Each finger can be moved separately

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Each finger can be moved separately

A new prosthetic hand is being tested at the Orthopedic University

Hospital in Heidelberg, grip function almost like a natural hand

http://www.eurekalert.org/pub_releases/2008-04/uhh-efc042208.php

It can hold a credit card, use a keyboard with the index finger, and

lift a bag weighing up to 20 kg – the world's first commercially

available pros-thetic hand that can move each finger separately and

has an astounding range of grip configurations. For the first time

worldwide a patient at the Orthopedic University Hospital in

Heidelberg has tested both the " i-LIMB " hand in comparison with

another innovative prosthesis, the so called " Fluidhand " . Eighteen-

year-old Sören Wolf, who was born with only one hand, is enthusiastic

about its capabilities.

The new prosthetic hand developed and distributed by the ish com-

pany " Touch Bionics " certainly has advantages over previous models.

For example, a comparable standard product from another manufacturer

al-lows only a pinch grip using thumb, index, and middle finger, and

not a grip using all five fingers. This does not allow a full-wrap

grip of an object.

Myoelectric signals from the stump of the arm control the prosthesis

Complex electronics and five motors contained in the fingers enable

every digit of the i-LIMB to be powered individually. A passive

positioning of the thumb enables various grip configurations to be

activated. The myoelectric signals from the stump control the

prosthetic hand; muscle signals are picked up by electrodes on the

skin and transferred to the control electronics in the prosthetic

hand. Batteries provide the necessary power.

The " Fluidhand " from Karlsruhe, thus far developed only as a

prototype that is also being tested in the Orthopedic University

Hospital in Heidelberg, is based on a somewhat different principle.

Unlike its predecessors, the new hand can close around objects, even

those with irregular surfaces. A large contact surface and soft,

passive form elements greatly reduce the gripping power required to

hold onto such an object. The hand also feels softer, more elastic,

and more natural than conventional hard prosthetic devices.

" Fluidhand " prosthetic device offers better finishing and better grip

function

The flexible drives are located directly in the movable finger joints

and operate on the biological principle of the spider leg – to flex

the joints, elastic chambers are pumped up by miniature hydraulics.

In this way, index finger, middle finger and thumb can be moved

independently. The prosthetic hand gives the stump feedback, enabling

the amputee to sense the strength of the grip.

Thus far, Sören has been the only patient in Heidelberg who has

tested both models. " This experience is very important for us, " says

Simon Steffen, Director of the Department of Upper Extremities at the

Orthopedic University Hospital in Heidelberg. The two new models were

the best of those tested, with a slight advantage for Fluidhand

because of its better finishing, the programmed grip configurations,

power feedback, and the more easily adjustable controls. However,

this prosthetic device is not in serial production. " First the

developers have to find a company to produce it, " says Alfons Fuchs,

Director of Orthopedics Engineering at the Orthopedic University

Hospital in Heidelberg, as the costs of manufacturing it are

comparatively high. However it is possible to produce an individual

model. Thus far, only one patient in the world has received a

Fluidhand for everyday use. A second patient will soon be fitted with

this innovative prosthesis in Heidelberg.

Heidelberg Orthopedic Workshop provide a unique service in Germany

The workshop at the Orthopedic University Hospital in Heidelberg has

been in existence since 1919 and is unique in Germany. Since the Tha-

lidomide tragedy in the 1960s it has had its own research department.

Today there are some 60 specialized professionals employed in the

orthopedic workshop who have learned their trade in many years of

training. Every year, around 5,000 patients are fitted with

orthopedic aids.