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.

References

1.
Duraiswamy
,
N.
,
Schoephoerster
,
R.
,
Moreno
,
M.
, and
Moore
,
J. J. E.
, 2007, “
Stented Artery Flow Patterns and Their Effects on the Artery Wall
,”
Ann. Rev. Fluid Mech.
,
39
, pp.
257
382
.
2.
Dotter
,
C.
, 1969, “
Transluminally-Placed Coilspring Endarterial Tube Grafts: Long-Term Patency in Canine Popliteal Artery
,”
Investigative Radiol.
,
4
, pp.
329
332
.
3.
Stoeckel
,
D.
,
Bonsignore
,
C.
, and
Duda
,
S.
, 2002, “
A Survey of Stent Designs
,”
Minimally Invasive Therapy Allied Technol.
,
11
, pp.
137
147
.
4.
Kandzari
,
D. E.
,
Tcheng
,
J. E.
, and
Zidar
,
J. P.
, 2002, “
Coronary Artery Stents: Evaluating New Designs for Contemporary Percutaneous Intervention
,”
Catheter. Cardiovas. Intervent.
,
56
, pp.
562
576
.
5.
Burt
,
H.
, and
Hunter
,
W.
, 2006, “
Drug-Eluting Stents: A Multidisciplinary Success Story
,”
Adv. Drug Delivery Rev.
,
58
, pp.
350
357
.
6.
Rosanio
,
S.
,
Tocchi
,
M.
,
Patterson
,
C.
, and
Runge
,
M.
, 1999, “
Prevention of Restenosis After Percutaneous Coronary Interventions
,”
Thromb. Haemost
,
82
, pp.
164
167
.
7.
Regar
,
E.
,
Sianos
,
G.
, and
Serruys
,
P.
, 2001, “
Stent Development and Local Drug Delivery
,”
Br. Med. Bull.
,
59
, pp.
277
248
.
8.
Schwartz
,
R.
, and
Henry
,
T.
, 2002, “
Pathphysiology of Coronary Artery Restenosis
,”
Rev. Cardiovas. Med.
,
3
, pp.
4
9
.
9.
Wang
,
R.
, and
Ravi-Chandar
,
K.
, 2004, “
Mechanical Response of a Metallic Aortic Stent—Part I: Pressure-Diameter Relationship
,”
J. Appl. Mech.
,
71
, p.
697
.
10.
Lally
,
C.
,
Dolan
,
F.
, and
Prendergast
,
P.
, 2005, “
Cardiovascular Stent Design and Vessel Stresses: A Finite Element Analysis
,”
J. Biomech.
,
38
, pp.
1574
1581
(2005).
11.
Athanasiou
,
K. A.
,
Niederauer
,
G. G.
, and
Agrawal
,
C. M.
, 1996, “
Sterilization, Toxicity, Biocompatibility and Clinical Applications of Polylactic Acid/ Polyglycolic Acid Copolymers
,”
Biomaterials
,
17
(
2
), pp.
93
102
.
12.
Welch
,
T.
,
Eberhart
,
R.
, and
Chuong
,
C.
, 2008, “
Characterizing the Expansive Deformation of a Bioresorbable Polymer Fiber Stent
,”
Ann. Biomed. Eng.
,
36
, pp.
742
751
.
13.
Vaajanen
,
A.
,
Nuutinen
,
J.
,
Isotalo
,
T.
,
Tammela
,
T. L. J.
, and
Talja
,
M.
, 2003, “
Expansion and Fixation Properties of a New Braided Biodegradable Urethral Stent: An Experimental Study in the Rabbit
,”
J. Urol.
,
169
, pp.
1171
1174
.
14.
Tan
,
L. B.
,
Webb
,
D. C.
,
Kormi
,
K.
, and
Al-Hassani
,
S. T. S.
, 2001, “
A Method for Investigating the Mechanical Properties of Intracoronary Stents Using Finite Element Numerical Simulation
,”
Int. J. Cardiol.
,
78
, pp.
51
67
.
15.
Su
,
S.-H.
,
Chao
,
R.
,
Landau
,
C.
,
Nelson
,
K. D.
,
Timmons
,
R. B.
,
Meidell
,
R. S.
, and
Eberhart
,
R. C.
, 2003, “
Expandable Bioresorbable Endovascular Stent. I. Fabrication and Properties
,”
Ann. Biomed. Eng.
,
31
, pp.
667
677
.
16.
Grabow
,
N.
,
Bunger
,
C. M.
,
Schultze
,
C.
,
Schmohl
,
K.
,
Martin
,
D. P.
,
Williams
,
S. F.
,
Sternberg
,
K.
, and
Schmitz
,
K.-P.
, 2007, “
A Biodegradable Slotted Tube Stent Based on Poly(L-Lactide) and Poly(4-Hydroxybutyrate) for Rapid Balloon-Expansion
,”
Ann. Biomed. Eng.
,
35
(
12
), pp.
2031
2038
.
17.
Grabow
,
N.
,
Schlun
,
M.
,
Sternberg
,
K.
,
Hakansson
,
N.
,
Kramer
,
S.
, and
Schmitz
,
K.-P.
, 2005, “
Mechanical Properties of Laser Cut Poly(L-Lactide) Micro-Specimens: Implications for Stent Design, Manufacture, and Sterilization
,”
ASME J. Biomechan. Eng.
,
127
pp.
25
31
.
18.
Soares
,
J. S.
,
Moore
, Jr.,
J. E.
, and
Rajagopal
,
K. R.
, 2010, “
Modeling of Deformation—Accelerated Breakdown of Polylactic Acid Biodegradable Stents
,”
ASME J. Med. Dev.
,
4
, p.
041007
.
19.
Chu
,
C. C.
, 1985, “
Strain-Accelerated Hydrolytic Degradation of Synthetic Absorbable Sutures
, in
Surgical Research, Recent Developments: Proceedings of the First Annual Scientific Session of the Academy of Surgical Research
, San Antonio, pp.
111
115
.
20.
Lansky
,
A. J.
,
Roubin
,
G. S.
,
O’Shaughnessy
,
C. D.
,
Moore
,
P. B.
,
Dean
,
L. S.
,
Raizner
,
A. E.
,
Safian
,
R. D.
,
Zidar
,
J. P.
,
Kerr
,
J. L.
,
Popma
,
J. J.
,
Mehran
,
R.
,
Kuntz
,
R. E.
, and
Leon
,
M. B.
, 2000, “
Randomized Comparison of GR-II Stent and Palmaz-Schatz Stent
,”
Circulation
,
102
, pp.
1364
1368
.
21.
Bedoya
,
J.
,
Meyer
,
C. A.
,
Timmins
,
L. H.
,
Moreno
,
M. R.
, and
Moore
,
J. E.
, Jr.
, 2006, “
Effect of Stent Design Parameters on Normal Artery Wall Mechanics
,”
ASME J Biomech. Eng.
,
128
, pp.
757
765
.
22.
Tamura
,
S.
,
Hirao
,
M.
,
Shiozaki
,
H.
,
Inoue
,
M.
,
Hashimoto
,
T.
,
Hori
,
S.
,
Ohkata
,
I.
,
Asano
,
H.
, and
Monden
,
M.
, 1996, “
A Newly-Designed Shape-Memory Coil Stent for Esophageal Stricture: A Preliminary Report
,”
Surg. Today, Jpn. J. Surg.
,
26
, pp.
945
948
.
23.
Vogt
,
F.
,
Stein
,
A.
,
Rettemeier
,
G.
,
Krottb
,
N.
,
Hoffmann
,
R.
,
vom Dahl
,
J.
,
Bosserhoff
,
A.
,
Michaeli
,
W.
,
Hanrath
,
P.
,
Weber
,
C.
, and
Blindt
,
R.
, 2004, “
Long-Term Assessment of a Novel Biodegradable Paclitaxel-Eluting Coronary Polylactide Stent
,”
Eur. Heart J.
,
25
, pp.
1330
1340
.
24.
Meng
,
B.
,
Wang
,
J.
,
Zhu
,
N.
,
Meng
,
Q.
,
Cui
,
F.
, and
Xu
,
Y.
, 2006, “
Study of Biodegradable and Self-Expandable PLLA Helical Biliary Stent In-Vivo and In-Vitro
,”
J. Mater. Sci.
,
17
, pp.
611
617
.
25.
Venkatraman
,
S.
, Lay
Poh
,
T.
,
Vinalia
,
T.
, Hou
Mak
,
K.
, and
Boey
,
F.
, 2003, “
Collapse Pressures of Biodegradable Stents
,”
Biomaterials
,
24
, pp.
2105
2111
.
26.
Tan
,
L. P.
,
Venkatraman
,
S. S.
,
Joso
,
J. F. D.
, and
Boey
,
F. Y. C.
, 2006, “
Collapse Pressures of Bilayered Biodegradable Stents
,”
Inc. J. Biomed. Mater. Res. Part B: Appl. Biomater.
,
79B
, pp.
102
107
.
27.
Agrawal
,
C. M.
,
Haas
,
K. F.
,
Leopold
,
D. A.
, and
Clark
,
H. G.
, 1992, “
Evaluation of Ploy (L-Lactic Acid) As a Material for Intravascular Polymeric Stents
,”
Biomaterials
,
13
, pp.
176
182
.
28.
Stolpmann
,
J.
,
Brauer
,
H.
,
Stracke
,
H.
,
Erbel
,
R.
, and
Fischer
,
A.
, 2003, “
Practicability and Limitations of Finite Element Simulation of the Dilation Behavior of Coronary Stents
,”
Mater. Wissenschaft Werkstofftech
,
34
, pp.
736
745
.
29.
Auricchio
,
F.
,
Loretoand
,
M.
, and
Sacco
,
E.
, 2000, “
Finite Element Analysis of a Stenotic Artery Revascularization Through a Stent Insertion
,”
Comput. Methods Biomech. Biomed. Eng.
,
4
, pp.
1
5
.
30.
Wang
,
W.
,
Liang
,
D.
,
Yang
,
D.
, and
Qi
,
M.
, 2006, “
Analysis of the Transient Expansion Behaviour and Design Optimization of Coronary Stents by Finite Element Method
,”
J. Biomech.
,
39
, pp.
21
32
.
31.
Rogers
,
C.
,
Tseng
,
D. Y.
,
Squire
,
J. C.
, and
Edelman
,
E. R.
, 1999, “
Balloon-Artery Interactions During Stent Placement
,”
Circ. Res.
,
84
, pp.
378
383
.
32.
Migliavacca
,
F.
,
Petrini
,
L.
,
Colombo
,
M.
,
Auricchio
,
F.
, and
Pietrabissa
,
R.
, 2002, “
Mechanical Behaviour of Coronary Stents Investigated Through the Finite Element Method
,”
J. Biomech.
,
35
, pp.
803
811
.
33.
Walke
,
W.
,
Paszenda
,
Z.
, and
Filipiak
,
J.
, 2005, “
Experimental and Numerical Biomechanical Analysis of Vascular Stent
,”
J. Mater. Process. Technol.
,
164 165–
, pp.
1263
1268
.
34.
Venkatraman
,
S.
,
Tan
,
L.
,
Joso
,
J.
,
Boey
,
Y.
, and
Wang
,
X.
, 2006, “
Biodegradable Stents With Elastic Memory
,”
Biomaterials
,
27
, pp.
1573
1578
.
35.
Kumar
,
F. S.
,
Boey
,
F.
, and
Venkatraman
,
S.
, 2004, “
Study of the Initial Stages of Drug Release From a Degradable Matrix of PLGA
,”
Biomaterials
,
25
, pp.
813
821
.
36.
A Personal Communication With NTU With Biodegradable Helical Stent Designer in Material Department of Nanyang Technological University (NTU).
37.
Bünger
,
C. M.
,
Grabow
,
N.
,
Sternberg
,
K.
,
Kröger
,
C.
,
Ketner
,
L.
,
Schmitz
,
K.-P.
,
Kreutzer
,
H. J.
,
Ince
,
H.
,
Nienaber
,
C. A.
,
Klar
,
E.
, and
Schareck
,
W.
, 2007, “
Sirolimus-Eluting Biodegradable Poly-L-Lactide Stent for Peripheral Vascular Application: A Preliminary Study in Porcine Carotid Arteries
,”
J. Surg. Res.
,
139
, pp.
77
82
.
38.
Brinson
,
H. F.
, and
Brinson
,
L. C.
, 2008,
Polymer Engineering Science and Viscoelasticity
”,
Springer
,
New York
.
39.
Dumoulin
,
C.
, and
Cochelin
,
B.
, 2000, “
Mechanical Behaviour Modeling of Balloon-Expandable Stents
,”
J. Biomech.
,
33
, pp.
1461
1470
.
40.
McGarry
,
J. P.
,
O’Donnell
,
B. P.
,
McHugh
,
P. E.
, and
McGarry
,
J. G.
, 2004, “
Analysis of the Mechanical Performance of a Cardiovascular Stent Design Based on Micromechanical Modeling
,”
Comput. Mater. Sci.
,
31
, pp.
421
438
.
41.
Paszenda
,
Z.
,
Walke
,
W.
, and
Filipiak
,
J.
, 2005, “
Experimental and Numerical Biomechanical Analysis of Vascular Stent
,”
J. Mater. Processi. Technol.
,
164 165–
, pp.
1263
1268
.
42.
Mori
,
K.
, and
Saito
,
T.
, 2005, “
Effect of Stent Structure on Stent Flexibility Measurement
,”
Ann. Biomed. Eng.
,
33
, pp.
733
742
.
43.
Martin
,
H.
,
Grabow
,
N.
, and
Schmitz
,
K. P.
, 2002, “
The Impact of Material Characteristics on the Mechanical Properties of a Poly (L-Lactide) Coronary Stent
,”
Biomed. Tech.
,
47
, pp.
503
505
.
44.
Chen
,
S. I.
,
Tsai
,
C. H.
,
Liu
,
J. S.
,
Kan
,
H. C.
,
Yao
,
C. M.
,
Lee
,
L. C.
,
Shih
,
R. J.
, and
Shen
,
C. Y.
, 2009, “
The Biomechanical Analysis of the Coil Stent and Mesh Stent
,”
ICBME Proc.
,
23
, pp.
1592
1594
.
45.
Oberhofer
,
G.
,
Gese
,
H.
,
Grob
,
M.
,
Kuhling
,
M.
, and
Seidel
,
D.
, 2006, “
Numerical Analysis of the Balloon Dilatation Process Using the Explicit Finite Element Method for the Optimization of a Stent Geometry
,” in
Proceedings of Ls-Dyna Anwender Forum
, ULM 2006, pp.
35
46
.
46.
Laroche
,
D.
,
Delorme
,
S.
,
Anderson
,
T.
, and
DiRaddo1
,
R.
, 2006, “
Computer Prediction of Friction in Balloon Angioplasty and Stent Implantation
,”
Lecture Notes Comput. Sci.
,
4072
, pp.
1
8
.
47.
Mortier
,
P.
,
De Beule
,
M.
,
Carlier
,
S. G.
, Van
Impe
,
R.
,
Verhegghe
,
B.
, and
Verdonck
,
P.
, 2008, “
Numerical Study of the Uniformity of Balloon-Expandable Stent Deployment
,”
ASME J. Biomechan. Eng.
,
130
, p.
021018
.
48.
De Beule
,
M.
,
Mortier
,
P.
,
Carlier
,
S. G.
,
Verhegghe
,
B.
,
Van Impe
,
R.
, and
Verdonck
,
P.
, 2008, “
Realistic Finite Element-Based Stent Design: The Impact of Balloon Folding
,”
J. Biomech.
,
41
, pp.
383
389
.
49.
Lim
,
D.
,
Cho
,
S.
,
Park
,
W.
,
Kristensson
,
A.
,
Ko
,
J.
,
Al-Hassani
,
S. T. S.
, and
Kim
,
H.
, 2008, “
Suggestion of Potential Stent Design Parameters to Reduce Restenosis Risk Driven by Foreshortening or Dogboning Due to Non-Uniform Balloon-Stent Expansion
,”
Ann. Biomed. Eng.
,
36
, pp.
1118
1129
.
50.
Friction Coefficients, http://www.engineershandbook.com/Tables/frictioncoefficients.htm
51.
Hibbeler
,
R. C.
, 1999,
Mechanics of Materials
, 4th ed.,
Prentice Hall
,
Englewood Cliffs, New Jersey
.
52.
Yang
,
J.
,
Liang
,
M. B.
,
Huang
,
N.
, and
Liux
,
Y. L.
, 2010, “
Studying the Non-uniform Expansion of a Stent Influenced By the Balloon
,”
J. Med. Eng. Technol.
,
34
(
5–6
), pp.
301
305
.
You do not currently have access to this content.