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Total 62 records

    Subject-specific loads on the lumbar spine in detailed finite element models scaled geometrically and kinematic-driven by radiography images

    , Article International Journal for Numerical Methods in Biomedical Engineering ; Volume 35, Issue 4 , 2019 ; 20407939 (ISSN) Dehghan Hamani, I ; Arjmand, N ; Shirazi Adl, A ; Sharif University of Technology
    Wiley-Blackwell  2019
    Abstract
    Traditional load-control musculoskeletal and finite element (FE) models of the spine fail to accurately predict in vivo intervertebral joint loads due mainly to the simplifications and assumptions when estimating redundant trunk muscle forces. An alternative powerful protocol that bypasses the calculation of muscle forces is to drive the detailed FE models by image-based in vivo displacements. Development of subject-specific models, however, both involves the risk of extensive radiation exposures while imaging in supine and upright postures and is time consuming in terms of the reconstruction of the vertebrae, discs, ligaments, and facets geometries. This study therefore aimed to introduce a... 

    Rigid-bar loading on pregnant uterus and development of pregnant abdominal response corridor based on finite element biomechanical model

    , Article International Journal for Numerical Methods in Biomedical Engineering ; Volume 36, Issue 1 , January , 2020 Irannejad Parizi, M ; Ahmadian, M. T ; Mohammadi, H ; Sharif University of Technology
    Wiley-Blackwell  2020
    Abstract
    During pregnancy, traumas can threaten maternal and fetal health. Various trauma effects on a pregnant uterus are little investigated. In the present study, a finite element model of a uterus along with a fetus, placenta, amniotic fluid, and two most effective ligament sets is developed. This model allows numerical evaluation of various loading on a pregnant uterus. The model geometry is developed based on CT-scan data and validated using anthropometric data. Applying Ogden hyper-elastic theory, material properties of uterine wall and placenta are developed. After simulating the “rigid-bar” abdominal loading, the impact force and abdominal penetration are investigated. Findings are compared... 

    Improvement of upper limb motor control and function after competitive and noncompetitive volleyball exercises in chronic stroke survivors: a randomized clinical trial

    , Article Archives of Physical Medicine and Rehabilitation ; Volume 100, Issue 3 , 2019 , Pages 401-411 ; 00039993 (ISSN) Mandehgary Najafabadi, M ; Azad, A ; Mehdizadeh, H ; Behzadipour, S ; Fakhar, M ; Taghavi Azar Sharabiani, P ; Parnianpour, M ; Taghizadeh, G ; Khalaf, K ; Sharif University of Technology
    W.B. Saunders  2019
    Abstract
    Objectives: To investigate the effects of competitive and noncompetitive volleyball exercises on the functional performance and motor control of the upper limbs in chronic stroke survivors. Design: Randomized clinical trial. Setting: Outpatient rehabilitation center. Participants: Chronic stroke survivors (N=48). Interventions: Participants were randomly assigned to competitive (n=16) or noncompetitive (n=16) volleyball exercise groups (60min/d volleyball exercise+30min/d traditional rehabilitation, 3d/wk for 7wk) and control group (n=16). Main Outcome Measures: Reach and grasp motor control measures were evaluated through kinematic analysis. Functional outcomes were assessed via Motor... 

    Role and significance of trunk and upper extremity muscles in walker-assisted paraplegic gait: a case study

    , Article Topics in Spinal Cord Injury Rehabilitation ; Volume 24, Issue 1 , 2018 , Pages 18-27 ; 10820744 (ISSN) Baniasad, M ; Farahmand, F ; Arazpour, M ; Zohoor, H ; Sharif University of Technology
    Thomas Land Publishers Inc  2018
    Abstract
    Background and Purpose: Understanding the role and significance of trunk and upper extremity muscles in paraplegic gait can help in designing more effective assistive devices for these patients and also provides valuable information for improving muscle strengthening programs. Methods: In a patient with a spinal cord injury (SCI) who could walk independently (rating scale of ambulatory capacity, 9) with the aid of bilateral ankle-foot orthosis and a walker, the kinematics, kinetics and electromyographic (EMG) activities of 16 muscles from the trunk and upper and lower extremities were recorded during gait. The onset, cessation, and duration of the EMG signal were associated with the 4 phases... 

    Effect of intervertebral translational flexibilities on estimations of trunk muscle forces, kinematics, loads, and stability

    , Article Computer Methods in Biomechanics and Biomedical Engineering ; Volume 18, Issue 16 , Sep , 2015 , Pages 1760-1767 ; 10255842 (ISSN) Ghezelbash, F ; Arjmand, N ; Shirazi Adl, A ; Sharif University of Technology
    Taylor and Francis Ltd  2015
    Abstract
    Due to the complexity of the human spinal motion segments, the intervertebral joints are often simulated in the musculoskeletal trunk models as pivots thus allowing no translational degrees of freedom (DOFs). This work aims to investigate, for the first time, the effect of such widely used assumption on trunk muscle forces, spinal loads, kinematics, and stability during a number of static activities. To address this, the shear deformable beam elements used in our nonlinear finite element (OFE) musculoskeletal model of the trunk were either substantially stiffened in translational directions (SFE model) or replaced by hinge joints interconnected through rotational springs (HFE model). Results... 

    Design, construction, and evaluation of “sensor lock”: an electromechanical stance control knee joint

    , Article Disability and Rehabilitation: Assistive Technology ; Volume 13, Issue 3 , 2018 , Pages 226-233 ; 17483107 (ISSN) Arazpour, M ; Ahmadi Bani, M ; Baniasad, M ; Samadian, M ; Golchin, N ; Sharif University of Technology
    Taylor and Francis Ltd  2018
    Abstract
    Background and aim: Most currently-available stance control knee ankle foot orthoses (SCKAFOs) still need full knee extension to lock the knee joint, and they are still noisy, bulky, and heavy. Therefore, the aim of this study was to design, construct, and evaluate an original electromechanical SCKAFO knee joint that could feasibly solve these problems, and thus address the problems of current stance control knee joints with regards to their structure, function, cosmesis, and cost. Method: Ten able-bodied (AB) participants and two (knee ankle foot orthosis) KAFO users were recruited to participate in the study. A custom SCKAFO with the same set of components was constructed for each... 

    Nanomechanical properties of MscL α helices: A steered molecular dynamics study

    , Article Channels ; Volume 11, Issue 3 , 2017 , Pages 209-223 ; 19336950 (ISSN) Bavi, N ; Bavi, O ; Vossoughi, M ; Naghdabadi, R ; Hill, A. P ; Martinac, B ; Jamali, Y ; Sharif University of Technology
    Taylor and Francis Inc  2017
    Abstract
    Gating of mechanosensitive (MS) channels is driven by a hierarchical cascade of movements and deformations of transmembrane helices in response to bilayer tension. Determining the intrinsic mechanical properties of the individual transmembrane helices is therefore central to understanding the intricacies of the gating mechanism of MS channels. We used a constant-force steered molecular dynamics (SMD) approach to perform unidirectional pulling tests on all the helices of MscL in M. tuberculosis and E. coli homologs. Using this method, we could overcome the issues encountered with the commonly used constant-velocity SMD simulations, such as low mechanical stability of the helix during... 

    A study of hyperelastic models for predicting the mechanical behavior of extensor apparatus

    , Article Biomechanics and Modeling in Mechanobiology ; Volume 16, Issue 3 , 2017 , Pages 1077-1093 ; 16177959 (ISSN) Elyasi, N ; Karimi Taheri, K ; Narooei, K ; Karimi Taheri, A ; Sharif University of Technology
    Springer Verlag  2017
    Abstract
    In this research, the nonlinear elastic behavior of human extensor apparatus was investigated. To this goal, firstly the best material parameters of hyperelastic strain energy density functions consisting of the Mooney–Rivlin, Ogden, invariants, and general exponential models were derived for the simple tension experimental data. Due to the significance of stress response in other deformation modes of nonlinear models, the calculated parameters were used to study the pure shear and balance biaxial tension behavior of the extensor apparatus. The results indicated that the Mooney–Rivlin model predicts an unstable behavior in the balance biaxial deformation of the extensor apparatus, while the... 

    Adjacent segments biomechanics following lumbar fusion surgery: a musculoskeletal finite element model study

    , Article European Spine Journal ; Volume 31, Issue 7 , 2022 , Pages 1630-1639 ; 09406719 (ISSN) Ebrahimkhani, M ; Arjmand, N ; Shirazi-Adl, A ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2022
    Abstract
    Purpose: This study exploits a novel musculoskeletal finite element (MS-FE) spine model to evaluate the post-fusion (L4–L5) alterations in adjacent segment kinetics. Methods: Unlike the existing MS models with idealized representation of spinal joints, this model predicts stress/strain distributions in all passive tissues while organically coupled to a MS model. This generic (in terms of musculature and material properties) model uses population-based in vivo vertebral sagittal rotations, gravity loads, and an optimization algorithm to calculate muscle forces. Simulations represent individuals with an intact L4–L5, a preoperative severely degenerated L4–L5 (by reducing the disc height by ~... 

    A three-dimensional statistical volume element for histology informed micromechanical modeling of brain white matter

    , Article Annals of Biomedical Engineering ; Volume 48, Issue 4 , 2020 , Pages 1337-1353 Hoursan, H ; Farahmand, F ; Ahmadian, M. T ; Sharif University of Technology
    Springer  2020
    Abstract
    This study presents a novel statistical volume element (SVE) for micromechanical modeling of the white matter structures, with histology-informed randomized distribution of axonal tracts within the extracellular matrix. The model was constructed based on the probability distribution functions obtained from the results of diffusion tensor imaging as well as the histological observations of scanning electron micrograph, at two structures of white matter susceptible to traumatic brain injury, i.e. corpus callosum and corona radiata. A simplistic representative volume element (RVE) with symmetrical arrangement of fully alligned axonal fibers was also created as a reference for comparison. A... 

    A regenerative approach towards recovering the mechanical properties of degenerated intervertebral discs: Genipin and platelet-rich plasma therapies

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 231, Issue 2 , 2017 , Pages 127-137 ; 09544119 (ISSN) Nikkhoo, M ; Wang, J. L ; Abdollahi, M ; Hsu, Y. C ; Parnianpour, M ; Khalaf, K ; Sharif University of Technology
    SAGE Publications Ltd  2017
    Abstract
    Degenerative disc disease, associated with discrete structural changes in the peripheral annulus and vertebral endplate, is one of the most common pathological triggers of acute and chronic low back pain, significantly depreciating an individual's quality of life and instigating huge socioeconomic costs. Novel emerging therapeutic techniques are hence of great interest to both research and clinical communities alike. Exogenous crosslinking, such as Genipin, and platelet-rich plasma therapies have been recently demonstrated encouraging results for the repair and regeneration of degenerated discs, but there remains a knowledge gap regarding the quantitative degree of effectiveness and... 

    Biomechanical simulation of eye-airbag impacts during vehicle accidents

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 232, Issue 7 , 2018 , Pages 699-707 ; 09544119 (ISSN) Shirzadi, H ; Zohoor, H ; Naserkhaki, S ; Sharif University of Technology
    SAGE Publications Ltd  2018
    Abstract
    Airbags are safety devices in vehicles effectively suppressing passengers’ injuries during accidents. Although there are still many cases of eye injuries reported due to eye-airbag impacts in recent years. Biomechanical approaches are now feasible and can considerably help experts to investigate the issue without ethical concerns. The eye-airbag impact–induced stresses/strains in various components of the eye were found to investigate the risk of injury in different conditions (impact velocity and airbag pressure). Three-dimensional geometry of the eyeball, fat and bony socket as well as the airbag were developed and meshed to develop a finite element model. Nonlinear material properties of... 

    Effects of plate contouring quality on the biomechanical performance of high tibial osteotomy fixation: A parametric finite element study

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 236, Issue 3 , 2022 , Pages 356-366 ; 09544119 (ISSN) Hayatbakhsh, Z ; Farahmand, F ; Sharif University of Technology
    SAGE Publications Ltd  2022
    Abstract
    Locking plates have threaded holes, in which threaded-head screws are affixed. Hence, they do not need to be in intimate contact with underlying bone to provide fixation. There are, however, reports that a large distance between the plate and the bone might cause clinical complications such as delayed union or nonunion, screw pull out, and screw and plate breakage. Considering the diversity in the capabilities and costs of different plate customization techniques, the purpose of this study was to investigate the effect of the plate contouring quality on the biomechanical performance of high tibial osteotomy (HTO) fixation. A finite element model of proximal tibia was developed in Abaqus,... 

    A multi-objective approach to optimize the weight and stress of the locking plates using finite element modeling

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 236, Issue 2 , 2022 , Pages 188-198 ; 09544119 (ISSN) Rafiei, S ; Nourani, A ; Chizari, M ; Sharif University of Technology
    SAGE Publications Ltd  2022
    Abstract
    This paper aims to identify an optimum bone fracture stabilizer. For this purpose, three design variables including the ratio of the screw diameter to the plate width at three levels, the ratio of the plate thickness to the plate width at three levels, and the diameter of the bone at two levels were selected for analysis. Eighteen 3D verified finite element models were developed to examine the effects of these parameters on the weight, maximum displacement and maximum von Mises stress of the fixation structure. Considering the relations between the inputs and outputs using multivariate regression, a genetic algorithm was used to find the optimal choices. Results showed that the diameter of... 

    A comprehensive evaluation of spine kinematics, kinetics, and trunk muscle activities during fatigue-induced repetitive lifting

    , Article Human Factors ; Volume 64, Issue 6 , 2022 , Pages 997-1012 ; 00187208 (ISSN) Kazemi, Z ; Mazloumi, A ; Arjmand, N ; Keihani, A ; Karimi, Z ; Ghasemi, M. S ; Kordi, R ; Sharif University of Technology
    SAGE Publications Inc  2022
    Abstract
    Objective: Spine kinematics, kinetics, and trunk muscle activities were evaluated during different stages of a fatigue-induced symmetric lifting task over time. Background: Due to neuromuscular adaptations, postural behaviors of workers during lifting tasks are affected by fatigue. Comprehensive aspects of these adaptations remain to be investigated. Method: Eighteen volunteers repeatedly lifted a box until perceived exhaustion. Body center of mass (CoM), trunk and box kinematics, and feet center of pressure (CoP) were estimated by a motion capture system and force-plate. Electromyographic (EMG) signals of trunk/abdominal muscles were assessed using linear and nonlinear approaches. The L5-S1... 

    Trunk dynamic stability assessment for individuals with and without nonspecific low back pain during repetitive movement

    , Article Human Factors ; Volume 64, Issue 2 , 2022 , Pages 291-304 ; 00187208 (ISSN) Asgari, M ; Mokhtarinia, H. R ; Sanjari, M. A ; Kahrizi, S ; Philip, G. C ; Parnianpour, M ; Khalaf, K ; Sharif University of Technology
    SAGE Publications Inc  2022
    Abstract
    Objective: This study aimed to employ nonlinear dynamic approaches to assess trunk dynamic stability with speed, symmetry, and load during repetitive flexion-extension (FE) movements for individuals with and without nonspecific low back pain (NSLBP). Background: Repetitive trunk FE movement is a typical work-related LBP risk factor contingent on speed, symmetry, and load. Improper settings/adjustments of these control parameters could undermine the dynamic stability of the trunk, hence leading to low back injuries. The underlying stability mechanisms and associated control impairments during such dynamic movements remain elusive. Method: Thirty-eight male volunteers (19 healthy, 19 NSLBP)... 

    Biomechanical effects of lumbar fusion surgery on adjacent segments using musculoskeletal models of the intact, degenerated and fused spine

    , Article Scientific Reports ; Volume 11, Issue 1 , 2021 ; 20452322 (ISSN) Ebrahimkhani, M ; Arjmand, N ; Shirazi Adl, A ; Sharif University of Technology
    Nature Research  2021
    Abstract
    Adjacent segment disorders are prevalent in patients following a spinal fusion surgery. Postoperative alterations in the adjacent segment biomechanics play a role in the etiology of these conditions. While experimental approaches fail to directly quantify spinal loads, previous modeling studies have numerous shortcomings when simulating the complex structures of the spine and the pre/postoperative mechanobiology of the patient. The biomechanical effects of the L4–L5 fusion surgery on muscle forces and adjacent segment kinetics (compression, shear, and moment) were investigated using a validated musculoskeletal model. The model was driven by in vivo kinematics for both preoperative (intact or... 

    Effects of auxetic shoe on lumbar spine kinematics and kinetics during gait and drop vertical jump by a combined in vivo and modeling investigation

    , Article Scientific Reports ; Volume 12, Issue 1 , 2022 ; 20452322 (ISSN) Dehaghani, M. R ; Nourani, A ; Arjmand, N ; Sharif University of Technology
    Nature Research  2022
    Abstract
    The present study examined the effects of auxetic shoes on the biomechanics of the spine, as compared to barefoot and conventional shoe conditions, during gait and drop vertical jump (DVJ) activities using a combined in vivo and musculoskeletal modeling approach. Motion and force-plate data as well as electromyographic (EMG) activities of select trunk muscles of 11 individuals were collected during foregoing activities. In DVJ activity, two main phases of first landing (FL) and second landing (SL) were studied. In the FL phase of DVJ noticeable alternations were observed when auxetic shoes were used. That is, compared to the conventional footwear condition, smaller EMG activities in extensor... 

    The influence of new reciprocating link medial linkage orthosis on walking and independence in a spinal cord injury patient

    , Article Spinal Cord ; Volume 53 , October , 2015 , Pages S10-S12 ; 13624393 (ISSN) Ahmadi Bani, M ; Arazpour, M ; Farahmand, F ; Azmand, A ; Hutchins, S. W ; Vahab Kashani, R ; Mousavi, M. E ; Sharif University of Technology
    Nature Publishing Group  2015
    Abstract
    Objectives: The purpose of this paper is to describe the development and evaluation of a new medial linkage reciprocating gait orthosis (MLRGO) that incorporates a reciprocal mechanism and is sensitive to pelvic motion to potentially assist paraplegic patients to walk and provide functional independence. Case description and methods: The new orthosis was constructed and tested by a 20-year-old female paraplegic subject with transverse myelitis at T10 level, who was 4 years post injury and had also been an isocentric reciprocating gait orthosis (IRGO) user for 2 years. She received gait training for 12 weeks before undertaking gait analysis, and also completed a questionnaire that was... 

    Anxiety and cognitive load affect upper limb motor control in Parkinson's disease during medication phases

    , Article Annals of the New York Academy of Sciences ; Volume 1494, Issue 1 , 2021 , Pages 44-58 ; 00778923 (ISSN) Nodehi, Z ; Mehdizadeh, H ; Azad, A ; Mehdizadeh, M ; Reyhanian, E ; Saberi, Z. S ; Meimandi, M ; Soltanzadeh, A ; Roohi Azizi, M ; Vasaghi Gharamaleki, B ; Parnianpour, M ; Khalaf, K ; Taghizadeh, G ; Sharif University of Technology
    John Wiley and Sons Inc  2021
    Abstract
    Anxiety is among the most debilitating nonmotor symptoms of Parkinson's disease (PD). This study aimed to determine how PD patients with low and high levels of anxiety (LA-PD and HA-PD, respectively) compare with age- and sex-matched controls at the level of motor control of reach-to-grasp movements during single- and dual-task conditions with varying complexity. Reach-to-grasp movement kinematics were assessed in 20 LA-PD, 20 HA-PD, and 20 sex- and age-matched healthy controls under single- as well as easy and difficult dual-task conditions. Assessment of PD patients was performed during both the on- and off-drug phases. The results obtained during dual-task conditions reveal deficits in...