Sep 9, 2015 | By Kira

Researchers at MIT’s biomechatronics group are developing a non-invasive tool that can sense the soft-tissue properties in human limbs, measuring which areas are softer or harder due to bones, muscles or nerves. This data can then be used to 3D print custom sockets for prosthetic-wearers, greatly decreasing the pain and discomfort associated with traditional, hand-made models.

The tool, designed by PhD candidate Arthur Petron and his MIT team, is known as the FitSocket. Traditional sockets—the cup-shaped part of a prosthesis that attaches the amputated limb to the rest of the device—are generally made by hand, using plaster molds to measure the end of the patient’s limb. The process can take months, and is far from perfect. Most prosthetists try to mold the socket so that it makes minimal contact with the hardest parts of the limb in order to decrease stress and discomfort. Ironically, with the soft areas bearing most of the weight, the wearer actually experiences more pain.

The FitSocket robotic socket measurement device uses a different approach by digitally capturing biomechanical stiffness properties and using the data to rapid-prototype dozens, if not hundreds, of socket designs with rigid, spatially variable stiffness. The 3D printed models, which take minutes instead of months, distribute the load of the prosthesis across the entire surface of the limb, with the hardest part of the socket corresponding to the softest part of the limb and vice versa. The response from many trial patients has been overwhelmingly positive, with one patient describing it as “walking on pillows.”

Digital maps showing the softness and stiffness in a patient's limb

Chris Ahern, who lost most of his leg below the knee in a motorcycle accident, is one of the six early test patients eager to experience the FitSocket’s promise of comfort and increased mobility. His existing socket is a source of soreness and discomfort: “every single socket I’ve had, I’ve always had to work out the kinks,” he said, showing his original prosthetic. “I’ve had this socket for a year and a half, and I’m still having problems with it.”

Chris Ahern pictured on right, with MIT researcher taking measurments. Via Boston Globe

In the video, a patient is shown placing his limb inside the circular device while 14 extendable indenters gently press down on his leg. While it may look like a futuristic torture device, each extender is carefully measuring the surface shape of the limb, as well as how much force it takes to push the tissue at each point, taking into consideration the muscle, bone and nerves below the surface. The process is repeated up to 100 times in order to get the most accurate data possible for each individual patient. The measurements are then sent to MIT’s high-end 3D printers and are made from resin with variable degrees of hardness.

So far, Petron has his team have used their technique on six patients and tested them successfully in experimental conditions at MIT labs, however they plan to expand their study with a larger trial of patients and more rigorous testing conditions to see how they hold up during sports or even dancing. So far, potential flaws include the possibility that the resin used during printing wears down too quickly, however through testing, more effective materials could be found.

As the MIT researchers see it, the FitSocket could hold the key for prosthetic-wearers such as Arhem who are struggling with their current devices, but that’s not all Petron has in mind. When he graduates from MIT this winter, he plans to apply the FitSocket research to consumer-oriented technology beyond prosthetics, such as customized shoes, backpacks or seats for high-end vehicles. “We’re treating the body as a mechanical thing, because it is,” he said. “I want to understand the biomechanical properties of the tissue.”

In the meantime, Petron’s collaborations Prof. Hugh Herr, Prof. Neri Oxman, Roy Kornbluh (SRI), Elizabeth Tsai, and Zjenja Doubrovzki will continue their FitSocket and 3D printing research at MIT with the goal of developing more comfortable, better-fitting wearable devices.  



Posted in 3D Printing Applications



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a.kurdstani wrote at 4/7/2018 7:53:40 AM:

thank you for all those hardships you take to heal souls,

Gabriel Hope wrote at 4/7/2016 9:42:09 PM:

Wonderful and helpful tool

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