Every year, about 280,000 patients around the world undergo heart valve surgery, and the number of patients requiring heart valve replacement is expected to triple by 2050. Many of those patients are children with congenital heart conditions, and while heart valves can be replaced with bioprosthetic and mechanical valves, pediatric patients present a special challenge. As children grow, they outgrow their prosthetics, whether that’s a hand or a vascular stent.
3D printing has shown itself to be a promising technology for creating customized stents, but a group of researchers from the Eindhoven University of Technology is working on developing something even better – stents that expand as the patient grows, and that biodegrade over time. In minimally invasive heart valve implantation surgeries, stents are critical to support the prosthesis, but they’re only required until the new heart valve is fully integrated into the body. The metal stents that are typically used currently, however, remain in the body forever, even though they’re no longer useful and can even cause complications such as hyperplasia.
Furthermore, the metal stents are incapable of expanding as the patient grows. In a study entitled “Computationally Designed 3D Printed Self-Expandable Polymer Stents with Biodegradation Capacity for Minimally Invasive Heart Valve Implantation: A Proof-of-Concept Study,” the researchers discuss an alternative: 3D printed, bioresorbable stents that are capable of self-expanding.
“Bioabsorbable polymers, broadly investigated for their applicability in stent devices, are an attractive option,” the researchers state. “These materials are not only of interest due to their short-term presence but also because they might enable other benefits, such as low late thrombus formation and less interference with minimally invasive techniques such as magnetic resonance imaging.”
To design the 3D printable stent, the researchers made a finite element computational model of a nitinol (nickel titanium) stent. The physical prototype was 3D printed on a MakerBot Replicator 2x, using a flexible filament. The 3D printed stent was then subjected to a number of crush and crimping tests, as well as accelerated degradation tests to determine how biodegradable it was.
Although it was just a proof of concept, the study showed that 3D printing has promise as a method of fabricating expandable, bioresorbable vascular stents. Much more research has to be done, however, to find an ideal material and printing method. The polymer used for the proof of concept was not biocompatible, so a priority for further research is to find a biocompatible polymer that can be successfully 3D printed or otherwise fabricated with the required properties of degradability and expandability.
“In this proof-of-principle study, it was shown that computational-based 3D printed self-expandable and biodegradable polymer stents, with a reasonable degree of plastic deformation and RFs comparable to nitinol stents, can be successfully designed,” the researchers explain. “The computational simulations have demonstrated the capacity to build models with realistic outcomes, based on uniaxial material characterization. In addition, the FDM 3D printing technique is a promising manufacturing technique to translate computational models into physical prototypes that can be used to assess the mechanical performance of stent designs. Furthermore, the copolyester materials used in this study have shown to possess biodegradation potential via hydrolysis.”
The research paper was authored by María Sol Cabrera, Bart Sanders, Olga J.G.M. Goor, Anita Driessen-Mol, Cees W.J. Oomens, and Frank P.T. Baaijens. You can read the full study here. Discuss in the 3D Printed Stents forum at 3DPB.com.
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