301 research outputs found
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Biomechanical risk factors and reduced bone health in lower limb amputees
Bone constantly adapts to its surroundings through the formation and resorption of material, controlled by bone modelling and remodelling. Strains produced by mechanical loading are one factor that drive these processes and thus determine bone health. Lower limb amputees (LLA) adopt an asymmetrical movement pattern to compensate for the loss of a limb, resulting in a change in mechanical loading and subsequently a degradation in bone health. The aetiology of the majority of amputations is vascular diseases, which affect bone health. Therefore, it is not clear whether the asymmetrical loading, or comorbidities cause the degradation in bone health in LLA. Finite element models (FEM) are used to generate strain plots and predict the bone's response to mechanical loading. To understand the relationship between the degradation in bone health and asymmetrical loads in LLAs the asymmetrical loads can be applied to a healthy bone using FEMs, or simulated within a healthy population using restrictive devices. Therefore, the overall aim was to investigate the relationship between asymmetrical loading, as observed in LLA’s, and bone health, through the use of semi-subject specific FEMs and restrictive lower limb devices.
Study one established a novel image processing method to convert peripheral quantative computed tomography (pQCT) scan images into binary and segment the tibia. The outer perimeter of the tibia was identified and sectioned to produce landmarks. The outer geometry landmarks were used to morph a base FEM, constructed from open source scan images to create semi-subject tibia FEM. Study two applied subject-specific joint reaction and muscle forces to the semi-subject tibia FEM. The strain plots output from Study two were validated against longitudinal geometrical changes from Study three. Study three, used 3D motion capture, pQCT and dual energy x-ray absorptiometry (DXA) to investigate gait and tibial geometry within a lower limb amputee and able-bodied population across twelve months. The coefficient of variation (CV) for able bodied subjects was less than 10% for ground reaction force (GRF) in level walking and less than 4% for bone total area. Study four, used a rigid foot orthosis and a trans-femoral prosthesis, to restrict able-bodied gait. Results showed participants walked significantly slower (p<0.01) in the restricted conditions, with a longer non-restricted step length (p<0.001). The loading rate and maximum GRF were higher in the non-restricted limb (p<0.05). Larger knee adductor moments were shown in the un-restricted leg in the trans-tibial condition (p<0.05).
This thesis presents a novel method of constructing semi-subject specific FEMs from pQCT scans. This can be used to further investigate the link between asymmetrical loading and bone health in LLA's and other populations with asymmetrical gait. The use of restrictive devices allow investigation into LLA's specifically, without the interference of prosthetic variability, or comorbidities
REALISTIC CADAVER MECHANICAL TESTING & QUANTITATIVE MAGNETIC RESONANCE IMAGING FOR EVALUATING KNEES THROUGHOUT WALKING
Introduction: Knees are subjected to daily physical activities, injuries and diseases, such as osteoarthritis (OA). Such complications represent significant costs (billions and thousands of USD/year for countries and individuals, respectively). Moreover, there is no OA cure and its risk factors (obesity, malalignment and injury) affect joints’ mechanical loading. Thus, knees must be studied under realistic loading conditions. Unfortunately, due to joints’ complexity (geometry, mechanical properties and loading), current experimental methods seldom achieve this. Quantitative magnetic resonance imaging (qMRI) potentially offers a non-invasive evaluation of tissue structure, biochemistry and mechanics, thereby facilitating injury or disease tracking if links between these properties and imaging outcomes were well established. However, the connections between tissue health and mechanical properties remain unclear, as is the relation between tissue- and joint-level biomechanics.
Objective: Determine if tissue structure and joint function are related in whole cadaver knees under physiologically realistic loading conditions applied via a novel MRI-safe loading device.
Methods: A novel MRI-safe knee loading device was designed, built and its repeatability assessed. Physiologic loading conditions (simulating walking) suitable for mechanical tests were determined via musculoskeletal (MSK) modelling, verified and validated against published data, and applied to a cadaver knee. To measure tibio- and patello-femoral (T-F and P-F) contact responses, a pressure sensing system was used in conjunction with the instrumented loading device. Then, to search for T2 relaxation-deformation associations, tibial and patellar cartilage deformations and T2 relaxation responses of other six ex-vivo knees subjected to axial compression (simulating standing) were measured and correlation analyses performed.
Results & Discussion: The MRI-safe loading system developed was able to simulate healthy or pathologic gait with adequate repeatability (e.g., 1.23 to 2.91 CV% for compression, comparable to existing simulators), leading to generally consistent contact responses in agreement with published experimental and finite element studies. Cartilage thickness and T2 relaxation time magnitudes measured fell within expected values, while their loading-induced changes agreed with previous studies but exhibited larger variability. Moreover, a moderate negative correlation (r = -0.402, p = 0.019) was found between unloaded tibial cartilage thickness and T2 relaxation time, which may be linked to cartilage composition (relating collagen fibers and water content)
Book of Abstracts 15th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering and 3rd Conference on Imaging and Visualization
In this edition, the two events will run together as a single conference, highlighting the strong connection with the Taylor & Francis journals: Computer Methods in Biomechanics and Biomedical Engineering (John Middleton and Christopher Jacobs, Eds.) and Computer Methods in Biomechanics and Biomedical Engineering: Imaging and Visualization (JoãoManuel R.S. Tavares, Ed.).
The conference has become a major international meeting on computational biomechanics, imaging andvisualization. In this edition, the main program includes 212 presentations. In addition, sixteen renowned researchers will give plenary keynotes, addressing current challenges in computational biomechanics and biomedical imaging.
In Lisbon, for the first time, a session dedicated to award the winner of the Best Paper in CMBBE Journal will take place.
We believe that CMBBE2018 will have a strong impact on the development of computational biomechanics and biomedical imaging and visualization, identifying emerging areas of research and promoting the collaboration and networking between participants. This impact is evidenced through the well-known research groups, commercial companies and scientific organizations, who continue to support and sponsor the CMBBE meeting
series. In fact, the conference is enriched with five workshops on specific scientific topics and commercial software.info:eu-repo/semantics/draf
Smart Sensors for Healthcare and Medical Applications
This book focuses on new sensing technologies, measurement techniques, and their applications in medicine and healthcare. Specifically, the book briefly describes the potential of smart sensors in the aforementioned applications, collecting 24 articles selected and published in the Special Issue “Smart Sensors for Healthcare and Medical Applications”. We proposed this topic, being aware of the pivotal role that smart sensors can play in the improvement of healthcare services in both acute and chronic conditions as well as in prevention for a healthy life and active aging. The articles selected in this book cover a variety of topics related to the design, validation, and application of smart sensors to healthcare
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Design and manufacture of a universal mechanical human joint simulator
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University London.The work performed in this thesis involves the study of human hip joint kinematics
and load analysis. Such analyses are very useful for investigating mobility and natural
functionality as well as the variation in motion due to replacement implants. The
objective of this study is to design, build and testing of a universal human joint
simulator that is configurable to hold several human joints and easily programmable to
create the required motion. This was performed by creating a Stewart Platform, which is
capable of moving in all six degrees of freedom; the maximum number needed by any
human joint. Many specific human joint simulators are available on the market for simulating all
major human limbs. These are used for wear testing replacement joints by using high
load repetitive motion. These systems have a predetermined limit degree of movement
and are very expensive; if one wanted to emulate another joint, one would have to
purchase a whole new system. This novel system compromises of a three-phase power supply, Control Area
Network with six actuators and drivers, a force reading clamp with strain gauges and
data logger. A user friendly computer program was developed that is able to derive joint
movement data from two inputs and replicating the movement by driving the platform,
as well as recording force and displacement data from the joint. The product would be
marketed towards biomechanical researchers and implant designers. Verification of this system was performed by simulating the human hip joint. A known combination of kinematic and force data were inputted into the system for nine different types of activities. The resultant force and joint centre displacement was then compared to see how well the system perform in comparison to the inputted data from a
previous study. The outcome of this project is a fully functional machine and configurable program
that can create movement data at varying speeds and body weights; which is also able to
drive the human joint simulator. The design also costs a fraction of any industrial joint
simulator. It is hoped that the simulator will allow easier study of both the kinematics and load
analysis within the human joints, with the intent on aiding investigation into mobility and functionality; as well as variation in motion caused by a replacement implant
Design of a robot for gait rehabilitation
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references.The ability to walk is important for independent living and when this capacity is affected by injury, gait therapy is the traditional approach to re-train the nervous system, to re-build muscle strength, to improve balance, and to re-train kinematics in order to reduce the stresses applied to bones and muscles. The importance of this problem is illustrated by the approximately 5.8 million stroke survivors alive in the US today and an estimated 700,000 strokes occurring each year. In fact, for stroke survivors with mild to moderate impairment, only 37% regain the ability to walk within one week post-stroke and 73% fall within the first six months. Falls are a leading cause of injury among Americans over 65 years old with over one third of this population experiencing a fall each year and an unsteady gait increases this risk. This growing population will require gait therapy. This thesis presents the design, development, fabrication, and proof-of-concept testing for a novel device to deliver gait therapy. While robotic devices exist, none of them take advantage of the concept of passive walkers and most focus on reproducing gait kinematics for impaired patients. Yet research has found that appropriate neural input is an important factor in efficacious therapy. For gait, this input would be the collision between the foot and the ground at heel-strike. The goal of this novel device is to allow patients to begin gait therapy before they are able to independently walk overground while maximizing the amount interface driven neural input during stepping in a safe environment.by Caitlyn Joyce Bosecker.S.M
Musculoskeletal Models in a Clinical Perspective
This book includes a selection of papers showing the potential of the dynamic modelling approach to treat problems related to the musculoskeletal system. The state-of-the-art is presented in a review article and in a perspective paper, and several examples of application in different clinical problems are provided
Development of an instrumented customizable total knee prosthesis for experimental tests.
Total knee arthroplasty (TKA) has revolutionized the life of millions of patients and it is the most efficient treatment in cases of osteoarthritis. The increase in life expectancy has lowered the average age of the patient, which requires a more enduring and performing prosthesis. To improve the design of implants and satisfying the patient's needs, a deep understanding of the
knee Biomechanics is needed. To overcome the uncertainties of numerical models, recently instrumented knee prostheses are spreading. The aim of the thesis was to design and manifacture a new prototype of instrumented implant, able to measure kinetics and kinematics (in terms of medial and lateral forces and patellofemoral forces) of different interchangeable designs of prosthesis during experiments tests within a research laboratory, on robotic knee simulator. Unlike previous prototypes it was not aimed for industrial applications, but purely focusing on research. After a careful study of the literature, and a preliminary analytic study, the device was created modifying the structure of a commercial prosthesis and transforming it in a load cell. For monitoring the kinematics of the femoral component a three-layers, piezoelettric position sensor was manifactured using a Velostat foil. This sensor has responded well to pilot test. Once completed, such device can be used to validate existing numerical models of the knee and of TKA and create new ones, more accurate.It can lead to refinement of surgical techniques, to enhancement of prosthetic designs and, once validated, and if properly modified, it can be used also intraoperatively
The influence of attentional focus on neuroplasticity following a seven-day balance training intervention
It is well established that focusing on the external effect of one’s movement (an external focus of attention) results in enhanced motor learning and produces superior motor performance compared to focusing inward on the body’s own physical execution of the motor movement (an internal focus). While the benefits of an external focus in motor learning, and the detriments of an inward or ‘internal’ focus have been highly replicated, there is still little mechanistic understanding pertaining to the brain-related changes that may result from these two different foci of attention during motor training. Since the brain is highly malleable and has been shown to adapt in response to motor training (i.e., neuroplasticity), it is postulated that attentional focus may change the brain’s structure and function. However, no direct examination exploring the influence of attentional focus on neuroplasticity (structural or functional) exists. The primary objective of this study was to determine the effects of balance training with different attentional foci on brain-related neuroplasticity in a young healthy population. Participants (n = 33) were randomly assigned to a control, internal focus, or external focus condition. Functional and structural brain connectivity analyses was conducted using neuroimaging data collected through functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) prior to (baseline) and following a seven-day balance training intervention (retention). Between baseline and retention data collection, participants in the internal and external focus training groups practiced a dynamic balance task for one hour per day, each day for seven consecutive days (acquisition). For the internal focus trials, participants were asked to, ‘focus on keeping their feet level;’ whereas, for the external focus trials participants were asked to, ‘focus on keeping the board level.’ The control group did not complete any balance training, but completed baseline and retention balance measurements. An inertial measurement unit was attached to the center of the balance board to assess the performance and learning of the balance task. Resting-state brain connectivity analyses were performed on the fMRI data to contrast connectivity differences for each group at retention relative to baseline, and, for the diffusion data (DTI), fractional anisotropy analyses (a metric to quantify water diffusion within a voxel of white-matter) was performed to quantify the relationship between changes in balance and water diffusivity within white-matter tracts. Classical attentional focus effects were observed for acquisition, with those in the external focus condition producing significantly less mean and standard deviation velocity compared to the internal focus group (both p .05). These results suggest that a seven-day balance training program with attentional focus in a young healthy population influences brain function (specifically correlated activity at rest), but longer training programs or more rest may be needed to influence brain structure (as measured by fractional anisotropy). These findings have important implications for a variety of clinical populations who show altered resting-sate connectivity and deteriorations in balance control (e.g., Alzheimer’s disease, stroke survivors). Seven days of balance training with an external focus may be useful in improving balance control and may influence correlated brain activity at rest, but longer training programs or more rest may be needed to influence brain structure. We discuss these findings in the context of the constrained-action hypothesis and OPTIMAL theory
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