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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

A Biomechanical Investigation of a Novel Implant for the Stabilization of Distal Radius Fractures

Allan, Andrew 15 August 2012 (has links)
Distal radius fractures are the single most common type of fracture suffered among the adult population. Presently, clinical decision making regarding optimal treatment is inconclusive. The goal of this thesis was to design, develop, and biomechanically test a novel implant for the stabilization of distal radius fractures. The novel implant is intended to provide a minimally invasive, low cost alternative to locked volar plates, while still permitting an earlier return to function. The implant consists of an angled bar with a sharp cutting edge and is inserted using a minimally invasive approach through the radial styloid. Surgical instrumentation was designed to facilitate the procedure in a controlled manner. To determine whether the implant would be capable of providing an early return to function, biomechanical tests were conducted both experimentally and numerically. Biomechanical testing showed that mechanical fixation with the novel implant does not support and early return to function.

Biomechanically Constrained Ultrasound to Computed Tomography Registration of the Lumbar Spine

Gill, Sean 30 November 2009 (has links)
Spinal injections for back-pain management are frequently carried out in hospitals and radiological clinics. Currently, these procedures are performed under fluoroscopy or CT guidance in specialized interventional radiology facilities, and thus incur a major financial burden on the healthcare system. Additionally, the current practice exposes patients and surgeons to X-ray radiation. The use of US for image guided navigation of the spine would greatly reduce the exposure of both the patient and the physician to ionizing radiation and allow the procedure to be performed outside of a specialized facility. However, US as the sole guidance modality has its own challenges. In particular, due to the significant level of occlusion in spinal US images, it can be difficult to accurately identify the appropriate injection site. Here, a groupwise US to CT registration algorithm for guiding percutaneous spinal interventions is presented. In our registration methodology, each vertebra in CT is treated as a sub-volume and transformed individually. A biomechanical model is used to constrain the displacement of the vertebrae relative to one another. The sub-volumes are then reconstructed into a single volume. In each iteration of registration, an US image is simulated from the reconstructed CT volume and an intensity-based similarity metric with the real US image is calculated. Validation studies are performed on datasets from a lamb cadaver, five patient-based phantoms designed to preserve realistic curvatures of the spine and a sixth patient-based phantom where the curvature of the spine is changed between preoperative and intraoperative imaging. For datasets where the spine curve between two imaging modalities was artificially perturbed, the proposed methodology was able to register initial misalignments of up to 20 mm with a success rate of 95%. For the phantom with a physical change in the curvature of the spine introduced between the US and CT datasets, the registration success rate was 98.5%. Finally, the registration success rate for the lamb cadaver with soft tissue information was 87%. The results demonstrate that our algorithm robustly registers US and CT datasets of the spine, regardless of a change in the patients pose between preoperative and intraoperative image acquisitions. / Thesis (Master, Computing) -- Queen's University, 2009-11-27 13:48:33.288

Modeling the transport of cryoprotective agents in articular cartilage for cryopreservation

Abazari Torqabeh, Alireza Unknown Date
No description available.

Time and frequency domain applications in biomechanics

Giakas, Giannis K. January 1998 (has links)
No description available.

Modeling the transport of cryoprotective agents in articular cartilage for cryopreservation

Abazari Torqabeh, Alireza 06 1900 (has links)
Loading vitrifiable concentrations of cryoprotective agents is an important step for cryopreservation of biological tissues by vitrification for research and transplantation purposes. This may be done by immersing the tissue in a cryoprotective agent (CPA) solution, and increasing the concentration, continuously or in multiple steps, and simultaneously decreasing the temperature to decrease the toxicity effects of the cryoprotective agent on the tissue cellular system. During cryoprotective agent loading, osmotic water movement from the tissue to the surrounding solution, and the resultant tissue shrinkage and stress-strain in the tissue matrix as well as on the cellular system can significantly alter the outcome of the cryopreservation protocol. In this thesis, a biomechanical model for articular cartilage is developed to account for the transport of the cryoprotective agent, the nonideal-nondilute properties of the vitrifiable solutions, the osmotic water movement and the resultant tissue shrinkage and stress-strain in the tissue matrix, and the osmotic volume change of the chondrocytes, during cryoprotective agent loading in the cartilage matrix. Four essential transport parameters needed for the model were specified, the values of which were obtained uniquely by fitting the model to experimental data from porcine articular cartilage. Then, it was shown that using real nonuniform initial distributions of water and fixed charges in cartilage, measured separately in this thesis using MRI, in the model can significantly affect the model predictions. The model predictions for dimethyl sulfoxide diffusion in porcine articular cartilage were verified by comparing to spatially and temporally resolved measurements of dimethyl sulfoxide concentration in porcine articular cartilage using a spectral MRI technique, developed for this purpose and novel to the field of cryobiology. It was demonstrated in this thesis that the developed mathematical model provides a novel tool for studying transport phenomena in cartilage during cryopreservation protocols, and can make accurate predictions for the quantities of interest for applications in the cryopreservation of articular cartilage. / Chemical Engineering

Development of a validation method for a cardiac-mri strain analysis system

Campbell, G. Unknown Date (has links)
No description available.

The impacts of climate and the environment on human skeletal morphology during the Holocene in north China

Siew, Yun Ysi January 2017 (has links)
This dissertation investigates the temporal and regional variation in human skeletal morphology in relation to climate and the environment in Holocene China. Linking skeletal morphology to the changes in climate, subsistence strategy and socio-political development has been well-documented in various geographical areas. Although a general pattern has been observed among different populations, it is evident that local factors have played an equally important role in human morphological variation. China was chosen in this dissertation because its diverse geographical, historical and cultural background provides an ideal setting in which to elucidate human biological responses to a variety different external forces and stimuli. A total sample of 533 adult skeletons, spanning from the mid-Neolithic to the twentieth century, was examined. These skeletons represent the ancient agriculturalists, nomadic pastoralists and agropastoralists inhabiting in contemporary Northeast China and modern humans from South China. This dissertation uses body size and shape, entheseal expression and biomechanical properties of long bones to investigate: 1.) temporal patterns in postcranial dimensions, stature and body mass; 2.) regional differences between the northern and southern Chinese in body size and body/limb proportions; and 3.) variation in skeletal biomechanics and entheses in relation to subsistence strategy. The findings in this dissertation indicated that while the human skeletons studied were morphologically varied throughout Holocene China, they were, to some extent, correlated with climatic and environmental factors. Body size and shape and body/limb proportions corresponded with variation in temperature. Additionally, stature, body mass and entheseal expression were correlated with socio-political and cultural development. Nevertheless, entheseal expression unexpectedly did not show a straightforward relationship with subsistence strategy, in which is inconsistent with the findings of previous studies. Although the comparisons of biomechanical properties were not unequivocal, they suggest differences in mobility and mechanical loading between different populations and subsistence strategies. On the whole, the results suggested that variation in skeletal morphology of the Holocene Chinese follows the universal patterns on the one hand, while on the other, they were influenced by local environmental and behavioural factors.

Análise biomecânica da marcha de indivíduos com osteoartrite do compartimento medial do joelho / Biomechanical gait analysis in subjects with knee osteoarthritis of the medial compartiment

Silva, Hésojy Gley Pereira Vital da, 1979- 02 September 2011 (has links)
Orientador: João Batista de Miranda / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-17T15:26:43Z (GMT). No. of bitstreams: 1 Silva_HesojyGleyPereiraVitalda_M.pdf: 1546474 bytes, checksum: 4af0be8378ecbdaf147f20da8c40d18f (MD5) Previous issue date: 2011 / Resumo: O objetivo deste trabalho é demonstrar a presença e a magnitude de determinadas variáveis biomecânicas na marcha de indivíduos com osteoartrite (OA) do compartimento medial de joelho. Em seguida, tentar relacioná-las com o carregamento do joelho, representado pelos picos precoce e tardio de momento adutor, na busca de fenômenos adaptativos ou de agravamento da patologia. Para isto, 16 indivíduos saudáveis e 21 indivíduos diagnosticados com OA do compartimento medial do joelho sintomáticos foram submetidos à análise da marcha e em seguida comparadas variáveis nos três planos espaciais. Avaliando os parâmetros espaço-temporais, observou-se que o grupo com OA apresentou redução de todos os valores (comprimento da passada, cadência, velocidade e tempo de ciclo) em relação ao grupo controle, principalmente representados pela redução da velocidade (0,8±0,1 vs. 1,1±0,1m/s). Exceção feita ao percentual da fase apoio que não apresentou modificação significativa. Na avaliação cinética, tanto o pico precoce do momento adutor (2,6±1,2 vs. 0,3±1,4 Nm/kg) quanto o pico tardio do momento adutor se apresentaram elevados nos indivíduos com OA (1,8±0,7 vs. 0,9±0,2 Nm/kg). Observação semelhante ocorreu no plano frontal, com maior pico do momento flexor (1,6±0,9 vs. 0,6±0,4 Nm/kg). Na cinemática, elevado pico de varo dinâmico (11,5o±8,3 vs. 3o±3,9) foi observado no plano frontal. No plano sagital, durante a fase de apoio, indivíduos com OA apresentaram maior pico de flexão (15,6o±8 vs. 9,3o±4,1), com tendência a menor extensão (5,5o±8,5). No mesmo plano, já na fase de balanço,os indivíduos com OA apresentaram menor pico de flexão (58,7o±13,3 vs. 67,5o±4,8). Elevados picos de rotação externa caracterizou a marcha de pacientes com OA (25,5o±12,7 vs. 0,5o±12,4). Os picos de ângulos e de momentos ocorreram nas mesmas fases da marcha nos dois grupos. Foi possível concluir que pacientes com OA do compartimento medial do joelho apresentam importantes modificações na marchaem relação a indivíduos saudáveis principalmente representados pelo elevado carregamento do joelho além de aumento da rotação externa e redução da velocidade. Esses últimos são estudados como possíveis fatores adaptativos e se mostraram insuficientes para manter o carregamento em valores normais. Foi ainda observado aumento do momento flexor e tendência a marcha em flexão no apoio como possível conseqüência destas adaptações. Os principais eventos cinéticos e cinemáticos ocorreram nas mesmas fases da marcha em ambos os grupos demonstrando que não há mudanças grosseiras no padrão da marcha / Abstract: The aim of this study is to demonstrate the presence and magnitude of certain biomechanical variables during gait in individuals with osteoarthritis (OA) of the medial compartment of the knee. Then, try to relate them to the loading of the knee, represented by the early and late peaks of adduction moment, searching for adaptive phenomena or aggravation of the condition. For this, 16 healthy subjects and 21 subjects diagnosed with symptomatic medial compartment OA of the knee underwent gait analysis and then compared variables in the three spatial planes. Assessing the spatio-temporal, it was observed that the group with OA showed a reduction of all values (step length, cadence, speed and cycle time) than the control group, represented mainly by reducing speed (0.8 ± 0.1 vs. 1.1 ± 0.1 m / s). The percentage of stance phase did not show significant change. In the kinetic evaluation, both the early adduction moment peak (2.6 ± 1.2 vs. 0.3 ± 1.4 Nm / kg) and the late adductor moment peak is presented elevated in patients with OA (1.8 ± 0.7 vs. 0.9 ± 0.2 Nm / kg). A similar observation occurred in the frontal plane, with higher flexor moment peak (1.6 ± 0.9 vs. 0.6 ± 0.4 Nm / kg). In the cinematic, high dynamic varus peak (11.5o ± 8.3 vs the. 3o ± 3.9) was observed in the frontal plane. In the sagittal plane, during the stance phase, patients with OA had higher flexion peak (15.6o ± 8 vs. 9.3o ± 4.1), tending to decrease extension (5.5o to ± 8.5). On the same plane, in the swing phase, subjects with OA had lower flexion peak (58.7o ± 13.3 vs. 67.5o ± 4.8). High peaks marked external rotation gait in patients with OA (25.5o ± 12.7 vs. 0.5o ± 12.4). The angles and moments peaks occurred on the same stages of gait in both groups. It was concluded that patients with OA of the medial compartment of the knee show significant changes in gait compared to healthy subjects represented mainly by the high loading of the knee as well as increased external rotation and speed reduction. External rotation and speed reduction are studied as possible adaptive factors and were insufficient to maintain the normal load in this study. It was also showed increased flexor moment and tends to flexion gait as a possible consequence of these adaptive variables. The main kinetic and kinematic events occurred in the same stages of gait in both groups showing that no substantial changes in the gait pattern / Mestrado / Fisiopatologia Cirúrgica / Mestre em Ciências da Cirurgia

The Effects of Aquatic Exercise on Physiological and Biomechanical Responses

Denning, Matthew M. 01 May 2010 (has links)
Due to recent advances in aquatic research, technology, and facilities, many modes of aquatic therapy now exist. These aquatic modes assist individuals (e.g., osteoarthritis patients) in the performance of activities that may be too difficult to complete on land. However, the biomechanical requirements of each aquatic therapy mode may elicit different physiological and functional responses. Therefore, the purpose of this thesis was to: (a) provide a review of the physiological and biomechanical differences between aquatic and land based exercises, and (b) examine the acute effects of underwater and land treadmill exercise on oxygen consumption (VO2), rating of perceived exertion (RPE), perceived pain, mobility, and gait kinematics for patients with osteoarthritis (OA). Methods consisted of the retrieval of experimental studies examining the physiological and biomechanical effects of deep water running (DWR), shallow water running (SWR), water calisthenics, and underwater treadmill therapy. The methods also examined the physiological and biomechanical effects on 19 participants during and after three consecutive exercise sessions on an underwater treadmill and on a land-based treadmill. Based on the studies reviewed, when compared to a similar land-based mode, VO2 values are lower during both DWR and SWR, but can be higher during water calisthenics and underwater treadmill exercise. RPE responses during DWR are similar during max effort, and stride frequency and stride length are both lower in all four aquatic modes than on land. Pain levels are no different between most water calisthenics, and most studies reported improvements in mobility after aquatic therapy, but no difference between the aquatic and land-based modes. The OA participants achieved VO2 values that were not different between conditions during moderate intensities, but were 37% greater during low intensity exercise on land than in water (p = 0.001). Perceived pain and Time Up & Go scores were 140% and 240% greater, respectively, for land than underwater treadmill exercise (p = 0.01). Patients diagnosed with OA may walk on an underwater treadmill at a moderate intensity with less pain and equivalent energy expenditures compared to walking on a land-based treadmill.

Biomechanics-Based Optimization for Exoskeleton Design

Hook, Melanie Lynn 24 May 2023 (has links)
The goal of this thesis is to use biomechanical data describing shoulder motion to determine optimal parameters to assist in the design of a 5 DOF active shoulder exoskeleton. This thesis will provide a proof of concept on optimization techniques using motion data using a simplified 3 DOF model to facilitate future work implementing a full 5 DOF model. Optimization will be performed to determine the link lengths and, consequently, the locations of the joints of the exoskeleton by considering the human's workspace to maximize range of motion and promote user safety by minimizing collisions of the exoskeleton with the user and with the exoskeleton itself. The thesis will detail the development of computational models of the human and proposed exoskeleton, the processing of experimental data used to estimate the human's capabilities, optimization, and future work. This work will contribute to a large-scale NSF-funded project of building an upper body exoskeleton emulator. The emulator will promote the widespread adoption of exoskeletons in industry by providing a test-bed to streamline the rapid design of various assistance profiles for various users and tasks. / Master of Science / An exoskeleton is a robotic assistive device used in industrial and rehabilitative settings. This thesis will use data describing how the human shoulder moves during certain tasks to help design an exoskeleton to assist with theses tasks. A model of the human shoulder and a model of the exoskeleton will be developed and used in an optimization to figure out the best dimensions of the exoskeleton links to support the human's movements.

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