Hand prostheses that maintain a natural shape can either be mechanical or myoelectric. Myoelectric prostheses are driven by a motor and fed from accumulators placed inside the prosthesis. These prostheses enable a simple grip and/or rotation of wrist. Bionic prostheses are a step up from myoelectric prostheses: they enable control of each finger separately, and are more similar in terms of function to the healthy hand. The required movement of the prosthesis is generated by the contraction of muscles on the amputation stump and sensed through the skin using myoelectric signals.
The disadvantage of myoelectric prostheses is their high price. Therefore finger prostheses which can be controlled by cables attached to the body or by the other healthy hand are still widely used. Prostheses using cables can only use a maximum of one cable to grip an object. However, a smooth gripping movement cannot be achieved with cables. The fingers of cosmetic prosthesis are controlled by the healthy hand. However, these prostheses do not enable an object to be gripped or held, or allow it only to a limited extent.
The new, manually adjustable finger prosthesis enables a finger to be fixed in the required position using a cylinder slotting into which fits an arresting tooth. The screw of the arresting tooth is located on the outer side of the prosthesis. Thus the prosthesis user can adjust the degree of finger bend by pressing the screw. This presses the tooth and the user can set the finger in the required position. When the arresting tooth is released, the finger is secured in the required position.
This easy way to control prosthetic fingers and the possibility provided to lock each finger in a different position enables all kinds of objects to be gripped. Thus the life of people using this finger prosthesis approaches a little nearer to their life before amputation.
Source: (1) LUX, Martin. Experimental biomechanical hand prosthesis [online]. Brno, 2012 [cit. 2013-07-16]. Available in: http://dl.uk.fme.vutbr.cz/zobraz_soubor.php?id=1662. Diploma thesis. Brno University of Technology. Thesis supervisor Ing. David Paloušek, Ph.D.
Title picture legend:
Válec s drážkováním - Cylinder with slotting
Zub aretace - Arresting cog
