Picture: An iron hand 
The Iron Hand of Götz von
Berlichingen was a real
sensation in his time

However, the attempt to displace lost body parts with prosthesis has a long tradition.

Historians believe that humans started ousting amputated extremities through self-made body parts as early as 2000 before Christ. The Egyptians made legs out of hollowed tree trunks and ancient Roman images show soldiers with artificial hands made of metal. These prostheses were purely cosmetically, they could not move actively.

The most popular prosthesis of the Middle Ages is the so called Iron Hand of knight Götz von Berlichingen. It was constructed in 1504 by an armourer and a real sensation at that time. It looked like an iron glove and was tightened to the stump of the forearm with leather straps. With the help of gearwheels the fingers could be revolved and fixed at a certain position, so that the knight could hold his sword and continue to carry out his profession.

Until the 19th century nothing happened in the development of prosthetic arms. In 1812 the Berlin dentist and surgical technician Peter Baliff had a new idea: he wanted to use the remaining power of the amputated arm to move the prosthesis. Therefore, he tightened tackles round elbow and shoulder, which carried out the movement. By stretching of the elbow the thumb could also be stretched and with a certain movement of the shoulder the other fingers were stretched. For the user of the prosthesis this meant that he had to crick himself to move his artificial hand.

The First World War and the many soldiers who had lost arms or legs gave new impetus to the development of prosthetic arms. In 1916 surgeon Dr. Ferdinand Sauerbruch revolutionised arm prosthetics with the construction of the Sauerbruch-Hand. This hand could be moved by stretching the upper arm. Unfortunately the grip of the hand was rather weak.

After the Second World War electric motors were used to move the fingers. Since the late 1960s myoelectric systems have prevailed. Electrodes on the skin measure electric impulses produced by the stretched arm muscle. These impulses are transferred to the motor which moves the fingers. Compared to a natural hand the functions of such prosthetic arms are limited. A lot of exercise is necessary to handle them and even then they allow only a few simple movements. Moreover their heave weight often leads to strong pain in the upper arm. For many people their prosthetic arm is more a burden than a help and about one third is not using it at all.

A possible alternative could be the newly developed Fluidhand, created by scientists at Karlsruhe research centre. This artificial hand has cushions on its wrists. When air is pumped into the cushions the fingers move. The special advantage of the Fluidhand is its light weight and its flexibility.

However the basic problem is still the same as it used to be 500 years ago: artificial hands are numb and insensitive to pressure. Researchers from Switzerland and the USA want to change that. They are working on a sensitive prosthetic arm controlled by the brain. It will probably take some more years until such a feeling artificial hand is available to patients.

MEDICA.de