3D-Printed Hyperelastic Bone Will Change Medicine

Healing broken bones just got a whole lot easier.

Credit: Rahkendra Ice / A. Jakus et al. / Science Translational Medicine 

Broken bones are the bane of the medical profession, despite physicians’ best efforts to pump fractures full of expensive, growth-inducing chemicals and provide support. But when it comes to shattered skeletons, there ultimately isn’t much to do but wait. A bizarre new substance scientists nicknamed “hyperelastic bone,” however, is set to appease the impatient.

Imagine a broken arm, like Harry Potter’s famously Quidditch-battered limb in the Chamber of Secrets. Inside, one of the long bones is splintered in two. Without magical Skele-Gro to turn to, researchers at Northwestern University, publishing their study in Science Translational Medicine today, figured out how to patch the gap between those shards of bone using a substance they call hyperelastic bone — or HB for short. The squishy material gets 3D-printed into the right shape, then gets compressed and wedged into the space, where it will expand to fill in the nooks and crannies in the broken bone. Think of a scrunched-up marshmallow wedged into a crack.

Here's a close-up of a small region of the first several top layers of a 3D-printed sheet of hyperelastic bone.

[Credit: Adam E. Jakus, PhD

“Since it’s elastic it can be pressed into a defect in expand to mechanically fix itself into the space without glue or sutures,” Ramille N. Shah, Ph.D., the paper’s co-author and an assistant professor at Northwestern’s Department of Materials Science and Engineering said in a teleconference on Tuesday. Shah and his colleagues managed to create this substance out of the same stuff bone is made of: a mineral called hydroxyapatite, mixed together with binding agents that give the otherwise brittle substance bendable properties and unprecedented strength. In one experiment, they 3D-printed a section of a femur and it withstood a weight of 150 pounds before it started to give way.

Hyperelastic bone "sleeves" can be pulled around a human tendon to promote healing -- good news for athletes with torn ACLs.

A. Jakus et al., Science Translational Medicine (2016)] 

That in itself is an impressive feat, but the expandable substance does more than provide structure. Hyperelastic bone, largely composed of materials that occur naturally in the body (all of which are FDA-approved), provides physiological structure — a framework for the body’s cells to grow. Because it’s both biodegradable and, importantly, biocompatible, it integrates itself into the body, making it easier for blood vessels to pass through and cells to grow. Shah and his colleagues tested this property of the HB by seeding it with stem cells — cells that have the potential to specialize into any kind of tissue. What they found was remarkable: The stem cells planted on the HB not only multiplied but began to make bone, mining minerals from the HB itself as a resource. And the immune system, as far as their experiments have shown, doesn’t freak out when HB enters its turf.

Its ability to be 3D-printed make its applications pretty much limitless. If you, say, need a new skull, Shah and co. have got you covered:

A 3D-printed skull, made of elastic bone.

Adam E. Jakus, PhD 

Ditto an exact replica of a DNA helix:

Hyperelastic bone, a mixture of hydroxyapatite and stretchy binders, can be 3D-printed into any shape necessary to mend fractures.

Credit: Rahkendra Ice / A. Jakus et al. / Science Translational Medicine

While 3D printing is now commonly used in the medical field, Shah notes that the big upside to hyperelastic bone is that the “ink” used to print it isn’t prohibitively expensive, being “relatively low cost compared to most medical materials.” That means it’ll be easy to scale up, ship to hospitals equipped with 3D printers, and insert into broken arms, legs, and ribs across the planet.

Will it happen anytime soon? “Getting to that point there’s a lot of regulation and a lot of quality control that has to happen,” Shah notes. But if the evidence he’s shown is any indication of its potential, there’s little doubt it’ll be happening soon.

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