Prosthetic Limbs That Can Feel

In the year 2000, scientists found a prosthetic toe buried with the mummified remains of a woman dating as far back as 1069, B.C. Today, the field of prosthetics continues to evolve, taking advantage of advancements in technology and surgery. Soon prosthetic limbs that have the ability to feel will be available to patients, providing the wearers with sensory information that was once the missing piece of the puzzle. Until recently, the wearer could only operate the prosthetic limb using visual senses.

Phantom Limb

• Amputee patients commonly report the feeling of phantom limbs. Even though he has lost a hand or an arm, the patient will continue to report sensation and even pain, as if the limb were still attached. The development of prosthetics with sensory information builds upon this notion. For example, if you press on an amputee's forearm, he will likely report that he feels as if you are pressing on his fingers. Signals are also sent from the brain to the nerve fibers in the severed area when the patient thinks about moving his phantom limb. Prosthetic limbs that can feel are hooked directly into nerves in order to provide sensory information.

Nerve Transplant

• Achieving a prosthetic limb that can feel begins with a nerve transplant. Nerves from the amputated limb are transplanted to the chest. Sensors in the prosthetic then send sensory information through electrodes in the amputated area to transplanted nerve endings in the chest. The nerve transplant provides the prosthetic with a better sense of self by allowing it to respond to sensations and neural signals. Transplanted nerves allow the patient to feel light touches as well as hot and cold.

Advancements

• Many companies are scrambling to offer the first marketable prosthetics that can feel. The European Union has funded the Smart Hand, which is a prosthetic hand that not only has sensory capabilities, but is also motorized. Sensors on the forearm not only allow the patient to move the hand intuitively, but also to sense objects that she is holding.

  In the United States, the Pentagon funds military research into prosthetics. The Deka Research and Development firm is working on a joystick-operated prosthetic arm that sends sensory information to bundles of nerves transplanted into the chest. This limb can also sense pressure, motion and temperature.

Problems and Setbacks

• Like all new technology, problems with prosthetics that can feel are imminent. While great advancements have been made for prosthetics below the elbow, more research and development is needed for upper arm amputees because they don't have the same muscle control. It is also difficult for the current technology to send sensory information to the proper part of the hand. This is due to the fact that it is difficult to place the electrodes accurately enough so that the patient can feel the difference between pressures on his index finger versus pressure on his middle finger. Creating a lasting, reliable prosthetic also poses a challenge because current prosthetics only last about two years before replacement is needed.