Characterization of Radial Forces in Z Stents

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Abstract
Snowhill PB, Nosher JL, Siegel RL, et al. Characterization of radial forces in z stents. Invest Radiol 2001;36:521–530. The purpose of this study was to evaluate the effects of variation in design parameters on the resultant radial force. We evaluated the influence of wire gauge, leg length, and number of bends on the radial force produced by z stents and compared these with radial forces produced by commercial stents. A second goal was to develop an engineering model for predicting radial forces generated by z stents. Z stents were fashioned by hand using stainless steel wire and solder that connected the ends. The radial force was measured as a function of wire gauge, vessel diameter, leg length, and number of bends and compared with the theoretical values of radial force calculated by combining Castigliano’s theorem and the law of Laplace. Theoretically predicted radial forces were within 8% of each observed value of radial force up to 70% spring compression. These results suggest that the z-stent model can be used to build custom stents with preselected values of radial force for clinical use. In addition, they can be used to design model investigational stents made of similar materials and surface areas to test the effects of radial force on biological response.