3D-Printed Implant Could Help Bones Regrow

It provides a scaffold for the body to populate with its own cells

Illustration: Diana Quach
Sep 28, 2016 at 5:39 PM ET

A flexible 3D-printed material may someday be able to replace large areas of damaged or missing bone, according to a new study.

As anyone who has broken a bone can tell you, these injuries take a while to heal. But if a patient needs a large area of bone replaced, either due to a traumatic injury or a birth defect, the body can’t replace the bone cells as easily on its own, and the person typically requires an implant. Some can get a graft of bone from another part of their body, but that can leave the original tissue more vulnerable to injury and can look strange, especially if the graft is going into the face or head. Other implants, from cadavers or made of synthetic products, are sometimes too brittle to be shaped to fit the area that the patient needs.

Now researchers have developed a type of synthetic bone that can help the body regrow bone itself. The material, called “hyperelastic bone” or HB, provides a scaffolding for the blood vessels and minerals that make up real bone to populate; because HB is made of biodegradable and biocompatible materials, it eventually just dissolves away as the body’s own tissue replaces it without causing inflammation, its creators claim. HB is made using a 3D printer at room temperature, which means it’s cheap to manufacture, simple to make into any shape, and relatively easy to create in mass quantities.

HB has a few properties that make it work well. First, the ink used to print the implants is made of hydroxyapatite, a mineral found naturally in bone, and a biodegradable compound called polycaprolactone that make it softer and compatible with the body. The second is the architecture of the printed product — it has a triangular honeycomb structure that makes it strong enough to bear about 150 pounds without bending, but leaves enough holes to make the material flexible while still allowing space for the body to use it as a scaffold to regenerate its own bone. The design also means that surgeons can shape the material to fit into the patient without weakening it, and that HB could have a long shelf life that would enable it to be shipped to high-need regions and countries.

To be sure that HB works as they expected, the researchers performed several experiments on animals, according to the study published Wednesday in the journal Science Translational Medicine. They implanted HB in the spines of two mice. They also tested HB as a replacement for part of the skull of a macaque monkey. In both experiments, after eight weeks in the mice and four in the monkey, the implanted HB was connecting well with the surrounding bone and was being populated by the body’s cells, all without eliciting an immune response.

“This could be the next breakthrough when it comes to regenerating bone and bone defects,” said Ramille Shah, a researcher in materials science and engineering at Northwestern University and one of the study authors, said in a press conference. The researchers called their results “astounding.” 

The researchers still have a number of questions to answer before HB can make its way to human trials. They need to better understand just how the material works in humans, how long HB can last on a shelf before it’s implanted, to increase its loading capacity, and to scale up production. They plan conduct tests in larger animal models before starting clinical trials in humans, which they hope to have under way in the next five years.