How do prosthetic limbs work? Are they connected to your brain or something? How do you make them move?
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For arms, body-powered prosthetics have been available for decades. Folks learn to use chest, shoulder or other muscles to open/close the hand or hook, move the elbow, etc.
More recently myoelectric prosthetics were developed. These use electrical sensors to detect muscle movements and then move the limb using motors and batteries.
So the answer is, sort of, the newer prostheses are connected to your brain in the sense that they make use of your brain’s ability to generate impulses through your nervous system to existing muscles in your body and “repurpose” those signals to control movements of your prosthetic. But I’m not aware of anything that’s commercially available that comes anywhere close to the Cyberpunk or Deus Ex version of cybernetic devices. We’re still a ways off from understanding the brain well enough to wire modifications directly to the brain.
It depends on the type of prosthetic!
Most prosthetics are static, with legs being the most common example. The majority of prosthetic legs are basically well-engineered, very ergonomically-designed wearable crutches. The wearer can’t control them much, beyond moving whatever body part it’s attached to.
Some people have prosthetic hands/arms that are completely passive/immovable — just there for cosmetic reasons or general comfort/balance.
Okay, **moving on to more advanced prosthetics with movable appendages.** The most common ways that prosthetics can move are:
– Manual, lockable prosthetics. For example, an elbow that can be moved (e.g. manually with your other hand) into a bent position and then locked so that you can carry something.
– Cable-controlled prosthetics. For a long time this was the most advanced sort of upper limb prosthetic we had. The prosthetic is hooked up to a harness that the wearer puts on, which allows them to control the prosthetic through small movements of the body (especially the opposite shoulder). Small movements pull on cables to, for example, open or close a prosthetic hand.
– The most modern prosthetic technology includes prosthetics that can be controlled by…well, basically, leftover nerves. [These are super new and not very widely available.](https://www.michiganmedicine.org/health-lab/its-you-have-hand-again) Some very smart scientists figured out how to hook up prosthetics to leftover nerves in the upper limbs of partial amputees. This allows the wearer to control the prosthetic with their brain — the brain sends signals to the nerves, which tells the prosthetic what to do. Just like how you tell your arm and hand what to do!
There are a lot of other, more specialized types of prosthetics out there. Many folks who use prosthetics have multiple options depending on what they are doing — for example, a different prosthetic leg for exercising vs going to work.
It’s a rapidly evolving field!
I work for a company that makes myoelectric hands, so I can tell you a bit about those but I don’t know much about other types. We have two basically touch pads, one to send “open” signals and one to send “close” signals. These are mounted somewhere the person has enough control to be able to do press them with varying degrees of force and patterns (like rapid multi tap sort of patterns). How forcefully the sensor gets touched controls the speed of the motion.
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