Análisis numérico de una prótesis endobronquial utilizada para el tratamiento de cáncer pulmonar

Título en inglés: Numerical analysis of intrabronchial prosthesis used for the treatment of lung cancer Resumen En México, la mortalidad debido a enfermedades bronco-respiratorias se ubica en el sexto lugar según datos estadísticos dados por el Instituto Nacional de Enfermedades Respiratorias (INER). Esto genera la necesidad de incrementar la eficiencia en la aplicación de los tratamientos usados para este tipo de patología. Algunos de los métodos utilizados con mayor frecuencia para el tratamiento de estas dolencias hacen uso de micro dispositivos, también conocidos como válvulas endobronquiales. Este es un sistema alternativo que evita cirugías invasivas y logra prolongar e incrementar la calidad de vida de los pacientes. En este trabajo se presenta el análisis del desempeño de la válvula IBV®. Para el desarrollo del estudio numérico se determinaron las dimensiones y propiedades mecánicas del modelo a partir de catálogos del fabricante. Se desarrolló un modelo para el cual se consideraron las propiedades del Nitinol® y Silastic®. Asimismo, se propusieron dos condiciones de operación para la válvula, una anclada en el bronquio y la otra en la condición en la que se encuentra plegada dentro del broncoscopio. Se utilizó el Método del elemento finito (MEF) para simular las condiciones de trabajo de la válvula. Los resultados encontrados muestran el funcionamiento estructural y el nivel de los esfuerzos generados en el implante durante el ciclo de respiración forzada del individuo. Además, se proporcionan las bases para generar un nuevo dispositivo que pueda emular el funcionamiento de este tipo de implantes y aumente la eficiencia del tratamiento de dicha patología. Palabras clave: aleaciones con memoria de forma, cáncer pulmonar, válvulas endobronquiales. Abstract In Mexico, the mortality rate due to bronchial respiratory sickness is placed in the sixth position, according to statistics from the National Institute of Breathing Sickness (INER), so it is convenient to increment the efficiency of treatments for those pathologies. The intrabronchial valve is a recommended alternative method; being it main objective to avoid invasive surgery and increase the time and quality of patient´s life. Within this work a biomechanical analysis of an IBV® valve is carried out. Regarding the numerical analysis, the dimensions and mechanical properties of the valve were proposed based on catalogues published by the manufacturer as more reliable information was not available in the open literature. As a result, a new model was developed in which both materials Nitinol® and Silastic® are considered as the main valve materials. The proposed working conditions assume that the valve is implanted in folded form at the bronchus and then anchored when it is unfolded. Finite Element Method (FEM) was used to simulate the proposed working conditions. Results obtained show the structural performance and the level of stress generated in the implant during the breathing cycle. In addition, it provides the knowledge to generate a new device that could emulate the performance of these implants and develop a more efficient treatment this disease. Key words: Shape memory alloys, lung cancer, intrabronchial valves

Análisis numérico de una prótesis endobronquial utilizada para el tratamiento de cáncer pulmonar

Bronchial respiratory sickness occupies sixth place in Mexican mortality rates according to National Institute of Breathing Sickness (INER) statistics, meaning that the efficiency of treatment for this disease should be increased. The intrabronchial valve is a recommended treatment method, its main objective being an alternative for avoiding invasive surgery and increasing the length and quality of a patient�s life. An IBV® valve was submitted to biomechanical analysis. Regarding numerical analysis, the valve�s dimensions and mechanical properties were proposed using manufacturers� catalogues as more reliable information was not available in the pertinent available literature. As a result, a new model was developed in which nitinol® and silastic® were considered as the main valve materials. The proposed working conditions assumed that the valve had been implanted in folded form at the bronchus and then anchored when it is unfolded. The finite element method (FEM) was used for simulating the proposed working conditions. The results showed the structural performance and stress level produced in the implant during a person�s forced breathing cycle. They also provided the knowledge for producing a new device that could emulate the performance of these implants and develop more efficient treatment for this disease.En México, la mortalidad debido a enfermedades bronco-respiratorias se ubica en el sexto lugar según datos estadísticos dados por el Instituto Nacional de Enfermedades Respiratorias (INER). Esto genera la necesidad de incrementar la eficiencia en la aplicación de los tratamientos usados para este tipo de patología. Algunos de los métodos utilizados con mayor frecuencia para el tratamiento de estas dolencias hacen uso de micro dispositivos, también conocidos como válvulas endobronquiales. Este es un sistema alternativo que evita cirugías invasivas y logra prolongar e incrementar la calidad de vida de los pacientes. En este trabajo se presenta el análisis del desempeño de la válvula IBV®. Para el desarrollo del estudio numérico se determinaron las dimensiones y propiedades mecánicas del modelo a partir de catálogos del fabricante. Se desarrolló un modelo para el cual se consideraron las propiedades del Nitinol® y Silastic®. Asimismo, se propusieron dos condiciones de operación para la válvula, una anclada en el bronquio y la otra en la condición en la que se encuentra plegada dentro del broncoscopio. Se utilizó el Método del elemento finito (MEF) para simular las condiciones de trabajo de la válvula. Los resultados encontrados muestran el funcionamiento estructural y el nivel de los esfuerzos generados en el implante durante el ciclo de respiración forzada del individuo. Además, se proporcionan las bases para generar un nuevo dispositivo que pueda emular el funcionamiento de este tipo de implantes y aumente la eficiencia del tratamiento de dicha patología

Análisis numérico sobre esfuerzos y áreas de contacto en una PTR Scorpio II® Stryker®: Base para el diseño de PTR personalizada al fenotipo Mexicano

Wear of UHMWPE inserts continues affecting the longevity of total knee replacements (TKR) together with septic loosening, and both constitute two main causes of prosthesis failure. It is necessary to find appropriate solutions to avoid excessive wear and failure of polyethylene inserts. In this work a study was carried out by means of numeric simulation of a Scorpio II® Stryker® TKR, which was retired due to wear of UHMWPE in the Hospital 1° de Octubre of ISSSTE in Mexico city. Hypotheses of Bartel et al. (1995) and Chillag et al. (1991) were used, which settle down that wear of polyethylene can decrease using thicker tibial inserts, which can be reduced contact pressures. Analyses of this work was carried out by means of FEM varying insert thickness of 6, 8, 10, 12 and 14 mm, considered quasi-static axial loads actuating on the articulation with zero degrees of flexion and loads equivalent to 1.33 times of bodyweight of a subject of 75 kg (736 N) was considered. Normalized gait cycle was employed and results obtained are similar to those reported by Bei et al. (2004) and Deen et al. (2006). After validating the method, a model of study case of TKR in FEM was developed and the curves of stress and contact areas of UHMWPE were determined, with which important information was obtained to modify the design, as well as to obtain a prosthesis of optimal conformity in both coronal and sagital planes of the femoral and UHMWPE inserts, in agreement with characteristics of the Mexican phenotype.El desgaste de los insertos de Polietileno de Ultra-Alto Peso Molecular (UHMWPE pos sus siglas en inglés) continúa afectando la longevidad de las prótesis totales de rodilla (PTR) junto con el aflojamiento aséptico, y ambos constituyen las dos principales causas de falla de las prótesis. Considerando esto, es necesario encontrar soluciones adecuadas para evitar el desgaste excesivo y hasta la ruptura de los insertos de polietileno. En este trabajo se realizó el estudio mediante simulación numérica de una PTR Scorpio II® Stryker®, la cual se retiró por desgaste del inserto de UHMWPE en el Hospital 1° de Octubre del ISSSTE en México. Se utilizaron las hipótesis de Bartel et al. (1995) y Chillag et al. (1991) para la validación del método numérico utilizado, las cuales establecen que el desgaste del polietileno puede reducirse utilizando insertos tibiales de mayor espesor, lo cual disminuye las presiones de contacto. Los análisis se realizaron mediante MEF variando el espesor del inserto de 6, 8, 10, 12 y 14 mm, suponiendo cargas axiales de tipo cuasi-estático en la articulación a cero grados de flexión, para 1.33 veces el peso de un individuo de 75 kg (736 N) empleando el ciclo normalizado de marcha. Los resultados obtenidos muestran similitud con los reportados por Bei et al. (2004) y Deen et al. (2006). Después de validar el método, se desarrolló el modelo de MEF de la PTR y se determinaron las curvas de esfuerzo y de áreas de contacto del inserto de UHMWPE, con lo que se obtuvo información importante para modificar el diseño y obtener una prótesis de geometría conforme en los planos coronal y sagital del inserto femoral y el inserto de polietileno, de acuerdo con el fenotipo mexicano

Análisis numérico sobre esfuerzos y áreas de contacto en una ptr scorpio ii® stryker®. base para el diseño de ptr personalizada al fenotipo mexicano

Título en ingles: Numerical analysis on effort and contact areas in a TKR Scorpio II® of Stryker®. Basis for the design of customized TKR in accordance with the Mexican PhenotypeTítulo corto: Análisis numérico sobre esfuerzos y áreas de contacto en una PTRResumen: El desgaste de los insertos de Polietileno de Ultra-Alto Peso Molecular (UHMWPE pos sus siglas en inglés) continúa afectando la longevidad de las prótesis totales de rodilla (PTR) junto con el aflojamiento aséptico, y ambos constituyen las dos principales causas de falla de las prótesis. Considerando esto, es necesario encontrar soluciones adecuadas para evitar el desgaste excesivo y hasta la ruptura de los insertos de polietileno. En este trabajo se realizó el estudio mediante simulación numérica de una PTR Scorpio II® Stryker®, la cual se retiró por desgaste del inserto de UHMWPE en el Hospital 1° de Octubre del ISSSTE en México. Se utilizaron las hipótesis de Bartel et al. (1995) y Chillag et al. (1991) para la validación del método numérico utilizado, las cuales establecen que el desgaste del polietileno puede reducirse utilizando insertos tibiales de mayor espesor, lo cual disminuye las presiones de contacto. Los análisis se realizaron mediante MEF variando el espesor del inserto de 6, 8, 10, 12 y 14 mm, suponiendo cargas axiales de tipo cuasi-estático en la articulación a cero grados de flexión, para 1.33 veces el peso de un individuo de 75 kg (736 N) empleando el ciclo normalizado de marcha. Los resultados obtenidos muestran similitud con los reportados por Bei et al. (2004) y Deen et al. (2006). Después de validar el método, se desarrolló el modelo de MEF de la PTR y se determinaron las curvas de esfuerzo y de áreas de contacto del inserto de UHMWPE, con lo que se obtuvo información importante para modificar el diseño y obtener una prótesis de geometría conforme en los planos coronal y sagital del inserto femoral y el inserto de polietileno, de acuerdo con el fenotipo mexicano.Palabras clave: simulación numérica; desgaste; presión de contacto; inserto femoral; plato tibial.Abstract: The Wear of UHMWPE inserts continues affecting the longevity of total knee replacements (TKR) together with septic loosening, constitute the two main causes of prosthesis failure. Bearing this in mind, it is necessary to find appropriate solutions to avoid excessive wear and even the rupture of polyethylene inserts. In this work a study was carried out by means of numeric simulation of a Scorpio II® Stryker® TKR, which was removed due to wearing of the UHMWPE insert in the Hospital 1° de Octubre of ISSSTE in Mexico city. Hypotheses of Bartel et al. (1995) and Chillag et al. (1991) were used to validate the numerical method applied, proving that wear of polyethylene can decrease using thicker tibial inserts, which reduces contact pressures. The analyses of this work carried out by means of  FEM employing inserts of thicknesses of 6, 8, 10, 12 and 14 mm, putting quasi-static axial loads on the articulation with no degree of flexion and loads equivalent to 1.33 times the bodyweight of a subject of 75 kg (736 N), proved under regular walking conditions drew  similar results to those reported by Bei et al. (2004) and Deen et al. (2006). After validating the method, a model of study case of TKR in FEM was developed and the points of effort and contact areas of UHMWPE were identified. Thus, important information was obtained to modify the design, as well as to produce a prosthesis of optimal geometrical conformity in both, the coronal and the sagital planes of the femoral and UHMWPE inserts, complying with the requirements of the Mexican phenotype.Key words: Numerical simulation; wear; contact pressure; femoral insert; tibial tray; UHMWPE;  geometrical conformit

High Biofidelity 3D Biomodel Reconstruction from Soft and Hard Tissues (Knee), FEM, and 3D Printing: A Three-Dimensional Methodological Proposal

The modelling of biological structures has allowed great advances in Engineering, Biology, and Medicine. In turn, these advances are seen from the design of footwear and sports accessories, to the design of prostheses, accessories and rehabilitation treatments. The reproduction of the various tissues has gone through an important evolution thanks to the development of computer systems and programs. However, knowledge of the medical-biological and engineering areas continues to be required, and it involves a considerable investment of time and resources. The resulting biomodels still require great precision. The present work shows a methodology that allows to optimize computational resources and reduce elaboration time of biomodels. Through this methodology, it is possible to generate a biomodel of high biofidelity of a human knee. This biomodel is constituted by hard tissues (cortical and trabecular bones) and soft tissues (ligaments and meniscus) resulting in the modelling of the lower third of the femur, the tibial plateaus, the anterior cruciate ligament, posterior cruciate ligament, external lateral ligament, interior lateral ligaments, and the meniscus. With this model and methodology, it is possible to perform numerical analyses that will provide results very similar to those of real life. As, the methodology allows to assign the mechanical properties to each tissue and the anatomical structure

Numerical evaluation of the shot peening process and determination of the residual stress fields by the crack compilance method

En la literatura mundial, se encuentran muy bien establecidos los beneficios que presenta el proceso de granallado. Sin embargo, este proceso es una tarea de desarrollado artesanal (en algunos de los casos)o dependiente de la experiencia del operario. Una de las principales virtudes de este proceso, es el fortalecimiento de la superficie y la elevación del esfuerzo de cedencia del material. Este incremento de la resistencia en elmaterial , se debe a la inducción de un campo de esfuerzos residuales de tipo compresivo. La in inducción de este tipo de campo de esfuerzos residuales es en extremo benéfico para el componente , ya que esta operación hace que los elementos sometidos a cargas cíclicas eleven su capacidad de resistencia a la fatiga en la superficie (propagación de la grieta) y puedan de esta manera tener una vida útil más larga, por otra parte, que las cargas aplicadas a estos elementos se puedan elevar considerablemente. En este artículo, se realiza una comparación de la obtención del campo de esfuerzos residuales inducido por el granallado, realizado por dos medios, el anlítico y por el Método del Elemento Finito (MEF), esto con el fin de obtener un método de determinación de esfuerzos residuales por medio del MEF, que se acerque en mayor medida a los registrados por la parte experimental. El análisis numérico que en este trabajo se presenta; se realizó en 2D, considerando condiciones cuasi-estáticas y no tomado en cuenta el disparo aleatorio del proceso de granallado. Asimismo, se presentan los resultados obtenidos en el efecto que produce el cambio de tamaño de bola. De esta manera, en posteriores análisis, se podrá realizar una evaluación de los mejores resultados obtenidos por medio del MEF variando determinados factores que arrojen las condiciones idóneas de los parámetros en la prueba experimental, reduciendo costo y tiempo.In the open literatura around the world, it has been very well established the benefits that produces the shot peening process. Nevertheless, this process is a task, in some of the cases, of the development of handcrafted and/ or dependent on the experience of the workman. One of the principal virtues of this process, is the strengthening of the surface and increase in the yield stress of the material. This strengthening or increase of the resistance in the material, owes to the induction of a residual stress field of compressive type. The induction of this type of effect is extremely beneficial for the component, since this operation does that the elements submitted to cyclical loads raise its fatigue resistance (crack propagation)on the surface and could have hereby a longer useful life, and in the order hand, the applied loads to these elements could raise considerably. In this article, it is presented a comparison of the obtained residual stress field by shot peening by two methods, by the analytical and the finite element method (FEM), in order to obtain a confinable method for the evaluation of residual stresses, which approaches in major measurement to the registered ones by the experimental procedure. The numerical analysis performed in this work, it was done by 2D simulation, considering quasi-static conditions and not accounting random shot in the shot peening process. Also it is present the results obtained in the effect that the ball size produced. Hereby, in a later analyses, it will be possible to do an evaluation of the best results obtained by means of the FEM, changing certain factors that throw the suitable conditions of the parameters in the experimental tests, reducing cost and timePeer Reviewe

Mechanobiological Analysis of Molar Teeth with Carious Lesions through the Finite Element Method

The analysis of the distribution of stress in dental organs is a poorly studied area. That is why computational mechanobiological analysis at the tissue level using the finite element method is very useful to achieve a better understanding of the biomechanics and the behaviour of dental tissues in various pathologies. This knowledge will allow better diagnoses, customize treatment plans, and establish the basis for the development of better restoration materials. In the present work, through the use of high-fidelity biomodels, computational mechanobiological analyses were performed on four molar models affected with four different degrees of caries, which are subjected to masticatory forces. With the analyses performed, it is possible to observe that the masticatory forces that act on the enamel are not transmitted to the dentin and to the bone and periodontal ligament to protect the nerve, as it happens in a healthy dental organ. With the presence of decay, these forces are transmitted partly to the pulp. The reactions to the external loads on the dental organs depend on the advances of the carious lesion that they present, since the distribution of stresses is different in a healthy tooth

Numerical Analysis of Masticatory Forces on a Lower First Molar considering the Contact between Dental Tissues

The aim of the present work is to identify the reactions of the dental organs to the different forces that occur during chewing and the transcendence of the union and contact maintained by the dental tissues. The study used a lower first molar biomodel with a real morphology and morphometry and consisting of the three dental tissues (enamel, dentin, and pulp) each with its mechanical properties. In it, two simulations were carried out, as would the process of chewing a food. One of the simulations considers the contact between the enamel and the dentin, and the other does not take it into account. The results obtained differ significantly between the simulations that consider contact and those that do not, establishing the importance of taking this contact into account. In this way, the theories that establish horizontal and lateral occlusion forces are present during the functional chewing process which are viable to be correct. The case studies carried out present not only the reasons for the failure of enamel but also the failure of the restoration materials used. This reflection will allow the development of more adequate materials, mechanical design of prostheses, implants, and treatment

Multi-objective optimization of a parallel manipulator for the design of a prosthetic arm using genetic algorithms

Abstract This paper presents a synthesis of a spherical parallel manipulator for a shoulder of a seven-degrees-of-freedom prosthetic human arm using a multi-objective optimization. Three design objectives are considered, namely the workspace, the dexterity, and the actuators torques. The parallel manipulator is modelled considering 13 design parameters in an optimization procedure. Due to the non-linearity of the design problem, genetic algorithms are implemented. The outcomes show that a suitable performance of the manipulator is achieved using the proposed optimization

Numerical Analysis of a Dental Zirconium Restoration and the Stresses That Occur in Dental Tissues

When it is about restorative dental materials, aesthetics is traditionally preferred. This has led to the selection of materials very visually similar to the enamel, but unfortunately, their mechanical properties are not similar. This often translates into disadvantages than advantages. In the present work, a comparison is made of the stresses that occur during dental occlusion (dental bit) in a healthy dental organ and those that are generated in a dental organ with a dental zirconium restoration. Numerical simulation was carried out by means of the Finite Element Method, in computational biomodels, from Cone-Beam Tomography, to obtain the stresses generated during dental occlusion. It was found that the normal and von Mises stresses generated are substantially greater in the molar with restoration compared to those produced in the healthy molar. In addition, the normal function of the enamel and dentin to disperse these stresses to prevent them from reaching the pulp is altered. Therefore, it is necessary to analyze the indiscriminate use of this restoration material and consider other aspects, in addition to aesthetics and biocompatibility for the choice of restorative materials such as biomechanical compatibility