How Do Prosthetic Hands Work?

If someone lost a limb to due an amputation or from a birth defect, getting a prosthetic hand can help increase the person’s ability to function in a somewhat normal fashion. Depending on the type of prosthetic hand the person chooses, they can perform grooming and self-care tasks, engage in daily activities such as cooking and cleaning, play with the kids, or even play a musical instrument. Today, advancements in design and engineering can help anyone who needs a prosthetic hand have a fulfilling life.

What’s the History of Prosthetic Hands?

black prosthetic hand

Image via Pixaby by Stefan Dr. Schulz

From as early as 77 A.D. when Marcus Sergius, a Roman general, lost his hand in battle and had it replaced with an artificial one that he could use to ride a horse and fight in battle, people have used prosthetic hands to function. Throughout the ages, advancements in artificial hands have improved from body-powered prostheses used after World War I to modern ones found today that use electric power and even intuitive control to make the prostheses work.

What Are the Different Ways to Control a Prosthetic Hand?

Depending on the purpose and use of the prosthetic hand, you have several options of prosthetics and ways to control them.

Passive Prosthesis

This mostly nonfunctional type of prosthetic hand is used mainly for cosmetic purposes. Some of these passive hands can have fingers that the user can bend or reposition if desired. The passive artificial hand is made to match the other hand as much as possible and is then fitted with a vinyl or silicone glove that can match the person’s skin tone. In addition, the gloves are customizable to match what their real hand would look like with matching veins and fingernails.

Body-Power Control

A simple form of movable prosthetic hands uses body power to control the hand. A series of cables attached to the artificial hand and to a harness that the user wears let the person open or close the hand by moving their shoulder or upper arm. This system uses a voluntary opening of the hand triggered by the user, and then the hand voluntarily closes once pressure is released through the cable system.

Myoelectric Control

This functional type of prosthetic hand is called a myoelectric prosthesis. The muscles of the affected arm work together with electrodes fitted inside of the prosthetic hand. When the person contracts the muscles of the limb, electrical outputs send a message to the artificial hand to open or close it. Conveniently, electric-powered hands also let the user change the speed at which they can open and close the hand. With the addition of a wrist rotator, the person can also twist and turn their wrist.

Hybrid Prosthetics

For those who have lost a substantial amount of their limb, a hybrid prosthesis is a viable option. Using a combination of body power and electrical power control, a hybrid prosthesis is best used for a transhumeral prosthetic that can move the elbow, hands, and fingers simultaneously.

Activity-Specific Prosthetic Hands

In general, activity-specific prosthetics attach to an already existing one designed for specific activities, such as fishing, running, sewing, or playing a musical instrument

Advanced Biomedical Engineered Prosthetic Hands

As science and researchers strive to improve prosthetics, you’ll find prosthetic hands that use software, gyroscopic sensors, and high-tech electrodes to help the user move their prosthetic hand.

Bionic Limbs

iLimb and iLimb Digits are multifunctional prosthetic hands that articulate in various directions, including rotating the thumb. With bionic limbs, the user has more use and function of the wrist and individual fingers through the use of computers and specialized sensors.

Ultrasound Sensor Control

Using ultrasound sensors can help the user control movement within individual prosthetic fingers. Ultrasound technology can help those who want or need finite control over their hands, such as someone playing a musical instrument or when performing intricate finger work. Unlike electromyogram sensor-controlled prosthetic hands that require pressing buttons to change modes, ultrasound control lets the user move their fingers spontaneously.

Intuitive or Mind-Control Prosthetics

One of the most advanced prosthetic advancements today is using intuitive control to move the hand. This device uses residual nerve input from the limb ending to control the prosthetic hand. When the user thinks about moving the hand or fingers, the brain sends the message through the existing nerves into electrodes inside of the prosthetic to engage movement without any external help.

How Are Prosthetic Hands Fitted?

Prosthetic hands range from cosmetic to functional or even activity-specific. While cosmetic prosthetic hands offer little in the way of helping someone perform specific tasks, they do help to make the missing limb look a bit more natural. With a functional prosthetic hand, and depending on how the user controls it, someone can pick up objects, perform self-care tasks, or play music and sports.

Many prosthetic hands are custom-made to fit the person’s limb. Depending on whether the prosthetic fits on the arm below the elbow, a transradial prosthetic, or above the elbow, a transhumeral prosthetic, the device uses sockets, liners, suction, or a system of cables to attach the prosthetic device to the limb.

How Often Does a Prosthetic Hand Need Replacing or Re-Fitting?

Depending on the type of prosthetic hand and types of use, your prosthesis can last for several years. When you first experience an amputation, changes to the limb occur that require either changing the sockets, liners, or even replacement of the initial device. Once the amputated limb stabilizes, your prosthetic hand normally lasts between two to four years.

While the loss of a hand is traumatic, having a well-fitted prosthetic hand can help you function in a normal manner. With modern and innovative biomedical designs and engineering, you have several options of the type of prosthetic hand to fit your needs and lifestyle. If you or someone you know or love requires more information about how prosthetic hands work, feel free to contact our professional team at Scheck & Siress. We’ll evaluate your needs and discuss the best solution and option for your prosthetic hand.