| Περίληψη: | Total Knee Replacement is a surgical procedure that is commonly used to relieve pain and disability in patients with osteoarthritis or severe knee injury. The process involves the resurfacing of the damaged knee joint with metallic and plastic parts in order to restore knee’s natural function and improve the everyday life of patients with osteoarthritis.
A common way to investigate the kinematic and dynamic behavior of prosthetic knee joints, before or after a total knee arthroplasty, is through Finite Element Analysis. The finite element method is most widely applied for solving engineering and mathematical models, and, thus, it is utilized for stress and load estimation in biomechanical problems. In the case of total knee replacement, most studies focus on the investigation of the distribution of stresses and contact forces that are produced especially on the tibial plateau of the implant. These disquisitions aim, principally, at finding the main causes of implant failure or at designing custom–made prostheses.
In this project, a subject–specific total knee replacement finite element model was developed and validated based on personalized data from the Sixth SimTK Grand Challenge dataset. The finite element construction procedure includes the creation of 3D bone geometries by using semi-automatic image segmentation techniques on patient–specific pre–operational CT data. These 3D bone models were, later, aligned with the implant parts of the knee joint by using segmentation software on post–operative CT images. Moreover, 3D processing software was used in order to correct geometry artifacts that would probably pose as an obstacle during the finite element analysis execution.
Furthermore, the development of the finite element model of the implanted knee was performed automatically through Python scripting according to the FEBio FEM format. FEBio was utilized for the realization of finite element analysis of the total knee replacement model. The boundary conditions that were applied on the model were extracted from OpenSim analyses of subject–specific gait trials, which were, also, provided by the Sixth Grand Challenge Competition.
The extracted boundary conditions from patient’s different gait patterns contributed in the validation of the total knee replacement model. The validation was conducted in terms of contact pressures and forces that were produced at the femoral component–tibial insert
interface. More specifically, the observed contact stresses were in accordance with the acceptable values presented in literature, and the estimated contact forces were quite similar to the in vivo contact force measurements given by the Grand Challenge Competition.
Therefore, from the evaluation process it was deduced that the constructed finite element model can accurately simulate the biomechanical behavior of a subject’s instrumented knee. The automatic creation procedure of the model offers the capability of producing various patient–specific prosthetic knees, by simply changing a few parameters. In particular, this model can be generalized, meaning that it can simulate the kinematics and evaluate the dynamics of the implanted knee of different patients and produce valid results. The developed finite element model can be further used in order to design custom–made prosthesis or organize a personalized surgery.
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