special subjects
Options for Limb Prostheses
Upper Extremity Prostheses
The hand has significant psychosocial meaning. Amputation can affect a person's self-perception and/or identity and have a significant impact on relationships and career. Psychologic counseling should be routinely offered. The human hand is complex, and often two different prostheses are necessary to provide optimal function for general daily activities and for specific activities. There are 5 general types of upper extremity prosthesis: Passive prostheses Body-powered prostheses Externally powered myoelectric prostheses Hybrid prostheses Activity-specific prostheses Passive prosthesesassist in balance, stabilization of objects (such as paper when writing), or recreational/vocational activities. They look like a natural limb, are the lightest and cheapest, but they provide no active hand prehension. Body-powered prosthesesare the most often prescribed because they tend to be less expensive, more durable, and require less maintenance. A harness-cable system suspends the prosthesis and captures scapular and humeral motion to operate the hook, hand, or elbow joint. Some systems use the opposing arm to trigger one particular function; one end of a strap encircles the opposite arm at the axilla, and the other end connects to a cable that controls the terminal device (hook, hand, or specialty device for particular function). People involved in physical labor typically favor this type. Externally powered myoelectric prosthesesprovide active hand and joint movement without the need of scapular, humeral, or trunk motion. Sensors and other inputs detect muscle movement of the residual limb or upper body and control powered actuators that provide greater grasp force than body-powered prostheses. Hybrid prosthesesare typically prescribed for higher level upper-limb amputations. They combine specific features of body power and myoelectric power, for example a body-powered elbow might be combined with an externally powered hand or terminal device. Activity-specific prosthesesare designed to allow participation in activities that would otherwise damage the patient's residual limb or everyday prosthesis, or when the everyday prosthesis would not function effectively. These prostheses often include a specialty design interface, socket, suspension system, and terminal device. Activity-specific terminal devices can allow the patient to grasp a hammer and other tools, a golf club, or baseball bat, or hold a baseball glove. Others aid in various specific activities (eg, swimming, fishing). These devices can be passive or controlled by the amputee. Partial-hand amputations range from single or multiple digits to carpal-metacarpal; wrist flexion and extension is usually preserved. Functional prosthetic restoration is possible for complete hand or one or more missing fingers using mechanical or external power. Grasp and pinch can often be achieved by the opposition of some combination of natural and prosthetic digits. Wrist disarticulation amputation removes all carpal bones, leaving no ability to flex or extend the wrist. Pronation and supination are mostly retained. A prosthetic hand, hook, or special activity terminal device can be used. Passive, body-powered, or externally powered (myoelectric) devices can be used. Transradial/ulnar amputations can be long (2/3 or more of original radius bone length), medium (1/3 to 2/3 of original length), or short (≤ 1/3 of original length). Long and medium level amputations can retain some pronation and supination. Passive, body-powered, or externally powered devices can be used. Elbow disarticulation and above-elbow prostheses both require a mechanical elbow. Elbow disarticulation prostheses typically employ body power to flex the elbow (gravity extends the elbow) and myoelectric control of the terminal device. Two external elbow hinges are attached to the outside of the plastic socket. There are many combinations of elbow and control systems. In shoulder disarticulation and interscapular prostheses, heat dissipation, weight distribution, and comfort are of paramount concern. The contact surface can be rigid or flexible plastic, or a gel cushion material such as silicone. The most functional prostheses for these levels of amputation typically include myoelectric control for one or more joints and hand functioning. 