Korean J Radiol.  2001 Jun;2(2):75-79. 10.3348/kjr.2001.2.2.75.

Evaluation of the Biodurability of Polyurethane-Covered Stent Using a Flow Phantom

• Kim DH
• Kang SG
• Choi JR
• Byun JN
• Kim YC
• Ahn YM

• KMID: 754108
• DOI: http://doi.org/10.3348/kjr.2001.2.2.75

Abstract

OBJECTIVE
To evaluate the biodurability of the covering material in retrievable metallic stents covered with polycarbonate polyurethane. MATERIALS AND METHODS: Using a peristaltic pump at a constant rate of 1ml/min, bile was recirculated from a reservoir through a long tube containing four stents. Each of these was removed from the system every two weeks and a radial tensile strength test and scanning electron microscopy (SEM) were performed. Each stent, removed at 2, 4, 6 and 8 weeks, was compared with a control stent not exposed to bile juice. RESULTS: Gross examination showed that stents were intact at 2 weeks, but at 4, 6 and 8 weeks cracks were observed. The size of these increased gradually in accordance with the duration of exposure, and at 8 weeks several large holes in the polyurethane membrane were evident. With regard to radial tensile strength, extension and peak load at break were 84.47% and 10.030 N/mm, 54.90% and 6.769 N/mm, 16.55% and 2.452 N/mm, 11.21% and 1.373 N/mm at 0, 2, 4 and 6 weeks, respectively. Scanning electron microscopy at 2 weeks revealed intermittent pitting and cracking, and examination at 4, 6 and 8 weeks showed that the size of these defects was gradually increasing. CONCLUSION: When the polyurethane membrane was exposed to bile, biodegradation was first observed at week two and increased gradually according to the duration of exposure.

Keyword

Biliary stent; Biodegradation; Polyurethane membrane

MeSH Terms

Bile Acids and Salts/physiology
Biodegradation
Hydrogen-Ion Concentration
Microscopy, Electron, Scanning/*instrumentation
Phantoms, Imaging
*Polyurethanes
*Stents
Support, Non-U.S. Gov't
Tensile Strength
Time Factors

Figure

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  Fig. 1 A polyurethane-covered, retrievable, expandable metallic stent.

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  Fig. 2 Experimental settings of a perfusion system composed of a bile reservoir (1), long plastic tube (2) and peristaltic pump (3).

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  Fig. 3 Gross photograph of stent removed after eight weeks (asterisks : holes).

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  Fig. 4 Graph shows peak load and extension at break of covered material according to the duration of exposure to bile.

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  Fig. 5 SEM photomicrographs of polyurethane-covered, retrievable expandable metallic stent after exposure to bile (1,600×) (A: 0 week, B: 2 weeks, C: 4 weeks, D: 6 weeks, E: 8 weeks). Comparison between each specimen at constant magnification showed that the pits and cracks which developed became gradually larger in accordance with the duration of exposure.

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