DARPA Prosthetics Programs Seek Natural Upper Limb

by David Pope, editorial director

A neurally-controlled arm and hand prosthesis that will perform, look, and feel like a natural limb is the goal of two Revolutionizing Prosthetics programs funded by the Defense Advanced Research Projects Agency (DARPA). According to Col. Geoff Ling, DARPA’s manager of the programs, the goal is not only to advance the state of the art in prosthetics, but also to have a prosthesis ready for clinical trials, including a completed submission of an investigational new device to the Food and Drug Administration within four years.
DARPA’s push to jump-start the production of an advanced, neurally controlled prosthesis consists of two inter-related programs: Revolutionizing Prosthetics 2007, which will deliver a working advanced prosthetic arm and hand with a neural interface by the end of 2007, and Revolutionizing Prosthetics 2009, which will have a neurally-controlled arm and hand prosthesis ready for FDA approval and clinical trials in four years.

The $18.1 million Revolutionizing Prosthetics 2007 program was awarded to DEKA Research and Development Corp. of Manchester, NH, which will design and fabricate an advanced prosthetic arm and hand within two years using the best technologies available. DEKA’s Integrated Solutions Division is working closely with medical researchers at the Rehabilitation Institute of Chicago who have successfully developed and surgically attached thought-controlled prosthetic arms and hands.

The $30.4 million Revolutionizing Prosthetics 2009 program was awarded to the Applied Physics Laboratory (APL) of Johns Hopkins University. APL is primary national security and government R&D contractor. Stuart D. Harshbarger is leading the APL effort.
DEKA, founded in 1982 by inventor Dean Kamen, focuses on the development of new technologies and innovative solutions. Its main success has been with medical products for companies such as Johnson & Johnson, which contracted with DEKA to develop the Independence IBOT mobility system for handicapped persons. IBOT uses some of the technology found in the Segway Human Transporter, another Kamen invention. In 2004 DEKA received a small DARPA award to develop a rapid mobility concept. The $18.1 award to develop a working prosthetic arm and hand requires DEKA to solve some of the more difficult mechanical aspects of providing near-human strength in a prosthetic arm and hand. DEKA also is to develop a customizable method of manufacturing a cosmetic covering for the arm and hand that is both functional and looks like normal skin. The DEKA neurally-interfaced prosthesis will begin clinical trials when it is completed in two years.

DEKA designers and engineers will start with the Neuro-controlled Bionic Arm pioneered at the Rehabilitation Institute of Chicago (RIC) by Todd Kuiken and a team of researchers. Kuiken, director of RIC’s neural engineering center for artificial limbs, came up with the idea of re-attaching existing nerves in the amputee’s upper limb to bands of muscles in the chest, which serve as surrogate controllers for moving the artificial limb. After the replanted nerves have innervated the chest muscles, thinking about arm and hand movements causes these muscles to contract. A myoelectric sensor detects the contractions and sends the signals to an amplifier and digital signal processor, which in turn sends command signals to the artificial arm and hand. A commercial version, called the Boston Digital Arm, is being marketed by Learning Technologies, Inc. of Holliston, MA, and the company is contributing to the DEKA prosthetic arm effort.

Also contributing to the DEKA effort are researchers at Northwestern University, which houses its prosthetics research in the RIC facilities. Also participating are Canadian researchers at the Institute of Biomedical Engineering at the University of New Brunswick who helped develop the EMG pattern recognition algorithms for Kuiken’s bionic arm and currently are developing sensors directly linked to neurons.

Another participant is Chicago PT, LLC, which develops robotic devices for physical therapy. Richard Wier, a research scientist at VA Chicago Health Care System and a biomedical engineer at Northwestern University’s Prosthetics Research Laboratory, is overseeing the design of the DEKA prosthetic arm. Wier has investigated implanted BION-like myoelectric sensors for multiple degrees-of-freedom prosthesis arm control and the use of fuzzy logic to interpret the EMG signals.
The Revolutionizing Prosthetics 2009 program that is being managed by APL of Johns Hopkins University is divided into two 24-month phases. Phase I addresses the extent to which efferent neural signals can be used to control a robotic arm and hand, and the extent to which sensory (afferent) feedback can be provided from the robotic device to the nervous system. The Kuiken bionic arm provides some touch feedback, and there are indications that the sense of touch can be greatly enhanced. At the end of Phase I, APL will have to demonstrate a strategy that will integrate efferent and afferent capabilities to the extent that the user of the prosthetic will be able to accomplish normal activities of daily living. In addition, the prosthetic must be wearable for 18 hours a day without discomfort or skin pathology.

DARPA is well-aware of the critical importance of neural control and feedback, and is encouraging a multi-team effort in this area. However, DARPA’s Revolutionizing Prosthetics program manager is confident that neural control can be achieved. “This program,” said Ling, “builds on the Human Assisted Neural Device program, which recently decoded the brain’s motor signals with such fidelity that motor movements of a robotic arm can be achieved entirely by direct brain control.” DARPA’s previous Brain Machine Interfaces program also focused on extraction of motor neural signals and sensory feedback for closed loop control of appendages or robotic devices.

The challenge of developing a neurally-controlled prosthesis that matches the strength and dexterity of a natural limb is not being underestimated by DARPA. “Clearly, this is a DARPA-hard challenge,” said Ling. “Breakthroughs in actuation, mechanical power distribution, energy storage, biotic/abiotic interfaces, sensors, and computation will be required. But the most important aspect is the ability to control the arm and hand by the intent of the user.” The technology developed for the arm prosthesis will be used to develop neurally-controlled lower limb prostheses.

At the end of Phase I, DARPA is prepared to replace some research teams if they have failed to make significant progress. Phase II will deliver an advanced neurally-controlled prosthesis ready for human clinical trials, including submission of a completed IDE application to the FDA. As the designated systems integrator, APL and project leader Harshbarger are responsible for ensuring that component technologies developed by the member teams are successfully integrated into a working prosthetic device.

“Our challenge is to advance the base of scientific understanding related to neural control mechanisms and physiological function of the human limb, while at the same time developing innovative engineering solutions that can be successfully implemented,” said Harshbarger. “DARPA wants this technology ready for clinical trials in only four years, so there is no time for us to re-create the wheel. We have handpicked a team that has decades of experience in prosthetics, but more importantly had made recent advances that are ready to be realized.”
APL will focus mainly on advanced neural control strategies that will allow the user to feel and manipulate objects in a natural manner. APL also aims to develop new power, actuation, and control technologies, and advanced sensors.

The teams assembled by APL include researchers from: Rehabilitation Institute of Chicago, Northwestern University and its Prosthetics Research Laboratory, Johns Hopkins University, California Institute of Technology, University of California at Irvine, University of Southern California, Arizona State University, University of Michigan, University of Rochester, University of Utah, Vanderbilt University, Oak Ridge National Laboratories, National Rehabilitation Hospital, Umea University (Sweden), Otto Bock Health Care (Austria), New World Associates, and the BioSTAR Group.

Second tier subcontractors and collaborators include: University of New Brunswick Institute of Biomedical Engineering, Chicago PT LLC, Fraunhofer Institute (Germany), Scuola Superiore Sant’Anna (Italy), Sigenics, Flexsys, Martin Bionics, Scott Sabolich Prosthetics and Research, Harvey Mudd College, Ripple, and Punch Communications.
Stimulus for DARPA’s Revolutionizing Prosthetics programs comes from the growing number of amputations resulting from injuries in the Iraq and Afghanistan war zones. More than 200 amputees from these war zones have been treated at Walter Reed Army Medical Center in Washington, DC, and at Brooke Army Medical Center in San Antonio.