Finite Element Analysis for the Virtual Surgical Planning of Stiffness-matched Personalized Load-bearing Percutaneous Implants

Abstract

Osseointegrated, percutaneous intramedullary abutments provide a new opportunity to increase freedom of movement, dexterity, and power of prosthetic upper and lower extremities. Device deployment is based on the physician’s experience and judgment as no biomechanical information is available or choice of implant location, shape, and materials. Furthermore, there is little opportunity for personalization to improve performance and reduce the risk of stress shielding-induced bone loss or stress concentration-induced device failure. We present a Virtual Surgical Planning (VSP) environment for assessing the expected mechanical outcome of physician choice in the placement site of a percutaneous implant. Starting from de-identified patient images, a virtual anatomical model is created to emulate the surgical implantation procedure. After digitally implanting the intramedullary component-abutment system, the mechanical performance is computationally evaluated via Finite Element Analysis (FEA) under representative in vivo static loading conditions. Our computational analysis includes two different materials for the implant: medical-grade Surgical Grade 5 Titanium alloy (Ti-6Al-4V) and super-elastic Nickel-Titanium (NiTi). The resulting analysis can inspire future design personalization and deployment in an open surgical procedure. Our VSP approach would allow interactive assessment of device location, materials, and performance to alter the normal stress-strain distribution in the bone, potentially avoiding stress shielding and device failure. Future stiffness-matching strategies (e.g., incorporation of internal porosity, new materials, or novel implant geometry), and their effect on implant strength could be evaluated in our computational model.