Hi all,
Pardon my ignorant question but is it possible for something to be pulled hard enough against the skin by an implanted magnet to cause damage or restrict blood flow?
What about if someone brinks another strong magnet near the implanted one?
Yup, definitely. They’ll pinch together and restrict bloodflow. If you leave the magnet there long enough you’ll get necrosis
I just call out to @Eyeux , for exactly that happened to him… I’ll let him tell the story, but let me tell you this - it wasn’t good… 
For “attaching” something to an implanted magnet, @Satur9 already said the most important thing - there is no way to do that without damaging your body, and the timeframe for that is a lot smaller than one would expect.
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The cochlear implants use magnets to attach the exterior unit to the side of your head. They avoid the whole necrosis problem my mounting the interior magnet to bone, while distributing the force of the exterior magnet over a large area using a plastic ring.
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Yeah okay, but that is pretty much out of reach for DIYers or bodymodders, so… I was more talking about stuff we all can do
The use of implantable magnets in medicine is something entirely different, of course.
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Oh sorry, I wasn’t arguing with you. It just seems most people end this line of questioning with “how do cochlear implants do it?” So I just wanted to nip that in the bud.
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Thanks for the shout! been way too busy with work to properly scour the forum lately! >.<
You are right on that one! Definitely wasn’t a pretty one! 
So…
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I Implanted the magnet in my wrist, outside of it.
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Then I’m handling some sensitive equipment, which includes a very powerful magnet mounted in some brackets.
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Brackets break from wear and tear and large magnet falls. Gravity did most of the work there, but the titan surely helped steer the magnet straight into my wrist!
On any other day it would just hit my soft bits, the impact would get distributed through the jiggly flesh, and we would just curse a tiny bit.
Yet… instead of hitting soft flesh, the magnet encountered a tiny lump of titanium coming against it in equal force… leaving only a thin layer of skin in between, which obviously broke. (as in breaking skin. aka cut and bleed).
The implanted magnet was still implanted by then (YAY!), but got dragged closer to the surface, leaving a larger and stretched out pocket… and the skin rupture wasn’t recovering so well…
So I decided to remove the Titan.
I thought of removing it properly, with plastic tweezers to hold it in place while I would cut the pocket open with a scalpel…
But before that, why not have some fun testing how the Titan flips around on itself near a large magnet…
And justlike that I ended up yanking the Titan out of myself…
Wasn’t subtle. I definitely let my morbid curiosity get the best of me! 
But I used nothing else but a large magnet. (and the broken skin from the previous accident, which hadn’t sealed yet by then)
Since someone stirred up this wasp nest… 
That is very true…
So here it is a simplified explanation of the main mechanism behind the main (but not only) cochlear approach
On the left side you can see what happens when two magnets, or even a magnet and a metallic object, get in contact.
Your skin will be pressed over a tiny area (only the contact points), and will slowly get crushed. if it’s a quick interaction it’s nothing to worry about, but if you leave it long enough…
it would be basically the same thing as keeping a tight pinch on your skin.
Just like with pinching, if you pinch just a tiny bit of skin it will hurt a lot more than if you pinch a large chunk of flesh together…
So with magnets it’s the same thing:
The deeper the magnet is implanted the more “meat” will be between it and the skin, thus less damage. Yet then the “weaker” the field effect will be felt at skin level… so there’s a trade off.
Another factor here is the surface of the magnet. Larger surfaces distribute better the force, thus causing less damage…
Which takes us to the image on the right: A simplified version of the cochlear implant.
By bolting the magnet to the bone you make sure it won’t be moved closer to the external magnet, so you won’t have the localised pinching and by mounting the external magnet in a skin-friendly mount you keep that from trying to “sink” into the skin.
The mount being a disk shape will also increase the strength distribution causing much less harm to the skin.
This setup also avoids another issue with magnets: the closer they are the more intense will the attraction be, which is a vicious cycle in the left image.
So by keeping the distance constant you keep the attraction in check.
So…
Why don’e we use the same approach with regular magnets?
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Bolting something to bone will damage your fleshy bit unless it’s done somewhere with almost no mobility, such as the skull. As someone who had a needle stuck to the Knee bone I can attest: each millimetre of movement was a new level of agony.
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keeping the magnets at a “safe(-ish)” distance also causes the “attachment” to become quite weak and fiddly, and any bump would make the external magnet fall.
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Cochlear implants are not worn 24/7, which leaves room for the skin to recover.
And then the most important reason:
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Thanks for the detailed image!
I’m curious about magnets, in particular as I work in the electrical engineering field and wonder if I could feel the field around a live cable etc but the part where you have to remove them for an MRI scares me (a lot)!
I’m also an electrical engineer, and I get a lot of use out of my fingertip magnets during the course of my work. Detecting live wires (with current flow), locating transformers, finding magnets embedded in enclosures, and picking up small steel parts like screws and cheap THT components. It’s good fun. I won’t be taking mine out for any MRIs
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Do you not have to?
In the sense that you aren’t legally required to go through an MRI, yes
I think the idea is to try to aim for more magnet friendly medical procedures
You don’t have to do anything. I’m interested to get an MRI with the fingertip magnet installed to see how it is. My understanding is that it will be uncomfortable and may reduce the strength of the magnet a bit, but it likely won’t become a projectile.
What are they gonna do, cut it out of me against my will? I’ll just tell them, and if they won’t let me proceed then I suppose they’ll have to find another diagnostic tool.
Question that never occurred,
Are recipients of cochlear implants unable to have an mri?
I presume those magnets are far more difficult to remove
Edit,
Google says “it depends, but it’s not a great option”
And they’re right next to their ear! What idiot would voluntarily do that!? How are you supposed to get a head MRI? Good thing people don’t put like magnets in their tragus or anything, cause that would be crazy
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I mean… sarcasm obviously
But the magnets are on the back of the head no?
i think they usually are right behind the ear
If I am not mistaken (and please correct me if I am):
Individuals with a Cochlear implant can still get an MRI, but…
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It won’t be just any MRI machine that they can use
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There will be a series of procedures to be performed prior to the scan (based on both the implant and the MRI machine fabricator’s procedures)
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The biggest issue in this case is that the Cochlear magnet will disrupt the image… The fear of “the magnet becoming a projectile” should not be the case because the magnet is bolted to bone, therefore the magnetic pull necessary to rip it out is much higher than you would expect from an MRI session…
… Which brings us to the issues with sensing magnets:
They are, by design, left “floating” within our squishy bits (so that you can feel it’s displacement), and said squishy bits require less force to be burst through.
Usually this should not be a big issue. All you should experience is some small form of internal injury as the magnet moves itself, which your body will heal by itself (potentially leaving a more laxed pocket, causing scarring, reducing sensing…). The closer you bring it to the actual MRI, the worst this will be.
And regarding the “projectile effect”, although it is a possibility, usually our magnets are implanted deep enough and our skin is flexible enough to keep them in place.
Although this is mostly an assumption, so please do not take my word as a rule.
I am also to expect that angles and pairings will play as much a role here as field strength. Immagine an XG3 for instance. if the pull causes it to be moved sideways, the long area of the glass tube will make it so that almost no harm will come from it. Yet… if the pull happens on the tube’s z axis, pulling it straight from the “top” (the rounded upend of the tube), then it is way more likely it can dig it’s way out of your body! (more strength concentrated into a much smaller area)
Also worth noting… Always tell your MRI technician that you have a magnet! Because if you are the unlucky winner of the fingergun lottery and destroys the MRI machine in the process (aka your magnet does become a projectile), it is bad enough that you are hurt, but much worse if you also have to foot the bill for an insanely expensive machinery! (which, if you omit the information about your magnet, will become your fault)
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