Stent Size Optimization in the Femoral Bifurcation Using a Fractal Model: A Morphological Analysis

Stenting of common femoral artery (CFA) bifurcation lesions is complex due to harmonious asymmetric geometry between the CFA and deep or superficial femoral artery. In order to ensure an optimal flow, the stents must be implanted according to the diameter of the CFA and the diameter of the daughter vessels. The aim of this study was to validate a mathematical formula for the CFA bifurcation in order to optimize the implantation of stents in this bifurcation with a fast and efficient method.

We retrospectively included all patients who underwent transcatheter aortic valve implantation and who had a healthy CFA bifurcation on the CT-scan. Diameters of the mother vessel (D_m), daughter vessels (D_l: larger vessel; D_s: smaller vessel), and the ratio between the two were calculated. According to the latter, the following linear model was proposed: [D_m = (D_m/D_l + D_s) × (D_l + D_s)] and was compared to the four existing models (Murray, HK, Flow, Finet). Finally, we calculated the relative error between the prediction of the four models and the measurements.

Overall, 110 CFA bifurcations were included. Mean CFA diameter was 7.75 ± 1.67 mm. Mean D_l diameter was 5.79 ± 1.21 mm and mean D_s diameter was 5.23 ± 1.09 mm. A reduction of 25 % was seen between the CFA and the larger daughter-vessel. The mean ratio between the CFA and the daughter vessels was 0.71. Our model [D_m = 0.71× (D_l + D_s)] and the flow law were the most accurate (relative difference of 1.59 ± 11.97% and 1.01 ± 11.94%, respectively). However, Murray's law had a statistically significant deviation from the real mother-vessel diameter (P < 0.001).

We developed a simple fractal ratio between CFA and daughter vessels, which could be easily used in daily practice during CFA percutaneous reconstruction to identify the optimal diameters of the diseased vessels.