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3-D Printed Scaffold Helps Grow Skull Bone

Ramille Shah

Ramille Shah (2014 photo, Northwestern University)

17 May 2019. A Northwestern University bio-materials lab demonstrated the growth of new bone in skulls of lab animals on scaffolds made with three-dimensional printers. A team led by biomedical engineering and materials science professor Ramille Shah describes its techniques in this month’s issue of the journal Plastic and Reconstructive Surgery.

The Shah lab in Chicago studies materials for 3-D printing for medical uses, but also with applications across many industries. In this case, the researchers investigated a material to help regrow bone in people with injuries to their skulls, often from trauma, requiring reconstructive surgery. Up to now, the best solution in these cases is transfers of bone material from elsewhere in the patient’s body, such as rib or pelvis, which may not be readily available. And even if available, it means another surgery and associated risks for a patient already with a serious condition.

The team, with colleagues from University of Illinois Health and Shriner’s Hospital in Chicago, tested a 3-D printed scaffold from a material called hyperelastic bone. This material is made largely of hydroxyapatite, a calcium phosphate compound similar in composition and stability to human bone. About 10 percent of hyperelastic bone is the bio-compatible polymer polylactic-co-glycolic acid, or PLGA, approved by FDA for drug delivery and tissue engineering. Thus the material offers both the strength and stability of natural bone, as well as flexibility to fit into irregular-shaped openings like those repaired in reconstructive surgery.

In previous studies, the material is shown to promote bio-activity and the ability to integrate with surrounding tissue. For this project, the Shah lab printed hyperelastic bone samples, 5 layers thick, in a tight lattice formation on its 3-D bioplotter system. From these samples, the surgical team cut out scaffolds to fill holes made in skulls of lab rats. For comparison, the lab printed a similar PLGA material, but without the hydroxyapatite. The surgeons implanted the hyperelastic bone and PLGA scaffolds into the rats’ skulls, filling the holes.

The researchers compared bone regeneration from hyperelastic bone scaffolds to conventional bone transplants in the rats’ skulls, as well as the PLGA scaffolds. After 8 weeks, skull bone tissue regrew from hyperelastic bone scaffolds in 74 percent of the volume as conventional bone transplants. After 12 weeks, bone regrowth volume was 65 percent of bone transplants. Bone growth from the PLGA scaffolds was no more than 20 percent at either 8 or 12 weeks. Scanning electron microscope images show fibrous and cellular formations developing initially around the hyperelastic bone scaffolds, leading to growth of new bone.

“Hyperelastic bone,” says Shah in a statement from Wolters Kluwer, publisher of the journal, “has significant potential to be translated to craniofacial reconstructive surgery, where the need for cost-effective bone replacement grafts is enormous.”

Shah and co-author Adam Jakus are founders of the 3 year-old company Dimension Inx in Chicago, developers of advanced inks for 3-D printing and additive manufacturing, the industrial form of 3-D printing. Among the company’s offerings are hyperelastic bone described in the article. Shah and Jakus are Dimension Inx’s chief scientist and technology officer, respectively.

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