Modeling of the condyle elements within a biomechanical knee model

The development of a computational multibody knee model able to capture some of the fundamental properties of the human knee articulation is presented. This desideratum is reached by including the kinetics of the real knee articulation. The research question is whether an accurate modeling of the condyle contact in the knee will lead to reproduction of the complex combination of flexion/extension, abduction/adduction and tibial rotation ob-served in the real knee? The model is composed by two anatomic segments, the tibia and the femur, whose characteristics are functions of the geometric and anatomic properties of the real bones. The biomechanical model characterization is developed under the framework of multibody systems methodologies using Cartesian coordinates. The type of approach used in the proposed knee model is the joint surface contact conditions between ellipsoids, represent-ing the two femoral condyles, and points, representing the tibial plateau and the menisci. These elements are closely fitted to the actual knee geometry. This task is undertaken by con-sidering a parameter optimization process to replicate experimental data published in the lit-erature, namely that by Lafortune and his co-workers in 1992. Then, kinematic data in the form of flexion/extension patterns are imposed on the model corresponding to the stance phase of the human gait. From the results obtained, by performing several computational simulations, it can be observed that the knee model approximates the average secondary mo-tion patterns observed in the literature. Because the literature reports considerable inter-individual differences in the secondary motion patterns, the knee model presented here is also used to check whether it is possible to reproduce the observed differences with reasonable variations of bone shape parameters. This task is accomplished by a parameter study, in which the main variables that define the geometry of condyles are taken into account. It was observed that the data reveal a difference in secondary kinematics of the knee in flexion ver-sus extension. The likely explanation for this fact is the elastic component of the secondary motions created by the combination of joint forces and soft tissue deformations. The proposed knee model is, therefore, used to investigate whether this observed behavior can be explained by reasonable elastic deformations of the points representing the menisci in the model.Fundação para a Ciência e a Tecnologia (FCT) - PROPAFE – Design and Development of a Patello-Femoral Prosthesis (PTDC/EME-PME/67687/2006), DACHOR - Multibody Dynamics and Control of Hybrid Active Orthoses MIT-Pt/BSHHMS/0042/2008, BIOJOINTS - Development of advanced biological joint models for human locomotion biomechanics (PTDC/EME-PME/099764/2008)

Impacto do grau de uveíte em diferentes tipos de úlceras de córneas em cães submetidos ao enxerto pediculado de conjuntiva bulbar - 34 casos

RESUMO O presente trabalho objetivou avaliar os resultados de 34 olhos submetidos ao enxerto conjuntival pediculado (ECP) em ceratites ulcerativas profundas (n=5), em ceratites ulcerativas com colagenólise (n=2), descemetocele (n=7), perfuração corneal (n=15) e prolapso de íris (n=5). Os impactos do grau de uveíte e da integridade da córnea foram correlacionados com presença e ausência de visão por tabelas de contingência. Raças braquicefálicas foram acometidas em 91,11% dos casos. O número de córneas consideradas perfuradas [20/34 (58,82%)] foi maior que o de córneas íntegras [14/34 (41,17%)]. Ao 50º dia de pós-operatório, o número de olhos visuais que apresentavam córneas íntegras previamente às cirurgias (n=13) não diferiu significativamente dos olhos com córneas perfuradas (n=12) (P=0,05). Avaliações relativas ao grau de uveíte, revelaram que a metade dos casos foi considerada severa [17/34 (50%)] e na outra metade as uveítes foram consideradas discretas. Dos 17 casos que apresentaram uveíte severa, oito recuperaram a visão. Já nos 17 olhos onde a uveíte foi considerada leve, 15 mantiveram a visão ao final do período de avaliação. Apesar de a integridade da córnea não se correlacionar com a severidade da uveíte (P=0,48), constatou-se que o número de olhos visuais com uveíte discreta foi significativamente maior que os olhos com uveíte severa (P=0,006). Neste estudo, a taxa geral de sucesso visual após ECP foi de 73,52% e a integridade da córnea não exerceu impacto significativo sobre a manutenção da visão. Todavia, olhos acometidos por uveítes severas apresentaram menor chance de recuperar a visão