Stents using nitinol wire or nitinol tube are being widely used.
The method of treating vascular stenosis is to support the blood vessels from the inside by placing stents to obtain sufficient blood flow. Nitinol stents can also be used to treat the trachea, esophagus, large intestine and bile duct that have narrowed due to cancer. The former generally uses nitinol tubes, while the latter is made of nitinol wire due to size reasons. The principles of both are the same. The mesh design allows it to be folded and reduced in diameter, and then delivered to the blood vessels or digestive tract through a catheter, and released at the affected area, using its own superelastic self-expansion to be placed inside the duct.
High-hardness cobalt-chromium alloy stents can be used for thinner blood vessels in the coronary arteries near the heart. The alloy tube is not superelastic and needs to be expanded with a balloon before being placed in the blood vessel.
Nickel-titanium (nitinol) tubing is used to make stents because of its superelasticity, shape memory, and biocompatibility:
• Self-expanding
A nitinol stent is manufactured slightly larger than the target vessel and then released from a catheter to expand into the desired shape. This process is called “setting.”
• Thermal memory
The “thermal memory effect” of nitinol allows the stent to expand at body temperature and conform to the anatomy of the vessel.
• Biocompatibility
Nitinol is biocompatible and has corrosion resistance similar to other implant materials.
• Fatigue resistance
Nitinol stents are fatigue resistant and can withstand large recoverable strains.
• Kink resistance
The interwoven design of some nitinol stents makes them kink resistant.
Nitinol stents are used to treat a variety of conditions, including: femoropopliteal atherosclerosis, esophageal stenosis, and common femoral artery atherosclerotic disease.