“Previously, components in a prosthetic hand limited the number of functions the hand could perform,” says Icexpress operations manager Johan Snyders.
“One can perform almost any function with the bionic hand that can be performed by a normal hand. “The fingers are signal dependent, meaning that, when a firm hard signal is given, the hand will close almost immediately, and when a soft signal is given, it will close slowly,” he says.
The bionic hand was developed using leading-edge mechanical engineering techniques, and is manufactured from high-strength plastics. It is controlled through a highly intuitive control system that uses a traditional two- input myoelectric signal to open and close the hand’s fingers.
Myoelectric controls use the electrical signal generated by the muscles in the remaining portion of the patient’s limb. Electrodes on the surface of the skin pick up this signal. Existing users of basic myoelectric prosthetic hands are able to adapt to the new system quickly and can master the device’s new functionality within minutes.
The bionic hand’s thumb can, like a human thumb, be rotated into different positions to enable important grip configurations, many of which have not been available to amputees before. The grasp of the hand is akin to a human hand’s, with the articulating fingers able to close tightly around objects. Built-in detection tells each individual finger when it has sufficient grip on an object and, therefore, when to stop powering. Individual fingers lock into position until the patient triggers an open signal through a simple muscle flex.
While previous myoelectric hands could only be opened and closed, the bionic hand offers numerous grip patterns that enhance dexterity and support almost all daily living activities. For example, patients are now able to point the index finger to operate a keyboard, or to rotate the thumb in order to meet the side of the index finger to hold a plate or turn a key in a lock. None of these functions were possible before.
Snyders says that the muscles that control movement, called flexors and extensors, are still in place after an amputation takes place. He notes that this allows an electrode to be placed on the skin at the position where the maximum impulse originates in the muscle. When an amputee tries to contract that muscle group, an impulse from the electrode will be sent to a power source where it will be enhanced, allowing the user to open and close the hand as well as rotate the wrist, he says.
The bionic hand has an internal micropro-cessor and, with four fully powered fingers and an articulating thumb, users are given the ability to bend, touch and pick up and point, mimicking the movement of a natural hand. Each finger has an individually powered motor located within each digit. Each finger is built to include a gearbox that allows the user to close the hand and as soon as the fingers experience resistance, the gearbox will disengage, allowing the finger to stall in the appropriate position.
Normally, says Snyders, this sort of technology would bypass Africa.
However, he notes, Icexpress got involved in the i-limb technology following its exist- ing expertise in lower limb bionic technology.
“Icexpress is currently one of a few specialised prosthetic providers in Africa focusing on socket design and amputee rehabilitation. “Our vision is to allow users in Africa to have similar benefits as the rest of the world,” he says.
Snyders admits that the bionic hand is expensive, but adds that as technology becomes more advanced, it will gradually become cheaper. He believes that the breakthrough in the development of the hand could lead to other technological breakthroughs, such as arti- ficial muscles and nerve transplants that will enhance quality of life for amputees in Africa.
The bionic arm had a limited launch in July last year in Vancouver, Canada, and there are now 300 units across the globe.