There are all sorts of prosthetic arms available, but almost all offer some range of motion. Individuals who choose to wear a prosthetic tend to do so for the sake of convenience, and so movement is a necessary component in giving the prosthetic a function in their daily lives.
In short - Yes! Prosthetic arms can move!
Of course, there are exceptions, and the extent to which a prosthetic can move depends on its engineering, and what the user wants from the prosthetic device. Traditionally, a prosthetic will reduce its movement capabilities in order to more closely resemble its organic counterpart and vice versa - though with constant innovation in the field of prosthetics, these boundaries are always being pushed.
While the means of control in prosthetic arms is the easiest way to distinguish them (as we will explain in this article), it's important to note that not only is there a range of options available in each style, but many individuals who wear prosthetics own multiple different types of prosthetics. This is so that they can switch design based on what task they need to perform, thinking of prostheses as 'tools in a toolbox'. Different technologies are better suited to different scenarios, so there's no need to agonise over the compromises of one over the other.
So how can prosthetic arms move?
The original means of making a prosthetic arm move are body-powered and motor-powered prosthetics.
Body-powered prosthetics use a harness with cables to manipulate the arm. This means they're fully unpowered, which makes them well-suited to more rugged environments. The mechanical nature of the arm means that despite being the less-advanced technology, they still remain popular. The cables attaching to other parts of the body (generally the opposite shoulder, if possible) means body-powered arms can require a bit of practice to get precise movement down.
While body-powered prostheses may require an initial skill investment, you may be surprised how quickly moving them becomes second nature and part of everyday life. Children, especially, can adopt the use of prosthetics much faster than one would think - which is why it's often encouraged for children to start wearing a prosthetic as soon as they feel comfortable doing so.
Body-powered prosthetics can come fitted with hooks or hands. While hands look more natural, hooks can offer many advantages in terms of function, and are often preferred for manual jobs. It's always worth your time to experiment and find which is the right fit for you.
The next step is a motor-powered prosthesis. Like body-powered arms, these rely on the remaining muscles in the upper arm or opposite shoulder to control the arm - but in this case, they are used to press buttons or switches to control the arm with electric motors. The result is a prosthetic that is less physically taxing to use, but takes a little longer to get to grips with.
Running on a battery, motor-powered prosthetics need to be charged regularly, and they can be pretty loud which some people find awkward in social settings.
Are there more advanced options?
Myoelectric prostheses are controlled via electrode sensors placed on the skin, which detect muscle contractions and generate an electrical signal, which triggers the arm to move.
The signal these electrodes detect can be confused or weakened, especially if the sensor gets moved or dislodged or if something like sweat comes between the skin and the electrode contact. That just means the technology isn't perfect yet -- there are still new innovations and designs in the field which are working to solve these problems, and they are still the choice best suited to some patients.
Depending on the individual's remaining muscle function, myoelectric arms can be fitted with a hand that can articulate each finger individually. This degree of control is the value individuals are often seeking in this option.
For any prosthetic, though, there is forward progress. Many prosthetic options now offer modular hand attachments, allowing the user to handle a different task without needing a whole separate arm or to rely on the prosthetic just for grip. These range from helping with everyday life activities like brushing teeth and combing hair to outdoor activities like playing golf or even motorsports - for example, the Mert Lawwill device was designed to allow those who have a passion for bike racing to pursue it with a quick-release handlebar attachment.
This is just one of many examples, the takeaway being that there are many specialised attachments made for different scenarios. If you've been trying to learn a new skill but your current prosthetic has gotten in the way, it's always worth checking to see if there's an attachment out there that will make your life easier!
Looking to the future - bionics and beyond
Building on the technology in myoelectric arms, teams of scientists have been working on implanting electrodes (rather than attaching them to the skin) in order to better the connection between the user and their prosthetic device. This tends to improve the accuracy and precision that the prosthetic can achieve, though it requires this minor surgery to set up and is very much still in the experimental stage.
When someone asks "can prosthetic arms move?", they are generally thinking about the even more experimental technology that often makes it onto the news - the 'true' bionic arms that can be moved just by thought. The way these work differs, as research is still ongoing into many different designs at the same time, but generally the idea is to embed the electrodes in the brain to read the neuron signals generated when a patient would move their arm.
Of course this is a very invasive medical procedure, and currently the teams working on these prototypes rarely let the volunteers take the arms home (to give a clue as to how early in development these devices truly are). These robotics projects are still incredibly new, which is why they often make it into the news.
There is innovation in prosthetics outside of these experimental medical ideas, though. For example, Esper Bionics is one of many companies working on the implementation of AI to better control the hand. With machine learning, the arm will be able to adapt to suit the user by memorising which results they expect from different inputs (controlled with myoelectric implants) - to the point where moving the arm feels like second nature, or at least more intuitive than older myoelectric devices which users had to learn to use effectively, and alter inputs to match their desired results.
The advent of 3D printing technology has led to rapid innovation in the field of prosthetics. Arms like the ExpHand have been made possible thanks to the availability of lightweight, durable, 3D-printable materials. The dramatically reduced cost versus injection plastic moulds means that projects like ours can be prototyped and manufactured at a greatly reduced price, making prosthetics more accessible and affordable than was possible before.
Which prosthetic is right for me?
So, as is hopefully evidenced - the answer to "can prosthetic arms move?" is a resounding "yes, they can"! If you're thinking about a functional prosthetic you may want to ask which of these options is 'best' - we want to make it clear that there is no one fit for everyone, and that everyone's needs are different. While the forefront of myoelectric science is exciting, they are still extremely expensive prosthetics that simply aren't accessible to most people. Body-powered prosthetics are incredibly practical in day-to-day environments, but some users might feel held back by the limited finger dexterity.
As we discussed at the top of this article, many people who use prosthetic arms have a collection of options which they use depending on the situation, and the easiest way to learn which suits you best is to experiment.
And besides, trying out a new prosthetic should be an exciting prospect! If you feel confused you can always reach out to a prosthetist for more information about your options, and more tailored guidance as to which is likely to suit your lifestyle the best.
If you think the ExpHand would be a good fit for your child, you can sign up for our beta trial here, or learn more about prosthetics from our FAQ page here.