A Colorado man made history at the Johns Hopkins University (JHU) Applied Physics Laboratory (APL) in June when he became the first person with bilateral shoulder-level amputations to wear and simultaneously control two of the JHU’s Modular Prosthetic Limbs (MPLs). Most importantly, Les Baugh, who lost both arms in an electrical accident 40 years ago, was able to operate the system by simply thinking about moving his limbs, performing a variety of tasks during a ten-day training period.
Baugh was part of an APL-funded research effort to further assess the usability of the MPL, developed over the past decade as part of the Revolutionizing Prosthetics (RP) program. Before putting the limb system through its paces, Baugh had to undergo targeted muscle reinnervation surgery during which nerves that once controlled his arms and hands are reassigned. After recovery, Baugh underwent training at APL on the use of the MPLs. First, he worked with researchers on the pattern recognition system.
“We use pattern recognition algorithms to identify individual muscles that are contracting, how well they communicate with each other, and their amplitude and frequency,” explained trauma surgeon Albert Chi, MD, who performed the procedure. “We take that information and translate that into actual movements within a prosthetic.”
Then Baugh was fitted for a custom socket for his torso and shoulders that supports the prosthetic limbs and also makes the neurological connections with the reinnervated nerves. While the socket got its finishing touches, the team had him work with the limb system through a Virtual Integration Environment (VIE), a virtual-reality version of the MPL.
The VIE is completely interchangeable with the prosthetic limbs and through APL’s licensing process currently provides 19 groups in the research community with a low-cost means of testing brain-computer interfaces. It’s being used to test novel neural interface methods and study phantom limb pain, and serves as a portable training system.
By the time the socket was finished, Baugh said he was more than ready to get started. When he was fitted with the socket, and the prosthetic limbs were attached, he said, “I just went into a whole different world.” He moved several objects, including an empty cup from a counter-shelf height to a higher shelf, a task that required him to coordinate the control of eight separate motions to complete.
APL’s Courtney Moran, CPO, who works with Baugh, said the research team was floored by what Baugh was able to accomplish.
“We expected him to exceed performance compared to what he might achieve with conventional systems, but the speed with which he learned motions and the number of motions he was able to control in such a short period of time was far beyond expectation,” she said. “What really was amazing, and was another major milestone with MPL control, was his ability to control a combination of motions across both arms at the same time. This was a first for simultaneous bimanual control.”
The next step, said RP Principal Investigator Michael McLoughlin, is to send Baugh home with a pair of MPLs so that he can see how they integrate with his everyday life.