Any device used to replace a body part, organ, or limb, usually taking over all or part of its function. The most common prosthetic device (and the only one that the vast majority of the population are likely to need) is the artificial denture ("false teeth" or a "false tooth"). More than 50 percent of the American population over the age of 50 have dentures of some sort, either complete or partial, or have has teeth crowned.

The design of artificial limbs has been much improved in recent years. At one time an artificial leg was little better than the old-fashioned wooden leg; but the use of lightweight materials and improvements in joint movement have now made it possible for amputees to pass undetected in company. The most recent advance is the development of artificial limbs that are controlled by nerve impulses fed from the stump of the natural arm. These prostheses look like normal limbs, and their internal power systems enable the user to pick up and manipulate objects.

A third common use of prostheses is in the treatment of arthritis. Replacement of the hip joint in cases of both rheumatoid arthritis and osteoarthritis is now commonplace, using stainless steel and plastic materials. As a result of the success of this type of operation, surgeons have gone on to design elbow, knee, shoulder, and finger joints that can be implanted to replace joints in persons with severe arthritis.

A prosthesis that has gained much attention in recent years is the artificial heart. It has been used as a total heart replacement in a small number of persons with severe, life-threatening, end-stage heart disease who, because of their age and other factors, are not good candidate for heart transplants, and for those in need of a heart transplant but for whom a donor heart is not yet available. So far the results have been so poor that many experts have condemned the procedure. It is still considered experimental.

One of the most common reasons for open-heart surgery is the implantation of artificial heart valves in those whose valves are distorted or damaged from conditions such as rheumatic heart disease.

Other prostheses in current use include acrylic lenses (to replace those affected by cataract) and artificial eyes (whose purpose is entirely cosmetic). An artificial larynx ("voice box") is still under trial, and attempts are being made to miniaturize an artificial pancreas for use by diabetics. In the case of many complex internal organs, however, transplantation has so far proved more practicable than the development of mechanical prostheses.

Pros"the*sis (?), n. [L., fr. Gr. an addition, fr. to put to, to add; to + to put, place.]

1. Surg.

The addition to the human body of some artificial part, to replace one that is wanting, as a log or an eye; -- called also prothesis.

2. Gram.

The prefixing of one or more letters to the beginning of a word, as in beloved.


© Webster 1913.

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