What are body-powered and myoelectric prosthetics and how do they work?i

There are many types of prosthetics available in the market today for all kinds of disabilities. The type of device that a patient may choose is going to depend on his/her needs and desires. Today I am going to talk about the two main types of mechanical prosthetics that are currently available and how the contrast. These devices are the body-powered, and the myoelectric prosthetics!

Body-powered Prosthetics

As its name indicates, this prosthetic is powered by the patients body. It usually uses the remaining extensions of the patients limb to function the device. They are fairly simple and most of the time make use of wires and bolts. As you can see n the middle picture below, the device sits on the forearm and the remaining part of the patients limb. When the patient bends their hand, the wires you see in the picture work as tendons and make the hand close. This is a very specific application for a body-powered prosthetic, but since each case is different it’s very complicated to mass produce prosthetics. This is one of the reasons why they can be so expensive.

Curtesy of E-nable (Click for website)

Myoelectric Prosthetics:

On the other end of the spectrum from the body-powered devices are the myoelectric prosthetics. They are the current state of the art prosthetic devices and are also known as bionic limbs. The main characteristics of these devices are that they are electronically equipped. They are composed of a motor, a control unit, a battery, and electrodes. The way it works is that the electrodes capture the muscle movement in the patient’s arm, send that information to the control unit, and from there it moves the motor accordingly to the patient’s desire. Some of the problems with these devices are that they are usually heavier than what the patient’s limb would weigh, and they are slow to process commands due to the method utilized to pick up the signals.

Recently, a group of researchers with the hope of improving bionic arms, have experimented with what is called a TMR (Targeted Muscle Reinnervation) surgery. The leader of the research was Todd Kuiken, the director of the Center for Bionics Medicine. This surgery is very promising for the improvement of the the signal amplification through biological means. In a brief summary, this surgery moves the nerve endings that would control the patient’s arm muscles and root these nerves into the patient’s chest muscles. The surgery performed by the researchers was successful and a few very exciting and unexpected discoveries came out of this experiment.

In the next post I’m going to talk a little bit more about the outcome of the surgery, and its discoveries. I’m also going to explain the TMR surgery in a little more depth . Click here if you would like to watch Kuiken’s TED talk A prosthetic arm that “feels”  and get a head start on the subject of the upcoming post.

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