Dissertations / Theses on the topic 'Prostheses'

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.
Includes bibliographical references (leaves 213-230).
Neural prosthetic devices offer a means of restoring function that have been lost due to neural damage. The first part of this thesis investigates the design of a 15-channel, low-power, fully implantable stimulator chip. The chip is powered wirelessly and receives wireless commands. The chip features a CMOS only ASK detector, a single-differential converter based on a novel feedback loop, a low-power adaptive bandwidth DLL and 15 programmable current sources that can be controlled via four commands. Though it is feasible to build an implantable stimulator chip, the amount of power required to stimulate more than 16 channels is prohibitively large. Clearly, there is a need for a fundamentally different approach. The ultimate challenge is to design a self-sufficient neural interface. The ideal device will lend itself to seamless integration with the existing neural architecture. This necessitates that communication with the neural tissue should be performed via chemical rather than electrical messages. However, catastrophic destruction of neural tissue due to the release of large quantities of a neuroactive species, like neurotransmitters, precludes the storage of quantities large enough to suffice for the lifetime of the device. The ideal device then should actively sequester the chemical species from the body and release it upon receiving appropriate triggers in a power efficient manner. This thesis proposes the use of ionic gradients, specifically K+ ions as an alternative chemical stimulation method. The required ions can readily be sequestered from the background extracellular fluid. The parameters of using such a stimulation technique are first established by performing in-vitro experiments on rabbit retinas. The results show that modest increases (~~10mM) of K+ ions are sufficient to elicit a neural response.
(cont.) The first building block of making such a stimulation technique possible is the development of a potassium selective membrane. To achieve low-power the membranes must be ultrathin to allow for efficient operation in the diffusive transport limited regime. One method of achieving this is to use lyotropic self-assembly; unfortunately, conventional lipid bilayers cannot be used since they are not robust enough. Furthermore, the membrane cannot be made potassium selective by simply incorporating ion carriers since they would eventually leach away from the membrane. A single solution that solves all the above issues was then investigated in this thesis. A novel facile synthesis of self-assembling receptor functionalized polymers was achieved. By combining the properties of hydrophobic and hydrophilic interactions of two polymers a triblock co-polymer was synthesized. The middle hydrophobic block was composed of biocompatible polysiloxanes and further derivatized to posses ion recognition capabilities via pendant crown ether chains. The hydrophilic blocks were composed of biocompatible polyoxazolines. The self-assembling properties of the membrane were then studied by electroforming them into vesicular structures. The ion responsive properties of these polymers were then examined. These polymers show emergent behavior such as, spontaneous fusion and shape transformation to ionic stimuli due to the synergy between form and function. The results from the thesis show that it is feasible to build a renewable chemically based neural prosthesis based on supramolecular architectures. However, there remains a lot of fundamental work that needs to be pursued in the future to bring the idea to complete fruition.
by Luke Satish Kumar Theogarajan.
Ph.D.

La thèse de doctorat intitulée " Research on optimizing customized prostheses " a pour objectif final de développer un logiciel qui modifie la géométrie d'une tige fémorale en fonction de paramètres prédéterminés après l’analyse des images tomographiques du patient. Afin d'obtenir des résultats, ont été réalisées les études suivantes : Des images tomographiques ont été obtenues de patients avec une hanche saine, de patients avec une hanche arthritique et de patients avec prothèse totale de hanche ; Une planification virtuelle de l'opération de remplacement total de la hanche a été réalisée pour construire une prothèse personnalisée et identifier les paramètres qui peuvent être optimisés ; Des études FEA ont été réalisées sur les tiges prothétiques standard et sur la tige prothétique personnalisée pour observer le comportement mécanique de la prothèse sujet à différentes charges externes ; Après avoir interprété les résultats, nous avons poursuivi le développement du logiciel, son objectif sera l’impression de la tige fémorale personnalisée par la technique de fabrication additive
This thesis aims to develop a virtual surgery planning methodology starting from the traditional Total Hip Replacement preoperative planning and having as final goal the realization of a template prosthesis that can be customized according to the femoral landmarks of each patient. Starting from the traditional preoperative planning of THR, which is done on the patients’ X-Ray and using the same principles of obtaining femoral landmarks, the CT scans of a patient with hip joint related disease that need to undergo a THR surgery were segmented by using specific algorithms in order to extract the patients’ femur and after that was imported in dedicated CAD software in which, with the help of evaluation instruments, all the patients’ femoral landmarks were identified. These femoral landmarks were used to develop a custom prosthesis starting from a standard anatomical femoral stem, which was validated using FEA simulations. Based on the information obtained, the development of a software coded in Python language was done to create somehow a tool that allows the analysis of patients’ CT scans in MPR view, but also in 3D view. It allows the bone segmentation of the affected area in order to obtain a CAD model file and perform the virtual preoperative planning in a CAD dedicated software, and finally use some of these dimensions in order to personalize a custom hip stem based on a pre-existing stem model used as basis for the desired geometrical transformations. The work is completed by printing it with FDM technology, using a biocompatible material to demonstrate the potential of this study, the versatility and the possibility of orienting the femoral stems used in THR towards personalization and AM, avoiding the use of standard prostheses that can lead to postoperative complications and thus leading to the elimination of prostheses “banks” due to the fact that they would no longer be necessary

There is increasing use of Unicondylar or Unicompartmental Knee Replacements (UKR), especially following publication of good survival data and a trend towards ‘minimally invasive surgery’. The UKR preserves one of the femoral condyles and its meniscus, plus both of the cruciate ligaments. Therefore, the knee functions more normally following UKR than after Total Knee Replacement (TKR). However, the odds for failure of the UKR are higher than the TKR, and a principal reason is loosening of the tibial and femoral components. There is a need for the development of more reliable UKR fixation designs. The overall aim of this research was to understand fixation of UKR and make recommendations for improvement to designers and surgeons. Since the Oxford mobile-bearing UKR is most widely used in the UK, it was used as the benchmark in this study. To assess initial fixation, in-vitro bone-constructs were prepared from ten cadavers implanted with the Oxford mobile-bearing UKR and tested for bone strain and bone-implant interface motion with the implants fixed using first cementless and then cemented methods. Cementless fixation produced higher proximal tibia strain and bone-implant displacement than cemented fixation. Peak bone strain increased with reduced bone density, such that the lowest density specimen fractured when implanted with the cementless UKR. To assess long-term fixation, an in-vivo prospective follow-up study of 11 Oxford UKR patients was developed and conducted for one-year, taking measurements of bone density using Dual X-Ray Absorptiometry (DXA) scanning. The average bone resorption under the tibial implant was found to be low; while it was higher under the femoral component and very high under the tibial intercondylar eminence. The fixation of the Oxford UKR implant was considered to be adequate at 1-year. Finite Element (FE) simulation techniques were reviewed and developed to simulate the UKR knee for investigation of bone strain, bone-implant interface micromotion and bone remodelling to assess initial and long-term fixation performance. Computer simulations of the tibiae and femora of 2 patients and 4 cadaveric specimens (obtained from the in-vivo and in-vitro studies) were developed and validated for bone strain, bone-implant interface micromotion and bone remodelling. Comparative multi-specimen computational studies were conducted to understand how particular design features affected fixation. Good fixation was indicated for cementless UKRs when implanted in dense bone, but bone strains were very high in low density tibia. Cementation of the implants spread the loads more evenly and reduced bone strains. The cementless tibial implant caused less bone resorption (compared to the cemented equivalent) but the difference in the femur was small. Bone resorption was highest at the anterior tibia and posterior to the femoral peg. Bone density was an important factor in the fixation performance of implant design features. Less bulky fixation features reduced bone resorption, provided that the underlying bone was sufficiently dense to maintain bone strains below the failure limit of bone. For patients with dense bone, fixation could be improved with shorter tibial keels and less stiff femoral implants. For patients with low density bone, fixation could be improved with cementation and bone resection that avoids creating stress-raisers.

In the last years the number of shoulder arthroplasties has been increasing. Simultaneously the study of their shape, size and strength and the reasons that bring to a possible early explantation have not yet been examined in detail. The research carried out directly on explants is practically nonexistent, this means a poor understanding of the mechanisms leading the patient and so the surgeon, to their removal. The analysis of the mechanisms which are the cause of instability, dislocation, broken, fracture, etc, may lead to a change in the structure or design of the shoulder prostheses and lengthen the life of the implant in situ. The idea was to analyze 22 explants through three methods in order to find roughness, corrosion and surface wear. In the first method, the humeral heads and/or the glenospheres were examined with the interferometer, a machine that through electromagnetic waves gives information about the roughness of the surfaces under examination. The output of the device was a total profile containing both roughness and information on the waves (representing the spatial waves most characteristic on the surface). The most important value is called "roughness average" and brings the average value of the peaks found in the local defects of the surfaces. It was found that 42% of the prostheses had considerable peak values in the area where the damage was caused by the implant and not only by external events, such as possibly the surgeon's hand. One of the problems of interest in the use of metallic biomaterials is their resistance to corrosion. The clinical significance of the degradation of metal implants has been the purpose of the second method; the interaction between human body and metal components is critical to understand how and why they arrive to corrosion. The percentage of damage in the joints of the prosthetic components has been calculated via high resolution photos and the software ImageJ. The 40% and 50% of the area appeared to have scratches or multiple lines due to mechanical artifacts. The third method of analysis has been made through the use of electron microscopy to quantify the wear surface in polyethylene components. Different joint movements correspond to different mechanisms of damage, which were imprinted in the parts of polyethylene examined. The most affected area was located mainly in the side edges. The results could help the manufacturers to modify the design of the prostheses and thus reduce the number of explants. It could also help surgeons in choosing the model of the prosthesis to be implanted in the patient.

Although extensive research has been undertaken on wear of alumina there is still poor understanding about the mechanisms which can take place during the ill vivo wear of alumina, such as found in alumina hip prostheses. In particular, the origin of 'stripe' wear, a region of high wear dominated by fracture that is observed widely from retrieved ill vivo alumina hip prostheses, has not been clearly determined. Moreover, it has not been completely validated that laboratory hip simulators reproduce the same wear mechanisms as found in the body, although it is known that the stripe wear can only be replicated by the introduction of microseparation during the simulated walking cycle. The current study presents detailed analysis of the worn surface of alumina acetabular cup and alumina femoral head following ill vitro testing incorporating microseparation at the University of Leeds, as well as retrieved ill vivo alumina hip prostheses. Four different wear zones were identified on both the acetabular cup and femoral head for both ill vitro and ill vivo specimens, defined as: mild wear, wear transition, stripe boundary and stripe wear zones. Although sequence of events cannot be verified, the available evidence indicated the following wear process of alumina hip prostheses: rather than the final stage of the wear process, fracture occurred in the early stages due to the local impact associated with microseparation, leading to the region of stripe wear. FIB cross-section investigations showed that fracture was predominantly intergranular, with some transgranular fracture, and that in both cases, fracture was restricted to the outer layer of grains. In addition, plastic deformation and a 3rd body abrasion were also observed, with the dislocation activity also restricted to the outer grains. The wear debris liberated from the stripe wear region was believed to subsequently have resulted in wear in other parts of the joint that would otherwise have shown little evidence of damage. The stripe boundary zone, immediately adjacent to the stripe wear region, exhibited minimal wear, with a remarkably sharp boundary between the stripe wear and mild wear. The explanation for such an abrupt change from mild to severe wear were possibly abrupt change in lubrication from microseparation or small changes in the height of the alumina surface. Most of the remaining surface on the worn alumina-on-alumina THRs had experience only mild wear. Detailed analysis of this region showed that it contained extensive fine scale 3rd body abrasion, presumably from wear debris that had become much finer due to attrition between the articulating surfaces, originally coming from the stripe wear region. Cross-sectional TEM indicated that the abrasive grooves did result in surface dislocation activity which was restricted to the outer 100nm of the surface. In addition, differential wear between grains was observed in the mild wear zone, which was believed to be evidence of tribochemical wear. Some small additional wear scars, similar to the observations of the morphology of stripe wear and parallel to the stripe wear occurred near the stripe wear region on ill vitro and retrieved ill vivo alumina femoral heads in the mild wear zone. A wear transition zone outside the stripe wear zone was identified, comprising a highly pitted surface and an amount ofwear debris. The pits had largely arisen from intergranular fracture. The extent of this region was limited compared with other wear zones and was more obvious on the alumina acetabular cup than on the alumina femoral head. Detail TEM analysis showed of this region showed extensive dislocation activity on the pyramidal system. Three types of wear debris were observed: globular wear debris, nanocrystalline wear debris and needle shaped wear debris. The globular wear debris is most likely to have come from grains been pulled out and covered by tribochemical film as it rolls over the surface. The nanocrystalline wear debris was believed to arise from 3rd body microabrasion during the normal articulation and the needle shaped wear debris is believed to be a direct product of tribochemical wear.

In recent years, many new prosthetic devices have entered the marketplace claiming to be easy to use and to significantly improve the functional outcomes of the amputees. This research study aimed at establishing evidence and providing tools to rehabilitation professionals and funding agencies for use in appropriate prescriptions of prostheses to amputees who lost their upper limbs from work-related injuries. The thesis started with a review of published literatures on upper limb myoelectric prostheses. The review focused on critical factors affecting successful prescriptions, current standards governing design and safe use, guidelines and practice for testing, performance evaluation, and outcome measurements. To understand the current practice and state of technology, an overview of upper limb functions, amputation characteristics, residual limb management, prosthetic intervention, and current prosthetic technologies was included. A retrospective data analysis was performed on case files of upper limb amputee prosthetic users. The analysis first looked at the profile of the amputees, characteristics of prosthetic prescriptions, and levels of prosthetic utilization. Based on the claim files from prosthetists, the reliability, maintenance requirements, as well as the acquisition and operating costs of different prosthetic devices were studied. Results of the analysis such as prosthetic abandonment rates, mean time between failures, average maintenance service intervals, and life-cycle cost of ownerships were presented. A survey was performed to collect information on safety issues relating to prosthetic use. Based on survey results and risk management standards on medical devices, a systematic process to perform risk assessment on upper limb prostheses was formulated. This process took into consideration the functional activities and employment needs from the users’ and caregivers’ perspectives. An assessment platform for upper limb externally-powered prostheses was developed. The platform consisted of a hardware EMG signal acquisition module, an analog I/O module, virtual instrument (VI) modules, and a number of custom-built transducer circuits. The platform was designed to assess the functional performance of myoelectric prostheses and to verify technical specifications of prosthetic components. Two commercial myoelectric prosthetic terminal devices were used to validate the platform.

Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, February 2013.
"September 2012." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 113-118).
Since the time of the first philosophers, logic and observed human behavior have stood somewhat in contradiction. More recently, scientist have started to delve into decision making to understand why the way we act differs from rational choice, and indeed from our own desires. We believe that it is possible to use just-in-time feedback drawn from machine-observable behavior to help align behavior with personal goals. This dissertation presents mental prosthetics, a model for distributed, embodied, design-embedded, just-in-time interfaces that augment the human judgment process. Drawing information from the activity of the user around them, mental prostheses analyze behavioral patterns in a way orthogonal to human cognition. Unlike persuasive interfaces, mental prostheses attempt to align choices with personal goals by cueing the user with just-in-time information. Lastly, these devices provide calm yet understandable feedback to draw the user's attention at the correct time to the information available to them. This dissertation provides several prototypes and design explorations as a means of sampling the various approaches to data collection, synthesis, and feedback. Focusing on self-reflection, these sample designs form a subclass of mental prostheses that we term reflectOns. We show through the studies carried out in the course of this dissertation that these systems are effective in changing behavior to be better aligned with user goals. Lastly, this dissertation provides a set of design guidelines that assist in the creation of new mental prostheses. While we discuss a variety of scenarios in this work, it is only the beginning of the exploration. The design guidelines provide insight into both the critical aspects of the design of such systems, as well as possible input and feedback methodologies. These guidelines, together with the reflectOns themselves, provide a basis for future work in this area.
by Sajid Sadi.
Ph.D.

The most commonly reported failure modes of cementless hip stems are loosening and thigh pain both are attributed to the relative motion at the bone-implant interface due to failure to achieve sufficient primary fixation. The main aim of the current study is to investigate, using Finite Element Analysis, various factors that could affect micromotion and could compromise the stability of cementless femoral stems. We propose a novel technique for predicting hip stem instability to analyse these problems. The designs of cementless hip stems are crucial to its success. We first categorize them into three major types based on the overall geometry and they are all found to be stable under physiological loadings. Tsoelastic' stems are found to increase interface micromotion, but if tight fit is achieved distally, the stem would still be stable. Having shorter stems for primary arthroplasty is beneficial if revision surgery is required, but these produce larger relative motion. The results from this study show that if sufficient cortical contact is achieved distally, stability is not impaired. Two types of hip stems' fixation are also compared the proximal fixation design is found to be less stable than the distal fixation design, but stability can be improved with the use of proximal macrofeatures. The strength of primary fixation also depends on surgical parameters imprecise surgical procedures can cause interfacial gaps, implant undersizing and implant malalignment. The FE results show that undersizing should be avoided because it increases micromotion and instability, especially in stems with cylindrical design. Hip stems with varus malalignment are found to be relatively stable compared to the normally aligned undersized stem. Interfacial gaps due to surgical error are not found to impair the stem's fixation as long as maximum press-fit is achieved. Successful implant fixation also depends on the quality of the bone. Bone with skeletal diseases of osteoporosis and osteoarthritis are analysed and compared with the results from a normal healthy bone. The hip stem in the osteoporotic bone is found to have the largest micromotion and is the most unstable, especially during stair-climbing activity.

This work was digitised and made available on open access by the University of Sydney, Faculty of Dentistry and Sydney eScholarship . It may only be used for the purposes of research and study. Where possible, the Faculty will try to notify the author of this work. If you have any inquiries or issues regarding this work being made available please contact the Sydney eScholarship Repository Coordinator - ses@library.usyd.edu.au

This thesis explores methods for enhancing digital image-like sensations which might be similar to those experienced by blind users of electronic visual prostheses. Visual prostheses, otherwise referred to as artificial vision systems or bionic eyes, may operate at ultra low image quality and information levels as opposed to more common electronic displays such as televisions, for which our expectations of image quality are much higher. The scope of the research is limited to enhancement by digital image processing: that is, by manipulating the content of images presented to the user. The work was undertaken to improve the effectiveness of visual prostheses in representing the visible world. Presently visual prosthesis development is limited to animal models in Australia and prototype human trials overseas. Consequently this thesis deals with simulated vision experiments using normally sighted viewers. The experiments involve an original application of existing image processing techniques to the field of low quality vision anticipated from visual prostheses. Resulting from this work are firstly recommendations for effective image processing methods for enhancing viewer perception when using visual prosthesis prototypes. Although limited to low quality images, recognition of some objects can still be achieved, and it is useful for a viewer to be presented with several variations of the image representing different processing methods. Scene understanding can be improved by incorporating Region-of-Interest techniques that identify salient areas within images and allow a user to zoom into that area of the image. Also there is some benefit in tailoring the image processing depending on the type of scene. Secondly the research involved the construction of a metric for basic information required for the interpretation of a visual scene at low image quality. The amount of information content within an image was quantified using inherent attributes of the image and shown to be positively correlated with the ability of the image to be recognised at low quality.

This thesis explores methods for enhancing digital image-like sensations which might be similar to those experienced by blind users of electronic visual prostheses. Visual prostheses, otherwise referred to as artificial vision systems or bionic eyes, may operate at ultra low image quality and information levels as opposed to more common electronic displays such as televisions, for which our expectations of image quality are much higher. The scope of the research is limited to enhancement by digital image processing: that is, by manipulating the content of images presented to the user. The work was undertaken to improve the effectiveness of visual prostheses in representing the visible world. Presently visual prosthesis development is limited to animal models in Australia and prototype human trials overseas. Consequently this thesis deals with simulated vision experiments using normally sighted viewers. The experiments involve an original application of existing image processing techniques to the field of low quality vision anticipated from visual prostheses. Resulting from this work are firstly recommendations for effective image processing methods for enhancing viewer perception when using visual prosthesis prototypes. Although limited to low quality images, recognition of some objects can still be achieved, and it is useful for a viewer to be presented with several variations of the image representing different processing methods. Scene understanding can be improved by incorporating Region-of-Interest techniques that identify salient areas within images and allow a user to zoom into that area of the image. Also there is some benefit in tailoring the image processing depending on the type of scene. Secondly the research involved the construction of a metric for basic information required for the interpretation of a visual scene at low image quality. The amount of information content within an image was quantified using inherent attributes of the image and shown to be positively correlated with the ability of the image to be recognised at low quality.

O uso do Sistema CAD/CAM já é bastante consagrado na Odontologia, não sendo diferente na reabilitação facial. Traz diversas facilidades, porém poucos trabalhos relatam as reabilitações da região óculo-palpebral. Nesse estudo, a aquisição de imagem tridimensional foi feita com o uso de um escâner de superfície a laser, FARO Edge ScanArm®, protegendo-se o olho contralateral com uso de lente gelatinosa preta; método que demonstrou eficiência na obtenção de imagem de pálpebras abertas para confecção de protótipo reverso. Foram selecionados 10 pacientes com exenteração de órbita, de ambos os gêneros, sendo 5 com mutilação à esquerda e 5 à direita. Todos os pacientes receberam duas próteses óculo-palpebrais, uma confeccionada pelo método convencional e outra pelo sistema CAD/CAM. As reabilitações foram registradas fotograficamente e avaliadas por 30 indivíduos leigos, 3 especialistas em prótese bucomaxilofacial e pelos próprios pacientes, usando-se a Escala VAS. Para avaliar a variação intraexaminador, 15 leigos repetiram a avaliação com intervalo de uma semana, assim como os 3 especialistas. Os resultados demonstraram consistência interna e uma boa reprodutibilidade dos dados em todos os grupos. A percepção estética foi melhor avaliada nas próteses obtidas pelo método convencional; entretanto, a relevância da diferença observada entre os dois métodos foi avaliada como razoável.
The use of CAD/CAM system is already an established method in Dentistry, no different in facial rehabilitation. It brings several facilities, but few studies have already reported the rehabilitations of the orbital area. In this research the acquisition of the three dimensional image was taken using a surface laser scanner, FARO Edge ScanArm®, protecting the contralateral eye with the use of a black gelatinous contact lens; this method has demonstrated effectiveness in getting image with open eyelids for making reverse prototype. 10 patients were select with orbit exenteration, of both genders, 5 with left mutilation and 5 with right. All patients received two oculopalpebral prostheses, one obtained by the conventional method and another by the CAD/CAM system. The rehabilitations were photo registrated and assessed by 30 lay assessors, 3 bucomaxillofacial prosthetic specialists and by the patients themselves using the VAS Scale. To evaluate the intraexaminer variation, 15 lay assessors repeated the evaluation with one week interval, as did the specialists. The results demonstrated good interexaminer variation and reproducibility of data in all groups. The aesthetic perception was better evaluated in prostheses obtained by the conventional method; however, the relevance of difference between the two methods was assessed as a reasonable one.

Myoelectric prostheses are designed to provide cosmesis and a degree of upper limb functionality for people with upper limb absence. However, self-reported rejection rates remain stubbornly high, with control of the prosthesis being commonly cited as one of the primary reasons. This observation may indicate that the significant engineering efforts aimed at improving prosthesis control may not have been addressing the most important issues. Surprisingly, there has been no empirical work outside of lab environments to understand the relative importance of key factors affecting prosthesis control. This thesis explores the impacts of three factors: (1) user skill in controlling an EMG signal, (2) unpredictability of prosthesis response introduced at the interface between the electrodes and the skin, and (3) the electromechanical delay in the prosthesis, on user performance, quantified in terms of: (1) functionality (kinematic and gaze), and (2), for the first time, everyday prosthesis use. Chapter 1 introduces the thesis, followed by Chapter 2, which contains a review of existing literature relating to the factors affecting control of myoelectric prostheses. Chapters 3 reports a protocol for the assessment of the impact of skill, unpredictability and delays on user functionality and real world use of a prosthesis. Chapter 4 introduces the first method for the visualisation of time series data from wrist worn accelerometers and presents the first time series data on everyday prosthesis use. Chapter 5 presents results of a study, which recruited 20 trans-radial myoelectric prosthesis users from 6 centres across the UK, drawing conclusions as to the relative impacts of each control factor on performance. Results suggest unpredictability introduced at the electrode-skin interface by the socket mounted electrodes may be the key factor affecting control. Additionally, the results show the delay to the onset of hand opening from a fully closed position to be approximately double the delay measured from any other starting hand aperture. Chapter 6 reports on upper limb activity in the 20 trans-radial prosthesis users and 20 anatomically intact participants. The results show that, by contrast to the anatomically intact participants, upper limb activity of prosthesis users is heavily biased towards the intact limb. Finally Chapter 7 summarises the main findings of the thesis, addressing limitations and suggesting future work.

In the last couple of years The Institute of Cybernetics at NTNU, Norway, has based its research on the SVEN work carried out in Sweden in the late 1970’s. The SVEN hand was an on/off-controlled upper limb prosthesis based on electromyographic (EMG) signals. This master thesis is a part of the renewed and continuing research. This study will try to identify signal features that are beneficial in a proportional control of a multi-function upper limb prosthesis. The intent is to identify a set of signal features that could be implemented in a practical proportional control system to enhance the movement functions of the prosthesis such that it more closely mimic the movements of a normal upper limb. The data set used in this paper consist of EMG signals and VICON angle data recorded by Fougner (2007). A short explanation will be given on how to acquire such data. A brief introduction on feature selection defines the properties of a wrapper and filter approach in search for a feature subset. Wavelets properties are explained and two wavelet techniques are used in order to obtain more information from the EMG signal in addition to existing features. From this, we search for a subset of features that will let us use a mapping function that estimates a correct motion with respect to the features fed to it. The Cosine Similarity Transform (CST) and the Correlation coefficient (CORR) will in addition to RMSE be investigated in order to find an optimal performance indicator. With a good and reliable indicator we may find a suitable subset. EWC-WAVE were found to be the best subset according to both CST and RMSE. Based upon the information obtained from each performance indicator, it is suggested that CST should be carried out as a measure of accuracy on how to map data in the future. There are still unsolved problems. Some of the angles we tried to estimate with a neural network suffered and produced non-informative data. This indicate that one should add more hidden nodes to a neural network when more features are used as input. We have obtained indications that we do need to combine feature subsets in order to obtain higher accuracy of the estimated signal. It is proposed that a post-processing technique should be developed and used subsequent to the pattern recognition methods in order to achieve a signal that better reflects the estimation and may be used as a control signal for a prosthesis. Hopefully will these findings help improve future work to achieve an enhanced proportional control for a real prosthesis.

Millions of people are suffering from lower limb loss all around the world. Passive ankle prostheses in the market cannot fully restore ankle function and will cause asymmetrical walking gaits. Several powered ankle prostheses, which provide net power in the stance phase to assist walking, have been developed by the researchers, but their walking range is significantly limited by the power requirement. In this thesis, an electrohydrostatic actuator (EHA) powered ankle prosthesis is proposed. This is intended to actively assist walking at certain points in the gait cycle, namely the plantarflexion (PF) before toe-off and dorsiflexion (DF) in the early swing phase for toe-lifting. In the rest of the gait, the ankle prosthesis actuation system can operate passively with controllable damping. This approach can increase the working time range compared to a continually powered ankle and ensure safe passive prosthetic function after the battery discharged. A prototype of the EHA powered ankle prosthesis has been developed. A 100 W brushless DC motor is used driving a 0.45 cc/rev bi-directional gear pump. The damping ratios of the ankle PF and DF are controlled by bypass restriction valves. The EHA system and the foot springs at the ankle joint weigh 2.2 kg. The controller and a 2 Ah battery are held in a backpack. Walking characteristics with a passive ankle were studied in an amputee trial to gather ankle sensor signals for the controller design. A timing control method is proposed which uses the foot spring strain gauge signals to detect heel strike. A middle stance time delay is added between the end of the heel strike and the start of the powered PF phase. This delay time length can be adjusted to fit different walking speeds. Heel strike detection using hydraulic pressure signals is also studied. The EHA powered ankle prosthesis and its controller has been tested by a 70 kg transtibial amputee. According to the amputee trial results, the EHA can provide sufficient power to assist walking in the terminal stance and the energy consumption in the passive phases are proximately zero. The on-board battery is able to power over 5500 level walking steps. In the amputee trial, the ankle prosthesis controller correctly recognises the heel strike and triggers the powered PF phase. According to feedback from the amputee, the EHA powered ankle prosthesis provided beneficial level walking assistance and a very natural walking gait. The characteristics of the powered ankle prosthesis are analysed by comparing with the healthy ankle and by testing at different walking speeds. A simulation model was developed to help analyse the performance characteristics of the EHA. This includes a brushless DC motor model and a symmetric hydraulic actuation model. The laboratory-based experiment results and amputee trial results are used to analyse and validate the simulation model. The model can be used for future development and refinement of EHA powered ankle prostheses.

Metal-on-metal (MOM) total hip replacement is an artificial hip joint has been used to replace damaged or diseased natural joints. MOM studies have demonstrated severe complications due to metal wear debris in tissues adjacent to the implants. Reducing the wear rate and operating with full film lubrication could reduce these problems; a better understanding of the lubrication mechanisms is also relevant to other hard bearing materials such as ceramics or new metal alloys. Ball-in-socket MOM contacts were analysed using the Abaqus Finite Element package to simulate dry contact between the acetabular cup and the femoral head. Different cup thicknesses of 4, 6, 8, and 10 mm were considered using a polyurethane foam block support system. Elastohydrodynamic lubrication (EHL) analyses were developed for the contacts using three different approaches to specify the contact. These were (i) A simple model based on the radii of relative curvature, (ii) An equivalent contact model developed so that its dry contact area and maximum pressure replicated the values obtained from the FE analysis, and (iii) A modified version of (ii) that also ensured equivalence of the gap shape outside the contact area. Published in vivo information for the hip joint contact forces over the walking cycle was used to specify the operating conditions for the EHL analysis. III This was achieved by developing techniques to transform the in vivo information to provide load direction and kinematic information relative to the nominal contact point between the components. The analysis method was found to be effective for all points of the walking cycle for cases where the cup thickness exceeded 5 mm and modelling approach (ii) was identified as satisfactory. For a cup thickness of 4 mm, membrane action began to emerge in the FE analyses so that such contacts behaved in a different way.

Background Dental prostheses have seen a major change since the advent of dental implants in 1965. The osseointegration property of titanium fixtures enables dentists to place a dental prosthesis at almost everywhere intra-orally provided there is sufficient bone to support it. The novel treatment modality had attracted attention of clinicians who had made multiple innovations on their use. Meanwhile, there has also been a shift of focus in the medical field from disease-centered outcome to subjective patient-centered outcome in the measurement of health status. Quality of Life (QoL) measurements are one of the subjective measurements of health status. They provided a means for clinicians to compare different prostheses, including dental prostheses. Aim and Objectives This systematic review seeks to identify evidence that proves the superiority of the new treatment modality in improving QoL or Oral Health Related QoL and to briefly discuss their implications for public health policies in Hong Kong. Methods Researches which compare conventional removable dental prostheses and the fixed alternatives in terms of improving QoL were identified. The evidence was scrutinized, critically analyzed and a summary was made. Results Current evidence is only strong enough to support the superiority of the new implanted supported prostheses over the conventional type for patients without lower teeth. Discussion and Conclusions It is concluded in this systematic review that the new implant-fixed or supported dental prostheses are superior to conventional removable dental prostheses for patients without lower teeth. However, it is so far inconclusive as to whether dental implants have greater impact on QoL of partially dentate patients than conventional removable dental prostheses. The cost-effectiveness of this treatment modality in improving QoL is also unclear yet.
published_or_final_version
Medicine
Master
Master of Public Health

Selecting an appropriate prosthesis is a complex process. To the best of our knowledge, to date there is no standard prescription protocol for upper limb prostheses. Thus, the primary objective of this study was to propose a prescription protocol for upper limb prostheses. To understand more about the properties of the prosthetic terminal device; frictional properties of the contact surfaces between terminal devices and the grasped object, and the effect of loading rates on the frictional properties of the terminal devices were evaluated. The results showed that metal is better gripped by the body-powered hook than by the myoelectric hand; whereas plastic and wood are better gripped by the myoelectric hand than by the body-powered hook. In addition, as loading rate increases, the friction coefficient decreases. With regard to the prescription protocol for upper limb prostheses, this study proposed a prescription protocol that not only contains comprehensive information, but also proposed a scoring system to assist in selecting an appropriate prosthesis. The scoring system was developed by factorial survey approach. Five factors affecting the type of upper limb prosthetic device were selected for vignette constructions. Twenty upper limb prosthetic experts were involved in this study. Each participant was asked to rate 20 vignettes regarding the appropriateness in selecting a myoelectric prosthesis for an individual with upper limb amputation. The findings from the factorial survey analysis suggested that “work condition” is the most critical factor that influences the judgments of the upper limb prosthetic experts in making the selection of prosthetic devices for both trans-radial and trans-humeral amputation. The proposed scoring system was also evaluated for its effectiveness. The study suggests that the proposed scoring system may be improved as a tool to assist in the selection of an appropriate prosthetic device. In conclusion, this study suggested that the frictional coefficients of the terminal devices and the grasped objects are dependent on the material and the loading rate. “Work condition” is a key factor in selecting an appropriate prosthesis for the upper limb amputee, and a systematic evaluation of an amputee’s condition is useful in selecting an appropriate prosthetic device.

In the project a method to calculate the displacement of hip prostheses inside a hip socket is made. The project, performed as a bachelor thesis project is a cooperation between Karolinska Institute and Uppsala University. Hip replacements are expensive surgeries. Loosening is a large problem for orthopedists and patients, and costs both time and expenses. If dislocations of hip prostheses are detected in an early stage, preventions to reduce the loosening can be done. The method is programmed in Matlab code utilizing Computational Tomographic Images (CT). The CT images are built up by putting 0.5 [mm] wide X-ray slices after each other. In the project a model of a human hip made of plastic is used with two real hip prostheses, one for each hip, and small balls, around some [mm] in diameter, made of tantalum are located inside the plastic bone. The purpose of the tantalum balls are to mark the bones’ position and makes it easier toget exact coordinates from the X-ray images of the bone structure.

The technique of attaching a limb directly to the skeleton has clear benefits, when compared with socket-attachment, for the many amputees who encounter skin problems. A potential risk of attaching a limb to the skeleton is the wound where the implant breaches the skin. At the Centre for Biomedical Engineering in the Institute of Orthopaedics and Musculoskeletal Science at UCL, a method has been devised which enhances epithelial attachment to the implant, resisting infection, and this has been used to develop a system for attaching a limb to the skeleton: Intraosseous Transcutaneous Amputation Prosthesis, or ITAP. In a transfemoral prosthesis, protection of bone from external loading is anticipated and in this thesis a fail-safe component is designed to prevent fracture. It has adjustable activation levels and has been tested to the appropriate International Standards. In order to determine loads that are to be allowed and prevented, normal loading of the femur during ordinary activities is researched failure modes of femoral bone are investigated. Finite element analysis is employed to investigate the stress distribution throughout the femur with the attachment of a prosthetic leg. A cylindrical model is used to assess the effect of varying geometry and material properties of the bone and implant. An anatomical model, derived from a CT scan, is used to analyse the effect of stump length. There are three risk groups that the amputee can be allocated depending on the level of amputation, the size of the bone, and the amount of bone contact with the implant. At the beginning of rehabilitation the fail-safe is set low to protect the poorer bone and bone-implant interface. The settings are gradually increased during rehabilitation to 60Nm, 80Nm or 100Nm in bending and 10Nm, 15Nm and 25Nm in torsion for high, medium and low risk amputees respectively.

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.
Includes bibliographical references (p. 155-164).
The focus of this thesis is the modeling, characterization, and improvement of microfabricated electrodes for the Retinal Implant Project. The ultimate goal of the Project is to build a retinal prosthesis able to restore a limited degree of visual function in people suffering from certain types of blindness. An important step in this process is the design and fabrication of a safe, efficient, and effective electrode array. Designing such an array will require a detailed understanding of electrode properties and accurate models for their electrical and chemical behavior. This thesis represents a few initial steps towards that goal. Besides providing useful data on the current arrays, it is hoped that this thesis will also provide a good general introduction to electrode modeling and help others in the research group better understand the devices they are using. The thesis followed four main steps. The first step was to find an appropriate circuit model for the behavior of microfabricated electrodes in an electrolyte. After some preliminary observations, the Randles model was chosen as a convenient starting point. Several aspects of this model were discussed, including its impact on electrode design, its expected behavior using different measurement techniques, and its major limitations. The second step was to calculate experimental values for the individual elements in the model. This was done for a number of different electrode designs under various physical conditions. The data was collected using several different electrochemical measurement techniques, each of which was explained in reasonable detail. The third step was to understand the physical basis of each model parameter and find chemical or physical theories to explain and predict the observed values. This modeling work focused on the series resistance and double layer capacitance. The resistance was well fit by a recessed disk model with an additional term for the oxide film. Several important aspects of the capacitance scaling were explained by a simple model involving nonuniform current density at the electrode surface, but a great deal of work remains to be done in this area. The final step of the thesis was to suggest possible improvements on the current electrode design and point out several directions for future work.
by Kenneth L. Roach.
M.Eng.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 45-47).
and sometimes even surpass, the capabilities and aesthetics of the natural human body. A prosthesis is carefully designed to provide optimal functionality to assist the amputee in returning back to her normal daily activities as much and as independently as is possible. However, when an amputee wears her prosthesis, the prosthesis also becomes a part of her body image and feminine identity. She requires a prosthesis that aligns aesthetically with her body image just as much as she requires comfort and functionality. In designing for a female amputee, the focus needs to shift from a purely functional or aesthetic perspective to one that sees the whole woman that is the female amputee and works to design her the right tools that will help her reach her goals. The current prosthesis design process does not account for the importance of latent needs related to the feminine identity of female amputees. These unaddressed needs can contribute to issues of poor body image and lower levels of life satisfaction with prosthetic devices. Embracing latent, aesthetic needs early in the prosthesis design process can help lead prosthetists to more informed design decisions and increased prosthesis user satisfaction. In this thesis, use case diagrams are developed to define the scope of a female's interactions with the items in her feminine wardrobe, as clothes are a crucial part of expressing one's feminine identity. The diagrams allow the identification of areas of identity that will be most affected as a result of a particular amputation. Using the three use case diagrams in this thesis as inspiration, prosthetists can work with amputees to develop requirements that address both explicit and latent needs, and design prostheses that are more appropriate for the female gender.
by Debbie Diem Nguyen.
S.M.

Upper-limb myoelectric prostheses are controlled by muscle activity information recorded on the skin surface using electromyography (EMG). Intuitive prosthetic control can be achieved by deploying statistical and machine learning (ML) tools to decipher the user's movement intent from EMG signals. This thesis proposes various means of advancing the capabilities of non-invasive, ML-based control of myoelectric hand prostheses. Two main directions are explored, namely classification-based hand grip selection and proportional finger position control using regression methods. Several practical aspects are considered with the aim of maximising the clinical impact of the proposed methodologies, which are evaluated with offline analyses as well as real-time experiments involving both able-bodied and transradial amputee participants. It has been generally accepted that the EMG signal may not always be a reliable source of control information for prostheses, mainly due to its stochastic and non-stationary properties. One particular issue associated with the use of surface EMG signals for upper-extremity myoelectric control is the limb position effect, which is related to the lack of decoding generalisation under novel arm postures. To address this challenge, it is proposed to make concurrent use of EMG sensors and inertial measurement units (IMUs). It is demonstrated this can lead to a significant improvement in both classification accuracy (CA) and real-time prosthetic control performance. Additionally, the relationship between surface EMG and inertial measurements is investigated and it is found that these modalities are partially related due to reflecting different manifestations of the same underlying phenomenon, that is, the muscular activity. In the field of upper-limb myoelectric control, the linear discriminant analysis (LDA) classifier has arguably been the most popular choice for movement intent decoding. This is mainly attributable to its ease of implementation, low computational requirements, and acceptable decoding performance. Nevertheless, this particular method makes a strong fundamental assumption, that is, data observations from different classes share a common covariance structure. Although this assumption may often be violated in practice, it has been found that the performance of the method is comparable to that of more sophisticated algorithms. In this thesis, it is proposed to remove this assumption by making use of general class-conditional Gaussian models and appropriate regularisation to avoid overfitting issues. By performing an exhaustive analysis on benchmark datasets, it is demonstrated that the proposed approach based on regularised discriminant analysis (RDA) can offer an impressive increase in decoding accuracy. By combining the use of RDA classification with a novel confidence-based rejection policy that intends to minimise the rate of unintended hand motions, it is shown that it is feasible to attain robust myoelectric grip control of a prosthetic hand by making use of a single pair of surface EMG-IMU sensors. Most present-day commercial prosthetic hands offer the mechanical abilities to support individual digit control; however, classification-based methods can only produce pre-defined grip patterns, a feature which results in prosthesis under-actuation. Although classification-based grip control can provide a great advantage over conventional strategies, it is far from being intuitive and natural to the user. A potential way of approaching the level of dexterity enjoyed by the human hand is via continuous and individual control of multiple joints. To this end, an exhaustive analysis is performed on the feasibility of reconstructing multidimensional hand joint angles from surface EMG signals. A supervised method based on the eigenvalue formulation of multiple linear regression (MLR) is then proposed to simultaneously reduce the dimensionality of input and output variables and its performance is compared to that of typically used unsupervised methods, which may produce suboptimal results in this context. An experimental paradigm is finally designed to evaluate the efficacy of the proposed finger position control scheme during real-time prosthesis use. This thesis provides insight into the capacity of deploying a range of computational methods for non-invasive myoelectric control. It contributes towards developing intuitive interfaces for dexterous control of multi-articulated prosthetic hands by transradial amputees.

Background: Tooth loss has a negative impact on patients’ general health and wellbeing. Dental prostheses can restore oral function, aesthetics and improve oral health related quality of life. Preferences for dental prostheses cannot be fully captured using existing clinical studies and questionnaires. Discrete choice experiment (DCE) is a novel method in health economics to elicit people’s preference for treatments and it allows the researcher to integrate all aspects relevant to treatment into evaluation and measurement of interrelationship between factors. The aim of this PhD thesis is to use a mixed method of DCE and qualitative interviews to analyse dentists and patient’s preferences for dental prosthesis choices in replacing missing teeth. Methods: Discrete choice experiment questionnaires were developed, describing dental prosthdontic treatments in multi-dimensions, including outcome, process and economic factors. Survey and analysis using the questionnaires were conducted with dentists and patients in Edinburgh. Qualitative interviews with Edinburgh dentists and patients were carried out to derive factors to aid the DCE questionnaire design and provide in-depth understanding of DCE results. Systematic reviews were performed to summarise existing evidence on prosthesis evaluation in traditional quantitative studies and perception of prostheses in qualitative interviews. The current application of DCEs in dentistry was also systematically reviewed. Results: Treatment longevity was identified as the most important factor for dentists and patients’ treatment decisions of anterior missing tooth replacements, followed by appearance and chewing function. Dentists put more value on fixation/comfort and treatment procedure than patients. Patients cared about cost of treatment whereas dentists were relatively insensitive. Gender, age and treatment experience significantly influenced patients’ preference for treatment characteristics. Dental implant supported crown was preferred by dentists, whereas patients gave higher utility to traditional prosthodontic treatments. The monetary benefit of fixed dental prostheses ranged from £1856 -£3848 for patients, far exceeding their willingness-to-pay (WTP), which was £120 - £240. Dentists were willing to pay £600-£3000, more than the perceived benefit £503 to £1649. Qualitative study identified the above factors and provided interpretation of DCE results. Problems in the dental care system related to referral and training for dental implant treatments were raised. Discussion: This thesis is the first DCE application in dentistry evaluating and comparing dentists and patients preferences for missing tooth replacements. Dentists and patients’ preferences were elicited qualitatively and qualitatively integrating multidimensional factors. Patients’ preference for treatments, monetary benefit and WTP were demonstrated to be different from dentists’. Treatment benefits exceeded patients WTP for fixed dental prostheses.

[ES] Mucha gente en el mundo se ve afectada por la pérdida de una extremidad (las predicciones estiman que en 2050 habrá más de 3 millones de personas afectadas únicamente en los Estados Unidos de América). A pesar de la continua mejora en las técnicas de amputación y la prostética, vivir sin una extremidad sigue limitando las actividades de los afectados en su vida diaria, provocando una disminución en su calidad de vida. En este trabajo nos centramos en los casos de amputaciones de extremidades superiores, entendiendo por ello la pérdida de cualquier parte del brazo o antebrazo. Esta tesis trata sobre el control mioeléctrico (potenciales eléctricos superficiales generados por la contracción de los músculos) de prótesis de extremidades superiores. Los estudios en este campo han crecido exponencialmente en las últimas décadas intentando reducir el hueco entre la parte investigadora más dinámica y propensa a los cambios e innovación (por ejemplo, usando técnicas como la inteligencia artificial) y la industria prostética, con una gran inercia y poco propensa a introducir cambios en sus controladores y dispositivos. El principal objetivo de esta tesis es desarrollar un nuevo controlador implementable basado en filtros adaptativos que supere los principales problemas del estado del arte. Desde el punto de vista teórico, podríamos considerar dos contribuciones principales. Primero, proponemos un nuevo sistema para modelar la relación entre los patrones de la señales mioélectricas y los movimientos deseados; este nuevo modelo tiene en cuenta a la hora de estimar la posición actual el valor de los estados pasados generando una nueva sinergia entre máquina y ser humano. En segundo lugar, introducimos un nuevo paradigma de entrenamiento más eficiente y personalizado autónomamente, el cual puede aplicarse no sólo a nuestro nuevo controlador, sino a otros regresores disponibles en la literatura. Como consecuencia de este nuevo protocolo, la estructura humano-máquina difiere con respecto del actual estado del arte en dos características: el proceso de aprendizaje del controlador y la estrategia para la generación de las señales de entrada. Como consecuencia directa de todo esto, el diseño de la fase experimental resulta mucho más complejo que con los controladores tradicionales. La dependencia de la posición actual de la prótesis con respecto a estados pasados fuerza a la realización de todos los experimentos de validación del nuevo controlador en tiempo real, algo costoso en recursos tanto humanos como de tiempo. Por lo tanto, una gran parte de esta tesis está dedicada al trabajo de campo necesario para validar el nuevo modelo y estrategia de entrenamiento. Como el objetivo final es proveer un nuevo controlador implementable, la última parte de la tesis está destinada a testear los métodos propuestos en casos reales, tanto en entornos simulados para validar su robustez ante rutinas diarias, como su uso en dispositivos prostéticos comerciales. Como conclusión, este trabajo propone un nuevo paradigma de control mioélectrico para prótesis que puede ser implementado en una prótesis real. Una vez se ha demostrado la viabilidad del sistema, la tesis propone futuras líneas de investigación, mostrando algunos resultados iniciales.
[CA] Molta gent en el món es veu afectada per la pèrdua d'una extremitat (les prediccions estimen que en 2050 hi haurà més de 3 milions de persones afectades únicament als Estats Units d'Amèrica). Malgrat la contínua millora en les tècniques d'amputació i la prostètica, viure sense una extremitat continua limitant les activitats dels afectats en la seua vida diària, provocant una disminució en la seua qualitat de vida. En aquest treball ens centrem en els casos d'amputacions d'extremitats superiors, entenent per això la pèrdua de qualsevol part del braç o avantbraç. Aquesta tesi tracta sobre el control mioelèctric (potencials elèctrics superficials generats per la contracció dels músculs) de pròtesis d'extremitats superiors. Els estudis en aquest camp han crescut exponencialment en les últimes dècades intentant reduir el buit entre la part investigadora més dinàmica i propensa als canvis i innovació (per exemple, usant tècniques com la intel·ligència artificial) i la indústria prostètica, amb una gran inèrcia i poc propensa a introduir canvis en els seus controladors i dispositius. Aquesta tesi contribueix a la investigació des de diversos punts de vista. El principal objectiu és desenvolupar un nou controlador basat en filtres adaptatius que supere els principals problemes de l'estat de l'art. Des del punt de vista teòric, podríem considerar dues contribucions principals. Primer, proposem un nou sistema per a modelar la relació entre els patrons de la senyals mioelèctrics i els moviments desitjats; aquest nou model té en compte a l'hora d'estimar la posició actual el valor dels estats passats generant una nova sinergia entre màquina i ésser humà. En segon lloc, introduïm un nou paradigma d'entrenament més eficient i personalitzat autònomament, el qual pot aplicar-se no sols al nostre nou controlador, sinó a uns altres regresors disponibles en la literatura. Com a conseqüència d'aquest nou protocol, l'estructura humà-màquina difereix respecte a l'actual estat de l'art en dues característiques: el procés d'aprenentatge del controlador i l'estratègia per a la generació dels senyals d'entrada. Com a conseqüència directa de tot això, el disseny de la fase experimental resulta molt més complex que amb els controladors tradicionals. La dependència de la posició actual de la pròtesi respecte a estats passats força a la realització de tots els experiments de validació del nou controlador en temps real, una cosa costosa en recursos tant humans com de temps. Per tant, una gran part d'aquesta tesi està dedicada al treball de camp necessari per a validar el nou model i estratègia d'entrenament. Com l'objectiu final és proveir un nou controlador implementable, l'última part de la tesi està destinada a testar els mètodes proposats en casos reals, tant en entorns simulats per a validar la seua robustesa davant rutines diàries, com el seu ús en dispositius prostètics comercials. Com a conclusió, aquest treball proposa un nou paradigma de control mioelèctric per a pròtesi que pot ser implementat en una pròtesi real. Una vegada s'ha demostrat la viabilitat del sistema, la tesi proposa futures línies d'investigació, mostrant alguns resultats inicials.
[EN] Many people in the world suffer from the loss of a limb (predictions estimate more than 3 million people by 2050 only in the USA). In spite of the continuous improvement in the amputation rehabilitation and prosthetic restoration, living without a limb keeps limiting the daily life activities leading to a lower quality of life. In this work, we focus in the upper limb amputation case, i.e., the removal of any part of the arm or forearm. This thesis is about upper limb prosthesis control using electromyographic signals (the superficial electric potentials generated during muscle contractions). Studies in this field have grown exponentially in the past decades trying to reduce the gap between a fast growing prosthetic research field, with the introduction of machine learning, and a slower prosthetic industry and limited manufacturing innovation. This thesis contributes to the field from different perspectives. The main goal is to provide and implementable new controller based on adaptive filtering that overcomes the most common state of the art concerns. From the theoretical point of view, there are two main contributions. First, we propose a new system to model the relationship between electromyographic signals and the desired prosthesis movements; this new model takes into account previous states for the estimation of the current position generating a new human-machine synergy. Second, we introduce a new and more efficient autonomously personalized training paradigm, which can benefit not only to our new proposed controller but also other state of the art regressors. As a consequence of this new protocol, the human-machine structure differs with respect to current state of the art in two features: the controller learning process and the input signal generation strategy. As a direct aftereffect of all of this, the experimental phase design results more complex than with traditional controllers. The current state dependency on past states forces the experimentation to be in real time, a very high demanding task in human and time resources. Therefore, a major part of this thesis is the associated fieldwork needed to validate the new model and training strategy. Since the final goal is to provide an implementable new controller, the last part of the thesis is devoted to test the proposed methods in real cases, not only analyzing the robustness and reliability of the controller in real life situations but in real prosthetic devices. As a conclusion, this work provides a new paradigm for the myoelectric prosthetic control that can be implemented in a real device. Once the thesis has proven the system's viability, future work should continue with the development of a physical device where all these ideas are deployed and used by final patients in a daily basis.
The work of Carles Igual Bañó to carry out this research and elaborate this dissertation has been supported by the Ministerio de Educación, Cultura y Deporte under the FPU Grant FPU15/02870. One visiting research fellowships (EST18/00544) was also funded by the Ministerio de Educación, Cultura y Deporte of Spain.
Igual Bañó, C. (2021). Co-adaptive myoelectric control for upper limb prostheses [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/168192
TESIS

Despite the technological advances of the twentieth century, we are not yet able to produce artificial limbs which "mimic" perfectly their natural counterparts. In general, artificial limbs are not as dextrous as human limbs, the control is unnatural and there is no proper feedback by which the user can assess the status of the prosthesis. In this thesis the problems related to upper-limb prostheses are considered. The use of a special material known as Shape Memory Alloy (SMA) is investigated towards producing improved joint actuators for small artificial prostheses such as those required by young children. SMA actuators can be very lightweight, their motion is silent and smooth and yet they are capable of delivering considerable power per unit of weight. The Shape Memory phenomenon and the many challenges involved in its application are discussed. The detailed design of an SMA joint actuator for a hand mechanism in an above-elbow prosthesis for young children is given. To assist the design and construction of both the artificial hand and the actuator, a mathematical model was developed and incorporated in a computer program simulating the forces and movements within the hand. The model was used to optimise the hand mechanism and specify the required joint actuator. Suitable SMA elements were identified through laboratory tests. The hand mechanism was constructed and the actuator, control systems and power source were attached to it. Tests were performed to investigate the characteristics of the complete device. The results show that, although SMA actuators must be designed and used with great care, they do offer a viable and more natural alternative to conventional actuators such as pneumatic devices and electric motors in certain applications.

Since the first Total Hip Arthroplasty (THA) performed in the 60's, it has been regarded among the most successful surgical procedures. When an un-cemented hip prosthesis is employed, the prosthesis is impacted into a prepared cavity in the femur. This surgical technique is known as impact bone grafting and is commonly used in THA. The stability of the prosthesis immediately after surgery is denoted primary stability.Numerical analyses of primary stability, often assume the forces applied during impact grafting to be lower than those present during routine activity. The magnitude of the forces applied during impact grafting is regarded a point of uncertainty, questioning this assumption. As the forces applied during impact grafting are equalized by frictional and contact forces, frictional characteristics present between prosthesis and femur could influence the primary stability of the prosthesis. The influence of grafting force magnitude and frictional characteristics on primary stability is investigated in this thesis. A study of scientific publications on primary stability was performed, forming the basis for the further analyses. External loads, mechanical properties and recommended practice with regard to numerical analysis of THA, were based on findings from this literature study.The performed analyses are purely numerical, using state of the art finite element software. The numerical model's response is verified, but as no experimental results are available on the particular geometry, validation is difficult. Two parametric studies were performed, investigating the influence of the impaction force magnitude and friction characteristics on micro motion.The friction coefficient was found to influence the primary stability of the prosthesis. An intermediate friction coefficient yielded the highest stability, with the same loads applied in all cases. Based on this finding, the influence of prosthesis-bone interface lubrication was investigated. A preliminary reduced friction coefficient during impact grafting yielded an enhanced primary stability, motivating further investigation of the concept. The magnitude of the impaction force was found to influence the primary stability of the prosthesis. An increased force magnitude above 240% of the patient bodyweight yielded an enhanced primary stability. This finding motivates a further investigation of the force magnitudes present during surgery.In order to extend the numerical model to include non-linear friction characteristics, a subroutine is proposed. The friction model's behavior is verified in this thesis, but further implementation is required.

Healthy vasculature possesses a single layer of vascular endothelial cells on the interior lumen of the vessel. It is these cells that are responsible for the non-thrombogenicity of the natural blood vessel lumen. The generation of this layer on the surface of an artificial graft could provide the necessary non-thrombogenic properties to the artificial prosthesis. In this work, synthetic cell adhesion peptides were designed, synthesized and chemisorbed onto the surface of a gold coated polyurethane. The polymer substrate was chosen in order to maintain good mechanical properties in the artificial vein or artery, while the gold coating served the purpose of permitting surface modification with the cell adhesion peptides. The peptides were custom designed to specifically be active to cell surface receptors on vascular endothelial cells. The peptides also contained a thiol present in a cysteine amino acid which was necessary for interaction with the gold on the polymer surface. The modifications to the surface were confirmed by various methods including water contact angles, and surface analysis techniques such as: x-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy. The surfaces were tested for their ability to promote the initial attachment of both vascular endothelial cells and mouse 3T3 fibroblasts. (Abstract shortened by UMI.)

The objective of prostheses and of dynamic orthoses is to provide restorative function to anatomical joints of the upper or lower limb that are either absent or physiologically compromised. This study considers the volitional demands of upper limb function and the periodic requirements of the lower limb during gait. Control strategies using discrete magneto-transducers to measure normal residual physiological activities which predict intended joint positions of dysfunctional or absent joints in the lower or upper limb, have been investigated and tested by experiment. The restoration of ankle dorsiflexion in hemiplegics with drop foot using functional electrical stimulation (FES) has been investigated. FES is traditionally controlled using a pressure switch in the heel of the shoe switching the stimulation on only when the foot is not weight bearing. However functional and cosmetic constraints of this method of control do not make it universally acceptable. A novel FES controller using a magneto-transducer to measure the cyclic variation of angular velocity of the leg through the knee has been developed. Experimentation with this controller showed that reliable switching of FES during successive gait cycles was possible in some patients with a hemiplegic drop foot. Most powered prosthetic prehensors and wrist units are controlled using the myoelectric activity of muscles. Such prostheses however have no intrinsic relationship between the position of the prosthetic prehensor and wrist unit and hence a degree of conscious effort in their control is required. A powered prosthetic prehensor and wrist unit has been developed using magneto-transducers which sense the myokinemetric activity of muscles dedicated to grasping and which measure forearm rotation. Reliable volitional control of the position of prosthetic prehension and wrist rotator has been demonstrated over several cycles of grasping and wrist rotation.