Moment arms are important in many contexts. Various methods have been used to estimate moment arms. It has been shown that a moment arm changes as a function of joint angle and contraction state. However, besides the influence of these anatomical factors, results from recent studies suggest that the estimation of moment arm is also dependent on the methods employed. The overall goal of this thesis was to explore the interaction between the methodological and anatomical influences on moment arm and their effect on estimates of muscle-tendon forces during biomechanical modelling. The first experiment was a direct comparison between two different moment arm methods that have been previously used for the estimation of Achilles tendon moment arm. The results of this experiment revealed a significant difference in Achilles tendon moment arm length dependent on the moment arm method employed. However, besides the differences found, results from both methods were well correlated. Based on these results, methodological differences between these two methods were compared across different joint angles and contraction states in study two. Results of experiment two revealed that Achilles tendon moment arms obtained using both methods change in a similar way as a function of joint angle and contraction state. In the third experiment, results from the first two experiments were used to determine how methodological and anatomical influences on Achilles tendon moment arm would change muscle-tendon forces during the task of submaximal cycling. Results of the third experiment showed the importance of taking the method, ankle angle and contraction state dependence of Achilles tendon moment arm into account when using biomechanical modelling techniques. Together, these findings emphasis the importance of carefully considering methodological and anatomical modifiers when estimating Achilles tendon moment arm.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

This thesis focuses on the problem of determining appropriate skeletal configurations for which a virtual animated character moves to desired positions as smoothly, rapidly, and as accurately as possible. During the last decades, several methods and techniques, sophisticated or heuristic, have been presented to produce smooth and natural solutions to the Inverse Kinematics (IK) problem. However, many of the currently available methods suffer from high computational cost and production of unrealistic poses. In this study, a novel heuristic method, called Forward And Backward Reaching Inverse Kinematics (FABRIK), is proposed, which returnsvisually natural poses in real-time, equally comparable with highly sophisticated approaches. It is capable of supporting constraints for most of the known joint types and it can be extended to solve problems with multiple end effectors, multiple targets and closed loops. FABRIK wascompared against the most popular IK approaches and evaluated in terms of its robustness and performance limitations. This thesis also includes a robust methodology for marker prediction under multiple marker occlusion for extended time periods, in order to drive real-time centre of rotation (CoR) estimations. Inferred information from neighbouring markers has been utilised, assuming that the inter-marker distances remain constant over time. This is the firsttime where the useful information about the missing markers positions which are partially visible to a single camera is deployed. Experiments demonstrate that the proposed methodology can effectively track the occluded markers with high accuracy, even if the occlusion persists for extended periods of time, recovering in real-time good estimates of the true joint positions. In addition, the predicted positions of the joints were further improved by employing FABRIK to relocate their positions and ensure a fixed bone length over time. Our methodology is tested against some of the most popular methods for marker prediction and the results confirm that our approach outperforms these methods in estimating both marker and CoR positions. Finally, an efficient model for real-time hand tracking and reconstruction that requires a minimumnumber of available markers, one on each finger, is presented. The proposed hand modelis highly constrained with joint rotational and orientational constraints, restricting the fingers and palm movements to an appropriate feasible set. FABRIK is then incorporated to estimate the remaining joint positions and to fit them to the hand model. Physiological constraints, such as inertia, abduction, flexion etc, are also incorporated to correct the final hand posture. A mesh deformation algorithm is then applied to visualise the movements of the underlying hand skeleton for comparison with the true hand poses. The mathematical framework used for describing and implementing the techniques discussed within this thesis is Conformal GeometricAlgebra (CGA).

[ES] En esta Tesis Doctoral se plantea un nuevo modelado biomecánico del cuello para su aplicación en los campos de la valoración funcional y la ergonomía. Se ha realizado un estudio cinemático para describir los axoides asociados a los ejes instantáneos de rotación (EIR) del movimiento de la cabeza respecto del tórax, así como las variables cinemáticas (posiciones, velocidades y aceleraciones), que se describen como funciones continuas mediante técnicas de Análisis de Datos Funcionales (FDA). Se han analizado movimientos cíclicos continuos. El movimiento más reproducible es el de flexo-extensión. Para el análisis dinámico, se ha elaborado un modelo articular de dinámica inversa, que permite estimar las fuerzas, momentos a nivel de C7 y potencia desarrollada, a partir de la cinemática del movimiento y de las características inerciales del sistema cuello-cabeza, obtenidas a partir de estudios previos y ajustadas mediante un procedimiento de calibración. El modelo ha sido validado experimentalmente y se ha cuantificado su fiabilidad, que resulta suficiente para aplicaciones clínicas. Se han estudiado una muestra de sujetos sanos (n=45) con la finalidad de obtener una base de normalidad, analizar el efecto de características individuales (edad, sexo y características antropométricas), y una muestra de pacientes con dolor inespecífico de cuello (n=24), para analizar las diferencias asociados a la patología. Este es el primer estudio en el que se obtiene una representación continua del EIR y se realiza una descripción de la cinemática y dinámica usando funciones continuas mediante técnicas estadísticas de FDA. Los resultados muestran que los patrones cinemáticos y dinámicos están influidos por el sexo y por la longitud del cuello. Las mujeres presentan más movilidad que los hombres y una mayor longitud del cuello va asociada a movimientos más lentos. El efecto de la edad no es demasiado acusado en la muestra analizada, con edades inferiores a 50 años en la mayoría de casos. Las diferencias cinemáticas entre personas sanas y con dolor de cuello son muy claras, siendo mayores en las variables de posición y de aceleración que en los rangos, por lo que son éstas variables más adecuadas para definir protocolos de valoración biomecánica clínica. Desde el punto de vista dinámico, hay diferencias muy claras en las fuerzas y en la potencia desarrollada, aunque no tanto en el momento articular. Las diferencias en las variables funcionales son mucho más evidentes que en las correspondientes variables numéricas extraídas de éstas (rangos, valores máximos y mínimos). En definitiva, se demuestra que el registro de movimientos continuo y el uso conjunto de información cinemática y dinámica ofrece una visión más completa de los patrones biomecánicos de movimiento del cuello y puede mejorar los actuales sistemas de valoración funcional. / [CA] En aquesta tesi doctoral es planteja un nou modelatge biomecànic de el coll per la seva aplicació en els camps de la valoració funcional i l'ergonomia. S'ha realitzat un estudi cinemàtic per descriure els axoides associats als eixos instantanis de rotació (EIR) de el moviment del cap respecte de tòrax, així com les variables cinemàtiques (posicions, velocitats i acceleracions), que es descriuen com a funcions contínues mitjançant tècniques d'Anàlisi de Dades Funcionals (FDA). S'han analitzat moviments cíclics continus. El moviment més reproduïble és el de flexo-extensió. Per a l'anàlisi dinàmic, s'ha elaborat un model articular de dinàmica inversa, que permet estimar les forces, moments a nivell de C7 i potència desenvolupada, a partir de la cinemàtica de el moviment i de les característiques inercials de sistema coll-cap, obtingudes a partir d'estudis previs i ajustades mitjançant un procediment de calibratge. El model ha estat validat experimentalment i s'ha quantificat la seva fiabilitat, que resulta suficient per a aplicacions clíniques. S'han estudiat una mostra de subjectes sans (n = 45) amb la finalitat d'obtenir una base de normalitat, analitzar l'efecte de característiques individuals (edat, sexe i característiques antropomètriques), i una mostra de pacients amb dolor inespecífic de coll (n = 24), per analitzar les diferències associats a la patologia. Aquest és el primer estudi en el qual s'obté una representació contínua de l'AIR i es realitza una descripció de la cinemàtica i dinàmica usant funcions contínues mitjançant tècniques estadístiques de FDA. Els resultats mostren que els patrons cinemàtics i dinàmics estan influïts pel sexe i per la longitud de coll. Les dones presenten més mobilitat que els homes i una major longitud de coll va associada a moviments més lents. L'efecte de l'edat no és massa acusat en la mostra analitzada, amb edats inferiors a 50 anys en la majoria de casos. Les diferències cinemàtiques entre persones sanes i amb mal de coll són molt clares, sent majors en les variables de posició i d'acceleració que en els rangs, de manera que són aquestes variables més adequades per definir protocols de valoració biomecànica clínica. Des del punt de vista dinàmic, hi ha diferències molt clares en les forces i en la potència desenvolupada, encara que no tant en el moment articular. Les diferències en les variables funcionals són molt més evidents que en les corresponents variables numèriques extretes d'aquestes (rangs, valors màxims i mínims). En definitiva, es demostra que el registre de moviments continu i l'ús conjunt d'informació cinemàtica i dinàmica ofereix una visió més completa dels patrons biomecànics de moviment de coll i pot millorar els actuals sistemes de valoració funcional. / [EN] In this Doctoral Thesis, a new biomechanical modeling of the neck is proposed for its application in the fields of functional assessment and ergonomics. A kinematic study has been carried out to describe the axoids associated with the instantaneous axes of rotation (EIR) of the movement of the head with respect to the thorax, as well as the kinematic variables (positions, velocities and accelerations), which are described as continuous functions using techniques of Functional Data Analysis (FDA). Continuous cyclical movements have been analyzed. The most reproducible movement is flexion-extension. For the dynamic analysis, a joint model of inverse dynamics has been developed, which allows estimating the forces, moments at the C7 level and developed power, from the kinematics of the movement and the inertial characteristics of the neck-head system, obtained from starting from previous studies and adjusted by means of a calibration procedure. The model has been experimentally validated and its reliability has been quantified, which is sufficient for clinical applications. A sample of healthy subjects (n = 45) were studied in order to obtain a normality base, analyze the effect of individual characteristics (age, sex and anthropometric characteristics), and a sample of patients with nonspecific neck pain (n = 24), to analyze the differences associated with the pathology. This is the first study in which a continuous representation of the EIR is obtained and a description of the kinematics and dynamics is made using continuous functions using FDA statistical techniques. The results show that the kinematic and dynamic patterns are influenced by gender and neck length. Women are more mobile than men and longer neck length is associated with slower movements. The effect of age is not too pronounced in the analyzed sample, with ages less than 50 years in most cases. The kinematic differences between healthy people and those with neck pain are very clear, being greater in the position and acceleration variables than in the ranges, making these variables more suitable for defining clinical biomechanical assessment protocols. From the dynamic point of view, there are very clear differences in the forces and the power developed, although not so much in the articulation moment. The differences in the functional variables are much more evident than in the corresponding numerical variables extracted from them (ranges, maximum and minimum values). In short, it has been shown that continuous movement recording and the joint use of kinematic and dynamic information offers a more complete view of the biomechanical patterns of neck movement and can improve current functional assessment systems. / Este trabajo ha sido desarrollado en el Instituto Universitario de Ingeniería Mecánica y Biomecánica de la Universitat Politècnica de València, y ha sido financiado con el proyecto de investigación Junior PIJ-15-08 de la Escuela Politécnica Nacional de Quito-Ecuador. / Venegas Toro, WR. (2021). Modelado biomecánico del cuello basado en la imagen cinemática de la función articular para su aplicación en tecnologías para la salud y el bienestar del ser humano [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/174522

La révision d’arthroplastie de la hanche en cas d’important déficit osseux acétabulaire peut être difficile. Les reconstructions avec cupule de très grand diamètre ou cupule « jumbo » (≥ 62 mm chez la femme et ≥ 66 mm chez l’homme) sont une option thérapeutique. Nous voulions évaluer la préservation et la restauration du centre de rotation de la hanche reconstruite en la comparant au coté controlatéral sain ou selon les critères de Pierchon et al. Nous voulions également évaluer la stabilité du montage à un suivi d’au moins 2 ans. Il s’agissait de 53 cas consécutifs de révision acétabulaire pour descellement non septique avec implantation d’une cupule jumbo sans ciment à l’Hôpital Maisonneuve-Rosemont. Le déficit osseux évalué selon la classification de Paprosky et al. Les cupules implantées avaient un diamètre moyen de 66 mm (62-81) chez les femmes et 68 mm (66-75) chez les hommes. L’allogreffe osseuse morcelée et massive était utilisée dans 34 et dans 14 cas respectivement. La cupule a été positionnée avec un angle d’inclinaison moyen de 41.3° (26.0-53.0). Le centre de rotation de la hanche reconstruite a été jugé satisfaisant dans 78% de cas sur l'axe médiolatéral, 71% sur l'axe craniopodal et amélioré dans 27% dans cet axe. Au recul moyen radiologique de 84.0 mois (24.0-236.4) et clinique de 91.8 mois (24.0 – 241.8): 6 cas étaient décédés, 3 perdus au suivi. On a observé le descellement radiologique dans un 1 cas, la luxation récidivante dans 5 cas et l’infection dans 4 cas. Le retrait de la cupule a été effectué dans 2 cas pour infection. L’ostéointégration des greffons osseux était complète dans tous les cas sauf 3. Les scores cliniques étaient pour le HHS de 82 +/-17, le WOMAC de 86 +/- 14 et le SF-12 physique de 46 +/- 12 et mental 53 +/-13. La cupule jumbo peut être considérée comme un moyen fiable pour gérer le déficit osseux dans les révisions acétabulaires. Elle permet de conserver ou d’améliorer la position du centre de rotation physiologique de la hanche. La fixation sans ciment favorise l’ostéointégration de la cupule et permet une stabilité à moyen terme. Le taux de complications est comparable ou inférieur à d'autres procédures de reconstruction. / Acetabular implant revision with large bone defects, can be challenging. One of the reconstruction options is a large outer diameter cup or “jumbo cup” (≥62 mm in women and ≥66 mm in men). We hypothesized that cementless jumbo cups is a reliable technique to preserve or reconstruct hip center of rotation. We also evaluated stability at least 2 two years follow up. Fifty-three consecutive non septic loosening acetabular arthroplasty revisions at Hopital Maisonneuve-Rosemont where a cementless jumbo cup was used were assessed. Bone defect was evaluated according to Paprosky classification. Mean implanted component size was 66 mm (62-81) in women and 68 mm (66-75) in men. Cancelous bone chips allograft was used in 34 cases and bulk bone allograft in 14. Immediate postoperative AP view showed a mean abduction cup angle of 41.3° (26.0-53.0). Hip centre were found at satisfy position in 78% on mediolateral axis, in 71% on craniopodal axis and it was improved in 27% in this late axis. At the mean follow up of 84.0 months (24.0-236.4) radiologically and 91.8 months (24.0-241.8) clinically: 6 patients were died and 3 were lost of follow up. Complications were: dislocation in 5 cases (4 revisions with constrained liner), infection in 4 cases (2 treated conservatively and 2 revised in 2 times procedure) and radiographic loosening in 1 case. Bone graft integration was completed in all except in 3 cases. Clinically, the mean HHS was 82% +/- 17, WOMAC 86 +/- 14, physical SF-12 46 +/- 12 and mentally SF-12 53 +/- 13. Jumbo cups appear as a reliable procedure to manage bone loss in acetabular revision. It allows conservation or improvement of physiologic hip center. Also, cementless fixation promote bone integration. with subsequent cup stabilitity. The complication rate is comparable or may be less than others reconstruction procedures .

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