Orthopedic Biomechanics
Javad Mortazavi; Farzam Farahmand; Saeed Behzadipour; Ali Yeganeh
Volume 12, Issue 1 , June 2018, , Pages 63-74
Abstract
Intramedullary nailing is a common technique for treatment of femoral shaft fractures. Nail deformation after insertion into the bone, makes the distal hole locking a challenging task for the surgeon. The proximally mounted targeting systems for locating the position of the distal hole become ineffective ...
Read More
Intramedullary nailing is a common technique for treatment of femoral shaft fractures. Nail deformation after insertion into the bone, makes the distal hole locking a challenging task for the surgeon. The proximally mounted targeting systems for locating the position of the distal hole become ineffective due to the nail deformation. The previous image-based techniques have often considered the shape of the distal end of the nail only to find the position and direction of the distal hole. The purpose of this study was to evaluate the hypothesis of possibility of locating the position of the distal hole using mechanical modeling and radiography data simultaneously. In the proposed method, according to the nail geometry (length to diameter ratio between 25 and 50), an Euler-Bernoulli beam model is used to simulate the mechanical behavior of the nail and calculate its deformation pattern. Then, by registering the deformation pattern with the sagittal radiography image of the nail, using iterative closest point algorithm, the nail deformation and the position of the distal hole are predicted. In order to evaluate the research hypothesis, a number of experiments were performed on five cadaveric femurs and the predicted and actual positions of the distal hole were compared. Results indicated that by using mechanical modeling and the imaging data of the nail curvature, the position of the distal hole could be predicted with a mean error of 0.84 mm and a maximum error of 1.3 mm. It is expected that by combining the proposed method with the image-based techniques, which make use of the shape data of the hole, a sub-millimeter error in locating the distal hole could be achieved in future.
Medical Robotics / Bio-Robotics
Mojtaba Sharifi; Saeid Behzadipour; Hasan Salarieh; Farzam Farahmand
Volume 9, Issue 1 , April 2015, , Pages 85-98
Abstract
In this paper, a transparent bilateral controller is developed for the control of telesurgery systems that have physical interactions with soft tissue. In this control method, the parameters of a viscoelastic model of the soft tissue are estimated during its interaction with the slave robot using an ...
Read More
In this paper, a transparent bilateral controller is developed for the control of telesurgery systems that have physical interactions with soft tissue. In this control method, the parameters of a viscoelastic model of the soft tissue are estimated during its interaction with the slave robot using an on-line identification method. These estimated parameters are used inanimpedance control of the master robot which is in contact with the surgeon. Also, the slave robot tracks the master robot position using a tracking controller. Accordingly, it is shown that the transparency of the teleoperation system is obtained by estimating and realizing the dynamic parameters of the tissue for the master robot and providing the position tracking performance for the slave robot. The stability, and the position and force tracking performances are proved using the Lyapunov theorem. Moreover, the effectiveness of the proposed transparent bilateral controller is investigated by simulations performed on a piece of beef (as the soft tissue) using a two DOF robot with nonlinear dynamics. The proposed control strategy can be used in telesurgery, telesonography and telerehabilitation systems in which the robot interacts with soft tissues.
Rehabilitation Engineering
Mohammad Salehi Amini; Siavash Kazemirad; Saman Mohammadi; Roya Narimani; Farzam Farahmand
Volume 7, Issue 2 , June 2013, , Pages 121-132
Abstract
The purpose of this study was to design, analyze and evaluate an effective low-cost driving mechanism for gait trainer. The crank-rocker mechanism was favored for reproducing the path of foot during gait cycle, considering the type of motion and design parameters such as adjustability for different anthropometries, ...
Read More
The purpose of this study was to design, analyze and evaluate an effective low-cost driving mechanism for gait trainer. The crank-rocker mechanism was favored for reproducing the path of foot during gait cycle, considering the type of motion and design parameters such as adjustability for different anthropometries, providing sufficient space for interactions with physical therapist, and simplicity of execution. The dimensions of the mechanism were determined using optimization method while applying appropriate constraints so that the normal gait pattern, particularly of stance phase, was obtained. A 2-D model of the lower limb was developed to simulate the gait of a patient when using the mechanism. Results indicated that with appropriate positioning of the patient, the kinematic and kinetic patterns of the normal gait are reconstructed with no risk of injury. However, there is a high risk of injury of the knee articular surfaces and ligaments, if the patient is positioned only 3 cm higher than designed height.
Dariush Nazarinasab; Alireza Mirbagheri; Farzam Farahmand; Elnaz Afshari
Volume 7, Issue 4 , June 2013, , Pages 311-319
Abstract
During laparoscopy surgery, the surgeon cannot touch the tissues directly by his/her hand. As a result, he is not able to use tactile sensing for evaluating the tissues’ mechanical behavior and diagnosing their normal/pathological conditions. Furthermore in vivo biomechanical characteristics of ...
Read More
During laparoscopy surgery, the surgeon cannot touch the tissues directly by his/her hand. As a result, he is not able to use tactile sensing for evaluating the tissues’ mechanical behavior and diagnosing their normal/pathological conditions. Furthermore in vivo biomechanical characteristics of Intraabdominal soft tissues are among the main data required for surgery simulator softwares. The purpose of this research was to design and analyze a robotic surgical instrument which could grasp and compress the intra-abdominal large soft tissues and provide their force-displacement characteristics. The designed device is analogous to a robotic hand with two fingers, which are opened and closed using a parallelogram mechanism. A combined mechanism, including two connected sliding links and a compensatory cam, are used to prevent the fingers horizontal motion and keep the contact area fixed. The results of the kinematics analysis indicate the efficacy of the designed mechanism to provide pure vertical motion in fingers, parallel to each other. Also, the results of dynamic analysis indicate that, after dimensional optimization, the maximum force required at the actuator is 65 N, to apply a 10 N compressive force to the tissue at the middle of grasping range.
Biomechanics of Bone / Bone Biomechanics
Seyed Hamed Hosseini Nasab; Farzam Farahmand; Mohammad Hossein Karegar Novin; Mohsen Karami
Volume -1, Issue 2 , June 2005, , Pages 159-172
Abstract
Several linear and nonlinear finite element models of intact and fixed lumbar spine were analyzed. The intact model was developed based on CT images, and following verification, was employed to simulate the spinal fixation procedure using two different commercial pedicle screw systems. The results including ...
Read More
Several linear and nonlinear finite element models of intact and fixed lumbar spine were analyzed. The intact model was developed based on CT images, and following verification, was employed to simulate the spinal fixation procedure using two different commercial pedicle screw systems. The results including the force-deformation behavior and the stress distribution within the structures were studied in detail. The effects of pedicle morphology, insertion errors and material properties of bone graft on the stress distribution pattern within the vertebrae and implant components were also studied. The results suggest superiority of titanium implants over steel implants, necessity of bone graft insertion, and a higher failure risk for screws due to osteoporosis. It has been recommended that surgeons use thicker screws when dealing with pedicels with larger anterior posterior length and avoid insertion errors to minimize the risk of screw fracture.
