Mechanical Characterization of Self-Expandable Esophageal Metal Stents

Lee, Kyu Back; Chun, Hoon Jai; Kim, Yun Bae; Kim, Young Sun; Park, Jae Hong; Moon, Taekgyun; Hong, Daehie; Hyun, Jin Hai

Abstract

Backgound/Aims: One of the most important mechanical properties to consider in selecting clinically optimal stents would be expansile pressure. However, there were scanty data about the expansile pressure of stents. Furthermore, the data were improper for the clinical selection of stents. In this study, the authors tried to develop a precise and reproducible expansile pressure measurement method and to measure the expansile pressure of a variety of stent types.
METHODS
We developed a new method of expansile force measurement using a cylindrical measurement device under a quasi-static equilibrium state and measured the expansile forces of six different stents made by various manufacturers; covered and uncovered Y2P SR , covered Y3E SR (Stentech, Korea), covered and uncovered Ultraflex and uncovered Wallstent (Boston Scientific, USA)
RESULTS
Three important points critical in explaining and predicting the expansion characteristics of stents were found. Firstly, the radial expansion force varies greatly among the types of stents. Secondly, stents could be categorized to "soft stent" and "stiff stent" based upon the slope of expansion force change. Lastly, the initial force needed to compress the fully expanded stents is far greater in stents covered with membrane compared with the stents without membrane.
CONCLUSIONS
The newly developed method of measurement helped the authors to get more realistic data of expansion force and pressure, which are thought to be helpful in clinical selection of stent type.