Prosthetic Limb Types
A prosthesis is an artificial external device, designed to replace a missing part of the body – be it missing from birth or lost due to an injury – or to make the body part in question function more effectively. The best example of prosthesis, and one which most people are aware of, is that of prosthetic limbs, more commonly known as artificial limbs.
Transtibial Prostheses
A transtibial prosthesis is one designed to replace a missing leg below the knee. With this artificial limb, the amputee is able to keep control of his/her own knee. Due to this, patients with transtibial prosthesis have the best chance of regaining control of their movements, because the knee is the most complex part of the leg when it comes to biomechanics.
Transfemoral Prostheses
A transfemoral prosthesis is a prosthetic limb that replaces a missing leg from above the knee. As explained above, the knee is a most complex part of the leg, thus transfemoral amputees require a lot more energy and work in order to regain normal movement. Transfemoral prostheses consist of four main parts: the socket, the knee system, the shin and the foot-ankle system. To retain the leg in place, either suction or a suspension system can be used. Two types of upper leg prosthesis are the exoskeletal and the endoskeletal designs. The former is made up of wood and polyurethane foam covered with laminated or preformed plastic which provides the strength and through which the weight load is transmitted. This is a hollow design in the form of a normal leg. The endoskeletal design, considered superior to the exoskeletal, consists of a tube of aluminium, titanium or carbon-fibre epoxy through which the weight load is transmitted. The leg form is provided by an external foam cover shaped according to the measurements of the amputee.
Transradial Prostheses
A transradial prosthesis replaces a missing arm below the elbow. There are two types of this prosthesis, a cable type were the prosthesis is moved with the help of a cable held around the opposite shoulder, and a myoelectrical type, in which the prosthesis senses electrical signals sent by flexing the muscles.
Transhumeral Prostheses
A transhumeral prosthesis is designed as a replacement for a missing arm above the elbow. In this prosthesis, the functionality of the elbow has to be taken into account. When designing a transhumeral and elbow disarticulation prosthesis, a number of factors have to be taken into consideration, including the length of the bony arm, the quality and nature of soft-tissue coverage, the shape and muscle tone of the residual link and the flexibility and range of motion of the proximal joints.