The hand can hold a bank card, the forefinger can operate a keyboard and lift a bag weighing up to 20 kg: the world’s first fully articulating and commercially available bionic hand that can move each digit individually and can bend the fingers almost like a human hand. A patient at the Orthopaedic Hospital at Heidelberg University has now tested the “i-Limb-Hand”. Eighteen-year-old Sören Wolf, who was born with only one hand, is enthusiastic about the hand’s capabilities.

The new prosthetic hand is developed and marketed by the Scottish company “Touch Bionics”; it has considerable advantages over traditional models. A similar product by another manufacturer only enables the users to grasp things with thumb, index and middle finger, but not with all five fingers. This means that users cannot grasp an object with the whole hand.

Complex electronics and five engines in the fingers enable the patients to activate each digit of the bionic hand. The thumb can be rotated into different positions and thus enables important grip configurations. The hand is controlled by electrical signals generated by the muscles in the remaining portion of the patient’s limb. These signals are picked up by the electrodes that sit on the surface of the skin and are transmitted to the prosthetic hand. Accumulators supply the energy required to operate the hand.

"Fluidhand" with improved finishing and better grip function

The “Fluidhand” developed by the Karlsruhe Research Centre, which is so far only available in prototype form, is based on a slightly different principle. This prosthesis is also being tested at the Orthopaedic Hospital at the Heidelberg University Hospital. Unlike its precursors, the Fluidhand can close around objects with irregular surfaces. A large contact area and soft, passive elements considerably reduce the grasping force that is required to securely hold an object, thereby increasing the range of movements of the hand. The hand is softer, more elastic and more natural than traditional, rigid prostheses.

The flexible actuators are situated directly in the finger joints and work according to the biological model of a spider leg. Flexing of the joints is accomplished by inflating the elastic chambers. Thus, index finger, middle finger and thumb can be operated independently from each other. The integration of a force feedback between prosthesis and remaining limb gives the patient a sense of feeling.

Sören has so far been the only one to test both models. “His experience is very important for us,” explains Simon Steffen, head of the Department Upper Limbs at the Orthopaedic Hospital at Heidelberg University. The two models achieved the best results, with a slight advantage for Fluidhand due to better processing and programmed grip patterns, the integration of force feedback and better adjustable control of the hand. However, the Fluidhand prosthesis is so far only available as prototype. “The developers will have to find a company to serially produce the prosthesis,” said Alfons Fuchs, head of Orthopaedic Technology at the Hospital referring to the high production costs. However, individual hands can be manufactured if required. So far, only one patient is using the hand for his daily activities; a second patient from Heidelberg will shortly be provided with the Fluidhand.

The workshop of the Orthopaedic University Hospital in Heidelberg was established in 1919 and is the only one of its kind in Germany. Since the Distaval® crisis in the 1960s the workshop has an own research division and almost 60 highly specialised experts who have learned their craft during a year-long training course. Every year, approximately 5000 patients are given advice on and supplied with orthopaedic aids.

Source: University Hospital Heidelberg / Orthopaedic University Hospital Heidelberg Foundation - 9th April 2008

Further information:
Alfons Fuchs
Head of Technical Orthopaedics
Orthopaedic University Hospital Foundation
Schlierbacher Landstraße 200
69118 Heidelberg
Tel.: +49 (0)6221/966406
E-mail: alfons.fuchs@ok.uni-heidelberg.de