Search for: biomechanical-phenomena
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Total 47 records

    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
    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... 

    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
    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... 

    Relative performances of artificial neural network and regression mapping tools in evaluation of spinal loads and muscle forces during static lifting

    , Article Journal of Biomechanics ; Volume 46, Issue 8 , 2013 , Pages 1454-1462 ; 00219290 (ISSN) Arjmand, N ; Ekrami, O ; Shirazi Adl, A ; Plamondon, A ; Parnianpour, M ; Sharif University of Technology
    Two artificial neural networks (ANNs) are constructed, trained, and tested to map inputs of a complex trunk finite element (FE) model to its outputs for spinal loads and muscle forces. Five input variables (thorax flexion angle, load magnitude, its anterior and lateral positions, load handling technique, i.e., one- or two-handed static lifting) and four model outputs (L4-L5 and L5-S1 disc compression and anterior-posterior shear forces) for spinal loads and 76 model outputs (forces in individual trunk muscles) are considered. Moreover, full quadratic regression equations mapping input-outputs of the model developed here for muscle forces and previously for spine loads are used to compare the... 

    The effects of movement speed on kinematic variability and dynamic stability of the trunk in healthy individuals and low back pain patients

    , Article Clinical Biomechanics ; Volume 30, Issue 7 , Aug , 2015 , Pages 682-688 ; 02680033 (ISSN) Asgari, M ; Sanjari, M. A ; Mokhtarinia, H. R ; Moeini Sedeh, S ; Khalaf, K ; Parnianpour, M ; Sharif University of Technology
    Elsevier Ltd  2015
    Background: Comparison of the kinematic variability and dynamic stability of the trunk between healthy and low back pain patient groups can contribute to gaining valuable information about the movement patterns and neuromotor strategies involved in various movement tasks. Methods: Fourteen chronic low back pain patients with mild symptoms and twelve healthy male volunteers performed repeated trunk flexion-extension movements in the sagittal plane at three different speeds: 20 cycles/min, self-selected, and 40 cycles/min. Mean standard deviations, coefficient of variation and variance ratio as variability measures; maximum finite-time Lyapunov exponents and maximum Floquet multipliers as... 

    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... 

    Objective measurement of inferior-directed stiffness in glenohumeral joint using a specially designed robotic device in healthy shoulders; within- and between-session reliability

    , Article Journal of Biomechanics ; Volume 127 , 2021 ; 00219290 (ISSN) Azarsa, M. H ; Mirbagheri, A. R ; Hosseini, R ; Shadmehr, A ; Karimi, N ; Sharif University of Technology
    Elsevier Ltd  2021
    Clinical assessment of capsuloligamentous structures of the glenohumeral joint has been qualitative and subjective in nature, as demonstrated by limited intra- and inter-rater reliability. Robotic devices were utilized to develop a clinically objective measurement technique for glenohumeral joint stiffness. The purpose of this study was to quantify the amount of inferior-direction stiffness of the glenohumeral joint using a safe clinical device in the asymptomatic individuals, and to determine between trial and between session reliability of the robotic device. Twenty healthy subjects were recruited via convenience sampling. Inferior-directed translation and applying force were measured... 

    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
    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... 

    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
    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... 

    Effects of an exercise therapy targeting knee kinetics on pain, function, and gait kinetics in patients with knee osteoarthritis: A randomized clinical trial

    , Article Adapted Physical Activity Quarterly ; Volume 38, Issue 3 , 2021 , Pages 377-395 ; 07365829 (ISSN) Bokaeian, H. R ; Esfandiarpour, F ; Zahednejad, S ; Kouhzad Mohammadi, H ; Farahmand, F ; Sharif University of Technology
    Human Kinetics Publishers Inc  2021
    In this study, the effects of an exercise therapy comprising yoga exercises and medial-thrust gait (YogaMT) on lower-extremity kinetics, pain, and function in patients with medial knee osteoarthritis were investigated. Fifty-nine patients were randomly allocated to three treatment groups: (a) the YogaMT group practiced yoga exercises and medial thrust gait, (b) the knee-strengthening group performed quadriceps-and hamstring-strengthening exercises, and (c) the treadmill walking group practiced normal treadmill walking in 12 supervised sessions. The adduction and flexion moments of the hip, knee, and ankle; pain intensity; and 2-min walking test were assessed before and after treatment and at... 

    Goal equivalent manifold analysis of task performance in non-specific LBP and healthy subjects during repetitive trunk movement; effect of load, velocity, symmetry

    , Article Human Movement Science ; Volume 51 , 2017 , Pages 72-81 ; 01679457 (ISSN) Chehrehrazi, M ; Sanjari, M. A ; Mokhtarinia, H. R ; Jamshidi, A. A ; Maroufi, N ; Parnianpour, M ; Sharif University of Technology
    Motor abundance allows reliability of motor performance despite its variability. The nature of this variability provides important information on the flexibility of control strategies. This feature of control may be affected by low back pain (LPB) and trunk flexion/extension conditions. Goal equivalent manifold (GEM) analysis was used to quantify the ability to exploit motor abundance during repeated trunk flexion/extension in healthy individuals and people with chronic non-specific LBP (CNSLBP). Kinematic data were collected from 22 healthy volunteers and 22 CNSLBP patients during metronomically timed, repeated trunk flexion/extension in three conditions of symmetry, velocity, and loading;... 

    Can the body slope of interference screw affect initial stability of reconstructed anterior cruciate ligament?: An in-vitro investigation

    , Article BMC Musculoskeletal Disorders ; Volume 22, Issue 1 , 2021 ; 14712474 (ISSN) Daneshvarhashjin, N ; Chizari, M ; Mortazavi, J ; Rouhi, G ; Sharif University of Technology
    BioMed Central Ltd  2021
    Background: Superior biomechanical performance of tapered interference screws, compared with non-tapered screws, with reference to the anterior cruciate ligament (ACL) reconstruction process, has been reported in the literature. However, the effect of tapered interference screw’s body slope on the initial stability of ACL is poorly understood. Thus, the main goal of this study was to investigate the effect of the interference screw’s body slope on the initial stability of the reconstructed ACL. Methods: Based on the best screw-bone tunnel diameter ratios in non-tapered screws, two different tapered interference screws were designed and fabricated. The diameters of both screws were equal to... 

    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
    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... 

    Comparison of the trunk-pelvis and lower extremities sagittal plane inter-segmental coordination and variability during walking in persons with and without chronic low back pain

    , Article Human Movement Science ; Volume 52 , 2017 , Pages 55-66 ; 01679457 (ISSN) Ebrahimi, S ; Kamali, F ; Razeghi, M ; Haghpanah, S. A ; Sharif University of Technology
    Elsevier B.V  2017
    Inter-segmental coordination can be influenced by chronic low back pain (CLBP). The sagittal plane lower extremities inter-segmental coordination pattern and variability, in conjunction with the pelvis and trunk, were assessed in subjects with and without non-specific CLBP during free-speed walking. Kinematic data were collected from 10 non-specific CLBP and 10 non-CLBP control volunteers while the subjects were walking at their preferred speed. Sagittal plane time-normalized segmental angles and velocities were used to calculate continuous relative phase for each data point. Mean absolute relative phase (MARP) and deviation phase (DP) were derived to quantify the trunk-pelvis and bilateral... 

    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
    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... 

    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
    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... 

    Comparison of kinematics of ACL-deficient and healthy knees during passive flexion and isometric leg press

    , Article Knee ; Volume 20, Issue 6 , December , 2013 , Pages 505-510 ; 09680160 (ISSN) Esfandiarpour, F ; Shakourirad, A ; Talebian Moghaddam, S ; Olyaei, G ; Eslami, A ; Farahmand, F ; Sharif University of Technology
    Background: Studying the kinematics of the ACL deficient (ACLD) knees, during different physiological activities and muscle contraction patterns, can improve our understanding of the joint's altered biomechanics due to ACL deficiency as well as the efficacy and safety of the rehabilitations exercises. Methods: Twenty-five male volunteers, including 11 normal and 14 unilateral ACLD subjects, participated in this study. The kinematics of the injured knees of the ACLD subjects was compared with their intact knees and the healthy group during passive flexion and isometric leg press with the knees flexed from full extension to 45° flexion, with 15° intervals. An accurate registration algorithm... 

    Subject-specific 2D/3D image registration and kinematics-driven musculoskeletal model of the spine

    , Article Journal of Biomechanics ; Volume 57 , 2017 , Pages 18-26 ; 00219290 (ISSN) Eskandari, A. H ; Arjmand, N ; Shirazi Adl, A ; Farahmand, F ; Sharif University of Technology
    An essential input to the musculoskeletal (MS) trunk models that estimate muscle and spine forces is kinematics of the thorax, pelvis, and lumbar vertebrae. While thorax and pelvis kinematics are usually measured via skin motion capture devices (with inherent errors on the proper identification of the underlying bony landmarks and the relative skin-sensor-bone movements), those of the intervening lumbar vertebrae are commonly approximated at fixed proportions based on the thorax-pelvis kinematics. This study proposes an image-based kinematics measurement approach to drive subject-specific (musculature, geometry, mass, and center of masses) MS models. Kinematics of the thorax, pelvis, and... 

    Hypersensitivity of trunk biomechanical model predictions to errors in image-based kinematics when using fully displacement-control techniques

    , Article Journal of Biomechanics ; Volume 84 , 2019 , Pages 161-171 ; 00219290 (ISSN) Eskandari, A. H ; Arjmand, N ; Shirazi Adl, A ; Farahmand, F ; Sharif University of Technology
    Elsevier Ltd  2019
    Recent advances in medical imaging techniques have allowed pure displacement-control trunk models to estimate spinal loads with no need to calculate muscle forces. Sensitivity of these models to the errors in post-imaging evaluation of displacements (reported to be ∼0.4–0.9° and 0.2–0.3 mm in vertebral displacements) has not yet been investigated. A Monte Carlo analysis was therefore used to assess the sensitivity of results in both musculoskeletal (MS) and passive finite element (FE) spine models to errors in measured displacements. Six static activities in upright standing, flexed, and extended postures were initially simulated using a force-control hybrid MS-FE model. Computed vertebral... 

    Spinal segment ranges of motion, movement coordination, and three-dimensional kinematics during occupational activities in normal-weight and obese individuals

    , Article Journal of Biomechanics ; Volume 123 , 2021 ; 00219290 (ISSN) Ghasemi, M ; Arjmand, N ; Sharif University of Technology
    Elsevier Ltd  2021
    Measurements of spinal segment ranges of motion (RoMs), movement coordination, and three-dimensional kinematics during occupational activities have implications in occupational/clinical biomechanics. Due to the large amount of adipose tissues, obese individuals may have different RoMs, lumbopelvic coordination, and kinematics than normal-weight ones. We aimed to measure/compare trunk, lumbar, and pelvis primary RoMs in all anatomical planes/directions, lumbopelvic ratios (lumbar to pelvis rotations at different trunk angles) in all anatomical planes/directions and three-dimensional spine kinematics during twelve symmetric/asymmetric statics load-handling activities in healthy normal-weight... 

    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
    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...