Advice from a Certified Hand Therapist: Upper Extremity Prosthetics
I have seen news stories about robotic arms. What is really out there for people to use?
Advances in upper extremity prosthetics have come slowly over the last 100 years. The first prosthetics were cable-driven devices or body-powered prostheses. These required the user to be able to move his/her body (usually the shoulder) to pull on a cable to bend and straighten the arm or open and close a hook. Most big leaps forward have, unfortunately, come from wartime injuries. Cable-driven prosthetics became the norm around the time of WWI, WWII and the Korean War. During Vietnam, myoelectric prostheses emerged. Myoelectric prostheses are controlled with the electric signals produced by muscles in the person’s remaining arm. Now, after 15 years of conflict in Afghanistan and Iraq, the area of upper extremity prosthetics is ready to make another big jump.
Upper extremity prosthetics have made a splash in the news during the past 10 years as a result of the 2006 DARPA (Defense Advanced Research Projects Agency) Revolutionizing Prosthetics project. The program grew from a desire to make an arm that moves exactly like a human arm. Dean Kamen (creator of the Segway) helped develop the DEKA Arm, sometimes called the “Luke arm” after Luke Skywalker. Johns Hopkins Applied Physics Lab created the APL limb. While the APL limb is still in the research stage, the DEKA Arm was approved for the market by the FDA in 2014. Other prostheses on the market include the Michaelangelo hand from Ottobock, and the iLimb hand from TouchBionics.
How do these new prostheses work?
A big advancement in the past five years has been the use of microprocessors and pattern recognition software that allows for more accurate control. For example, the DEKA Arm sends electrical signals from the muscles to a computer processor in the prosthetic arm, which then produces movements in the prosthetic hand. These movements are more refined than traditional cable-driven prostheses, allowing the person to perform tasks such as preparing food, turning keys and holding a toothbrush. Watch this great video from Johns Hopkins University Applied Physics Laboratory https://youtu.be/9NOncx2jU0Ql.
That is amazing! Are they able to feel things with this arm? It doesn’t look like they would be able to with all that metal and plastic.
New research has shown promise in adding sensation to upper extremity prostheses. The Hand Proprioception and Touch Interface (HAPTIX) program is creating technology that will enable users to gauge grip force and sense hand position. The HAPTIX system involves implanting electrodes in the body that sense movement and relay this to the sensory nerves. Adding this type of sensory feedback may ultimately reduce phantom limb pain.
What will they think of next for prosthetics?
On the horizon are prostheses that can be controlled by electrodes implanted in the brain. This would not only allow more seamless integration of prostheses for amputees but also give exciting opportunities for patients with spinal cord injuries through robotics, exoskeletons and other technology.
Jeff Smith, OTR/L, CHT is a Certified Hand Therapist and a member of the American Society of Hand Therapists. Special thanks to Rahsaan Holley, MS, OTR/L, Director of Research at National Rehabilitation Hospital and to Brian Monroe, CPO, National Upper Limb Specialist with Hanger Prosthetics.