Bioresorbable Poly (L-Lactic Acid) Flow Diverter Versus Cobalt-Chromium Flow Diverter: In Vitro and In Vivo Analysis

Permanent metallic flow diverter (FD) implantation for treatment of intracranial aneurysms requires antiplatelet therapy for an unclear duration and restricts postprocedural endovascular access. Bioresorbable FDs are being developed as a solution to these issues, but the biological reactions and phenomena induced by bioresorbable FDs have not been compared with those of metallic FDs. We have developed a bioresorbable poly (L-lactic acid) FD (PLLA-FD) and compared it with an FD composed of cobalt-chromium and platinum-tungsten (CoCr-FD). FD mechanical performance and in vitro degradation of the PLLA-FD were evaluated. For in vivo testing in a rabbit aneurysm model, FDs were implanted at the aneurysm site and the abdominal aorta in the PLLA-FD group (n=21) and CoCr-FD group (n=15). Aneurysm occlusion rate, branch patency, and thrombus formation within the FD were evaluated at 3, 6, and 12 months. Local inflammation and neointima structure were also evaluated. Mean strut, porosity, and pore density for the PLLA-FD were 41.7 μm, 60%, and 20 pores per mm , respectively. The proportion of aneurysms exhibiting a neck remnant or complete occlusion did not significantly differ between the groups; however, the complete occlusion rate was significantly higher in the PLLA-FD group (48% versus 13%; =0.0399). Branch occlusion and thrombus formation within the FD were not observed in either group. In the PLLA-FD group, CD68 immunoreactivity was significantly higher, but neointimal thickness decreased over time and did not significantly differ from that of the CoCr-FD at 12 months. Collagen fibers significantly predominated over elastic fibers in the neointima in the PLLA-FD group. The opposite was observed in the CoCr-FD group. The PLLA-FD was as effective as the CoCr-FD in this study and is feasible for aneurysm treatment. No morphological or pathological problems were observed with PLLA-FD over a 1-year period.