Loss of an arm or a hand is a severe injury that can affect a person's job prospects, personal relationships, and overall quality of life. Approximately 41,000 people in the United States have lost all or part of an arm, including many of the soldiers injured in the wars in Iraq and Afghanistan. Although most lower-limb amputations are caused by diseases such as diabetes and affect older people, most (90%) of upper-limb amputations are caused by trauma -- such as vehicle or machinery accidents or military conflict -- and affect young, active people. The most effective treatment is an artificial arm or prosthesis; however, the artificial arms that are currently available do not even come close to being able to replace a human hand or arm. They are heavy, clumsy, and uncomfortable to wear. They are difficult to control, and they cannot do many of the things people need them to do. Individuals with amputations need better devices and better ways to control them so that they can overcome their disability and get back to an active, productive lifestyle.

The Center for Bionic Medicine (CBM) is a research group at the Rehabilitation Institute of Chicago (RIC) that includes biomedical engineers, scientists, doctors, occupational therapists, and prosthetists and so can both understand the needs of people who have lost an arm and invent new ways to help them.

In 2002, CBM began a new surgical technique called Targeted Muscle Reinnervation (TMR). In TMR, the nerves that previously controlled the missing arm are sewn on to "target" muscles that no longer do anything because the arm is gone. Even though the arm is missing, the brain still sends messages down these nerves telling the arm how and when to move. The transferred arm nerves grow into (reinnervate) the target muscles so that when the person tries to move the missing arm, the target muscle contracts. When the target muscles contract, they make electrical signals (called EMG signals) that are detected by sensors (called electrodes) on the skin surface. These EMG signals are used to control a prosthesis -- so that when the person tries to move their missing arm, the prosthesis moves in a similar way to their arm. TMR has proved very successful, and more than 50 people around the world have now had the surgery.

The transferred nerves tell every part of the lost arm or hand how to move, including the fingers and thumb. After TMR, all that information is available and can be used for prosthesis control. However, current technology only allows a small amount of this arm-control information to be used.

CBM has developed new technologies -- including user-friendly electronics and new software -- that allow more control information from the target muscles to be used. The skin-surface electrodes and their wires are made of flexible fabric and they are embedded in a soft, flexible gel liner that fits comfortably over the remaining arm. The gel liner is easy to put on and take off, making it convenient to use. The fabric wires carry EMG signals to the new electronics, which use software to understand the signals and tell the prosthesis what to do. This system allows the prosthesis user to control their device without thinking about it and to make their prosthesis do more useful things.

CBM has also developed an artificial arm that is lightweight and small, and yet can perform more functions than arms that are currently available, including rotating and bending the wrist and making different hand grasps. The arm is small enough to be used by a small woman or adolescent, and it is quiet so that it is not noticeable in public.

We have tested these technologies in the laboratory and believe that they will work a lot better than the devices that people use now. These technologies pose no risk to users, but provide important benefits including easier, faster, and more natural prosthesis control and a much more user-friendly, useful prosthesis. We now need to test these technologies in clinical trials to see exactly how well they work in the real world, to measure what difference they make, and to find and fix any problems. We will focus on people with above-elbow amputations, but also do an initial test to see how these technologies might benefit people with shoulder-level amputations.

We expect that our new technologies will provide significant benefit to anyone who has lost an arm, especially military personnel. Loss of an arm is one of the most severe combat-related injuries, resulting in major disability in a young, fit group of people who may have additional battlefield injuries to deal with. To date, 14 service men and women have had TMR surgery, giving them better control of their prostheses. Our new technologies are another major step toward giving more ability back to these wounded warriors and may allow, for some, the chance to return to active duty. Our proposed clinical trials are an important step toward bringing better artificial arms to injured warfighters, war veterans, and civilians.