How Does a Prosthetic Arm Work?


Prosthetics, or artificial limbs, are used to replace limbs that were lost or absent limbs from birth. They enable those with congenital limb differences and amputees alike to improve function and mobility. Due to advances in medical science, prosthetics have improved and are capable of remarkable things.

What Are the Components of a Prosthetic Arm?

A person with a prosthetic arm sitting down

Image via Flickr by TechCrunch

A prosthetic arm consists of several components that work together to make the arm useful, including: 

  • Limb. The limbs of a prosthetic arm are formed out of lightweight, yet durable materials.
  • Socket. The socket connects the prosthesis to your residual limb to ensure that it fits securely. A poor fit can cause you considerable discomfort and reduce the function of the prosthetic arm. To circumvent this problem, prosthetics are made using a personalized mold to fit the exact shape of your residual limb.
  • Suspension system. The suspension system is the component that secures the prosthetic to the residual limb. There are different suspension systems, including a harness, an elastic sleeve, a suction socket, or a self-suspending socket.
  • Control system. While the brain controls a natural limb and nerve impulses, a prosthetic arm can’t be controlled the same way. Control systems are myoelectric, body-powered, or motor-controlled.

What Is the Process for Fitting a Prosthetic Arm?

If the residual limb isn’t fully healed, a physician will prescribe a cloth shrinker to control swelling. During an initial appointment, you’ll meet with a prosthetist who will formulate a patient profile by learning about your pre-amputation activities and your goals for the future. This information determines an appropriate design to match your unique needs. A proper prosthetic fitting is essential for you to achieve their goals, whether to aid you in their regular daily activities or use the limb for work or sports.

Once healed, your surgeon will provide you with clearance for your prosthetic, which means that you’ll be able to start the casting process. Your prosthetic arm will be hand-casted to the exact shape of your residual limb. Casting is vital to ensure your prosthetic has a proper socket fit, which means you’ll have reduced or no discomfort, and superior functioning of your prosthetic arm and hand.

Next, you’ll have a series of fittings in a diagnostic test socket (DTS.) A diagnostic test socket is made of transparent plastic and is used to confirm that your socket fits properly. This stage of testing is used to fine-tune the alignment and the socket fitting of your prosthesis. The findings from this process will then be transferred to your definitive, final prosthesis.

After you get your new prosthesis, you’ll start working with a physical therapist. A physical therapist helps you learn how to use your new prosthesis. Working with your physical therapist will help you gain more mobility and better control of your prosthesis. It takes time to adjust to a prosthesis, and physical therapy ensures you’ll be successful and get the best usage from your prosthetic arm.

Choosing the Function and Appearance of Your Prosthesis

Whether you have a congenital limb difference or if you’re an upper limb amputee, you have options for the appearance and function of your prosthetic arm. The best choice for you depends on your level of limb loss and your intentions for using your prosthesis.

Passive Prosthesis

A passive prosthesis is designed to look like your natural arm, hand, and fingers. They’re lightweight and don’t have active movement. However, they can help improve your functioning by acting as a steady surface for carrying objects to assist your sound limb. Your passive prosthesis will be covered with high-definition silicone that’s custom painted to look like your arm, hand, and fingers. This prosthesis is an aesthetic choice to give you greater confidence in your appearance, to help your clothes fit better, and so on.

Multi-positional

Joints that are multi-positional can combine with a passive prosthesis to enable you to position your finger, wrist, elbow, or shoulder joints for you to achieve greater functionality. For example, you can use your good hand to place your prosthetic at a specific angle to assist you with holding or carrying an object. The option of a multi-positional wrist, elbow, or shoulder joint enables a greater range of motion. Finger joints can be moved into specific positions allowing you to grasp and use small objects, making them extremely useful for your day-to-day tasks and activities.

Body-powered

A body-powered prosthesis may be the right choice if you engage in manual labor and need the basic function and durability that a body-powered prosthesis offers. It’s a prosthetic that favors function over form or appearance.

Electrically-powered Prosthetic Arm

An electrically powered prosthesis uses motors and batteries to transfer the desired movement and power to the prosthesis. Depending on your level of limb loss, the electrical components will vary. Sensors and varied inputs function by detecting motion in the muscles in your residual limb or upper body. These then signal the motor within the prosthetic to perform the movement you want. You’ll have the option of covering the electrically powered prosthesis with a cosmetic glove. These come in a wide array of flesh tones and can even be uniquely customized to match your remaining hand.

Hybrid Prosthesis

Another option is a hybrid prosthesis, which employs a combination of electrically powered and body-powered components into one prosthesis. This type of prosthetic can give you greater function. It’s advantageous if you have a higher level of limb loss, which means you may need more than one moveable component. A hybrid prosthesis can increase your arm and hand’s functionality for work or any other physical activity.

Activity-specific Prostheses

Activity-specific prostheses are designed for activities where none of the other prosthetics work or are too likely to be damaged by a specific action. They’re designed specifically for certain activities, such as sports, hobbies, work, and other specialized activities. You may have seen these types of prosthetics on professional or amateur athletes. They’re designed to be durable and with particular functions in mind. They are most often a supplementary prosthetic, used alternating with one of the other types of prostheses.

With these varied options available, you’ll undoubtedly find the right prosthetic to meet your needs. Due to the strides made in the science of prosthetics, you have a greater chance than ever to live a full, productive life engaged in whatever vocation you desire and the ability to enjoy greater independence, sports, and recreation. Your prosthesis can be your passport to a whole new life without limits. If you or a loved one wants more information on prosthetics, reach out to the knowledgeable team at Scheck & Siress. We’d be happy to discuss your options with you.