Hand that thinks for itself

Press, 5 November 1977, Page 15

Hand that thinks for itself

An electronic hand for people with below-elbow amputations, controlled by the thought processes of the wearer, has been developed by a Swedish team of doctors and engineers, and is being tested on four men. The artificial extremity, covered with plastic so well moulded that it strongly resembles a normal hand, contains a sophisticated control unit that responds to electric signals from the arm muscles within the wearer’s forearm. It is capable of six movements. The electric impulses are filtered and amplified and they activate “tendons” inside the artificial hand. The wearer can rotate his wrist in either direction, flex the wrist upward or downward. and grip or release an object. The hand is still in the initial stage of clinical tests.

“It will be some time before we can make it available to large numbers of patients here in Sweden,

much less in other countries,” said Dr Peter Herberts, an orthopaedist at Sahlgren Hospital in the west coast city of Gothenburg.

Developed over a 12year period at a cost of about SIM in public grants, the device, known as the Sven-hand, has so far been fitted on four men in their thirties who live in Gothenburg. Athough the device is not yet commercially available, the price would have to be between $5OOO and $lO,OOO to cover the costs of small-scale production.

Before fitting the hand on each of the four patients, a group of doctors at Sahlgren Hospital, working with engineers from the city’s Chalmers University of Technology, first used an oscilloscope and other equipment to test the electric signals in the forearm stump.

These signals occur when the amputee, who has the “phantom limb”

sensation that his hand is still there, attempts to make it carry out specific movements. After a computer has analysed these command

patterns, which differ from person to person depending on the shape of the amputation stump, the patterns are programmed into a digital control unit which is placed inside the artificial hand.

To pick up the signals from the stump muscles, a sensitive electrode must be placed in exactly the right position on the skin. According to Dr Herberts, no commercially available electrode fitted the requirements of the signalling process ,and it proved necessary to design a special electrode. It is important for the socket of the device to fit perfectly against the

stump, so that all electrodes stay in contact with the skin regardless of arm movements. Dr Herberts says. This is done by mounting the electrodes on

Patients wear rechargeable batteries and other electronic gear needed to work the artificial hand on a special belt under their jackets.

Tests on one of the four patients, a 35-year-old man who had lost his left hand and forearm in an accident 25 years ago, showed that without any special training he was able to use his artificial hand to make all six movements within one second of making his mental command.

Development of the Sven-hand began in 1965 within the research institute of the Swedish armed

elastic springs, providing a resilient contact.

forces. The National Board for Technical Development took over the financing of, the project, and engineers from the Institute for the Handicapped in Stockholm and the nearby medical technology firm of Systemteknik have performed the actual construction work and made the first 10 prototypes.

Mr Torbjoem Holmqvist, an engineer at Systemteknik, said that to his knowledge the Sven-hand and related projects in Sweden were the most advanced in the world. “The Swedish authorities have been very generous in financing this type of technical research,” he said.

Mr Holmqvist said his firm had also designed a similarly controlled artificial hand for children aged from two to five. This had been tested during the last five years at the department of neurophysiology of the Regional Hospital at Oerebro, in central Sweden.

A study published this year by Dr R. Soerbye said children tested in Oerebro seemed to have a higher acceptance level of an artificial hand than adults. He said one patient wearing the electronic hand, an eight-year-old girl, “has become the club champion in running and in gymnasium she is doing exactly the same things as the others, without being less successful. She plays leapfrog, throws balls with both hands, skips rope, imitates Tarzan by swinging herself by rope. She has also taken lessons in trumpet-playing.”

Together with the Uppsala firm of Een-Holmgren, Systemteknik is developing a “second generation” artificial hand featuring an active thumb movement.

The electronic gear inside the new unit, called the Es-hand, is much more compact than in the Svenhand and it will be possibe to fit the device to a patient whose hand was amputated at the wrist.

From VICTOR KAYFETZ, of NZPA-Reuter, in Stockholm.