special subjects
Prosthetic Components
Structural components of a limb prosthesis
A prosthesis is comprised of Socket(plastic receptacle in which the residual limb is contained), which is the most important component because it supports the body and transmits all associated pressure and forces developed during ambulation to the residual limb Appendages(eg, hand, foot) andjoints(eg, wrist, elbow, shoulder, ankle, knee, hip) Connecting modulesthat connect appendages and joints to the socket Advanced componentsare available. For lower limbs, microprocessor-controlled ankles and knees can provide greater safety, stability, reduced energy expenditure, and diminished stress to proximal joints and the spine. Myoelectric upper-limb prostheses use the natural, electrical signals of a person's muscles; sensing electrodes embedded in the socket of the prosthesis over active muscles detect muscular activity and transmit signals that operate the prosthetic hand, wrist, and/or elbow. No other body movement is required. In contrast, the body-powered upper-limb prosthesis requires a fully functioning shoulder and arm because there is a loop strap around and under the opposite axilla. The strap is connected to the prosthetic hand or hook via a wire cable. Movement of the opposing shoulder stretches the strap/cable system and thereby opens or closes the hand or hook. 