Prosthetic socket fitting is achieved by the prosthetist applying artisan techniques which are skill dependent and of subjective nature. This study investigates the use of finite element (FE) modelling techniques to predict the biomechanical behaviour at the residual limb/socket interface for the purpose of obtaining a quantitative evaluation of socket fit. Three dimensional FE models of the residual limb of trans-femoral amputees were generated based on geometrical data obtained using a mechanical digitizer and magnetic resonance (MR) imaging techniques. The inter-segmental loadings at the amputee's hip during standing and walking were applied to the FE models. These were measured with the aid of force platforms and infrared cameras. The material characteristic is introduced to the FE models were obtained by testing the residual limb's soft tissue with a computer controlled mechanical indentor. The FE models were validated by comparing predicted and measured pressures at the inter face between the residual limb and the socket. The majority of the FE prediction erred within 70% of the measured values. Detailed internal geometry of two trans-femoral amputees' residual limb in its natural shape and wearing quadrilateral and ischial containment type sockets was studied using MR imaging techniques. At the ischial level, the maximum difference in cross sectional area between the muscles of the sound limb and the residual limb was approximately 62%. The difference in muscles' size can be attributed to muscle atrophy in the residual limb or an increase in the muscle bulk in the sound limb. At similar level, the cross sectional area of the rectus femoris in the residual limb was reduced by as much as 68% from its natural shape when wearing the quadrilateral socket. Based on the acquired MR images,a two dimensional FE model of a transverse section 30 mm below the ischium was modelled. The model incorporated the interface characteristics between the muscles and intermuscular tissues. The maximum stress was recorded inside the residual limb near muscles/intermuscular tissue interface and at muscles/bone interface. The FE models generated have shown the potential of predicting stresses and deformation at the residual limb.

Persons with transfemoral (above knee) and transtibial (below knee) prostheses experience changes in the volume of their residual limb during the course of the day. These changes in volume unavoidably lead to changes in quality of fit of the prosthesis, skin irritations, and soft tissue injuries. The associated pain and discomfort can become debilitating by reducing one's ability to perform daily activities. While significant advancements have been made in prostheses, the undesirable pain and discomfort that occurs due to the volume change is still a major challenge that needs to be solved. The overall goal of this research is to develop smart prosthetic sockets that can accommodate for volume fluctuations in the residual limb. In this research, fluidic flexible matrix composite wafers (f2mc) are integrated into the prosthetic socket for volume regulation. The f2mc's are flexible tubular elements embedded in a flexible matrix. These tubular elements are connected to a reservoir, and contain an internal fluid such as air or water. Fluid flow between the tubes and reservoir is controlled by valves. A linear finite element model has been created to better understand output response and stiffness of the f2mc wafers for different design variables. Results demonstrate that wind angle, latex thickness, and material selection can be used to tailor the wafers for different applications. Through experiments, f2mc's have been shown to achieve nearly 100% strain through the thickness when pressurized to about 482.6 kPa (70 psi). The displacement results shown through these tests show great promise in applications of socket integration to compensate for volume change. / Master of Science

For pediatric amputees in developing countries, where characteristically rapid growth of children is compounded by a lack of medical services, maintaining proper socket fit is a challenging but necessary endeavor. A socket design that adjusts for radial and longitudinal growth will allow patients to wear the same socket for a longer period of time saving them the expense of subsequent fittings and hardware. Manufacture of such a socket poses a challenge for contemporary manufacturing processes. Due to its ability to rapidly manufacture complex part geometries, Selective Laser Sintering (SLS) is particularly suited to this application. Several preliminary design concepts for a volume adjustable transtibial SLS prosthetic socket for pediatric amputees in developing countries have been generated. These current design concepts utilize fasteners such as ratchet hooks and threads. Results from design and validation of theoretical models of these fastener concepts are the focus of this thesis. / text

For many years, the biggest issue that causes discomfort and hygiene issues for patients with lower limb amputations have been the interface between body and prosthetic, the socket. Often made of an inflexible, solid polymer that does not allow the residual limb to breathe or perspire and with no consideration for the changes in size and shape of the human body caused by changes in temperature or environment, inflammation, irritation and discomfort often cause reduced usage or outright rejection of the prosthetic by the patient in their day to day lives. To address these issues and move towards a future of improved quality of life for patients who suffer amputations, Loughborough University formed the Next Generation Prosthetics research cluster. This work is one of four multidisciplinary research studies conducted by members of this research cluster, focusing on the area of Computer Aided Design (CAD) for improving the interface with Additive Manufacture (AM) to solve some of the challenges presented with improving prosthetic socket design, with an aim to improve and streamline the process to enable the involvement of clinicians and patients in the design process. The research presented in this thesis is based on three primary studies. The first study involved the conception of a CAD criteria, deciding what features are needed to represent the various properties the future socket outlined by the research cluster needs. These criteria were then used for testing three CAD systems, one each from the Parametric, Non Uniform Rational Basis Spline (NURBS) and Polygon archetypes respectively. The result of these tests led to the creation of a hybrid control workflow, used as the basis for finding improvements. The second study explored emerging CAD solutions, various new systems or plug-ins that had opportunities to improve the control model. These solutions were tested individually in areas where they could improve the workflow, and the successful solutions were added to the hybrid workflow to improve and reduce the workflow further. The final study involved taking the knowledge gained from the literature and the first two studies in order to theorise how an ideal CAD system for producing future prosthetic sockets would work, with considerations for user interface issues as well as background CAD applications. The third study was then used to inform the final deliverable of this research, a software design specification that defines how the system would work. This specification was written as a challenge to the CAD community, hoping to inform and aid future advancements in CAD software. As a final stage of research validation, a number of members of the CAD community were contacted and interviewed about their feelings of the work produced and their feedback was taken in order to inform future research in this area.

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Preface: The research about product development of a prosthetic socket was conducted by two students from Mälardalen University, department of Innovation, Design, and Technology. Background: The most recent public survey shows that an estimated 5 million people in China are amputees, out of which a significantly large portion are below-elbow amputees. Sockets sold to below-elbow amputees are equipped with only two surface electromyography sensors, has low comfortability, has problems with perspiration, and a high weight. The current standard for socket manufacturing has not changed in decades. Research Questions: The following research questions have determined the direction of the research: (1) What measurable factors contribute to a convenient and ergonomic feature design in prosthetic socket from the end-user’s perspective? (2) How can the weight and functionality be improved to achieve a prosthetic socket more suited to the end-user, with respect to the existing prosthetic socket? (3) Which material and manufacturing method is suitable for producing cost-effective and customized prosthetic sockets? Research Method: The research was guided by the 5th edition of Product Design and Development by Ulrich & Eppinger (2012) where the product development process described in five of the six phases from planning to test and refinement were utilized. The data collection and analysis techniques performed in this research was guided by Research Methods for Students, Academics and Professionals by Williamson & Bow (2002). Interviews were conducted with five different stakeholders to find specifications of requirements and concretize subjectivism of what defines quality and ergonomics. Implementation: Currently, below-elbow amputees order sockets from orthopedic clinics. The socket was identified as a product of Ottobock. Investigations were made to find optimal solutions to the specification of requirements. Results: The development of a socket concept was designed for additive manufacturing using a multi-jet fusion printer. Analysis: This concept had significant improvements to parameters: higher grade of customizability, 30 % reduced weight, 48 % cost reduction, a new production workflow with 93,5 % automation, and a 69 % reduction in manual work hours. Conclusions: The data of the research strongly indicate existing potentials in enhancing socket design techniques and outputs by implementation of additive manufacturing processes. This can prove to be beneficial for achieving more competitive prosthetics and associated services. / Förord: Denna forskning om produktutvecklingsprocessen av en armprotes genomfördes av två studenter från Mälardalens universitet, avdelningen för innovation, design och teknik. Bakgrund: Den senaste offentliga undersökningen visar att cirka 5 miljoner människor i Kina är amputerade, varav en betydligt stor del är under-armbågsamputerade. Armproteser som säljs till underarmsamputerade individer är utrustade med endast två yt-elektromyografiska sensorer, har låg komfort, har problem med perspiration och hög vikt. Den nuvarande standarden för armproteser har inte förändrats under årtionden. Forskningsfrågor: Följande forskningsfrågor har bestämt riktningen för forskningen: (1) Vilka mätbara faktorer bidrar till en praktisk och ergonomisk funktionsdesign i underarmsproteser ur slutanvändarens perspektiv? (2) Hur kan vikten och funktionaliteten förbättras för att åstadkomma en underarmsprotes som är bättre anpassad för slutanvändaren med avseende på den befintliga underarmsprotesen? (3) Vilket material och tillverkningsmetod är lämpligt för att producera kostnadseffektiva och anpassade underarmsproteser? Forskningsmetod: Forskningsmetoden styrdes av den femte upplagan av Product Design and Development av Ulrich & Eppinger (2012) där produktutvecklingsprocessen är uppdelad i sex faser. I denna forskning användes de fem första faserna från planering till testning och justering. Tekniker för datainsamling och analys som användes i denna forskning styrdes av Research Methods for Students, Academics and Professionals av Williamson & Bow (2002). Intervjuer genomfördes med fem olika intressenter för att hitta kravspecifikationer och för att konkretisera subjektivitet för vad som definierar kvalitet och ergonomi. Implementering:  Underarmsamputerade individer beställer för närvarande armproteser från ortopediska kliniker. Armprotesen identifierades som en produkt av Ottobock. Undersökningar gjordes för att hitta optimala lösningar för kravspecifikationen. Resultat: Konceptutvecklingen av en armprotes utformades för additiv tillverkning med hjälp av en multi-jet-fusion-skrivare. Analys: Det här konceptet hade betydande förbättringar av parametrar: högre grad av anpassningsbarhet, 30 % minskad vikt, 48 % kostnadsreduktion, ett nytt produktionsflöde med 93,5 % automatisering och en 69 % minskning av manuella arbetstider. Slutsatser: Data från denna forskning indikerar att det finns starkt potential för att förbättra designtekniker och utgångar av underarmsproteser genom implementering av additiva tillverkningsprocesser. Detta kan visa sig vara fördelaktigt för att uppnå mer konkurrenskraftiga proteser och tillhörande tjänster.