| Περίληψη: | During the last couple of years, computational modeling and simulation have become an important field of research in biomedical sciences, with implications in our ability to efficiently analyze human body functionality. Among others, the knee joint constitutes a big and very much complicated joint in human body. Evidently, the significant increase in the number of knee replacements and surgical operations that have been reported over the last years makes our understanding of the mechanical and anatomical functionality of the knee more than critical.
This thesis studies the stress-strain of four ligaments (ACL, LCL, MCL, LCL), of two menisci (lateral, medial) and of two bone cartilages (femur, tibia) for a gait stance cycle motion in an effort to refine and study the knee’s components behavior. In doing so, we have developed two Models (A, B) with different kinematics constrain. We assumed that in Model A the tibia bone is fixed in all dimensions (based on the assumptions in literature), whereas in Model B the tibia is fixed in all dimension except the flexion-extension. For these two Models, we simulated five Cases which were considered based on the kinematics-prescribed motions, and applied them in the finite element knee model. For these prescribed DOFs the flexion-extension of both Models (A, B) is taken as the output of multibody musculoskeletal software OpenSim. The internal-external and valgus-varus prescribed rotationals DOFs are taken from OpenSim too, but modified based on [21], in order to obtain more consistent results of the knee geometry. We applied the two translational DOFs in accordance with the results of [21]. An open-source software was developed, in order to handle the kinematics and kinetic output of OpenSim software and apply as prescribed motions or forces input in finite element analysis (FEBio).
The results concludes in three studies. The first study presents the differences of ligaments’ stresses behavior between Case Three - Case Four and between the Case Four - Case Five in both Models (A, B). The second study presents the differences of stresses behavior of ligaments in Case Three, Four and Five between the Model A and Model B. Finally, in third study, a ligaments’ stresses profile during the gait stance cycle is determined for both Models (A, B).
In the end of this thesis, a brief study of knee’s total, lateral and medial meniscectomy in gait stance cycle is presented. In these models, the three rotational (flexion-extension, internal-external, valgus-varus) and two translational (anterior-posterior and lateral-medial) at femur bone were set as prescribed DOFs, and the distal-proximal DOF was set to be unconstraint. The tibia set was fixed in all dimensions.
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