Helical coil polymeric stents provide an alternative method of stenting compared to traditional metallic stents, but require additional investigation to understand deployment, expansion, and fixation. A bilayer helical coil stent consisting of PLLA and PLGA was investigated using the finite element model to evaluate performance by uniform expansion and subsequent recoiling. In vitro material characterization studies showed that a preinsertion water-soaking step to mimic body implantation conditions provided the required ductility level expansion. In this case, the mechanical contribution of the outer PLGA layer was negligible since it softened significantly under environmental conditions. The viscoelastic response was not considered in this study since the strain rate during expansion was relatively slow and the material response was primarily plastic. The numerical model was validated with available experimental expansion and recoiling data. A parametric study was then undertaken to investigate the effect of stent geometry and coefficient of friction at the stent-cylinder interface on the expansion and recoiling characteristics. The model showed that helical stents exhibit a uniform stress distribution after expansion, which is important for controlled degradation when using biodegradable materials. The results indicated that increasing stent width, pitch value, and coil thickness resulted in a larger diameter after recoiling, which would improve fixation in the artery. It was also noted that a helical stent should have more than five coils to be stable after recoiling. This work is part of a larger research study focused on the performance of a balloon-inflated polymeric helical stent for artery applications.
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June 2012
Research Papers
Uniform Expansion of a Polymeric Helical Stent
Nasim Paryab,
Nasim Paryab
Department of Mechanical and Mechatronics Engineering,
University of Waterloo, 200 University Avenue West Waterloo
, Ontario N2L 3G1, Canada
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Duane Cronin,
Duane Cronin
Department of Mechanical and Mechatronics Engineering,
University of Waterloo, 200 University Avenue West Waterloo
, Ontario N2L 3G1, Canada
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Pearl Lee-Sullivan,
Pearl Lee-Sullivan
Department of Mechanical and Mechatronics Engineering,
University of Waterloo, 200 University Avenue West Waterloo
, Ontario N2L 3G1, Canada
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Xiong Ying,
Xiong Ying
Nanyang Technological University
, Nanyang Avenue, Singapore 639798, Singapore
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Freddy Y. C. Boey,
Freddy Y. C. Boey
Nanyang Technological University
, Nanyang Avenue, Singapore 639798, Singapore
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Subbu Venkatraman
Subbu Venkatraman
Nanyang Technological University
, Nanyang Avenue, Singapore 639798, Singapore
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Nasim Paryab
Department of Mechanical and Mechatronics Engineering,
University of Waterloo, 200 University Avenue West Waterloo
, Ontario N2L 3G1, Canada
Duane Cronin
Department of Mechanical and Mechatronics Engineering,
University of Waterloo, 200 University Avenue West Waterloo
, Ontario N2L 3G1, Canada
Pearl Lee-Sullivan
Department of Mechanical and Mechatronics Engineering,
University of Waterloo, 200 University Avenue West Waterloo
, Ontario N2L 3G1, Canada
Xiong Ying
Nanyang Technological University
, Nanyang Avenue, Singapore 639798, Singapore
Freddy Y. C. Boey
Nanyang Technological University
, Nanyang Avenue, Singapore 639798, Singapore
Subbu Venkatraman
Nanyang Technological University
, Nanyang Avenue, Singapore 639798, Singapore
J. Med. Devices. Jun 2012, 6(2): 021012 (10 pages)
Published Online: May 14, 2012
Article history
Received:
December 18, 2009
Accepted:
May 27, 2011
Online:
May 14, 2012
Published:
May 14, 2012
Citation
Paryab, N., Cronin, D., Lee-Sullivan, P., Ying, X., Boey, F. Y. C., and Venkatraman, S. (May 14, 2012). "Uniform Expansion of a Polymeric Helical Stent." ASME. J. Med. Devices. June 2012; 6(2): 021012. https://doi.org/10.1115/1.4005777
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