Sensor capacitivo para a monitorização da interface osso-implante

Mestrado em Engenharia MecânicaOs implantes ósseos usados atualmente não são capazes de substituir integralmente a articulação onde são aplicadas. A redistribuição da carga no osso origina o efeito stress-shielding, o que pode provocar perda de massa óssea e migração do implante. O desgaste das componentes integrais do implante também causa alterações na interface ossoimplante. Os pacientes com estas complicações, podem ser submetidos a operações de revisão, onde o risco de insucesso e infeções é elevado. Para prevenir tais casos, recentemente foi proposto o conceito de Implante Instrumentado para dotar esta tecnologia com: sistemas de atuação (sobre a interface osso-implante), monitorização da integração osso-implante, sistemas de comunicação implante-exterior e sistemas de geração autónoma de energia. No entanto, uma revisão da literatura mostrou que os sistemas de monitorização propostos não são viáveis para serem incorporados em implantes instrumentados. Este é um estudo preliminar que visa propor um sistema de monitorização capacitivo com configuração em co-superfície listrado integrado num circuito ressonante RLC. Foi desenvolvido um aparato experimental para o teste do sistema in vitro usando estruturas de osso porcino. Observaram-se variações de 0,2 fF da capacitância por cada μm de deslocamento relativo entre a estrutura óssea e o sistema de monitorização. Embora preliminar, este estudo apresenta resultados promissores para a monitorização de diferentes interfaces osso-implante usando em sistemas capacitivos em co-superfície.The prostheses currently used, are not able to fully replace the joint where they are applied. The redistribution of the load in the bone causes stressshielding, which origins loss of bone mass, and migration of the implant. Also, the wear of the integral components of the prosthesis causes changes between the interface of the bone and the implant. Patients with these complications can be submitted to review surgeries, where the risk of failure and infection is high. To prevent such cases, instrumented prosthesis have been recently proposed, to enhance this technology with: actuation systems (over the bone-implant interface), osseointegration monitoring, communication systems between implant-exterior and systems capable of generating energy autonomously. However, a review over these technologies showed that the proposed monitoring systems are not feasible to be incorporated into instrumented implants. This is a preliminary study which aims to advocate a monitoring capacitive system with a cosurface stripe pattern integrated in a RLC resonant circuit. An experimental apparatus was developed to test the system in vitro using a porcine bone. Variations of 0,2 fF in the capacitance were observed, for each ìm of relative movement between the bone and the monitoring system. Although preliminary, this study presents promising result for monitoring different bone-implant interfaces using a cosurface capacitive system

Analysis of orthopaedic device development in South Africa: Mapping the landscape and understanding the drivers of knowledge development and knowledge diffusion through networks

An orthopaedic medical device refers to a part, implant, prosthetic or orthotic which is used to address damage to the body's musculoskeletal system, primarily by providing stability and mobility. Orthopaedic medical devices play a role in injury-related disorders, which have been highlighted as a key element of the quadruple burden of disease in South Africa. In this thesis, orthopaedic devices are conceptualised as a technological field and a technological innovation system (TIS) framework is applied to understand orthopaedic device development in South Africa. Knowledge development and knowledge diffusion are fundamental components of any innovation system. The thesis hypothesises that the functions “knowledge development” and “knowledge diffusion through networks” of the orthopaedic devices TIS are influenced by contextual factors. The objectives of the study are: to identify the actors who generate knowledge for orthopaedic device development and to characterise the relationships between them; to identify focus areas of orthopaedic device development; to provide insight into the drivers and barriers to knowledge development and diffusion in the TIS; and to identify the contextual factors that influence knowledge dynamics in the TIS. These objectives are investigated using social network analysis based on bibliometric data (scientific publications and patents), keyword networks, a review of institutions, and a set of case studies where the primary data source are interviews with actors. Actors producing knowledge were from the university, healthcare, industry and science council sectors, although science councils played a small role. International actors were shown to bring new ideas into the TIS. The networks were fragmented, illustrating that knowledge diffusion through the networks was limited. This was especially the case in the patent networks as many actors patent in isolation. The keyword networks highlighted unrealised collaboration potential between actors based on their common research interests. The case studies revealed features of cross-sector interaction for orthopaedic device development not evident from network analysis based on bibliometric data. Drivers of knowledge development and knowledge diffusion were: inter-sectoral collaboration; the availability of resources; the affordability of available devices; and the positive externalities of allied TISs. The main barrier to knowledge development and diffusion was in the form of barriers to intersectoral collaboration. These include unmatched expectations from partners in collaboration, different views on intellectual property ownership, and burdensome university administrative processes. The orthopaedic devices TIS was structurally coupled to the embedded TIS and sectoral contexts, and externally linked and structurally coupled to its political context. Knowledge development and diffusion was found to be positively enhanced by innovation in the additive manufacturing TIS, with shared structural elements and resources. Knowledge development and diffusion was influenced by sectoral dynamics of the university, healthcare and industry sectors. This thesis makes the following contributions. First, it applies the TIS framework to a new focus area, namely medical device development, in a developing country context. Second, it makes two unique methodological contributions: it presents an index to capture the extent of sectoral collaboration in a network; and it develops a method for determining the collaboration potential of actors in a network based on cognitive distance