Basic Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Aug 14, 2016; 22(30): 6917-6924
Published online Aug 14, 2016. doi: 10.3748/wjg.v22.i30.6917
Evaluation of anti-migration properties of biliary covered self-expandable metal stents
Kosuke Minaga, Masayuki Kitano, Hajime Imai, Yogesh Harwani, Kentaro Yamao, Ken Kamata, Takeshi Miyata, Shunsuke Omoto, Kumpei Kadosaka, Toshiharu Sakurai, Naoshi Nishida, Masatoshi Kudo
Kosuke Minaga, Masayuki Kitano, Hajime Imai, Yogesh Harwani, Kentaro Yamao, Ken Kamata, Takeshi Miyata, Shunsuke Omoto, Kumpei Kadosaka, Toshiharu Sakurai, Naoshi Nishida, Masatoshi Kudo, Department of Gastroenterology and Hepatology, Kindai University Faculty of Medicine, Osaka-Sayama 589-8511, Japan
Author contributions: All authors helped to perform the research; Kitano M and Kudo M drafted conception and design; Minaga K and Kitano M performed the experiments, analyzed the data, and wrote the manuscript; Imai H, Harwani Y, Yamao K, Kamata K, Miyata T, Omoto S, Kadosaka K, Sakurai T, Nishida N and Kudo M contributed to writing the manuscript.
Supported by Japan Society for the Promotion of Science and the Japanese Foundation for the Research and Promotion of Endoscopy, No. 22590764 and No. 25461035.
Institutional review board statement: This study was approved by the Institutional Review Board of Kindai University Faculty of Medicine.
Conflict-of-interest statement: All authors declare no conflicts-of-interest related to this article.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Masayuki Kitano, MD, PhD, Department of Gastroenterology and Hepatology, Kindai University Faculty of Medicine, 377-2 Ohno-Higashi, Osaka-Sayama 589-8511, Japan. m-kitano@med.kindai.ac.jp
Telephone: +81-72-3660221 Fax: +81-72-3672880
Received: February 17, 2016
Peer-review started: February 19, 2016
First decision: March 31, 2016
Revised: April 4, 2016
Accepted: April 15, 2016
Article in press: April 15, 2016
Published online: August 14, 2016
Processing time: 168 Days and 21.5 Hours
Abstract

AIM: To assess anti-migration potential of six biliary covered self-expandable metal stents (C-SEMSs) by using a newly designed phantom model.

METHODS: In the phantom model, the stent was placed in differently sized holes in a silicone wall and retracted with a retraction robot. Resistance force to migration (RFM) was measured by a force gauge on the stent end. Radial force (RF) was measured with a RF measurement machine. Measured flare structure variables were the outer diameter, height, and taper angle of the flare (ODF, HF, and TAF, respectively). Correlations between RFM and RF or flare variables were analyzed using a linear correlated model.

RESULTS: Out of the six stents, five stents were braided, the other was laser-cut. The RF and RFM of each stent were expressed as the average of five replicate measurements. For all six stents, RFM and RF decreased as the hole diameter increased. For all six stents, RFM and RF correlated strongly when the stent had not fully expanded. This correlation was not observed in the five braided stents excluding the laser cut stent. For all six stents, there was a strong correlation between RFM and TAF when the stent fully expanded. For the five braided stents, RFM after full stent expansion correlated strongly with all three stent flare structure variables (ODF, HF, and TAF). The laser-cut C-SEMS had higher RFMs than the braided C-SEMSs regardless of expansion state.

CONCLUSION: RF was an important anti-migration property when the C-SEMS did not fully expand. Once fully expanded, stent flare structure variables plays an important role in anti-migration.

Keywords: Biliary stricture; Self-expandable metal stent; Radial force; Resistance force to migration; Anti-migration property

Core tip: Ability of prevention of migration is very important to improve the results of covered self-expandable metal stents (C-SEMSs) for biliary stricture. This study aims to assess the anti-migration potential of six C-SEMSs by using a newly designed phantom model which allows the resistance force to migration (RFM) measurement of the stents. We found that RFM and radial force correlated strongly when the stent had not fully expanded. Once fully expanded, stent flare structure variables affected the anti-migration property of the stent. We concluded that several stent properties, including radial force and flare structure should be considered when selecting C-SEMS.