A combined FEM-DEM approach: interface stiffening by densification of the periprosthetic bone in cementless joint replacements

Aim and content of the work. In this work, a combined finite discrete element model is to be developed with the simulation software EDEM, which simulates the axial pull-out test of implants. The increase in the initial stability of the implant in the bone through compaction of the surrounding bone with abrasion particles is to be mapped. For this purpose, the results of a previous FEM analysis of the pull-out test are to be combined with a DEM analysis. The interaction of particles and trabeculae (stresses, displacements) is of particular interest. After validation of the model, an outlook is to be given with the help of the simulation results, which parameters could further increase the primary stability and to what extent. Background. Cementless anchorage of implants is gaining importance in total knee arthroplasty, especially in younger and more active patients. The initial strength immediately after implantation (primary stability) is one of the factors leading to the success or failure of the implant. In Germany, loosening of a component is the most common reason for revision of primary total knee arthroplasties1. Loosening can, for example, be caused by insufficient primary stability. In the laboratory, the axial pull-out test is an established procedure for determining primary stability. Results of previous studies showed a high dependence of primary stability on bone density. In addition, the compaction of the bone near the implant by abrasion particles can increase the primary stability2. For a more detailed investigation of primary stability, a test set-up is used in which parameters such as densification can be varied. In the literature, compaction is only insufficiently simulated as a continuum. High-resolution modelling by means of discrete element modelling (DEM) offers the possibility to more precisely describe the interplay of bone density, compaction and primary stability.


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