Statistical data suggests that increased use of evidence-based medical therapies has largely contributed to the decrease in American death rate caused by heart disease. And my studies are about two applications of magnetic resonance imaging (MRI) as a non-invasive approach in evidence-based health care research. In my first study, the achievement of a pulmonary valve replacement surgery was assessed on a patient with tetralogy of Fallot (TOF). In order to evaluate the remodeling of right ventricle, two biventricular finite element models were built up for pre-surgical images and post-surgical images. In my second study, 3D Lagrangian strains and torsion in the left ventricle of ten rats were investigated using Displacement ENcoding with Stimulated Echoes (DENSE) cardiac magnetic resonance (CMR) images. Tools written in MATLAB were developed for 2D contouring, 3D modeling, strain and torsion computations, and statistical comparison across subjects.

Limited knowledge of the neuromechanical response to use of an ankle foot orthosis-footwear combination (AFO-FC) has created a lack of consensus in understanding orthotic motion control as a therapeutic treatment. Lack of consensus may hinder the clinician’s ability to target the motion control needs of persons with movement impairment (e.g., peripheral nerve injury, stroke, etc.). Some evidence suggests a proportional relationship between joint motion and neuromuscular activity based on the notion that use of lower limb orthoses that constrain joint motion may invoke motor slacking and decreasing levels of muscle activity. Use of AFO-FCs likely alters the biomechanical and neuromuscular output as the central control system gradually forms new movement patterns. If there is proportional relationship between muscle activation and joint motion, then it could be examined by quantifying joint motion and subsequent neuromuscular output. Considering principles of neuromechanical adjustment, my general hypothesis examines whether orthotic control of lower limb motion alters neuromuscular output in proportion to the biomechanical output as a representation of the limb’s dynamics are updated by the neural control system. The rationale for this approach is that reference knowledge of the neuromechanical response is needed to inform clinicians about how a person responds to walking with motion controlling devices such as ankle foot orthoses combined with footwear. In the first line of research, I hypothesize that a newly developed AFO which maximizes leverage and stiffness will constrain the talocrural joint and alter joint kinematics and ground reaction force patterns. To answer the hypothesis, I sampled kinematics and kinetics of healthy subjects’ treadmill walking using an AFO-FC in a STOP condition and confirmed that the AFO substantially limited the range of talocrural plantarflexion and dorsiflexion motion to 3.7° and in a FREE condition maintained talocrural motion to 24.2° compared to 27.7° in a CONTROL (no AFO) condition. A follow up controlled static loading study sampled kinematics of matched healthy subjects limbs and cadaveric limbs in the AFO STOP and FREE conditions. Findings revealed healthy and cadaveric limbs in the AFO STOP condition substantially limited their limb segment motion similar to matched healthy subjects walking in the STOP condition and in the AFO FREE condition healthy and cadaveric limbs maintained similar limb segment motion to matched healthy subjects walking in the FREE condition. In a second line of research, I hypothesize that flexibility of a newly developed footwear system will allow normal walking kinetics due to the shape and flexibility of the footwear. To answer the hypothesis, I utilized a curved-flexible footwear system integrated with an AFO in a STOP condition and sampled kinematics and kinetics of healthy subjects during treadmill walking. Results revealed subjects elicited similar cadence, stance and swing duration and effective leg-ankle-foot roll over radius compared to walking in the curved-flexible footwear integrated with the AFO in a FREE condition and a CONTROL (no AFO) condition. To validate rollover dynamics of the curved-flexible footwear system, a follow up study of healthy subjects’ treadmill walking in newly developed flat-rigid footwear system integrated with the AFO in a STOP condition revealed interrupted leg-ankle-foot rollover compared to walking in curved-flexible footwear in STOP, FREE and CONTROL conditions. In a third line of research, I hypothesize that use of an AFO that limits talocrural motion in a STOP condition will proportionally reduce activation of Tibialis Anterior, Soleus, Medial and Lateral Gastrocnemii muscles compared to a FREE and CONTROL condition due to alterations in length dependent representation of the limb’s dynamics undergoing updates to the central control system that modify the pattern of motor output. To answer the question, the same subjects and AFO-footwear presented in the first two lines of research were used in a treadmill walking protocol in STOP, FREE, and CONTROL conditions. Findings revealed the same subjects and ipsilateral AFO-footwear system presented in Aim 1 exhibited an immediate yet moderate 30% decline in EMG activity of ipsilateral Soleus (SOL), Medial Gastrocnemius (MG) and Lateral Gastrocnemius (LG) muscles in the STOP condition compared to the CONTROL condition. The reduction in EMG activity in ipsilateral SOL, MG and LG muscles continued to gradually decline during 15 minutes of treadmill walking. On the contralateral leg, there was an immediate yet small increase of 1% to 14% in EMG activity in SOL, MG, LG muscles above baseline. After 10 minutes of walking, the EMG activity in contralateral SOL, MG and LG declined to a baseline level similar to the EMG activity in the contralateral CONTROL condition. These collective findings provide compelling evidence that the moderate 30% reduction in muscle activation exhibited by subjects as they experience substantial (85%) constraint of total talocrural motion in the AFO STOP condition is not proportionally equivalent. Further, the immediate decrease in muscle activation may be due to a reactive feedback mechanism whereas the continued decline may in part be explained by a feedforward mechanism. The clinical relevance of these findings suggests that short term use of orthotic constraint of talocrural motion in healthy subjects does not substantially reduce muscle activation. These preliminary findings could be used to inform the development of orthoses and footwear as therapeutic motion control treatments in the development of motor rehabilitation protocols.

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. Histological analysis was completed on the safety phase palates post treatment. All horses were successfully treated with the genipin injections. At least one horse showed high frequency amplitude reductions, and all horses had low frequency amplitude reductions, correlating to a reduction in palatal displacement and snoring loudness. One efficacy horse appears to have been completely cured. The histological analysis presented tissue damage, mucosal tissue damage, and mild inflammation due to palate expansion and errant injections. Different injection volumes and techniques should be investigated next. Applying this treatment to human studies for snoring and OSA applications is the ultimate goal.

This project investigas humeral torsion and activity-related change in the human upper limb. Increased humeral torsion angles have been identified in the professional throwing athlete and may be associated with strenuous activity. The nature of humeral torsion as an osteogenic response to the strain environment is investigated to identify its role in the behavioural morphology of the upper limb. These physical manifestations of strenuous physical activity provide an insight into the make-up of medieval armies prior to the establishment of standing armies. Populations analysed include two blade-injured samples, Towton and a subsample of blade-injured men from the Priory of St. Andrew, Fishergate, York. The men from the Mary Rose, a Tudor warship are also investigated. Other samples analysed include the rural sites of Wharram Percy and Hickleton, the urban cemeteries from the Priory of St. Andrew, Fishergate,York and the leprosarium of Sts. James and Mary Magdalene, Chichester, the modern cadaver-based Terry collection and non-human primates, Gorilla sp., Pan sp., Pongo sp., and Macaca sp.. Measurement of the humeral torsion angle and external measurements and indices of architecture, articulations and robusticity are employed. Cross-sectional geometric properties are investigated using CT imaging of the paired humeri from a sub-sample of blade-injured individuals and a comparative sample of those who were not. Bilateral asymmetry is investigated to identify the role of plasticity within the humerus and to reveal aspects of limb dominance. The results are compared with non-human primate species to obtain insight into inter-species differences. Results indicate the humeral torsion is not ontogenetically constrained, but is highly variable between and within populations, individuals and even between sides. Biomechanical analyses indicate that in the Towton population, humeral torsion may serve as part of a two-stage adaptation, in which the architecture is modified to enable greater biomechanical efficiency in distributing strain, reducing the need of increased cortical thickness. Changes in humeral torsion related to strenuous activity have been identified, although in the blade-injured samples it is decreased torsion angles, w hile in the comparative sample it is increased torsion angles that significantly correlate with limb hypertrophy. Humeral torsion appears to be influenced by other measurementd of humeral architecture, specifically, the amount of anterior bowing and anterior curvature to the distal humeral shaft. This work demonstrates the need for individual rather than population-based analyses, as the heterogeneity within population samples obscures individual variation in activity patterns. This analysis provides baseline data for typical populations of the Middle Ages. From this, it is then possible to investigate the individual within this baseline, to identify those who stand out from their samples through habitual, strenuous activity patterns. Movement patterns identified related to warfare include those consistent with the use of the longbow in the Towton sample and the use of a sword in the Fishergate blade-injured sample. These men, and those of the Mary Rose, appear to have either been selected for combat based on size, or benefited from a more nutritious diet during growth.

Submitted in partial compliance with the requirements for the Master’s Degree in Technology: Chiropractic, Durban University of Technology, 2014. / Background: Classical ballet is an art form that seems graceful on the surface. However, beneath the disguise of beauty and ease lies an extremely physically demanding activity that calls for dedication, strength and perseverance. Ballet requires a specific body type and precise techniques, which predispose the dancer to musculoskeletal injury. Although a few studies have been conducted to investigate biomechanical factors as risk factors for injury in ballet dancers, few have included amateur ballet dancers and a range of biomechanical factors. Objectives: This study aimed to determine characteristics of ballet-related injury in amateur ballet dancers in the greater Durban area; to measure and record lower limb biomechanical measurements of these dancers; and to identify associations between the biomechanical measurements and characteristics of injury in the population. Method: A quantitative, questionnaire-based survey with biomechanical measurements was conducted on 21 amateur ballet dancers in the greater Durban area. Statistical analysis included the description of categorical variables using frequency and percentages in tables and bar charts. Continuous variables were summarised using mean, standard deviation and range, or median and range as appropriate. Independent Sample T-tests were used to compare biomechanical measurements between two independent groups. A p value <0.05 was considered as statistically significant. Pearson’s correlations and ANOVA testing were also used. Results: The period prevalence of ballet-related injury over the last 2 years was found to be 62% and the point prevalence 38%. There were 37 total previous injuries, most of which occurred in the hamstring (24%). Most of the worst previous injuries were reported to have occurred in the low back (31%). Most of the worst previous (70%) and current (93%) injuries occurred over time. The worst previous injuries reported ranged from mild to severe in severity, while the worst current injuries reported ranged from mild to moderate. Significant associations were found between right weight-bearing ankle dorsiflexion and previous injury; right weight-bearing ankle dorsiflexion and current injury; ‘functional turnout’ and onset of injury; right non weight-bearing ankle dorsiflexion and onset of injury; and ‘compensated turnout’ and onset of injury. Conclusion: The results suggest a significant association between musculoskeletal ballet-related injury and reduced weight-bearing ankle dorsiflexion; between injuries that occur over time (overuse injuries) and decreased ‘functional turnout’; and between overuse injuries and decreased non weight-bearing ankle dorsiflexion. These findings may help identify risk factors for injury in ballet dancers and contribute towards preventing ballet-related injury. / M

L’élastographie est une technique d’imagerie qui vise à cartographier in vivo les propriétés mécaniques des tissus biologiques dans le but de fournir des informations diagnostiques additionnelles. Depuis son introduction en imagerie ultrasonore dans les années 1990, l’élastographie a trouvé de nombreuses applications. Cette modalité a notamment été utilisée pour l’étude du sein, du foie, de la prostate et des artères par imagerie ultrasonore, par résonance magnétique ou en tomographie par cohérence optique. Dans le contexte des maladies cardiovasculaires, cette modalité a un fort potentiel diagnostique puisque l’athérosclérose modifie la structure des tissus biologiques et leurs propriétés mécaniques bien avant l’apparition de tout symptôme. Quelle que soit la modalité d’imagerie utilisée, l’élastographie repose sur : l’excitation mécanique du tissu (statique ou dynamique), la mesure de déplacements et de déformations induites, et l’inversion qui permet de recouvrir les propriétés mécaniques des tissus sous-jacents. Cette thèse présente un ensemble de travaux d’élastographie dédiés à l’évaluation des tissus de l’appareil cardiovasculaire. Elle est scindée en deux parties. La première partie intitulée « Élastographie vasculaire » s’intéresse aux pathologies affectant les artères périphériques. La seconde, intitulée « Élastographie cardiaque », s’adresse aux pathologies du muscle cardiaque. Dans le contexte vasculaire, l’athérosclérose modifie la physiologie de la paroi artérielle et, de ce fait, ses propriétés biomécaniques. La première partie de cette thèse a pour objectif principal le développement d’un outil de segmentation et de caractérisation mécanique des composantes tissulaires (coeur lipidique, tissus fibreux et inclusions calciques) de la paroi artérielle, en imagerie ultrasonore non invasive, afin de prédire la vulnérabilité des plaques. Dans une première étude (Chapitre 5), nous présentons un nouvel estimateur de déformations, associé à de l’imagerie ultrarapide par ondes planes. Cette nouvelle méthode d’imagerie permet d’augmenter les performances de l’élastographie non invasive. Dans la continuité de cette étude, on propose une nouvelle méthode d’inversion mécanique dédiée à l’identification et à la quantification des propriétés mécaniques des tissus de la paroi (Chapitre 6). Ces deux méthodes sont validées in silico et in vitro sur des fantômes d’artères en polymère. Dans le contexte cardiaque, les ischémies et les infarctus causés par l’athérosclérose altèrent la contractilité du myocarde et, de ce fait, sa capacité à pomper le sang dans le corps (fonction myocardique). En échocardiographie conventionnelle, on évalue généralement la fonction myocardique en analysant la dynamique des mouvements ventriculaires (vitesses et déformations du myocarde). L’abscence de contraintes physiologiques agissant sur le myocarde (contrairement à la pression sanguine qui contraint la paroi vasculaire) ne permet pas de résoudre le problème inverse et de retrouver les propriétés mécaniques du tissu. Le terme d’élastographie fait donc ici référence à l’évaluation de la dynamique des mouvements et des déformations et non à l’évaluation des propriétés mécanique du tissu. La seconde partie de cette thèse a pour principal objectif le développement de nouveaux outils d’imagerie ultrarapide permettant une meilleure évaluation de la dynamique du myocarde. Dans une première étude (Chapitre 7), nous proposons une nouvelle approche d’échocardiographie ultrarapide et de haute résolution, par ondes divergentes, couplée à de l'imagerie Doppler tissulaire. Cette combinaison, validée in vitro et in vivo, permet d’optimiser le contraste des images mode B ainsi que l’estimation des vitesses Doppler tissulaires. Dans la continuité de cette première étude, nous proposons une nouvelle méthode d’imagerie des vecteurs de vitesses tissulaires (Chapitre 8). Cette approche, validée in vitro et in vivo, associe les informations de vitesses Doppler tissulaires et le mode B ultrarapide de l’étude précédente pour estimer l’ensemble du champ des vitesses 2D à l’intérieur du myocarde. / Elastography is an imaging technique that aims to map the in vivo mechanical properties of biological tissues in order to provide additional diagnostic information. Since its introduction in ultrasound imaging in the 1990s, elastography has found many applications. This method has been used for the study of the breast, liver, prostate and arteries by ultrasound imaging, magnetic resonance imaging (MRI) or optical coherence tomography (OCT). In the context of cardiovascular diseases (CVD), this modality has a high diagnostic potential as atherosclerosis, a common pathology causing cardiovascular diseases, changes the structure of biological tissues and their mechanical properties well before any symptoms appear. Whatever the imaging modality, elastography is based on: the mechanical excitation of the tissue (static or dynamic), the measurement of induced displacements and strains, and the inverse problem allowing the quantification of the mechanical properties of underlying tissues. This thesis presents a series of works in elastography for the evaluation of cardiovascular tissues. It is divided into two parts. The first part, entitled « Vascular elastography » focuses on diseases affecting peripheral arteries. The second, entitled « Cardiac elastography » targets heart muscle pathologies. In the vascular context, atherosclerosis changes the physiology of the arterial wall and thereby its biomechanical properties. The main objective of the first part of this thesis is to develop a tool that enables the segmentation and the mechanical characterization of tissues (necrotic core, fibrous tissues and calcium inclusions) in the vascular wall of the peripheral arteries, to predict the vulnerability of plaques. In a first study (Chapter 5), we propose a new strain estimator, associated with ultrafast plane wave imaging. This new imaging technique can increase the performance of the noninvasive elastography. Building on this first study, we propose a new inverse problem method dedicated to the identification and quantification of the mechanical properties of the vascular wall tissues (Chapter 6). These two methods are validated in silico and in vitro on polymer phantom mimicking arteries. In the cardiac context, myocardial infarctions and ischemia caused by atherosclerosis alter myocardial contractility. In conventional echocardiography, the myocardial function is generally evaluated by analyzing the dynamics of ventricular motions (myocardial velocities and deformations). The abscence of physiological stress acting on the myocardium (as opposed to the blood pressure which acts the vascular wall) do not allow the solving the inverse problem and to find the mechanical properties of the fabric. Elastography thus here refers to the assessment of motion dynamics and deformations and not to the evaluation of mechanical properties of the tissue. The main objective of the second part of this thesis is to develop new ultrafast imaging tools for a better evaluation of the myocardial dynamics. In a first study (Chapter 7), we propose a new approach for ultrafast and high-resolution echocardiography using diverging waves and tissue Doppler. This combination, validated in vitro and in vivo, optimize the contrast in B-mode images and the estimation of myocardial velocities with tissue Doppler. Building on this study, we propose a new velocity vector imaging method (Chapter 8). This approach combines tissue Doppler and ultrafast B-mode of the previous study to estimate 2D velocity fields within the myocardium. This original method was validated in vitro and in vivo on six healthy volunteers.

The present work details the creation and analysis of a finite element model of the foot, wherein the plantar fascia was modeled as a viscohyperelastic solid. The objective of this work was to develop a fully functional CAD and Finite Element Model of the foot and plantar fascia for analysis by examining the transient stresses on the plantar fascia through the use of a viscohyperelastic material model. The model’s geometry was developed through the use of image processing techniques with anatomical images provided by the National Institutes of Health. The finite element method was used to analyze the transient response of the plantar fascia during loading. As a first step towards modeling the transient response of the mechanical behavior of the plantar fascia under dynamic loadings, standing conditions were used to analyze the relaxation of the plantar fascia over a time period of 120 seconds (which is the steady-state relaxation time of the plantar fascia). This study resulted in a fully functional model with transient stress data on the behavior of the plantar fascia during loading, along with stress and deformation data for the bones and soft tissue of the foot. The results obtained were similar to that recorded in literature. This model is the first step towards fully characterizing the mechanics of the plantar fascia so as to develop novel treatment methods for plantar fasciitis, and can be applied to future studies to develop novel orthotic devices and surgical techniques for the treatment of and prevention of plantar fasciitis.

Previous studies have shown favourable properties for papaya bast fibres, with a Young's modulus of up to 10 GPa and a tensile strength of up to 100 MPa. Because the fibres remain as residues on papaya plantations across the tropics in large quantities, their use in the making of green composites would seem to be worthy of consideration. This study aims to show that such composites can have very suitable mechanical properties, comparable to or even better than the common wood plastic composites (WPCs), and as such, represent a promising raw material for composites and a low-cost alternative to wood.

Submitted in partial compliance with the requirements for the Master’s Degree in Technology: Chiropractic, Durban University of Technology, 2014. / Background: Classical ballet is an art form that seems graceful on the surface. However, beneath the disguise of beauty and ease lies an extremely physically demanding activity that calls for dedication, strength and perseverance. Ballet requires a specific body type and precise techniques, which predispose the dancer to musculoskeletal injury. Although a few studies have been conducted to investigate biomechanical factors as risk factors for injury in ballet dancers, few have included amateur ballet dancers and a range of biomechanical factors. Objectives: This study aimed to determine characteristics of ballet-related injury in amateur ballet dancers in the greater Durban area; to measure and record lower limb biomechanical measurements of these dancers; and to identify associations between the biomechanical measurements and characteristics of injury in the population. Method: A quantitative, questionnaire-based survey with biomechanical measurements was conducted on 21 amateur ballet dancers in the greater Durban area. Statistical analysis included the description of categorical variables using frequency and percentages in tables and bar charts. Continuous variables were summarised using mean, standard deviation and range, or median and range as appropriate. Independent Sample T-tests were used to compare biomechanical measurements between two independent groups. A p value <0.05 was considered as statistically significant. Pearson’s correlations and ANOVA testing were also used. Results: The period prevalence of ballet-related injury over the last 2 years was found to be 62% and the point prevalence 38%. There were 37 total previous injuries, most of which occurred in the hamstring (24%). Most of the worst previous injuries were reported to have occurred in the low back (31%). Most of the worst previous (70%) and current (93%) injuries occurred over time. The worst previous injuries reported ranged from mild to severe in severity, while the worst current injuries reported ranged from mild to moderate. Significant associations were found between right weight-bearing ankle dorsiflexion and previous injury; right weight-bearing ankle dorsiflexion and current injury; ‘functional turnout’ and onset of injury; right non weight-bearing ankle dorsiflexion and onset of injury; and ‘compensated turnout’ and onset of injury. Conclusion: The results suggest a significant association between musculoskeletal ballet-related injury and reduced weight-bearing ankle dorsiflexion; between injuries that occur over time (overuse injuries) and decreased ‘functional turnout’; and between overuse injuries and decreased non weight-bearing ankle dorsiflexion. These findings may help identify risk factors for injury in ballet dancers and contribute towards preventing ballet-related injury. / M

Muscle mechanical behavior potentially plays an important role in some of the most common bladder disorders. These include overactive bladder, which can involve involuntary contractions during bladder filling, and impaired contractility or underactive bladder, which may involve weak or incomplete contractions during voiding. Actin-myosin cross-bridges in detrusor smooth muscle (DSM) are responsible for contracting and emptying the bladder. The total tension produced by muscle is the sum of its preload and active tensions. Studies suggest that actin-myosin cross-links are involved in adjustable preload stiffness (APS), which is characterized by a preload tension curve that can be shifted along the length axis as a function of strain history and activation history. DSM also exhibits length adaptation in which the active tension curve can exhibit a similar shift. Actin-myosin cross-bridges are also responsible for myogenic contractions in response to quick stretch of DSM strips and spontaneous rhythmic contractions (SRC) that may occur during bladder filling. Studies show that SRC may participate in the mechanical regulation of both APS and length adaptation. However, the mechanical mechanisms by which actin-myosin interactions enable this interrelated combination of behaviors remain to be determined and were the primary focus of this dissertation. The objectives of this study were to: 1) provide evidence to support the hypothesis that a common mechanism is responsible for SRC and myogenic contraction, 2) develop a sensor-based mechanical model to demonstrate that SRC in one cell is sufficient to trigger stretch-induced myogenic contraction in surrounding cells and propagate the contraction, and 3) develop a conceptual model with actin-myosin cross-bridges and cross-links that produces the coupled mechanical behaviors of APS, SRC, and length adaptation in DSM. Improved understanding of bladder biomechanics may enable the identification of specific targets for the development of new treatments for overactive and underactive bladder.