In trying to develop a new thumb prosthetic, Dustin Crouch and his team have called surgeons, therapists, and patients to understand what the current treatment and prosthetic options are for thumb amputees.
One conversation in particular stood out to Crouch, an associate professor in the Department of Mechanical, Aerospace, and Biomedical Engineering at the University of Tennessee. A sculptor from New York City had lost his thumb and lamented the prosthetic choices he’s been given.
Crouch told the sculptor about the technology he was developing, which would restore thumb function by providing accurate length, flexibility, skin coverage and potentially the sensation of touch. The technology is a revolutionary new type of implantable prothesis that is anchored into a bone, completely enclosed by skin, and connected and controlled by the patient’s own muscles.
“He shouted into the phone with excitement,” Crouch said. “He said he’s been asking his surgeon if something like this existed because his residual thumb length is so short that his prosthesis sometimes slips off. He said the loss of his thumb, especially as an artist, was emotionally a big hit for him.”
Opposable thumbs are crucial for dexterity and functionality. They play a crucial role in day-to-day life, allowing humans to grab, hold, pinch, and grip items. They provide humans with the ability to type, carry items, tie shoes, and button clothes. Most people don’t realize the importance of the thumb until it’s injured.
For amputees, current thumb reconstruction can involve transferring a patient’s healthy toe or finger to replace the missing thumb. Crouch’s technology restores shape, size, and function without having to remove another finger or toe.
“It would restore the length of the thumb, which is really important. If you don’t have a lot of length, you can’t grasp objects or pinch,” Crouch said. “For our device, you’d want the base joint preserved so you could still move the thumb around. You just won’t be able to flex. But according to our conversations with different surgeons and therapists, that will restore a lot of useful function.”
Marketing innovation
Crouch’s interest in prosthetics dates to his early years as a college student. On his application for grad school, his personal statement included that he would like to work on prosthetics for people in third-world countries. He held a postdoctoral position at North Carolina State University, where he spent three years working in a lab dedicated to prothesis control.
“I was able to meet people impacted by amputation and saw the struggles they faced,” Crouch said. “I got to see firsthand some of the increases in performance, but also some of the challenges. They don’t move naturally, and they can have errors in how they move compared to what the person wants. That can be very frustrating.”
Crouch knew there was a market for innovative solutions to help amputees restore their quality of life. Each year, approximately 5,000 to 6,000 people in the United States suffer thumb amputations, with an estimated 2 million people globally living with thumb amputation.
Crouch pitched his start-up idea, EndoThumb, to UT’s Office of Research, Innovation, and Economic Development (ORIED) for its annual Chancellor’s Innovation Fund awards. His team was selected to receive up to $50,000 to support commercialization and entrepreneurial efforts.
His team has also received grants from the National Institutes of Health (NIH) and National Science Foundation (NSF) to fund studies and further development of the technology. Earlier this year, Katrina Easton, a former postdoc in Crouch’s lab, was selected as a UT Research Foundation Entrepreneurial Fellow and will assist Crouch with developing EndoThumb.
Crouch has been collaborating on his prosthetic technology with David Anderson, associate dean for research and graduate studies at the UT College of Veterinary Medicine, and Stacey Stephenson, a plastic surgeon and assistant professor at the UT Medical Center.
“It’s been extremely helpful to have that ecosystem,” Crouch said. “They have been willing to offer their time and services because they believe in the project as well.”
Potential for growth
To prove the feasibility of enclosing a prosthetic into skin, Crouch has implanted the technology into animal models. The tests have so far been successful with a leg and foot.
“The studies proved the concept that we can implant a device like this at the end of a limb that has had an amputation and cover it in living skin and have that skin heal,” Crouch said. “The data so far suggests that animals were able to use it as a foot and ankle prosthesis so they could bear weight on it while they were moving around.”
A UT senior design team has spent the last few months working on a project involving a simple prototype as the EndoThumb with a bone anchor and a thumb tip that can be connected with a screw.
Crouch anticipates it will be two years until EndoThumb can conduct clinical trials and four years until it’s approved to sell. If approved, the simpler surgery required for the prosthetic will enable more medical centers to offer the procedure to patients.
Crouch’s long-term vision is to adapt the technology for other areas of the body, starting with small appendages like fingers, toes, hands, feet and eventually expanding to arms and legs.
“I am really excited about all that we’ve been able to accomplish over the last year,” Crouch said. “It feels like we are really gaining momentum with something that I hope can improve the quality of life for a lot of people.”
Contact
Rhiannon Potkey (865-974-0683, rpotkey@utk.edu)