Photograph of the FitSocket in use courtesy of Petron.
Researchers with the Biomechatronics Group within the Massachusetts Institute of Technology (MIT) Media Lab are working toward developing more comfortable, better-fitting prosthetic sockets. The FitSocket project, a robotic socket measurement device, uses 14 multiple linear actuators that press down on the patient’s residual limb to accurately detect and map areas of softness and stiffness; the device runs on an EtherCAT communication bus with PC control. With these data, the researchers computationally generate files that describe a socket based on the printable materials and their corresponding material properties. They can then 3D print full sockets and socket molds in order to make rigid, spatially variable stiffness, and spatially/temporally variable stiffness sockets.
“These sockets, made from different hardnesses of resin, do what traditional sockets cannot: distribute the load of a prosthetic leg across the entire surface of the remaining limb,” reported The Boston Globe.
“It takes under an hour from the patient arriving, changing into shorts, marking the testing locations, doing the measurement, and changing again,” said doctoral candidate Arthur Petron, one who is working on the project. “The PC controller is a graphical user interface program just like Word or MS Paint. I wrote the software so that there are buttons that tell the robot to take samples, calibrate force or position, or run one of various other functions. The socket itself takes about one-and-a-half days to print.”
The advantages of the FitSocket, Petron said, is that the loop between finite element simulations of residual limbs and indenter measurements of residual limbs can now be closed. “The system can provide repeatable, precise data to a computer model of the residual limb, then that model can be used to predict what the FitSocket will measure, thereby verifying the entire dataset.”
The FitSocket has been used to custom-print sockets for six patients, and the results have been positive, according to The Boston Globe article.
“The next step is to get this into a clinic,” Petron said.
