For the more than 2,000,000 people in the US alone who have suffered an amputated limb or have had to have one removed for medical reasons, prosthetics have offered a solid, albeit limited, way of coping.
While the use of prosthetics dates back many centuries, recent years have seen a rapid improvement in the technology behind them, allowing for ever-increasing leaps in what the devices can accomplish.
Now, a team led by Assistant Professor Dustin Crouch seeks to unlock what would be a game-changing jump in prosthetic devices by using technology that has so far largely only existed as fantasy: bionics.
The key component of the research is what are called muscle-driven endoprostheses (MDEs), which are a type of prosthetic that is completely implanted under skin in a patient’s body.
“We want to physically attach prosthetic limbs and appendages to the muscles that remain in the residual limb after amputation,” said Crouch, who works out of the Department of Mechanical, Aerospace, and Biomedical Engineering. “Using the residual muscles and tissue will enable patients to do things that they cannot with current prosthetics.”
Many current prosthetics limit the variety of motions that patients can perform, one of the big things Crouch and his team most want to change.
For example hand replacements have typically allowed patients to control the speed of motion when opening and closing the hand. Controlling and feeling the firmness of grasps or very fine finger motions are difficult or impossible with current prosthetics.
By using the muscles that remain after amputation, the thought is that it would be possible to create prosthetics that approached the same mobility and dexterities as the original limb.
“Many amputees are able to remember how to control the muscles that used to be there, are able to ‘feel’ that control,” Crouch said. “Humans have a remarkable ability to modify how they coordinate their muscles. One aspect of implementing this will be getting amputees to relearn how to coordinate their muscles to directly control their new devices. We want it to feel as natural as possible.”
Another major advantage of the new technology is that it solves two complaints that often come up when people talk about their artificial limbs: weight and convenience.
Using Crouch’s approach eliminates a lot of the bulkiness associated with many current models since, muscles don’t need batteries or motors to operate.
Additionally, having the new devices connected to existing muscle means that people would have a more “natural” experience of their new appendage being with them and functionable at all times, instead of having to remove and reattach them as the situation dictated.
Crouch said he knew that having other viewpoints—especially those from a medical realm—would help, so his teamed formed accordingly.
Professor and Head of the UT Large Animal Clinic Science David Anderson, Professor of Small Animal Clinical Sciences Cheryl Greenacre, and Clinical Veterinarian Bryce Burton, all of the UT College of Veterinary Medicine, and Stacy Stephenson, a doctor at UT Medical Center, are all assisting on the project.
Like most scientific undertakings, the group has started at the small-scale side of things, beginning with prosthetic feet for rabbits.
Using synthetic tendons to attach muscles to a small prosthetic foot and ankle in the leg, the team will be able to get feedback from the foot, such as strength and reflexivity, that will help them design later models.
Eventually, the goal is to work up to human-based implementation, where, once again, the team will start small before building up to full-size limbs, likely beginning with individual fingers or toes.
Crouch said he hopes the work has advanced to that level well within the next five years.
“The whole goal of this is to improve outcomes for people who have undergone amputation,” Crouch said. “People have to change jobs, maybe even quit work altogether because of limb loss. This could drastically change lives for the better.”
As a sign of the importance of the work, the National Science Foundation selected Crouch for one of its prestigious CAREER awards, which go to up-and-coming faculty with ideas it deems important to humanity.