Biomechanical Fatigue Behavior of a Dental Implant Due to Chewing Forces: A Finite Element Analysis.

The use of titanium as a biomaterial for the treatment of dental implants has been successful and has become the most viable and common option. However, in the last three decades, new alternatives have emerged, such as polymers that could replace metallic materials. The aim of this research work is to demonstrate the structural effects caused by the fatigue phenomenon and the comparison with polymeric materials that may be biomechanically viable by reducing the stress shielding effect at the bone-implant interface. A numerical simulation was performed using the finite element method. Variables such as Young's modulus, Poisson's coefficient, density, yield strength, ultimate strength, and the S-N curve were included. Prior to the simulation, a representative digital model of both a dental implant and the bone was developed. A maximum load of 550 N was applied, and the analysis was considered linear, homogeneous, and isotropic. The results obtained allowed us to observe the mechanical behavior of the dental implant by means of displacements and von Mises forces. They also show the critical areas where the implant tends to fail due to fatigue. Finally, this type of non-destructive analysis proves to be versatile, avoids experimentation on people and/or animals, and reduces costs, and the iteration is unlimited in evaluating various structural parameters (geometry, materials, properties, etc.).

Numerical Analysis of Zirconium and Titanium Implants under the Effect of Critical Masticatory Load.

Dental implants have become an alternative to replace the teeth of people suffering from edentulous and meet the physiological and morphological characteristics (recovering 95% of the chewing function). The evolution and innovation of biomaterials for dental implants have had a trajectory that dates back to prehistory, where dental pieces were replaced by ivory or seashells, to the present day, where they are replaced by metallic materials such as titanium or ceramics such as zirconium or fiberglass. The numerical evaluation focuses on comparing the stress distribution and general displacement between different dental implants and a healthy tooth when applying a force of 850 N. For the analysis, a model of the anatomical structure was developed of a healthy tooth considering three essential parts of the tooth (enamel, dentin, and pulp). The tooth biomodel was established through computed tomography. Three dental implant models were considered by changing the geometry of the abutment. A structural simulation was carried out by applying the finite element method (FEM). In addition, the material considered for the analyses was zirconium oxide (ZrO2), which was compared against titanium alloy (Ti6Al4V). The analyses were considered with linear, isotropic, and homogeneous properties. The variables included in the biomodeling were the modulus of elasticity, Poisson's ratio, density, and elastic limit. The results obtained from the study indicated a significant difference in the biomechanical behavior of the von Mises forces and the displacement between the healthy tooth and the titanium and zirconium implant models. However, the difference between the titanium implant and the zirconium implant is minimal because one is more rigid, and the other is more tenacious.

Traumatic Impact Assessment of CPR Load on a Human Ribcage.

Chest compression is a parameter of injury criteria assessment for human beings. Additionally, it is used to find the external compression response as a result of vehicle crashes, falls, or sporting impacts. This behavioral feature is described by many deterministic models related to specific experimental tests, hindering distinct scenarios. The present study evaluates the energy absorbed as a function of rib compression. The proposed model was obtained from three different computed tomography (CT) studies. The anthropometric values are interpolated to obtain a parametric curve for a human rib's average size. The computed results are compared against an STL-DICOM® file used to obtain a virtual reconstruction of one rib. A numerical model of the behavior of the thorax displacement expressed injury in the human rib model's stiffness. The proposed model is used to determine the correlation of the input payload versus the numerical stiffness value. The outcome is confirmed by numerical analyses applied to a virtual human rib reconstruction.

Numerical Analysis of the ACL, with Sprains of Different Degrees after Trauma.

Nowadays, cruciate ligament injuries have increased in incidence, since practicing a sport or physical activity has become a trend in current societies. Although this lifestyle generates multiple benefits, as a consequence, injury has also increased. Due to its nature and complexity, the ligaments of the knee are those that are most frequently affected, mainly the ACL (anterior cruciate ligament). This tissue reacts to overexertion or movements out of range, either caused by the exercise itself or caused by trauma caused by the practice of physical activity, causing various degrees of sprain. Whatever the etiology of these injuries, they will require a therapy indicated for each degree of injury. This therapy initially entails immobilization of the affected area and later; physical therapy will be required to a lesser or greater degree. Commonly, in the physiotherapy of these injuries, rehabilitation exercises are prescribed, where the physiotherapist asks a patient to use equipment with an estimated weight. However, the effectiveness of a generalized therapy in this way does not always give the expected results. This is related to the fact that these therapies are standardized and do not consider some factors such as the remaining muscle fibres that are not directly affected by the sprain, which does not mean that they should not be considered. Therefore, in the present work, a biomodel of a human knee has been developed and used to evaluate numerically how the ACL acts under an external load, when there are different degrees of injuries, caused by trauma. Four case studies were considered: Case 1 (control case) where the ACL is healthy, Case 2 where the ACL presents a 1st-degree sprain, Case 3 where the ACL presents a 2nd-degree sprain, and finally Case 4 where the ACL presents a 3rd-sprain grade. After performing the analyses, in the control case, it was found that it presents a balance between tensile and compressive stresses. While in the 4th case, the most critical tensile stress decreases while compression stresses increase. This shows that the ligament, having considerable damage, no longer works as it should and can eventually damage the collateral structures. It was found that, when there was a sprain, where the continuity of the ligament is compromised, a second torsional moment occurs in the ACL which causes the tissue fibres not to act according to their normal physiology or in a healthy state. The results obtained from the present study provide the possibility of predicting where the following injuries will occur by considering the von Mises failure criterion. Likewise, they will allow to improve the therapeutic procedures considering not only the injured structure but also the system as a whole.

Redesign of a Piston for a Diesel Combustion Engine to Use Biodiesel Blends.

Biofuels represent an energy option to mitigate polluting gases. However, technical problems must be solved, one of them is to improve the combustion process. In this study, the geometry of a piston head for a diesel engine was redesigned. The objective was to improve the combustion process and reduce polluting emissions using biodiesel blends as the fuel. The methodology used was the mechanical engineering design process. A commercial piston (base piston) was selected as a reference model to assess the piston head's redesign. Changes were applied to the profile of the piston head based on previous research and a new model was obtained. Both models were evaluated and analyzed using the finite element method, where the most relevant physical conditions were temperature and pressure. Numerical simulations in the base piston and the new piston redesign proposal presented similar behaviors and results. However, with the proposed piston, it was possible to reduce the effort and the material. The proposed piston profile presents adequate results and behaviors. In future, we suggest continuing conducting simulations and experimental tests to assess its performance.

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.

High-Biofidelity Biomodel Generated from Three-Dimensional Imaging (Cone-Beam Computed Tomography): A Methodological Proposal.

Experimental research on living beings faces several obstacles, which are more than ethical and moral issues. One of the proposed solutions to these situations is the computational modelling of anatomical structures. The present study shows a methodology for obtaining high-biofidelity biomodels, where a novel imagenological technique is used, which applies several CAM/CAD computer programs that allow a better precision for obtaining a biomodel, with highly accurate morphological specifications of the molar and tissues that shape the biomodel. The biomodel developed is the first lower molar subjected to a basic chewing simulation through the application of the finite element method, resulting in a viable model, able to be subjected to various simulations to analyse molar biomechanical characteristics, as well as pathological conditions to evaluate restorative materials and develop treatment plans. When research is focused in medical and dental investigation aspects, numerical analyses could allow the implementation of several tools commonly used by mechanical engineers to provide new answers to old problems in these areas. With this methodology, it is possible to perform high-fidelity models no matter the size of the anatomical structure, nor the complexity of its structure and internal tissues. So, it can be used in any area of medicine.

Identification of Stress Fields in a Customized Mandibular Reconstruction Based on a Photoelastic Model.

Tumors, trauma and infections are the main reasons for subjecting a patient to a bone reconstruction made with the use of bone grafts or prosthetic elements, using for example components such as osteosynthesis plates, meshes and screws for their stabilization.This study focuses on the photoelastic analysis of a customized prosthesis of the jaw for a patient diagnosed with osteonecrosis. A resin model was manufactured as follows: DICOM files were processed in ScanIP software to obtain an STL file that was used to generate an antagonist model of the healthy section of the jaw using CATIA software, then, models were printed in Acrylonitrile Butadiene Styrene (ABS). Following the resin casting technique, the printed model of the jaw was used to construct a resin model, which is tested to determine its mechanical behavior.After carrying out the photoelastic analysis, it was found that the assembly process generates stress concentration zones. Here, the stress reaches a maximum value after the application of a bite force of 130.9 N in the premolars. In this study near the premolars, 3 stress concentration zones were identified and overlap of stress fields is reveled.The results show the importance of planning in the design and assembly process to obtain the best results in the reconstruction, reducing in this way the risk of a surgical reoperation due to problems of rupture or loosening of the prosthesis.

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.

Evaluación inicial de parámetros de campo en un biodigestor anaeróbico para el tratamiento de aguas residuales / Preliminary evaluation of field parameters at an anaerobic biodigester designed for the treatment of wastewater

El biodigestor anaerobio utilizado en este estudio, se diseñó para tratar agua residual doméstica en un sanitario de prueba, y se caracteriza por ser de: flujo continuo, baja carga orgánica y tener cuatro etapas de proceso. La importancia del prototipo estudiado radicó en las condiciones reales en que se probó. La primera etapa consistió en la selección del sitio, construcción del prototipo en ferrocemento con capacidad de 1m³, impermeabilización y carga. En esta etapa se inoculó el reactor con materia orgánica procedente de las descargas del sanitario, durante el periodo de agosto a diciembre de 2011. La evaluación de este periodo consistió en la medición de parámetros de campo: pH, conductividad eléctrica, sólidos sedimentables, temperatura del influente - efluente y oxígeno disuelto del sistema que permitieron verificar el comportamiento del proceso del digestor durante la fase de arranque. Los resultados obtenidos para estas determinaciones a la entrada y salida del biodigestor respectivamente son los siguientes: pH (8.03; 8.43), conductividad eléctrica (1510.83 µS/cm; 1207.00 µS/cm), temperatura del proceso (19.2°C; 20.1°C), sólidos sedimentables (144.5mL/L; 0.02mL/L), oxígeno disuelto (4.5992 mg/L; 0.1924 mg/L) estos datos proporcionaron un punto de partida para el tratamiento de aguas residuales de tipo doméstica.

The anaerobic biodigester analyzed in the present study was designed for the treatment of domestic wastewater in a test restroom, characterized by its continuous flow, low organic load and a four-stage processing system. The value of the prototype under research consists in the real daily conditions under which it was tested. The first stage consisted of the site selection, and the manufacture of a waterproof iron reinforced cement prototype, with a 1m³ loading capacity. At this stage, during the period from august to december 2011, the reactor was inoculated with organic matter originating from the aforementioned restroom discharges. The evaluation of this stage consisted in taking measurements of the following field parameters: pH, electrical conductivity, sedimentable solids, and inflow and outflow temperature along the system. These records substantiated the behaviour of the processes within the digester during the starting phase. The results obtained through these determinations at both the biodigester entry and exit points are respectively: pH (8.03; 8.43), electrical conductivity (1510.83 µS/cm; 1207.00 µS/cm), inflow and outflow temperatures (19.2°C; 20.1°C), sedimentable solids (144.5mL/L; 0.02mL/L) and dissolved oxygen (4.5992 mg/L; 0.1924 g/L). These data provided a starting point for the treatment of domestic wastewater.

Determination of the mechanical properties of lumbar porcine vertebrae with 2D digital image correlation.

PURPOSE: To evaluate the strain fields and to calculate the modulus of elasticity and Poisson's ratio of trabecular bone of the 6 lumbar vertebrae of the porcine spine by a 2-dimensional digital image correlation (2D DIC). METHODS: This study was performed through a 2D DIC technique and the specimens were tested under compression. The resulting images were analyzed numerically by 2D DIC. Then, representative regions of interest were examined. The strain fields were determined and stress-strain curves were obtained. RESULTS: The full field measurement of the strain in the lumbar bone spine was evaluated and with this data, the Young's modulus and Poisson's ratio were determined. CONCLUSIONS: This research highlights the potential applications of noninvasive acquisition techniques in biomechanical analysis. This is useful in the mechanical characterization of bony structures and in the design of prostheses.

Diseño mecánico de un exoesqueleto para rehabilitación de miembro superior / Mechanical design of an exoskeleton for upper limb rehabilitation

El ritmo de vida actual, tanto sociocultural como tecnológico, ha desembocado en un aumento de enfermedades y padecimientos que afectan las capacidades físico-motrices de los individuos. Esto ha originado el desarrollo de prototipos para auxiliar al paciente a recuperar la movilidad y la fortaleza de las extremidades superiores afectadas. El presente trabajo aborda el diseño de una estructura mecánica de un exoesqueleto con 4 grados de libertad para miembro superior. La cual tiene como principales atributos la capacidad de ajustarse a la antropometría del paciente mexicano (longitud del brazo, extensión del antebrazo, condiciones geométricas de la espalda y altura del paciente). Se aplicó el método BLITZ QFD para obtener el diseño conceptual óptimo y establecer adecuadamente las condiciones de carga de servicio. Por lo que, se definieron 5 casos de estudio cuasi-estáticos e implantaron condiciones para rehabilitación de los pacientes. Asimismo, mediante el Método de Elemento Finito (MEF) se analizaron los esfuerzos y deformaciones a los que la estructura está sometida durante la aplicación de los agentes externos de servicio. Los resultados presentados en éste trabajo exhiben una nueva propuesta para la rehabilitación de pacientes con problemas de movilidad en miembro superior. Donde el equipo propuesto permite la rehabilitación del miembro superior apoyado en 4 grados de libertad (tres grados de libertad en el hombro y uno en el codo), el cual es adecuado para realizar terapias activas y pasivas. Asimismo, es un dispositivo que está al alcance de un mayor porcentaje de la población por su bajo costo y fácil desarrollo en la fabricación.

The pace of modern life, both socio-cultural and technologically, has led to an increase of diseases and conditions that affect the physical-motor capabilities of persons. This increase has originated the development of prototypes to help patients to regain mobility and strength of the affected upper limb. This work, deals with the mechanical structure design of an exoskeleton with 4 degrees freedom for upper limb. Which has the capacity to adjust to the Mexican patient anthropometry (arm length, forearm extension, geometry conditions of the back and the patient's height) BLITZ QFD method was applied to establish the conceptual design and loading service conditions on the structure. So, 5 quasi-static cases of study were defined and conditions for patient rehabilitation were subjected. Also by applying the finite element method the structure was analyzed due to service loading. The results presented in this work, show a new method for patient rehabilitation with mobility deficiencies in the upper limb. The proposed new design allows the rehabilitation of the upper limb under 4 degrees of freedom (tree degrees of freedom at shoulder and one at the elbow), which is perfect to perform active and passive therapy. Additionally, it is an equipment of low cost, which can be affordable to almost all the country population.

Proceder de la innovación en la industria farmacéutica. El caso de España / Proceed to the innovation in the pharmaceutical industry. The case of Spain

El presente artículo explora sectores que identifican la innovación en empresas farmacéuticas de España. Para ello se consideran firmas nacionales y filiales extranjeras establecidas en territorio nacional. El análisis realizado comprende el periodo de 2009 al 2011 para una población N=200 empresas afiliadas en ese momento a Farmaindustria y al Plan Profarma. El trabajo consistió en una búsqueda de información útil en las páginas web de las empresas farmacéuticas establecidas en España que pudieran describir de forma estática el perfil innovador del sector farmacéutico español a través del análisis estadístico descriptivo. De esta forma, se crea un cimiento para la documentación de los resultados en una base de datos con el propósito de obtener un panorama con determinación sobre el comportamiento del sector farmacéutico español, así como posibles tendencias. El alto contenido de aportación literaria sobre el sector farmacéutico, se expresa de forma globalizada a nivel nacional e internacional, desestimando datos e información que pudieran ofrecer señales de amenaza u oportunidad respecto al corto periodo de tiempo, ya que a su vez son equiparables a otros años puesto que la industria farmacéutica española se constituye por empresas de origen extranjero (50.5%) y de capital nacional (49.5%). De éstas últimas las pymes son las protagonistas de las pequeñas innovaciones de las firmas establecidas en Madrid y Barcelona principalmente.

This article explores sectors identified innovation in Spanish pharmaceutical companies. It also considers domestic firms and foreign subsidiaries in the country. The analysis covers the period 2009 to 2011 for a population N=200 affiliates at that time Farmaindustria and Plan Profarma. The work involved a search of useful information on the websites of pharmaceutical companies based in Spain statically describes the innovative profile of the Spanish pharmaceutical through descriptive statistical analysis. Thus a foundation for documenting the results in a database in order to get a picture with determination on the behavior of Spanish pharmaceutical sector and possible trends is created. The high content of literary contribution on the pharmaceutical sector is expressed in a globalized national and international level, rejecting data and information that could provide signals threat or opportunity regarding short period time, and which in turn are comparable to other years since the Spanish pharmaceutical industry is constituted by companies of foreign origin (50.5%) and domestic capital (49.5%). Of the latter SMEs are the protagonists of small innovations established in Madrid and Barcelona mainly.

Análisis numérico sobre esfuerzos y áreas de contacto en una PTR Scorpio II® Stryker®. Base para el diseño de PTR personalizada al fenotipo Mexicano / Numerical analysis on stresses and contact areas in a TKR Scorpio II® of Stryker®. Basis to design of customized TKR in accordance to 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.

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.

Análisis numérico de una prótesis endobronquial utilizada para el tratamiento de cáncer pulmonar / Numerical analysis of intrabronchial prosthesis used for the treatment of lung cancer

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.

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.

Aplicación de celda fotoacústica diferencial en la determinación de la permeabilidad de agua en hueso descalcificado / Application of differential photoacoustic cell to determine water permeability in decalcified bone

La espectroscopia mediante celda fotoacústica diferencial (CFD) tiene la capacidad de medir in situ el desarrollo de diversos procesos dinámicos, entre otros la difusión de agua a través de una membrana. Mediante esta técnicase realizó el estudio de permeación de agua en huesos de rata Wistar sanos y descalcificados. Los huesos descalcificados fueron tratados mediante estimulación electromagnética a fin de evaluar la actividad celular en el hueso y, en su caso, detener la descalcificación del mismo. En este trabajo fue posible determinar la viabilidad de la CFD para la evaluación de densidad ósea indirectamente, siendo posible efectuar la evaluación in situ de permeación de agua, así como la cantidad de agua retenida en la estructura ósea al finalizar las pruebas en CFD.

Modelo tridimensional de un fémur humano por medio del método del elemento finito / Tri-dimentional model of a human femur determined by the finite element method

El método del elemento finito nos permite observar la geometría del espécimen, las propiedades mecánicas de los materiales empleados y las condiciones de carga y frontera del modelo. Analizamos el fémur de un individuo masculino sano, de 27 años. Nuestra conclusión es que el fémur trabaja predominantemente en cargas de compresión y secundariamente en flexión.

Efecto del espesor de la capa de cemento en el componente femoral de una prótesis de Charnley: análisis biomécanico mediante el método del elemento finito / Mechanical effects of cement thickness around femoral component in Charnley prosthesis: a biomechanical analysis by the finite element method

Se analizan los esfuerzos y las deformaciones en el componente femoral de una prótesis de Charnley para cadera, cuando se aplican cargas fisiológicas. A partir de radiografías simples se determina la geometría bidimensional del fémur y se analiza su comportamiento cuando son aplicadas cargas que corresponden a la etapa de apoyo medio de la marcha. Se emplea el Método del Elemento Finito, en particular el paquete Ansys versión 5.3 (Ansys, Inc., Houston PA, E.U.A). Durante el Análisis se consideran tres distintos materiales: hueso trabecular, hueso cortical del canal medular y hueso cortical de las zonas medial y lateral del fémur. Posteriormente se elige el tamaño de prótesis adecuado para el hueso estudiado y se inserta en el modelo bidimensional del fémur. De igual forma, se desarrollan seis espesores de capa de cemento, las cuales varían de uno a seis milímetros. Se desea que los esfuerzos para el hueso sean similares que los correspondientes para el caso del fémur intacto, en tanto que los esfuerzos de menor intensidad son los preferidos cuando se trata de los materiales inertes: la prótesis y el cemento. De los espesores de la capa de cemento estudiados, el de tres milímetros presenta los menores esfuerzos para la prótesis y el cemento, en tanto que el hueso trabecular es el que se asemeja en mayor grado al caso del hueso intacto. Para el hueso cortical, los resultados mejores corresponden al espesor de 4 mm. Con base en el presente estudio se recomienda emplear espesores de la capa de cemento de 3 a 4 mm.

Estudio mecánico del fijador interno de columna INO: primera parte: comportamiento bajo en carga cuasi-estática de flexo-compresión / A mechanical study of the spine internal fixator INO: first part: behavior under quasi-static flexoid compression load

Se estudió mecánicamente in vitro el fijador interno de columna INO (Instituto Nacional de Ortopedia) de placas longitudinales y tornillos pediculares, bajo carga cuasi-estática (n = 5) de flexocompresión anterior, para determinar su resistencia a la flexión (N.m), rigidez (N.m/mm) y flexibilidad (mm/N.m). El modelo experimental representó una corpectomía total, utilizándose discos de plástico como cuerpos vertebrales; los tornillos pediculares se fijaron pivotantes (apoyo esférico de las tuercas hacia la placa) a las placas longitudinales. Los ensayos se realizaron en una máquina Instron 4502, aplicando la carga con un brazo de palanca de 39 mm. Los valores medios de resistencia a la flexión, rigidez y flexibilidad obtenidos fueron de 31.184 N.m [de (desviación estándar) = 2.73], 1.205 N.m/mm (de = 0.225) y 0.852 mm/N.m (de = 0.152) respectivamente; la falla observada fue alargamiento y flexión plástica de los cuatro tornillos pediculares. La resistencia a la flexión obtenida para el fijador INO representa el 309.3 por ciento y 53.7 por ciento de la resistencia de los fijadores Rogozinski e Isola, los de menor y mayor resistencia respectivamente, de los doce fijadores estudiados por Cunningham; su rigidez, el 42 por ciento y 17.5 por ciento de la rigidez correspondiente a los fijadores Kirschner e Isola, los de menor y mayor rigidez, y su flexibilidad, el 238.5 por ciento y 572.4 por ciento de la flexibilidad de estos últimos fijadores. Por tanto, el fijador interno INO tiene resistencia a la flexión aceptable pero es más flexible que todos los fijadores estudiados por Cunningham.