Researchers at Northwestern University have made a potentially huge medical advancement: 3-D printed bone.

According to a study in Science Translational Medicine, the team of researchers developed ink that can be used to print a synthetic bone material. The hyperelastic bone can be easily shaped, which means it can be customized to fit an individual patient.

Bone implants often require taking a piece of bone from elsewhere in the body, a process that can cause pain and other complications. And bones stabilized with metal braces or rods often mean additional surgeries for children who outgrow them.

By contrast, cells in the body respond to the hyperelastic bone and regenerate naturally, potentially avoiding the need to replace it in the future.

The material is made by combining hydroxyapatite, a calcium mineral found in human bones, and polycaprolactone, a biodegradable polymer that can be easily molded when warm but is hard at body temperatures. The hydroxyapatite encourages natural bone growth, so it can act as a brace for the already existing bone and a scaffold for new bone to grow around it.

The bodies of the rats used in the experiment didn't reject the material--never a given when a new material is implanted into the body.

To create an implant, the patient's body is scanned, and the scan is used to print the bone material in the necessary shape and size. The material can be used soon after printing, which means it's possible that hospitals and doctor's offices could have their own printers--allowing implants to be created and installed on demand. In a press release, Ramille Shah, an assistant professor at Northwestern and the study's lead researcher, said that turnaround times on implants could be less than 24 hours.

3-D printing for medical purposes is still a young field. While many scientists have the goal of producing 3-D usable printed organs and tissue, those results are likely still years away. Some startups, like Philadelphia-based BioBots, manufacture 3-D printers that produce living tissue and organ samples, but they're used for research and not to be implanted in human bodies. Some scientists have successfully produced prosthetic limbs, drastically reducing their cost for patients--especially children, who need to be re-fitted often.

In the press release, Shah said that the advancement "could change the world of craniofacial and orthopaedic surgery, and, I hope, will improve patient outcomes."