Quantitative assessment of the conformational change in the femoropopliteal artery with leg movement

Abstract

The unique physical forces exerted on the femoropopliteal (FP) artery during movement have been implicated in the high rates of restenosis and stent fracture in this artery. Conformational changes in the FP artery during movement are important surrogates of these forces. This study sought to quantify the conformational change in the FP artery between the straight-leg (SL) and crossed-leg (CL) positions. Using paired angiographic images of overlapping segments of the FP artery in SL and CL positions from patients with peripheral arterial disease, 3-D models of individual segments were generated and subsequently fused to create a 3-D model of the entire FP artery in both leg positions. Based on these 3-D models, the following parameters in the SL and CL positions were quantitatively assessed for the superficial femoral artery (SFA), popliteal artery (PA), and FP artery (i.e., SFA and PA): length, curvature, torsion, twist angle, and development of new flexion angles = 15 degrees. In nine male patients with a mean age of 57 +/- 10.2 years, angiography was performed in 10 FP arteries, with successful generation of 3-D models for all vessels. Movement from the SL to the CL position for the SFA, PA, and FP artery was associated with (a) a mean shortening of 18.2 mm (P = 0.002), 32.2 mm (P < 0.001), and 50.3 mm (P < 0.001), respectively; (b) a mean increase in curvature of 0.04 cm(-1) (P = 0.012), 0.2 cm(-1) (P < 0.001), and 0.11 cm(-1) (P < 0.001), respectively; (c) and small absolute changes in mean torsion of 0.034 cm(-1) (P = 0.48), 0.006 cm(-1) (P < 0.001), and 0.057 cm(-1) (P < 0.001), respectively. The same leg movement was associated with a mean twist angle of 45.6 degrees +/- 27.9 degrees (range of 17.4 degrees-103.4 degrees ) and 61.1 degrees +/- 31.9 degrees (range of 20.5 degrees-101.1 degrees ) for the SFA and PA, respectively. Compared to the SL position, the CL position induced a single flexion point (FxP) =15 degrees in the SFA in two patients, and a mean of 2.4 FxPs =15 degrees (range 1-5) in the PA. Significant changes in length, curvature, and twist occur in the PA and significant but more modest changes in length and twist occur in the SFA during movement from the SL to the CL position. This data has important implications for endovascular therapies that are used to treat disease in the FP artery.