By Published: Nov. 18, 2019

Doctoral student Joshua Tacca works with study participant in lab

Many people in developing countries who have lost a limb live with a common problem: They have no prosthesis. 

Josh Tacca, a doctoral student in mechanical engineering, traveled to Quito, Ecuador, last year and saw the great need of amputees to find prosthetics with well-fitting sockets.

Tacca, whose research focus is on biomechanics and prosthetic devices, worked with the Range of Motion Project (ROMP) for his practicum, which is one of the requirements for the Graduate Certificate in Global Engineering from the Mortenson Center in Global Engineering at CU Boulder.

“Most of the world has a lot of need for prosthetic care,” Tacca said. “There’s a severe lack of access in many parts of the world. And if there is care, it’s only in major cities. And the care is very expensive. ROMP is working to help get access to prosthetic care to people who need it.” 


I envision we could reach a lot more people if we could go into the field to reach them. We could scan the limb in the field, send back the information to the prosthetists in a central location, print it and then send the prothesis to the person.”

ROMP is a nonprofit organization that provides prosthetic and orthotic care to people without access to these services. ROMP partnered with tech startup Tukuna to develop and test a 3D printer filament made from 100% recycled plastic bottles, which could be made into limb sockets. The plastic bottles are collected by people in Quito who pick them up from the streets and dumpsters and sell them to Tukuna. 

The socket wraps around the limb and must be fitted for each individual. Since the residual limb inevitably changes shape over time, the prosthetic leg socket will lose its fit. Patients may need several adjustments to the socket over time. For amputees living in developing countries, traveling to clinics specializing in this work can be difficult.

Amputation is more prevalent in developing countries where high-quality, consistent health care is often lacking. Access to rehabilitative services and technology is minimal. Only one in 10 people in need of assistive devices such as prostheses and orthoses have access to them, according to the Standards of Prosthetics and Orthotics at the World Health Organization.

Traditionally, fitting a socket uses a great deal of labor and materials. Using a 3D scanner and 3D printer speeds the process. 

After a 3D scanner creates an image of a patient’s residual leg, a computer model is modified to make a digital socket that is then sent to a 3D printer. After plastic bottles are shredded and melted, extruded polyethylene terephthalate (PET) plastic is used to make a filament, which the 3D printer uses to make the individualized socket. 

While in Quito, ROMP held weeklong clinicals when amputees traveled to the clinic—some making an arduous journey from many miles away—to have the prosthetists fit them with prosthetic legs. Although the prosthetists were from Ecuador or otherwise fluent in Spanish, Tacca was not as fluent. In the rush of all the patients the prosthetists were meeting with, it was difficult at times for Tacca to ask questions and get all the information he needed to make modifications. To speed things along, he standardized the way information was gathered from the patients.

He also determined the 3D settings and would troubleshoot the printing process. The method they used for making a socket started by scanning the patient’s limb. Then they would modify the digital model of the leg, create a digital socket, print the socket out of recycled plastic, prepare the socket (sanding, buffing, adding a valve, etc.) and fit it to the patient.

By adjusting printer settings, prosthetists were able to obtain consistent 3D prints. Tacca standardized operation procedures, from scanning to modifying to fitting the socket.

Doctoral student Joshua Tacca at computerDoctoral student Joshua Tacca works with study participant in lab

“It’s difficult for people to travel to the clinic,” he said. “I envision we could reach a lot more people if we could go into the field to reach them. We could scan the limb in the field, send back the information to the prosthetists in a central location, print it and then send the prothesis to the person.”

When Tacca was an undergraduate at Vanderbilt University, he worked in a lab helping researchers develop prosthetics. Patients became excited when they got to try out the new devices. That inspired Tacca to come to CU Boulder to pursue that area of research. 

The skills and knowledge he learned in classes at the Mortenson Center for Global Engineering and in the Applied Biomechanics Lab were helpful for his ROMP internship. 

Tacca is working on projects in the lab of Assistant Professor Alena Grabowski in the Applied Biomechanics Lab. He’s processing data for a study that examined how the biomechanics and gait symmetry of sprinters with unilateral, below-the-knee amputations changed when running with different stiffnesses, heights and models of running-specific prostheses. And he worked on a pilot study to see how subjects with unilateral, above-the-knee amputations walked across different slopes and at different speeds when using a standard suction prosthetic socket compared to the way they walked using an adjustable socket.

“I am starting to work on a project with the Department of Veterans Affairs that will be my main project over the next few years,” Tacca said. “For that project, we are examining walking with a powered ankle prostheses attached to a passive foot. We plan to systematically determine the effects of changing the power supplied by the prosthesis and (whether) the stiffness of the passive foot affects subjects’ biomechanics, muscle activity and metabolic energy consumption when walking at a range of speeds.”

Tacca’s first-hand experience this summer in Quito emphasized the importance of work conducted by organizations like ROMP for people with limited or no prosthetic and orthotic care.

“I’m not totally sure about my career path yet,” Tacca said, “but right now I think I would like to pursue an academic role where I would be able to continue conducting research on biomechanics and prosthetic devices. I also think I would like to incorporate international development projects, like the one I did with ROMP, into my career path.”