3D printing aids growth of jawbone patch in patient’s rib

Three-dimensional printing is being tested for use in craniofacial reconstruction by growing a patch in another part of the body.

Rice University bioengineers have developed a technique to grow live bone to repair craniofacial injuries by attaching a 3D-printed bioreactor, or a mold, to a rib.

Researchers at Rice, The University of Texas Health Science Center at Houston (UTHealth) and Baylor College of Medicine conducted the study, and the results appear in the Proceedings of the National Academy of Sciences.

The 3-D printed mold acts as a scaffold and is infiltrated with stem cells and blood vessels, and is eventually replaced with natural bone, which becomes a custom-fit piece that can be used to repair the injured area in the jaw.

The two-part repair also involves preparing the area of the jaw to accept the bone grown on a rib.

The technique is being developed to replace current reconstruction techniques that use bone graft tissues harvested from different areas in a patient, such as the lower leg, hip and shoulder. The goal of the new approach is to take advantage of the body’s natural healing powers.

“A major innovation of this work is leveraging a 3D-printed bioreactor to form bone grown in another part of the body while we prime the defect to accept the newly generated tissue," said Antonios Mikos, a professor of bioengineering and chemical and biomolecular engineering at Rice and a member of the National Academy of Engineering and National Academy of Medicine.

"This study demonstrated that we could create viable bone grafts from artificial bone substitute materials,” says Mark Wong, co-author of the article and chair and program director of the department of oral and maxillofacial surgery with the School of Dentistry at UTHealth. “The significant advantage of this approach is that you do not need to harvest a patient’s own bone to make a bone graft, but that other non-autogenous sources can be used."

To prove the concept, the researchers made a rectangular defect in the mandibles of sheep. They created a template for 3D printing and printed an implantable mold and a spacer, both made of PMMA, also known as bone cement. The goal of the spacer is to promote healing and prevent scar tissue from filling the defect site. They removed enough bone from the animal's rib to expose the periosteum, which served as a source of stem cells and vasculature to seed scaffold material inside the mold.

The mold stayed in place for nine weeks before removal and transfer to the site of the defect, replacing the spacer. In the animal models, the new bone knitted to the old and soft tissue grew around and covered the site.

"We chose to use ribs because they're easily accessed and a rich source of stem cells and vessels, which infiltrate the scaffold and grow into new bone tissue that matches the patient," Mikos says. "There's no need for exogenous growth factors or cells that would complicate the regulatory approval process and translation to clinical applications." Additionally, multiple patches of bone can be created on several ribs of one patient.