Which bioproof is best for you?

There’s a lot of discussion on here about the various kinds of bioproofing, but it tends to be focussed on whatever implant is being discussed at the time.

Which made me wonder – does a table exist listing the various bioproofing materials, which applications they’re suitable for, strengths, weaknesses, lifespan, known issues, etc? Seems like it’d really help anyone pondering a new type of implant pick the best one for them.

What do you think?



  • There's no table per se. There is a huge list but even that has wiggle room and in this community in particular, people like to pick and choose based on financial situation and technology available. 

    The reason that each conversation focuses on the implant at each time is that the considerations for each implant (would be if it was beyond magnets) are locationally and biological system specific.

    There are a lot of things to consider in biological systems. Custom building from the current list available is usually the way to go.

    I would hazard to get a list up here, but then I would be concerned about people mix and matching as they felt acceptable as opposed to using the proper coating for the proper thing (re:dental resin for implants...)

    Do we want a list? Is that a thing?
  • From what I have read sugru will work for most locations but it would probably wear down in high friction areas (like up close and personal with joints) or anywhere particularly hostile like your digestive track.
  • Sugru isn't any good. SFM tested it alongside TiN, Parylene, and some other materials and it broke up so easily that it couldn't so much as be tested by some methods. It also showed tons of fouling.
  • Oh my! Do you know if he kept a paper or something on his test? It sounds incredibly useful.
  • Heh, SfM is me and @Cassox. I can dig up the results. However, I think the paperwork will be slim. Basicallly, the sugru was so crappy for a bioprooof coating, there is not really an official metric to describe how bad it is. Things that bad aren't even considered to be put in bodies except by grinders....
  • I used polyolefin/nylon shrink tubing over a cylindrical magnet and have had no issues.  I can't really speak on how it holds up in the long run as it has only been a bit over a month.
  • DocM, hey what types of fixatives do you use? A pet project here... I've been looking into chemical sterilants which are often also fixtures. Glutaraldhyde in particular has caught my eye. Is this something used in your proffession?
  • It’s definitely a good point that discussing things from the end product view gives the most context and focus. In the end, you’ll get a really solid, well researched manual for “How to do X”.

    But I’m wondering about approaching from the other side – innovating new products. If you were to build an ingredients/tools list, that essentially said “here’s all the stuff we have, and its strengths and limitations”, you can kindle that engineering mindset and get people thinking “ok, so I can’t use X with Y, but what if I used Z?”

    Is that a sensible idea? Or would it be a fool's errand?
  • I totally agree Frank. TiN is great for a number of purposes... but then again, so is Parylene. We've tested a lot of materials and can give a limited version of what you're talking about. Even silicone really does have some advantages in certain situations although it's a poor choice for magnets.
  • @Cassox - Yes, we use glutaraldhyde but mostly just to clean equipment and in specialized embalming fluids to keep jaundice cases from going green during embalming (it isn't totally successful).
  • Can you explain to me the safety procedures and such used? It's one of the few approved chemical sterilant that don't totally destroy most coatings... it's also rather nasty and toxic though.
  • Unfortunately, because the people we're working with are already deceased there really aren't safety procedures for the patient.  

    As for me, I'm gloved up and... well not much else.  Most embalmers (in my experience, and myself included) are primarily concerned with biohazards and direct chemical exposure.  If we inhale a ton of aldehydes over the course of a month, a year, a career... oh well, that's just the job.  

    Our employers provide respirators and such, but the only time I've used one was because of a large accidental spill of high index fluid when the ventilation wasn't on.  Without the respirator you couldn't have forced me to go in there to turn the fans on.

    Glutaraldhyde won't just outgas super quick like formaldehyde, so you're going to want to wash the implant several times in an appropriate solvent.  It is miscible in water, so you should be able to bring the concentration down quickly.

    Is there anything more specific I might be able to address?
  • When purchased, do you get a pre-mixed version? Or do you dilute it yourself? For sterilization, the immersion time is rather long. 8 hours or so.. I'm wondering if we could soak, pull it out of a container using sterile forceps, then drop it into a container of sterile saline. Shake the bottle for a while, then take it out with sterile forceps and do a final saline rinse with a syringe. I'm worried though about how much if any residue would remain. Also, I've read about people being effected by the fumes alone from an open bottle. While fume hoods are not an issue here... people using this as an at home procedure... any thoughts?
  • Hey doc, your shrink tubing thing caught my eye. how'd you seal the end of that and heat the whole thing without damaging the magnets?
  • @Cassox
    The fumes can be irritating, but even without ventilation on I've never been bothered much working around them (formaldehyde is far worse).  We get a premixed solution that also contains methanol and god knows what else.  There's a tray with a lid that I keep the trocar in full of the stuff, and another for soaking non-sharps (hemostats, forceps, etc.).

    I'd do more than a single rinse although two or three should be fine.  Also, if you're going to all the trouble why not use formalin?  You can get it with or without methanol (the stuff without ends up with a thin layer of paraformaldehyde in the bottom if you let it sit long enough) and your soak time is considerably reduced.  Formaldehyde is typically a gas at room temp, so after rinsing if you let it sit for a spell it should completely outgas.

    Either way, ventilation is a good idea.  Even with g-aldehyde I wouldn't want to leave it in an enclosed space for any amount of time.

    Heating wasn't difficult.  I hit it quickly with a hair dryer, stopped and let it cool a bit, hit it again, etc. until it was nice and tight.  In retrospect, I probably could have just kept the hairdryer on it since the tubing didn't have far to go and I only hit it with the heat three times, but I guess I was being cautious.

    The ends concerned me a bit, but I don't think I damaged the magnet much.  They had already shrunk to a diameter smaller than the magnet.  I have a small pair of flat faced pliers I heated over an alcohol lamp and pinched the ends shut as close to the magnet as I could with them.  After that, I trimmed them down as much as I was comfortable with using a scalpel and a pair of cuticle scissors.  I also rounded off the corners thinking the points might damage tissue a bit, but I'm not sure how necessary that was either.

    In the end, there is a small amount of material on either end that makes the implant longer than just the magnet, and it is a much thicker coating than a lot of the things discussed here.  I wanted to see if I could come up with something I already had on hand and that would be easy, and this is the result.  I am getting sensation from it, but without another implant to compare it is hard to tell how much.
  • oh ok that's exactly how i figured you'd do it. and it's holding well? crazy that soemthing so simple is bioproof
  • edited December 2014
    It hasn't been very long... a month or so.  So far, so good.  My only regret is not getting the cylinder farther back along the side of the finger.  As it is, it is up toward the pad enough that it gets some mechanical stress from certain activities.  Live and learn, I guess.

    Talk to me in a year, and we'll see how bioproof it turns out to be.
  • edited December 2014
    well since you've had such good luck I was thinking of giving it a shot myself. Also what size did you use for magnets? the usual 3x1? or longer?

  • It is 4mm long.  I want to say 4x1, but it feels wider than that when I roll another finger over it.  Might just be the coating making it feel that way.

    The one nice thing about the extra bits on the ends is that it makes it really easy to place a deep stitch against the little "tab" to hold it in place while it heals a bit.
  • I'll be attempting with 3x1 magnets. Im very interested in this and want to see if commercial tubing and magnets can compared to the nice TiN ones i'll eventually also be implanting. 
  • @drjaaz
    I've been thinking about it tonight and I'm going to go ahead and prep and implant another one of these in a different finger.  If all goes well, I'll be removing the first one since the placement is pretty annoying at times (specifically while hunting with a pump action).  Hopefully the new location will alleviate this.

    I'm not sure when I'll have a chance with the holidays and all, but I'll get some step-by-step pics this time of the magnet prep for you.
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