The project focuses on the functional and structural design of an innovative hip prosthesis (HP), to be realized through additive manufacturing (AM) technology, with the aim of drastically reducing the typical biomechanical issues of this kind of implants. Taking advantage of the AM capability, a conventional titanium bulky HP is redesigned with a trabecular inner region of the stem, in order to reduce its stiffness and overall weight. Stiffness reduction is beneficial for the stress shielding effect: a conventional implant, more rigid than the bone, takes the great part of the loads during everyday movements, leading the bone to adapt to the partial unload reducing its size and strength. Furthermore, weight reduction is expected to mitigate the impact of the HP on the patient perception. Additionally, by means of AM, the roughness of external regions of the HP can be controlled, thus promoting a better osseointegration.
For the new design to be effective with respect to the above mentioned problems, a large amount of material has to be removed from a bulky HP classical design. Consequently, an assessment of the structural integrity of the new AM-HP design becomes crucial. To achieve this, a parametric Finite Element Model of the implant (prosthesis inserted in the host femur bone) is set up to find the best design parameters which maximize the benefits in terms of stress shielding and weight reduction, and guarantee at the same time that the structural limits are not overcome, identifying the critical points stress state. To improve the prediction of the FE model, tests on dedicated samples will be executed to identify elastic and failure limits of the HP materials. Concurrently, measurements on patients will be performed to acquire the actual loads under everyday and critical activities. As a result, a feasible, safe and efficient HP solution will be presented, along with a thorough comparison showing the gains of the new design with respect to a traditional one.
