Search for: lumbar-spines
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    Muscle force evaluation and the role of posture in human lumbar spine under compression

    , Article European Spine Journal ; Volume 11, Issue 6 , 2002 , Pages 519-526 ; 09406719 (ISSN) Shirazi Adl, A ; Sadouk, S ; Parnianpour, M ; Pop, D ; El-Rich, M ; Sharif University of Technology
    Using two nonlinear finite element models of the lumbar spine, the concept of optimal posture is explored by minimizing the segmental sagittal moments required for the equilibrium of the passive lumbar spine under a total of 2800 N axial compression while varying the pelvic tilt and lumbar lordosis. The redundant active-passive system is subsequently solved for this posture using a novel kinematics-based muscle calculation algorithm along with minimization approach. Some flattening in the lumbar spine substantially reduces the required moments and internal passive shear forces under 2800 N axial compression force. Small muscle forces are calculated for this optimal posture. The role of... 

    Effect of considering stability requirements on antagonistic muscle activities using a musculoskeletal model of the human lumbar spine

    , Article 2013 20th Iranian Conference on Biomedical Engineering, ICBME 2013 ; 2013 , Pages 260-264 Hajihoseinali, M ; Nickpour, H ; Arjmand, N ; Farahmand, F ; Sharif University of Technology
    The recruitment pattern of trunk muscles is determined using a three-dimensional model of the spine with two joints and six symmetric pairs of muscles in which both equilibrium and stability requirements are satisfied. Model predictions are verified using Anybody Modeling System (AMS) and Abaqus. The model is used to test the hypothesis that antagonistic muscle activities are necessary for the spinal stability. The model with stability constraints predicts muscle activities greater than those predicted without stability consideration. In agreement with experimental data, the stability-based model predicts antagonistic muscle activities. It is shown that spinal stability increases with trunk... 

    Can simple trunk muscle models balance and stabilize lumbar spine during support of symmetric and asymmetric loads? a FE model study

    , Article 2007 ASME Summer Bioengineering Conference, SBC 2007, Keystone, CO, 20 June 2007 through 24 June 2007 ; 2007 , Pages 443-444 ; 0791847985 (ISBN); 9780791847985 (ISBN) Kiapour, A ; Shirazi Adl, A ; Parnianpour, M ; Sharif University of Technology

    Control of different FEM based musculoskeletal models of human lumbar spine under different loading conditions using optimization method

    , Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) Kiapour, A ; Parnianpour, M ; Shirazi Adl, A ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    In this study the effects of using different musculoskeletal models on load-displacement behavior of FE models of the human lumbar spine under external loads and moments have been analyzed in terms of equilibrium and clinical stability. A simplified and a complex architecture of muscles have been integrated to FE based models of lumbar spine and were loaded to simulate the load carrying behavior of human lumbar spine in flexion, extension and lateral bending. The displacement values as well as muscle forces have been computed and compared in both cases using optimization methods with different cost functions. The models showed similar kinematics in pure flexion but the simplified model... 

    Design of a Novel Loading Mechanism for in Vitro Spine Testing

    , M.Sc. Thesis Sharif University of Technology Sharif, Mohammad Reza (Author) ; Parnianpour, Mohamad (Supervisor) ; Narimani, Roya (Co-Advisor)
    In this project, we use a novel mechanism to control the lumbar rotational profile and also the disc pressure of L3/L4 and L4/L5. Spine, as one of the most important parts of human musculoskeletal system, helps human beings to walk on two feet without much energy consumption. Any problem in this part may cause moving disorders or pain. To heal severe spine disorders, many different methods like surgery and implantation are adopted. To be sure of proper functionality in the human body, these methods should be tested clinically in advance. Cadaver spine testing in vitro, is accepted as a gold standard to evaluate new methods. One of the main challenges facing spine in vitro tests is how to... 

    Evaluation of Trunk Movement System Strategies through the Concept of Muscle Synergies

    , M.Sc. Thesis Sharif University of Technology Bagheri Rouchi, Mahdi (Author) ; Firoozbakhsh, Keikhosrow (Supervisor) ; Parnianpour, Mohammad (Co-Advisor)
    In this study, by dividing spine motion in two part, ordinary movement and initial-final accelerated movement, the commands of CNS are evaluated by optimization methods to find synchronous and time varying synergies. Spine, which is a complex structure of vertebrae and cartilage, has been modeled by a 3D inverted pendulum with a ball and socket joint at L4/L5 incorporated with 18 muscle fascicles. Planning of point-to-point spine motion is performed by optimal control method in combined with cost function of kinematics and kinetic features that available in spine structure. In the second step, coactivation of muscles is predicted by utilizing static optimization along with stability... 

    Effect of Lumbar Spine Lordosis on Intervertebral Joint Load Sharing Using Musculoskeletal and Finite Element Modeling

    , M.Sc. Thesis Sharif University of Technology Havashinezhadian, Sara (Author) ; Arjmand, Navid (Supervisor)
    There is a large, at times contradictory body of investigations relating low back pain and spinal curvature in sagittal plane. The previous studies have not been subject-specified, and they have not considered the active tissues in the models. The mechanical load has a significant impact on the prevalence of low back pain and the geometry of lumbar spine in the sagittal plane is one of the most important characteristics in determining the load sharing of the spine. Thus, it is essential to know how the geometry load affects the load sharing of the lumbar spine. As a matter of fact, the purpose of this project is to know how the geometry of the lumbar spine affects the load sharing. Thus,... 

    A Detailed Finite Element Model of the Lumbar Spine under Muscle Forces

    , M.Sc. Thesis Sharif University of Technology Asadi, Hamed (Author) ; Arjmand, Navid (Supervisor)
    Etiological studies proves the fact that Low Back Pain (LBP) is one of the most expensive and prevalent desease all over the world. This fact illustrates the reqiurment of the special effort in ordet to reducing the pain due to this problem. Finite element modeling of human spine is one the suitable methods to simulate the behavior of human spine in different loading conditions. These conditions could be different daily occupational tasks. There is two general viewpoint toward finite element modeling of human spine. The fisrt method focuses on the detailed geometry and mechanical properties of spine, while the other complexities such as detailed muscle forces are overlooked. The latter... 

    Effect of Iatrogenic Muscle Injuries on Spine Biomechanics During Posterior Lumbar Surgeries Using a Biomechanical Model for Design of Rehabilitation Exercises

    , M.Sc. Thesis Sharif University of Technology Jamshidnezhad, Saman (Author) ; Arjmand, Navid (Supervisor)
    Posterior lumbar surgery is often associated with extensive injuries to back muscles. In this thesis, the effect of such iatrogenic injuries in some patients was examined. For this purpose, the CSA of back muscles in 6 patients were measured using MR scan. To examine any natural change in CSAs of healthy people or instrument errors, same measurement were carried out on 10 healthy volunteers. In addition, a detailed anatomical model of an intact human spine was developed. With the aim of experimental studies and intact model, the post-operative model of patients was also developed. These two models were used to quantizing the change in activity of back muscles during some symmetric, normal... 

    Developing a Biomechanical Model of Lumbar Spine in Order to Evaluating the Behavior of Spine under Physiological and in Vitro Loading Conditions

    , M.Sc. Thesis Sharif University of Technology Borghei Nejad, Mustafa (Author) ; Firozbakhsh, Keikhosrow (Supervisor) ; Parnianpour, Mohammad (Co-Advisor)
    In present study we are going to introduce a biomechanical model of lumbar spine with using finite element method and use it for evaluating the behavior of spine under different loading conditions.Spine as the main part of muskloskeletal system of human body is tolerating various forces during daily activities.So it's important to know about different approaches for studing the loading conditions wich is using for evaluating the behavior of lumbar implants. In other words in order to obtain correct outputs we need to simulate the real condition in the experiments. We can use biomechanical models in order to comparison the different approaches  

    An optimization-based method for prediction of lumbar spine segmental kinematics from the measurements of thorax and pelvic kinematics

    , Article International Journal for Numerical Methods in Biomedical Engineering ; July , 2015 , Volume 31, Issue 12 ; 20407939 (ISSN) Shojaei, I ; Arjmand, N ; Bazrgari, B ; Sharif University of Technology
    Wiley-Blackwell  2015
    Given measurement difficulties, earlier modeling studies have often used some constant ratios to predict lumbar segmental kinematics from measurements of total lumbar kinematics. Recent imaging studies suggested distribution of lumbar kinematics across its vertebrae changes with trunk rotation, lumbar posture, and presence of load. An optimization-based method is presented and validated in this study to predict segmental kinematics from measured total lumbar kinematics. Specifically, a kinematics-driven biomechanical model of the spine is used in a heuristic optimization procedure to obtain a set of segmental kinematics that, when prescribed to the model, were associated with the minimum... 

    A rigid thorax assumption affects model loading predictions at the upper but not lower lumbar levels

    , Article Journal of Biomechanics ; Volume 49, Issue 13 , 2016 , Pages 3074-3078 ; 00219290 (ISSN) Ignasiak, D ; Ferguson, S. J ; Arjmand, N ; Sharif University of Technology
    Elsevier Ltd 
    A number of musculoskeletal models of the human spine have been used for predictions of lumbar and muscle forces. However, the predictive power of these models might be limited by a commonly made assumption; thoracic region is represented as a single lumped rigid body. This study hence aims to investigate the impact of such assumption on the predictions of spinal and muscle forces. A validated thoracolumbar spine model was used with a flexible thorax (T1–T12), a completely rigid one or rigid with thoracic posture updated at each analysis step. The simulations of isometric forward flexion up to 80°, with and without a 20 kg hand load, were performed, based on the previously measured... 

    Investigation on a developed wearable assistive device (WAD) in reduction lumbar muscles activity

    , Article Biomedical Engineering - Applications, Basis and Communications ; Volume 25, Issue 3 , 2013 ; 10162372 (ISSN) Heydari, H ; Hoviattalab, M ; Azghani, M. R ; Ramezanzadehkoldeh, M ; Parnianpour, M ; Sharif University of Technology
    A new wearable assistive device (WAD) was developed to decrease required force on the lumbar spine in static holding tasks. In order to obtain moments on lumbar spine in two conditions, with and without WAD, a biomechanical static model was used for estimation of external moments on lumbar spine. The results of biomechanical models indicated that there was a reduction in the lumbar moment ranging from 20% to 43% using WAD depending on the load and flexion angle. A total of 15 male healthy subjects were tested to experimentally verify the predicted reduction of external moments on the spine by wearing WAD. Normalized electromyography (EMG) of the right and left lumbar and thoracic erector... 

    How does the central nervous system address the kinetic redundancy in the lumbar spine? Three-dimensional isometric exertions with 18 Hill-model-based muscle fascicles at the L4-L5 level

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 224, Issue 3 , 2010 , Pages 487-501 ; 09544119 (ISSN) Rashedi, E ; Khalaf, K ; Nassajian, M. R ; Nasseroleslami, B ; Parnianpour, M ; Sharif University of Technology
    The human motor system is organized for execution of various motor tasks in a different and flexible manner. The kinetic redundancy in the human musculoskeletal system is a significant property by which the central nervous system achieves many complementary goals. An equilibrium-based biomechanical model of isometric three-dimensional exertions of trunk muscles has been developed. Following the definition and role of the uncontrolled manifold, the kinetic redundancy concept is explored in mathematical terms. The null space of the kinetically redundant system when a certain joint moment and/or stiffness are needed is derived and discussed. The aforementioned concepts have been illustrated,... 

    Role of Intra-Abdominal Pressure and Abdominal Muscle Activities on Spinal Stability and Spinal Loads

    , M.Sc. Thesis Sharif University of Technology Farahmand, Masoud (Author) ; ParnianPour, Mohamad (Supervisor) ; Firoozbakhsh, Keikhosrow (Co-Advisor)
    Spine is one of the most important musculoskeletal systems of the human body. Any problem which is related to this part of human body causes pain and disability. Spinal compression forces are one of the main reasons of this disability and pain. It is assumed that intra-abdominal pressure causes spinal unloading in lifting. Studies usually don’t consider the role of intra-abdominal pressure and introduce it as an effective parameter which can increases spinal stability and influences spinal mechanics.Generation mechanism of intra-abdominal pressure remain enigmatic, studies that advocate the unloading effect of IAP usually consider a raise in IAP to be primarily due to the activity of... 

    A Comparative Study between Available Lifting Tools for Assessment of Risk of Back Injuries

    , M.Sc. Thesis Sharif University of Technology Rajaee, Mohamad Ali (Author) ; Arjmand, Navid (Supervisor)
    Epidemiological studies have identified manual material handling and lifting as risk factors in occupational low back pain (LBP). There are many lifting analysis tools to estimate the risk of injury during a specific lifting task. One for using these tools, needs to know the limitations of each tool and be noticed where a tool cannot be used. The purpose of this study is to compare different biomechanical models of lumbar spine and find out their characteristics.Five models are chosen for this study which are: the University of Michigan’s Static Strength Prediction Program ( ) software, the revised Hand-Calculation Back Compressive Force (HCBCF) equation, the simple polynomial equation of... 

    Real-time Tracking of the Lumbar Spine with Surgical Navigation System and Biomechanical Modeling

    , M.Sc. Thesis Sharif University of Technology Sarrami, Saman (Author) ; Behzadipour, Saeed (Supervisor) ; Farahmand, Farzam (Co-Advisor)
    One of the most important parts of the human’s body is spine. Its anatomy is very complex and has many degrees off freedom. Many kinds of diseases might occur for this part. One of the ways of treatment for this part is surgery that it has different types. In the past decades the surgeries have been done very simple without the help of computers or robots. In other words the surgeon did the surgery with no use of lateral tools. For this reason the error in those surgeries was high. Doing a surgery on the spine level needs a special attention. As the technology improved very much in the last 2 decades the amount of errors has been reduced and various kinds of techniques came in the scene to... 

    Investigation of trunk muscle activities during lifting using a multi-objective optimization-based model and intelligent optimization algorithms

    , Article Medical and Biological Engineering and Computing ; Volume 54, Issue 2-3 , 2016 , Pages 431-440 ; 01400118 (ISSN) Ghiasi, M. S ; Arjmand, N ; Boroushaki, M ; Farahmand, F ; Sharif University of Technology
    Springer Verlag  2016
    A six-degree-of-freedom musculoskeletal model of the lumbar spine was developed to predict the activity of trunk muscles during light, moderate and heavy lifting tasks in standing posture. The model was formulated into a multi-objective optimization problem, minimizing the sum of the cubed muscle stresses and maximizing the spinal stability index. Two intelligent optimization algorithms, i.e., the vector evaluated particle swarm optimization (VEPSO) and nondominated sorting genetic algorithm (NSGA), were employed to solve the optimization problem. The optimal solution for each task was then found in the way that the corresponding in vivo intradiscal pressure could be reproduced. Results... 

    Modeling and validation of a detailed FE viscoelastic lumbar spine model for vehicle occupant dummies

    , Article Computers in Biology and Medicine ; Volume 99 , 2018 , Pages 191-200 ; 00104825 (ISSN) Amiri, S ; Naserkhaki, S ; Parnianpour, M ; Sharif University of Technology
    Elsevier Ltd  2018
    The dummies currently used for predicting vehicle occupant response during frontal crashes or whole-body vibration provide insufficient information about spinal loads. Although they aptly approximate upper-body rotations in different loading scenarios, they overlook spinal loads, which are crucial to injury assessment. This paper aims to develop a modified dummy finite element (FE) model with a detailed viscoelastic lumbar spine. This model has been developed and validated against in-vitro and in-silico data under different loading conditions, and its predicted ranges of motion (RoM) and intradiscal pressure (IDP) maintain close correspondence with the in-vitro data. The dominant frequency... 

    A comprehensive approach for the validation of lumbar spine finite element models investigating post-fusion adjacent segment effects

    , Article Journal of Biomechanics ; Volume 121 , 2021 ; 00219290 (ISSN) Azadi, A ; Arjmand, N ; Sharif University of Technology
    Elsevier Ltd  2021
    Spinal fusion surgery is usually followed by accelerated degenerative changes in the unfused segments above and below the treated segment(s), i.e., adjacent segment disease (ASD). While a number of risk factors for ASD have been suggested, its exact pathogenesis remains to be identified. Finite element (FE) models are indispensable tools to investigate mechanical effects of fusion surgeries on post-fusion changes in the adjacent segment kinematics and kinetics. Existing modeling studies validate only their intact FE model against in vitro data and subsequently simulate post-fusion in vivo conditions. The present study provides a novel approach for the comprehensive validation of a lumbar...