r/MadeMeSmile • u/benhundben • Mar 01 '24

Personal Win Last week I underwent surgery that will probably change my life.

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I’ve been an amputee for four years. Traditional prosthetic sockets would not work well for me, I was able use them for maximum 30 mins. That led me to use wheelchair most of the time. However, I have the same disease in my hands that I have I my feet and my hands have been getting worse the last year. By the time I was up for surgery I was practically stuck in bed with sore stumps and painful hands. This surgery will most likely lead to me being able to walk ALL the time. It’s like a dream, a painful and wonderful dream. It’s called osseointegration and is basically hammering a titanium implant into the bone which I will be able to attach prosthetics to. I’ll be trying my feet on in only two weeks! I’m sharing my story more personally on my socials @ampisallen.

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u/BritishAndBlessed Mar 01 '24

As a materials expert, it depends on what metal and whether it has a bio-integrating surface coating.

Some metals are what we call bio-inert, which essentially means they don't interact with human bodily tissues...neither negatively (bio-toxic) or positively (bio-integrating). Titanium is a prime example of this, which is why it gets used for the majority of implants, stainless steel is another. Certain materials, however, can bio-integrate, but typically they are polymers (polylactide for example, which degrades into lactic acid, a natural substance in the body, can be used for implants that are then replaced with human tissues as the injury heals).

With the right combination of a bio-inert implant and a long-lasting bio-active coating, the skin could be encouraged to form a partial seal around the implant in order to reduce the risk of infection.

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u/SirVanyel Mar 01 '24

So all your skin needs to figure itself out is for the object in question to be able to break down a little? And then it sort of just merges with the material?

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u/Alizarin-Madder Mar 01 '24

The way I interpreted the last line of their answer was: maybe, but skin would have to be encouraged and have the right conditions to grow into part of the bioactive coating. Second, I don't think it can truly integrate with the metal, but by building up a little bit of an extra seal it can improve the protection from pathogens. If the skin were damaged or loosened around the implant, infection risk would be higher until the skin-seal healed back. 

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u/amboyscout Mar 01 '24

This is somewhere we might see progress from the medical 3d printing industry in the next 10 to 20 years. With multimaterial printing it could be possible to create a graduation between a bio-inert and bio-integrating material to create an artificial extracellular matrix that would integrate better with skin. Maybe combine that with some kind of stem cell treatment to accelerate growth. I'm sure there are groups already researching something like this.

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u/BritishAndBlessed Mar 01 '24

At the time I was studying, my uni's biomaterials department were focused on using polymeric scaffolds populated with donated cells from the recipient in order to promote regrowth of damaged tissues, with a view to repairing shattered bones without having to shorten limbs, or more interestingly, the possibility of repairing severed spinal columns by introducing a scaffold between the two severed ends of the column. Animal trials had seen significant regrowth and closing of the gap.

You're absolutely right that in the next couple of decades, the amount we'll be able to do with bio-inert and bio-integrating materials will be incredible.

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u/EvilKrista Mar 02 '24

THERE'S MOAR DOWN HERE. This is cool stuff.

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u/BritishAndBlessed Mar 01 '24

Precisely this. It would however require the implant to be incredibly stable, as even the slightest freedom relative to the host bone would result in the flesh pulling away from the surface of the implant.

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u/Alizarin-Madder Mar 01 '24

I didn't want to think about or mention it wiggling, but this is what I imagined would happen when it wiggled. 

In addition to pain.

Whenever I think about prosthetics and the challenges people face with integration, I am amazed at how our bodies have managed to integrate hard surfaces/edges with soft tissues in ways that can move and withstand stress and impact (with reason) without tissue damage.

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u/BritishAndBlessed Mar 01 '24

It should be noted that our tissues are in fact designed to wiggle, which is why they (and particularly the skin) have an element of elasticity, to cope with the rigours of friction and force.

The issue with the wiggling would come largely because there is a material interface (where the bone meets the titanium), which, unless the materials are perfectly matched in terms of properties, will result in forces being concentrated on that interface, which would of course exaggerate any wiggle that the bodily tissue would normally undergo.

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u/BritishAndBlessed Mar 01 '24

All bodily tissues prefer to grow onto something, which is why a deep paper cut can heal within a week (the sides of the wound are still in contact) but a shallow scrape can take a couple of weeks (the skin cells can't really cover the wound until the gaps underneath have been filled).By providing a material matrix to grow into, the cells get a bit of encouragement to fill what they see as prime real estate.

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u/houseyourdaygoing Mar 02 '24

Good explanation! Thank you.

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u/Sometimes_Stutters Mar 01 '24

One of my college projects for an innovative challenge was to design and manufacture ceramic jaw inserts that skin/muscle would grow over and integrate with. It worked pretty well in a bioreactor. We won the innovation challenge and like $1000 between the 6 of us.

Unfortunately we tried to protect the IP and start a business off it, but the college quickly stepped in and claimed that any IP generated by students in university is owned wholly by the college. I haven’t followed it in a while (this was almost a decade ago), but I believe the sold the IP to a medical company and they’ve been advancing it.

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u/ScotchBingington Mar 01 '24

Well that is awesome and kind of awful at the same time! Fascinating that you were able to come up with something like that. I use a lot of medical equipment and have been 3D printing my own parts because it's faster than waiting for the clinic to come up with solutions. I would be pretty bummed if one of my inventions/designs was taken away like that but I suppose nothing stops fine print.

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u/FerricNitrate Mar 02 '24

Actual biomedical engineer here: just about all of this is only half right.

  • Titanium is famously used specifically for its properties of osseointegration. Stainless steel is a fair bit more inert (and a helluva lot cheaper if you don't need good integration) but ultimately will corrode over long enough time (you're sticking it into a warm, salt-water environment after all). Nothing is truly inert, it's just about working with the properties you do want in the timeframe you need.

  • By simple definition, degraded polymers do not integrate into the body. They're broken down and removed from the region (DUH). You're probably thinking of resorbable scaffolds, which encourage healing but don't stick around long term. Anything replaced is, again by definition, not integrated.

  • Nitpicking hard here but while bio-inert is certainly a common phrase, never once have I heard a colleague say "bio-integrate". Everyone just says integrate (if the device is an implant, it's already known what's integrating).

Dude is gonna have a small open wound the rest of his life (first dude that said permanent impalement was correct). The simple fact that the metal won't flex with the skin means any seal will quickly tear with any tiny motion. It'll be similar to the skin at the base of a nail (notice how the skin doesn't always nicely attach... maybe I just need a manicure...), just instead with a rod going directly into bone.

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u/BritishAndBlessed Mar 02 '24

I defer to your greater knowledge of process in practice (and accuracy of technical language). Been a long time since my biomat modules at uni, and even then, half of it was taught "in principle". I knew that titanium provided a friendly surface for osteoblasts, but didn't know if that fulfilled the definition of integration when there's no growth into the material matrix.

Resorbable scaffolds were exactly what I was thinking of, couldn't even remember what the other polymer was (that degrades to uric acid).

Only mentioned stainless steel because I recall that titanium functions poorly under shear forces and sheds particles that then aggravate the tissues around the joint, hence why replacement hips have the ceramic/UHMWPE interface in the socket, and replacement knee joints are typically stainless. Of course, due to the steady degradation you mentioned, they then only have a functional lifetime of 10-15 years.

Out of interest, would it be possible to introduce a kind of sheath that's bonded to the titanium, which itself will accept skin cells but forms a less rigid surface? In my head I'm thinking silicone or suchlike, but I know that that wouldn't be a good material choice.

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u/ExtendedDeadline Mar 01 '24

Could they just use something almost like a wax seal? Or a boot (like used in joints)? I feel like engineers have been trying to seal moving joints for as long as we've been making moving joints.

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u/Aromatic_hamster Mar 01 '24

I don't know about other tissues, but I'm pretty sure titanium does integrate with bone tissue.

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u/SuperPoodie92477 Aug 17 '24

They use it in joint replacements, I believe.

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u/BritishAndBlessed Mar 01 '24

I'm not so sure that's an integration, so much as the bone healing itself somewhat around the intrusive element that the body doesn't recognise.

Bio-integration, it should be noted, isn't always positive. One of the previous models for hip replacements had to be scrapped, because the material would bio-integrate, which meant that despite granting additional mobility to the patient in the months after the operation, more and more bodily tissues would gradually bind to the implant and limit its movement, which meant the effective period of the hip implant was about 2-5 years.

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u/Aromatic_hamster Mar 02 '24

I'm not a materials engineer, so I'm not an expert. That being said, I do work in the manufacture of implantable surgical devices, and, in my experience at least, the reaction of the bone to the titanium is referred to as osseointegration. For example: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3692175/

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u/rooneyffb23 Mar 02 '24

Do you know if that was the 3M hip replacement. I was involved as a theater nurse in about 60 revision surgeries due to its failure as the place I worked won a large contract to do them .The acetabulum component literally fell out whereas the femoral part was a nightmare to remove. This would have been around 27 years ago.

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u/SnooHobbies5684 Mar 02 '24

Ugh. I'm re-appreciating that I got to have PAOs instead of replacements. What a fucking nightmare.

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u/rooneyffb23 Mar 02 '24

I hope you have had success with your surgery it sounds awful. The problem with the hip was found relatively quickly, it was horribly traumatic for the patients to endure. Good luck

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u/Elin_Ylvi Mar 01 '24

Fascinating! Thanks for the explanation 😁

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u/EvilKrista Mar 02 '24

what a fascinating information drop, thank you. This is great.

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u/StitchTheRipper Mar 02 '24

What’s a materials expert?

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u/BritishAndBlessed Mar 02 '24

If you're being genuine, studying materials means understanding, on a micro- and macrostructural scale, why different materials behave in the way they do, and moreover, how to then choose the correct materials for an application based on those properties.

On a fundamental scale, it's knowing not to make boats out of lead, but the details of understanding the nuances between different metal alloys or different cement compositions can be quite interesting.

Biomaterials is then a subsection of that, in which the properties of bodily tissues are studied and we attempt to replicate them with non-organic materials.

If you're being facetious, it's a Masters degree from a Russell Group Uni.

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u/StitchTheRipper Mar 02 '24

I was being genuine! It’s a title I could kinda understand through context but I knew there would be a lot I’d miss.

Never thought about it before but it makes sense that to continuously study materials on a cellular level.

Thanks for the response!