Researchers at the Shiga Medical Center for Adults in Japan have developed biodegradable plastic stents for implantation in humans suffering from coronary artery stenosis, or constriction. The development was led by Hideo Tamai, who was searching for an alternative to the metallic stents currently used. While metallic stents have been used effectively for nearly 15 years, they can occasionally damage blood vessels. When used in children, they can come loose as the repaired vessel increases in size as the child grows. The stent developed by Tamai and his colleagues is made of a poly-l-lactic acid (PLLA) monopolymer that is 0.17-mm thick formed into a zigzag helical coil. The 12-mm long PLLA stent comes in three diameter sizes: 3, 3.5, and 4 mm. Lactic acid polymer is already used in other medical applications, such as binding broken bones and surgical sutures. Tamai says that stents are typically needed for only 6 months after implantation because the blood vessel strengthens naturally. The new stent is absorbed by the body in 18 to 24 months. In studies conducted at the center, patients with the plastic stents had a lower rate of restenosis than patients with metallic stents. "We expect that the PLLA stents will become another alternative for heart patients," says Keiji Igaki of Igaki Medical Planning Co., Ltd., which manufactures the PLLA stents. For more information, call Hideo Tamai at +81 77 582 5031, or fax at +81 77 582 5426; or contact Keiji Igaki at +81 75 594 5595.
Researchers at Lawrence Livermore National Laboratory have published two physics-based models for the selective laser melting (SLM) metals additive manufacturing process, so engineers can understand how it works at the powder and scales, and develop better parts with less trial and error.
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