Sharif Digital Repository

Objective: Stability is important to prevent falls during occupational and daily living activities. Control parameters such as speed, direction of motion and external load can affect stability pattern. The purpose of this study was to evaluate the effect of the mentioned control parameters on stability control pattern.
Methods: Kinematic data (rotation angles) to 19 healthy volunteers and 19 patients with low back pain associated with repeated trunk bending motion in eight different conditions of speed (high and slow), direction (symmetric and asymmetric planes) and external load (with and without load), was evaluated. Since the volunteers do during dynamic movements, they must also be... 

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... 

The 1991 NIOSH Lifting Equation (NLE) is widely used to assess the risk of injury to the spine by providing estimates of the recommended weight limit (RWL) in hands. The present study uses the AnyBody modeling software to verify whether the RWL generates L5-S1 within the limits (e.g., 3400 N for compression recommended by NIOSH and 1000 N for shear recommended in the literature). Twenty-four symmetric and asymmetric lifting activities were simulated to evaluate the RWL by the NLE and the L5-S1 loads by AnyBody. In two activities, involving large trunk flexion and 30 and 60 degrees of load asymmetry, the estimated RWL generated L5-S1 spine loads exceeding the recommended limits. The NIOSH... 

Spinal diseases are prevalent and costly. Excessive mechanical loads on the spine play a crucial role in the etiology of back disorders. To estimate spinal loads one needs to calculate unknown muscle forces through either an optimization or EMG-driven approach. Both approaches involve several assumptions and simplifications regarding anatomy of muscles,mechanical properties of the spinal tissues, and estimation of the muscle forces. An alternative approach is to estimate spinal loads through effect of muscle forces, i.e., kinematics generated by muscles rather than forces generated by muscles. The present study hence aims to estimate spinal loads using a detailed finite element (FE) model of... 

Spinal instrumentation with pedicle screws has become a widespread surgical procedure in the treatment of spinal disease. The traditional way of placing pedicle screws is to use the anatomical landmarks which at many times can be a best guess resulting in breaches of the pedicle and causing neurological injuries. Additional modalities used include the intra-operative fluoroscopy or navigation systems, which results in radiation exposure and more intra-operative time. In order to solve the technical problems, a pedicle screw navigation template that guarantees the correct implantation position and direction of vertebral pedicle screws, can be used. Compared to pedicles in the lumbar spine,... 

Manual material handling (MMH) is associated with mechanical back injuries. To manage such injuries, musculoskeletal models are employed to estimate spinal loads during MMH. These models require, as input, 3D-position of the hand-load and body posture whose measurements involve skillful and time-consuming motion analysis investigations.In order to facilitate the procedure of posture measurements and load estimations, three coupled artificial-neural-networks (ANNs) were developed. To predict whole body posture, ANN1 was trained based on our novel measurements on 15 individuals. Each individual performed several static-tasks by holding 0, 5, and 10 kg weight at 9 different anterior-left... 

The aim of homogenization theory is to establish the macroscopic behaviour of a system which is ‘microscopically’ heterogeneous, in order to describe some characteristics of the heterogeneous medium (for instance, its thermal or electrical conductivity). This means that the heterogeneous material is replaced by a homogeneous fictitious one (the ‘homogenized’ material), whose global (or overall) characteristics are a good approximation of the initial ones. From the mathematical point of view, this signifies mainly that the solutions of a boundary value problem, depending on a small parameter, converge to the solution of a limit boundary value problem which is explicitly described. In... 

Today, obesity, as a major global health challenge, affects more than 30 percent of the world's population. To investigate the effect of obesity on spinal function, a common method is motion analysis (kinematic method). This method is based on the claim that the abnormal mechanical function of the spine is directly related to its abnormal motions.The aim of this study is to measure and compare the range of motions (RoMs) of different segments of the spine in all anatomical plates between obese and normal individuals, as well as to calculate and compare some motion rhythms between the lumbar spine and the pelvis in these two groups. Comparing the posture of the spine between obese and normal...