinbeck
- Implant Research Center, School of Biomedical Engineering, Science, and Health Systems and Department of Materials Engineering, Drexel University, Philadelphia, PA
| | - Allyson Ianuzzi
- Implant Research Center, School of Biomedical Engineering, Science, and Health Systems and Department of Materials Engineering, Drexel University, Philadelphia, PA ; Exponent, Inc., 3401 Market St., Suite 300, Philadelphia, PA
| | - André van Ooij
- Departments of Orthopaedic Surgery, Maastricht University Medical Center, AZ Maastricht, 6202 AZ Maastricht, the Netherlands
| | - Ilona M Punt
- Departments of Orthopaedic Surgery, Maastricht University Medical Center, AZ Maastricht, 6202 AZ Maastricht, the Netherlands
| | - Jorge Isaza
- Our Lady of the Lake Medical Center, Baton Rouge, LA
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