July 21, 2025

Sophie Hsieh 

11th Grade

Fountain Valley High School

Humans have been using prosthetic arms to aid amputees in regaining some sort of aesthetic appeal and basic functioning for thousands of years. The most basic of prosthetic arms today, the passive arm, serves a primarily aesthetic purpose. The arm is custom-made out of silicone and is modeled to look like a real arm, and can help in basic functioning, such as pointing or waving. A version that allows for more function is the body-powered prosthetic arm, which is not as aesthetically appealing as the passive arm. However, by using a series of pulleys and harnesses connected to other portions of the body, users have the ability to open and close their prosthesis, allowing for more functional control. As of recently, a new prosthesis has entered the game: the myoelectric prosthetic arm. Through the use of electrical signals from the amputated limb, a myoelectric prosthesis provides users with the most control over their prosthesis.

In order for you to have clicked on this article, you had to have executed some sort of motor function with your hand. Neurons at the neuromuscular junctions of your forearm and hand fired, releasing the excitatory neurotransmitter acetylcholine, which your muscles responded to by contracting, causing the movement that allowed you to click on this article. Now imagine your hand was amputated, the muscles in your forearm would contract, but nothing would happen because there is no hand to move. So what if there was a prosthesis that could interpret this muscle contraction and provide a prosthetic hand that would carry out the movement. That is the idea of the myoelectric prosthesis.

Electrical signals, called electromyographical (EMG) signals, are released when your muscle contracts. These signals represent the intention of the user: to point, grab, push, etc.  Electrodes are attached to the surface of the amputated limb, which detects and collects the EMG signals, then relays them to sensors within the prosthesis. The sensors can then use these signals to create a movement within the prosthesis that replicates the intended movement of the user.

The myoelectric arm cannot fully function in the way that a natural hand does, however. Due to the lack of a hand, which contains an abundance of muscles that aid in further motor control, it is difficult to achieve fine motor control in the fingers. Additionally, the non-invasive approach of placing electrodes on the surface of the limb is limited in the locations where they can receive EMG signals, consequently resulting in a decreased degree of control. However, there is a surgical approach that places intramuscular electrodes where there are more locations where they can receive EMG signals, allowing for more dexterity.

Overall, myoelectric prosthetic arms allow amputees greater ability in the everyday tasks of their lives, such as picking up a cup or grabbing something out of the fridge. By taking advantage of advancing technology, companies have been able to provide amputees with a better quality of life. As technology begins to advance further, it is likely that more versions of the myoelectric arm will develop, with increasing dexterity, control, and accuracy.