http://www.jhuapl.edu/prosthetics/scientists/mpl.asp

The human body is capable of doing extraordinary things. Our limbs can perform complex tasks such as drawing a picture or playing an instrument as well as endure the power of an impact or the exhaustion of a long run (1). However, there are people who are unfortunate and are missing limbs due to traumatic injuries, diseases, or birth defects (2). With the help of a prosthetic limb, some of the capabilities of a lost limb could be restored. Designs of prosthetics can vary in a multitude of ways including how they are attached to the body, the way they are controlled, as well as the purpose that they serve.

The process of attaching an artificial limb to the body usually begins with where the amputation has occurred. Different prosthetics are required depending on whether a major joint, such as an elbow or knee, needed to be removed (1,2). After it is determined whether or not the person needs a prosthetic with a joint or not, the artificial limb could be attached with a harness or strap system, an airtight suction seal, or shape changing structures (1,3). The type of attachment usually depends on the location and severity of an amputation.

http://www.oandpdesign.com/prosthetics.htm

Controlling an artificial limb is usually done in one of three ways. First, a prosthetic could be controlled by connecting it to somewhere else on the body using cables (1). Second, it could be powered by a motor that can be controlled by toggling a variety of switches or buttons (1). However, a more advanced and preferred way of control is known as myoelectric (1,2). Through this method, the prosthetic limb, in order to move,  listens to small electric signals that occur in the remaining muscle that a patient can still contract around an amputation.

Lastly, artificial limb designs can vary in the purpose that they serve. Some are obviously designed with physical function such as walking as the main goal (1). Others are designed with sensors to help measure and feel forces, vibrations, contact, and temperature (3). On the other hand, some designs are focused more on appearance. Known as cosmesis, this aspect of artificial limbs can be detailed to the extent of including freckles, hair, and fingerprints (1,2,3). The ultimate goal of cosmesis is a design that will fully resemble a natural limb (3).

Despite the fact that prosthetic limbs have improved the lives of thousands, they do still have their drawbacks and flaws. While they can restore some function, they can be difficult to learn how to use and are not advanced to the point where they can rival a biological limb (1). In addition, the cost of an artificial limb tends to be very high, ranging up to tens of thousands of dollars (1). However, with advancing technology, new materials, and more research, it is not out of the realm of possibility for prosthetics to become dramatically more similar to the real body.

Sources:

1. http://science.howstuffworks.com/prosthetic-limb.htm
2. http://www.oandpdesign.com/prosthetics.htm
3. http://www.jhuapl.edu/prosthetics/scientists/mpl.asp