Improvement of a trapezo-metacarpal prosthesis by using electron beam melting

The Dr. Ledoux's trapezo-metacarpal implant (Figure 1) was taken as a model in this study. An evolutionary 3D finite element model coupled to an iterative process was developed to simulate the remodeling phenomena of the metacarpal bone by taking into account « the stress shielding » phenomena, as the main factor which lead to a bone lysis damage. The simulation was based on the stimulus concept and the wolf's law, the damage has been investigated as it is due to the high difference of stiffness between Titanium material of the implant and both of cortical and trabecular bones. It was shown that a significant improvement of the lifespan of the metacarpal bone could be obtained with an optimized implant based on an elastic modulus graded material. The method of manufacturing such an implant is the Electron Beam Melting (EBM) which is a rapid additive manufacturing process, implemented by the Arcam machine and available at the Collective Centre of the Belgian Technological Industry (Sirris). Of course the study was a first approach and disregarded completely the contact stresses at the bone prosthesis interface. Additional more advanced optimizations remain necessary to improve the actual results and consequently the lifespan of the orthpaedic implants.