Mechanical Characteristics of Self-expandable Metallic Stents: In Vitro Study with Three of Stress

PURPOSE: To obtain objective and comparable date for mechanical characteristics of self-expandable metallicstents widely used in the treatment of biliary obstruction. MATERIALS AND METHODS: The stents tested were the 6and 9 mm-band Hanaro spiral stent, Gianturco-R sch Z stent, Wallstent, Ultraflex stent, and Memotherm stent. Eachwas subjected to three types of load : point, area, and circular. We analyzed their mechanical characteristics(resistance force, expansile force, and elasticity) according to these three types of stress. RESULTS: Withregard to point loads, the Memotherm stent showed the highest resistance force and expansile force. The 8 mm-bandhanaro stent showed the lowest resistance force and the Gianturco-R sch Z stent and Ultraflex stent showed lowerexpansile force. With regard to area loads, the Ultraflex stent showed the highest resistance force. The 6 mm-bandHanaro stent, Gianturco-R sch Z stent, and Ultraflex stent showed higher expansile force. The 8 mm-band Hanarostent showed the lowest value in both resistance force and expansile force. For circular loads, the Memothermstent showed the highest resistance force and the Ultraflex stent and Wallstent showed lower Value. Under alltypes of stress, the Hanaro stent and Memotherm stent were completel elastic, and the Ultraflex stent andWallstent showed a wide gap between resistance force and expansile force. CONCLUSION: In clinical practice,awareness of the mechanical characteristics of each stent might help in choosing the one which is most suitable,according to type of biliary obstruction.