Inside The 3-D-Printed Limb Factory

Making the fake parts is easy but getting these limbs in the right hands takes a cultural, not just logistical, shift.

Inside The 3-D-Printed Limb Factory
A foot and trans-tibial alignment module from the International Committee of the Red Cross (ICRC) [Photos: courtesy of ginger coons]

Inside the University of Toronto’s brutalist concrete library, there is a room filled with human limbs. Not real limbs, but 3-D-printed lower-leg prosthetics. They litter the Faculty of Information’s Critical Making Lab, a tiny neon-red leg perched on a book shelf, and larger, white, adult-sized calf lying beside a beat-up MacBook Pro.


Ginger Coons, a PhD student who prefers her name rendered as “ginger coons,” picks up another limb (this one, green) and explains how each one is different. Although the latest legs have exceeded all expectations in stress-testing–the 3-D-printed plastic is about as strong as a traditional prosthetic-–coons and associate professor Matt Ratto have yet to find the perfect thickness, the perfect fill, that they’re certain will reliably support a person’s weight.

But with each iteration, they’re getting closer to their goal: a relatively simple, low-cost process for scanning, modeling, fabricating and assembling a 3-D-printed lower-leg prosthetic for use in developing countries. Everything will be tested for the first time at a Ugandan hospital, the Comprehensive Rehabilitation Services for Uganda (CoRSU), next month.

The project, led by Ratto, has been in development since July 2013. But Ratto and coons aren’t simply putting their designs, software and tutorials online and calling it a day: Just because something is available in theory doesn’t automatically make it accessible to all. (Linux, anyone?)

Like a whole cadre of other prosthetic researchers and makers, they are interested in breaking down the process, figuring out how to turn 3-D printing into something self-sustaining, adaptable, and easily taught.

A socket in progressPhoto: courtesy of ginger coons

“The social relationships [between] these things matter a lot. And these things have got to be created, developed, made to be sustainable as much as the tech,” Ratto told Fast Company in an interview. “In fact you can’t even differentiate, you can’t even separate the tech from the social. They are irretrievably interwoven together. And I think this is the biggest problem with these kinds of projects, and with technology more generally.”

Unlike many other 3-D-printed projects, prosthetics don’t exist in a vacuum. You can’t just upload a design to Thingiverse—the popular online file repository for 3-D objects—and expect to change the world. “I think one of the things we take for granted when we talk about the availability of technology is that not everyone’s infrastructure is our infrastructure,” says coons.


That’s one of the realizations that led Rochester Institute of Technology research scientist Jon Schull to found e-NABLE, a network of “makers, engineers, medical professionals, tinkerers, teachers, students, artists, philanthropists, [and] parents” that design, customize, and fabricate 3-D-printed hand prosthetics for people with missing or deformed fingers and hands. The devices are especially useful for children, who tend to outgrow otherwise costly commercial prosthetics every few years.

Schull says that his group has convinced over 3,000 volunteers globally “to collectively work on the fabrication, as well as the dissemination, of what is really a new design and distribution channel that complements the existing medical and commercial channels.” In other words, e-NABLE is positioned to work alongside hospitals—most of which aren’t yet using 3-D printing in this way, but still have traditional prosthetics access and expertise.

Some volunteer their 3-D printers and printing materials to fabricate prosthetic hand parts, while other groups assemble the parts, and medical professionals often assist with ensuring the devices fit and function correctly. In December, Boy and Girl Scouts are volunteering to assemble hands at John Hopkins Hospital.

“While we’re doing a lot to make this easier and easier for people to do, there’s no particular reason to think that the person who needs one of these hands will also have the technical skills required to do design or customize or fabricate or fit one of these hands,” Schull explained.


That’s very much the case in Uganda, where Ratto and coons are planning to test their last year of work in a hospital setting. The aim is to simplify the process of scanning, modeling and printing process without taking away agency from hospital staff. Ratto demonstrated a software wizard written in Python and still under development that guides hospital staff through the scanning process with text and videos—using what is essentially the same sensor as a first-generation Microsoft Xbox Kinect–and then through the process of modeling the prosthetic itself. A clinician will be taught how to customize each prosthetic using a piece of software from project partner Autodesk (called MeshMixer) by building up the scan in certain areas to add relief where areas might be bonier. Afterwards, they will make a negative cast of the scan (all digitally, of course) and prints the prosthetic out.

3-D-printed sockets for trans-tibial (below the knee) prosthesesPhoto: courtesy of ginger coons

“The simplest way to do this would be for [the hospital] to send the scans to us. Or we set up a service bureau and we get trained prosthetics from here,” Ratto says.

“And it’s a lovely, warm, fuzzy non-profit effort that looks great for a lot of Canadian prosthetists. Like, I’m spending my spare time making legs for children in Uganda,” coons adds.

But the problem with that approach is it denies African hospitals the knowledge and expertise to develop these prosthetics themselves. It doesn’t build new infrastructure, but leverages existing networks. The idea, instead, is to train and empower—at first, by establishing CoRSU as a training center for other hospitals — rather than make developing countries primarily reliant on foreign medical aid.

Dr. Albert Chi, who is an assistant professor of surgery at John Hopkins Medicine and an e-NABLE volunteer, echoed that view. “We’re looking not only to help supply places in need but also to get them started so they can be independent,” Chi said. He is currently working to expand e-NABLE’s volunteer network overseas.

A previous prosthetics project, Project Daniel, bills itself as “probably the world’s first 3-D-printing prosthetic lab and training facility.” But the work being done at The Critical Making lab is arguably more complex—in particular, because the lower-leg prosthetics are load bearing. And Ratto and coons have global plans. The pair hope that, from the time the team establish their first 3-D-printing lab in Uganda next year, at least 65 working prosthetics will be printed and sent home with children over the following twelve months. And during that time, they’ll be figuring out where and how to expand next.


Ratto and coons know that, for this to work they can’t simply deploy copycat labs in new hospitals. There will have to be ongoing relationships between each site, where knowledge and learnings are fed back to the other locations and the Critical Making Lab’s home base–a network for 3-D prosthetic limbs.

“The next phase of this work is thinking about how the scaling works. Because you can’t scale out of a research lab. So this idea of a social innovation [or] social entrepreneurship company is what happens next,” Ratto said.

“And that’s going to be as interesting as the rest of it, to tell you the truth.”

*Update: An earlier version of this story incorrectly identified Matt Ratto as an assistant rather than associate editor. We apologize for the error.