Biomechanics and Biotransport Commons^™

Direct Numerical Simulation Of Pulsating Flow In Curved Pipes: Insights Into Aortic Dissection In Humans, Gokul Anugrah Gopakumar

Theses and Dissertations--Mechanical and Aerospace Engineering

This dissertation investigates the hemodynamics of pulsating blood flow in curved vessels through direct numerical simulations (DNS), with the overarching aim of uncovering fluid dynamic mechanisms linked to the onset and progression of aortic dissection in humans. The work is structured in two parts: (i) fundamental studies in idealized geometries and (ii) preliminary investigations in patient-specific anatomies. In the first part, curved pipe models representing the aortic arch are used to isolate the effects of pulsation frequency, amplitude ratio, and curvature ratio on transitional and turbulent flow dynamics. The simulations reveal that curvature-driven centrifugal forces shift the peak velocity toward …

Defining Sagittal Plane Gait Mechanics And Joint Loading In People With Marfan Syndrome, Justin Melan Pol

Theses and Dissertations--Biomedical Engineering

Marfan syndrome (MFS) is a genetic condition that is associated with altered muscle composition, which leads to muscle dysfunction. People with MFS exhibit high instances of lower extremity (LE) joint pain that inhibits their ability to perform activities of daily living, such as walking. Despite these detrimental impacts of MFS, there have been no attempts to characterize the effects of MFS on LE joint loading and health during walking that are associated with LE pain and dysfunction. As people with MFS exhibit a high incidence rate of osteoarthritis (OA), the need to understand the potential alterations in LE extremity mechanics …

Work-Related Changes In The Trunk Stiffness Of Nursing Personnel, Clare Tyler

Theses and Dissertations--Biomedical Engineering

Low back pain (LBP) is a significant issue related to spinal stability and, therefore, to trunk stiffness. Due to the nature of their work, nursing personnel are exposed to potential risk factors for LBP, such as lifting and trunk flexion, which have been reported in the literature to lead to decreases in trunk stiffness. Consequently, the purpose of this study was to investigate potential occupational effects on the trunk stiffness in nursing personnel. Twenty-four nursing personnel participated in this study and completed two sessions (pre-shift and post-shift) during which two passive flexion tests (with and without an ~7.5-lb load) were …

Knee Joint Loading Following Anterior Cruciate Ligament Reconstruction: Link To Patient Reported Outcomes And A Novel Method To Monitor With Wearable Sensors, Alex Spencer

Theses and Dissertations--Kinesiology and Health Promotion

Recovery from anterior cruciate ligament reconstruction (ACLR) commonly results in undesirable physical and patient-reported outcomes (PROs). Identification of modifiable factors such as knee contact force (KCF) early in rehabilitation that can improve these outcomes is important due to the rapid decrease in function, quality of life, and joint health in this population. Additionally, if noninvasive measurement of KCFs outside of a traditional laboratory were possible, clinicians could optimize patient treatment with personalized care. Therefore, there are two primary aims to this thesis: 1) quantify the link between KCF and PROs which measure pain, ability to perform activities of daily living, …

Atv Dynamics And Pediatric Rider Safety, James T. Auxier Ii

Theses and Dissertations--Biomedical Engineering

It has been observed through numerous academic and governmental agency studies that pediatric all-terrain vehicle ridership carries significant risk of injury and death. While no doubt valuable to safety, the post-hoc approach employed in these studies does little to explain the why and how behind the risk factors. Furthermore, there has been no prolonged, widespread, organized, and concerted effort to reconstruct and catalog the details and causes of the large (20,000+) number of ATV-related injuries that occur each year as has been done for road-based motor vehicle accidents. This dissertation takes the opposite approach from a meta-analysis and instead examines …

Work Related Diurnal Changes In Trunk Mechanical Behavior, Maeve Mcdonald

Theses and Dissertations--Biomedical Engineering

The objectives of this study were to analyze effects of day-long exposure to LBP risk factors on lumbo-pelvic coordination (LPC) in nursing occupations and to verify if physical activity level affects diurnal work-related changes in LPC. Thirty-three nurses were recruited into three groups based on workplace physical demands and each completed two data collection sessions, one before and one after their 8-12 hour work shift. Participants completed several stationary trunk forward-bending/backward-return exercises at self-selected “fast” and “slow” rotational speeds, and while holding a 15 lbs. load. Kinematic data collected during these exercises were then used to characterize the timing and …

Connecting The Pieces: How Low Back Pain Alters Lower Extremity Biomechanics And Shock Attenuation In Active Individuals, Alexa Johnson

Theses and Dissertations--Rehabilitation Sciences

Low back pain in collegiate athletes has been reported at a rate of 37% from a wide array of sports including soccer, volleyball, football, swimming, and baseball. Whereas, in a military population the prevalence of low back pain is 70% higher than the general population. Compensatory movement strategies are often used as an attempt to reduce pain. Though compensatory movement strategies may effectively reduce pain, they are often associated with altered lower extremity loading patterns. Those who suffer from chronic low back pain tend to walk and run slower and with less trunk and pelvis coordination and variability. Individuals with …

Biomechanical Effects Of A Hip Orthosis On Lumbo-Pelvic Coordination, Matthew Ballard

Theses and Dissertations--Biomedical Engineering

Abnormal lumbar movement has been observed in individuals who have a history of low back pain (LBP). Affected individuals display a reduction in lumbar spine rotation during trunk movement tasks, while pelvic rotation increases to compensate. Reduced lumbar contribution to forward bending is associated with increased compressive forces and increased shearing demand of the task on the lower back. This abnormal lumbo-pelvic coordination (LPC) can persist beyond LBP symptom alleviation and may contribute to further occurrences or more severe cases of LBP. This study serves as a first step in investigating if abnormal LPC can be corrected with a hip …

Quantification Of Myocardial Mechanics In Left Ventricles Under Inotropic Stimulation And In Healthy Right Ventricles Using 3d Dense Cmr, Zhan-Qiu Liu

Theses and Dissertations--Mechanical and Aerospace Engineering

Statistical data from clinical studies indicate that the death rate caused by heart disease has decreased due to an increased use of evidence-based medical therapies. This includes the use of magnetic resonance imaging (MRI), which is one of the most common non-invasive approaches in evidence-based health care research. In the current work, I present 3D Lagrangian strains and torsion in the left ventricle of healthy and isoproterenol-stimulated rats, which were investigated using Displacement ENcoding with Stimulated Echoes (DENSE) cardiac magnetic resonance (CMR) imaging. With the implementation of the 12-segment model, a detailed profile of regional cardiac mechanics was reconstructed for …

Effects Of Backpack Type On Kinematics Of The Lower Back During Walking And Jogging, Cazmon Suri

Theses and Dissertations--Biomedical Engineering

Heavy backpacks have been suggested to have a pathogenic role in experience of low back pain among children. We have conducted a repeated-measure study to investigate the backpack-induced changes in lumbo-pelvic coordination of forty gender-balanced college age students when they walked and jogged on a treadmill with two different types of backpacks: normal and ergonomically modified. The backpack-induced changes in lumbo-pelvic coordination were larger when carrying an ergonomically modified vs. a normal backpack as well as when jogging versus walking. The larger changes in lumbo-pelvic coordination when carrying an ergonomically modified backpack were likely due to kinematic restraints imposed by …

Design And Analysis Of A 3d-Printed, Thermoplastic Elastomer (Tpe) Spring Element For Use In Corrective Hand Orthotics, Kevin Thomas Richardson

Theses and Dissertations--Mechanical and Aerospace Engineering

This thesis proposes an algorithm that determine the geometry of 3D-printed, custom-designed spring element bands made of thermoplastic elastomer (TPE) for use in a wearable orthotic device to aid in the physical therapy of a human hand exhibiting spasticity after stroke. Each finger of the hand is modeled as a mechanical system consisting of a triple-rod pendulum with nonlinear stiffness at each joint and forces applied at the attachment point of each flexor muscle. The system is assumed quasi-static, which leads to a torque balance between the flexor tendons in the hand, joint stiffness and the design force applied to …

Age-Related Differences In The Lumbopelvic Kinematics During The Trunk Motions In The Anatomical Planes, Milad Vazirian

Theses and Dissertations--Biomedical Engineering

Management and control of the low back pain as an important health problem in the industrial societies necessitates to investigate how the risk of this disease is affected by aging. Since the abnormalities of the lumbopelvic kinematics are related to the existence or risk of low back injuries, the objective of this dissertation was set to find the age-related differences in lumbopelvic kinematics when performing basic trunk motions reaching to range of motion in different anatomical planes.

A cross-sectional study was designed where sixty asymptomatic individuals between 20–70 years old with no confounding health condition, no current or previous highly …

Three-Dimensional Endothelial Spheroid-Based Investigation Of Pressure-Sensitive Sprout Formation, Min Song

Theses and Dissertations--Biomedical Engineering

This study explored hydrostatic pressure as a mechanobiological parameter to control in vitro endothelial cell tubulogenesis in 3-D hydrogels as a model microvascular tissue engineering approach. For this purpose, the present investigation used an endothelial spheroid model, which we believe is an adaptable microvascularization strategy for many tissue engineering construct designs. We also aimed to identify the operating magnitudes and exposure times for hydrostatic pressure-sensitive sprout formation as well as verify the involvement of VEGFR-3 signaling. For this purpose, we used a custom-designed pressure system and a 3-D endothelial cell spheroid model of sprouting tubulogenesis. We report that an exposure …

The Rheological Impact Of Cell Activation On The Flow Behavior Of Neutrophils, Nolan M. Horrall

Theses and Dissertations--Biomedical Engineering

Previously, it was reported that the morphological changes (pseudopod projection) that circulating neutrophils adopt due to cell activation raises peripheral vascular resistance by disrupting microvascular rheology. Studies utilized murine muscle preparations to link neutrophil pseudopod formation to cell activation and a viscous impact on hemodynamic resistance. But because of the complexity associated with the organization of the vasculature and microvasculature in tissues, it was unclear whether the effects of neutrophil activation on hemodynamic resistance were associated with the macro-/micro- circulation. This research describes an in vitro analysis using viscometry and microvascular network mimics (microporous membranes) to assess the rheological impact …

Reference Point Indentation Of Human Trabecular Bone Treated With Bisphosphonates For Varying Durations, Drew Jones

Theses and Dissertations--Biomedical Engineering

Reference point indentation (RPI), a novel form of micro-indentation, quantifies RPI material parameters which correlate with modulus, yield stress, strength, or toughness. Information linking bisphosphonate treatment length with the material properties of osteoporotic trabecular bone is needed to improve patient treatment. The objectives of this study were to: 1) determine if RPI can be used to successfully evaluate human trabecular bone and if so, determine an optimized test method for using RPI on trabecular bone, and 2) use this method to determine if any RPI parameters are related to the duration of bisphosphonate treatment.

Indentation using a 4 N applied …

Collagen Crosslinking Reagent Utilized To Modify The Mechanical Properties Of The Soft Palate In Equine Snoring And Apnea Applications, Stephanie L. Hunt

Theses and Dissertations--Biomedical Engineering

Snoring is a sleep disruption that can lead to obstructive sleep apnea (OSA), which interrupts breathing by obstructing the airway. Injecting a protein crosslinker, such as genipin, into the soft palate could decrease the severity of snoring and OSA by stiffening the soft palate. Equine soft palates modeled human palates due to a high incidence of awake snoring and apnea.

The pilot in vivo study treated six horses with two 100 mM injections of the buffered genipin reagent. The efficacy phase horses underwent respiratory audio recordings to document snoring changes using Matlab and ImageJ in the time and frequency domains. …

The Effect Of Cholesterol On The Osteoblast Responsiveness To Hydrodynamic Pressure Stimulation, Kristen Lough

Theses and Dissertations--Biomedical Engineering

Hypercholesterolemia is a risk factor for osteoporosis but the underlying mechanism is unknown. Previous evidence suggests that osteoporosis results from an impaired regulation of osteoblasts by fluid pressure fluctuations in the bone matrix. Recently, our laboratory showed that enhanced cholesterol in the cell membrane, due to hypercholesterolemia, alters leukocyte mechanosensitivity. We predict a similar link between osteoblasts and hypercholesterolemia leading to osteoporosis. Specifically, we hypothesize that extracellular cholesterol modifies the osteoblast sensitivity to pressure. MC3T3-E1 cells were exposed to hydrodynamic pressures regimes (mean=40mmHg, amplitude=0-20mmHg, frequency=1Hz) for 1-12 hours. To assess the impact of membrane cholesterol enrichment, cells were pre-treated with …

Long Term Blood Oxygenation Membranes, Joseph V. Alexander

Theses and Dissertations--Biomedical Engineering

Hollow fiber membranes are widely used in blood oxygenators to remove carbon dioxide and add oxygen during cardiopulmonary bypass operations. These devices are now widely used off-label by physicians to perform extracorporeal blood oxygenation for patients with lung failure. Unfortunately, the hollow fiber membranes used in these devices fail prematurely due to blood plasma leakage and gas emboli formation.

This project formed ultrathin (~100nm) polymer coatings on polymer hollow fiber membranes. The coatings were intended to “block” existing pores on the exterior surfaces while permitting high gas fluxes. This coating is synthesized using surface imitated control radical polymerization.

The coating …

Body Armor Induced Changes In The Trunk Mechancial And Neuromuscular Behavior, Rebecca Leigh Tromp

Theses and Dissertations--Biomedical Engineering

While military body armor is used among warfighters for protection on and off the battlefield, it has been suggested to impede performance and act as a risk factor for the development of musculoskeletal disorders, especially low back pain. Apart from personal suffering, low back pain in soldiers is a great economic burden on the US economy. The objective of this study was to quantify the changes in trunk mechanical and neuromuscular behavior following prolonged exposure to body armor compared to exposure without. A crossover study design was used where 12 sex-balanced participants completed a series of tests before and after …

Computational Modeling Of Cardiac Biomechanics, Amir Nikou

Theses and Dissertations--Mechanical and Aerospace Engineering

The goal of this dissertation was to develop a realistic and patient-specific computational model of the heart that ultimately would help medical scientists to better diagnose and treat heart diseases. In order to achieve this goal, a three dimensional finite element model of the heart was created using magnetic resonance images of the beating pig heart. This model was loaded by the pressure of blood inside the left ventricle which was measured by synchronous catheterization. A recently developed structurally based constitutive model of the myocardium was incorporated in the finite element solver to model passive left ventricular myocardium. Additionally, an …

Relationships Of Long-Term Bisphosphonate Treatment With Measures Of Bone Microarchitecture And Mechanical Competence, Jonathan Joseph Ward

Theses and Dissertations--Biomedical Engineering

Oral bisphosphonate drug therapy is a common and effective treatment for osteoporosis. Little is known about the long-term effects of bisphosphonates on bone quality. This study examined the structural and mechanical properties of trabecular bone following 0-16 years of bisphosphonate treatment. Fifty-three iliac crest bone samples of Caucasian women diagnosed with low turnover osteoporosis were identified from the Kentucky Bone Registry. Forty-five were treated with oral bisphosphonates for 1 to 16 years while eight were treatment naive. A section of trabecular bone was chosen from a micro-computed tomography (Scanco µCT 40) scan of each sample for a uniaxial linearly elastic …

The Effects Of Hydrostatic Pressure On Early Endothelial Tubulogenic Processes, Ryan M. Underwood

Theses and Dissertations--Biomedical Engineering

The effects of mechanical forces on endothelial cell function and behavior are well documented, but have not been fully characterized. Specifically, fluid pressure has been shown to elicit physical and chemical responses known to be involved in the initiation and progression of endothelial cell-mediated vascularization. Central to the process of vascularization is the formation of tube-like structures. This process—tubulogenesis—is essential to both the physiological and pathological growth of tissues. Given the known effects of pressure on endothelial cells and its ubiquitous presence in the vasculature, we investigated pressure as a magnitude-dependent parameter for the regulation of endothelial tubulogenic activity. To …

Bisphosphonates And Bone Microdamage, William A. Caruthers

Theses and Dissertations--Biomedical Engineering

Osteoporosis is a significant healthcare issue due to the increasing elderly population. Bisphosphonates are used to treat osteoporosis by reducing the rate of resorption, increasing bone mineral density (BMD) and thereby reducing fracture risk. Long-term bisphosphonate treatment, however, has been associated with low-energy fractures. Bone microdamage may provide a partial explanation for one of the mechanisms responsible for these fractures since it has been shown to reduce bone toughness, fracture resistance, and bone strength. The goal of this study was to quantify the changes in bone microdamage parameters with the duration of bisphosphonate treatment. This study selected, stained, and histomorphometrically …

Distal Radioulnar Joint Biomechanics And Forearm Muscle Activity, Joseph Scott Bader

University of Kentucky Doctoral Dissertations

Optimal management of fractures, post-traumatic arthritis and instability of the distal radioulnar joint (DRUJ) requires an understanding of the forces existing across this joint as a function of the activities of daily living. However, such knowledge is currently incomplete. The goal of this research was to quantify the loads that occur at the DRUJ during forearm rotation and to determine the effect that individual muscles have on those loads.

Human and cadaver studies were used to analyze the shear (A-P), transverse (M-L) and resultant forces at the DRUJ and to determine the role that 15 individual muscles had on those …