3D-Printed “Bone” Mends Injuries in Animals

Researchers say their hyperelastic 3D-printed "bone" may be used within five years to treat human injuries. | Science/ AAAS

Custom 3D-printed synthetic bone that can spur new bone growth successfully repaired the spinal cord and skull in animals, according to a study in the 28 September issue of Science Translational Medicine. The implants could help treat a wide range of bone injuries, including spine, dental, facial, pediatric, and sports injuries.

"Within five years we hope to get these in patients," said Ramille Shah from Northwestern University at a 27 September press teleconference. "Ideally, it would be great if we could have these printers in a hospital setting where … they can then make patient-specific implants that day, within 24 hours."

The synthetic bone may also offer "off-the-shelf" products that can be easily and rapidly deployed in the operating room, especially in developing countries, according to Adam Jakus, also at Northwestern University. "[There is a] huge potential for scaling it at relatively low costs compared to most medical materials," he said.

Synthetic bone grafts currently in development are often too brittle to be shaped and handled by surgeons, risk being rejected by the immune system once inside the body, or may be too expensive or difficult to manufacture for widespread use.

To overcome these limitations, Jakus and colleagues took advantage of 3D-printing technology to create hyperelastic "bone," a biomaterial made of polymer and ceramic containing a mineral found in teeth and bones. Both polymer and ceramic are currently used in medical devices from dental implants to sutures. Because the material is highly flexible, it can be printed into many shapes and cut, folded, and sutured to snugly fit a patient's injury.

The implant successfully healed a spinal cord injury in rats and a skull fracture in a monkey, regenerating bone without adding proteins usually needed to coax bone growth. The synthetic material quickly integrated with the surrounding tissue and eventually broke down and was replaced by new bone.

"I was surprised that just these two simple materials — really, these synthetics — when we produce them in this way, they have in addition to these great mechanical properties this incredible biological response," said Jakus.

The animals showed no signs of infection or other side effects. Shah noted that they could add antibiotics to the implant to reduce the risk of infection, or proteins to further enhance bone formation.

"Because of the versatility and properties and the ability to print hyperelastic 'bone' in different forms — anywhere from large sheets to hollow or dense structures to simple or complex structures — we envision this material to be used in a variety of different orthopedic applications from spine, to fractures, to sports medicine injuries," said Shah.

One of the first applications in the clinic Shah hopes to test is pediatric craniofacial surgery, where the implant can grow with a child. Children born with facial bone defects, especially in developing countries, are usually treated with an implant using a piece of bone taken from the patient's own hip bone or rib.

"We hope that because the hyperelastic 'bone' is scalable and at a lower cost, that it would be accessible to those types of patients," said Shah. "So that indication will make a huge impact, especially when it's a very aesthetic type of defect that if you get it right, you can make a huge impact on the quality of life of both children and adults."

[Credit for associated image: Adam E. Jakus, Ph.D.]