Mechanical Behavior of Radial Support of a Novel Balloon Expandable Tapered Stent / 医用生物力学

Objective To explore influences of the taper and connecting rib form on supporting performance of the stent, and provide an important scientific basis for structural design and clinical selection of the tapered stent. Methods A nonlinear finite element model for radial support performance of a novel balloon-expandable tapered stent was constructed, and the radial stiffness (RS) and stress distributions of the stent at different tapers (0°, 0.565°and 1.13°) and with different structural forms of stent linker (V-shape, I-shape, C-shape, S-shape, M-shape) were analyzed by plane compression. The relationship between structural design of the vascular stent and its radial support performance was studied. Results The RS of 0°stent, 0.565°stent, 1.13° stent was 2.51, 1.61, 0.85 N/mm, respectively. The RS of 0.565°stent and 1.13° stent was 35.86% and 66.14% lower than that of 0°stent (round straight stent), respectively. Except that the RS of C-shape linker stent was 1.48 N/mm, the RS of I, M, S and V-shape linker stents was not significantly different, which was 2.51, 2.61, 2.41, 2.52 N/mm, respectively, indicating that radial compression resistance of these four linker stents was almost the same. Conclusions Compared with traditional round straight stents, the RS of tapered stents will decrease, and the RS of stents will gradually decrease with the the taper increasing. Among all stent types in this study, except C-shape linker stents, the RS of other linker shapes has little effect on the RS of stents. The radial support performance of the stent can be improved by reducing the taper of the tapered stent, without changing the form of stent connecting ribs.

Mechanical Properties of Optimized Stent Retrievers / 医用生物力学

Objective To analyze mechanical properties of stent retrievers with different structures, and provide theoretical support for the design and clinical selection of stent retrievers. Methods Three kinds of stent retrievers with different structures (B3, K4, X) were evaluated by finite element analysis and in vitro simulation experiment. The analytic parameters were radial support force, withdrawal force and thrombosis state during the thrombotomy test. Results The radial support forces of B3, K4, X stent retrievers obtained from the experiment were 0.48 N, 0.43 N, 0.51 N, respectively. The larger the crimping distance, the greater the radial support force of stent retrievers. The radial support force of the stent increased significantly when the crimping distance was larger than 3 mm. The simulated thrombus removal experiment results showed that the peak withdrawal forces of B3, K4, X stent retrievers were 0.410 N, 0.451N, 0.501 N, respectively. The experimental results were consistent with the finite element analysis results. Conclusion sBoth the experimental results and the finite element results showed that the X stent has better mechanical properties. This method can be used as an analytic method to evaluate performance of the stent retrievers, and provide references for performance improvement and development of the stent retrievers.

In vitro experimental study on the mechanical properties of biodegradable polymer stents / 生物医学工程学杂志

experimental test for mechanical properties of a vascular stent is a main method to evaluate its effectiveness and safety, which is of great significance to the clinical applications. In this study, a comparative study of planar, V-groove and radial compression methods for the radial support property test were performed, and the effects of compression rate and circumferential position on the test results were conducted. Based on the three-point bending method, the influences of compression rate and circumferential position on flexibility were also explored. And then a best test proposal was selected to evaluate the radial support property and flexibility of the three self-designed stents and the comparative biodegradable vascular stent (BVS) (BVS1.1, Abbott Vascular, USA) with different outside diameters of 1.4 mm, 1.7 mm and 2.4 mm. The results show that the developing trends of the compression load with the compression displacement measured by the three radial support property test methods are the same, but normalized radial force values are quite different. The planar compression method is more suitable for comparing the radial support properties of stents with different diameters and structures. Compression rate has no obvious effect on the testing results of both the radial support property and flexibility. Compression circumferential position has a great impact on testing radial support property with the planar or V-groove compression methods and testing flexibility with three-point bending method. The radial support properties of all the three self-designed stents are improved at a certain degree compared to that of the BVS stent. The study has better guide significance and reference value for testing mechanical properties of vascular stents.