Cynthia Chestek, Ph.D., Paul Cederna, MD
Every day in the US, 507 people lose a limb; while, 1000 children per year are born with limb defects. The use of prosthetic devices may determine whether persons with amputations return to work. Advanced prosthetic limbs now provide motorized joints with fine controls and sensorization similar to normal limbs (e.g. iLimb). However, the reliability of methods to control these limbs suffers from lack of suitable transduction of natural signals. Residual peripheral nerves continue to naturally conduct native control and sensation signals through their pathways that are anatomically understood. Current methods for controlling prostheses include capturing muscle signals with skin surface electrodes or capturing nerve signals with nerve cuff electrodes or nerve implanted wire electrodes. These three methods have problems because signals lack clarity, reliability, and amplitude. These interfacing methods are not intuitively based on the anatomical nerve functions. Thus users are trained over 6 to 9 months to continually anticipate how activation of one body area will make the prosthetic device move.
Cindy Chestek, Ph.D., collaborating with Paul Cederna, MD, and Melanie Urbanchek, Ph.D., with their colleagues developed the Regenerative Peripheral Nerve Interface (RPNI) as a method of recording signals that are two orders of magnitude larger than signals recorded from nerve fascicles. This is done by grafting small pieces of autologous muscle tissue to the ends of residual nerves. The muscle becomes reinnervated and then acts as an amplifier for the nerve signals. The amplified signals are then detected by a small implantable device then precisely records the signals sent through only the connected nerve fascicle. Receivers that translate the recorded signals and interface with a prosthetic device are housed within the prosthetic socket. Thus, this technology has promise to allow patients to control existing prosthetic devices without continuous and mentally demanding training.
The RPNI team is participating in the Coulter program for the third year. In the first two years of the project, they obtained compelling safety and efficacy data from 2 nonhuman primates who successfully used RPNI signals to control the fingers of a prosthetic hand. During this year, the first in human experiment will be conducted.
Link to technology at UM Tech Transfer: https://inventions.umich.edu/technologies/4889_a-living-biosynthetic-peripheral-nerve-interface or email Thomas Marten ([email protected]) for more information.