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Written by: Jeremy Dailami
Written on: May 4th, 2002
Tags: biomedical engineering, health & medicine
Thumbnail by: Xiong Chiamiov/Wikimedia Commons
About the Author
In Fall 2002, Jeremy Dailami was a junior at the University of Southern California pursuing a B.S. in Biomedical Engineering. As a student, he enjoys surfing, long walks on the beach, and aims to pursue a career that involves mass-producing industrial sized microwave ovens.
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Volume III Issue I > The Myoelectric Arm: It's Electrifying
With the help of scientists and engineers, individuals missing appendages can be given a chance to live a life in which their amputee status is an afterthought. The recent progress of prosthetic engineering has enabled scientists to design artificial limbs that function nearly as well as biological ones. On the forefront of this technology is a prosthetic device called the myoelectric arm. What makes this prosthesis so unique is its ability to function with the amputee's muscle movements, reacting accordingly. It enables wearers to pinch, grip, and release objects, unlike earlier prostheses. The device is compatible with daily activities and can be donned and doffed independently.

Introduction

One of the most commonly amputated or missing limbs is the arm, which is used in many vital movements. Opening doors, pulling out a chair, or even rising from bed all require the use of the upper body. The loss of an arm can be understandably overwhelming.
However, with modern technology and the emergence of rehabilitation engineering, the effects of losing a limb are not as catastrophic as they once were. The superiority of today's artificial limbs may go unnoticed, since they have become so sophisticated that many amputees are able to participate in activities that once seemed inconceivable.
Vast technological advances have been made in designing upper extremity (shoulder, arm, hand) prostheses. Progressing from peg arms and hooks, the appearance of electrically powered prostheses has revolutionized the artificial limb industry. These prostheses not only help amputees live normal lives, but also look realistic enough to alleviate self-consciousness (Fig. 1).

Prosthetic History

Afurse/Wikimedia Commons
Figure 1: Prosthetic limbs allow amputees to live normal lives while looking realistic to alleviate self-consciousness.
P​rosthetic devices have existed for centuries. In 218 B.C. the Roman general Marcus Serigus guided his troops against Carthage in the second Punic War and suffered over twenty injuries, including the loss of his right arm. An iron hand was created so he could continue to fight in the war [1].
The American Civil War prompted the establishment of the American prosthetics field. Reports show that there were at least 30,000 amputations on the Union side alone [1]. But the industry soon faded away and it was not until the United States entered World War I that a revival of prostheses production occurred. The industry was further developed by the advent of the telephone and phone directories. Doctors were able to place illustrated advertisements, attracting more customers [1].
In the 1960's, German scientists created the first functional hand, followed by American development of the first working prosthetic arm. However these prostheses were not always well received by the amputee community, due to great user discomfort.

Background

In the United States alone, there are an estimated 10,000 new upper extremity amputees annually [2]. Many of these are trauma-related, some are disease-related, and some are due to congenital deficiencies.
With the exception of children born missing a limb, individuals can begin the process of obtaining an artificial limb immediately following the loss of an appendage. Designing and fitting a prosthesis for an individual occurs in two stages. The first stage involves fitting the amputee with a preparatory prosthesis. This is perhaps the most crucial stage, for it helps the residual limb - any remaining part of the limb - to heal. During this stage, the amputee has a chance to adjust to the artificial limb, which may assist in the final design of the prosthesis.
The preparatory prosthesis is worn for two months. During this time, any sizing problems or other concerns of the wearer are addressed. The next step involves taking the preparatory prosthesis and creating a more durable and long-term prosthesis by molding it from harder materials, then giving the prosthesis a silicon or latex covering.

The Electric Arm

GeeJo/Wikimedia Commons
Figure 2: After an injury in Iraq, Lance Cpl. Brandon Mendez now has a new myoelectric arm.
The most recent additions to the prosthetic field are electrically-powered​ limbs controlled by electrical signals from the body. When first introduced in the late 1960's, electric hands and arms seemed a science fiction dream from television shows such as The Six Million Dollar Man. However the early model of the electric prosthesis was bulky, with a loud motor to control finger movement. These early models were very noticeable, and made amputees wearing them uncomfortable and embarrassed. However in the past four decades, improvements have made such prostheses more inconspicuous. The most popular and advanced arm on the market today is the myoelectric arm.