1. dracodomitor
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    dracodomitor Member

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    How would growing out of a prosthetic work?

    Discussion in 'Research' started by dracodomitor, May 21, 2016.

    So one of my young main characters has a cybernetic arm (think...hm, the Winter Soldier if you need a visual reference) and being twelve, obviously is starting to mature and go through growth spurts. It's quite an important plot point that he begins to out-grow his prosthesis, but since such a thing doesn't exist I'm not sure what damage it would do.

    I know the basics; the skin starts to feel tight and painful, the arm itself wouldn't work as well, but I'm wondering what internal damage there would be, if any.

    Help would be appreciated, even if it is theoretical.
     
  2. Cave Troll
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    Cave Troll Bite the bullet, do your own thing. Contributor

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    It would be the same as growing out of a pair of jeans. You would be to big to accommodate the excess mass, so buy a bigger pair of pants. :supergrin:

    You could cause nerve and bone damage if you did not update as needed, and there are health risks involved such as: muscle death, gangrene, a staph infection, and I am sure the list could go on for a while. But I think you get the idea that it would be highly unpleasant for the person. Worst case if left untreated is death, and not much really comes after that symptom. :p
     
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  3. Mumble Bee
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    Mumble Bee The writer formerly known as Chained. Contributor

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    If your question is mainly concerning 'damage', i'd assume with something as futuristic as a 'winder soldier' arm there wouldn't be much

    Pain on the other hand? There's probably be a bit of that.. Disconnecting the old prosthetic and connecting one to all of the necessary nerve endings... My experience with FMA tells me that would produce, and this is a metric unit, loads of pains.
     
  4. dracodomitor
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    dracodomitor Member

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    Thanks for your help, guys!
     
  5. Nidhogg
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    Nidhogg Member

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    In general, the biggest issue would be discomfort and pain. Think of it this way- you've got a metal object constraining your growth, and your body is trying to push against it in order to expand outwards. There will be a lot of pain over time, as well as the other effects mentioned by @Cave Troll

    If the growth issues were to leave open sores or wounds, there would also be issues with disease that could occur. I'd imagine the first signs of anything being wrong would be redness and tenderness around the connected tissue- whilst this may be a bad analogy, a similar thing occurs when you wear braces and your teeth start to move around the mouth into places they're not used to being in- redness, tenderness, and a higher susceptibility to stimuli being interpreted as painful. Depending on how bad things got, this could be used as a plot point, as the tissue connecting the prosthetic to the body would be a big weak point in terms of physical pain.

    Another thing to consider is just how attached is the prosthetic? If there are wires and the like inside the human tissue due to its cybernetic nature, then they could cause issues with nerves and muscles as the body changes in size.

    From some quick background reading on prosthetics, it sounds like adolescents get regularly checked (if possible) to make sure everything fits properly, due to the changes physical shape. With this in mind, it may be worth considering why the protagonist may not get their limb checked up on, so as to avoid the negative impact of ill-fitting limbs.
     
  6. Jack Asher
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    Jack Asher Wildly experimental Contributor

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    At first I was confused by the title, there are children with prosthetics all over the world. Growing children who regularly out grow, and need new, ones.

    More importantly, we are now beginning to see the first "cybernetic" equipment, using EEG brain mapping, and there is a real chance for some of this technology in the near future. But I don't think any of these responses come from a medical or scientific understanding of these concepts.

    Sorry guys, this is going to get long.

    For a start, I imagine that you (and others) envision some kind of nerve connection for the cybernetics. This makes some kind of sense, our nerves are basically wires, why not just hook them up to a machine. The problem with this is that we really don't understand much about how nerves actually work. We know that they've chemical electric, and we know that they release chemicals from one ending (axion terminal) to the next (dendrite). How those chemicals actually work, we don't understand at all. More importantly from a constructive standpoint, is that we don't know how the signals on a nerve ending know where to go. Your spine is on huge collection of nerve cells, but as far as we can trace, those cells send signals along random pathways, and these somehow know where to branch to get to where they are going.

    Clearly for this technology to work, much much more needs to be understood about the nervous system. In this fashion.

    But I mentioned above that we're already working on proto-cybernetic prosthetics. They just don't work in the was you're anticipating. We can't understand the way nerves work, but we can understand the way the brain works.

    Actually that's a lie, we have no idea how the brain works.

    But we can read brain activity! We have a whole bunch of sensors that do that, and they can read surface signal activity on the outside of the cortex. Conveniently this is where almost all of your sensory control areas are located on the brain.

    The setup is fairly simple. You hook your brain up to an EEG, and program it. The programmer tells you to think about raising your hand, the EEG records the brainwaves that mean "hand=raise" and the programmer tells the arm that that's what hand raising looks like. While this technology is in its infancy, it already shows amazing fluidity. Here's a monkey eating a banana with a robot arm.

    Notice that while the robot is a little uncoordinated, it's not jerky. The monkey is able to control his arm with unconscious motion, just like a real arm!

    There's even potential for the arm to send signals back into the brain. At first they would be read is an uncomfortable sensation, but all of our research in behaviorism and fluidity indicates that these would resolve themselves very quickly into feelings that would be indistinguishable for real physical sensation or pain.

    So no, you don't have to connect every nerve ending, and Full Metal Alchemist is not a realistic depiction of cybernetics.

    Of course we have to go much father with this line of thought. Your child must have a stump. It's easy to imagine that, like the Strogg, or the Borg, the cybernetics would interface seamlessly with the flesh. This is impossible from pretty much every understood perspective. The blood supply has to be cut off, the immune system can police metal, and the muscles on an amputated limb slowly die off. Were you somehow to connect the structure of the prosthetic to the bone, you'd have to stave off the constant risk of infection.

    So there has to be a stub, the stub has to be covered in skin, and must therefore be washed, frequently. A permanent arm, like Luke's in Jedi, is not really a possibility.

    So we can look at what children with amputations go through right now, even though the technology "doesn't exist yet."

    Their stump is constantly changing. This is true of any amputee, it's normal to need a new prosthetic every 3-6 months at the start. After a couple of years this might go down to 6-18 months. For a growing child? It's more like 6 weeks, and every time they go in they'll need a new socket. A difference as small as a millimeter between the shape of the socket and the shape of his arm can be excruciating after only a few hours. Imagine a wrinkle in your sock that's impossible to fix, and which is there for a week, for perspective.

    For an adolescent an amputation and prosthetic is particularly difficult. Their bones are still growing, but their muscles are not. The muscle on a stump can't be exercised, atrophies and dies, so an adolescent stump looks pretty weird pretty fast.

    Sorry, that's not really pertinent, just kind of a thing.

    But what this bone growth means, is that the relative length of the limb as a whole is changing, but at a different rate than the other limb. It an imperfect comparison (being between legs and arms) but the difference of a couple of a fractions of an inch is immediately perceivable when you put on a shoe with an insert, and one that does not.

    Your boy has two different sized arms, and it's gonna annoy him like hell. The brain is able to keep up with small differences in limb size, but remembering that one set of fingers is a half inch longer than the other is difficult enough for the conscious mind. He'll have all kinds of difficulties with typing, or picking things up, or doing anything that requires fine motors, and he'll have to adjust constantly, as one set of fingers grows longer, one stays the same, but the arm gets longer, and then every 6 weeks their the same size, and the process starts all over again.
     
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  7. GingerCoffee
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    GingerCoffee Web Surfer Girl Contributor

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    I don't understand how you think "such a thing doesn't exist." Of course it exists. @Jack Asher's done a good job explaining the process. I'll just add some sources:

    Here's a company (for an example):
    Prosthetic Care for Child Amputees

    Another commercial site:
    Pediatric Prosthetics

    And here's a recent innovation for children with internal protheses because not all protheses are external:
    Outcome of expandable prostheses in children.

    It might be useful to actually read up on the subject:
    Introduction to the Child Amputee
     
  8. ChaosReigns
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    ChaosReigns Be Still and Know Contributor

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    I've done a little research like the guys above (i did a presentation on Smart prosthetics in one of my units for uni) and generally speaking, prosthetics are designed to have some ability to allow growth in them (as the affected limb can swell on occasion due to varying factors) so there is some leniency there also common logic would be that as the child was getting too big for it they would be refitted for a new one (albeit smart prosthetics aren't cheap, the ones I was looking at were circa £50,000)

    I don't know exact details on what they would do with kids, as I was looking in general (and more than happy to supply you a copy of my script where I go into a little more detail on smart prosthetics, including my sources)

    I don't know how much that helped but I hope you find what you are looking for

    *note* The prosthetic I was referencing earlier was this one here
     

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