prosthesis
Meaning of prosthesis: Replacing a missing part is only half the task, since the fit against the remaining tissue decides whether a device is used or abandoned.
Definition of prosthesis
A prosthesis is an artificial device made to replace a body part that is missing, whether absent from birth, lost to injury, or removed by surgery. Artificial limbs, replacement hip and knee joints, artificial eyes, dentures and breast forms are all prostheses. The plural is prostheses, and the purpose may be function, appearance, or both together.
What kinds are there?
| Type | What it replaces | Mainly for |
|---|---|---|
| Limb prosthesis | Part of an arm or leg | Function, with appearance often close behind |
| Joint replacement | Worn or damaged joint surfaces, usually hip or knee | Function and relief of pain |
| Ocular prosthesis | An eye that has been removed | Appearance and support of the eyelids |
| Dental prosthesis | Missing teeth, as a denture, bridge or implant crown | Chewing, speech and appearance |
| Breast prosthesis | A breast removed for breast cancer | Appearance, balance and comfort of clothing |
Heart valves, testicular implants and parts of the skull replaced after injury belong on the same list. The word stretches from a silicone form worn inside a bra to a titanium component cemented into bone, which is why the setting usually matters more than the label.
How does a prosthesis differ from an orthosis or an implant?
A prosthesis replaces something that is gone. An orthosis, such as a brace, splint or shoe insert, supports, aligns or protects a part that is still there. The distinction decides which specialist is involved and how the device is funded, and it is one of the more commonly muddled pairs in the field. Implant is a looser word for anything placed inside the body, so a joint replacement is both an implant and an internal prosthesis, while a pacemaker is an implant that replaces no missing structure at all.
What decides whether it works?
Fit does most of the work. A limb prosthesis transmits body weight through a socket onto tissue never designed to carry it, so pressure, skin health and the changing shape of the residual limb govern comfort more than the sophistication of the mechanism further down. Devices are custom made and refitted repeatedly, especially in the months after surgery while swelling settles. Modern designs read electrical signals from remaining muscles to drive powered hands, and anchoring the socket directly to bone is used in selected cases, but a device that hurts is a device that stays in a cupboard.
Used in a sentence
The patient was fitted for a prosthesis following the below-knee amputation.
Good to know
A prosthesis replaces a missing body part, while an orthosis supports or corrects one that is still present, a distinction that determines which device suits a given situation.
Word origin
Where “prosthesis” comes from
Formed from Greek prosthesis, meaning an addition, from prostithenai, meaning to place in addition.