Sharif Digital Repository

The human brain is the most sensitive and important human organ and surgery must be done with high precision and without risk. During surgery, brain tissue deform continuously due to gravity, out of the cerebrospinal fluid and the changing pressure of the cerebrospinal fluid and the surgical maneuvers. Because the surgeon has no direct view on brain internal, the ways to solve this problem is to pay attention. This method makes it possible to the surgeon see in the brain and the brain tissue deformation. This thesis method is based on biomechanical modeling. After forming finite element model from the pre-operative MRI, brain surface and volume datasets during surgery as a load, apply to the... 

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... 

Low back pain is one of the musculoskeletal diseases which is an important issue for general health of society in both quality of life and costs. Most of the clinical instructions employ exercise as a clinical treatment in order to cure chronic low back pain. General and core stability exercises are of common prevalence, however, there are disputes about the effectiveness of these exercises in the literature. The aim of this study is to answer the question whether stabilizer exercise can significantly alter the stability of vertebral column in comparison with general exercises. Hence, experiments have been designed and conducted. The participants have been divided to two group. Within six... 

Nowadays, the use of vehicles is inevitable for all people including pregnant females. Vehicle vibrations during passing road bumps and holes is one of the pregnant females’ concerns. The aim of the present study is to develop a biomechanical model of a Uterus and Fetus Set (UFS) to evaluate its response to the inferior excitation, caused by the vehicle passing over speed bumps. The most important innovation of this research is "Analysis of the effect of vehicle speed and speed bumps characteristics on the risk of injury to the fetus." "Modeling the pregnant uterus complex separately from other abdominal organs", "Biomechanical modeling based on CT scan data from a real subject", "Providing... 

Eye and vision are the most important tools and the perceptual sense of human. This important vital member is one of the most vulnerable organs of human body. For example in the United States 1.9 million eye surgery are being done yearly which include 9 thousand globe rupture and 30 thousand blindness due to impacts on the eye. Eye traumas could have occurred as mechanical, radiation, thermal, chemical, etc. among these, the damages related to the airbag impact which is subset of mechanical damages, take a significant percentage. Presenting a model of human eye in car airbag blunt impacts during accident could be effective for receiving helpful information from damage of the internal parts... 

Nowadays, Eye injuries caused by blunt impacts are considered among the major causes of blindness and vision problems; therefore, studying the existence of possible damages can be quite useful and effective. One of the quickest and most suitable methods in identifying damage parameters is finite-element modeling of the human eye. In this regard, in the current study, first a geometrical design was created by incorporating CT-Scan images of the eye into Mimics and later Solid works software. Afterwards, the most suitable mechanical properties for the constituents of the eye were extracted from the literature. The mechanical properties of vitreous and Sclera were obtained by experimental... 

A single-degree-of-freedom model is considered for flexible exercise bars based on the lumped-element approach. By considering the side segment of a flexible exercise bar as a cantilever beam with an equivalent mass at the free end, its free-vibration response and forced one under excitation of the grip of the flexible bar is written parametrically. Some experiments are performed on a specific flexible bar to obtain numerical values for the parameters in the model to have it quantitatively known. In the next step, simulation of the model results in the response of the flexible bar under a considered excitation. The response is imported into a multi-segment musculoskeletal software, AnyBody,... 

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... 

Subdural hemorrhage (SDH) is one of the most common traumatic brain injuries. The mortality rate of SDH is over 30 percent. In addition, patients require to visit hospital for treatment and further healthcare. According to the costs of treatment and frequency of injuries, prevention of SDH is essential. 3D-Finite element modeling of human head is an appropriate tool for evaluation of injury risk and setting up a prevention tolerance criteria. The aim of this study is to create a 3D finite element model of human head with special consideration of vessels. Vessels are modeled by truss elements at current finite element models of human head; however, geometry of vessels is regarded as simple... 

Most elderly and physically disabled people suffer from lack of functionality and dexterity in their elbow or wrist. These disabilities are due to the damages mostly caused by sport surgery, spinal surgery, or stroke. Therefore, design of an assistive exoskeleton robot for upper limb movements seems necessary. The purpose of this study is to design, fabricate and deliver a control algorithm for an assistive wearable robot. The robot has five degrees of freedom in order to help the flexion/extension and abduction/adduction shoulder. Dynamic and kinematic model of elbow, forearm, and wrist is developed to determine the amounts of torques which are required in the joint actuators mounted on the... 

We have recently designed/fabricated novel bilateral vertebra- and patient-specific drill guides for pedicle screw (PS) placements and tested their accuracy for both nondeformed and deformed thoracic spines. PS placement deviations from their preplanned positions significantly reduced when guide template were used; the success rate improved from ~72% (freehand placements) to 94% (guided placements). In the present study, we aim to use finite element (FE) analyses to evaluate the pull-out strength of these PSs inserted via either the freehand technique or our drill-guide templates. Two 3D-printed T1-T12 thoracic models of a severe scoliosis patient with a 47° thoracic dextro-scoliotic curve... 

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... 

Foot related problems or diseases such as plan foot pain, diabetic foot, arthritic foot, pathological flatfoot, ankle sprain, bone fracture or other sports related injuries have been costing a significant amount of medical expenditure. Abnormal loading patterns and high pressure on the foot as well as improper or ill-fitting footwear are thought to be one major mechanical cause of foot problems. Most ankle sprains respond favorably to nonsurgical treatment, such as those offered by physical therapists, doctors of chiropractic, and rehabilitation specialists. A comprehensive history and examination aid in diagnosing the severity and type of ankle sprain. Based on the diagnosis and an... 

Heart failure is one of the leading causes of death around the world and diastolic dysfunction is the main culprit behind about 30 percent of them. End-diastolic pressure-volume relationship is one of the most important indices of ventricles diastolic function, however invasive nature of assessment, has hindered its use in clinical applications. Despite the advances in computational modeling and bio-mechanical simulations, computational cost of these procedures often renders the computational methods unsuitable for clinical implications. Machine learning methods are usually the proper substitute in such cases. However, this method requires a large set of pre-calculated data for training,... 

Background: Degeneration of intervertebral joints due to kinetical alterations after fusion surgery is a prevalent back disorder. While in-vivo studies are limited to medical imaging techniques, in-vitro and in-silico (passive FE modeling) investigations lack the crucial role of muscle forces. Available musculoskeletal modeling studies, not only suffer oversimplification of intervertebral joints, but have some shortcomings in incorporation of the contributing factors (that may alter postoperative kinetics). On the other hand, one of the main shortcomings in the available musculoskeletal models is their inability to account for dynamic effects and modeling transient events. Purpose: 1-... 

Objective: To assess adequacy of the National Institute for Occupational Safety and Health (NIOSH) Lifting Equation (NLE) in controlling lumbar spine loads below their recommended action limits during load-handling activities in the stoop and squat using a detailed musculoskeletal model,that is, the AnyBody Modeling System.Background: The NIOSH committee employed simplistic biomechanical models for the calculation of the spine compressive loads with no estimates of the shear loads. In addition, NLE does not include the posture of the knee during manual material handling. It is therefore unknown whether the NLE would adequately control lumbar compression and shear loads below their... 

BASHTI is a new implant-less ACL reconstruction surgery which has recently been considered for its advantages. This study aimed to investigate the effects of tendon and cannulated drill bit diameter on the BASHTI fixation strength and core bone engaged length (CBEL) in an anterior cruciate ligament (ACL) reconstruction. It is believed that CBEL may affect both bone healing process and fixation strength in this technique. Bovine digital tendons and Sawbones blocks were used to mimic the ACL reconstruction. Tendons were sized to 6, 7, 8, 9, and 10 mm and the hole size for the 6-9 mm tendons was set to 10 mm while for the 10 mm tendon was set to 12 mm. Mechanical strength of the specimens was... 

Obesity is a worldwide growing health challenge affecting ~30% of the world's population. Increased rate of disc degeneration and herniation, low back pain and surgery has been reported in obese individuals. Although obesity-related low back diseases have multifactorial etiology, presumably greater mechanical loads on the spine of heavier individuals during their daily activities may be considered as a risk factor. Likely larger trunk muscle sizes, disc sizes and thus passive stiffness in heavier individuals may however partly or fully offset the effect of their additional body weight on the spinal loads. In absence of in vivo approaches, the present study aims to construct subject-specific... 

80% of people in all over the world, experience Low Back Pain (LBP) once in their lives. LBP leads to dysfunction of spine. About 25% of LBP relates to the intervertebral disks which in the critical cases, a Posterior Lumbar Surgery (PLS) on the one or more lumbar disks should be done. Due to the some procedure such as retracting, cutting or denervation of muscles, PLS can hurt trunk muscles and spine. Thus, investigation of LBP and postoperative complications of PLS can help us in recognition of causes of LBP and PLS complications and modification of PLS approaches. The objective of this research was investigation of effects of LBP and PLS on the biomechanical function of spine. Pattern of... 

Obesity is a worldwide growing health challenge affecting ~30% of the world's population. Increased rate of disc degeneration and herniation, low back pain and surgery has been reported in obese individuals. Although obesity-related low back diseases have multifactorial etiology, presumably greater mechanical loads on the spine of heavier individuals during their daily activities may be considered as a risk factor. Likely larger trunk muscle sizes, disc sizes and thus passive stiffness in heavier individuals may however partly or fully offset the effect of their additional body weight on the spinal loads. In absence of in vivo approaches, the present study aims to construct subject-specific...