When doctors repair broken bones or problematic joints, they often rely on ceramic or resin bone implants. But those have some downfalls: Because they’re rigid, they’re difficult for surgeons to customize to a patient’s body, and they are tricky to use in minimally invasive surgeries. The ideal would be a cheap material that would be bendable but would allow new bone to grow into its structure.

In a step toward that goal, Northwestern University researchers have developed a new ceramic-polymer blend that can be 3-D printed into various shapes and cut to fit. When implanted into experimental animals, replacement bones made of the material quickly integrated with the surrounding tissue, allowing real bone tissue to regenerate.

“It needed to have had the best properties of each of them, to maintain a balance between states of solid and liquid to be flexible or rigid, depending on what’s needed,” said senior author Ramille Shah, an assistant professor of material science and engineering at Northwestern University. “We combine the 3-D printing settings with the formulation in a way that brings out different properties in the materials.”

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Bones printed out of the material were as effective as the natural equivalent — a living bone with its minerals removed — in supporting spinal fusion in rats. Researchers also successfully used the printed bone to heal a skull defect in a rhesus macaque, with no signs of infection or other side effects. The findings were reported in Science Translational Medicine.

“This is one of the better formulations I’ve seen,” said Purdue University biomedical engineering professor Eric Nauman, who wasn’t involved with the research. But he said the new material still has a few drawbacks. “It’s too compressible to stand on its own. You would still have to incorporate big pieces of metal with it. But it’s a nice model for studying how bone adapts, and it might be good for soft-tissue repair, like in areas where ligaments meet bone.”

Shah said that her team’s next step is to test their material further.

“Right now we have to get more data, to be sure it works,” she said. “We’re testing it in cranial defects in rats, for example. And we’re still doing studies, with different formulations.”

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