FEM Modeling of a Stent-Retriever Device

Abstract

Ischaemic stroke remains a leading cause of death and disability worldwide, and mechanical thrombectomy using stent retrievers is the current standard of care for its treatment. Bringing new thrombectomy devices to market, however, relies on costly and time-consuming preclinical and clinical trials that struggle to capture the full variability of patient anatomy and thrombus composition. In-silico clinical trials (ISCTs) offer a way to circumvent these constraints, provided the underlying device models are computationally efficient and demonstrably credible. This thesis, conducted within the T-SIM project, addresses this need by developing and validating a finite element model of the Trevo XP ProVue stent retriever, following the ASME V&V 10/40 framework.

A high-fidelity solid-element (C3D8I) model of the stent geometry was constructed from microscopy measurements and converted into a computationally efficient beam-element (B31) representation. An initial comparison revealed discrepancies of up to 33% in stiffness properties between the two representations, traced to an under-stiffened connector–cell junction in the beam model; introducing an additional beam element at this location reduced the discrepancy to within 1–4%, while reducing the element and node count by more than an order of magnitude. The complete model, including end features and platinum–tungsten braided wires, was then validated against in-vitro flat-plate compression and three-point bending tests. The initial model (Version 1) showed poor agreement with experimental data (NRMSE of 36.0% and 27.0%, respectively); a sensitivity analysis identified strut width and depth as the dominant contributing parameters, motivating refined measurements and a revised model (Version 2), which improved agreement to 16.8% and 22.1% NRMSE. Neither version met the 10% acceptance criterion required under the model's assigned Risk Level 5 classification. Finally, four Context-of-Use simulations comparing the stent with and without the braided wires showed that the wires have negligible influence on radial mechanical behaviour but measurably restrict axial elongation during retraction.

These results show that a computationally efficient beam-element model can reproduce the structural response of a high-fidelity solid model with good accuracy, but that full experimental validation against the required 10% threshold has not yet been achieved, leaving the central research question only partially answered. The findings nonetheless provide a reusable model development pipeline and a provisional simplification rule—omitting braided radiopacity wires for radial-loading applications—that can support the broader device library envisioned within the T-SIM project