Surgeons See Success with Experimental 3D-Printed Bone Grafts

Researchers have developed a 3D-printed synthetic bone that overcomes many of the shortcomings of current bone grafting materials. Surgeons successfully used the substance to fuse the spines of rats and repair a skull defect in a monkey, the researchers reported today in Science Translational Medicine.

The novel biomaterial is strong, elastic, and capable of helping the body regenerate new bone on its own. Most importantly, the material isn’t brittle, a property that could allow surgeons to trim a piece to fit the patient without it crumbling—a common problem with other synthetic bone constructs.

To achieve the effect, researchers used the right combination of starting materials for the ink and printed it at room temperature rather than with heat or lasers, explains Ramille Shah, principle investigator on the paper and biomaterials scientist at Northwestern University.

Shah’s team used a type of bioactive ceramic called hydroxyapatite—a material commonly used in attempts at regenerating bone—and added a polymer called polycaprolactone. Then, rather than using hot-melt or laser-based 3D printing, the team used a solvent-based, room-temperature 3D printing technique that relied on a unique combination of three solvents.

That improved the microstructure of the ink, says Shah. “It doesn’t dry out right away. It’s a little wet which allows each layer to adhere to the previous one,” she adds. The team dubbed their substance “hyperelastic bone.” The printer they used, called the 3D-Bioplotter System by EnvisionTec, is commercially available and costs US $250,000–$300,000, Shah says.

In the rat and monkey experiments, the printed scaffold integrated well into the animals’ bodies. Blood vessels moved into the porous material quickly, and the animals’ immune systems didn’t seem to reject the implant. Over time, the material is expected to biodegrade as the body’s cells naturally regenerate new tissue and replace the synthetic scaffold.

The substance could be particularly beneficial to children who need bone grafts, since it essentially grows with the child, says Adam Jakus, a postdoc in Shah’s lab and an author of the report.

Researchers have 3D printed bone-like material for other purposes, such as medical modeling. Paleontologists have 3D printed replica dinosaur skeletons and other scientists have created human skeleton replicas and biomimetic robot hands.

Implanting 3D-printed materials into the human body, however, requires orders of magnitude more testing and development. Shah wants to move the printed biomaterial into human clinical trials within five years. The U.S. Food and Drug Administration (FDA) has not yet approved a 3D-printed substance for use as a regenerative bone material, Jakus says. They hope hyperelastic bone will be the first.

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