Virtual Surgical Planning for Osseointegrated Transfemoral Percutaneousimplants

In transfemoral bone amputation cases, after trauma or disease, osseointegrated (OI) percutaneous prosthetic mounts offer improved freedom of movement and comfort over socketed implants. However, current device design and deployment do not consider the effect of the implant’s design, material, fastening method, or location on its mechanical performance or the sustainability of these OI devices. Physicians select and position an implant based on their experience. They have no personalized biomechanical information available at the Point-of-Care (PoC). Access to the simulated performance of the implant and prosthetic could, potentially, decrease the risk of bone loss due to stress shielding and device failure due to stress concentration. Here, we present a Virtual Surgical Planning (VSP) environment, for personalizing the shape, material, and location of a lower limb OI percutaneous prosthetic limb mount implant. The VSP starts with a patient image to create a digital model, for surgical planning and emulation. Next, the bone-implant construct is mechanically evaluated via Finite Element Analysis (FEA). The example analysis compares the use of medical-grade Surgical Titanium (Ti-6Al-4V) alloy and super-elastic Nickel-Titanium (NiTi).

Furthermore, the bones’ normal stress-strain pattern alteration due to the implant’s geometry, material, and location can be addressed. A stiffer implant (Ti64) was seen to localize stress transferring to the bone while using more elastic materials (NiTi), which promote widespread load transfer and bone deformation. This could be protective against bone tissue resorption. The screwed fastening method showed proximally localized loading which could lead to aseptic OI device loosening. The resulting analysis can be used for future design personalization and deployment in an open surgical procedure. Furthermore, recent (i.e., in progress) work compares future stiffness-matching strategies (e.g., incorporation of internal porosity, new materials, or novel implant geometry), their effect on the implant strength, and the validation of our computational model.