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CHA PTE R

Design, Simulation, and Experimentation

of Colonic Stents

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,†
Sergio Pu ertolas* , Antonio Herrera †,‡,§ , Eduardo Bajador , Judith Millastre ,
,†
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Elena Ibarz* , Sergio Gabarre , Jos eA.Pu ertolas , Luis Gracia* ,†
k
†
*Department of Mechanical Engineering, University of Zaragoza, Zaragoza, Spain Arago ´n Institute for Engineering
§
‡
Research, Zaragoza, Spain Arago ´n Health Research Institute, Zaragoza, Spain Department of Surgery, University of
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Zaragoza, Zaragoza, Spain Department of Gastroenterology, Lozano Blesa University Hospital, Zaragoza, Spain Vlaams
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#
Instituut voor Biotechnologie, Leuven, Belgium Department of Material Science, University of Zaragoza, Zaragoza, Spain
3.1 INTRODUCTION
Stents are medical devices that scaffold or brace the inside circumference of tubular passages in the human body.
They are endoprostheses with a flexible tubular mesh structure that are manufactured mainly with biocompatible
metallic alloys. Stenting technology has become an alternative to recover the lumen and restore flow or transit in many
vital ducts.
The first applications were for the treatment of coronary atherosclerosis. In 1964 Charles Dotter [1] performed the
first angioplasty in a peripheral artery of the legs. Since then stents have been widely used for the treatment of car-
diovascular ischemia, and their use has been extended to the treatment of stenosis in ducts of the respiratory and diges-
tive system: tracheobronchial, biliary duct, esophageal, urethral or urethral/prostatic, and colon.
Many different stent designs are currently being marketed or evaluated for the foregoing applications with different
characteristics due mainly to the materials used and their structure. Biocompatibility is maintained using materials
such as stainless steel 316L, 316LVM, tantalum, shape memory alloy NiTi [2–4], or more recently biodegradable mate-
rials based on polymers from the lactic acid, glycolic, and caprolactone families [5, 6], and metals [7], either Mg-based
[8, 9] or Fe-based alloys [10]. In fact, metals have superior mechanical properties over polymers for replicating the
properties of SS316L, the reference material for coronary stents.
Usually, the final geometry is a coil, helical, spiral, woven, individual, or sequential ring, and a closed or open cell,
which are manufactured from wires, tubes, ribbons, or sheets by laser cutting, photochemical etching, or wire forming
such as braiding, knitting, etc. Deployment, efficiency, and stability of treatments for stenosis are obtained by balloon-
expandable or self-expanding methods.
In the majority of coronary and noncoronary applications, the combination of different types of biomaterials and
geometries allows stents to be designed with both deployment methods for stenosis: balloon-expandable and self-
expanding stents with different efficiencies and stabilities.
Colonic strictures are a common complication of enteral diseases. Benign causes of obstructions like Crohn’s disease
and ulcerative colitis present a group of strictures scattered throughout the colon, since they are not caused by local
growth of malignant tumor and in most cases evolve favorably under pharmacological treatment. Therefore the use of
stents is not a common practice in benign pathologies. However, colonic stents have been used for more than 20years
for preoperative and palliative relief of malignant colonic obstruction [11, 12].
Large bowel cancer is the most common cancer in the digestive system. Colorectal cancer is the third most common
cancer in men, after lung and prostate cancer, and the second most common in women, after breast cancer, and rep-
resents the second leading cause of cancer death in the world. It is the third most common malignant tumor in

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