Frictional force analysis of stent retriever devices using a realistic vascular model: Pilot study

Abstract

ObjectiveTo date, no vascular model to analyze frictional forces between stent retriever devices and vessel walls has been designed to be similar to the real human vasculature. We developed a novel in vitro intracranial cerebrovascular model and analyzed frictional forces of three stent retriever devices.MethodsA vascular mold was created based on digital subtraction angiography of a patient's cerebral vessels. The vascular model was constructed using polydimethylsiloxane (PDMS, Dow Corning, Inc.) as a silicone elastomer. The vascular model was coated on its inner surface with a lubricating layer to create a low coefficient of friction (~0.037) to closely approximate the intima. A pulsatile blood pump was used to produce blood flow inside the model to approximate real vascular conditions. The frictional forces of Trevo XP, Solitaire 2, and Eric 4 were analyzed for initial and maximal friction retrieval forces using this vascular model. The total pulling energy generated during the 3 cm movement was also obtained.ResultsResults for initial retrieval force were as follows: Trevo, 0.09 ± 0.04 N; Solitaire, 0.25 ± 0.07 N; and Eric, 0.33 ± 0.21 N. Results for maximal retrieval force were as follows: Trevo, 0.36 ± 0.07 N; Solitaire, 0.54 ± 0.06 N; and Eric, 0.80 ± 0.13 N. Total pulling energy (N·cm) was 0.40 ± 0.10 in Trevo, 0.65 ± 0.10 in Solitaire, and 0.87 ± 0.14 in Eric, respectively.ConclusionsUsing a realistic vascular model, different stent retriever devices were shown to have statistically different frictional forces. Future studies using a realistic vascular model are warranted to assess SRT devices.

Methods for Evaluating Friction between Intravascular Device and Vascular Biomodel

“…Experiments using more complex vascular models made of silicone rubber [29,[35][36][37][38][39], acrylic [40], poly(vinyl alcohol) hydrogel [25][26][27][30][31][32][33], and elastomer-hydrogel skin multilayers [9,28] that mimic living tissue have also been conducted. 3D printers are widely used to prepare biomodels and can easily fabricate mold copies of the vascular tree, which is subsequently embedded in a liquid resin that solidifies into a solid biomodel.…”

“…• It has been reported that continuous insertion at a constant speed into silicone that simulates an aneurysm requires half or less of the maximum force required for intermittent insertion by a doctor, presumably because static friction is exerted when the insertion is paused [35]. • A pulsatile blood pump has been used to generate a pulsating flow with approximately physiological conditions [39]. Khoshbakht et al [98] showed that fluid flow can greatly change the tip contact force when the catheter is close to the left inferior pulmonary vein.…”

“…Biomodels that mimic various types of vasculature [9,[25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] can be used to test new endovascular medical devices and teach techniques to medical personnel; they also allow the practice and planning of procedures before treatment without exposing patients to X-rays. Moreover, biomodels are more economical and ethical compared to human cadavers and animals.…”

“…Water. Kwak et al [39] PDMS patient-specific vascular model coated with lubricating layer vs. three commercially available stent retriever devices. Initial and maximum force during withdrawal (1 mm/s).…”