Finite element analysis of an implanted human tibia under normal gait loading

In the present work a model for the mechanical response of a human tibia under normal gait conditions is formulated and its results are compared with the values corresponding to a tibia after Total Knee Reconstruction (TKR).; A structurally accurate solid model of a human tibia is developed from a Computed Tomography scan of a cadaveric human tibia. A procedure of obtaining solid models suitable for Finite Element (FE) analyses based on Computed Tomography data is shown.; The aim of this study is to better assess the stresses induced in a bone by the presence of an implant under physiologically normal loads and also to gain insight into failure risks. As part of the load supported by a healthy bone is transferred to the implant, the bone structure adapts to the new lower load following Wolff's Law—adaptation to stimuli. The phenomenon is called stress shielding. The stress shielding effects induced in the tibia due to the presence of a knee implant are estimated. The solid model used for the tibia with an implant is based on an actual knee implant model: a fixed bearing stemmed metal backed NexGen model provided by Zimmer, Inc.; Two FE meshes, a tetrahedral and a hexahedral mesh, are generated, in part, to validate the results and to determine their robustness. Analyses of the models, under normal gait conditions, are performed in ABAQUS. As bone functions at or near to its ultimate properties it is safer to consider the orthotropic model predictions, as the isotropic model results could be exceeding the bone's ultimate properties. The FE analyses of the tibia with an implant model the bone-implant contact environment. Free sliding and frictional contact models are analyzed and compared. The bone-implant interfacial stresses and relative displacements are estimated and compared with the existing literature results.; The contributions of this study have been: (1) To develop and validate a detailed FE model for the human tibia, including cortical and cancellous bone zones and bone marrow; (2) To establish procedures for generating a finite element mesh starting with a CT scan, (3) To extend the model to incorporate a realistic orthopaedic implant; (4) To assess effects of articulation of the implant on bone; (5) To predict the stresses in the vicinity of the implant, to assess the stress shielding effects induced by the implant presence.