Showing papers by "Mohamad Parnianpour published in 2011"

Low back pain in Iran: a growing need to adapt and implement evidence-based practice in developing countries.

Abstract: Study design A descriptive overview of the literature. Objective To present a comprehensive descriptive overview of the published papers about epidemiologic features, burden, and current management of low back pain (LBP) in Iran. Summary of background data Little is known about the epidemiology, burden, and management of LBP in developing and low- to middle-income countries, such as Iran. Methods A literature search was carried out using MEDLINE database to assess existing literature about prevalence, disease burden, impact, and current management of nonspecific LBP in Iran. Results Twenty-six articles matched inclusion criteria and included in the study. The findings related to point, period, and lifetime prevalence of LBP in general population, working population, school children, and pregnant women ranged from 14.4% to 84.1%. The 1-year incidence of disabling LBP was found to be 2.1%. LBP is the third leading cause of disease burden (measured by Disability Adjusted Life Years) in Iranian population aged 15 to 69 years, without considering causes of intentional and unintentional injuries. High levels of anxiety and depression among patients with LBP and the etiological role of job strain in causing LBP in workers have been reported in Iran. Our search failed to find any articles about referral system, direct and indirect costs, social determinants, and current management of LBP in Iran. Conclusion This overview of the literature illustrates that LBP is a common symptom and an important cause of disease burden in Iran, in particular, in the most productive age for both males and females. The 1-year incidence of disabling LBP in Iran was found to be low. Future research will be necessary to investigate economic cost, social determinants, health technology assessment, and management of LBP in Iran.

Control of human spine in repetitive sagittal plane flexion and extension motion using a CPG based ANN approach

Abstract: The complexity associated with musculoskeletal modeling, simulation, and neural control of the human spine is a challenging problem in the field of biomechanics. This paper presents a novel method for simulation of a 3D trunk model under control of 48 muscle actuators. Central pattern generators (CPG) and artificial neural network (ANN) are used simultaneously to generate muscles activation patterns. The parameters of the ANN are updated based on a novel learning method used to address the kinetic redundancy due to presence of 48 muscles driving the trunk. We demonstrated the feasibility of the proposed method with numerical simulation of experiments involving rhythmic motion between upright standing and 55 degrees of flexion. The tracking performance of the model is accurate to within 2° while reciprocal muscle activation patterns were similar to the observed experimental coordination patterns in normal subjects. The suggested method can be used to map high-level control strategies to low-level control signals in complex biomechanical and biorobotic systems. This will also provide insight about underlying neural control mechanisms.

The effect of resistance level and stability demands on recruitment patterns and internal loading of spine in dynamic flexion and extension using a simple trunk model

Abstract: The effects of external resistance on the recruitment of trunk muscles in sagittal movements and the coactivation mechanism to maintain spinal stability were investigated using a simple computational model of iso-resistive spine sagittal movements. Neural excitation of muscles was attained based on inverse dynamics approach along with a stability-based optimisation. The trunk flexion and extension movements between 60° flexion and the upright posture against various resistance levels were simulated. Incorporation of the stability constraint in the optimisation algorithm required higher antagonistic activities for all resistance levels mostly close to the upright position. Extension movements showed higher coactivation with higher resistance, whereas flexion movements demonstrated lower coactivation indicating a greater stability demand in backward extension movements against higher resistance at the neighbourhood of the upright posture. Optimal extension profiles based on minimum jerk, work and power had ...

SVD analysis of dynamic properties for fatigue loaded intervertebral disc

Abstract: This paper uses singular value decomposition (SVD) for studying the dynamic properties of fatigue-loaded intervertebral disc. Previously, this problem had been addressed using mathematical models of using mass, spring and damper or based on poroelastic theory. This paper utilizes the signal processing approach and attempts to describe SVD based feature that can be an indicator for change in behavioral performance of the intervertebral disc warning the occurrence of temporary or permanent change in the structure or abnormality in behavior. The results are encouraging; however, further validation is required with more data.

A mixture of modular structures to describe human motor planning level: A new perspective based on motor decomposition

Abstract: A modular hierarchical structure is developed to describe human movement planning level. The modular feature of the proposed model enables it to generalize planning a task. The movements are planned based on decomposing a task into its corresponding subtasks (motion phases). There is a module responsible for one condition. The final plan is constructed using soft computing of the plans proposed by different modules. Each module estimates the kinematics of the joints at the end of each subtask; we call them kinematic estimator modules (KEMs). A timing module estimates the duration of motion and a gating module determines the responsibility of each KEM under different conditions. To evaluate the performance of the proposed model, a set of experimental data are collected for the Sit-to-Stand movement under five different bases of support as different conditions. The results showed that this architecture is able to plan the motion under new untested conditions. Good match between the simulation results and experimental movement, low computational requirements as well as behavioral and neurophysiological supports, make it to be considered as a good candidate to interpret computationally the function of the motor planning level in the central nervous system.

Effects of construction worker's experience, the presence of safety handrail and height of movable scaffold on postural and spinal stability

Abstract: In this study, posture and spinal stability were evaluated during a manual task in a standing posture on a movable scaffold at two levels of heights, with and without safety handrails between experts and novice construction workers using insole pressure transducers and muscle activities of trunk muscles. Eight construction workers (4 experts and 4 novices) working at a construction site participated in the experiment for ergonomic assessment. A significant difference was found in postural stability, spinal stability with regard to career (p<0.01), floor (p<0.01), and presence of a safety handrail (p<0.01), based on Manova and Anova analyses. It was also found that the standard deviation of COP (Center of Pressure), and back muscle activities increased, when career is lower, scaffold height is higher, and the safety handrail is not installed. The experiment results suggest that the risk of a fall incident and back pain may increase at lower worker's experience (career), higher moveable scaffolding frame, and without safety handrail.

Comparison of the viscoelastic creep behavior of spine different regions by using finite element method

Abstract: There are extensive differences in the structure and composition between cervical and thoracolumbar discs. There is no comparison between the time-dependent "creep" behavior of different regions of spine. In this study, three different finite element models of motion segments in spine different regions (Lumbar, Thoracic and Cervical) were prepared. All of the models were prepared by using a new element. The new element consists a disc (Viscoelastic Euler Beam Element) and a vertebra (Rigid Link) as a unit element. The hire of new element leads to reduction of the runtime of the models. For validating the models, prediction of the lumbar segment motion model for short creep test was compared with in-vivo result. After validation of the model predictions, other models were subjected to the same boundary conditions. The results show that although the creep results for the models of lumbar region and thoracic region are near to each other, they are differences from cervical region results.

A computation tool to simulate trunk motion and predict muscle activation by assigning different weights to physical and physiological criteria

Abstract: A central problem in motor control is to understand how the many biomechanical degrees of freedom are coordinated to achieve a goal. A common assumption is that Central Nervous System (CNS) will plan tasks based on open-loop optimal control theory which simultaneously predicts state variables and motor commands based on a compound objective function. A 3D computational method incorporated with 18 anatomically oriented muscles is used to simulate human trunk system. Direct collocation method allows us to convert a constrained optimal control problem to a common nonlinear programming problem to assume the spinal stability condition. Trunk movement from the upright standing to 60 degrees of flexion is simulated based on this method. Incorporation of the stability condition with the open-loop optimal controller resulted in an increase of antagonistic activities which would increase the joint stiffness around the Lumbosacral joint in response to gravity perturbation. Results showed that different patterns of trunk movement and back muscles activity can be explained based on change in the coefficient of two performance indices.

A finite element model of trunk with muscles by both active and passive contractions

Abstract: Prevalence of LBP has led researchers to find out biomechanics of lumbar spine in conjunction with the surrounding muscles and the role of intra-abdominal pressure in different activities. Despite substantial number of experimental studies in this field, limitations of in-vivo experiments have guided researchers to utilize mathematical modeling to obtain more information regarding the spine biomechanics. An important aspect of such spinal modeling is to replicate the muscle behavior which includes nonlinear mechanical properties. In this study, we developed a finite element model of the spine with the surrounding muscles consisting both active and passive behavior of the muscles at the same time. In order to have more realistic muscles, we used the combination of a 1-D nonlinear element and a 2-D linear elastic shell. The shell element can take initial stress, while the 1-D element can take force-displacement relationship. For each muscle, 1-D elements were laid on shell elements in the direction of muscle fibers. In a specific activity level, initial stress and stiffness of shell elements and force-displacement relation of 1-D elements were changed based on mathematical model of muscles published in the literature. The effects of two muscles of the model were investigated on lumbar spine and IAP. These muscles are rectus abdominis and transversus abdominis. Results show that TA has an important effect on IAP generation and this muscle can produce extensor moment due to increasing IAP. RA has flexor role and has no important effect on IAP. Also analyses have predicted a reduction in lumbar spine compression force with increasing IAP.