Assessment of self-expanding nitinol stent deformation after chronic implantation into the femoropopliteal arteries

AIMS: The purpose of this prospective clinical investigation was to quantify the degree and range of compressive and bending deformations sustained by self-expanding nitinol stents when implanted into the femoropopliteal arteries of patients with symptomatic peripheral vascular disease (PVD). METHODS AND RESULTS: Twenty-three nitinol self-expanding stents (Absolute; Abbott Vascular, Santa Clara, CA, USA) with diameters ranging from 5-10 mm and lengths ranging from 40-100 mm were implanted in 19 lesions in 18 extremities of 17 patients. Two days following implantation, in vivo stent compression and bending were assessed by measurement of stent length and deflection angle via lateral view radiographs. The results showed that leg flexion was associated with significant stent bending; popliteal stents bent almost 90° while SFA stents bent only minimally. Leg flexion was also associated with stent shortening (compression), the greatest amount being observed for stents implanted into the popliteal artery (popliteal 8.5% ± 3.2%; SFA/prox pop 5.3% ± 0.5%; SFA 3.1% ± 1.8%). After a mean follow-up of 7.1 ± 1.3 months, the degree of stent deformation during leg flexion was essentially unchanged as compared to immediate post-procedure levels. CONCLUSIONS: Indwelling nitinol stents are routinely bent and compressed during leg flexion, with most bending observed in stents implanted near the popliteal artery. The degree of deformation observed immediately after implantation appears to be predictive of the chronic state, as repeat measurements obtained after a mean of seven months were essentially unchanged from baseline.