PRINTING PROSTHETICS
High-tech 3-D process to make custom-fitted devices more affordable is being studied.
Researchers at the University of New Mexico’s Department of Orthopaedics & Rehabilitation are studying how to use 3-D printer technology to create low-cost artificial hands and fingers for pediatric patients who quickly outgrow their custom-fitted prosthetics.
Every prosthesis is individually fitted to the wearer, so growing children may need a new device every six to 12 months.
Since a basic claw-type prosthetic hand costs from $7,000 to $10,000, lowering the cost would be very beneficial for families, said Dr. Selena Silva, interim medical director of Carrie Tingley Hospital.
Dr. Deana Mercer, a pediatric hand surgeon at Carrie Tingley, and Christina Salas, assistant professor and director of UNM Orthopaedics Biomechanics & Biomaterials Laboratory, both hope that prosthetics produced by a 3-D printer could bring the basic cost of producing one down to less than $200.
“Christina and I have been working on trying to figure out how we can address the need for prosthetics for kids over at Carrie Tingley, and this came up as a possible solution to that problem,” Mercer said.
Carrie Tingley serves more than 300 pediatric patients who need an arm or hand prosthesis because of a congenital defect or amputation.
Carrie Tingley Hospital Foundation provided $15,000 in funding for a one-year study and testing began in mid-June. A team of medical students, residents and engineering students, from bachelors up to post-doctorate level, is helping with the research project.
The 3-D printer feeds a polymer thread (that looks similar to those used by weed whackers) through a nozzle and melts it so that it can be laid down in a pattern created by a computer program. The process takes several hours.
So far, they have created about seven prototype hands that are now being tested.
“The first phase is for us to investigate different configurations of the hand and different orientations for the fingers to make sure that we can actually simulate a human hand,” Salas said.
The next phase will be mechanical testing to determine strength, flexibility and grasp force, she said.
For example, Mercer explained, the grasp force needed to hold a plastic bottle of water is different from that needed to hold a hammer. “The balance of actual force applied across the fingers is pretty delicate,” Mercer said.
The 3-D printed prosthetics are mechanically activated, which means the
wearer must flex muscles of their existing limb to open and close the fingers. They are attached by adjustable straps, which can accommodate the wearer’s growth.
Salas estimates that, with the polymer-using printer they are currently using, it costs less than $50 to print each one.
Salas soon plans to buy a more sophisticated printer costing about $9,500 that can use carbon fiber, fiberglass and nylon materials — which can create prosthetic hands with greater pinch strength capabilities. She estimates it will be able to create a prosthetic hand for between $150 and $200.
Salas hopes to be able to start testing the devices with patients in Mercer’s clinic by early next year.