Final Report Summary - TOTAL.KNEE (Development of a new generation of knee prostheses with enhanced lifespan features using advanced computational biomechanics)
WP-1 Project Management
WP-2 To perform a survey of already existing models of prostheses and their inherent problems
WP-3 To model and to analyse different geometries of the prostheses stems to evaluate the stresses levels, searching for a reduction of these stresses and for an increase of the fixation degree.
WP-4 To generate several geometries for the surfaces of prosthesis in order to reduce the degree of wear between the prosthesis components
WP-5 To generate, model and analyse several geometries of the tibial tray in order to evaluate the potential risk of mechanical failure.
WP-6 To evaluate the coupling bone-prosthesis in light of the previous results, by combining some selected geometries obtained in the precedent WP´s
WP-7 To carry out a Dissemination Plan to ensure the proper dissemination of the outcomes
WORK PERFORMED AND RESULTS
The goals of the project have been achieved successfully.
A survey of the most common used implants was done. Several brands were analyzed. A comparative analysis based in the finite element method was done, by defining several combinations of stem lengths, stem diameters and stem inclinations. All these geometries were discretized using refined finite element meshes. Sensitivity analyses of all the FE meshes were also done. The generation of surfaces in both the tibial plate and the femoral component is still under development. A comparative analysis based in the finite element method was done, by defining several combinations of the attaching pegs in the femoral component of the implant. All these geometries were discretized using refined finite element meshes. Sensitivity analyses of all the FE meshes were also done. Analysis of the wear generated in the tibial surfaces was also done and the mechanical stresses were estimated.
Some additional (unexpected) outcomes have been obtained during the project.
The first one is related to the efficient integration of the stiffness matrix of n-noded high-order hexahedral finite elements by taking advantage of some mathematical relations among the nine terms of the matrix, previously found for the more simple brick element.
The second one dealt with the reconstruction of geometries from CT’s and MRI’s. An efficient and integrated methodology to accomplish this task was proposed and successfully used. The methodology is based on image-processing algorithms chosen according to some characteristics of the tissue. First, low-quality images are improved by using enhancement algorithms to reduce image noise and to increase structures contrast. Then, hybrid segmentation for tissue identification is applied through a multi-stage approach
The third one dealt with the implementation of the developed methodology into a virtual platform to represent the human body and implants (called BodyGiD), which is being developed at the host center.
The fourth one was obtained when carrying out a numerical-experimental study of the cell behavior, oriented towards possible new strategies for bone remodeling. A new approach based on a cellular-automata scheme was developed and published.
The research has impact on the scientific knowledge and understanding of the complex processes existing around the osseointegration and fixation of implants. The results obtained have demonstrated that severe inclinations in varus lead to high concentration of stresses under the tibial plate, thus leading to big zones of bone resorption risk. Also several geometries were studied by varying the attaching pegs of the femoral component, leading to a better knowledge of the stresses distribution along the femur and close to the implant region.
At the moment of this report, no commercial impact is available. However, it is expected that the designs coming from this project would have better performance and improved lifespan, then leading to a marketable prototypes and products. From the social point of view the project also will give significant impact. The better the implants, the longer their lifespan and the less the money spent. Other clear impact of the project is the increase in the awareness among physicians that engineering simulation and computer modeling is of great relevance to model and to predict the evolution of bone modified by the presence of implants.