The Impact of Knee Bending on the Superficial Femoral Artery and Popliteal Artery Morphology Before and After Endovascular Repair of Popliteal Aneurysm

Objective: The aim of this study is to evaluate the deformations of the femoropopliteal (FP) arterial segment due to knee flexion in patients suffering from popliteal aneurysm before and after endovascular treatment (ET). Design and methods: Nine patients were prospectively evaluated. Pre-operative and post-operative computed tomography angiography (CTA) scans were performed on the leg of each patient in both a flexed and extended knee position. The images were employed to reconstruct the FP segment through segmentation and the resulting models were subsequently used to calculate the average diameter, length, and tortuosity of both the superficial femoral artery (SFA) and popliteal artery (PA). Furthermore, the overall PA tortuosity was decomposed into 2 components, ie, antero-posterior and lateral direction. Results: Following knee flexion, both arterial segments experienced shortening in the pre-operative and post-operative phases. Specifically, the SFA was shortened by 3.5% in pre (p<0.001) and 1.21% in post-stenting (p<0.001), while the PA was shortened by 4.8% (p<0.001) and 5.63% (p<0.001), respectively. Tortuosity significantly increased in all considered segments; in particular, in SFA there was a pre-intervention increase of 85.2% (p=0.002) and an increase of 100% post-intervention (p=0.004), whereas in the PA, there was an increase of 128.9% (p<0.001) and 254.8% (p<0.001), respectively. The only diameter variation occurred in the SFA pre-operatively with an increase of 11.9% (p=0.007). Tortuosity decomposition revealed significant differences between the 2 planes during the pre-operative and post-operative phases in both extended and flexed configurations, confirming a change in artery position and geometry due to treatment. Conclusions: Knee flexion induces arterial shortening and increased tortuosity in both the pre- and post-operative configuration. Stent placement does not induce significant geometric differences between pre-treatment and post-treatment. These results seem to indicate that the geometry of the covered stent is not affected by the flexion of the knee joint. Despite this, a more detailed analysis of arterial tortuosity showed a change in artery deformation following treatment. Clinical Impact This study aimed to evaluate femoropopliteal arterial deformations in nine patients with popliteal aneurysm before and after endovascular treatment (ET) during knee flexion, using a standardized protocol for CTA acquisition and analysis. The result can be useful in procedure planning and have shown that the Viabahn stent used can adapt to the morphological variations induced by limb flexion. Consequently, device failure does not be attributed to stent compression but rather to other factors, such as alterations in hemodynamic and biomechanical forces on the implant due to the significant changes in tortuosity observed, or biological causes.