From crash test to the operating room: optimization of stent-graft design using numerical simulation

Background: Numerical simulation (NS) is a computer-based procedure to simulate and demonstrate mechanical interactions between bodies. It is well known and has been used in the automotive and aerospace industries for years. The method of NS is also used in the field of endovascular surgery to predict the behavior of stent-grafts in vessels and to plan complex custom-made prostheses. Objective: The current planning and manufacture of fenestrated prostheses for complex aortic aneurysms is a time, human resources and material intensive process, which for most manufacturers takes weeks to months. The positioning of fenestrations should be as accurate as possible to enable a successful and complication-free implantation. A precise prediction of graft deployment and alignment within the patient's aorta has so far only been possible to a certain extent in models. Methods: Numerical simulation using finite element analysis now enables this prediction. The mechanical properties of the stent-graft and the aorta can be implemented and graft deployment can be simulated and graphically shown in a patient-specific aorta. In this way, the optimal dimensions of the prosthesis can be determined and the fenestrations can be exactly positioned. The computed tomography (CT) angiography of the complete aorta in 1 mm thick slices serves as input data. Based on the CT data a digital twin of the aorta is simulated and presented 3-dimensionally. In this hollow model the prosthesis, which is not yet fenestrated, is digitally implanted and in the next step the positions of the fenestrations are then determined based on the ostia of the visceral arteries. Results: The results of a prospective multicenter study showed that planning fenestrated grafts using NS is accurate and time saving compared to the conventional planning process. Moreover, a user-friendly online platform has already been developed, which in the future will enable a complex custom-made graft planning within 24 h. The 3-dimensional depiction of the unfolded prosthesis can be assessed in all directions and possible problems can be predicted and therefore rectified. Discussion: The development of digital planning of a prosthesis and prediction of the unfolding of a stent-graft within the patient's aorta is an important step towards a contemporary, fast and safe treatment of patients with complex aortic aneurysms.