Electronic prosthetics eliminate the need for a body harness.
Prosthetics are artificial limbs designed to replace missing arms and legs that have been lost to injury or disease. Although body-powered prostheses are still used, electronic prosthetics are increasingly popular. Advances in technology have made these devices easier to operate and better able to mimic normal function.
Electronic Arm Prosthesis
Electronic arm prostheses are artificial limbs that are typically controlled by a battery. Myoelectric prostheses are the most commonly used type of electronic prosthesis. These devices are operated by electrical signals sent from the brain to muscles in the arm that tell the device how to move. Electrodes implanted in the prosthesis sit on the skin over specific muscles in the remaining part of the limb. Electrodes typically attach to the inside and outside of the elbow joint or the upper arm if the elbow joint is missing. As these muscles individually contract, the signal is recorded and made stronger in the prosthesis, activating the motor that controls the hand. Most electronic hands perform basic opening and closing movements, although hands that enable individual finger movements are in development.
Electronic Leg Prosthesis
Electronic leg prostheses typically use a single motor to control movement of the "knee" joint. Electrodes implanted in the prosthesis respond to muscles in the thigh. These muscles contract to tell the knee which way it should move. Electronic leg prostheses with a microprocessor in the knee joint are also available. Sensors in the knee, lower leg component and prosthetic foot collect information about the position of the leg as the person moves and adjust the function of the leg to match the person's current activity.
Electronic prostheses have several advantages over body-powered devices. Significantly less muscle strength is required to operate an electronic prosthesis. They are powered by a muscle twitch, requiring minimal strength to operate. These devices also tend to be more comfortable. Electronic arm prostheses do not require a harness to keep them in place like body-powered devices do. Unlike body-powered prostheses, electronic arm devices can also be operated with the shoulder in various positions, allowing the artificial hand to be used overhead or in other directions away from the body. These devices also look more realistic than body-powered devices, as they're often covered by silicon or latex "skin."
Some disadvantages are associated with an electronic prosthesis. These devices are significantly more expensive than body-powered limbs. The battery component of the device also requires maintenance, including charging on a daily basis. If the battery fails, the device cannot be used. Electronic prostheses are also often heavier than body-powered devices and cannot be used around water due to potential damage to the battery.