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Gould SL, Davico G, Palanca M, Viceconti M, Cristofolini L. Identification of a lumped-parameter model of the intervertebral joint from experimental data. Front Bioeng Biotechnol 2024; 12:1304334. [PMID: 39104629 PMCID: PMC11298350 DOI: 10.3389/fbioe.2024.1304334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 07/01/2024] [Indexed: 08/07/2024] Open
Abstract
Through predictive simulations, multibody models can aid the treatment of spinal pathologies by identifying optimal surgical procedures. Critical to achieving accurate predictions is the definition of the intervertebral joint. The joint pose is often defined by virtual palpation. Intervertebral joint stiffnesses are either derived from literature, or specimen-specific stiffnesses are calculated with optimisation methods. This study tested the feasibility of an optimisation method for determining the specimen-specific stiffnesses and investigated the influence of the assigned joint pose on the subject-specific estimated stiffness. Furthermore, the influence of the joint pose and the stiffness on the accuracy of the predicted motion was investigated. A computed tomography based model of a lumbar spine segment was created. Joints were defined from virtually palpated landmarks sampled with a Latin Hypercube technique from a possible Cartesian space. An optimisation method was used to determine specimen-specific stiffnesses for 500 models. A two-factor analysis was performed by running forward dynamic simulations for ten different stiffnesses for each successfully optimised model. The optimisations calculated a large range of stiffnesses, indicating the optimised specimen-specific stiffnesses were highly sensitive to the assigned joint pose and related uncertainties. A limited number of combinations of optimised joint stiffnesses and joint poses could accurately predict the kinematics. The two-factor analysis indicated that, for the ranges explored, the joint pose definition was more important than the stiffness. To obtain kinematic prediction errors below 1 mm and 1° and suitable specimen-specific stiffnesses the precision of virtually palpated landmarks for joint definition should be better than 2.9 mm.
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Affiliation(s)
- Samuele L. Gould
- Department of Industrial Engineering, Alma Mater Studiorum-University of Bologna, Bologna, Italy
- Medical Technology Lab, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Giorgio Davico
- Department of Industrial Engineering, Alma Mater Studiorum-University of Bologna, Bologna, Italy
- Medical Technology Lab, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Marco Palanca
- Department of Industrial Engineering, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Marco Viceconti
- Department of Industrial Engineering, Alma Mater Studiorum-University of Bologna, Bologna, Italy
- Medical Technology Lab, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Luca Cristofolini
- Department of Industrial Engineering, Alma Mater Studiorum-University of Bologna, Bologna, Italy
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2
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Caimi A, Ferguson SJ, Ignasiak D. Evaluation of trunk muscle coactivation predictions in multi-body models. J Biomech 2024; 168:112039. [PMID: 38657434 DOI: 10.1016/j.jbiomech.2024.112039] [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: 08/30/2023] [Revised: 02/28/2024] [Accepted: 03/04/2024] [Indexed: 04/26/2024]
Abstract
Musculoskeletal simulations with muscle optimization aim to minimize muscle effort, hence are considered unable to predict the activation of antagonistic muscles. However, activation of antagonistic muscles might be necessary to satisfy the dynamic equilibrium. This study aims to elucidate under which conditions coactivation can be predicted, to evaluate factors modulating it, and to compare the antagonistic activations predicted by the lumbar spine model with literature data. Simple 2D and 3D models, comprising of 2 or 3 rigid bodies, with simple or multi-joint muscles, were created to study conditions under which muscle coactivity is predicted. An existing musculoskeletal model of the lumbar spine developed in AnyBody was used to investigate the effects of modeling intra-abdominal pressure (IAP), linear/cubic and load/activity-based muscle recruitment criterion on predicted coactivation during forward flexion and lateral bending. The predicted antagonist activations were compared to reported EMG data. Muscle coactivity was predicted with simplified models when multi-joint muscles were present or the model was three-dimensional. During forward flexion and lateral bending, the coactivation ratio predicted by the model showed good agreement with experimental values. Predicted coactivation was negligibly influenced by IAP but substantially reduced with a force-based recruitment criterion. The conditions needed in multi-body models to predict coactivity are: three-dimensionality or multi-joint muscles, unless perfect antagonists. The antagonist activations are required to balance 3D moments but do not reflect other physiological phenomena, which might explain the discrepancies between model predictions and experimental data. Nevertheless, the findings confirm the ability of the multi-body trunk models to predict muscle coactivity and suggest their overall validity.
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Affiliation(s)
- Alice Caimi
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
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Lerchl T, Nispel K, Baum T, Bodden J, Senner V, Kirschke JS. Multibody Models of the Thoracolumbar Spine: A Review on Applications, Limitations, and Challenges. Bioengineering (Basel) 2023; 10:bioengineering10020202. [PMID: 36829696 PMCID: PMC9952620 DOI: 10.3390/bioengineering10020202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 01/30/2023] [Accepted: 01/31/2023] [Indexed: 02/09/2023] Open
Abstract
Numerical models of the musculoskeletal system as investigative tools are an integral part of biomechanical and clinical research. While finite element modeling is primarily suitable for the examination of deformation states and internal stresses in flexible bodies, multibody modeling is based on the assumption of rigid bodies, that are connected via joints and flexible elements. This simplification allows the consideration of biomechanical systems from a holistic perspective and thus takes into account multiple influencing factors of mechanical loads. Being the source of major health issues worldwide, the human spine is subject to a variety of studies using these models to investigate and understand healthy and pathological biomechanics of the upper body. In this review, we summarize the current state-of-the-art literature on multibody models of the thoracolumbar spine and identify limitations and challenges related to current modeling approaches.
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Affiliation(s)
- Tanja Lerchl
- Sport Equipment and Sport Materials, School of Engineering and Design, Technical University of Munich, 85748 Garching, Germany
- Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum Rechts der Isar, Technical University of Munich, 81675 Munich, Germany
- Correspondence: ; Tel.: +49-89-289-15365
| | - Kati Nispel
- Sport Equipment and Sport Materials, School of Engineering and Design, Technical University of Munich, 85748 Garching, Germany
- Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum Rechts der Isar, Technical University of Munich, 81675 Munich, Germany
| | - Thomas Baum
- Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum Rechts der Isar, Technical University of Munich, 81675 Munich, Germany
| | - Jannis Bodden
- Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum Rechts der Isar, Technical University of Munich, 81675 Munich, Germany
| | - Veit Senner
- Sport Equipment and Sport Materials, School of Engineering and Design, Technical University of Munich, 85748 Garching, Germany
| | - Jan S. Kirschke
- Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum Rechts der Isar, Technical University of Munich, 81675 Munich, Germany
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Knapik GG, Mendel E, Bourekas E, Marras WS. Computational lumbar spine models: A literature review. Clin Biomech (Bristol, Avon) 2022; 100:105816. [PMID: 36435080 DOI: 10.1016/j.clinbiomech.2022.105816] [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: 07/28/2022] [Revised: 10/26/2022] [Accepted: 11/08/2022] [Indexed: 11/15/2022]
Abstract
BACKGROUND Computational spine models of various types have been employed to understand spine function, assess the risk that different activities pose to the spine, and evaluate techniques to prevent injury. The areas in which these models are applied has expanded greatly, potentially beyond the appropriate scope of each, given their capabilities. A comprehensive understanding of the components of these models provides insight into their current capabilities and limitations. METHODS The objective of this review was to provide a critical assessment of the different characteristics of model elements employed across the spectrum of lumbar spine modeling and in newer combined methodologies to help better evaluate existing studies and delineate areas for future research and refinement. FINDINGS A total of 155 studies met selection criteria and were included in this review. Most current studies use either highly detailed Finite Element models or simpler Musculoskeletal models driven with in vivo data. Many models feature significant geometric or loading simplifications that limit their realism and validity. Frequently, studies only create a single model and thus can't account for the impact of subject variability. The lack of model representation for certain subject cohorts leaves significant gaps in spine knowledge. Combining features from both types of modeling could result in more accurate and predictive models. INTERPRETATION Development of integrated models combining elements from different model types in a framework that enables the evaluation of larger populations of subjects could address existing voids and enable more realistic representation of the biomechanics of the lumbar spine.
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Affiliation(s)
- Gregory G Knapik
- Spine Research Institute, The Ohio State University, 210 Baker Systems, 1971 Neil Avenue, Columbus, OH 43210, USA.
| | - Ehud Mendel
- Department of Neurosurgery, Yale University, New Haven, CT 06510, USA
| | - Eric Bourekas
- Department of Radiology, The Ohio State University, Columbus, OH 43210, USA
| | - William S Marras
- Spine Research Institute, The Ohio State University, 210 Baker Systems, 1971 Neil Avenue, Columbus, OH 43210, USA
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Effects of Artificially Induced Breast Augmentation on the Electromyographic Activity of Neck and Trunk Muscles during Common Daily Movements. J Funct Morphol Kinesiol 2022; 7:jfmk7040080. [PMID: 36278741 PMCID: PMC9590005 DOI: 10.3390/jfmk7040080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/18/2022] [Accepted: 09/27/2022] [Indexed: 11/12/2022] Open
Abstract
A female breast can be a potential source of musculoskeletal problems, especially if it is disproportionately large. The purpose of the present study was to examine the effect of artificially induced breast volume on the EMG activity of neck and trunk musculature during common everyday movements. The EMG activity of the sternocleidomastoid (SCM), the upper trapezius (UT), and the thoracic and lumbar erector spinae (TES, LES) were recorded during 45° trunk inclination from the upright standing and sitting postures (TIST45°, TISI45°) as well as during stand-to-sit and sit-to-stand (STSI, SIST) in 24 healthy females with minimal and ideal breast volume (M-NBV, I-NBV). All movements were performed before and after increasing M-NBV and I-NBV by 1.5-, 3.0-, 4.5-, and 6-times using silicone-gel implants. Significantly higher EMG activity for TES and LES were found at 6.0- and ≥4.5-times increase the I-NBV, respectively, compared to smaller breast volumes during TIST45°. EMG activity of UT was higher, and TES was lower in M-NBV females compared to I-NBV females in all movements but were significantly different only during SIST. The female breast can affect the activity of neck and trunk muscles only when its volume increases above a certain limit, potentially contributing to muscle dysfunction.
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Jalalian A, Arastehfar S, Gibson I, Tay FEH, Liu G. How Can Biomechanical Multibody Models of Scoliosis Be Accurate in Simulating Spine Movement Behavior While Neglecting the Changes of Spinal Length? J Biomech Eng 2021; 143:081004. [PMID: 33764411 DOI: 10.1115/1.4050636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Indexed: 11/08/2022]
Abstract
This paper studies how biomechanical multibody models of scoliosis can neglect the changes of spinal length and yet be accurate in reconstructing spinal columns. As these models with fixed length comprise rigid links interconnected by rotary joints, they resemble polygonal chains that approximate spine curves with a finite number of line segments. In mathematics, using more segments with shorter lengths can result in more accurate curve approximations. This raises the question of whether more accurate spine curve approximations by increasing the number of links/joints can yield more accurate spinal column reconstructions. For this, the accuracy of spine curve approximation was improved consistently by increasing the number of links/joints, and its effects on the accuracy of spinal column reconstruction were assessed. Positive correlation was found between the accuracy of spine reconstruction and curve approximation. It was shown that while increasing the accuracy of curve approximations, the representation of scoliosis concavity and its side-to-side deviations were improved. Moreover, reconstruction errors of the spine regions separated by the inflection vertebrae had minimal impacts on each other. Overall, multibody scoliosis models with fixed spinal lengths can benefit from the extra rotational joints that contribute toward the accuracy of spine curve approximation. The outcome of this study leads to concurrent accuracy improvement and simplification of multibody models; joint-link configurations can be independently defined for the regions separated by the inflection vertebrae, enabling local optimization of the models for higher accuracy without unnecessary added complexity to the whole model.
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Affiliation(s)
- Athena Jalalian
- Faculty of Engineering Technology, University of Twente, P.O. BOX 217, Enschede 7500 AE, The Netherlands
| | - Soheil Arastehfar
- Faculty of Engineering Technology, University of Twente, P.O. BOX 217, Enschede 7500 AE, The Netherlands
| | - Ian Gibson
- Faculty of Engineering Technology, University of Twente, P.O. BOX 217, Enschede, 7500 AE The Netherlands
| | - Francis E H Tay
- Faculty of Engineering, National University of Singapore, 21 Lower Kent Ridge Road, Singapore 119077, Singapore
| | - Gabriel Liu
- Department of Orthopedic Surgery, National University Hospital, 5 Lower Kent Ridge Road, Singapore 119074, Singapore
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Remus R, Lipphaus A, Neumann M, Bender B. Calibration and validation of a novel hybrid model of the lumbosacral spine in ArtiSynth-The passive structures. PLoS One 2021; 16:e0250456. [PMID: 33901222 PMCID: PMC8075237 DOI: 10.1371/journal.pone.0250456] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 04/07/2021] [Indexed: 12/04/2022] Open
Abstract
In computational biomechanics, two separate types of models have been used predominantly to enhance the understanding of the mechanisms of action of the lumbosacral spine (LSS): Finite element (FE) and musculoskeletal multibody (MB) models. To combine advantages of both models, hybrid FE-MB models are an increasingly used alternative. The aim of this paper is to develop, calibrate, and validate a novel passive hybrid FE-MB open-access simulation model of a ligamentous LSS using ArtiSynth. Based on anatomical data from the Male Visible Human Project, the LSS model is constructed from the L1-S1 rigid vertebrae interconnected with hyperelastic fiber-reinforced FE intervertebral discs, ligaments, and facet joints. A mesh convergence study, sensitivity analyses, and systematic calibration were conducted with the hybrid functional spinal unit (FSU) L4/5. The predicted mechanical responses of the FSU L4/5, the lumbar spine (L1-L5), and the LSS were validated against literature data from in vivo and in vitro measurements and in silico models. Spinal mechanical responses considered when loaded with pure moments and combined loading modes were total and intervertebral range of motions, instantaneous axes and centers of rotation, facet joint contact forces, intradiscal pressures, disc bulges, and stiffnesses. Undesirable correlations with the FE mesh were minimized, the number of crisscrossed collagen fiber rings was reduced to five, and the individual influences of specific anatomical structures were adjusted to in vitro range of motions. Including intervertebral motion couplings for axial rotation and nonlinear stiffening under increasing axial compression, the predicted kinematic and structural mechanics responses were consistent with the comparative data. The results demonstrate that the hybrid simulation model is robust and efficient in reproducing valid mechanical responses to provide a starting point for upcoming optimizations and extensions, such as with active skeletal muscles.
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Affiliation(s)
- Robin Remus
- Chair of Product Development, Department of Mechanical Engineering, Ruhr-University Bochum, Bochum, Germany
- * E-mail:
| | - Andreas Lipphaus
- Biomechanics Research Group, Chair of Product Development, Department of Mechanical Engineering, Ruhr-University Bochum, Bochum, Germany
| | - Marc Neumann
- Chair of Product Development, Department of Mechanical Engineering, Ruhr-University Bochum, Bochum, Germany
| | - Beate Bender
- Chair of Product Development, Department of Mechanical Engineering, Ruhr-University Bochum, Bochum, Germany
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8
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Tennant LM, Nelson-Wong E, Kuest J, Lawrence G, Levesque K, Owens D, Prisby J, Spivey S, Albin SR, Jagger K, Barrett JM, Wong JD, Callaghan JP. A Comparison of Clinical Spinal Mobility Measures to Experimentally Derived Lumbar Spine Passive Stiffness. J Appl Biomech 2020; 36:397-407. [PMID: 33049702 DOI: 10.1123/jab.2020-0030] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 05/12/2020] [Accepted: 06/17/2020] [Indexed: 11/18/2022]
Abstract
Spinal stiffness and mobility assessments vary between clinical and research settings, potentially hindering the understanding and treatment of low back pain. A total of 71 healthy participants were evaluated using 2 clinical assessments (posteroanterior spring and passive intervertebral motion) and 2 quantitative measures: lumped mechanical stiffness of the lumbar spine and local tissue stiffness (lumbar erector spinae and supraspinous ligament) measured via myotonometry. The authors hypothesized that clinical, mechanical, and local tissue measures would be correlated, that clinical tests would not alter mechanical stiffness, and that males would demonstrate greater lumbar stiffness than females. Clinical, lumped mechanical, and tissue stiffness were not correlated; however, gradings from the posteroanterior spring and passive intervertebral motion tests were positively correlated with each other. Clinical assessments had no effect on lumped mechanical stiffness. The males had greater lumped mechanical and lumbar erector spinae stiffness compared with the females. The lack of correlation between clinical, tissue, and lumped mechanical measures of spinal stiffness indicates that the use of the term "stiffness" by clinicians may require reevaluation; clinicians should be confident that they are not altering mechanical stiffness of the spine through segmental mobility assessments; and greater resting lumbar erector stiffness in males suggests that sex should be considered in the assessment and treatment of the low back.
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9
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Wang W, Wang D, De Groote F, Scheys L, Jonkers I. Implementation of physiological functional spinal units in a rigid-body model of the thoracolumbar spine. J Biomech 2020; 98:109437. [DOI: 10.1016/j.jbiomech.2019.109437] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 09/14/2019] [Accepted: 10/17/2019] [Indexed: 11/30/2022]
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Load-sharing in the lumbosacral spine in neutral standing & flexed postures – A combined finite element and inverse static study. J Biomech 2018; 70:43-50. [DOI: 10.1016/j.jbiomech.2017.10.033] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 10/18/2017] [Accepted: 10/27/2017] [Indexed: 12/22/2022]
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11
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Senteler M, Aiyangar A, Weisse B, Farshad M, Snedeker JG. Sensitivity of intervertebral joint forces to center of rotation location and trends along its migration path. J Biomech 2018; 70:140-148. [DOI: 10.1016/j.jbiomech.2017.10.027] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 10/04/2017] [Accepted: 10/27/2017] [Indexed: 12/13/2022]
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12
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An EMG-assisted modeling approach to assess passive lumbar tissue loading in vivo during trunk bending. J Electromyogr Kinesiol 2017. [PMID: 28633066 DOI: 10.1016/j.jelekin.2017.06.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
Lower back pain (LBP) is a condition with high prevalence and high cost both in the United States and around the world. The magnitude of mechanical loading on spine is strongly associated with the occurrence of LBP. Previously, to assess spinal loading, biologically assisted biomechanical models were developed to estimate trunk muscle contraction forces. Loadings on lumbar passive tissues are estimated using anatomical models. However, despite the substantial individual variability in lumbar ligament geometry and viscoelastic properties, the existing anatomical models do not account for these differences. As such, the accuracy of model prediction is compromised especially when mid to full range of trunk motions are involved. This paper describes a new modeling approach to assess lumbar passive tissue loading with the consideration of individual differences in lumbar passive tissue properties. A data set that has trunk bending data from 13 human participants was analyzed; on average, lumbar passive tissue contributes to ∼89% of the total spinal compression force at fully flexed trunk postures; the estimated spinal tissue loadings were in feasible ranges as reported from previous cadaver studies; the estimated spinal loadings were also mostly in agreement with results from previous in vivo studies.
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Bayoglu R, Geeraedts L, Groenen KH, Verdonschot N, Koopman B, Homminga J. Twente spine model: A complete and coherent dataset for musculo-skeletal modeling of the lumbar region of the human spine. J Biomech 2017; 53:111-119. [DOI: 10.1016/j.jbiomech.2017.01.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 12/08/2016] [Accepted: 01/05/2017] [Indexed: 02/07/2023]
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14
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Bassani T, Ottardi C, Costa F, Brayda-Bruno M, Wilke HJ, Galbusera F. Semiautomated 3D Spine Reconstruction from Biplanar Radiographic Images: Prediction of Intervertebral Loading in Scoliotic Subjects. Front Bioeng Biotechnol 2017; 5:1. [PMID: 28164082 PMCID: PMC5247473 DOI: 10.3389/fbioe.2017.00001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 01/04/2017] [Indexed: 11/13/2022] Open
Abstract
The present study proposes a semiautomatic software approach to reconstruct 3D subject-specific musculoskeletal model of thoracolumbar spine from radiographic digitized images acquired with EOS system. The approach is applied to evaluate the intervertebral loads in 38 standing adolescents with mild idiopathic scoliosis. For each vertebra, a set of landmarks was manually identified on radiographic images. The landmark coordinates were processed to calculate the following vertebral geometrical properties in the 3D space (i) location (ii) dimensions; and (iii) rotations. Spherical joints simulated disks, ligaments, and facet joints. Body weight distribution, muscles forces, and insertion points were placed according to physiological-anatomical values. Inverse static analysis, calculating joints' reactions in maintaining assigned spine configuration, was performed with AnyBody software. Reaction forces were computed to quantify intervertebral loads, and correlation with the patient anatomical parameters was then checked. Preliminary validation was performed comparing the model outcomes with that obtained from other authors in previous modeling works and from in vivo measurements. The comparison with previous modeling works and in vivo studies partially fulfilled the preliminary validation purpose. However, minor incongruities were pointed out that need further investigations. The subjects' intervertebral loads were found significantly correlated with the anatomical parameters in the sagittal and axial planes. Despite preliminary encouraging results that support model suitability, future investigations to consolidate the proposed approach are necessary. Nonetheless, the present method appears to be a promising tool that once fully validated could allow the subject-specific non-invasive evaluation of a deformed spine, providing supplementary information to the routine clinical examination and surgical intervention planning.
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Affiliation(s)
- Tito Bassani
- IRCCS Istituto Ortopedico Galeazzi , Milan , Italy
| | - Claudia Ottardi
- Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering 'Giulio Natta', Politecnico di Milano , Milan , Italy
| | - Francesco Costa
- Department of Neurosurgery, Humanitas Clinical and Research Center , Rozzano , Italy
| | | | - Hans-Joachim Wilke
- Institute of Orthopaedic Research and Biomechanics, Centre for Trauma Research Ulm (ZTF), Ulm University , Ulm , Germany
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15
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Shojaei I, Vazirian M, Salt EG, Van Dillen LR, Bazrgari B. Timing and magnitude of lumbar spine contribution to trunk forward bending and backward return in patients with acute low back pain. J Biomech 2017; 53:71-77. [PMID: 28087062 DOI: 10.1016/j.jbiomech.2016.12.039] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 12/20/2016] [Accepted: 12/25/2016] [Indexed: 11/16/2022]
Abstract
Alterations in the lumbo-pelvic coordination denote changes in neuromuscular control of trunk motion as well as load sharing between passive and active tissues in the lower back. Differences in timing and magnitude aspects of lumbo-pelvic coordination between patients with chronic low back pain (LBP) and asymptomatic individuals have been reported; yet, the literature on lumbo-pelvic coordination in patients with acute LBP is scant. A case-control study was conducted to explore the differences in timing and magnitude aspects of lumbo-pelvic coordination between females with (n=19) and without (n=19) acute LBP. Participants in each group completed one experimental session wherein they performed trunk forward bending and backward return at preferred and fast paces. The amount of lumbar contribution to trunk motion (as the magnitude aspect) as well as the mean absolute relative phase (MARP) and deviation phase (DP) between thoracic and pelvic rotations (as the timing aspect) of lumbo-pelvic coordination were calculated. The lumbar contribution to trunk motion in the 2nd and the 3rd quarters of both forward bending and backward return phases was significantly smaller in the patient than the control group. The MARP and the DP were smaller in the patient vs. the control group during entire motion. The reduced lumbar contribution to trunk motion as well as the more in-phase and less variable lumbo-pelvic coordination in patients with acute LBP compared to the asymptomatic controls is likely the result of a neuromuscular adaptation to reduce painful deformation and to protect injured lower back tissues.
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Affiliation(s)
- Iman Shojaei
- F. Joseph Halcomb III, M.D. Department of Biomedical Engineering, University of Kentucky, Lexington, KY 40506, USA
| | - Milad Vazirian
- F. Joseph Halcomb III, M.D. Department of Biomedical Engineering, University of Kentucky, Lexington, KY 40506, USA
| | - Elizabeth G Salt
- College of Nursing, University of Kentucky, Lexington, KY 40506, USA
| | - Linda R Van Dillen
- Program in Physical Therapy, Department of Orthopedic Surgery, Washington University School of Medicine, St. Louis, MO 63108, USA
| | - Babak Bazrgari
- F. Joseph Halcomb III, M.D. Department of Biomedical Engineering, University of Kentucky, Lexington, KY 40506, USA.
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Senteler M, Weisse B, Rothenfluh DA, Farshad MT, Snedeker JG. Fusion angle affects intervertebral adjacent spinal segment joint forces-Model-based analysis of patient specific alignment. J Orthop Res 2017; 35:131-139. [PMID: 27364167 DOI: 10.1002/jor.23357] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 06/30/2016] [Indexed: 02/04/2023]
Abstract
This study addresses the hypothesis that adjacent segment intervertebral joint loads are sensitive to the degree of lordosis that is surgically imposed during vertebral fusion. Adjacent segment degeneration is often observed after lumbar fusion, but a causative mechanism is not yet clearly evident. Altered kinematics of the adjacent segments and potentially nonphysiological mechanical joint loads have been implicated in this process. However, little is known of how altered alignment and kinematics influence loading of the adjacent intervertebral joints under consideration of active muscle forces. This study investigated these effects by simulating L4/5 fusions using kinematics-driven musculoskeletal models of one generic and eight sagittal alignment-specific models. Models featured different spinopelvic configurations but were normalized by body height, masses, and muscle properties. Fusion of the L4/5 segment was implemented in an in situ (22°), hyperlordotic (32°), and hypolordotic (8°) fashion and kinematic input parameters were changed accordingly based on findings of an in vitro investigation. Bending motion from upright standing to 45° forward flexion and back was simulated for all models in intact and fused conditions. Joint loads at adjacent levels and moment arms of spinal muscles experienced changes after all types of fusion. Hypolordotic configuration led to an increase of adjacent segment (L3/4) shear forces of 29% on average, whereas hyperlordotic fusion reduced shear by 39%. Overall, L4/5 in situ fusion resulted in intervertebral joint forces closest to intact loading conditions. An artificial decrease in lumbar lordosis (minus 14° on average) caused by an L4/5 fusion lead to adverse loading conditions, particularly at the cranial adjacent levels, and altered muscle moment arms, in particular for muscles in the vicinity of the fusion. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:131-139, 2017.
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Affiliation(s)
- Marco Senteler
- Department of Orthopedics, Balgrist, University of Zurich, Lengghalde 5, Zurich 8008, Switzerland.,Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.,Swiss Federal Laboratories for Materials Science and Technology, Zurich, Switzerland
| | - Bernhard Weisse
- Swiss Federal Laboratories for Materials Science and Technology, Zurich, Switzerland
| | - Dominique A Rothenfluh
- Oxford University Hospitals, NHS Trust, Nuffield Orthopaedic Centre, Oxford, United Kingdom
| | - Mazda T Farshad
- Department of Orthopedics, Balgrist, University of Zurich, Lengghalde 5, Zurich 8008, Switzerland
| | - Jess G Snedeker
- Department of Orthopedics, Balgrist, University of Zurich, Lengghalde 5, Zurich 8008, Switzerland.,Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
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Huang YP, Du CF, Cheng CK, Zhong ZC, Chen XW, Wu G, Li ZC, Ye JD, Lin JH, Wang LZ. Preserving Posterior Complex Can Prevent Adjacent Segment Disease following Posterior Lumbar Interbody Fusion Surgeries: A Finite Element Analysis. PLoS One 2016; 11:e0166452. [PMID: 27870867 PMCID: PMC5117648 DOI: 10.1371/journal.pone.0166452] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 10/29/2016] [Indexed: 11/28/2022] Open
Abstract
Objective To investigate the biomechanical effects of the lumbar posterior complex on the adjacent segments after posterior lumbar interbody fusion (PLIF) surgeries. Methods A finite element model of the L1–S1 segment was modified to simulate PLIF with total laminectomy (PLIF-LAM) and PLIF with hemilaminectomy (PLIF-HEMI) procedures. The models were subjected to a 400N follower load with a 7.5-N.m moment of flexion, extension, torsion, and lateral bending. The range of motion (ROM), intradiscal pressure (IDP), and ligament force were compared. Results In Flexion, the ROM, IDP and ligament force of posterior longitudinal ligament, intertransverse ligament, and capsular ligament remarkably increased at the proximal adjacent segment in the PLIF-LAM model, and slightly increased in the PLIF-HEMI model. There was almost no difference for the ROM, IDP and ligament force at L5-S1 level between the two PLIF models although the ligament forces of ligamenta flava remarkably increased compared with the intact lumbar spine (INT) model. For the other loading conditions, these two models almost showed no difference in ROM, IDP and ligament force on the adjacent discs. Conclusions Preserved posterior complex acts as the posterior tension band during PLIF surgery and results in less ROM, IDP and ligament forces on the proximal adjacent segment in flexion. Preserving the posterior complex during decompression can be effective on preventing adjacent segment degeneration (ASD) following PLIF surgeries.
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Affiliation(s)
- Yun-Peng Huang
- Department of Orthopaedics, The First Affiliated Hospital of Fujian Medical University, Fuzhou City, Fujian Province, 350005, China
| | - Cheng-Fei Du
- Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, Tianjin University of Technology, Tianjin, 300384, China
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, International Research Center for Implantable and Interventional Medical Devices, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, China
| | - Cheng-Kung Cheng
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, International Research Center for Implantable and Interventional Medical Devices, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, China
- Orthopaedic Device Research Center, National Yang-Ming University, 11221, Taipei, China
| | - Zheng-Cheng Zhong
- Orthopaedic Device Research Center, National Yang-Ming University, 11221, Taipei, China
| | - Xuan-Wei Chen
- Department of Orthopaedics, The First Affiliated Hospital of Fujian Medical University, Fuzhou City, Fujian Province, 350005, China
| | - Gui Wu
- Department of Orthopaedics, The First Affiliated Hospital of Fujian Medical University, Fuzhou City, Fujian Province, 350005, China
| | - Zhe-Cheng Li
- Department of Orthopaedics, The First Affiliated Hospital of Fujian Medical University, Fuzhou City, Fujian Province, 350005, China
| | - Jin-Duo Ye
- Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, Tianjin University of Technology, Tianjin, 300384, China
| | - Jian-Hua Lin
- Department of Orthopaedics, The First Affiliated Hospital of Fujian Medical University, Fuzhou City, Fujian Province, 350005, China
- * E-mail: (JHL); (LZW)
| | - Li Zhen Wang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, International Research Center for Implantable and Interventional Medical Devices, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, China
- * E-mail: (JHL); (LZW)
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A new method to approximate load–displacement relationships of spinal motion segments for patient-specific multi-body models of scoliotic spine. Med Biol Eng Comput 2016; 55:1039-1050. [DOI: 10.1007/s11517-016-1576-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 09/17/2016] [Indexed: 10/20/2022]
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19
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Ignasiak D, Ferguson SJ, Arjmand N. A rigid thorax assumption affects model loading predictions at the upper but not lower lumbar levels. J Biomech 2016; 49:3074-3078. [DOI: 10.1016/j.jbiomech.2016.07.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 07/03/2016] [Accepted: 07/08/2016] [Indexed: 10/21/2022]
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20
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Finding line of action of the force exerted on erect spine based on lateral bending test in personalization of scoliotic spine models. Med Biol Eng Comput 2016; 55:673-684. [DOI: 10.1007/s11517-016-1550-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 07/11/2016] [Indexed: 12/01/2022]
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21
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Naserkhaki S, Jaremko JL, Adeeb S, El-Rich M. On the load-sharing along the ligamentous lumbosacral spine in flexed and extended postures: Finite element study. J Biomech 2015; 49:974-982. [PMID: 26493346 DOI: 10.1016/j.jbiomech.2015.09.050] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 09/11/2015] [Accepted: 09/27/2015] [Indexed: 10/22/2022]
Abstract
A harmonic synergy between the load-bearing and stabilizing components of the spine is necessary to maintain its normal function. This study aimed to investigate the load-sharing along the ligamentous lumbosacral spine under sagittal loading. A 3D nonlinear detailed Finite Element (FE) model of lumbosacral spine with realistic geometry was developed and validated using wide range of numerical and experimental (in-vivo and in-vitro) data. The model was subjected to 500 N compressive Follower Load (FL) combined with 7.5 Nm flexion (FLX) or extension (EXT) moments. Load-sharing was expressed as percentage of total internal force/moment developed along the spine that each spinal component carried. These internal forces and moments were determined at the discs centres and included the applied load and the resisting forces in the ligaments and facet joints. The contribution of the facet joints and ligaments in supporting bending moments produced additional forces and moments in the discs. The intervertebral discs carried up to 81% and 68% of the total internal force in case of FL combined with FLX and EXT, respectively. The ligaments withstood up to 67% and 81% of the total internal moment in cases of FL combined with EXT and FLX, respectively. Contribution of the facet joints in resisting internal force and moment was noticeable at levels L4-S1 only particularly in case of FL combined with EXT and reached up 29% and 52% of the internal moment and force, respectively. This study demonstrated that spinal load-sharing depended on applied load and varied along the spine.
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Affiliation(s)
- Sadegh Naserkhaki
- Department of Civil and Environmental Engineering, University of Alberta, Canada
| | - Jacob L Jaremko
- Department of Radiology and Diagnostic Imaging, University of Alberta, Canada
| | - Samer Adeeb
- Department of Civil and Environmental Engineering, University of Alberta, Canada
| | - Marwan El-Rich
- Department of Civil and Environmental Engineering, University of Alberta, Canada.
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Passive lumbar tissue loading during trunk bending at three speeds: An in vivo study. Clin Biomech (Bristol, Avon) 2015; 30:726-31. [PMID: 25979223 DOI: 10.1016/j.clinbiomech.2015.04.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 03/19/2015] [Accepted: 04/28/2015] [Indexed: 02/07/2023]
Abstract
BACKGROUND Low back disorders are closely related with the magnitude of mechanical loading on human spine. However, spinal loading contributed by the lumbar passive tissues is still not well understood. In this study, the effect of motion speed on lumbar passive moment output was investigated. In addition, the increase of lumbar passive moment during trunk bending was modeled. METHODS Twelve volunteers performed trunk-bending motions at three different speeds. Trunk kinematics and muscle activities were collected and used to estimate instantaneous spinal loading and the corresponding lumbar passive moment. The lumbar passive moments at different ranges of trunk motion were compared at different speed levels and the relationship between lumbar passive moment lumbar flexion was modeled. FINDINGS A non-linear, two-stage pattern of increase in lumbar passive moment was evident during trunk flexion. However, the effect of motion speed was not significant on lumbar passive moments or any of the model parameters. INTERPRETATION As reported previously, distinct lumbar ligaments may begin to generate tension at differing extents of trunk flexion, and this could be the cause of the observed two-stage increasing pattern of lumbar passive moment. The current results also suggest that changes in tissue strain rate may not have a significant impact on the total passive moment output at the relatively slow trunk motions examined here.
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Senteler M, Weisse B, Rothenfluh DA, Snedeker JG. Intervertebral reaction force prediction using an enhanced assembly of OpenSim models. Comput Methods Biomech Biomed Engin 2015; 19:538-48. [DOI: 10.1080/10255842.2015.1043906] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Abouhossein A, Weisse B, Ferguson SJ. Quantifying the centre of rotation pattern in a multi-body model of the lumbar spine. Comput Methods Biomech Biomed Engin 2013; 16:1362-73. [DOI: 10.1080/10255842.2012.671306] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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25
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Aiyangar AK, Zheng L, Tashman S, Anderst WJ, Zhang X. Capturing Three-Dimensional In Vivo Lumbar Intervertebral Joint Kinematics Using Dynamic Stereo-X-Ray Imaging. J Biomech Eng 2013; 136:011004. [DOI: 10.1115/1.4025793] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Indexed: 11/08/2022]
Abstract
Availability of accurate three-dimensional (3D) kinematics of lumbar vertebrae is necessary to understand normal and pathological biomechanics of the lumbar spine. Due to the technical challenges of imaging the lumbar spine motion in vivo, it has been difficult to obtain comprehensive, 3D lumbar kinematics during dynamic functional tasks. The present study demonstrates a recently developed technique to acquire true 3D lumbar vertebral kinematics, in vivo, during a functional load-lifting task. The technique uses a high-speed dynamic stereo-radiography (DSX) system coupled with a volumetric model-based bone tracking procedure. Eight asymptomatic male participants performed weight-lifting tasks, while dynamic X-ray images of their lumbar spines were acquired at 30 fps. A custom-designed radiation attenuator reduced the radiation white-out effect and enhanced the image quality. High resolution CT scans of participants' lumbar spines were obtained to create 3D bone models, which were used to track the X-ray images via a volumetric bone tracking procedure. Continuous 3D intervertebral kinematics from the second lumbar vertebra (L2) to the sacrum (S1) were derived. Results revealed motions occurring simultaneously in all the segments. Differences in contributions to overall lumbar motion from individual segments, particularly L2–L3, L3–L4, and L4–L5, were not statistically significant. However, a reduced contribution from the L5–S1 segment was observed. Segmental extension was nominally linear in the middle range (20%–80%) of motion during the lifting task, but exhibited nonlinear behavior at the beginning and end of the motion. L5–S1 extension exhibited the greatest nonlinearity and variability across participants. Substantial AP translations occurred in all segments (5.0 ± 0.3 mm) and exhibited more scatter and deviation from a nominally linear path compared to segmental extension. Maximum out-of-plane rotations (<1.91 deg) and translations (<0.94 mm) were small compared to the dominant motion in the sagittal plane. The demonstrated success in capturing continuous 3D in vivo lumbar intervertebral kinematics during functional tasks affords the possibility to create a baseline data set for evaluating the lumbar spinal function. The technique can be used to address the gaps in knowledge of lumbar kinematics, to improve the accuracy of the kinematic input into biomechanical models, and to support development of new disk replacement designs more closely replicating the natural lumbar biomechanics.
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Affiliation(s)
- Ameet K. Aiyangar
- EMPA (Swiss Federal Laboratories for Materials Science and Research), Mechanical Systems Engineering (Lab 304), Ueberlandstrasse 129, Duebendorf 8400, Switzerland
- Department of Orthopaedic Surgery, University of Pittsburgh, 3820 South Water Street, Pittsburgh, PA 15203 e-mail:
| | - Liying Zheng
- Department of Orthopaedic Surgery, Musculoskeletal Modeling Laboratory, University of Pittsburgh, 3820 South Water Street, Pittsburgh, PA 15203 e-mail:
| | - Scott Tashman
- Department of Orthopaedic Surgery, Department of Bioengineering, Orthopaedic Biodynamics Laboratory, University of Pittsburgh, 3820 South Water Street, Pittsburgh, PA 15203 e-mail:
| | - William J. Anderst
- Department of Orthopaedic Surgery, Orthopaedic Biodynamics Laboratory, University of Pittsburgh, 3820 South Water Street, Pittsburgh, PA 15203 e-mail:
| | - Xudong Zhang
- Department of Orthopaedic Surgery, Department of Bioengineering, Department of Mechanical Engineering and Materials Science, Musculoskeletal Modeling Laboratory, University of Pittsburgh, 3820 South Water Street, Pittsburgh, PA 15203 e-mail:
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Computational Biomechanical Modeling of Scoliotic Spine: Challenges and Opportunities. Spine Deform 2013; 1:401-411. [PMID: 27927365 DOI: 10.1016/j.jspd.2013.07.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 07/24/2013] [Indexed: 11/21/2022]
Abstract
BACKGROUND Biomechanical computer models of the spine have important roles in the treatment and correction of scoliosis by providing predictive information for surgeons and other clinicians. OBJECTIVES This article reviews computational models of intact and scoliotic spine and its components; vertebra, intervertebral disc, ligament, facet joints, and muscle. Several spine models, developed using multi-body modelling and finite element modelling schemes, and their pros and cons are discussed. CONCLUSIONS The review reveals that scoliosis modelling is performed for 3 main applications: 1) brace simulation; 2) analysis of surgical correction technique; and 3) patient positioning before surgical instrumentation. The models provide predictive information for a priori choice of brace configurations and mechanically effective surgical correction techniques and the expected degree of correction. However, they have many shortcomings: for instance, they do not fully reproduce the active behaviour of the spine and the models' properties are not personalized.
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Han KS, Rohlmann A, Zander T, Taylor WR. Lumbar spinal loads vary with body height and weight. Med Eng Phys 2013; 35:969-77. [DOI: 10.1016/j.medengphy.2012.09.009] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 08/24/2012] [Accepted: 09/13/2012] [Indexed: 11/25/2022]
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Neidlinger-Wilke C, Galbusera F, Pratsinis H, Mavrogonatou E, Mietsch A, Kletsas D, Wilke HJ. Mechanical loading of the intervertebral disc: from the macroscopic to the cellular level. 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; 23 Suppl 3:S333-43. [DOI: 10.1007/s00586-013-2855-9] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 05/10/2013] [Accepted: 06/03/2013] [Indexed: 12/24/2022]
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Aspden RM. Letters to the Editor. Comput Methods Biomech Biomed Engin 2012; 15:1011-2; author reply 1013-4. [DOI: 10.1080/10255842.2011.566417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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30
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An enhanced and validated generic thoraco-lumbar spine model for prediction of muscle forces. Med Eng Phys 2012; 34:709-16. [DOI: 10.1016/j.medengphy.2011.09.014] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 07/08/2011] [Accepted: 09/04/2011] [Indexed: 11/23/2022]
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