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Xu ML, Yang YT, Zeng HZ, Cao YT, Zheng LD, Jin C, Zhu SJ, Zhu R. Finite element modeling and analysis of effect of preexisting cervical degenerative disease on the spinal cord during flexion and extension. Med Biol Eng Comput 2024; 62:1089-1104. [PMID: 38148413 DOI: 10.1007/s11517-023-02993-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Accepted: 12/07/2023] [Indexed: 12/28/2023]
Abstract
Recent studies have emphasized the importance of dynamic activity in the development of myelopathy. However, current knowledge of how degenerative factors affect the spinal cord during motion is still limited. This study aimed to investigate the effect of various types of preexisting herniated cervical disc and the ligamentum flavum ossification on the spinal cord during cervical flexion and extension. A detailed dynamic fluid-structure interaction finite element model of the cervical spine with the spinal cord was developed and validated. The changes of von Mises stress and maximum principal strain within the spinal cord in the period of normal, hyperflexion, and hyperextension were investigated, considering various types and grades of disc herniation and ossification of the ligamentum flavum. The flexion and extension of the cervical spine with spinal canal encroachment induced high stress and strain inside the spinal cord, and this effect was also amplified by increased canal encroachments and cervical hypermobility. The spinal cord might evade lateral encroachment, leading to a reduction in the maximum stress and principal strain within the spinal cord in local-type herniation. Although the impact was limited in the case of diffuse type, the maximum stress tended to appear in the white matter near the encroachment site while compression from both ventral and dorsal was essential to make maximum stress appear in the grey matter. The existence of canal encroachment can reduce the safe range for spinal cord activities, and hypermobility activities may induce spinal cord injury. Besides, the ligamentum flavum plays an important role in the development of central canal syndrome.Significance. This model will enable researchers to have a better understanding of the influence of cervical degenerative diseases on the spinal cord during extension and flexion.
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Affiliation(s)
- Meng-Lei Xu
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai, 200092, China
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai, 200065, China
| | - Yi-Ting Yang
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai, 200092, China
| | - Hui-Zi Zeng
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai, 200092, China
| | - Yu-Ting Cao
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai, 200092, China
| | - Liang-Dong Zheng
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai, 200092, China
| | - Chen Jin
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai, 200092, China
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai, 200065, China
| | - Shi-Jie Zhu
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai, 200092, China
| | - Rui Zhu
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai, 200092, China.
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai, 200065, China.
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Davies B, Schaefer S, Rafati Fard A, Newcombe V, Sutcliffe M. Finite Element Analysis for Degenerative Cervical Myelopathy: Scoping Review of the Current Findings and Design Approaches, Including Recommendations on the Choice of Material Properties. JMIR BIOMEDICAL ENGINEERING 2024; 9:e48146. [PMID: 38875683 PMCID: PMC11041437 DOI: 10.2196/48146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 10/31/2023] [Accepted: 02/15/2024] [Indexed: 06/16/2024] Open
Abstract
BACKGROUND Degenerative cervical myelopathy (DCM) is a slow-motion spinal cord injury caused via chronic mechanical loading by spinal degenerative changes. A range of different degenerative changes can occur. Finite element analysis (FEA) can predict the distribution of mechanical stress and strain on the spinal cord to help understand the implications of any mechanical loading. One of the critical assumptions for FEA is the behavior of each anatomical element under loading (ie, its material properties). OBJECTIVE This scoping review aims to undertake a structured process to select the most appropriate material properties for use in DCM FEA. In doing so, it also provides an overview of existing modeling approaches in spinal cord disease and clinical insights into DCM. METHODS We conducted a scoping review using qualitative synthesis. Observational studies that discussed the use of FEA models involving the spinal cord in either health or disease (including DCM) were eligible for inclusion in the review. We followed the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) guidelines. The MEDLINE and Embase databases were searched to September 1, 2021. This was supplemented with citation searching to retrieve the literature used to define material properties. Duplicate title and abstract screening and data extraction were performed. The quality of evidence was appraised using the quality assessment tool we developed, adapted from the Newcastle-Ottawa Scale, and shortlisted with respect to DCM material properties, with a final recommendation provided. A qualitative synthesis of the literature is presented according to the Synthesis Without Meta-Analysis reporting guidelines. RESULTS A total of 60 papers were included: 41 (68%) "FEA articles" and 19 (32%) "source articles." Most FEA articles (33/41, 80%) modeled the gray matter and white matter separately, with models typically based on tabulated data or, less frequently, a hyperelastic Ogden variant or linear elastic function. Of the 19 source articles, 14 (74%) were identified as describing the material properties of the spinal cord, of which 3 (21%) were considered most relevant to DCM. Of the 41 FEA articles, 15 (37%) focused on DCM, of which 9 (60%) focused on ossification of the posterior longitudinal ligament. Our aggregated results of DCM FEA indicate that spinal cord loading is influenced by the pattern of degenerative changes, with decompression alone (eg, laminectomy) sufficient to address this as opposed to decompression combined with other procedures (eg, laminectomy and fusion). CONCLUSIONS FEA is a promising technique for exploring the pathobiology of DCM and informing clinical care. This review describes a structured approach to help future investigators deploy FEA for DCM. However, there are limitations to these recommendations and wider uncertainties. It is likely that these will need to be overcome to support the clinical translation of FEA to DCM.
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Affiliation(s)
- Benjamin Davies
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Samuel Schaefer
- Department of Engineering, University of Cambridge, Cambridge, United Kingdom
| | - Amir Rafati Fard
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Virginia Newcombe
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Michael Sutcliffe
- Department of Engineering, University of Cambridge, Cambridge, United Kingdom
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Zheng LD, Cao YT, Yang YT, Xu ML, Zeng HZ, Zhu SJ, Jin C, Yuan Q, Zhu R. Effect of Different Types of Ossification of the Posterior Longitudinal Ligament on the Dynamic Biomechanical Response of the Spinal Cord: A Finite Element Analysis. J Biomech Eng 2023; 145:121002. [PMID: 37578172 DOI: 10.1115/1.4063194] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Accepted: 08/09/2023] [Indexed: 08/15/2023]
Abstract
Ossification of the posterior longitudinal ligament (OPLL) has been identified as an important cause of cervical myelopathy. However, the biomechanical mechanism between the OPLL type and the clinical characteristics of myelopathy remains unclear. The aim of this study was to evaluate the effect of different types of OPLL on the dynamic biomechanical response of the spinal cord. A three-dimensional finite element model of the fluid-structure interaction of the cervical spine with spinal cord was established and validated. The spinal cord stress and strain, cervical range of motion (ROM) in different types of OPLL models were predicted during dynamic flexion and extension activity. Different types of OPLL models showed varying degrees of increase in stress and strain under the process of flexion and extension, and there was a surge toward the end of extension. Larger spinal cord stress was observed in segmental OPLL. For continuous and mixed types of OPLL, the adjacent segments of OPLL showed a dramatic increase in ROM, while the ROM of affected segments was limited. As a dynamic factor, flexion and extension of the cervical spine play an amplifying role in OPLL-related myelopathy, while appropriate spine motion is safe and permitted. Segmental OPLL patients are more concerned about the spinal cord injury induced by large stress, and patients with continuous OPLL should be noted to progressive injuries of adjacent level.
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Affiliation(s)
- Liang-Dong Zheng
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China;Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Yu-Ting Cao
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China;Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Yi-Ting Yang
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China;Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Meng-Lei Xu
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China;Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Hui-Zi Zeng
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China;Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Shi-Jie Zhu
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China;Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Chen Jin
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China;Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Qing Yuan
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China;Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Rui Zhu
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China;Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
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Yang YT, Zhu SJ, Xu ML, Zheng LD, Cao YT, Yuan Q, Zhang K, Zhu R. The biomechanical effect of different types of ossification of the ligamentum flavum on the spinal cord during cervical dynamic activities. Med Eng Phys 2023; 121:104062. [PMID: 37985028 DOI: 10.1016/j.medengphy.2023.104062] [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: 12/01/2022] [Revised: 08/15/2023] [Accepted: 10/11/2023] [Indexed: 11/22/2023]
Abstract
Ossification of the ligamentum flavum (OLF) is thought to be an influential etiology of myelopathy, as thickened ligamentum flavum causes the stenosis of the vertebral canal, which could subsequently compress the spinal cord. Unfortunately, there was little information available on the effects of cervical OLF on spinal cord compression, such as the relationship between the progression of cervical OLF and nervous system symptoms during dynamic cervical spine activities. In this research, a finite element model of C1-C7 including the spinal cord featured by dynamic fluid-structure interaction was reconstructed and utilized to analyze how different types of cervical OLF affect principal strain and stress distribution in spinal cord during spinal activities towards six directions. For patients with cervical OLF, cervical extension induces higher stress within the spinal cord among all directions. From the perspective of biomechanics, extension leads to stress concentration in the lateral corticospinal tracts or the posterior of gray matter. Low energy damage to the spinal cord would be caused by the high and fluctuating stresses during cervical movements to the affected side for patients with unilateral OLF at lower grades.
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Affiliation(s)
- Yi-Ting Yang
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Shi-Jie Zhu
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Meng-Lei Xu
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Liang-Dong Zheng
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Yu-Ting Cao
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Qing Yuan
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China
| | - Kai Zhang
- Department of Orthopedics, Shanghai Liqun Hospital, Taopu road 910, Shanghai 200333, China.
| | - Rui Zhu
- Shanghai YangZhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), School of Medicine, Tongji University, Shanghai 200092, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of the Ministry of Education, Tongji Hospital, School of Medicine, Tongji University, 389 Xincun Road, Shanghai 200065, China.
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Wang S, Sun J, Han D, Fan J, Yu Mm Y, Yang Mm H, Gao C, Zhou X, Guo Y, Shi J. Magnetic Resonance Imaging-CCCFLS Scoring System: Toward Predicting Clinical Symptoms and C5 Paralysis. Global Spine J 2023:21925682231170607. [PMID: 37203443 DOI: 10.1177/21925682231170607] [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] [Indexed: 05/20/2023] Open
Abstract
STUDY DESIGN A retrospective study. OBJECTIVE To develop a new MRI scoring system to assess patients' clinical characteristics, outcomes and complications. METHODS A retrospective 1-year follow-up study of 366 patients with cervical spondylosis from 2017 to 2021. The CCCFLS scores (cervical curvature and balance (CC), spinal cord curvature (SC), spinal cord compression ratio (CR), cerebrospinal fluid space (CFS). Spinal cord and lesion location (SL). Increased Signal Intensity (ISI) were divided into Mild group (0-6), Moderate group (6-12), and Severe group (12-18) for comparison, and the Japanese Orthopaedic Association (JOA) scores, visual analog scale (VAS), numerical rating scale (NRS), Neck Disability Index (NDI) and Nurick scores were evaluated. Correlation and regression analyses were performed between each variable and the total model in relation to clinical symptoms and C5 palsy. RESULTS The CCCFLS scoring system was linearly correlated with JOA, NRS, Nurick and NDI scores, with significant differences in JOA scores among patients with different CC, CR, CFS, ISI scores, with a predictive model (R2 = 69.3%), and significant differences in preoperative and final follow-up clinical scores among the 3 groups, with a higher rate of improvement in JOA in the severe group (P < .05), while patients with and without C5 paralysis had significant differences in preoperative SC and SL (P < .05). CONCLUSIONS CCCFLS scoring system can be divided into mild (0-6). moderate (6-12), severe (12-18) groups. It can effectively reflect the severity of clinical symptoms, and the improvement rate of JOA is better in the severe group, while the preoperative SC and SL scores are closely related to C5 palsy. LEVEL OF EVIDENCE III.
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Affiliation(s)
- Shunmin Wang
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
- 910 Hospital, Quanzhou, China
| | - Jingchuan Sun
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Dan Han
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Jianping Fan
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Yaping Yu Mm
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Haiqin Yang Mm
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Chunyan Gao
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - XiaoNan Zhou
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Yongfei Guo
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Jiangang Shi
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
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Effect of degenerative factors on cervical spinal cord during flexion and extension: a dynamic finite element analysis. Biomech Model Mechanobiol 2022; 21:1743-1759. [PMID: 35931861 DOI: 10.1007/s10237-022-01617-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 07/13/2022] [Indexed: 11/02/2022]
Abstract
Spinal cord injury (SCI) is a global problem that brings a heavy burden to both patients and society. Recent investigations indicated degenerative disease is taking an increasing part in SCI with the growth of the aging population. However, little insight has been gained about the effect of cervical degenerative disease on the spinal cord during dynamic activities. In this work, a dynamic fluid-structure interaction model was developed and validated to investigate the effect of anterior and posterior encroachment caused by degenerative disease on the spinal cord during normal extension and flexion. Maximum von-Mises stress and maximum principal strain were observed at the end of extension and flexion. The abnormal stress distribution caused by degenerative factors was concentrated in the descending tracts of the spinal cord. Our finding indicates that the excessive motion of the cervical spine could potentially exacerbate spinal cord injury and enlarge injury areas. Stress and strain remained low compared to extension during moderate flexion. This suggests that patients with cervical degenerative disease should avoid frequent or excessive flexion and extension which could result in motor function impairment, whereas moderate flexion is safe. Besides, encroachment caused by degenerative factors that are not significant in static imaging could also cause cord compression during normal activities.
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Rycman A, McLachlin S, Cronin DS. Comparison of numerical methods for cerebrospinal fluid representation and fluid-structure interaction during transverse impact of a finite element spinal cord model. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2022; 38:e3570. [PMID: 34997836 DOI: 10.1002/cnm.3570] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 01/04/2022] [Accepted: 01/05/2022] [Indexed: 06/14/2023]
Abstract
Spinal cord impacts can have devastating consequences. Computational models can investigate such impacts but require biofidelic numerical representations of the neural tissues and fluid-structure interaction with cerebrospinal fluid. Achieving this biofidelity is challenging, particularly for efficient implementation of the cerebrospinal fluid in full computational human body models. The goal of this study was to assess the biofidelity and computational efficiency of fluid-structure interaction methods representing the cerebrospinal fluid interacting with the spinal cord, dura, and pia mater using experimental pellet impact test data from bovine spinal cords. Building on an existing finite element model of the spinal cord and pia mater, an orthotropic hyperelastic constitutive model was proposed for the dura mater and fit to literature data. The dura mater and cerebrospinal fluid were integrated with the existing finite element model to assess four fluid-structure interaction methods under transverse impact: Lagrange, pressurized volume, smoothed particle hydrodynamics, and arbitrary Lagrangian-Eulerian. The Lagrange method resulted in an overly stiff mechanical response, whereas the pressurized volume method over-predicted compression of the neural tissues. Both the smoothed particle hydrodynamics and arbitrary Lagrangian-Eulerian methods were able to effectively model the impact response of the pellet on the dura mater, outflow of the cerebrospinal fluid, and compression of the spinal cord; however, the arbitrary Lagrangian-Eulerian compute time was approximately five times higher than smoothed particle hydrodynamics. Crucial to implementation in human body models, the smoothed particle hydrodynamics method provided a computationally efficient and representative approach to model spinal cord fluid-structure interaction during transverse impact.
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Affiliation(s)
- Aleksander Rycman
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Stewart McLachlin
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Duane S Cronin
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada
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Davies BM, Mowforth O, Gharooni AA, Tetreault L, Nouri A, Dhillon RS, Bednarik J, Martin AR, Young A, Takahashi H, Boerger TF, Newcombe VFJ, Zipser CM, Freund P, Koljonen PA, Rodrigues-Pinto R, Rahimi-Movaghar V, Wilson JR, Kurpad SN, Fehlings MG, Kwon BK, Harrop JS, Guest JD, Curt A, Kotter MRN. A New Framework for Investigating the Biological Basis of Degenerative Cervical Myelopathy [AO Spine RECODE-DCM Research Priority Number 5]: Mechanical Stress, Vulnerability and Time. Global Spine J 2022; 12:78S-96S. [PMID: 35174728 PMCID: PMC8859710 DOI: 10.1177/21925682211057546] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
STUDY DESIGN Literature Review (Narrative). OBJECTIVE To propose a new framework, to support the investigation and understanding of the pathobiology of DCM, AO Spine RECODE-DCM research priority number 5. METHODS Degenerative cervical myelopathy is a common and disabling spinal cord disorder. In this perspective, we review key knowledge gaps between the clinical phenotype and our biological models. We then propose a reappraisal of the key driving forces behind DCM and an individual's susceptibility, including the proposal of a new framework. RESULTS Present pathobiological and mechanistic knowledge does not adequately explain the disease phenotype; why only a subset of patients with visualized cord compression show clinical myelopathy, and the amount of cord compression only weakly correlates with disability. We propose that DCM is better represented as a function of several interacting mechanical forces, such as shear, tension and compression, alongside an individual's vulnerability to spinal cord injury, influenced by factors such as age, genetics, their cardiovascular, gastrointestinal and nervous system status, and time. CONCLUSION Understanding the disease pathobiology is a fundamental research priority. We believe a framework of mechanical stress, vulnerability, and time may better represent the disease as a whole. Whilst this remains theoretical, we hope that at the very least it will inspire new avenues of research that better encapsulate the full spectrum of disease.
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Affiliation(s)
| | - Oliver Mowforth
- Department of Neurosurgery, University of Cambridge, Cambridge, UK
| | | | - Lindsay Tetreault
- New York University, Langone Health, Graduate Medical Education, Department of Neurology, New York, NY, USA
| | - Aria Nouri
- Division of Neurosurgery, Geneva University Hospitals, University of Geneva, Genève, Switzerland
| | - Rana S. Dhillon
- Department of Neurosurgery, St Vincent’s Hospital Melbourne, Fitzroy, VIC, Australia
| | - Josef Bednarik
- Department of Neurology, University Hospital Brno and Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Allan R. Martin
- Department of Neurosurgery, University of California Davis, Sacramento, CA, USA
| | - Adam Young
- Department of Neurosurgery, University of Cambridge, Cambridge, UK
| | - Hitoshi Takahashi
- Department of Pathology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Timothy F. Boerger
- Department of Neurosurgery, Medical College of Wisconsin, Wauwatosa, WI, USA
| | - Virginia FJ Newcombe
- Division of Anaesthesia, Department of Medicine, University of Cambridge, Cambridge, UK
| | - Carl Moritz Zipser
- University Spine Center, Balgrist University Hospital, Zurich, Switzerland
| | - Patrick Freund
- University Spine Center, Balgrist University Hospital, Zurich, Switzerland
| | - Paul Aarne Koljonen
- Department of Orthopaedics and Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Ricardo Rodrigues-Pinto
- Spinal Unit (UVM), Department of Orthopaedics, Centro Hospitalar Universitário do Porto - Hospital de Santo António, Porto, Portugal
- Instituto de Ciências Biomédicas Abel Salazar, Porto, Portugal
| | - Vafa Rahimi-Movaghar
- Department of Neurosurgery, Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Jefferson R. Wilson
- Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, ON, Canada
| | - Shekar N Kurpad
- Department of Neurosurgery, Medical College of Wisconsin, Wauwatosa, WI, USA
| | - Michael G. Fehlings
- Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, ON, Canada
| | - Brian K. Kwon
- Vancouver Spine Surgery Institute, Department of Orthopedics, The University of British Columbia, Vancouver, BC, Canada
| | - James S. Harrop
- Department of Neurological Surgery, Thomas Jefferson University, Philadelphia, PA, USA
| | - James D. Guest
- Department of Neurosurgery and the Miami Project to Cure Paralysis, The Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Armin Curt
- University Spine Center, Balgrist University Hospital, Zurich, Switzerland
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Rycman A, McLachlin S, Cronin DS. A Hyper-Viscoelastic Continuum-Level Finite Element Model of the Spinal Cord Assessed for Transverse Indentation and Impact Loading. Front Bioeng Biotechnol 2021; 9:693120. [PMID: 34458242 PMCID: PMC8387872 DOI: 10.3389/fbioe.2021.693120] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 07/15/2021] [Indexed: 11/22/2022] Open
Abstract
Finite Element (FE) modelling of spinal cord response to impact can provide unique insights into the neural tissue response and injury risk potential. Yet, contemporary human body models (HBMs) used to examine injury risk and prevention across a wide range of impact scenarios often lack detailed integration of the spinal cord and surrounding tissues. The integration of a spinal cord in contemporary HBMs has been limited by the need for a continuum-level model owing to the relatively large element size required to be compatible with HBM, and the requirement for model development based on published material properties and validation using relevant non-linear material data. The goals of this study were to develop and assess non-linear material model parameters for the spinal cord parenchyma and pia mater, and incorporate these models into a continuum-level model of the spinal cord with a mesh size conducive to integration in HBM. First, hyper-viscoelastic material properties based on tissue-level mechanical test data for the spinal cord and hyperelastic material properties for the pia mater were determined. Secondly, the constitutive models were integrated in a spinal cord segment FE model validated against independent experimental data representing transverse compression of the spinal cord-pia mater complex (SCP) under quasi-static indentation and dynamic impact loading. The constitutive model parameters were fit to a quasi-linear viscoelastic model with an Ogden hyperelastic function, and then verified using single element test cases corresponding to the experimental strain rates for the spinal cord (0.32–77.22 s−1) and pia mater (0.05 s−1). Validation of the spinal cord model was then performed by re-creating, in an explicit FE code, two independent ex-vivo experimental setups: 1) transverse indentation of a porcine spinal cord-pia mater complex and 2) dynamic transverse impact of a bovine SCP. The indentation model accurately matched the experimental results up to 60% compression of the SCP, while the impact model predicted the loading phase and the maximum deformation (within 7%) of the SCP experimental data. This study quantified the important biomechanical contribution of the pia mater tissue during spinal cord deformation. The validated material models established in this study can be implemented in computational HBM.
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Affiliation(s)
- Aleksander Rycman
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
| | - Stewart McLachlin
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
| | - Duane S Cronin
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
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Diotalevi L, Bailly N, Wagnac É, Mac-Thiong JM, Goulet J, Petit Y. Dynamics of spinal cord compression with different patterns of thoracolumbar burst fractures: Numerical simulations using finite element modelling. Clin Biomech (Bristol, Avon) 2020; 72:186-194. [PMID: 31901589 DOI: 10.1016/j.clinbiomech.2019.12.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 12/15/2019] [Accepted: 12/23/2019] [Indexed: 02/07/2023]
Abstract
BACKGROUND In thoracolumbar burst fractures, spinal cord primary injury involves a direct impact and energy transfer from bone fragments to the spinal cord. Unfortunately, imaging studies performed after the injury only depict the residual bone fragments position and pattern of spinal cord compression, with little insight on the dynamics involved during traumas. Knowledge of underlying mechanisms could be helpful in determining the severity of the primary injury, hence the extent of spinal cord damage and associated potential for recovery. Finite element models are often used to study dynamic processes, but have never been used specifically to simulate different severities of thoracolumbar burst fractures. METHODS Previously developed thoracolumbar spine and spinal cord finite element models were used and further validated, and representative vertebral fragments were modelled. A full factorial design was used to investigate the effects of comminution of the superior fragment, presence of an inferior fragment, fragments rotation and velocity, on maximum Von Mises stress and strain, maximum major strain, and pressure in the spinal cord. FINDINGS Fragment velocity clearly was the most influential factor. Fragments rotation and presence of an inferior fragment increased pressure, but rotation decreased both strains outputs. Although significant for both strains outputs, comminution of the superior fragment isn't estimated to influence outputs. INTERPRETATION This study is the first, to the authors' knowledge, to examine a detailed spinal cord model impacted in situ by fragments from burst fractures. This numeric model could be used in the future to comprehensively link traumatic events or imaging study characteristics to known spinal cord injuries severity and potential for recovery.
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Affiliation(s)
- Lucien Diotalevi
- Department of Mechanical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Street West, Montréal, Québec H3C 1K3, Canada; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin blvd, Montréal H4J 1C5, Québec, Canada; International Laboratory on Spine Imaging and Biomechanics (iLab-Spine), Canada
| | - Nicolas Bailly
- Department of Mechanical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Street West, Montréal, Québec H3C 1K3, Canada; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin blvd, Montréal H4J 1C5, Québec, Canada; International Laboratory on Spine Imaging and Biomechanics (iLab-Spine), Canada
| | - Éric Wagnac
- Department of Mechanical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Street West, Montréal, Québec H3C 1K3, Canada; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin blvd, Montréal H4J 1C5, Québec, Canada; International Laboratory on Spine Imaging and Biomechanics (iLab-Spine), Canada.
| | - Jean-Marc Mac-Thiong
- Research Center, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin blvd, Montréal H4J 1C5, Québec, Canada; Department of Orthopaedic Surgery, Université de Montréal, P.O. box 6128, Station Centre-Ville, Montréal, Québec H3C 3J7, Canada
| | - Julien Goulet
- Research Center, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin blvd, Montréal H4J 1C5, Québec, Canada; Department of Orthopaedic Surgery, Université de Montréal, P.O. box 6128, Station Centre-Ville, Montréal, Québec H3C 3J7, Canada.
| | - Yvan Petit
- Department of Mechanical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Street West, Montréal, Québec H3C 1K3, Canada; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin blvd, Montréal H4J 1C5, Québec, Canada; International Laboratory on Spine Imaging and Biomechanics (iLab-Spine), Canada.
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Differences in Morphometric Measures of the Uninjured Porcine Spinal Cord and Dural Sac Predict Histological and Behavioral Outcomes after Traumatic Spinal Cord Injury. J Neurotrauma 2019; 36:3005-3017. [DOI: 10.1089/neu.2018.5930] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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Jones CF, Clarke EC. Engineering approaches to understanding mechanisms of spinal column injury leading to spinal cord injury. Clin Biomech (Bristol, Avon) 2019; 64:69-81. [PMID: 29625748 DOI: 10.1016/j.clinbiomech.2018.03.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 02/16/2018] [Accepted: 03/24/2018] [Indexed: 02/07/2023]
Abstract
BACKGROUND The mechanical interactions occurring between the spinal column and spinal cord during an injury event are complex and variable, and likely have implications for the clinical presentation and prognosis of the individual. METHODS The engineering approaches that have been developed to better understand spinal column and cord interactions during an injury event are discussed. These include injury models utilising human and animal cadaveric specimens, in vivo anaesthetised animals, finite element models, inanimate physical systems and combinations thereof. FINDINGS The paper describes the development of these modelling approaches, discusses the advantages and disadvantages of the various models, and the major outcomes that have had implications for spinal cord injury research and clinical practice. INTERPRETATION The contribution of these four engineering approaches to understanding the interaction between the biomechanics and biology of spinal cord injury is substantial; they have improved our understanding of the factors contributing to the spinal column disruption, the degree of spinal cord deformation or motion, and the resultant neurological deficit and imaging features. Models of the injury event are challenging to produce, but technological advances are likely to improve these models and, consequently, our understanding of the mechanical context in which the biological injury occurs.
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Affiliation(s)
- Claire F Jones
- Spinal Research Group, Centre for Orthopaedics and Trauma Research, Adelaide Medical School, The University of Adelaide, Australia; School of Mechanical Engineering, The University of Adelaide, Australia
| | - Elizabeth C Clarke
- Institute for Bone and Joint Research, Kolling Institute, Sydney Medical School, University of Sydney, Australia.
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Lucas E, Whyte T, Liu J, Russell C, Tetzlaff W, Cripton PA. High-Speed Fluoroscopy to Measure Dynamic Spinal Cord Deformation in an In Vivo Rat Model. J Neurotrauma 2018; 35:2572-2580. [PMID: 29786472 DOI: 10.1089/neu.2017.5478] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Although spinal cord deformation is thought to be a predictor of injury severity, few researchers have investigated dynamic cord deformation, in vivo, during impact. This is needed to establish correlations among impact parameters, internal cord deformation, and histological and functional outcomes. Relying on surface deformations alone may not sufficiently represent spinal cord deformation. The objective of this study was to develop a high-speed fluoroscopic method of tracking the surface and internal cord deformations of rat spinal cord during experimental cord injury. Two radio-opaque beads were injected into the cord at C5/6 in the dorsal and ventral white matter. Four additional beads were glued to the surface of the cord. Dynamic bead displacement was tracked during a dorsal impact (130 mm/sec, 1 mm depth) by high-speed radiographic imaging at 3000 FPS, laterally. The internal spinal cord beads displaced significantly more than the surface beads in the ventral direction (1.1-1.9 times) and more than most surface beads in the cranial direction (1.2-1.5 times). The dorsal beads (internal and surface) displaced more than the ventral beads during all impacts. The bead displacement pattern implies that the spinal cord undergoes complex internal and surface deformations during impact. Residual displacement of the internal beads was significantly greater than that of the surface beads in the cranial-caudal direction but not the dorsoventral direction. Finite element simulation confirmed that the additional bead mass likely had little effect on the internal cord deformations. These results support the merit of this technique for measuring in vivo spinal cord deformation.
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Affiliation(s)
- Erin Lucas
- 1 Orthopaedic Injury Biomechanics Group, Departments of Mechanical Engineering and Orthopaedics and the School of Biomedical Engineering, The University of British Columbia , Vancouver, British Columbia, Canada .,2 International Collaboration on Repair Discoveries (ICORD), The University of British Columbia , Vancouver, British Columbia, Canada
| | - Thomas Whyte
- 1 Orthopaedic Injury Biomechanics Group, Departments of Mechanical Engineering and Orthopaedics and the School of Biomedical Engineering, The University of British Columbia , Vancouver, British Columbia, Canada .,2 International Collaboration on Repair Discoveries (ICORD), The University of British Columbia , Vancouver, British Columbia, Canada
| | - Jie Liu
- 2 International Collaboration on Repair Discoveries (ICORD), The University of British Columbia , Vancouver, British Columbia, Canada
| | - Colin Russell
- 1 Orthopaedic Injury Biomechanics Group, Departments of Mechanical Engineering and Orthopaedics and the School of Biomedical Engineering, The University of British Columbia , Vancouver, British Columbia, Canada .,2 International Collaboration on Repair Discoveries (ICORD), The University of British Columbia , Vancouver, British Columbia, Canada
| | - Wolfram Tetzlaff
- 2 International Collaboration on Repair Discoveries (ICORD), The University of British Columbia , Vancouver, British Columbia, Canada
| | - Peter Alec Cripton
- 1 Orthopaedic Injury Biomechanics Group, Departments of Mechanical Engineering and Orthopaedics and the School of Biomedical Engineering, The University of British Columbia , Vancouver, British Columbia, Canada .,2 International Collaboration on Repair Discoveries (ICORD), The University of British Columbia , Vancouver, British Columbia, Canada
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Ramo N, Shetye SS, Puttlitz CM. Damage Accumulation Modeling and Rate Dependency of Spinal Dura Mater. ACTA ACUST UNITED AC 2017; 1:0110061-110068. [DOI: 10.1115/1.4038261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 10/17/2017] [Indexed: 11/08/2022]
Abstract
As the strongest of the meningeal tissues, the spinal dura mater plays an important role in the overall behavior of the spinal cord-meningeal complex (SCM). It follows that the accumulation of damage affects the dura mater's ability to protect the cord from excessive mechanical loads. Unfortunately, current computational investigations of spinal cord injury (SCI) etiology typically do not include postyield behavior. Therefore, a more detailed description of the material behavior of the spinal dura mater, including characterization of damage accumulation, is required to comprehensively study SCI. Continuum mechanics-based viscoelastic damage theories have been previously applied to other biological tissues; however, the current work is the first to report damage accumulation modeling in a tissue of the SCM complex. Longitudinal (i.e., cranial-to-caudal long-axis) samples of ovine cervical dura mater were tensioned-to-failure at one of three strain rates (quasi-static, 0.05/s, and 0.3/s). The resulting stress–strain data were fit to a hyperelastic continuum damage model to characterize the strain-rate-dependent subfailure and failure behavior. The results show that the damage behavior of the fibrous and matrix components of the dura mater are strain-rate dependent, with distinct behaviors when exposed to strain rates above that experienced during normal voluntary neck motion suggesting the possible existence of a protective mechanism.
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Affiliation(s)
- Nicole Ramo
- School of Biomedical Engineering, Colorado State University, 1376 Campus Delivery, Fort Collins, CO 80523-1376
| | - Snehal S. Shetye
- Department of Mechanical Engineering, Colorado State University, 1374 Campus Delivery, Fort Collins, CO 80523-1374
| | - Christian M. Puttlitz
- School of Biomedical Engineering, Department of Mechanical Engineering, Department of Clinical Sciences, Colorado State University, 1374 Campus Delivery, Fort Collins, CO 80523-1374
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Facchinello Y, Wagnac É, Ung B, Petit Y, Pradhan P, Peyrache LM, Mac-Thiong JM. Development of an instrumented spinal cord surrogate using optical fibers: A feasibility study. Med Eng Phys 2017; 48:212-216. [PMID: 28687472 DOI: 10.1016/j.medengphy.2017.06.033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 06/15/2017] [Accepted: 06/17/2017] [Indexed: 11/17/2022]
Abstract
In vitro replication of traumatic spinal cord injury is necessary to understand its biomechanics and to improve animal models. During a traumatic spinal cord injury, the spinal cord withstands an impaction at high velocity. In order to fully assess the impaction, the use of spinal canal occlusion sensor is necessary. A physical spinal cord surrogate is also often used to simulate the presence of the spinal cord and its surrounding structures. In this study, an instrumented physical spinal cord surrogate is presented and validated. The sensing is based on light transmission loss observed in embedded bare optical fibers subjected to bending. The instrumented surrogate exhibits similar mechanical properties under static compression compared to fresh porcine spinal cords. The instrumented surrogate has a compression sensing threshold of 40% that matches the smallest compression values leading to neurological injuries. The signal obtained from the sensor allows calculating the compression of the spinal cord surrogate with a maximum of 5% deviation. Excellent repeatability was also observed under repetitive loading. The proposed instrumented spinal cord surrogate is promising with satisfying mechanical properties and good sensing capability. It is the first attempt at proposing a method to assess the internal loads sustained by the spinal cord during a traumatic injury.
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Affiliation(s)
- Yann Facchinello
- Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, Gouin Boul. West, Montreal, Quebec H4J 1C5, Canada ; Department of Surgery, Faculty of Medicine, University of Montreal, Pavillon Roger-Gaudry, S-749, C.P. 6128, succ. Centre-ville, Montreal, Quebec H3C 3J7, Canada
| | - Éric Wagnac
- Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, Gouin Boul. West, Montreal, Quebec H4J 1C5, Canada ; École de technologie supérieure, 1100 Notre-Dame Street West, Montreal, Quebec H3C 1K3, Canada.
| | - Bora Ung
- École de technologie supérieure, 1100 Notre-Dame Street West, Montreal, Quebec H3C 1K3, Canada
| | - Yvan Petit
- Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, Gouin Boul. West, Montreal, Quebec H4J 1C5, Canada ; École de technologie supérieure, 1100 Notre-Dame Street West, Montreal, Quebec H3C 1K3, Canada
| | - Prabin Pradhan
- École de technologie supérieure, 1100 Notre-Dame Street West, Montreal, Quebec H3C 1K3, Canada
| | - Louis-Marie Peyrache
- Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, Gouin Boul. West, Montreal, Quebec H4J 1C5, Canada ; École de technologie supérieure, 1100 Notre-Dame Street West, Montreal, Quebec H3C 1K3, Canada
| | - Jean-Marc Mac-Thiong
- Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, Gouin Boul. West, Montreal, Quebec H4J 1C5, Canada ; Department of Surgery, Faculty of Medicine, University of Montreal, Pavillon Roger-Gaudry, S-749, C.P. 6128, succ. Centre-ville, Montreal, Quebec H3C 3J7, Canada
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Khuyagbaatar B, Kim K, Man Park W, Hyuk Kim Y. Biomechanical Behaviors in Three Types of Spinal Cord Injury Mechanisms. J Biomech Eng 2016; 138:2528303. [DOI: 10.1115/1.4033794] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Indexed: 01/08/2023]
Abstract
Clinically, spinal cord injuries (SCIs) are radiographically evaluated and diagnosed from plain radiographs, computed tomography (CT), and magnetic resonance imaging. However, it is difficult to conclude that radiographic evaluation of SCI can directly explain the fundamental mechanism of spinal cord damage. The von-Mises stress and maximum principal strain are directly associated with neurological damage in the spinal cord from a biomechanical viewpoint. In this study, the von-Mises stress and maximum principal strain in the spinal cord as well as the cord cross-sectional area (CSA) were analyzed under various magnitudes for contusion, dislocation, and distraction SCI mechanisms, using a finite-element (FE) model of the cervical spine with spinal cord including white matter, gray matter, dura mater with nerve roots, and cerebrospinal fluid (CSF). A regression analysis was performed to find correlation between peak von-Mises stress/peak maximum principal strain at the cross section of the highest reduction in CSA and corresponding reduction in CSA of the cord. Dislocation and contusion showed greater peak stress and strain values in the cord than distraction. The substantial increases in von-Mises stress as well as CSA reduction similar to or more than 30% were produced at a 60% contusion and a 60% dislocation, while the maximum principal strain was gradually increased as injury severity elevated. In addition, the CSA reduction had a strong correlation with peak von-Mises stress/peak maximum principal strain for the three injury mechanisms, which might be fundamental information in elucidating the relationship between radiographic and mechanical parameters related to SCI.
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Affiliation(s)
- Batbayar Khuyagbaatar
- Department of Mechanical Engineering, Kyung Hee University, 1 Seocheon-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-701, Korea e-mail:
| | - Kyungsoo Kim
- Department of Applied Mathematics, Kyung Hee University, 1 Seocheon-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-701, Korea e-mail:
| | - Won Man Park
- Department of Mechanical Engineering, Kyung Hee University, 1 Seocheon-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-701, Korea e-mail:
| | - Yoon Hyuk Kim
- Department of Mechanical Engineering, Kyung Hee University, 1 Seocheon-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-701, Korea e-mail:
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Khuyagbaatar B, Kim K, Park WM, Kim YH. Influence of sagittal and axial types of ossification of posterior longitudinal ligament on mechanical stress in cervical spinal cord: A finite element analysis. Clin Biomech (Bristol, Avon) 2015; 30:1133-9. [PMID: 26351002 DOI: 10.1016/j.clinbiomech.2015.08.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 08/18/2015] [Accepted: 08/19/2015] [Indexed: 02/07/2023]
Abstract
BACKGROUND There are few studies focusing on the prediction of stress distribution according to the types of ossification of the posterior longitudinal ligament, which can be fundamental information associated with clinical aspects such as the relationship between stress level and neurological symptom severity. In this study, the influence of sagittal and axial types of ossification of the posterior longitudinal ligament on mechanical stress in the cervical spinal cord was investigated. METHODS A three-dimensional finite element model of the cervical spine with spinal cord was developed and validated. The von Mises stresses in the cord and the reduction in cross-sectional areas and volume of the cord were investigated for various axial and sagittal types according to the occupying ratio of ossification of the posterior longitudinal ligament in the spinal canal. FINDINGS The influence of axial type was less than that of the sagittal type, even though the central type showed higher maximum stresses in the cord, especially for the continuous type. With a 60% occupying ratio of ossification of the posterior longitudinal ligament, the maximum stress was significantly high and the cross-sectional area of the spinal cord was reduced by more than 30% of the intact area regardless of sagittal or axial types. Finally, a higher level of sagittal extension would increase the peak cord tissue stress, which would be related to the neurological dysfunction and tissue damage. INTERPRETATION Quantitative investigation of biomechanical characteristics such as mechanical stress may provide fundamental information for pre-operative planning of treatment for ossification of the posterior longitudinal ligament.
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Affiliation(s)
| | - Kyungsoo Kim
- Department of Applied Mathematics, Kyung Hee University, Yongin, Korea
| | - Won Man Park
- Department of Mechanical Engineering, Kyung Hee University, Yongin, Korea
| | - Yoon Hyuk Kim
- Department of Mechanical Engineering, Kyung Hee University, Yongin, Korea.
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The morphological and clinical significance of developmental cervical stenosis. 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 2015; 24:1583-9. [PMID: 25813007 DOI: 10.1007/s00586-015-3896-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 03/19/2015] [Accepted: 03/19/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE To investigate the difference of intra-dural space for spinal cord in magnetic resonance imaging between patients with and without developmental cervical stenosis and its clinical significance. METHODS 445 patients with cervical spondylotic myelopathy who had decompression surgeries were recruited. Based on their lateral radiographs, they were divided into stenosis and non-stenosis groups. On the magnetic resonance images, the ratio of the sagittal diameter of the dural sac to that of the vertebral body was measured and calculated as MRI Pavlov ratio at mid-vertebral level on sagittal images, and the ratio of the transverse area of the spinal cord to that of the dural sac was measured and calculated as occupation ratio on axial images from C3 to C7. The two ratios were compared between the two groups. We examined the correlations of the Pavlov ratio and the MRI Pavlov ratio between different vertebral levels. The correlation between the Pavlov ratio of each level and its corresponding MRI Pavlov ratio was also examined. The stenosis group was further divided into space-reserving and non-space-reserving subgroups based on their occupation ratios; then, clinical parameters were compared between the two subgroups to determine the clinical significance of the reserving space. RESULTS The MRI Pavlov ratio of the stenosis group was significantly smaller at C3-C7 (P < 0.001), while the occupation ratio was larger without significance. The Pavlov and MRI Pavlov ratios were correlated significantly at different levels (P < 0.001). The Pavlov ratio correlated significantly with its corresponding MRI Pavlov ratio at each level (P < 0.001). For space-reserving subgroup, the recovery rate was lower (P < 0.05) than that for non-space-reserving group, and was higher in anterior approach than that in posterior approach (P < 0.05). CONCLUSIONS Developmental cervical stenosis is associated with a smaller sagittal diameter of dural sac, but does not lead to a significant decrease of intra-dural space available for the cord. For patients with normal intra-dural space, the recovery after anterior decompression surgery was better.
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Khuyagbaatar B, Kim K, Hyuk Kim Y. Effect of bone fragment impact velocity on biomechanical parameters related to spinal cord injury: A finite element study. J Biomech 2014; 47:2820-5. [DOI: 10.1016/j.jbiomech.2014.04.042] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 04/24/2014] [Accepted: 04/26/2014] [Indexed: 10/25/2022]
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Jones CF, Lee JHT, Burstyn U, Okon EB, Kwon BK, Cripton PA. Cerebrospinal Fluid Pressures Resulting From Experimental Traumatic Spinal Cord Injuries in a Pig Model. J Biomech Eng 2013; 135:101005. [DOI: 10.1115/1.4025100] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 07/29/2013] [Indexed: 12/21/2022]
Abstract
Despite considerable effort over the last four decades, research has failed to translate into consistently effective treatment options for spinal cord injury (SCI). This is partly attributed to differences between the injury response of humans and rodent models. Some of this difference could be because the cerebrospinal fluid (CSF) layer of the human spine is relatively large, while that of the rodents is extremely thin. We sought to characterize the fluid impulse induced in the CSF by experimental SCIs of moderate and high human-like severity, and to compare this with previous studies in which fluid impulse has been associated with neural tissue injury. We used a new in vivo pig model (n = 6 per injury group, mean age 124.5 days, 20.9 kg) incorporating four miniature pressure transducers that were implanted in pairs in the subarachnoid space, cranial, and caudal to the injury at 30 mm and 100 mm. Tissue sparing was assessed with Eriochrome Cyanine and Neutral Red staining. The median peak pressures near the injury were 522.5 and 868.8 mmHg (range 96.7–1430.0) and far from the injury were 7.6 and 36.3 mmHg (range 3.8–83.7), for the moderate and high injury severities, respectively. Pressure impulse (mmHg.ms), apparent wave speed, and apparent attenuation factor were also evaluated. The data indicates that the fluid pressure wave may be sufficient to affect the severity and extent of primary tissue damage close to the injury site. However, the CSF pressure was close to normal physiologic values at 100 mm from the injury. The high injury severity animals had less tissue sparing than the moderate injury severity animals; this difference was statistically significant only within 1.6 mm of the epicenter. These results indicate that future research seeking to elucidate the mechanical origins of primary tissue damage in SCI should consider the effects of CSF. This pig model provides advantages for basic and preclinical SCI research due to its similarities to human scale, including the existence of a human-like CSF fluid layer.
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Affiliation(s)
- Claire F. Jones
- Orthopaedic and Injury Biomechanics Group, Departments of Mechanical Engineering and Orthopaedics, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
- International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, BC V5Z 1M9, Canada e-mail:
| | | | | | - Elena B. Okon
- e-mail: International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, BC V5Z 1M9, Canada
| | - Brian K. Kwon
- Associate Professor Combined Neurosurgical and Orthopaedic Spine Program (CNOSP), Department of Orthopaedics, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
- International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, BC V5Z 1M9, Canada e-mail:
| | - Peter A. Cripton
- Orthopaedic and Injury Biomechanics Group, Departments of Mechanical Engineering and Orthopaedics, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
- International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, BC V5Z 1M9, Canada e-mail:
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Soubeyrand M, Laemmel E, Court C, Dubory A, Vicaut E, Duranteau J. Rat model of spinal cord injury preserving dura mater integrity and allowing measurements of cerebrospinal fluid pressure and spinal cord blood flow. 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; 22:1810-9. [PMID: 23508337 DOI: 10.1007/s00586-013-2744-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 02/25/2013] [Accepted: 03/05/2013] [Indexed: 01/14/2023]
Abstract
PURPOSES Cerebrospinal fluid (CSF) pressure elevation may worsen spinal cord ischaemia after spinal cord injury (SCI). We developed a rat model to investigate relationships between CSF pressure and spinal cord blood flow (SCBF). METHODS Male Wistar rats had SCI induced at Th10 (n = 7) or a sham operation (n = 10). SCBF was measured using laser-Doppler and CSF pressure via a sacral catheter. Dural integrity was assessed using subdural methylene-blue injection (n = 5) and myelography (n = 5). RESULTS The SCI group had significantly lower SCBF (p < 0.0001) and higher CSF pressure (p < 0.0001) values compared to the sham-operated group. Sixty minutes after SCI or sham operation, CSF pressure was 8.6 ± 0.4 mmHg in the SCI group versus 5.5 ± 0.5 mmHg in the sham-operated group. No dural tears were found after SCI. CONCLUSION Our rat model allows SCBF and CSF pressure measurements after induced SCI. After SCI, CSF pressure significantly increases.
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Affiliation(s)
- Marc Soubeyrand
- Equipe universitaire 3509 Paris VII-Paris XI-Paris XIII, Microcirculation, Bioénergétique, Inflammation et Insuffisance circulatoire aiguë, Paris Diderot-Paris VII University, Paris, France.
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Cheng C, Kmech J, Mushahwar VK, Elias AL. Development of surrogate spinal cords for the evaluation of electrode arrays used in intraspinal implants. IEEE Trans Biomed Eng 2013; 60:1667-76. [PMID: 23358939 DOI: 10.1109/tbme.2013.2241061] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We report the development of a surrogate spinal cord for evaluating the mechanical suitability of electrode arrays for intraspinal implants. The mechanical and interfacial properties of candidate materials (including silicone elastomers and gelatin hydrogels) for the surrogate cord were tested. The elastic modulus was characterized using dynamic mechanical analysis, and compared with values of actual human spinal cords from the literature. Forces required to indent the surrogate cords to specified depths were measured to obtain values under static conditions. Importantly, to quantify surface properties in addition to mechanical properties normally considered, interfacial frictional forces were measured by pulling a needle out of each cord at a controlled rate. The measured forces were then compared to those obtained from rat spinal cords. Formaldehyde-crosslinked gelatin, 12 wt% in water, was identified as the most suitable material for the construction of surrogate spinal cords. To demonstrate the utility of surrogate spinal cords in evaluating the behavior of various electrode arrays, cords were implanted with two types of intraspinal electrode arrays (one made of individual microwires and another of microwires anchored with a solid base), and cord deformation under elongation was evaluated. The results demonstrate that the surrogate model simulates the mechanical and interfacial properties of the spinal cord, and enables in vitro screening of intraspinal implants.
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Affiliation(s)
- Cheng Cheng
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 2V4, Canada.
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Jones CF, Lee JHT, Kwon BK, Cripton PA. Development of a large-animal model to measure dynamic cerebrospinal fluid pressure during spinal cord injury. J Neurosurg Spine 2012; 16:624-35. [DOI: 10.3171/2012.3.spine11970] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Object
Spinal cord injury (SCI) often results in considerable permanent neurological impairment, and unfortunately, the successful translation of effective treatments from laboratory models to human patients is lacking. This may be partially attributed to differences in anatomy, physiology, and scale between humans and rodent models. One potentially important difference between the rodent and human spinal cord is the presence of a significant CSF volume within the intrathecal space around the human cord. While the CSF may “cushion” the spinal cord, pressure waves within the CSF at the time of injury may contribute to the extent and severity of the primary injury. The objective of this study was to develop a model of contusion SCI in a miniature pig and establish the feasibility of measuring spinal CSF pressure during injury.
Methods
A custom weight-drop device was used to apply thoracic contusion SCI to 17 Yucatan miniature pigs. Impact load and velocity were measured. Using fiber optic pressure transducers implanted in the thecal sac, CSF pressures resulting from 2 injury severities (caused by 50-g and 100-g weights released from a 50-cm height) were measured.
Results
The median peak impact loads were 54 N and 132 N for the 50-g and 100-g injuries, respectively. At a nominal 100 mm from the injury epicenter, the authors observed a small negative pressure peak (median −4.6 mm Hg [cranial] and −5.8 mm Hg [caudal] for 50 g; −27.6 mm Hg [cranial] and −27.2 mm Hg [caudal] for 100 g) followed by a larger positive pressure peak (median 110.5 mm Hg [cranial] and 77.1 mm Hg [caudal] for 50 g; 88.4 mm Hg [cranial] and 67.2 mm Hg [caudal] for 100 g) relative to the preinjury pressure. There were no significant differences in peak pressure between the 2 injury severities or the caudal and cranial transducer locations.
Conclusions
A new model of contusion SCI was developed to measure spinal CSF pressures during the SCI event. The results suggest that the Yucatan miniature pig is an appropriate model for studying CSF, spinal cord, and dura interactions during injury. With further development and characterization it may be an appropriate in vivo largeanimal model of SCI to answer questions regarding pathological changes, therapeutic safety, or treatment efficacy, particularly where humanlike dimensions and physiology are important.
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Affiliation(s)
- Claire F. Jones
- 1Orthopaedic and Injury Biomechanics Laboratory, Departments of Mechanical Engineering and Orthopaedics,
- 2International Collaboration on Repair Discoveries, and
| | - Jae H. T. Lee
- 2International Collaboration on Repair Discoveries, and
| | - Brian K. Kwon
- 2International Collaboration on Repair Discoveries, and
- 3Combined Neurosurgical and Orthopaedic Spine Program, Department of Orthopaedics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Peter A. Cripton
- 1Orthopaedic and Injury Biomechanics Laboratory, Departments of Mechanical Engineering and Orthopaedics,
- 2International Collaboration on Repair Discoveries, and
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Russell CM, Choo AM, Tetzlaff W, Chung TE, Oxland TR. Maximum principal strain correlates with spinal cord tissue damage in contusion and dislocation injuries in the rat cervical spine. J Neurotrauma 2012; 29:1574-85. [PMID: 22320127 DOI: 10.1089/neu.2011.2225] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The heterogeneity of the primary mechanical mechanism of spinal cord injury (SCI) is not currently used to tailor treatment strategies because the effects of these distinct patterns of acute mechanical damage on long-term neuropathology have not been fully investigated. A computational model of SCI enables the dynamic analysis of mechanical forces and deformations within the spinal cord tissue that would otherwise not be visible from histological tissue sections. We created a dynamic, three-dimensional finite element (FE) model of the rat cervical spine and simulated contusion and dislocation SCI mechanisms. We investigated the relationship between maximum principal strain and tissue damage, and compared primary injury patterns between mechanisms. The model incorporated the spinal cord white and gray matter, the dura mater, cerebrospinal fluid, spinal ligaments, intervertebral discs, a rigid indenter and vertebrae, and failure criteria for ligaments and vertebral endplates. High-speed (∼ 1 m/sec) contusion and dislocation injuries were simulated between vertebral levels C3 and C6 to match previous animal experiments, and average peak maximum principal strains were calculated for several regions at the injury epicenter and at 1-mm intervals from +5 mm rostral to -5 mm caudal to the lesion. Average peak principal strains were compared to tissue damage measured previously in the same regions via axonal permeability to 10-kD fluorescein-dextran. Linear regression of tissue damage against peak maximum principal strain for pooled data within all white matter regions yielded similar and significant (p<0.0001) correlations for both contusion (R(2)=0.86) and dislocation (R(2)=0.52). The model enhances our understanding of the differences in injury patterns between SCI mechanisms, and provides further evidence for the link between principal strain and tissue damage.
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Affiliation(s)
- Colin M Russell
- Orthopaedic and Injury Biomechanics Group, Departments of Orthopaedics and Mechanical Engineering, University of British Columbia, British Columbia, Canada
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Jones CF, Kwon BK, Cripton PA. Mechanical indicators of injury severity are decreased with increased thecal sac dimension in a bench-top model of contusion type spinal cord injury. J Biomech 2012; 45:1003-10. [DOI: 10.1016/j.jbiomech.2012.01.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 11/04/2011] [Accepted: 01/05/2012] [Indexed: 10/28/2022]
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The Effect of Cerebrospinal Fluid Thickness on Traumatic Spinal Cord Deformation. J Appl Biomech 2011; 27:330-5. [DOI: 10.1123/jab.27.4.330] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A spinal cord injury may lead to loss of motor and sensory function and even death. The biomechanics of the injury process have been found to be important to the neurological damage pattern, and some studies have found a protective effect of the cerebrospinal fluid (CSF). However, the effect of the CSF thickness on the cord deformation and, hence, the resulting injury has not been previously investigated. In this study, the effects of natural variability (in bovine) as well as the difference between bovine and human spinal canal dimensions on spinal cord deformation were studied using a previously validated computational model. Owing to the pronounced effect that the CSF thickness was found to have on the biomechanics of the cord deformation, it can be concluded that results from animal models may be affected by the disparities in the CSF layer thickness as well as by any difference in the biological responses they may have compared with those of humans.
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Saari A, Itshayek E, Cripton P. Cervical spinal cord deformation during simulated head-first impact injuries. J Biomech 2011; 44:2565-71. [DOI: 10.1016/j.jbiomech.2011.06.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 06/12/2011] [Accepted: 06/15/2011] [Indexed: 10/17/2022]
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Persson C, Summers J, Hall RM. The importance of fluid-structure interaction in spinal trauma models. J Neurotrauma 2010; 28:113-25. [PMID: 21047151 DOI: 10.1089/neu.2010.1332] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
While recent studies have demonstrated the importance of the initial mechanical insult in the severity of spinal cord injury, there is a lack of information on the detailed cord-column interaction during such events. In vitro models have demonstrated the protective properties of the cerebrospinal fluid, but visualization of the impact is difficult. In this study a computational model was developed in order to clarify the role of the cerebrospinal fluid and provide a more detailed picture of the cord-column interaction. The study was validated against a parallel in vitro study on bovine tissue. Previous assumptions about complete subdural collapse before any cord deformation were found to be incorrect. Both the presence of the dura mater and the cerebrospinal fluid led to a reduction in the longitudinal strains within the cord. The division of the spinal cord into white and grey matter perturbed the bone fragment trajectory only marginally. In conclusion, the cerebrospinal fluid had a significant effect on the deformation pattern of the cord during impact and should be included in future models. The type of material models used for the spinal cord and the dura mater were found to be important to the stress and strain values within the components, but less important to the fragment trajectory.
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Affiliation(s)
- Cecilia Persson
- School of Mechanical Engineering, University of Leeds, Leeds, United Kingdom.
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Kroeker SG, Morley PL, Jones CF, Bilston LE, Cripton PA. The development of an improved physical surrogate model of the human spinal cord--tension and transverse compression. J Biomech 2009; 42:878-83. [PMID: 19268950 DOI: 10.1016/j.jbiomech.2009.01.036] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Revised: 12/19/2008] [Accepted: 01/21/2009] [Indexed: 10/21/2022]
Abstract
To prevent spinal cord injury, optimize treatments for it, and better understand spinal cord pathologies such as spondylotic myelopathy, the interaction between the spinal column and the spinal cord during injury and pathology must be understood. The spinal cord is a complex and very soft tissue that changes properties rapidly after death and is difficult to model. Our objective was to develop a physical surrogate spinal cord with material properties closely corresponding to the in vivo human spinal cord that would be suitable for studying spinal cord injury under a variety of injurious conditions. Appropriate target material properties were identified from published studies and several candidate surrogate materials were screened, under uniaxial tension, in a materials testing machine. QM Skin 30, a silicone elastomer, was identified as the most appropriate material. Spinal cords manufactured from QM Skin 30 were tested under uniaxial tension and transverse compression. Rectangular specimens of QM Skin 30 were also tested under uniform compression. QM Skin 30 produced surrogate cords with a Young's modulus in tension and compression approximately matching values reported for in vivo animal spinal cords (0.25 and 0.20 MPa, respectively). The tensile and compressive Young's modulus and the behavior of the surrogate cord simulated the nonlinear behavior of the in vivo spinal cord.
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Affiliation(s)
- Shannon G Kroeker
- Injury Biomechanics Laboratory, Division of Orthopaedic Engineering Research and ICORD, Department of Mechanical Engineering, University of British Columbia, Vancouver, British Columbia, Canada
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