The standard electrical stimulation waveform used for electrical activation of nerve is a rectangular pulse or a charge balanced rectangular pulse, where the pulse width is typically in the range of ∼100 µsec through ∼1000 µsec. In this work, we explore the effects of a continuous sinusoidal waveform with a frequency ranging from 5 through 20 Hz, which was named the Low Frequency Alternating Current (LFAC) waveform. The LFAC waveform was explored in the Bioelectronics Laboratory as a novel means to evoke nerve block. However, in an attempt to evoke complete nerve block on a somatic motor nerve, increasing the amplitude of the LFAC waveform unexpectedly produced nerve activation, and elicited a strong non-fatiguing muscle contraction in the anesthetized rabbit model (unpublished observation). The present thesis aimed to further explore the phenomenon to measure the effect of LFAC waveform frequency and amplitude on nerve activation.<div><br></div><div>In freshly excised canine cervical vagus nerve (n=3), it was found that the LFAC waveform at 5, 10, and 20 Hz produced burst modulated activity. Compound action potentials (CAP) synchronous to the stimuli was absent from the electroneurogram (ENG) recordings. When applied <i>in-vivo</i>, LFAC was capable of activating the cervical vagus nerve fibers in anaesthetized swine (n=5) and induced the Hering-Breuer reflex. Additionally, when applied <i>in-vivo</i> to anesthetized Sprague Dawley rats (n=4), the LFAC waveform was able to activate the left sciatic nerve fibers and induced muscle contractions.</div><div><br></div><div>The results demonstrate that LFAC activation was stochastic, and asynchronous to the stimuli unlike conventional pulse stimulation where nerve and muscle response simultaneously and synchronously to stimulus. The activation thresholds were found to be frequency dependent. As the waveform frequency increases the required current amplitude decreases. These experiments also implied that the LFAC phenomenon was most likely to be fiber type-size dependent but that more sophisticated exploration should be addressed before reaching clinical applications. In all settings, the LFAC amplitude was within the water window preventing irreversible electrochemical reactions and damages to the cuff electrodes or nerve tissues. This thesis also reconfirms the preliminary LFAC activation discovery and explores multiple methods to evaluate the experimental observations, which suggest the feasibility of the LFAC waveform at 5, 10, and 20 Hz to activate autonomic and somatic nerve fibers. LFAC appears to be a promising new technique to activate peripheral nerve fibers.</div>

Energy densities (ED, mJ/mm3) quantify mechanical work imposed on articular cartilages during function. This cross-sectional study examined differences in temporomandibular joint (TMJ) ED during asymmetric versus symmetric jaw closing in healthy females versus males. ED component variables were tested for differences between and within sexes for two types of jaw closing. Seventeen female and 17 male subjects gave informed consent to participate. Diagnostic criteria for temporomandibular disorders and images (magnetic resonance (MR), computed tomography) were used to confirm healthy TMJ status. Numerical modelling predicted TMJ loads (Fnormal) consequent to unilateral canine biting. Dynamic stereometry combined MR imaging and jaw-tracking data to measure ED component variables during 10 trials of each type of jaw closing in each subject's TMJs. These data were then used to calculate TMJ ED during jaw closing asymmetrically and symmetrically. Paired and Student's t tests assessed ED between jaw closing movements and sexes, respectively. Multivariate data analyses assessed ED component variable differences between jaw closing movements and sexes (α = 0.05). Contralateral TMJ ED were 3.6-fold and significantly larger (P <.0001) during asymmetric versus symmetric jaw closing, due to significantly larger (P ≤.001) distances of TMJ stress-field translation in asymmetric versus symmetric movement. During asymmetric jaw closing, contralateral TMJ ED were twofold and significantly larger (P =.036) in females versus males, due to 1.5-fold and significantly smaller (P ≤.010) TMJ disc cartilage volumes under stress fields in females versus males. These results suggest that in healthy individuals, asymmetric compared to symmetric jaw closure in females compared to males has higher TMJ mechanical fatigue liabilities.

The primary objective of this biomechanical study was to investigate the effect of decompressive surgery, specifically dorsal laminectomy and discectomy, on the stability of the lumbosacral joint in the dog. Different size laminectomies were compared with respect to their effect on lumbosacral stability. A total of eighteen lumbosacral motion units were collected from cadavers and divided into three groups. Group 1 was a control group and received no modification, Group 2 specimens received mini-dorsal laminectomies and discectomies (lamina of L7 caudal to the dorsal spinous process excised, lamina of S1 not affected) while Group 3 specimens received standard dorsal laminectomies and discectomies (75% of L7 lamina and 50% of S1 lamina excised). All specimens were potted in aluminium tubing and mounted in a four-point bending jig and tested in a load cell. Specimens were stressed to 21° in dorsiflexion and ventroflexion. The relevant surgical modification was then performed and the specimens re-tested to 21° in dorsiflexion and ventroflexion. All specimens were then tested to failure in ventroflexion. Force and angular displacement was recorded and used to obtain load-deformation curves for each specimen (5 curves for each specimen). From the load-deformation curves the stiffness (gradient of the graph) was determined at three set angles of deflection. These points were 6°-8°, 12°-16° and 18°-20°. The percentage change in stiffness for each specimen in both dorsiflexion and ventroflexion was obtained. Peak force at failure and angular deformation at failure were obtained when tested to failure in ventroflexion. When examining the overall stiffness of the specimen (dorsiflexion and ventroflexion and all angles of deflection) mini-dorsal laminectomy was shown to result in a 48.3% reduction in stiffness (P < 0.001) while standard dorsal laminectomy and discectomy resulted in a 59.8% reduction in stiffness (P < 0.001). These results were statistically significant. The difference between the two different types of laminectomies could be described as approaching significance (P=0.066). Larger group size would be required to determine whether this is in fact statistically significant Dorsal laminectomy combined with discectomy does have an effect on the stability of the lumbosacral joint. This may contribute to the relatively high recurrence rate following surgical treatment of degenerative lumbosacral stenosis especially in large breed highly active dogs. The study provides further support for decompressive surgery combined with a stabilisation technique when treating degenerative lumbosacral stenosis. It also provides potential support for the use of mini-dorsal laminectomies. / Dissertation (MMedVet)--University of Pretoria, 2009. / Companion Animal Clinical Studies / unrestricted

The development of wearable devices to monitor biosignals and collect real-time data from biological systems at all scales from cellular to organ level has played a significant role in the field of medical engineering. The current coronavirus disease 2019 (COVID-19) pandemic has further increased the demand for remote monitoring and smart healthcare where patient data can be also be accessed from a remote distance. Recent efforts to integrate wearable devices with artificial intelligence and machine learning have transformed conventional healthcare into smart healthcare, which requires reliable and robust recording data. The biomedical devices that are mechanically stretchable and compliant have provided the capability to form a seamless interface with the curvilinear, soft surface of tissues and body, enabling accurate, continuous acquisition of physical and electrophysiological signals. This dissertation presents a comprehensive set of functional materials, design principles, and fabrication strategies to develop mechanically stretchable and compliant biomedical devices tailored for various applications, including (1) a stretchable sensor patch enabling the continuous monitoring of swallowing function from the submental/facial area for the telerehabilitation of patients with dysphagia, (2) a human hand-like sensory glove for advanced control of prosthetic hands, (3) a mechanically compliant manipulator for the non-invasive handling of delicate biomaterials and bioelectronics, and (4) a stretchable sensors embedded inside a tissue scaffold enabling the continuous monitoring of cellular electrophysiological behavior with high spatiotemporal resolution.<br>

The research presented in this thesis focuses on understanding the biomechanical effects of various cranial features that are often ignored in finite element models (FEMs) because their size, position, and complex shapes make them difficult to model. Specifically, this work examines the effects of the alveoli (tooth sockets), periodontal ligament, and squamosal suture on the stress and strain distributions in a cranium under masticatory and dynamic tooth loads. Results from this research will help determine if these features have a significant effect on stress and strain patterns and will yield guidelines as to if or under what conditions they need to be modeled in future FE skull model analyses. As part of this research, three sets of FEMs were developed to address a hypothesis focusing on each cranial feature. The first set of models examined the effect of the tooth sockets on the stress and strain distributions in a cranium under static biting conditions to determine if improperly modeled sockets produce strong global effects in craniofacial regions. The second set of models were used to assess the effect of the PDL's material behavior on the stresses and strains in a cranium under static biting and dynamic tooth loading conditions to determine if the PDL plays an important role in reducing stresses and strains in a model. The final set of models were used to determine the effect of the squamosal suture size on the stresses and strain energies in a cranium under static biting conditions to see if an increase in suture size decreases the risk of separation of the temporal bone from the parietal bone. Results for all analyses indicate the effects of the cranial features are local (i.e. within the vicinity of the feature), with no meaningful global effects. This suggests the sockets, PDL, and squamosal suture do not play an important role in global stress and strain distributions in a cranium under masticatory and dynamic tooth loads. Therefore, it may be safe to ignore the sockets, PDLs, and squamosal sutures during the FE modeling process if the objective of the analysis is to understand global stress and strain patterns.

Hydrocephalus is developed when the flow of cerebrospinal fluid is obstructed in the ventricles and a pressure build-up is generated within the brain. Ventricular shunts are used to remove excess fluid from the brain, but these shunts have a common problem of failure due to the shunt being obstructed by the build-up of astrocytes. To address this, two sets of 27 designs of ventricular shunts were identified and analyzed with parameters that could potentially reduce obstruction risks. The performance of these designs was examined using fluid simulations on these two sets of 27 designs. One set explored close-tipped shunt designs, and the other assessed open-tipped ones. Following these simulations, adjustments were made to three design variables of the ventricular catheters - inlet hole size, inner shunt diameter, and inner-segment distance. The goal was to optimize these variables to prevent obstruction, ensuring three key design objectives were met: maintaining wall shear stress, ensuring a balanced inlet and outlet pressure difference, and achieving a uniform flow distribution.

The aim of this study was two-fold: 1) what the hammer throwing technique differences between sexes are and 2) what technique parameters help determine throw distance. The performances of the top 16 male and female throwers at the 2003 World Athletic Final and the top 13 male and female throwers from the 2003 USA Track and Field Nationals were examined. Video was captured using three Canon 60 Hz cameras. The best throws of each athlete were digitized and analyzed using the Peak Motus 8.2 motion analysis system. T-tests revealed that athlete mass, athlete height, velocity at release, timing components, and centripetal force were different between sexes. The separation between the shoulders and hips and between the shoulders and the hammer at particular positions during the throw, radius changes at certain phases of the throw, and generation of large centripetal forces helped determine throwing distance. Performance would be aided by working on the development of centripetal force, the magnitude of radius changes, the separation that occurs between the shoulders and hips, and the separation between the shoulders and hammer.

An estimated 27 million Americans suffer from osteoarthritis (OA). Symptomatic OA is often treated with total knee replacement, a procedure which is expected to increase in number by 673% from 2005 to 2030, and costs to perform total knee replacement surgeries exceeded $11 billion in 2005. Subject-specific modeling and finite element (FE) predictions are state-of-the-art computational methods for anatomically accurate predictions of joint tissue loads in surgical-planning and rehabilitation. Knee joint FE models have been used to predict in-vivo joint kinematics, loads, stresses and strains, and joint contact area and pressure. Abnormal cartilage contact pressure is considered a risk factor for incidence and progression of OA. For this study, three subject-specific tibiofemoral knee FE models containing accurate geometry were developed from magnetic resonance images (MRIs). Linear (LIN), Neo-Hookean (NH), and poroelastic (PE) cartilage material models were implemented in each FE model for each subject under three loading cases to compare cartilage contact pressure predictions at each load case. An additional objective was to compare FE predictions of cartilage contact pressure for LIN, NH, and PE material models with experimental measurements of cartilage contact pressure. Because past studies on FE predictions of cartilage contact pressure using different material models and material property values have found differences in cartilage contact pressure, it was hypothesized that different FE predictions of cartilage contact pressure using LIN, NH, and PE material models for three subjects at three different loading cases would find statistically significant differences in cartilage contact pressure between the material models. It was further hypothesized that FE predictions of cartilage contact pressure for the PE cartilage material model would be statistically similar to experimental data, while the LIN and NH cartilage material models would be significantly different for all three loading cases. This study found FE and experimental measurements of cartilage contact pressure only showed significant statistical differences for LIN, NH, and PE predictions in the medial compartment at 1000N applied at 30 degrees, and for the PE prediction in the medial compartment at 500N applied at 0 degrees. FE predictions of cartilage contact pressure using the PE cartilage material model were considered less similar to experimental data than the LIN and NH cartilage material models. This is the first study to use LIN, NH, and PE material models to examine knee cartilage contact pressure predictions using FE methods for multiple subjects and multiple load cases. The results demonstrated that future subject specific knee joint FE studies would be advised to select LIN and NH cartilage material models for the purpose of making FE predictions of cartilage contact pressure.

With the increasing longevity that accompanies advances in medical technology comes a host of other age-related disabilities. Among these are neuro-degenerative diseases such as Alzheimer's disease, Parkinson's disease, and stroke, which significantly reduce the motor and cognitive ability of affected individuals. As these diseases become more prevalent, there is a need for further research and innovation in the field of motor rehabilitation therapy to accommodate these individuals in a cost-effective manner. In recent years, the implementation of social agents has been proposed to alleviate the burden on in-home human caregivers. Socially assistive robotics (SAR) is a new subfield of research derived from human-robot interaction that aims to provide hands-off interventions for patients with an emphasis on social rather than physical interaction. As these SAR systems are very new within the medical field, there is no standardized approach to developing such systems for different populations and therapeutic outcomes. The primary aim of this project is to provide a standardized method for developing such systems by introducing a modular human-robot interaction software framework upon which future implementations can be built. The framework is modular in nature, allowing for a variety of hardware and software additions and modifications, and is designed to provide a task-oriented training structure with augmented feedback given to the user in a closed-loop format. The framework utilizes the ROS (Robot Operating System) middleware suite which supports multiple hardware interfaces and runs primarily on Linux operating systems. These design requirements are validated through testing and analysis of two unique implementations of the framework: a keyboard input reaction task and a reaching-to-grasp task. These implementations serve as example use cases for the framework and provide a template for future designs. This framework will provide a means to streamline the development of future SAR systems for research and rehabilitation therapy.

When conducting motion analysis using 3-dimensional motion capture technology, errors in marker placement on the knee results in a widely observed phenomenon known as “crosstalk” [1-18] in calculated knee joint angles (i.e., flexion-extension (FE), adduction-abduction (AA), internal-external rotation (IE)). Principal Component Analysis (PCA) has recently been proposed as a post hoc method to reduce crosstalk errors and operates by minimizing the correlation between the knee angles [1, 2]. However, recent studies that have used PCA have neither considered exercises, such as cycling (C) and elliptical training (E), other than gait (G) nor estimated the corrected knee axes following PCA correction. The hypothesis of this study is that PCA can correct for crosstalk in G, C, and E exercises but that subject-specific PCA corrected axes differ for these exercises. Motion analysis of the selected exercises were conducted on 8 normal weight (body mass index (BMI) = 21.70 +/- 3.20) and 7 overweight participants (BMI = 27.45 +/- 2.45). An enhanced Helen Hayes marker set with 27 markers was used to track kinematics. Knee joint FE, AA, and IE angles were obtained with Cortex (Motion Analysis, Santa Rosa, CA) software and corrected using PCA to obtain corrected angles for each exercise. Exercise-specific corrected knee joint axes were determined by finding axes that reproduced the shank and ankle body vectors taken from Cortex when used with the PCA corrected angles. Then, PCA corrected gait axes were used as a common set of axes for all exercises to find corresponding knee angles. Paired t-tests assessed if FE-AA angle correlations changed with PCA. Multivariate Paired Hotelling’s T-Square tests assessed if the PCA corrected knee joint axes were similar between exercises. ANOVA was used to assess if Cortex angles, PCA corrected angles, and knee angles using PCA corrected gait axes were different. Reduced FE-AA angle correlations existed for G (p<0.001 for Cortex and p=0.85 for PCA corrected), C (p=0.01 for Cortex and p=0.77 for PCA corrected), and E (p<0.001 for Cortex and p=0.77 for PCA corrected). Differences in the PCA corrected knee axes were found between G and C (p<0.0014). Then, differences were found between Cortex, PCA corrected, and C and E knee angles using the PCA corrected G axes (p<0.0056). The results of this study suggest that if PCA is used to reduce crosstalk errors in motions other than G then it is recommended to adopt the use of a PCA corrected axes set determined from G to produce the PCA corrected angles.