Biomechanics of bone transport: in vivo, ex vivo and numerical characterization

The work carried out in this Thesis was motivated by the need of providing experimental data about distraction osteogenesis to improve and validate in silico models of the process. Computational models of distraction osteogenesis allow understanding the mechanobiology and improving the clinical applications of the process. In the last years, numerical models were proposed based on different hypothesis [8, 12, 14–16]. Although experimental studies which evaluated mechanical, biological or both aspects of distraction osteogenesis may be found in literature [1–7, 9–11], the differences existing in the conditions of the experiments carried out make difficult to compare among these studies and to make conclusions. Therefore, more experimental data are demanded to validate computational models and to improve the clinical applications.Premio Extraordinario de Doctorado U

Time-Dependent Collagen Fibered Structure in the Early Distraction Callus: Imaging Characterization and Mathematical Modeling

Collagen is a ubiquitous protein present in regenerating bone tissues that experiences multiple biological phenomena during distraction osteogenesis until the deposition of phosphate crystals. This work combines fluorescence techniques and mathematical modeling to shed light on the mechano-structural processes behind the maturation and accommodation-to-mineralization of the callus tissue. Ovine metatarsal bone calluses were analyzed through confocal images at different stages of the early distraction osteogenesis process, quantifying the fiber orientation distribution and mean intensity as fiber density measure. Likewise, a mathematical model based on the experimental data was defined to micromechanically characterize the apparent stiffening of the tissue within the distracted callus. A reorganization of the fibers around the distraction axis and increased fiber density were found as the bone fragments were gradually separated. Given the degree of significance between the mathematical model and previous in vivo data, reorganization, densification, and bundle maturation phenomena seem to explain the apparent mechanical maturation observed in the tissue theoretically.This work was supported by the Spanish Ministry of Economy, Industry and Competitiveness [Grant No. DPI2017-82501-P]; the Spanish State Research Agency (AEI) [Grant No. PID2020-113790RB-I00/AEI/ 10.13039/501100011033]; and the European Regional Development Fund (FEDER) with the Junta de Andalucı ´a [Grant No. US-1261691]

Multiscale characterisation of cortical bone tissue

Multiscale analysis has become an attractive technique to predict the behaviour of materials whose microstructure strongly changes spatially or among samples, with that microstructure controlling the local constitutive behaviour. This is the case, for example, of most biological tissues-such as bone. Multiscale approaches not only allow, not only to better characterise the local behaviour, but also to predict the field-variable distributions (e.g., strains, stresses) at both scales (macro and micro) simultaneously. However, multiscale analysis usually lacks sufficient experimental feedback to demonstrate its validity. In this paper an experimental and numerical micromechanics analysis is developed with application to cortical bone. Displacement and strain fields are obtained across the microstructure by means of digital image correlation (DIC). The other mechanical variables are computed following the micromechanics theory. Special emphasis is given to the differences found in the different field variables between the micro- and macro-structures, which points out the need for this multiscale approach in cortical bone tissue. The obtained results are used to establish the basis of a multiscale methodology with application to the analysis of bone tissue mechanics at different spatial scales

Diseño de dispositivos para el análisis experimental del proceso de transporte óseo en ovejas

La distracción osteogénica, es una técnica que permite generar nuevo tejido óseo a partir de la separación gradual de dos fragmentos óseos. Aunque se han realizado numerosos estudios experimentales sobre el proceso de distracción, no se ha analizado cuantitativamente la evolución de la rigidez del callo durante el proceso de distracción y posteriormente a él. El objetivo de este trabajo es aplicar técnicas experimentales para caracterizar este proceso mecánicamente y validar modelos numéricos del proceso de distracción y consolidación existentes. Para conocer la rigidez del callo en cada momento, se ha diseñado un dispositivo que permite obtener datos experimentales de las fuerzas que pasan por el callo y distractor in vivo, en unos ensayos de transporte óseo en el hueso metatarsiano de ovejas. El diseño de este experimento ha requerido crear una serie de dispositivos. En primer lugar, se optimizó un distractor tipo Ilizarov y se añadieron sistemas de medida de fuerzas. En segundo lugar, fue necesario diseñar un útil para la correcta colocación del distractor durante la intervención quirúrgica. Finalmente, para poder obtener valores de fuerza en el hueso fue necesario el diseño de un sistema de adquisición de datos que permitiera la medida de fuerzas in vivo.Distraction osteogenesis is a technique to generate new bone tissue from the gradual separation of two bone fragments. Although there are many experimental studies about the distraction process, the evolution of the callus stiffness has not been analyzed quantitatively during the distraction and then it. The aim of this work is to apply experimental techniques to characterize this process mechanically and to validate existing numerical models about distraction and consolidation. To know callus stiffness at any time, a device has been design to obtain force in distractor and callus experimental data in vivo, by means of experiments performed in the metatarsus bone of sheep. The design of this experiment requires creating some devices. First, a Ilizarov distractor was optimized and force transducers were added. Secondly, it was necessary to design a tool that allows a correct installation of distractor during surgery. Finally, in order to obtain force values in the bone, it was necessary to design a data acquisition system which allows the measurement of in vivo forces.Junta de Andalucía P09-TEP-519

Real-Time Wireless Platform for In Vivo Monitoring of Bone Regeneration

For the monitoring of bone regeneration processes, the instrumentation of the fixation is an increasingly common technique to indirectly measure the evolution of bone formation instead of ex vivo measurements or traditional in vivo techniques, such as X-ray or visual review. A versatile instrumented external fixator capable of adapting to multiple bone regeneration processes was designed, as well as a wireless acquisition system for the data collection. The design and implementation of the overall architecture of such a system is described in this work, including the hardware, firmware, and mechanical components. The measurements are conditioned and subsequently sent to a PC via wireless communication to be in vivo displayed and analyzed using a developed real-time monitoring application. Moreover, a model for the in vivo estimation of the bone callus stiffness from collected data was defined. This model was validated in vitro using elastic springs, reporting promising results with respect to previous equipment, with average errors and uncertainties below 6.7% and 14.04%. The devices were also validated in vivo performing a bone lengthening treatment on a sheep metatarsus. The resulting system allowed the in vivo mechanical characterization of the bone callus during experimentation, providing a low-cost, simple, and highly reliable solution.Junta de Andalucía US-1261691Ministerio de Economía y Competitividad DPI2017-82501-PMinisterio de Economía y Competitividad PGC2018-097257-B-C3

Comparison of the volumetric composition of lamellar bone and the woven bone of calluses

Woven tissue is mainly present in the bone callus, formed very rapidly either after a fracture or in distraction processes. This high formation speed is probably responsible for its disorganized microstructure and this, in turn, for its low stiffness. Nonetheless, the singular volumetric composition of this tissue may also play a key role in its mechanical properties. The volumetric composition of woven tissue extracted from the bone transport callus of sheep was investigated and compared with that of the lamellar tissue extracted from the cortical shell of the same bone. Significant differences were found in the mineral and water contents, but they can be due to the different ages of both tissues, which affects the mineral/water ratio. However, the content in organic phase remains more or less constant throughout the mineralization process and has proven to be a good variable to measure the different composition of both tissues, being that content significantly higher in woven tissue. This may be linked to the abnormally high concentration of osteocytes in this tissue, which is likely a consequence of the more abundant presence of osteoblasts secreting osteoid and burying other osteoblasts, which then differentiate into osteocytes. This would explain the high formation rate of woven tissue, useful to recover the short-term stability of the bone. Nonetheless, the more abundant presence of organic phase prevents the woven tissue from reaching a stiffness similar to that of lamellar tissue in the long term, when it is fully mineralized

Evolution of relaxation properties of callus tissue during bone transport

Callus tissue exhibits a viscoelastic behavior that has a strong influence on the distribution of stresses and their evolution with time and, thus, it can affect tissue differentiation during distraction procedures. For this reason, a deep knowledge of that viscoelastic behavior can be very useful to improve current protocols of bone distraction and bone transport. Monitoring stress relaxation of the callus during distraction osteogenesis allows characterizing its viscoelastic behavior. Different procedures have been used in the literature to fit the response of a given viscoelastic model to the force relaxation curve. However, these procedures do not ensure the uniqueness of that fit, which is of the utmost importance for statistical purposes. This work uses a fitting procedure already validated for other tissues that ensures that uniqueness. Very importantly too, the procedure presented here allows obtaining more information from the stress relaxation tests, distinguishing relaxation in different time scales, which provides a deeper insight into the viscoelastic behavior and its evolution over time. As it was observed in the results, relaxation is faster at the first days after osteotomy and becomes slower and more gradual with time. This fact can be directly linked to the temporal evolution of the callus composition (water, organic phase, and mineral content) and also to the progression of tissue differentiation, with a prevalence of hard tissues as time passes

Dispositivo de control de flujo de sangre en un vaso sanguíneo

Dispositivo de control de flujo de sangre en un vaso sanguíneo. La invención describe un dispositivo (1) de control de flujo de sangre en un vaso sanguíneo que comprende una cadena (2) formada por eslabones donde el ángulo máximo de giro entre cada par de eslabones está limitado, donde la cadena (2) tiene una porción proximal (2p) dotada de un lazo (3) configurado para rodear el vaso sanguíneo con el propósito de comprimirlo y una porción distal (2d) configurada para cerrar el lazo (3) mediante la aplicación de tracción.Españ

Kwapa: Gente del río. Estrategias transmedia de impacto social

El PAP Alter Código, período Primavera 2023, trabajó con los dos proyectos que se han venido trabajando en semestres anteriores: el videojuego A Orillas del río y el documental Déjennos pescar. Ambos proyectos parten de la metodología interdisciplinaria y colaborativa con miembros de la comunidad Cucapá para crear representaciones audiovisuales no estigmatizantes, que detonen el sentido de comunidad y refuercen su acervo cultural. El videojuego A Orillas del río es del género point and click, de vista isométrica, el cual está inspirado en el cuento oral tradicional El zorro y el coyote, que busca ser una herramienta lúdica de aprendizaje para reforzar el aprendizaje de la lengua Cucapá en los niños. Los resultados obtenidos fueron el demo del nivel uno (escenas uno y dos); colorimetría, arcos de personajes principales; programación de minijuegos. Dentro del documental ‘Déjennos pescar’ los resultados fueron un montaje, una clasificación del material grabado con transcripciones de audio, mientras que en la parte de estrategia de impacto se creó un manual de uso de redes sociales con colorimetría, tipografía, estilo de voz, tipo de contenido según la red social, para los futuros integrantes del equipo.ITESO, A.C