Academic literature on the topic 'Lower Limb Prosthesis'

A study has been made of data on 19,421 prosthetic limbs prescribed for 12,143 Australians under the Free Limb Scheme in the years 1981–1985. These prostheses consisted of 18,119 legs and 1,302 arms. The mean age of the lower limb prosthesis user was 52.8 and the upper limb prosthesis user 31.3 years. Males outnumbered females by 3 to 1 in the upper limb prosthesis users, and 2.8 to 1 with lower limb prosthesis users. Below-knee prostheses, patellar-tendon-bearing and thigh-lacing prostheses, made up 58.7% of all prostheses prescribed in the time span. Below-elbow prostheses were the commonest upper limb prostheses with children being the most frequent users. Comparisons with other studies of large number of prosthesis users show an older mean age in Australia and more below-knee prosthesis users than in American studies.

With the rapid development of computer science and technology in our country, especially the advent of the 5G network era, the emergence of smart prostheses makes it possible for disabled, injured, or amputee people with lower limbs to walk and exercise like normal people. However, due to the different selection of prosthetic materials, the final lower limb prostheses produced will also have different performance differences. How to select prosthetic materials to optimize the performance of the intelligent lower limb prosthesis is the focus of extensive discussion in the medical community. For this reason, this article takes the research of the adaptive control system of intelligent lower limb prosthesis based on 5G virtual reality as the research object. By using the current advanced 5G communication technology and virtual reality technology, a high-performance intelligent lower limb prosthesis is produced. Provide assistance with basic walking and motor abilities in daily life of patients with lower limb disabilities. This article first gives a systematic theoretical introduction to 5G virtual reality technology, expounds the current status of patients with lower limb disabilities, and proposes to use intelligent lower limb prosthetics to replace healthy lower limbs to solve the basic walking and sports needs of disabled patients in daily life and then use 5G virtual reality technology. The selection of human knee joints and ankle joints and structural system design were carried out. Finally, it was decided to use the four-bar linkage structure as the knee joint structure of the three-dimensional modeling of the intelligent lower limb prosthesis. At the end of this article, the application and simulation of the intelligent lower limb prosthesis to the human body were also carried out. The results of the experiment found that after 45 weeks of wearing exercises, the gait of the intelligent lower limb prosthesis is consistent with the expected effect whether it is walking on level ground and up and down the stairs or uphill. Due to the strong adaptiveness of the intelligent lower limb prosthesis sexual control, it can well assist the basic life movement ability of patients with lower limb disabilities.

The provision and maintenance of prostheses in 100 trans-femoral amputees and 73 trans-tibial amputees were retrospectively analysed over a 10-year period. The aim of the study was to analyse the prosthetic episodes, i.e., the need for maintenance, repairs and replacements to a trans-femoral and a trans-tibial prosthesis and frequency of new sockets prescribed over the same period of use by established adult amputees. The study showed that the trans-femoral amputees needed 0.96 new prostheses, 3.27 new sockets, 2.31 major repairs, 3.36 component changes and 21.85 minor repairs. Younger trans-femoral amputees aged less than 60 years needed 1.1 new prostheses, 3.15 new sockets, 2.06 major repairs, 4.23 component changes and 20.49 minor repairs. Younger trans-femoral amputees needed significantly more changes of prosthetic components ( p = 0.04). The associated study on 73 trans-tibial amputees showed that they needed 1.4 new prosthesis, 2.9 new sockets, 3.2 major repairs and 14.1 minor repairs over the same 10-year period. The introduction and prescription of modular prosthesis as opposed to conventional limbs used earlier has possibly allowed components to be easily replaced thus reducing the need to replace a whole new prosthesis.

Background: One of the main indicators of the suspension system efficiency in lower limb prostheses is vertical displacement or pistoning within the socket. Decreasing pistoning and introducing an effective system for evaluating pistoning could contribute to the amputees’ rehabilitation process.Objectives: The main objective of this study was to review existing research studies that examine the occurrence of pistoning in lower limb prosthesis with different techniques in static (standing) and dynamic (walking and jumping) positions.Study Design: Literature review.Methods: Keywords related to slippage, suspension, pistoning and vertical movement in lower limb prosthetics were used to search the literature available in PubMed, ScienceDirect, Web of Science and Google Scholar databases. Sixteen articles were selected for further analysis according to the selection criteria.Results: The following methods have been used to measure the occurrence of pistoning in prosthetic limbs: radiological methods, photographic technique, motion analysis system, sensor and spiral computerized tomography (CT). Pistoning was measured both in standing and walking.Conclusions: The results of this review reveal that further research is needed to develop and evaluate easy, accurate and safe methods of measuring pistoning. Future studies should provide a gold standard for the acceptable range of pistoning in a prosthetic socket.Clinical relevanceThis literature review contributes to a further understanding of lower limb prosthetic biomechanics by highlighting the strengths and weaknesses of the techniques that are currently available for evaluating the occurrence of pistoning in a prosthetic socket. It provides a useful overview of the current methods of measuring residual limb movements relative to the socket and liner, and will be of use for both practitioners and researchers in prosthetics and orthotics fields.

Background: Many persons with upper limb amputation reject prostheses, and many are not satisfied with their devices. Research is needed to understand modifiable factors related to device satisfaction. Myoelectric devices with multiple degrees of freedom are now available; however, no studies have examined whether they lead to greater device satisfaction. Prosthetic training contributes to more skillful prosthesis use and greater likelihood of long-term use; however, the relationship between training and device satisfaction is unclear. Objectives: (1) To describe and compare satisfaction by prosthesis and terminal device type and (2) to identify factors associated with satisfaction. Study design: Cross-sectional study. Methods: Participants were 449 persons with unilateral upper limb amputation who used a prosthesis. Participants described their prostheses, prosthetic training, device repairs, visits to a prosthetist, and rated device satisfaction using two standardized measures (Trinity Amputation and Prosthesis Experience Scales Satisfaction scale and Orthotics and Prosthetics Users’ Survey - Client Satisfaction with Devices scale). Multivariate generalized linear regression models examined the relationship between prosthesis and terminal device type and satisfaction, controlling for covariates that were meaningful in bivariate analyses. Results: There were no differences in satisfaction by prosthesis type or terminal device degrees of freedom. Satisfaction was associated with receipt of training to use the initial prosthesis, amputation level, age, and race. Conclusion: No differences in satisfaction by device or terminal device type were observed. Worse satisfaction was associated with more proximal amputation level, younger age, and black race. The association between receipt of initial prosthetic training and device satisfaction points to the critical role of occupational or physical therapy in the early stages of prosthetic care. Clinical relevance Prosthetic satisfaction did not vary by device or terminal device degrees of freedom. Proximal amputation level, younger age, and black race were associated with lower prosthetic satisfaction. Receipt of initial prosthetic training was associated with greater device satisfaction, pointing to the critical role and lasting impact of early training.

Amputation of a limb is always perceived as a catastrophe. The principles underlying creation of a stump adapted to modern prosthetic fittings must be fully understood and the patient managed by a multidisciplinary team. In paediatric patients, managing the prosthetic limb length is a crucial point that should be maintained according to the expected growth potential of the child. The main problem with child amputee is the heel height and adjustment of height of prosthesis during change of foot wears and bare foot walking. Children with congenital amputation and congenital anomalies need special attention for the prosthetic fitment. As children are in the growing age, the prosthetic device is required to be changed frequently. The major constraint in frequent change of prosthetic device in developing country is lack of special prosthetic kit, paediatric prosthetics components, skilled prosthetists and low-income group of amputees. To face this challenge, we have designed and developed a new adjustable prosthetic pylon for lower limb prosthesis. Key words: Prosthesis, Component development, Prosthesis, congenital anomaly, Adjustable pylon.

In the present study the psychophysical detection threshold levels for mechanical stimulation of 32 prosthetic limbs were determined. Prosthetic limbs were anchored to the bone by means of an implant (n=17) or supported by a socket enclosing the amputation stump (n=15). Detection threshold levels were assessed for pressure and vibratory stimulation of the prosthesis and the limb at the contralateral side (control). Following vibratory stimulation, thresholds were increased on an avarage 20% for socket prostheses, but approached those of the control for boneanchored prostheses. For pressure stimulation, thresholds were increased up to 60% for socket prostheses and 40% for boneanchored prostheses compared to the control. While boneanchored prostheses yielded significantly lower threshold levels than socket prostheses, there was no significant difference between both treatments regarding pressure stimulation. Results were applicable to both upper and lower limb amputees. It could be concluded that detection thresholds for pressure and especially vibratory stimulation of prosthetic limbs were generally higher than for control limbs. The outcome was related to the prosthetic limb design with boneanchored prostheses yielding better perception than socket prostheses.

Aim. To study the physical activity in disabled patients who underwent an amputation of the lower limb in a late period of rehabilitation and prosthetics. Methods. The study included patients with structural and functional disorders of limbs. 308 patients aged 18 to 66 years were randomly selected to participate in the study as they were referred to Prosthetic and orthopedics center «Reabilitaciya invalidov», Kazan, Russia from 2008 to 2010. Patients were allocated to five age groups: 19 to 29 years, 30 to 39 years, 40 to 49 years, 50 to 59 years old and older than 60 years. Activity level, depending on the motor capacity was investigated in 308 patients who were offered prosthetics according to the classification subdividing locomotor activity on five levels. SF-36 questionnaire (quality of life), Spielberger-Hanin reactive and personal anxiety scales, Beck Depression Inventory, the Mehrabian Achieving Tendency Scale, Smisek-Leonhard characterological test were administered. Quality of lower limbs prostheses were assessed by «TWO LEGS» prosthesis evaluation questionnaire on a 5-point scale. Results. The majority of patients who were at the remote stage of rehabilitation after prosthesis had high level of physical activity - 141 (45.7%) patients, average activity level - 81 (26.2%) patients, reduced level of activity - 63 (20.5%) patients. High level of physical activity, depending on the locomotor activity, was more typical for the second (20-29) and third (30-39 years) age groups - 60 and 54%, respectively. Very high and high levels of physical activity was equally observed in patients with one and both amputated both lower legs: 8.4 and 7%, respectively. Conclusion. Level of amputation, age and psychological characteristics, as well as prosthesis quality and the term of prosthesis use were essential for motor activity, quality of life and functional independence of the disabled with structural and functional of the lower limb disorders.

The objectives of this project were to ascertain whether, to date, the views concerning the determination of prosthetic candidacy have been optimal and whether the training methods applied have been effective and have resulted in constant use of the prosthesis after conclusion of the training programme. Secondly it was intended to set up guidelines for future budgeting as well as providing a reference framework for the process of rehabilitation. An inquiry based on questionnaires was the first phase in a quality assurance project carried out among 29 amputees trained in 1990 and 1991. The result of the inquiry was that rehabilitation using PTB prostheses for 19 trans-tibial amputations in 18 cases (one patient was a bilateral trans-tibial amputee) led to constant use of the prosthesis and that advanced age was no hindrance to constant use in this group. For 10 trans-femoral amputees the inquiry revealed that advanced age combined with problems of donning the prosthesis was a hindrance to constant use in two cases. It is concluded that there is a need for testing/developing new types of femoral prostheses. The patients' evaluation of the rehabilitation process and their prostheses stresses the need for communication between the team of professionals and the patients in the decision process concerning the provision of a prosthesis as well as the provision of complete information on the patients' future functional possibilities. Qualitative measurements must include the kind and number of medical complications and the social conditions of the amputee as well as tests of physical and mental resources.

Amputation is a surgical operation in which a portion of the body is removed such as an arm, foot, leg, hand or finger. Amputation can be performed on any portion of the body, from a tiny area to a big area. Two types of prosthesis limb are used after amputation upper limb prostheses and lower limb prostheses. After amputation, most people use prostheses to carry out their daily activities. This research explains how people use prostheses after amputation and what difficulties people have to go through after using the prostheses. Social, economic and psychological aspects also discussed in this research. The objective of this research is to explore the problems and challenges in income climate and personal characteristics. To find out the health care with prosthetic technology, rehabilitation and satisfaction with prostheses and to investigate the established need and resources for prosthesis limb usage also focused in this research. The universe for the following study was all the prosthetic limb amputees in Multan District. All the prosthetic limb amputees were the population of the study. 15 cases were selected to investigate the study. Non probability purposive sampling technique was used. To measure the socio economic problems faced by prosthetic limb amputees, researcher used the interview guide. As a result questions were asked from the respondents during face to face meeting. In all cases, most of the amputations are due to accidents, diabetes, gunshot and amputation of any part of the body in machinery while working in factories. Most people have lower limb amputation including above or below knee amputation. In mostly cases people of lower limb amputations have severe disability. People with amputation have to go through a lot of troubles and sufferings after having their limbs amputated and having their prostheses implanted. The lives of such people are going through troubles and physical pain. Due to which such people are suffering from a lot of mental stress. The government should provide free prostheses to these disabled people and also help them so that they can meet their needs.

In Germany alone, 10,000 to 12,000 transfemoral amputations occur every year. Persistent rehabilitation efforts and advanced medical devices like prosthetic knee joints are crucial to reintegrating amputees into daily life successfully. Modern knee joints represent a highly integrated mechatronic system including special kinematics, a lightweight design, various sensors, microprocessors and complex algorithms to control a damping system in the context of the given situation. A knee joint is a passive system and normally has no actuator for an active movement. To enable a natural gait pattern, dampers decelerate the swinging speed of the prosthesis depending on the walking speed and situation. The invention of a novel knee joint called VarioKnie provides two kinematics - a monocentric and a polycentric one. Both kinematics have diametrical advantages and the user can choose the preferred setting through an electromechanical switching unit. With this knee joint in mind, a special hydraulic damper is developed to support both kinematics. Requirements and technical data are provided in the present paper. State of art are microprocessor-controlled knee joints with only one kinematic and either a hydraulic, a pneumatic, or a rheological damper.

The introduction of computer-aided tools into the product development process allows improving the quality of the product, evaluating different variants of the same product in a faster way and reducing time and costs. They can play a meaningful role also in designing custom-fit products (especially, those characterized by a tight interaction with the human body), increasing the comfort and improving people’s quality of life. This thesis concerns a specific custom-fit product, the lower limb prosthesis. It is part of a research project that aims at developing a new design platform centred on the digital model of the patient and his/her characteristics. The platform, named Prosthesis Virtual Laboratory (PVL), is being developed by the V&K Research Group (University of Bergamo) and integrates ICT tools and product-process knowledge. It provides two environments: one for prosthesis design (named Prosthesis Modelling Lab), both transfemoral and transtibial, and one for the prosthesis testing (named Virtual Testing Lab). The main objective has been to embed within the Virtual Testing Environment numerical simulation tools to analyse the interaction between the socket and the residual limb under different loading conditions, allowing the prosthetist to automatically run the simulation and optimize socket shape. Simulation tools, such as Finite Element Analysis (FEA), permit to predict the pressures at the interface socket-residual limb, evaluate the comfort of socket and validate the socket design before manufacturing phase. However, the diffusion of simulation tools in orthopaedic laboratories is strongly limited by the high level of competence required to use them. Furthermore, the implementation of the simulation model is time consuming and requires expensive resources, both humans and technological, especially onerous for small orthopaedic labs. To effectively employ the numerical analysis in prosthesis design, the simulation process has been automated and embedded within the virtual design platform. Therefore, in such a context, the specific scientific objectives have been to: • Critically analyse the state of the art with regard to methods and tools to evaluate socket-residual limb interaction. • Identify the key issues to automate the simulation activities. • Define a set of simulation rules and the Finite Element Analysis model. • Implement and integrate within the new design platform the automatic simulation procedure. • Test the integrated design platform with a case study. • Identify future development trends. Research activities have been organized into four main activities as follows. The first activity consisted in an extensive analysis of the last two decades State of the Art on numerical models adopted to study residual lower-limb and prosthetic socket interaction. Starting from literature, the key issues of the simulation process (e.g., geometric models reconstruction, materials characterization, simulation steps, and boundary conditions), the methodologies and procedures have been identified. Particular attention has been also paid to the parameters commonly adopted to evaluate socket comfort. This phase played a fundamental role since it constituted the basis for the implementation of the embedded simulation procedure. It also permitted to highlight that current finite element models are stand-alone and not integrated with prosthetic CAD or Digital Human Modelling (DHM) systems. In the second activity the tools and methods necessary to develop the embedded simulation module have been selected. By using these tools, it was possible to identify the simulation rules and the best practice procedures, which are fundamental to implement an automatic simulation module. Initially, the modelling tools have been considered since they provide the geometric models for the numerical analysis of the socket-residuum interaction and for the virtual gait analysis of the patient’s avatar. Then, particular attention has been paid on the choice of the FE solver, that has been made according to the results of preliminary FE models. They were implemented using two different solvers: Abaqus (commercial) and CalculiX (open-source). The latter has been experimented to verify the possibility to develop a design platform totally independent from commercial tools. However, according to the results, Abaqus has been chosen because it allows managing adequately simulation problems characterized by large deformations and difficult contact conditions, its results are comparable with those found in literature, and its scripting code does not require specific customization. The last considered tool was the Digital Human Modelling system (LifeMOD) since it permits to enhance the accuracy of the numerical analysis. By performing the gait simulation of the patient’s avatar, it provides the directions and the magnitude of forces and moments that act on the socket. The third activity consisted in defining the architecture of the simulation module, implementing the module and the interfaces with the socket CAD tool (namely Socket Modelling Assistant-SMA) to get the geometric models of the involved parts (socket and residual limb) and with the DHM system to acquire forces acting on the socket during patient’s walking. The simulation module has been implemented using the Python language and the integrated environment works as follows. Once the prosthetist has created the 3D socket model, SMA acquires the input for the analysis (e.g., residual limb length, patient’s weight, friction coefficient, material properties), and produces the files required to generate the FE model. Abaqus automatically generates the FE model without any human intervention, solves the analysis and generates the output file containing the pressure values. Results are imported in SMA and visualized with a colour map. SMA evaluates pressure distribution and highlights the areas that should be modified. Geometry modifications are needed in the areas where pressure exceeds the maximum value and are carried out automatically by the system or by the prosthetist using the virtual tools available in SMA. Then, the system re-executes the simulation. Through this iterative process of adjustments, the socket shape is modified and optimized in order to eliminate undercuts, minimize weight and, especially, distribute loads in the appropriate way so that they can be tolerated for the longest period of time. The fourth and last activity concerned the test and validation of the simulation module integrated within the new design platform, by considering a transfemoral patient. The new virtual process and the key issues of the simulation procedure have been tested starting from the patient’s data acquisition to the release of the socket using also data coming from the gait simulation with the DHM system. The geometric model of the residual limb has been reconstructed from MRI images and the socket has been modelled using SMA. Through an iterative process, the socket shape has been optimized until the pressure distribution on the residuum was consistent. Preliminary activity concerning the FE model validation has been performed comparing the pressure distribution experimentally acquired with pressure transducers over the residuum with the simulation results. To accomplish this task, the geometric model of the real socket has been acquired using reverse engineering techniques. Two numerical simulations have been implemented, they differ for the residuum geometric models adopted: from MRI and from 3D scanning. Preliminary results have been considered positive but improvements are necessary. As an example, some geometric inconsistencies, occurred during the acquisition of the geometric model of the residual limb, have reduced the accuracy of the final results. To complete the evaluation of the simulation model, a new residuum geometric model is needed and a refinement of the material model characterization is desirable. To conclude, the simulation module embedded within Virtual Testing Laboratory has improved the prosthesis development process with the goal of assessing and validating the socket shape under different load conditions (static or dynamic) before the manufacturing phase. The testing phase of the new procedure has demonstrated the feasibility of the virtual approach for lower limb prosthesis design. The tests carried out permitted to highlight necessary improvements and future developments, such as the definition of a protocol to acquire the residual limb through MRI and 3D scan, refinement of the FE model (e.g., non-linear viscoelastic behaviour for soft tissues, friction coefficients), parallel computing to improve simulation performances, open-source solvers to implement a design platform totally independent from commercial systems, and a massive test campaign involving transtibial and transfemoral patients to fully validate the FE model and the design platform.
L’introduzione di strumenti informatizzati nel processo di sviluppo del prodotto permette di migliorarne la qualità, nonché di valutare diverse varianti del prodotto stesso in modo più veloce, riducendo in tal modo il tempo ed i costi relativi alla progettazione. Per queste motivazioni, tali strumenti possono giocare un ruolo rilevante anche nella realizzazione di prodotti personalizzati (specialmente quelli caratterizzati da una stretta interazione con il corpo umano), aumentandone il comfort e migliorando la qualità di vita delle persone. Il presente lavoro di tesi si concentra nello specifico sull’applicazione di tali strumenti informatizzati nella creazione di protesi per arti inferiori, inserendosi in un progetto di ricerca che ha come obiettivo quello di sviluppare una nuova piattaforma di progettazione centrata sul modello digitale del paziente e sulle sue caratteristiche. La piattaforma, chiamata Prosthesis Virtual Laboratory (PVL), è stata sviluppata dal gruppo di ricerca V&K dell’Università degli Studi di Bergamo nell’ottica di integrare gli strumenti informatici con la conoscenza del prodotto e del processo. La piattaforma è strutturata in modo da offrire due ambienti di lavoro: uno dedicato alla progettazione della protesi (chiamato Prosthesis Modelling Lab), sia transfemorale che transtibiale, e l’altro destinato alla fase di verifica della stessa (chiamato Virtual Testing Lab). L’obiettivo principale del lavoro di tesi è stato quello di integrare, all’interno dell’ambiente virtuale di verifica, gli strumenti di simulazione numerica che consentono di analizzare l’interazione tra l’invaso e l’arto residuo sotto diverse condizioni di carico, permettendo al tecnico protesico di effettuare la simulazione in automatico e di ottimizzare la forma dell’invaso. Gli strumenti di simulazione, come l’analisi agli elementi finiti (FEA), permettono di predire la pressione all’interfaccia tra invaso e moncone, di valutare il comfort dell’invaso e di validare la progettazione dello stesso prima della fase di manifattura. Tuttavia, la diffusione degli strumenti di simulazione nei laboratori ortopedici è fortemente limitata dall’elevato livello di competenze richieste per ottenere risultati significativi. Inoltre, l’implementazione di un modello di simulazione numerica richiede tempo e costose risorse, sia umane che tecnologiche, particolarmente onerose per i piccoli laboratori ortopedici. Affinché l’analisi numerica sia utilizzata nella progettazione delle protesi, è necessario che il processo di simulazione sia automatico ed integrato all’interno di una piattaforma virtuale di progettazione. In questo contesto, gli obiettivi scientifici specifici sono stati: • Analizzare criticamente lo stato dell'arte riguardante i metodi e gli strumenti per valutare l'interazione tra invaso ed arto residuo. • Identificare le questioni chiave per automatizzare le attività di simulazione. • Definire un insieme di regole di simulazione ed il modello per l’analisi ad elementi finiti. • Implementare ed integrare nella nuova piattaforma di progettazione la procedura di simulazione automatica. • Verificare la piattaforma di progettazione integrata con un caso studio. • Identificare le tendenze di sviluppo futuro. Le attività di ricerca sono state organizzate in quattro attività principali, come di seguito presentato nello specifico. La prima attività è consistita in un'analisi approfondita dello stato dell’arte negli ultimi due decenni relativamente ai modelli numerici adottati per studiare l’interazione tra invaso ed arto residuo. Partendo dalla letteratura, sono stati individuati i temi chiave del processo di simulazione (ad esempio la ricostruzione dei modelli geometrici, la caratterizzazione dei materiali, le fasi di simulazione e le condizioni al contorno), nonché le metodologie e le procedure di simulazione. Particolare attenzione è stata posta anche ai parametri comunemente adottati per valutare il comfort dell’invaso. Questa fase ha giocato un ruolo fondamentale in quanto costituisce la base per l’implementazione della procedura di simulazione integrata. Ha permesso altresì di evidenziare come gli attuali modelli agli elementi finiti siano indipendenti e non integrati con i sistemi CAD per protesi o di Digital Human Modelling (DHM). La seconda attività ha avuto come focus la selezione degli strumenti e dei metodi necessari allo sviluppo del modulo di simulazione, per mezzo dei quali è stato possibile identificare le regole di simulazione e le procedure di buona prassi, fondamentali per l’implementazione di un modulo di simulazione automatica. Inizialmente, gli strumenti di modellazione sono stati presi in considerazione in quanto forniscono i modelli geometrici sia per l’analisi numerica dell’interazione tra invaso ed arto residuo che per l’analisi della camminata virtuale dell’avatar del paziente. In seguito, particolare attenzione è stata posta sulla scelta del solutore a elementi finiti, che è stata fatta in accordo con i risultati ottenuti dai modelli preliminari implementati utilizzando due diversi solutori: Abaqus (commerciale) e CalculiX (open-souce). Quest’ultimo è stato impiegato per verificare la possibilità di sviluppare una piattaforma di progettazione totalmente indipendente dagli strumenti commerciali. Tuttavia, in base ai risultati ottenuti, la scelta si è indirizzata verso Abaqus, in quanto permette di gestire in modo adeguato i problemi di simulazione caratterizzati da grandi deformazioni e da difficili condizioni di contatto. L’utilizzo di questo solutore consente di ottenere risultati paragonabili a quelli presenti in letteratura ed inoltre il suo codice di script non richiede specifiche personalizzazioni. L’ultimo strumento utilizzato è stato il sistema DHM (Digital Human Modelling ) che permette di aumentare la precisione dell’analisi numerica. Attraverso l’analisi della camminata virtuale dell’avatar del paziente, questo strumento è in grado di fornire le direzioni e le intensità delle forze e delle coppie che agiscono sull’invaso. La terza attività ha riguardato la definizione dell’architettura del modulo di simulazione, l’implementazione del modulo stesso e del suo interfacciamento prima con lo strumento CAD per l’invaso (chiamato Socket Modelling Assistant - SMA), allo scopo di ottenere i modelli geometrici delle parti coinvolte (invaso ed arto residuo), ed in seguito con il sistema DHM, per acquisire le forze che agiscono sull’invaso durante la deambulazione del paziente. Il modulo di simulazione è stato implementato utilizzando il linguaggio Python e l’ambiente integrato prevede diverse fasi di sviluppo, come di seguito approfondito. Una volta che il tecnico protesico ha creato il modello 3D dell’invaso, lo SMA acquisisce gli input per l’analisi (come la lunghezza dell’arto residuo, il peso del paziente, il coefficiente di attrito, le proprietà dei materiali) e rilascia i file richiesti per generare il modello agli elementi finiti. Abaqus genera automaticamente il modello di simulazione senza che vi sia alcun intervento umano, risolve l’analisi e genera il file di output contenente i valori di pressione. I risultati sono importati nello SMA e visualizzati con una mappa di colore. La modifica della geometria dell’invaso, necessaria nelle aree in cui la pressione eccede i valori massimi, è eseguita in automatico dal sistema o dal tecnico protesico tramite gli strumenti virtuali presenti nello SMA. Il sistema, quindi, riesegue la simulazione. Attraverso questo processo iterativo di rettifica, la forma dell’invaso è modificata ed ottimizzata al fine di eliminare i sottosquadri, minimizzare il peso e soprattutto distribuire i carichi in modo appropriato, così che siano tollerabili per lunghi periodi di tempo. La quarta ed ultima attività ha riguardato la sperimentazione e la validazione del modulo di simulazione integrato all’interno della nuova piattaforma di progettazione considerando un paziente transfemorale. Il nuovo processo virtuale e le questioni chiave della procedura di simulazione sono state testate partendo dall’acquisizione dei dati del paziente fino al rilascio dell’invaso definitivo, utilizzando anche i dati provenenti dalla simulazione della camminata con il sistema DHM. Il modello geometrico dell’arto residuo è stato ricostruito partendo dalle immagini MRI e l’invaso è stato modellato utilizzando lo SMA. Attraverso un processo iterativo, la forma dell’invaso è stata ottimizzata fino ad avere una distribuzione appropriata della pressione sul moncone. L’attività preliminare riguardante la validazione del modello agli elementi finiti è stata eseguita comparando la distribuzione delle pressioni acquisite sperimentalmente sul moncone con i risultati della simulazione. Per realizzare questo compito, il modello geometrico dell’invaso reale è stato acquisito utilizzando tecniche di reverse engineering. Sono state implementate due diverse simulazioni numeriche che differiscono per il modello geometrico del moncone adottato: attraverso MRI nel primo caso, da scansione 3D nel secondo. I risultati preliminari possono considerarsi positivi ma ulteriori sviluppi sono necessari. Ad esempio, alcune incongruenze geometriche che si sono verificate durante l’acquisizione del modello geometrico hanno ridotto la precisione dei risultati finali. Per completare la valutazione del modello di simulazione è quindi necessario utilizzare un nuovo modello geometrico del moncone e sarebbe anche auspicabile raffinare il modello di caratterizzazione del materiale. Concludendo, il modulo di simulazione integrato all’interno del Virtual Testing Laboratory – VTL ha permesso di migliorare il processo di sviluppo della protesi con l’obiettivo di valutare e validare la forma dell’invaso sotto diverse condizioni di carico (statiche o dinamiche), prima della fase di manifattura. La fase di test del nuovo processo ha inoltre dimostrato la fattibilità del nuovo approccio virtuale per la progettazione delle protesi per arti inferiori. I test effettuati hanno indicato quali miglioramenti siano necessari ed i possibili sviluppi futuri, tra cui: la definizione di un protocollo di acquisizione dell’arto residuo attraverso MRI o scansione 3D, il calcolo parallelo per migliorare le prestazioni della simulazione, l’utilizzo di solutori open-source per implementare una piattaforma di progettazione totalmente indipendente dai sistemi commerciali, la realizzazione di una massiccia campagna sperimentale che coinvolga pazienti transtibiali e transfemorali al fine di convalidare pienamente il modello FE e la piattaforma di progettazione.

Misalignment in the lower limb prosthesis can cause great discomfort in the stump- socket interface and disturbance to gait function. In the long run, it could deteriorate the musculoskeletal system. In practice, the assessment still depends heavily on the verbal feedback of an amputee and experiences of a prosthetist. Moreover it is inconsistent amongst the prosthetists. Prosthetic alignment involves the adjustment of the prosthetic components relative to the gait quality. Some methods were proposed, including symmetry index, variation in a step-to-step transition, stability within the zone of integrated balance, matching roll-over shape eROS) to an ideal ROS and etc. It is not clear if the optimum alignment could be achieved. These methods exhibit a few limitations, i.e. limited use of gait variables in a single comparison and non-uniform results when different gait variables are applied. There is a need to provide an objective assessment method that processes high dimensional gait variables and presents them in a simple form. In addition, it could be impractical and expensive clinically to spend excessive time on a patient. An ambulatory gait measurement system could achieve this objective to a certain extent. This research investigates a potential engineering solution that is able to provide an assistive and objective assessment of the lower limb prosthetic alignment that provides optimal gait quality. The effort includes a development of a low-cost ambulatory gait measurement system which could be reliably used during indoor and outdoor trials. Human walking trials using the designed ambulatory system are designed and performed to justify the proposed solution. A novel gait analysis method using Principle Component Analysis and Self-Organizing Feature Map is proposed to process high dimensional gait data into a simple plot and a decision guide. The proposed methodology could help to collect sufficient gait data during indoor and outdoor gaits and could provide an objective gait assessment during the application of lower limb prosthetic alignments.

Le socket prothétique (dit aussi emboiture prothétique), élément d'interface essentiel entre le moignon du patient et le dispositif prothétique, est le plus souvent le lieu où se définit le degré de réussite prothétique. C'est la partie la plus critique de la prothèse, personnalisée pour s'adapter au membre résiduel unique de l'amputé. Sans une forme et un ajustement approprié du socket, la prothèse devient inconfortable, voire inutilisable, et provoque des douleurs et des problèmes de peau. La production prothétique actuelle manque encore de normes numériques universelles pour concevoir un socket. La pratique actuelle est coûteuse et repose sur les raffinements manuels du technicien orthopédiste, et la qualité de l'ajustement est strictement corrélée à ses compétences ainsi qu'aux retours subjectifs du patient lors des phases d’essai de la prothèse fabriquée. La thèse vise à mener une analyse approfondie d'une conception optimale de l'emboîture prothétique en étudiant un processus alternatif de conception assistée par ordinateur. Ce processus est entièrement basé sur le modèle virtuel du membre résiduel du patient et repose sur le calcul de l’interaction emboîture-moignon. Un calcul rapide est favorable dans ce cas, c'est pourquoi nous proposons d'utiliser le système Mass-Spring (MSS) au lieu de la méthode FE largement utilisée pour modéliser les tissus mous du membre résiduel. Une nouvelle configuration du modèle MSS est proposée pour respecter la propriété de non compressibilité des tissus mous en ajoutant des « ressorts correctifs » non linéaires. Le modèle numérique doit être généré à partir du modèle scanné du moignon. À cette fin, nous proposons un schéma de fusion de quatre capteurs de profondeur à bas coût pour un scan rapide et économique avec des techniques de réduction des erreurs. Enfin, le membre résiduel virtuel est utilisé dans la phase de conception du socket. Une méthode de conception paramétrique est proposée et étudiée. Le problème de conception est transformé en problème de satisfaction des contraintes dérivées du calcul inverse de l'interaction socket-moignon. L'approche inverse a été choisie pour éliminer le besoin d'une formulation de contact coûteuse. Ce fait conduit à des calculs rapides, et par conséquent, permet de fournir des retours numériques en temps réel pendant le processus de conception. Le système a été implémenté pas programmation C++ avec une interface graphique où les retours numériques sont donnés sous forme d’une carte de radar. La validation a été faite en comparant les résultats de notre système avec la sortie des simulations FE. Le système a été implémenté avec une interface graphique conviviale et virtuellement testé et validé numériquement. Ce système réduit les limites des pratiques actuelles. Cependant, de nombreux travaux sont encore en cours pour affiner et développer le système et le valider par des expériences cliniques
The prosthetic socket, an essential interface element between the patient's stump and prosthetic device, is most often the place where the degree of prosthetic success is defined. It is the most critical part of the prosthesis, customized to fit with the unique residual limb of the amputee. Without a proper socket shape and fit, the prosthesis becomes uncomfortable, or even unusable, and causes pain and skin issues. The state-of-the-art prosthetic production is still missing universal numerical standards to design a socket. The current practice is expensive and relies on the manual refinements of the orthopedic technician, and the fit quality strictly correlates with his skills as well as the subjective feedback of the patient. The thesis aims to conduct a deep analysis of an optimal design of the prosthetic socket by studying and developing an alternative computer-aided design process. This process is fully based on the virtual model of the patient’s residual limb and relies on the calculation of the socket-stump interaction. A fast calculation is favorable in this case, that’s why we propose to use the Mass-Spring System (MSS) instead of the widely used FE method to model the soft tissues of the residual limb. A new configuration of the MSS model is proposed to respect the non-compressibility property of the soft tissues by adding non-linear “Corrective Springs”. The numeric model is to be generated from the scanned model of the stump. For this purpose, we propose a fusion scheme of four RGB-Depth sensors for a rapid and low-cost scan with error reduction techniques. Finally, the virtual residual limb is used in the socket designing phase. A parametric design method is proposed and investigated. The design problem is transformed into a constraint-satisfaction-problem whose constraints are derived from the inverse calculation of the stump-socket interaction. The inverse approach has been chosen to eliminate the need for expensive contact formulation. This fact leads to rapid calculations, and consequently, allows to provide real-time numerical feedback during the designing process. The validation was done by comparing the results of our system with the output of FE simulations. The system has been implemented with a user-friendly graphical interface and virtually tested and numerically validated. This system reduces the limitations of the current practices. However, a lot of works is still ahead to refine and develop the system and validate it with clinical experiments

>Magister Scientiae - MSc
Persons with lower limb amputations (LLA) experience different challenges in the community. These challenges include the physical, psychological and social function of an individual. Little is known in Malawi on what persons with lower limb amputations go through in the communities where they live. Therefore, the study aimed at exploring and determining community experiences of persons with LLA in Malawi. The study sought to address the following objectives: 1) To determine the functional and psychological status of persons with LLA in the community; 2) To explore and describe experiences on social participation of persons with LLA in the community; 3). To explore experiences on community re-integration following LLA. A mixed method approach was applied where quantitative and qualitative data were collected simultaneously to provide a more holistic overview of the experiences of persons with LLA at one point in time. The study setting was Queen Elizabeth Central Hospital (QECH) and Kamuzu Central Hospitals (KCH) (500 miles), located in Malawi. A sample of 180 participants was recruited to participate in the study. Three self-administered questionnaires (socio-demographic questionnaire, OPUS module of lower extremity functional status, and a Beck’s depression inventory scale) and a semi-structured interview guide were used for data collection. Thematic data analysis was used to analyze qualitative data, while quantitative data was analyzed using descriptive and inferential statistics. Ethical clearance was obtained from the University of the Western Cape Biomedical Research Ethics Committee (BMREC) and College of Medicine Research Ethics Committee (COMREC). Permission to conduct the study was obtained from KCH (500 miles) and QECH. Privacy andconfidentiality was strictly observed such that data obtained was anonymous. It was kept in a secure place, and electronic data was secured using a password.

ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, Nevada
Even after rehabilitation, patients with lower-limb amputation may continue to exhibit suboptimal gait. A wireless telemetry system, featuring force sensors, accelerometers, control electronics and a Bluetooth transmission module was developed to measure plantar pressure information and remotely monitor patient mobility. Plantar pressure characterization studies were performed to determine the optimal sensor placement. Finally, the wireless telemetry system was integrated with a previously developed haptic feedback system in order to allow remote monitoring of patient mobility during haptic system validation trials.

Though there are a variety of prosthetic limbs that address the motor deficits associated with amputation, there has been relatively little progress in restoring sensation. Prosthetic limbs provide little direct sensory feedback of the forces they encounter in the environment, but “closing the loop” between sensation and action can make a great difference in performance [1]. For users of lower limb prostheses, stair descent is a difficult and dangerous task. The difficulty in stair descent can be attributed to three different factors: 1) Absence of tactile and haptic sensations at the bottom of the foot. Although force on the prosthetic socket provides some haptic feedback of the terrain being stepped on, this feedback does not provide information on the location of the staircase edge. 2) Insufficient ankle flexion of lower limb prostheses. Dorsiflexion of the physiological ankle during stair descent is about 27°. Even prostheses that provide active dorsiflexion provide less than this number, and regular prostheses provide almost no ankle dorsiflexion. The first two factors are analogous to the sensation of stair descent for someone without amputation wearing ski boots. 3) Prosthetic feet are optimized for flat-ground walking, offering undesirable energy storage at ankle flexion and energy return at toe-off. This can result in unwanted extra energy at the end of stance phase, propelling the user forward down the stairs. Most lower limb prosthesis designs focus on flat ground walking, but there has been less progress in addressing the challenges of stair descent. One technique that users of prosthetic lower limbs can use for addressing these challenges is to employ an “overhanging toe” foot placement strategy. Under this strategy, the edge of the staircase is used as a pivot point for the foot to roll over the stair. This reduces the need for ankle flexion by allowing the knee and hip to compensate, and avoids storing energy in the prosthetic spring. This strategy is dynamic, and requires the user to know the amount of toe overhang to adjust the movement of the rest of the body. Most haptic devices built to assist individuals wearing prostheses focus on upper extremity tasks [2–4] or standing and walking [5,6]. Whereas previous lower limb sensory replacement systems have targeted standing measures, here we focus on stair descent. The system provides cues of the stair edge location via vibrotactile stimulations on the thigh.

This paper presents a new design framework to configure lower limb prostheses, both transfemoral and transtibial, where the key elements are the patient digital avatar and the domain knowledge. The technician is supported during the design process by the knowledge acquired from analysis of the traditional process and represented in the framework. The last one integrates virtual prototyping tools and knowledge management techniques. A specific software tool, named Socket Modelling Assistant, has been developed to design the socket, the custom-fit component of the prosthesis. A commercial CAD system is used to model the standard components (e.g., knee, foot and tubes) and to create the final assembly. Patient avatar and his/her data (e.g., anthropometric and physiological parameters) are the backbone of the whole product design process. They guide both the selection of standard components and the modelling of the socket digital model.

Vibrotactile feedback may be able to compensate for the loss of sensory input in lower-limb prosthesis users. Designing an effective vibrotactile feedback system would require that users could perceive and correctly respond to vibrotactile stimuli applied by the tactors. Our study explored three key tactor configuration variables (i.e. vibratory intensity, prosthetic pressure, spacing between adjacent tactors) through two experiments. The vibration propagation experiment investigated the effects of tactor configurations on vibratory amplitude at the prosthesis-limb interface. Results revealed a positive relationship between vibratory amplitude and intensity, and a negative relationship between vibratory amplitude and prosthetic pressure. The vibrotactile perception experiment investigated the effects of tactor configurations on user response accuracy, and found that greater spacing between tactors, and higher prosthetic pressure resulted in more accurate responses from the subjects. These findings inform the design of a vibrotactile feedback system for use in lower-limb prostheses: 1) the tactors may be best placed in areas of slightly elevated pressure at the prosthesis-limb interface; 2) a higher vibratory intensity level should improve performance for vibrotactile feedback systems; and 3) more spacing between adjacent tactors improves user response accuracy.

Modular lower limb prosthesis is composed by custom-fit parts, such as the socket containing the residual limb, and standard components available on market, such as knee or foot. For both custom and standard parts the support offered by existing design tools is not efficient or integrated enough and, as a result, most prosthetists do not use computer-aided tools and still rely only on their personal expertise. This paper presents an approach to design and configure complete lower limb prosthesis for transfemoral and transtibial amputees, using patient’s digital data (e.g., residual limb model acquired by MRI) and specification sheets of components. The ultimate goal is to realise a virtual laboratory where the technicians can design lower limb prosthesis guided step by step by the system. We have identified key patient’s characteristics guiding the prosthetist during the four main steps of the production process: acquiring patient’s data, socket modelling, standard components selection and prosthesis assembly and check. The developed innovative framework integrates different tools to guide the technicians during each design task providing specific knowledge and rules. Thus, it allows a quicker and easier definition of the virtual prosthesis, on which virtual test could be performed (e.g., pressure distribution on residual limb, gait evaluation) in order to be able to realize the definitive prosthesis at the first attempt. The results have been evaluated and validated with the technical staff of a certified orthopaedic laboratory.

Control of prosthetic limbs using myoelectric muscle potentials from the wearer’s residual limb enables direct control of artificial limb behavior. The typical approach entails the integration of surface electromyogram (sEMG) electrodes within the inner wall of the socket interface, located to target specific superficial muscles in the amputee’s residual limb. While myoelectric upper-limb control is commonplace in prosthetic practice, its use in lower-extremity devices has been slow to follow suit. Various research efforts have studied approaches to implementing myoelectric control of artificial leg behavior [1–4], but the need for myoelectric control in lower-limb prostheses has been limited by the lack of commercial prototypes with the capability of net power generation.

Advanced prostheses are currently being sold in consumer markets. The development of these advanced prostheses is largely a result of a better understanding of the biomechanics of human locomotion [1]. Powered and microprocessor controlled prostheses are offering better performance in a variety of movements and in the gait cycle. However the focus in lower limb prosthetics has been largely on locomotion (e.g. walking, stair gait and running). This study focuses on the sit and stand cycles of an individual with an Otto Bock C-leg and an Ossur Power Knee prosthesis, comparing his ability to utilize each prosthesis and comparing his cycle to that of a healthy (non-amputee) control subject. This study is part of a larger ongoing study of the sit and stand cycles seen in a large population of unilateral transfemoral prosthetic users of various kinds. The purpose of this study is to compare the difference in method of standing, and assistance provided by the prosthesis. With the knowledge gained from this study we hope to better understand the biomechanics of the sit and stand cycles, leading to better prostheses in the future.