Researchers at the University of Toronto, in collaboration with Autodesk Research (Toronto, Ontario) and CBM Canada (Stouffville, Ontario) are employing 3D-printing techniques to produce cheap, fast, and easily customizable prosthetic sockets for use in the developing world. I was invited to check out the lab on behalf of Medgadget to get a better idea of what’s the latest in custom printed prosthetic devices.
Upon walking into the lab, I was greeted by clean, open spaces, and a room full of large futuristic boxes that resembled hollowed-out inkjet printers, whizzing back and forth as they constructed objects layer-by-layer. After being given a quick tour around, I chatted with Dr. Matt Ratto of Semaphore, and Dr. Ryan Schmidt of Autodesk Research, about their prosthetic socket project in Uganda.
Ben Ouyang, Medgadget: Where did the idea for this project come from?
Matt Ratto: We were approached by CBM Canada, an NGO that provides support for medical facilities in the developing world. One of their partner hospitals in Uganda, CoRSU (Comprehensive Rehabilitation Services in Uganda) had heard of 3D printing, and wondered if it could be used to serve their patient population better. In conversations with CBM Canada and CoRSU, we realized their biggest need was not prosthetics for arms nor hands, but for legs and mobility. They really wanted to restore mobility in children as early as possible to improve participation within their community and reduce their chances of becoming ostracized.
Medgadget: Can you quickly walk our readers through the creation of the customized prosthetic sockets?
Ryan Schmidt: We first create a 3D scan of the limb using an Xbox Kinect. We can bring that digital limb into Autodesk Meshmixer, smooth out the rough scan mesh, and use it directly to design the socket. We create a molded “bucket” around the limb’s contours, and can use Meshmixer to quickly push and pull parts of the design to modify its shape. In the end, the model is sent to a 3D printer, which prints the socket in a few hours using PLA (poly lactic acid), a thermoplastic that is easily modifiable with heat. This method can make a typical socket for under $10.
Medgadget: What user factors are you designing for in the socket?
Matt Ratto: One thing is the comfort and fit. Pressure on bony parts of the limbs can cause pain and discomfort. Anything that’s soft – that’s where you want the pressure. Meshmixer allows us to change the pressure points of the socket to design a fit around the leg that maximizes comfort. For example, we mold the rim of the socket to go below and under the patella. This redistributes the force of standing to the patellar tendon – which can take a lot of pressure – from some of the pressure that would otherwise go down to the tibia. We’re also developing ways to make the socket wrap around the bony condyles of the knee, so that the prosthetic can stay attached when the leg is lifted.
Medgadget: What benefits does this 3D printing method have over the traditional method?
Matt Ratto: The traditional method involves wrapping an amputated limb with a plastic mold to first create a negative cast. Once that dries, plaster is poured into the negative cast to make a positive cast, which serves as a representation of the actual limb. Finally, a socket is molded around the positive cast, and can be used upon curing.
Ryan Schmidt: The traditional method is very time-consuming, especially if iteration needs to be done. It’s a destructive process, so any modifications destroy the original molds, and that information is lost. The method we use with 3D printing allows for a quick scan to digitize the limb, simplifying the process. It allows for quick and non-destructive modifications.
3D scanning has become increasingly widespread, and the capabilities of 3D printers have been steadily improving. The missing piece now, and the novelty of Meshmixer, is the ability to deal with the data and models and link the scanning and fabrication.
Medgadget: How will you make this tool accessible to healthcare providers in third world countries?
Matt Ratto: There’s a need for at least 40,000 prosthetists and prosthetic technicians in the developing world that is completely unmet. The WHO estimated that in the next 50 years, they could train 18,000 to employ the traditional Red Cross’s negative/positive casting technique. Using that process alone, there’s no way to fulfill the need. The idea behind our system is to provide an alternative method, which facilitates the learning for the design and fabrication through the work of using it. Even for someone with limited or no training, it can produce a functional prosthetic.
We’re creating this tool to be used by people on the ground, the whole way through from scanning to modeling to 3D printing. We want to avoid sending the scans back to the developed world for analysis and design because we see that as a problematic, patriarchal relationship with the developing world. However, I think it would be possible for the scans and models to be shared online for collaborations and evaluations from anywhere around the world, to further facilitate the learning process for prosthetists.
Right now, we’re working on a software wizard to guide a user and prompt them for modification of the socket to make the process easier. As the users become more proficient with use, they can begin to explore and use the full functionality of the software underneath the wizard. We can do a general design of a socket in 10 minutes. We’ll be working with some prosthetists in Toronto to work out the initial validation soon, and we hope that in 6-8 months we’ll be able to get it out to Uganda.