artificial limb

(redirected from Prosthetic hand)
Also found in: Medical.

artificial limb,

mechanical replacement for a missing limb. An artificial limb, called a prosthesis, must be light and flexible to permit easy movement, but must also be sufficiently sturdy to support the weight of the body or to manipulate objects. The materials used in artificial limbs include willow wood, laminated fibers and plastics, various metallic alloys, and carbon-fiber composites. One model of artificial leg is made of layers of stockinette cloth coated with plastic; it has duraluminum joints at the knee and ankle, rubber soles on the feet, and a leather cuff cushioning the stump. The cuff fits around the thigh like a corset, holding the artificial leg firmly in place, and connects to a leather belt around the waist. Often, spring joints are employed on foot pieces to give natural-looking movements. Microprocessors and an array of sensors are used to operate the mechanical and hydraulic system of some artifical legs, providing more natural locomotion. Sensors, microprocessors, and nerve stimulators can also be used to transmit stimulatory signals to nerve endings in the stump, allowing the amputee to feel more lifelike sensations from the artificial foot. Other artificial legs sacrifice a natural appearance to achieve greater mobility, such as the C-shaped carbon-fiber Flex-Foot used by amputees to participate in track-and-field sports. Artificial legs may also be secured by suction between socket and stump.

Artificial arms, not having to support the weight of the body, may be made of lighter metals and plastics. They are usually strapped to the trunk and controlled by a shoulder harness. Bionic arms have been developed that permit a person to use thought to control the limited movements of the motorized prosthesis. The commands are transmitted through chest muscle that has been surgically connected to the remaining nerves associated with the lost limb; electrodes linked to the artificial arm convert the sensed electrical signals of the muscle into arm movement. Tests with monkeys have shown that robotic arms can be controlled by the brain's electrical signals directly, using probes implanted in the brain and computer software to interpret the signals, and in laboratory experiments a person has similarly controlled a robotic arm.

Artificial hands vary in structure and utility; research and development has resulted in devices that are both cosmetic and functional. For example, an artificial hand has been devised that utilizes a split hook resembling a lobster claw; this is enclosed within a flexible plastic glove that can be made remarkably lifelike, even having fingerprints. The biceps muscle can be attached to the prosthesis by a surgical procedure called cineplasty, which permits grasping in the terminal device while dispensing with shoulder harnesses. A more recent artificial hand has separate motors for each finger, allowing for a more natural and useful grip and movement; the prosthesis is controlled by electrical signals generated by the arm muscles that normally control the hand. Software and electronics have improved sufficiently that some artificial hands can supply feedback to sensory nerves, enabling the user to feel the size, shape, and rigidity or flexibility of the object being handled.

References in periodicals archive ?
Among people with only one hand, the brain area that enables us to recognise hands can also recognise a prosthetic hand, particularly among those who use a prosthesis regularly.
Griffin clipped his prosthetic hand onto the bar, then leaned back.
The prosthetic hand detects information from an object and then relays it through electrodes that are implanted in nerves.
Lambru refused to give in and left his dream of becoming a footballer, so he bought a costly prosthetic hand from Italy .
Born without a right hand below the wrist, the girl is now able to pick up objects, all thanks to two students and a teacher who designed a custom prosthetic hand using the 3-D printer.
Tenders are invited for : Recruitment of the supply of a multi-articulated prosthetic hand for adaptation to passive twist wrap with coaxial connector, addressed to an amputated patient attended by FREMAP, Mutua Collaborator with Social Security n 61
The prosthetic hand enabled Kelsie Williams, of North Wales, to skip and to ride her bike.
Benitez was offered a prosthetic hand by Po Paraguay, a non-profit organisation that makes 3D-printed prostheses.
Engineers working to add "muscle sense" to prosthetic limbs found that tactile feedback on the skin allowed blindfolded test subjects to more than double their ability to discern the size of objects grasped with a prosthetic hand.
It does not stretch when the prosthetic hand is open.
In the study, neuroscientists from the University of Chicago used neuroprosthetic devices to turn the pressure 'felt' by a prosthetic hand into a signal that feeds directly into the parts of the brain that deal with hand movement and touch.
Her group also prints transistors, electrical leads, and other components on the rubbery skins to make stretchy circuits that could process data from touch sensors on a prosthetic hand.