Dissertations / Theses on the topic 'Surgical and Prosthetic Design'

This study compared the emission rates of orthopaedic space suits to standard surgical clothing in a simulated surgical environment. Significant increases in particle and microbiological emission rates were found when space suits were used, providing mechanistic evidence to support the increased prosthetic joint infection rates observed in epidemiological studies and helping to inform surgeons about their choice of clothing. Surgeons should proceed with caution when using space suits during surgery, particularly total joint arthroplasty.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 24-25).
Introduction: The design of prosthetic limbs is a complicated problem that continues to receive significant attention in research labs and in industry throughout the world. The idea of getting a machine to match human performance is an enticing one, and thus research continues to pursue the challenge of designing devices that can replace the functionality lost via limb amputation. Designers of prosthetics for developing countries face similar challenges. However, that challenge is also supplemented with a number of other contextual factors and considerations that must be made as a designer. As described by Cummings', these factors are social, economic, cultural, and geographic, and also include locally available forms of technology and time and distance constraints. These considerations further complicate the design process, especially for an engineer inexperienced with designing for the developing world and unfamiliar with the specific developing world environment being designed for. These topics have been covered in bits and pieces throughout the literature; this document attempts to cover them all thoroughly and in a logical way. This thesis also aims to provide some mechanism by which the challenge of designing a prosthetic knee for the developing world can be broken down and tackled effectively to yield an appropriate knee design. As amputees in the developing world are often subject to an inescapable life of poverty because they are unable to work and support their families, there is a strong impetus to design effective limbs for this population. This document intends to help facilitate that process. This thesis is inspired by a prosthetic knee design project that began in the class Developing World Prosthetics at the Massachusetts Institute of Technology in its inaugural term, spring 2008. Though the project was successful in many ways, the design process maybe could have been more effective with a stronger foundation in all the areas that will be covered below. This thesis primarily uses literature review to provide insight into human gait and amputee characteristics, as well as developing world considerations for designers of prosthetic limbs. The aim is to provide a foundation by which one can design effective and appropriate prosthetic devices. A metric is also developed by which those developing world considerations can be managed, weighed and incorporated into the design. In this case, experience and observations from the author's work on prosthetics in India are used to assess the contexts and contributions of various developing world factors to the successful incorporation of a prosthetic knee design into that environment. The document uses India as a case study; however, the thesis should serve as a generalized manual for developing world prosthetic knee design. This document begins with a presentation of human gait characteristics presented in a variety of contexts that can be useful to the designer of a prosthetic knee for the developing world. Then, basic mechanical components that are often used in prosthetic knee design are described, using examples. Finally, a thorough description of the many developing world factors that must be understood to design a sustainable prosthetic knee are discussed, and a table is presented by which those factors can be simply reviewed.
by Karina N. Pikhart.
S.B.

Includes bibliographical references.
This dissertation outlines the conceptualisation, design, manufacture, assembly and experimental testing of an affordable anthropomorphic mechanical hand prosthesis. In many countries, upper-limb amputees lack access to prosthetic hand devices. Furthermore, currently available mechanical devices require a large amount of effort to actuate; fatiguing and frustrating patients who have no other alternative but to use them. Consequently, a need has arisen to provide a mechanical device that is affordable enough to be accessible to low and middle-income patients, is functional enough to allow users to easily perform their Activities of Daily Living (ADLs), and is aesthetically appealing enough to ensure that patients feel comfortable and confident when wearing it. Concept solutions of several mechanisms were identified and evaluated from which the final design was selected. Analytical force analysis was used to generate a mathematical model to analyse the response of each dynamic member in the hand. A linear relationship between the input-force and applied grasp-forces of the hand was identified. Finite Element Analysis (FEA) used to investigate the lateral and hyperextensive loading limits of the phalanges, generated results that corresponded well to the experimental outcomes. Amongst the utilised actuation mechanisms (levers, pulleys, tendon-wires, bearings and springs), the tendon-wires were of concern due to their repetitive tensile loading and relative movement with the phalanges. Tensile testing of various tendon-wires and endurance testing of the phalangeal tendon-channels, yielded a combination which surpassed the infinite life requirement of 1,200,000 loading cycles; with carbon-nylon contact wearing at the lowest rate as confirmed by gravimetric tests in accordance with ASTM F2025 (2000). Manufacture of the hand used rapid prototyping in combination with traditional machining methods and standard components, enabling a fully-assembled cost of R 11,628.37; below the required R 18,000 limit. Various power and precision grasping configurations were achieved and the contact forces satisfactorily maintained, using the hand’s built-in locking mechanism. Feedback gathered from the prosthetist and patients suggested making slight alterations to the hand’s aesthetics and to address minor functional challenges, such as the control of the closing trajectory for precision grasps.

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 85-86).
Researchers in the Global Engineering and Research Lab (GEAR Lab) at MIT have been actively working on an improved design of the most widely distributed prosthetic foot in India, known as the Jaipur Foot. By developing an ISO 22675 prosthetic foot life cycle tester, researchers in GEAR Lab can test the durability of the prosthetic designs and fulfill the life cycle requirements. This thesis explores the mechatronic design of an ISO 22675 prosthetic foot life cycle tester and its contribution towards establishing fatigue testing infrastructure for prosthetics in GEAR Lab. It is broken down into three sub-systems: mechanical design, electrical design, and control architecture. It also serves as a documentation file detailing the engineering design decisions that were made during the development of the project. By building upon a mechanical framework that was established by past researchers, mechanical redesigns were conducted on the force loading assembly and the pivoting loading platform. The redesigned mechanical assembly were tested to be able to sustain maximum test force level with a safety factor of at least 1.5. The redesigned structure also provides adjustability to four crucial geometric parameters specified by the ISO 22675 standard and enables testing of prosthetic foot ranging from 23 cm to 31 cm in length. In addition, a system control PCB was designed and developed to serve as an electrical communication hub for reliable communication between the host controller LabVIEW myRIO-1900, various sensors, and the two actuators responsible for applying the test force and rotating the loading platform. A control architecture was developed and implemented through a LabVIEW parallel timed loop control structure to execute the control loop at a rate of 1kHz to reliably control both the stepper motor and the servo in parallel, read sensor states and display system current real time state through a graphical user interface.
by ZhiYi Liang.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering

Over seven million Americans suffer from Chronic Venous Insufficiency (CVI), a painful and debilitating disease that affects the superficial and deep veins of the legs. Problems associated with CVI include varicose veins, bleeding, ulcerations, severe swelling, deep vein thrombosis, and pulmonary embolism, which may lead to death. The presence of CVI results from damaged (incompetent) one-way vein valves in leg veins. These valves normally allow forward flow of blood to the heart, and prevent blood from pooling at the feet. However, incompetent valves allow reflux of blood, causing clinical problems. There are few effective clinical therapies for treating CVI. Vein valve transplantation is a surgical option for treatment. However, it is often difficult to find suitable donor valves. Very few prosthetic valves developed in the past have demonstrated sufficient clinical or mechanical functionality. Persistent problems include thrombus formation, leaking valves, and valves that do not open at physiologic pressure gradient. The primary objective of this research was to develop a clinically relevant functional prosthetic vein valve. The novel prosthetic valve is flexible, biocompatible, has low thrombogenecity, and is easy to manufacture. It was designed to address well-defined consumer needs and functional design requirements. The valve was required to 1) withstand 300 mmHg of backpressure with leakage less than 1.0 mL/min, 2) open with a pressure gradient less than 5 mmHg, and 3) meet criteria 1 and 2 after 500,000 cycles of operation. The valve met these design requirements in bench testing. The valve can open with a pressure gradient of 2.6 0.7 mmHg, and can withstand 300 mmHg with leakage less than 0.5 mL/min. The valve remained functional after opening and closing over 500,000 times. The valve presented in this research is operationally functional, and is a potential solution for treating venous incompetence in CVI patients.

In this thesis a flexible leaflet polymeric prosthetic aortic heart valve was designed, manufactured, and tested. The prosthesis was designed with the aim of overcoming the need for anticoagulant therapy, which is required for current mechanical prostheses; while also having lifelong durability, which current bioprosthetic heart valves are not able to achieve. Inspired by the anisotropic architecture of collagen in the natural valve, a shortlist of polystyrene based block copolymers (BCPs), which can be processed to yield mechanically anisotropic materials, was proposed. The shortlist was evaluated based upon processability, biostability, ex vivo haemocompatibility, and a novel material performance index comprising the flexural modulus and the cyclic fatigue stress predicted by fracture mechanics methods. Polystyrene-block-polyethylene-polypropylene-block-polystyrene with 22 mol% polystyrene (SEPS22) was selected for further testing and use in the design. Haemocompatibility and calcification of the BCPs was assessed against reference materials. In measures of coagulation and thrombogenicity the BCPs were better than polyester, but worse than expanded polytetrafluoroethylene and pericardium graft materials. In measures of inflammation, the BCPs and polytetrafluoroethylene were better than polyester and pericardium. A durable heparin coating gave SEPS22 superior haemocompatibility compared to all the reference materials. The BCPs calcified less than pericardium, but calcification still accelerated failure. The technique of injection moulding discs of the BCP from a point was used to create a novel biaxial structure of cylindrical polystyrene domains. A combination of modelling and bench-scale injection moulding was used to select a point from which the prosthetic heart valve injection tool cavity should be filled. By simultaneously injecting at a point at the centre of the free edge of each leaflet, a bioinspired orientation was produced. Based upon hydrodynamic testing, a spherical form leaflet design was selected. The hydrodynamic performance of the complied with the ISO 5840 standard for cardiac valve prostheses, but the fatigue performance was inadequate due to the leaflets being thinner than specified due to manufacturer error. Fatigue prediction and finite element analysis were used to conjecture that correctly manufactured polymeric valves could theoretically reach the ISO limit, indicating that there is potential for polymeric prostheses to overcome the issues of durability and need for anticoagulation.

Existing methods that use a fringe projection technique for orthotic and prosthetic designs produce good results for the trunk and lower limbs; however, the devices used for this purpose are expensive. This thesis investigates the use of an inexpensive passive method involving 3D surface reconstruction from video images taken at multiple views. The design and evaluation methodology, consisting of a number of techniques suitable for orthotic and prosthetic design, is developed. The method that focuses on fitting the reference model (3D model) of an object to the target data (3D data) is presented. The 3D model is obtained by a computer program while the 3D data uses the shape-from silhouette technique in an approximately circular motion.

There is a significant worldwide demand for a small calibre vascular graft for use as a bypass or replacement conduit. Our lab has developed a novel nanocomposite poly- mer based on polyhedral oligomeric silsesquioxane and poly(carbonate-urea)urethane (POSS-PCU) which has displayed promising properties in vitro. In this thesis, POSS- PCU has been utilised to fabricate prosthetic small calibre conduits for use as arterial replacements. An important feature in determining the success of a graft is the wall structure which includes porosity, pore size and pore interconnectivity, which play a crucial role not only in determining the extent of graft healing but also on mechanical behaviour. A novel extrusion/phase inversion method was investigated and optimised to produce grafts with a range of pore sizes (0-30 μm) and porosities (up to 90%). With mismatches in mechanical properties implicated in the aetiology of intimal hyperplasia, the dynamic mechanical behaviour of grafts was investigated. Grafts could be engineered with compliance values ranging from 5 to 12 per mmHg x 10^-2 compared to an average value of 5.9 per mmHg x 10^-2 for the native artery. Biocompatibility is largely dependent on surface properties which were extensively characterised for each of the porous grafts. Grafts were found to readily endothelialise in vitro and were resistant to platelet activation. An external graft reinforcement method was developed in order to minimise graft kinking. Finally, the grafts were evaluated in vivo in an ovine model following GLP protocols for a period of 9 months. A patency rate of 70% was achieved (n=10). The positive in vitro results and successful conclusion to the large animal trial suggest that POSS-PCU small calibre grafts are a promising candidate for cardiovascular reconstructions.

Chronic Venous Insufficiency (CVI) is characterized by chronic venous hypertension from blood pooling in the lower limbs. The resulting symptoms include leg pain, varicose veins, fatigue, venous edema, skin pigmentation, inflammation, induration, and ulceration. Reflux from incompetent venous valves is a factor in up to 94% of individuals with CVI. Current treatments of CVI include compression stockings, drug therapy, vein disabling, venous stenting, and surgical correction with varying rates of success. However, a minimally invasive correction of deep venous reflux does not currently exist. A transcatheter prosthetic venous valve has the potential to be an effective, minimally invasive treatment for deep venous reflux which could treat up to 1.4 million individuals in the United States suffering from venous ulceration and make more than 1.7 billion dollars each year. Previously developed prosthetic venous valves have had problems with competency, patency, thrombogenicity, biocompatibility, and incorrect sizing. To meet the clinical need a prosthetic valve needs to be developed which succeeds where previous valves have failed. This thesis describes the design, analysis, pre-clinical testing, and evaluation of a novel prosthetic venous valve. Design specifications for an effective prosthetic venous valve were created. Verification tests were developed and performed which demonstrated that the valve met every design specification. Finite element and computational fluid dynamics simulations were performed to analyze the valve and calculated a maximum shear rate of 2300 s-1 in the valve during the high forward flow after a Valsalva maneuver. The valve is made of a biocompatible material that has low thrombogenicity, Poly(vinyl-alcohol) cryogel. On the average, the valve allows less than 0.5 mL/min of reflux at low and high retrograde pressures even after 500,000 cycles, indicating that it will reduce the reflux of individuals with venous reflux by more than 99.4%. The valve closes in less than 0.07 seconds and allows the distal pressure to rise to an average of 7% of the equilibrium pressure 30 seconds after a simulated ankle flexion. The valve increases the outflow resistance an average of 2.3 mmHg*min/L which is much less than obstruction levels,≥ 5 mmHg*min/L. The valve can fit in a 16 French catheter and is capable of percutaneous delivery. The base of the valve is 1.5 times the diameter of the vein in which it is to be implanted to help correct orientation upon deployment. Fluid behind the valve’s leaflets is ejected with a forward flow rate of 400 mL/min, suggesting that thrombus formation will not occur at this location. A stented valve remained patent in a porcine blood flow loop for 3 hours. The valve remains competent without buckling in a constricted vein at rest. The valve can expand to fit a vein with a maximum diameter 1.4 times the valve's initial diameter with low risk of tearing or leaflet prolapse. An IACUC protocol for a 12 week study to test the valve in sheep was prepared and approved. A study to evaluate the valve in humans is proposed with endpoints that can be tested for statistical significance and compared with other treatments for CVI. A set of valves which will correct reflux in the majority of common femoral, femoral, and popliteal deep veins is proposed and a sizing guide for surgeons is provided. The minimum distance between prosthetic valves placed in the same vein segment is 13 cm. A comparison of this valve with previously developed prosthetic venous valves and recommendations for work to be performed in the future are given. The valve proposed in this work is the only valve to meet all design specification for an effective prosthetic venous valve, and therefore shows great potential to be a minimally invasive treatment for deep venous reflux.

The objective of this thesis is to develop design approaches and models for prosthetic ankle joints using kinematic models of the human ankle and compliant mechanisms technology. Compliant mechanisms offer several potential design advantages over traditional rigid-body designs including high reliability and low cost. These design advantages are ideal for use in prosthetics. Some prosthetic ankle/foot systems currently on the market have multiple degrees of freedom yet are expensive. Additionally, even though these systems have multiple degrees of freedom, none of them are designed after the actual movements of the biological ankle. In this thesis a two, single degree-of-freedom hinge joint model, which is a kinematic model based on the biological ankle during walking, is used to develop compliant prosthetic ankle joints. The use of the model together with compliant mechanisms may provide the ability to develop highly functional prosthetic ankle joints at a lower cost than current high-performance prosthetic systems. Finally, a design approach for ankles may facilitate future development for knees, hips or other biological joints.

This report presents the design and manufacturing process of a bionic signal messagebroker (BSMB), intended to allow communication between implanted electrodes andprosthetic legs designed by Ossur. The BSMB processes and analyses the data intorelevant information to control the bionic device. The intention is to carry out eventdetection in the BSMB, where events in the muscle signal are matched to the events ofthe gait cycle (toe-o, stance, swing).The whole system is designed to detect muscle contraction via sensors implantedin residual muscles and transmit the signals wireless to a control unit that activatesassociated functions of a prosthetic leg. Two users, one transtibial and one transfemoral,underwent surgery in order to get electrodes implantable into their residual leg muscles.They are among the rst users in the world to get this kind of implanted sensors.A prototype of the BSMB was manufactured. The process took more time thanexpected, mainly due to the fact that it was decided to use a ball grid array (BGA)microprocessor in order to save space. That meant more complicated routing and higherstandards for the manufacturing of the board. The results of the event detection indicatethat the data from the implanted electrodes can be used in order to get sucient controlover prosthetic legs. These are positive ndings for users of prosthetic legs and shouldincrease their security and quality of life.It is important to keep in mind when the results of this report are evaluated that allthe testing carried out were only done on one user each.

Sub-gingival margin placement is sometimes required due to different reasons and is often associated with adverse periodontal reactions. The purpose of this study was to determine if a single restoration with subgingival margin on a tooth, in the maxillary anterior zone, would affect its periodontal soft tissue parameters, and whether or not a deep chamfer preparation has a different influence in the periodontium when compared to a feather edge preparation. Plaque and gingival indexes, periodontal probing depth, bleeding on probing and patient’s biotype were registered. 106 teeth were prepared with a deep chamfer, while 94 were prepared with a feather edge finishing line. Six and twelve month after the restorations delivery the same parameters were evaluated. Repeated measure one-way analysis of variance (ANOVA ) (α=0.05) was used. At six months the patient A statistically significant difference between baseline and the 6 and 12-month follow up is present in regards to plaque index, gingival index and periodontal probing depth, but no statistically significant difference between chamfer and feather edge finishing lines. There is a statistically significant difference between baseline and the 6 and 12-month follow up in regards to bleeding on probing. Feather edge preparation presents significantly more bleeding on probing and less gingival recession than the chamfer. Sub-gingival margins do influence the periodontal soft tissue response. Statistically significant difference exists between feather edge and chamfer finishing lines in regards to bleeding on probing and gingival recession. Subgingival margins should be carefully selected, especially when feather edge finishing line is utilized.

The physiological energy requirements of prosthetic gait in lower-limb amputees have been observed to be significantly greater than those for able-bodied subjects. However, existing models of energy flow in walking have not been very successful in explaining the reasons for this additional energy cost. Existing mechanical models fail to capture all of the components of energy cost involved in human walking. In this thesis, a new model is developed that estimates the physiological cost of walking for an able-bodied individual; the same cost of walking is then computed using a variation of the model that represents a bi-lateral below-knee amputee. The results indicate a higher physiological cost for the amputee model, suggesting that the model more accurately represents the relative metabolic costs of able-bodied and amputee walking gait. The model is based on a two-dimensional multi-body mechanical model that computes the joint torques required for a specified pattern of joint kinematics. In contrast to other models, the mechanical model includes a balance controller component that dynamically maintains the stability of the model during the walking simulation. This allows for analysis of many consecutive steps, and includes in the metabolic cost estimation the energy required to maintain balance. A muscle stress based calculation is used to determine the optimal muscle force distribution required to achieve the joint torques computed by the mechanical model. This calculation is also used as a measure of the metabolic energy cost of the walking simulation. Finally, an optimization algorithm is applied to the joint kinematic patterns to find the optimal walking motion for the model. This approach allows the simulation to find the most energy efficient gait for the model, mimicking the natural human tendency to walk with the most efficient stride length and speed.

Rupture of the anterior cruciate ligament (ACL) is a relatively common sports-related injury for which the current treatment is reconstruction with an autograft or allograft. Drawbacks associated with each of the current options would make a prosthetic alternative advantageous, however, artificial ligaments are not widely used, having failed due to lack of biocompatibility and mechanical insufficiencies. To develop the next-generation prosthetic ACL, design control principles were applied including specification of comprehensive design inputs, risk analysis, and verification testing. A design was proposed utilizing polyvinyl alcohol and ultrahigh molecular weight polyethylene, selected for good biocompatibility and mechanical strength and stiffness suitable for ACL replacement. A biomimetic fibrous rope pattern was designed for the intra-articular ligament section of the prosthetic that produced a close match the static tensile behavior of the native ACL and which also demonstrated good resistance to fatigue and creep. A calcium phosphate coating was recommended for the sections of the device lying within the bone tunnel to increase the rate of osseointegration. The proposed design was then evaluated in a computational simulation to assess functional restoration and the effects of installation parameters such as tension and tunnel orientation on knee kinematics. The encouraging results of preclinical verification testing support further in vivo evaluation of the proposed design.

The majority of prosthetic feet used in low-income countries suffer from a limited lifespan and limited durability. The aim of this project is to design a prosthetic foot suited to use in low-income countries that incorporates both durability and a high level of function. A review of the literature was carried out which included examining the form and function of the anatomical human foot and the existing prosthetic systems used in low-income countries as well as their limitations and successes. Also reviewed were methods of assessment of a prosthetic foot. A Product Design Specification (PDS) was created to outline the requirements of a prosthetic foot for use in a low-income country based on the information detailed in the literature review. An existing design of Strathclyde foot was tested statically according to the ISO 10328 standard. The design was modified to improve performance in identified areas followed by an evaluation of layered manufacturing processes. Having identified a potential manufacturing method for prototypes testing of materials was carried out to determine the suitability of these materials for testing. Samples of the new design were tested statically according to ISO 10328. The foot design was then further modified based on the test results, confirmed by the use of FEA at which point new prototypes were made and static testing was again carried out. A comparison of the Strathclyde foot to other feet used in low-income countries took place. The second redesign of the Strathclyde foot was assessed via force plate trials by a non-amputee subject wearing prosthetic stilts. Finally, conclusions were drawn with respect to achieving the PDS and further work was recommended to improve upon the existing design and reach the requirements of the PDS. Appendix A gives details of the roll-over shape testing carried out on a range of prosthetic feet while Appendix B details the FEA work carried out to support design modification.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 38-39).
The need for effective prostheses is prevalent worldwide, and is especially dire in developing countries and low-resource settings. The MIT GEAR Lab is addressing this gap through the ATKnee, a low-cost, passive prosthetic knee that employs the use of spring and damper components to replicate the knee torque of the able-bodied human knee. In this study, we build upon prior work to optimize the components used in the ATKnee by accounting for results from field-testing. We first develop an inverse dynamics model to confirm understanding of previous work. We then use a genetic optimization algorithm to optimize parameters across different walking speeds and various spring-damper configurations. The best fit, as measured by the highest R2 value, is obtained when a viscous damper is active during the first dissipative phase (b*11 ), a friction damper is active during the second dissipative phase (b*/20 ), and an additional friction damper is active throughout both phases (b*/0). We make the suggestion that b*/0 = 0.084, b*/11 = 0.008, b*/0 = 0.183, gives the most optimal passive system knee torque with the engagement and disengagement timings teng = 51.3%, tdis1 = 64.2% for the first damper, and teng2 = 86.1%, tdis2 = 95.2% for the second damper. We find that the parameters are robust to subject body mass, but show a positive correlation with walking speed. We conclude that while we are able to suggest an optimized parameter set that includes higher order dampers, it will be important to investigate the effects of cadence, as well as to study the joint torques at the hip, which is further from the foot.
by Krithika Swaminathan.
S.B.

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.

Orthopedic surgery is dangerous, especially for the surgeon! Tool failures belong to the ten most frequent causes of operation delays. Nowadays, hospitals are pressured to optimize procedures and lower costs. Especially, orthopedic surgery is physically demanding for the ergonomics of the surgeon and tools wear out more quickly. Could the evolution of a surgical power tool be used in these scenarios to ease and support the surgeons work, increase the efficiency and flexibility of usage and at the same time offer more control and knowledge about the condition of the tools?

Minimally Invasive Surgery (MIS) is a growing field including both laparoscopic androbotic operations. Surgeons and engineers are making continual efforts to reduce the negative effects of procedures on patients. Reducing the size of the surgical instruments is one effective method pursued in this effort. When the instruments approach 3 mm in diameter, they reach a threshold where the entry incisions can be small enough that no scar is left on the patient. Laparoscopic instruments on this scale exist but typically lack wrist articulation and only have 1 degree of freedom (DoF). Alternatively, robotic surgical instruments can achieve high levels of dexterity but at a greater diameter. Smaller diameter robotic instruments employ snake wrists but this results in large swept volumes. There is a need for smaller robotic instruments with 3 DoF that preserve a small operational volume. Several unique challenges result when trying to develop small-scale instruments. Friction forces due to the relative motion of actuation cables and other parts in the mechanisms become more significant, as do the challenges of producing and assembling parts with extremely small features. These challenges have been limiting factors for the size of instruments. Traditional mechanisms use pin joints and pulleys which result in higher part counts and higher internal friction. To overcome these challenges, two alternative designs that reduce part count and minimize friction are presented as potential mechanisms that could be used as surgical instruments on the mesoscale (1-5 mm). Both designs implement rolling contact and gearing in place of pin joints and pulleys to realize their motion. Additionally, alternative manufacturing methods that are ideally suited to mesoscale production are presented. Micro metal laser sintering and composite carbon nanotude structures are shown to have the resolution required to create the detailed features necessary for these new designs. The result are two mechanisms suited to be produced as mesoscale, robotically actuated, surgical instruments. One of the two designs has been physically prototyped and has demonstrated clinical capabilities at 4 and 5 mm diameter instrument sizes.

In surgery, suturing is the use of needle and thread to join cut and/or damaged anatomical structures together. This repair strategy is highly versatile and is universal for all types of surgery as the goal is to restore, repair or improve function and/or appearance. The needles are almost always curved in shape, and it is handled and maneuvered by surgeons with a special tool called: needle driver. The versatility of this setup has proven its worth over time as needle drivers are one of the indispensable instruments in all types of surgery. We are entering a future where robots can be programmed to execute tasks with much higher level of precision and speed compared to humans. Medical robotics in surgery has gained ground over the past decades due to promising clinical results. A straightforward step in this direction would be to create a solution that enables the robot to grip needle driver. The purpose of this study was to develop a gripper tool that enables a collaborative robot to perform suturing with one of the most common types of needle drivers used in surgery. The Double Diamond design framework was employed. The selected content in the predefined four phases were: 1) Discover: Observation, MoSCoW Prioritization, Brainstorming, Choosing a Sample, Fast Visualisation, 2) Define: Assessment criteria, 3) Develop: Physical prototyping 4) Deliver: Final testing and Evaluation. In the first phase, Discover, clinical and technical demands were formulated. In the second phase, Define, numerous design ideas were generated and drafted on paper whereof the one with highest assessment score was chosen for physical prototyping. In phase three, Develop, the selected design idea was modelled in cardboard, clay and silicon, and 3D printed. Multiple design iterations were guided by feedback from clinical and technical experts and resulted in a final prototype design that was accepted by the experts. In phase four, Deliver, the final prototype was subjected to final testing and evaluation. Observation of five live and one video recording of surgical procedures on real patients were made. The insights gained were confirmed with the lead and co-surgeons of each procedure and were summarized in 24 clinically important observations relevant for the gripper tool design. Careful analysis of the previously designed gripper tool, live observation of the robot’s motion pattern and range, and interview with robotic engineer were summarized in ten technically important observations. The observations were then used to formulate the clinical and technical demands that the gripper tool design aims to fulfill, followed by prioritizing the demands and design features according by MoSCoW method and brainstorming on how to improve previous gripper tool design. To limit the scope of the design challenge, one of the five types of needle drivers used in pediatric heart surgery in Lund was selected in the method Choosing a Sample. To further characterize the clinical and technical demands, a test bench was set up to Define and measure force vectors applied on the needle driver when held by a surgeon during suturing. The radial forces vectors in six directions perpendicular to the tip of the needle driver ranged from 1.6 N to 3.8 N. The axial force along the length of the needle driver was 7.6 N towards the tip and 8.4 N towards the back end. The clockwise and counterclockwise torque along the length axis of the needle driver was 0.2 Nm and 0.18 Nm, respectively. The set of defined demands were sufficient to sketch numerous ideas of gripper tool designs according to the Fast Visualization method. These designs were then used in the Define phase to communicate the design ideas with surgeons, robotic and product development engineers. The most promising idea was advanced to the Develop phase where physical prototypes were produced in cardboard, clay and silicon and 3D printed. Inadequacies were found during design feedback with interviews and testing together with clinical and technical experts, and design actions were taken to arrive at the final prototype. The final prototype was brought into the Deliver phase for final testing and evaluation. The gripper tool could handle lager force loads than the human surgeon in all the stability tests. However, deflection of the needle driver occurred with the gripper tool unlike when the surgeon was subject to stability testing. One pediatric heart surgeon and one robotic engineer was asked to generate a composite score of fulfillment rate from 1–5, where 1 is bad, 3 satisfactory, and 5 excellent after final testing of the gripper tool was carried out. The final prototype of the gripper tool fulfills all clinical and technical demands at the level of 4, and 3–5, respectively. In conclusion, the design methodology used in this study was useful in the development of a gripper tool design that respects both clinical and technical demands. This suggest that the methodology may be used in similar setting of design challenges in the field between medical and technical innovation. The gripper tool fulfilled the demands, although further refinement in the choice of material, further testing and investigation of regulatory aspects are required before it can be implemented in the operating room.
Vid operation är suturering användningen av nål och tråd för att sammanfoga snittad och/eller skadade anatomiska strukturer. Denna reparationsstrategi är mycket mångsidig och universell för alla typer av kirurgi eftersom målet är att återställa reparera eller förbättra funktion och/eller anatomisk defekt. Nålarna är nästan alltid krökta i sin form och de hanteras och manövreras av kirurgerna med ett speciellt verktyg som kallas: nålförare. Mångsidigheten i denna uppställning har visat sig över tid eftersom nålförare är ett av de oumbärliga instrumenten vid alla typer av operationer. Vi går in i en framtid där robotar kan programmeras för att utföra uppgifter med mycket högre precision och hastighet jämfört med människor. Medicinska robotar inom kirurgi har varit på frammarsch senaste årtionden på grund av goda kliniska resultat. Ett steg i denna riktning skulle vara att skapa en lösning som gör det möjligt för en robot att greppa nålföraren. Syftet med denna studie var att utveckla ett gripdon som möjliggör för en kollaborativ robot att utföra suturering med hjälp av en av de vanligaste typerna av nålförare som används vid operation. Design metodiken Double Diamond användes för att beskriva design processensen. Det valda metoderna i de fyra för definierade faser var: 1) Discover: Observation, MoSCoW Prioritization, Brainstorming, Choosing a Sample, Fast Vissualization, 2) Define: Assessment criteria, 3) Develop: Physical Prototyping, 4) Deliver: Final testing and Evaluation. I första fasen, Discover, formulerades kliniska och tekniska krav. I den andra fasen, Define, definierades flera designidéer som skissades på papper, varav den med den högsta poängen valdes i Assessment criteria. I fas tre, Develop, modellerades den valda designidén i kartong, lera och silikon samt 3D-printades. Flera designiterationer gjordes baserat på feedback från kliniska och tekniska experter vilket resulterade i en slutlig prototypdesign som godkändes av experterna. I fas fyra, Deliver, testades och utvärderades den slutliga prototypen. Observation av fem realtids och en videoinspelning av kirurgiska ingrepp på riktiga patienter gjordes. Insikterna som gjordes bekräftades med kirurgerna som genomförde operationen och sammanfattades i 24 kliniskt viktiga observationer som var relevanta för gripdon designen. Noggrann realtids observation av robotens rörelsemönster samt analys av det tidigare utformade gripdonen och intervju med en robotingenjör sammanfattades i tio tekniskt viktiga observationer. Observationerna användes för att formulera kliniska och tekniska krav som gripdons designen strävar efter att uppfylla, följt av prioritering av kraven och designegenskaper enligt MoSCoW-metoden och brainstorming kring hur tidigare gripdons design kan förbättras. För att begränsa designutmaningens omfattning valdes en av de fem typer av nålförare som används vid barnhjärtkirurgi i Lund genom metoden Chossing a sample. För att ytterligare karakterisera de kliniska och tekniska kraven upprättades en testbänk för att definiera och mäta kraftvektorer som appliceras på nålföraren när den hålls av en kirurg under suturering. De radiella krafterna i sex riktningar vinkelrätt mot nålförarens spets varierade från 1,6 N till 3,8 N. Den axiella kraften längs nålförarens längd var 7,6 N mot spetsen och 8,4 N mot bakänden. Medurs och moturs vridmoment längs nålförarens längdaxel var 0,2 Nm respektive 0,18 Nm. Dom definierade kraven låg till grund för skisser av flertal gripdondesign idéer enligt Fast Visualization. Dessa skisser användes sedan i Define fasen för att kommunicera designidéer med kirurger samt robot- och produktutvecklingsingenjörer. Den mest lovande idén togs till Develop fasen där fysiska prototyper togs fram i kartong, lera och silikon samt genom 3D-printning. Förbättringspunkter hittades under testning och återkoppling med intervjuer tillsammans med kliniska och tekniska experter. Designåtgärder baserat på återkopplingen gjordes för att komma fram till den slutliga prototypen. Slutlig testning och utvärdering av den slutliga prototypen genomfördes i Deliver fasen. Gripdons designen kunde hantera större belastningar än den mänskliga kirurgen i alla stabilitetstester. Böjning av nålföraren uppstod dock i testerna med gripverktyget till skillnad från testerna med kirurgen var föremål för stabilitetsprovning. En barnhjärtkirurg och en robotingenjör poängsatte uppfyllnadsgrad av de kliniska respektive tekniska kraven efter att slutlig testning av gripdonet utförts. Uppfyllnadsgraden poängsattes från 1–5 där 1 var dålig, 3 tillfredsställande och 5 utmärkt. Gripdonets slutliga prototyp uppfyller alla kliniska och tekniska krav på nivå 4 respektive 3–5. Designmetodiken som användes i denna studie var användbar för utvecklingen av gripdon som uppfyller både de kliniska och tekniska kraven. Detta tyder på att denna metod kan användas i liknande designutmaningar inom området mellan medicinsk och teknisk innovation. Gripdonet uppfyllde kraven även om ytterligare förfining i materialvalet, ytterligare testning och undersökning av regulatoriska aspekter krävs innan den kan användas under riktiga operationer i operationssalen.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 29).
Amputees in developing countries face a challenging prospect. Without an adequate prosthesis, they face a lifetime of limited mobility and dependence. Unfortunately, as millions fall below the poverty line and as such do not have access to proper medical and prosthesis care, many must resign themselves to such a lifestyle. Bhagwan Mahaveer Viklang Sahayata Samiti (BMVSS) is attempting to change this. BMVSS is the world's leading prosthetics and mobility provider, serving over 20,000 new individuals per year - all free of charge - in 27 countries. Through a partnership with a Stanford design course, the Jaipur-Stanford Knee, a novel prosthetic knee incorporating a four-bar design, was born. This knee design has become widely popular amongst amputees and was named one of the top 50 best inventions in 2009 by Time Magazine. However, despite the popularity and widespread media coverage of the knee's development, there currently exists no available technical literature on the design. This research provides a kinematic model of this knee to compare to the dynamics of a natural gait along with a materials analysis to offer insight into design and manufacture improvements in future design iterations and concepts.
by Casandra N. Ceri.
S.B.

The number of Total Glossectomy cases in the United States is seeing an increasing trend as per the Nationwide Inpatient Sample Database. Patients, who have undergone such aggressive surgical procedures, have extensive limitations performing basic oral functions such as swallowing (deglutition), eating and speaking. Current rehabilitation prostheses do little in restoring the functionality of the original tongue. This is true especially in deglutition, which is necessary to transfer a bolus to the esophagus. Such patients need advanced prosthetic devices and through this research, investigations into potential solutions for prosthetic tongues to aid in deglutition were carried out. The process began with an extensive literature review that provided tongue position, motion, and pressure data during the swallowing stages. Several potential designs were considered such as using linkages and pneumatic networks (PneuNets). Based on a decision matrix, PneuNets were adopted as the foundational basis for generating prosthetic designs. Several prototypes were fabricated using Fused Filament Disposition for mold development and silicone Eco-flex 00-30 for actuator development. Each iteration involved tackling several design and manufacturing challenges especially when scaling these actuators from an initial experiment to an anatomical shape and size of a human tongue. A tongue of dimensions 1.8 inches wide, 2.4 inches long and 0.24 inches thick was developed. The PneuNet actuator was powered by a pneumatic system and kinematic data was collected using a tracking software. The data gathered provided validation comparisons between position trends exhibited in the literature. Theoretical deflection models were generated for analyzing the deflection of the front, middle and back sections of the tongue prototype. Details from literature review, design iterations, simulations, validation processes, research challenges and conclusions will be discussed in depth.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 59-60).
Access to surgical care for people in remote settings and/or developing countries is limited: 30% of the world's population receives 75% of major operations [1]. In developing countries, up to a third of patients acquire a surgical site infection (SSI), which is nine times more likely than in developed countries [2]. An estimated 85,500 cases of HIV and hepatitis are contracted by obstetrical/gynecological providers every year, and 90% of those cases are the result of treating patients living in poverty. SurgiBox aims to address these issues by providing a portable, sterile operating environment for use in austere settings. Not only are patients protected from environmental hazards through the use of SurgiBox, but medical personnel are also shielded from patient fluids, blood, and aerosols. SurgiBox consists of a clear, disposable plastic enclosure that is adhered to the patient's surgical site and inflated with filtered air. Long gloves, similar those used in a glovebox, are integrated into the enclosure and used by the medical personnel to perform the surgery. Surgical instruments are sterilized before the surgery and are placed inside the enclosure prior to the procedure, but materials, or even a baby in the case of a cesarean section, can be passed in or out of the sterile field during the procedure through a resealable port. Particle count testing inside the enclosure shows that particle counts could be maintained at less than 25% of operating room standards for particles greater than 0.5 microns (OR standard: less than 83,000 particles/m3)and 0.3 microns (OR standard: less than 1,000,000 particles/m 3 ).
by Sally A. Miller.
S.M.

Robot-assisted minimally invasive surgery is used to perform intricate surgical tasks through small incisions using long, slender instruments. The miniaturization of these instruments is advantageous to both surgeon and patient because smaller instruments reduce trauma to surrounding tissue, decrease patient recovery times, and can be used in confined spaces otherwise inaccessible using larger instruments. However, miniaturization of existing designs is limited by friction between moving parts, the volume occupied by the end effector, and manufacturing and assembly constraints. The objective of this work is to develop and analyze concepts that can be used in robot-assisted needlescopic surgery. The concepts are intended for instrument shafts no larger than 3 mm in diameter. An ideal concept is one with large ranges of wrist and gripping motion. Concepts should also minimize friction and swept volume while maintaining a focus on manufacturability and ease of assembly. Multiple concepts were generated and evaluated using a tree classification scheme, proof-of-concept prototypes, and simplified mathematical models. Three unique concepts were further developed and tested—the Split CORE Grips, the Inverted Flexure Grips, and the Crossed Cylinders Wrist. The two grip concepts are instruments that incorporate one rotational degree of freedom and one gripping degree of freedom. The wrist concept incorporates two rotational degrees of freedom and could be coupled with a single DOF grip mechanism to form a functional instrument. In addition to concept development, a variety of fabrication techniques were investigated to better understand the challenges that arise when designing and fabricating devices at the 3 mm scale. To augment existing techniques, a novel fabrication technique was developed which uses layers of lithographically patterned carbon nanotube (CNT) composite material to form a 3D part. This method was used to prototype some of the designs at a 1:1 size scale.

Thesis (Honors)--Ohio State University, 2005.
Title from first page of PDF file. Document formattted into pages: contains iv, 31 p.; also includes graphics. Includes bibliographical references (p. 30-31). Available online via Ohio State University's Knowledge Bank.

Höft- och knäprotesoperationer är idag en vanlig operation vid artros i höft- och knäled. Trotsminutiösa infektionsförebyggande förberedelser inför operationen drabbas ändå en delpatienter av postoperativa infektioner. Vid ortopedisk proteskirurgi är postoperativainfektioner ett direkt hot mot den nya inopererade leden och kan leda till långabehandlingstider som påverkar patientens livskvalitet under lång tid. Syftet med studien var att utforska patienters möjlighet till delaktighet i tidig upptäckt avpostoperativ infektion utifrån given information vid operation för höft- eller knäprotes. Semi-strukturerade intervjuer genomfördes med tio patienter med diagnostiserad postoperativinfektion efter höft- eller knäprotesoperation. Transkriberade intervjuer analyserades medinnehållsanalys. Journaler granskades för att beskriva patientens tidigare sjukdomar. Resultatet visade att första tecknen på infektion kan beskrivas med temat: Vad är normalt ochvad är inte normalt. Två kategorier beskriver patienternas Möjlighet till delaktighet ochHinder till delaktighet i det infektionsförebyggande arbete före, under och efter operation. Det handlade om hur patienten hade förstått eller inte förstått given information, vilketkategoriserades som subkategorier. Personcentrerad vård kan vara ett redskap för att stärka patienternas förutsättningar tilldelaktighet och ökar möjligheterna för att förhindra att vårdskador så som postoperativainfektioner uppstår.
Surgery with prosthetic joint replacement of the hip and knee in patients with osteoarthritis is a common procedure. Despite meticulous preparation prior to surgery, surgical site infections develop in some patients. A surgical site infection is a direct threat to the new implanted joint and can lead to long treatments that affect quality of life over time. The aim of this study was to explore patients´ participation in early detection of a surgical site infection based on the information given in conjunction to surgery for hip and knee replacement. Semi structured interviews were conducted with ten patients diagnosed with surgical site infection after hip or knee replacement surgery. Transcribed interviews were analyzed using content analysis. Medical records were reviewed to describe the patients´ comorbidity. The result showed that the first signs of infection can be described with the theme; What is normal and what is not normal? Two categories describe patients´ Possibility of participation and Barriers to participation in infection prevention before and after surgery. It was all about How the patient had understood or not understood the given information which was categorized as subcategories. Person-centered care can be a tool that enables patients´ possibilities to participate in their care and increases the possibilities to prevent adverse events such as surgical site infections.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 18).
Heat build-up in prosthetic sockets is a significant problem experienced by many amputees in America, with no central solution in sight. Heat and discomfort accounts for over 70% of problems experienced by lower limb amputees in America. Although there have been advances in prosthetics in the active-power knees and ankles, not even cybernetics can improve the comfort of the prosthesis if there is still a socket. The materials in prosthetic sockets are not conductive enough to relieve the heat inside of the socket. The purpose of this study is to model the temperature variance and heat transfer of an amputee's residual limb and design ways to improve current prosthetic socket technologies. With the addition of small holes, or perforations, in the socket, there will be an increase in the heat transfer by convection, while still maintaining the strength of a carbon fiber prosthesis. Through the use of discrete approximation modeling, the transient temperature inside of the socket layers can be identified and improved through design patterns cut into the socket. Increased heat transfer can be observed as the perforations in the socket become larger, although the larger the holes, the larger the stresses are in the prosthesis. Non-intrusive designs were developed for sockets before and after they are made to increase convection surface area. More modeling needs to be done in 3-dimensional polar coordinates.
by Luis Carbajal.
S.B.

Thesis: Ph. D., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 74-77).
For people living with limb amputation, the prosthetic socket - the interface between the residuum and prosthesis - is the most critical component. When a socket is uncomfortable, especially due to poor fit, the quality of life for a patient is greatly hindered. However, conventional design of sockets is largely artisan, with limited input of quantitative data. Current computer-aided and manufacturing (CAD/CAM) designs are still not clinically applicable solutions. Due to model identification procedures that employ non patient-specific and incomplete data sets, today's finite element (FE) models of the residuum are not predictive, leading to suboptimal socket designs. As such, there exists a need for a comprehensive biomechanical model of the residuum for the quantitative design and computational evaluation of patient-specific prosthetic sockets. This thesis presents a combined experimental-numerical approach to evaluate and validate a transtibial residuum biomechanical model. The central hypothesis of the work is that a single biomechanical model can predict the large non-linear response at various sites on a residuum under load. To evaluate this hypothesis, a non-linear, two-tissue model was formulated where tissue geometries were defined using MRI data of the residuum. The non-linear viscoelastic material parameters of the model were identified through inverse FEA-based optimization using in-vivo indentation experimental data at four locations. Using optimized model tissue parameters, the mean percentage error (mean absolute error/ maximum experimental force) between the experimental and simulation force-time curves at 14 other locations across the evaluated transtibial residuum was 7 ± 3%. Using this same modeling methodology and a single set of material constants to describe the bulk soft tissue biomechanical response of seven distinct transtibial residual limb models, the average percentage error for indentations at multiple locations across all seven limbs was 7 ± 1%. From these predictive models of residuum limbs, one rigid novel socket and two multimaterial transtibial sockets were designed, fabricated and evaluated through an entirely quantitative, automated and repeatable methodology. In a preliminary clinical investigation, the novel sockets were shown to reduce peak contact pressures at the tibia and fibular head regions on the residuum by significant amounts during standing compared to a conventional socket interface designed and fabricated by a trained prosthetist.
by David Moinina Sengeh.
Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references.
The goal of this work is to design a low cost, high performance prosthetic foot in collaboration with Bhagwan Mahaveer Viklang Sahayata Samiti (BMVSS), in Jaipur, India. In order to be adopted, the foot must cost less than $10 USD, be mass-manufacturable, and meet or exceed the performance of the Jaipur Foot, BMVSS' current prosthetic foot. This thesis investigates different metrics that are used to design and evaluate prosthetic feet and presents an analysis and evaluation of a solid ankle, cantilever beam - type prosthetic foot. Methods of comparing prosthetic feet in industry and in academia are discussed using a review of literature. These comparisons can be categorized into mechanical, metabolic, subjective, and gait analysis comparisons. The mechanical parameters are the most useful for designing a new prosthetic foot, as they are readily translated into engineering design requirements; however, these are the furthest removed from the performance of the foot. On the other end of the spectrum are metabolic and subjective parameters, which are useful in evaluating prosthetic feet because the objectives of minimizing energy expenditure and earning user approval are clear. Somewhere between these is gait analysis. The literature review reveals that not enough information is available to bridge these categories, that is, there is no consensus on how any particular mechanical parameter affects the subjective ranking of a prosthetic foot. Two mechanical parameters emerge as necessary, but not sufficient: the rollover shape and the energy storage and return capacity of a prosthetic foot. A simple model of a solid ankle, cantilever beam - type prosthetic foot is analyzed in the context of these two parameters. By applying beam bending theory and published gait analysis data, it is found that an unconstrained cantilever beam maximizes energy storage and return, but does not replicate a physiological roll-over shape well regardless of bending stiffness. Finite element analysis is used to find the roll-over shape and energy storage capacity from the same model when a mechanical constraint is added to prevent over deflection. The results show that for very compliant beams, the roll-over shape is nearly identical to the physiological rollover shape, but the energy storage capacity is low. For stiff beams, the opposite is true. Thus there is a trade-off between roll-over shape and energy storage capacity for cantilever beam type feet that fit this model. Further information is required to determine the relative importance of each of these parameters before an optimal bending stiffness can be found. A proof-of-concept prototype was built according to this model and tested in India at BMVSS. It was found that another parameter - perception of stability, which is perhaps dependent on the rate of forward progression of the center of pressure is equally important as, if not more than, the other parameters investigated here. Perception of stability increased with bending stiffness. The prototype foot received mixed feedback and has potential to be further refined. However, the solid ankle model is inappropriate for persons living in India, as it does not allow enough true dorsiflexion to permit squatting, an important activity that is done many times a day in the target demographic. Future work will use a similar method to design and optimize a prosthetic foot with a rotational ankle joint to allow this motion.
by Kathryn M. Olesnavage.
S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 51-54).
An estimated 230,000 above-knee amputees are in need of prosthetic devices in India with a majority of them facing severe socio-economic constraints in their daily lives. However, only a few passive prosthetic knee devices in the market have been designed to enable normative gait and to meet the unique daily life needs of above-knee amputees in the developing world. This thesis builds upon a past study at MIT, which established optimal mechanical component coefficients in prosthetic knee function required for achieving able-bodied kinematics. A mechanism for the design of a fully passive, low-cost prosthetic knee device, which aims to facilitate able-bodied kinematics at a low metabolic cost is presented. The mechanism is implemented using an automatic early stance lock for stability, a linear spring for early stance flexionextension and a differential friction damping system for late stance and swing control. For preliminary validation of the knee mechanism two field trials were carried out on five above-knee amputees in India, which showed satisfactory performance of the early stance lock and enabled smooth stance to swing transition by timely initiation of late stance flexion.
by Venkata Narayana Murthy, Arelekatti.
S.M.

Includes abstract.
Includes bibliographical references.
Aortic valve replacement in humans may be needed due to pathology leading to valve stenosis and regurgitation. Replacement is by either mechanical or soft tissue prosthetic valves. Before new valves are medically approved and introduced into the market they are required to undergo rigorous testing to verify performance and product life expectancy. Performance testing is done in a hydrodynamic test apparatus and life expectancy verified in an accelerated test apparatus. The Cardiology Department at Tygerberg Hospital has proposed a project for the design and implementation of a prosthetic aortic valve test apparatus. This device is to be used primarily for fatigue, but also limited hydrodynamic, testing of prosthetic heart valves. The design of the test apparatus was based on the four-element Windkessel model of the arterial system. This simple lumped parameter electrical analogy of the arterial system takes aortic and arterial resistance, arterial compliance, and blood inertance into account to simulate total arterial impedance. This model was developed with physiological reference and thus the element parameters only hold for physiological simulation as the equation governing impedance is speed sensitive. The model was adapted to provide theoretidal, physiological loads from physiological speeds of 60BPM through to accelerated speeds up to 1OOOBPM through mathematical optimisation of the Windkessel.The test apparatus was designed and built taking into account the varying Windkessel parameters where possible. Both compliance and resistance could be varied within an acceptable range, inertance however, could not be varied due to the limitations of the project. The apparatus was controlled and pressures on either side of the valve monitored with a LabView® graphical user interface. The apparatus was able to mimic in vivo closely and satisfied the ISO requirements for valve testing up to speeds of 230BPM. Various modifications are proposed to both the Windkessel model and the physical apparatus to compensate for hydrodynamic effects at high testing speeds in improve performance, as well as increase the maximum testing speed.

A high powered 4 DOF prosthesis for transfemoral amputees is presented in this paper. The prosthesis utilizes series elastic actuators with high powered hobby grade helicopter motors capable of providing 2880~W of power each for knee and ankle pitch and ankle roll. In addition, a yaw motor with a planetary gearbox combination is used for yaw actuation providing up to 21~Nm of torque. The prosthesis was designed to accommodate a variety of activities including, but not limited to, walking, running, and stair climbing.
Master of Science
A high powered prosthesis for transfemoral amputees is presented in this paper. Four control mechanisms, three of which are in series with springs to reduce the total power requirement of the motors, are used on the prosthesis to provide power to all motions of the leg. The prosthesis is capable of providing powered motion for knee and ankle pitch, ankle roll, and ankle yaw, i.e. ankle rotation from side to side. The prosthesis was designed to handle a variety of activities including, but not limited to, walking, running, and stair climbing.

Nowadays surgery simulations are aiming to apply not just visual effects but forcefeedback as well. To carry out force feedback, haptic devices are utilized that are mostlycommercial products for general purposes. Some of the haptic device features are moreimportant than others in case of surgery simulator use. The precision of the output forcemagnitude is one such property. The specifications provided by haptic devicemanufacturers are lacking details on device characteristics, known to cause difficulties inplanning of accurate surgery simulations.This project shows the design of a testbed that is capable of measuring the precision ofoutput forces within the haptic devices’ workspace. With the testbed, a set ofmeasurements can be run on different haptic devices, giving as a result a betterknowledge of the utilized device. This knowledge aids the design of more precise andrealistic surgery simulations.

Currently there are nearly 2 million people living with limb loss in the United States [1]. Many of these individuals are either transtibial (below knee) or transfemoral (above knee) amputees and require an ankle-foot prosthesis for basic mobility. While there are an abundance of options available for individuals who require an ankle-foot prosthesis, these options fail to mimic an intact ankle when it comes to key evaluation criteria such as range of motion, push-off force, and roll over shape. The roll over shape is created by plotting the center of pressure during a step in a shank-based coordinate system. To address the need for a prosthesis that effectively replaces the ankle's contribution to an able-bodied gait, a biomimetic approach is taken in the design the Compliant & Articulating Prosthetic Ankle (CAPA) foot. The passive CAPA foot consists of four components connected by torsion springs representing the Phalanges, Metatarsal bones, Talus, and Calcaneus. Biomimetic functionality is exhibited by CAPA foot with regards to the roll over shape and a linear relationship between moment exerted and ankle angle, distinguishing the CAPA foot from other ankle-foot prostheses. A mathematical model of the CAPA foot is created to determine the roll over shape a specific CAPA foot geometry would produce and support eventual customization of the 3D printed components. The mathematical model is used to optimize the design to two distinctly different roll over shapes, one with a rocker radius closer to that of the Talus bone and the other closer to the energetically advantageous value of 0.3 times leg length [2, 3]. Compliant and stiff versions of the two CAPA feet were compared to a conventional Solid Articulating Cushioned Heel (SACH) foot and a passive dynamic response foot (Renegade® AT produced by Freedom Innovations). Ten able bodied subjects walked on the Computer Assisted Rehabilitation Environment normally, and then with a transfemoral prosthetic simulator. The study was separated into two experiments. For the second experiment (subjects 6-10), the versions of the CAPA foot had pretension in the dorsiflexion springs. Overall the ankle angles and sagittal plane ground reaction forces of the CAPA foot better mimicked an intact ankle-foot than the existing passive ankle-foot prostheses. Added pretension increased the sagittal plane ground reaction forces and roll over shape radius of curvature and arc length. Nine out of ten participants preferred the CAPA foot and there was a statistical significant difference (F=14.2, p<0.01) between the difficulty level rating given for trials with the CAPA foot versus the existing ankle-foot prostheses. The mathematical model is found to be capable of accurately predicting experimental roll over shape trends and the concept of roll over shape based design is demonstrated. Successful aspects of the CAPA foot can be applied to other ankle-foot prosthesis. The CAPA foot could provide a passive, cheap, and personalizable ankle-foot prosthesis that improves mobility the quality of life for individual’s lacking an intact ankle.