Can We Really 3-D Print Limbs for Amputees?

The pros and cons of printing prosthetics
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A 3-D printed prosthetic hand (John Biehler/flickr)

For the approximately 1.7 million people in the United States living without one or more of their natural limbs, the process of acquiring a prosthetic one is exhausting. It’s a drain on time and money, involving mold fitting, laser body scanning, and hours upon hours in prosthetists’ offices.

But many of the approximately 34 million people around the world living without a natural limb don’t have access to this process at all.

The motivation to research and create more advanced prosthetic limbs is not financial. The money poured into research isn’t often recouped, simply because there aren’t enough customers. And it isn’t cheap for those customers, either.

3-D printing has the potential to change this.

When Scott Summit, the founder of Bespoke Innovations, started researching 3-D prosthetics six years ago, you had to go to Los Angeles to get a 3-D body scan and it cost about $800. Summit has been working for the past six years to reach a point where fully 3-D printed prosthetics become an easy reality. Everyone I talk to about the intersection of 3-D printing and prosthetics mentions Summit as the definitive expert in the field, and he says we can, right now, create a prosthetic limb with an iPhone and a 3-D printer. “I would like to see the creation of a prosthetic limb to be a viral app that’s usable by everyone,” Summit says.

The technology exists. Unfortunately, it costs a boatload of money.

3-D printing is, in layman’s terms, the ability to take a digital model and “print” it in all its three-dimensional glory. Generally, this process uses plastic as a medium, though it also works with metal and even biological material (though this is a slightly different process). 3-D printing offers higher customization of geometric models than ever before, and its nature allows for more trial and error in the actual creation process, since it makes prototyping cheap and quick.

The Media Hype

The Internet is full of stories about amputees creating entire prosthetic limbs in their homes, using a MakerBot Replicator-type home 3-D printer, but this is an extreme anomaly.

Jon Kuniholm, who lost his right arm to an IED as a Marine in Iraq, finds the media hype particularly egregious. Kuniholm founded The Open Prosthetics Project, a non-profit open-source collaborative resource for innovations in prosthetics, and he’s given several Tedx talks about the pros and cons of advancing of this technology.

Most prosthetic limbs are composed of two halves: the replacement limb and the part that connects with the body (generally called a socket). These parts are often made of a combination of materials from metals to plastics to electronics, which presents a problem for 3-D printing, which currently can only print one material at a time. The other issue 3-D printing faces is the connection to the body.

“The idea is—you’re trying to securely attach a hand or a foot or whatever to somebody’s skeleton—which is inside their body—through the soft tissue that’s still around it without damaging that soft tissue or it being uncomfortable,” Koniholm says. “Most of the time, a surface scan of somebody’s body isn’t going to create something that is going to be useful, because it has to interact with the bony part that’s inside.”

Generally, doing this requires that a plaster mold be made of the stump to capture its geometry. While a high-end laser body scanner, such as the one Summit remembers in Los Angeles, can do this work, Koniholm doesn’t think there is necessarily an advantage to it.

That said, scanners can help figure out the geometry of prototypes, which can then be created using a 3-D printing.

Prototyping

“If someone needs a prosthetic, then they’ll typically have another limb that’s intact, and they’ll use a white-light scanner or laser-based scanner to capture their intact limb and scan it to create their other limb,” says Rob Connelly, president of FineLine Prototyping. One of the advantages of 3-D printing is the absurd amount of customization available for the visual aspect of a prosthetic limb. While scanners vary in resolution, some exist that can “get down to even the fingerprint level,” Connelly says, allowing for a near-exact replica of an amputee’s remaining limb.

“There is a tremendous amount of engineering that goes into any prosthetics,” as Connelly says, but 3-D printing can still help create prototypes as engineers move toward an end goal.

For example, in 2009, then-25-year-old Joel Salder was honored by TIME for having one of the best 50 inventions that year—a prosthetic knee that only cost $20. The Stanford University Bio-X fellow used 3-D printing “to find out what forms work really well for a knee joint” when creating the JaipurKnee.

That’s one of the biggest advantages of 3-D printing, the ability to quickly print highly customizable forms. This opens the practice up to mechanical extrapolations, such as producing cheaper components for traditional prosthetic limbs.

Take Willow Wood, a company that produces prosthetic limbs and components. “We can print out a socket that can be used definitively, but attached to that socket is generally some sort of suspension device,” says director of research Jim Colvin. “To print that [component] in the same printer is not possible today.… You’re trying to replace a part of the body, and that part of the body isn’t homogenous.”

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Travis M. Andrews is a journalist based in Washington, D.C., and New Orleans. His has written for SalonThe Washingtonian, and The Washington Post Express. He is a contributing editor for the NBC website DVICE.

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