Ripple, a medical device company in Salt Lake City, is developing implantable electronic devices to provide advanced control of prosthetic hands and to restore sensations such as touch and finger position. As part of the Defense Advanced Research Projects Agency (DARPA)’s Hand Proprioception and Touch Interfaces (HAPTIX) program, Ripple is building a myoelectric implant to detect muscle signals for control of the prosthesis and an implantable neural stimulator to activate peripheral nerves to restore sensation. These devices are planned for use in clinical tests in collaboration with academic research universities.Every day we use our hands as tools to complete the tasks of daily living, and we also use our hands as sensors to learn about the world around us. Sensory nerves in our fingers tell us about the texture and temperature of objects as well as allow reflexes to prevent items from slipping from our grasp. People who have lost a hand not only suffer from the increased difficulty of performing routine tasks, they also lose the sensation required to manipulate objects gracefully.
New prosthetic hands increasingly look more like sophisticated marvels from sci-fi movies, but people have difficulty using these artificial hands because the devices do not have access to the subtle signals the body sends to produce coordinated motions. Also, the absence of sensory information from the robotic hand makes the prosthesis seem more like a foreign object than an extension of the body. “A hand that cannot feel does not feel like a hand,” explains Dr. Daniel McDonnall, Director of Research at Ripple.
Ripple’s myoelectric implant includes multiple electrodes to be implanted in the forearm to detect signals from the remaining muscles that formerly were used to move the hand and wrist. These electrodes connect to an electronics package implanted under the skin that wirelessly sends signals from the forearm muscles to a receiver built into the prosthetic arm. By recording from several of these muscles, people can use the myoelectric implant to more naturally control simultaneous motion of multiple joints in the prosthesis. Implanted sensors provide more reliable signals than conventional sensors placed on the surface of the skin. Ripple’s device has been under development for five years with ongoing support from the National Institutes of Health.
The implantable neural stimulator selectively activates nerve fibers that carry sensory information from the limb to the brain. HAPTIX seeks to tap into these biological communication pathways so that users can control and sense the prosthesis via the same neural signaling pathways used for intact hands and arms. Mechanical sensors built into the prosthetic hand can detect when the hand touches an object as well as proprioceptive information, such as whether the prosthetic hand is open or closed. Ripple’s neural stimulator will use information from these mechanical sensors to activate specific nerves to restore natural sensation from the missing hand.
Ripple will coordinate with researchers at the University of Pittsburgh and the University of Utah to conduct clinical trials evaluating performance of these systems in human subjects. Information gathered from these studies will provide support for Ripple’s submission to the Food and Drug Administration for clearance to provide this technology to patients across the nation. “Our goal is to help people embody their prostheses as an extension of themselves, not only to reduce the challenge of the activities of daily living, but to restore a sense of self to these deserving patients,” says Dr. Daniel Merrill, Chief Clinical Scientist at Ripple.
Located in Salt Lake City, Ripple was founded in 2004 to commercially develop medical instrumentation and implantable products for underserved, high-need patient markets that have traditionally been too small to be addressed by larger companies. In contrast with many electronic-only design firms, Ripple has the knowledge and experience to take basic instrumentation technology through to standards- compliant, FDA-approved medical products.
Ripple has close ties with the academic research community and maintains a presence at scientific and neuroprosthetic conferences. The company also offers contract design and consulting services for clients who need to convert prototype technology into medical products that meet safety standards and regulatory requirements for clinical use.
For more information about Ripple, visit www.rppl.com.
Contact: Daniel McDonnall, PhD Daniel Merrill, PhD
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