helping patients with amputations
This innovative research is funded for a second year by the Frankel Innovation Initiative, a $20 million fund made possible by a generous donation from the Maxine and Stuart Frankel Foundation that supports the research and development of life-saving therapies at Michigan Medicine. This project was renewed based on the successful completion of the Year 1 milestones and Year 2 milestones proposed.
One in 190 Americans has an amputated limb, which can be devastating to their quality of life. The quality of prosthetic hand control has barely improved over the last century. Today’s surgical techniques and contemporary prosthetic rehabilitation approaches offer only limited functional restoration for individuals with upper limb amputations. Described as “degrees of freedom” or DOF, it is common for those with an upper limb prosthesis to only have a single DOF, limiting their dexterity with everyday tasks.
University of Michigan’s Paul Cederna, M.D., and Cynthia Chestek, Ph.D., have proposed a nerve recording solution applicable to virtually every person with an amputation. Currently modeled as a prosthetic hand, the U-M researchers have developed a regenerative peripheral nerve interface (RPNI) technique, in which a small piece of muscle is wrapped around the end of a severed nerve to amplify the signal of that nerve tenfold. The commercial device (in development as a take-home system) will consist of a small implantable recording device, an external smart socket that will receive and interpret signals from the implant to control the prosthetic hand, and a clinical programmer that a prosthetist can use to calibrate the system.
“Our goal is to create a system that is first effective in the lab, then in a take-home clinical trial, and ultimately in daily life,” says Dr. Cederna.
Commercializing this technology could mean a new, more modern standard of care for individuals with an amputation, which can improve prosthetic control while simultaneously treating phantom pain and neuroma pain.
“Participants to date have up to 12 implanted bipolar electrodes to record RPNI signals from the peripheral nerve to control a prosthetic hand,” notes Dr. Chestek. “So far, participants have successfully demonstrated many new capabilities, including continuous control of thumb position along two degrees of freedom.”
At present, commercially available prosthetic hands have a lack of control signals and are limited to a single degree of freedom in their movement.
The RPNI technique involves wrapping a thin sheet of autologous muscle around the end of a divided nerve. It takes approximately three months for an RPNI to mature. Neural signals can be recorded from the RPNI (100s to 1000s of μV) which are substantially greater than any motor signals recorded directly from peripheral nerves. The commercial system will consist of an implantable electromyography (EMG) recording device, wireless charger, prosthetic controller, and software application.
The commercial system will be functionally far more advanced than any device currently used in any clinic or research group. In terms of prostheses that directly use nerve signals, signals from this technique are much larger, much more stable over time, and much safer to obtain in terms of nerve health. In addition, a primary benefit of this approach with implantable EMG recorded from RPNIs is that it can decode a large number of independent movements with a system that rarely needs to be recalibrated.
- Intellectual Property: Patents for commercial system and a surgical tool; additional patents in progress
- Commercialization Strategy: Working with startup companies and major prosthetics companies
- Regulatory Pathway: Approved FDA Investigational Device Exemption; Pre-submission inquiry submitted
- Product Launch Strategy: Expand the experiments that can be included in the clinical trial, renewing the R01 grant
- Redesign circuitry for implantable transceiver, data logging
- End-to-end system test using SmartLink socket and implantable sensing unit (ISU)
- Activities of daily living demonstration
- Full software suite available for use by a prosthetist
- Complete miniature version of ISU
- Complete initial prototype of leads
- Submit IDE amendment to use ISU in human experiments
- Submit FDA pre-sub on full manufacturing and testing of leads
CLICK HERE to listen to Dr. Cederna’s interview on WJR radio.