Biomechanically informed Virtual Surgical Planning for transfemoral percutaneous implant

Optional to socketed implants, intramedullary percutaneous prosthetics are expected to osteointegrate with the remaining bone, providing enhanced movement, dexterity, and power to the patient. However, retrospective studies have shown secondary problems, such as stress shielding-induced bone loss or stress concentration-induced device failure, which are related to the mechanical properties mismatch. For most of the available implants, current physicians do not have a choice on the implant location, shape, and/or materials. The deployment of this type of implant is based on the surgeon’s experience and X-ray images. We believe that providing biomechanical data will greatly improve the outcome. We have developed a Virtual Surgical Planning (VSP) environment, based on patient images, where the effect of different implant materials, location, and geometry, on the mechanical behavior under biological conditions is assessed. After patient image segmentation, a virtual anatomical model is built to virtually plan the surgery. Once the location of the implant is set, the model can be mechanically evaluated via Finite Element Analysis (FEA). Static studies, considering the maximum force during level walking, have shown better outcomes for less stiff materials such as NiTi, rather than commonly used Ti64. The resulting analysis can inspire future design personalization and deployment in an open surgical procedure. Dynamic modeling will address stress distribution throughout the entire support stage of a level walking cycle. This type of information will allow a better understanding of how stress and deformation are distributed in the implant, detecting potential areas of failure or plasticity concentration. Further work includes evaluation of novel geometries (angulations, gradient diameter), use of porous structures, and multilateral devices.