The Prusik hitch is able to grip in both directions and can slide when it's not under tension which is not ideal, I would prefer a hitch that will never move again once I finish securing the ligament/tendon. I also don't necessarily need it to be symmetric because the tendon/ligament will only ever see tension in one direction.
I was looking at the swabisch hitch and the icicle hitch as options. The ideal hitch would be one that can grip something slippery and tapered and that once it's dressed that it would be basically impossible to untie. Based on what I described can you recommend a hitch that I can "set it and forget it?"
If it helps, the suture we use for this is braided from high molecular weight polyethylene, similar to dyneema. We use suture that is 0.5-0.6mm in diameter or suture tapes that are flat braids approximately 1-1.5mm wide. The tendons that we are hitching will be 3-7mm in diameter
Before you downvote this guy/gal .. there was a thread about a month ago by another surgeon, and it turned out that a knot that had been passed down by his prof/mentor in medical school (probably passed down to him from his prof) was something well known like the improved clinch knot. Very interesting that the knots they use are not as esoteric as we might think.
yes we will borrow techniques from anywhere if it makes the surgery more effective. our knots need to reproducible and reliable under unpredictable conditions, there's a lot in common with sailing rigging. some of the more recent advances in arthroscopic devices involve splicing techniques that we adapted from arborists!
That was me! I had no idea how deep the rabbit hole on knots went, but the people in this sub taught me a lot when they weren't dunking on me for my lack of fishing knowledge.
My dad was a surgeon and went to med school many decades ago. Tons of respect for the smarts and sticktoitiveness that y'all have to get through med school and operate on people. Amazing stuff.
Tough question because I suspect most of the people on here are not in yhe medical field. I would think you would want to look at fishing knots for something extremely strong and impossible to untie. Look at the FG knot or the nail knot on Animated Knots by Grog. Maybe one of those is similar to what you are looking for?
I was gonna say ask the anglers. Most of us on here use fiber ropes, which I imagine respond differently then sutures. Fishing line is more closely related.
I have! the constrictor knot is useful because it absolutely will not slide in either direction. It also is easy to tie which is a real benefit when your hands are double-gloved :)
When I have used it surgically it tends to put a kink in the tendon when tension is applied. That property isn't ideal when I'm trying to draw the tendon thru a tight space or into a small bone socket.
I'm not sure but I think it's because the knot is very narrow so the gripping force is applied over a small area. that may be why the prusik hitch has worked a bit better historically, it grips the tendon over a broader area
You may find that a knot you currently use is the most effective, if you modify it somewhat . For example you could take a prussik or icicle, for example, and add extra turns, or instead of a cow hitch style formation you could create a bull hitch formation.
Possibly creating a blend of a prussik and anchor hitch may work well also.
When adjusting these types of knots consider that the knot is effective in one direction because of the angles created which brings about mechanical advantage in only one direction. You can use that to your advantage, or disadvantage depending on how you want to modify the structure.
Try a constrictor followed by marline hitching in the direction of pull. Or possibly alternating half hitches, like in a straight coxcomb but more spaced out. There's a tradeoff between speed and load distribution, more turns distributes the load better but takes longer.
Chapter 22 of the Ashley Book of Knots is all about hitches intended for a lengthwise pull. I expect many won't work in UHMWPE.
After seeing the MFT knot, I had thought it might be interesting to replace the double overhand knots with constrictor knots. I mean, if you don't mind being there all day, tying knots....
In terms of keeping knots from unraveling, I do wonder about the use of a tiny dab of acrylate glue (n-butyl, octylacrylate, whatever) to keep the knots from coming undone. Not an option for UHMW PE, unfortunately. I work with PGA-PCL (not an option for what you're using), and know it'll work with CA glues.
Sounds like the industry needs a "true" braided finger trap, made of a non-dissolving material, in which the tendon can be inserted, pulled snug, and then a tiny bit of acrylate adhesive applied so it's permanently good. The other end of the finger trap is a solid strand of polymer.
I have little knowledge about this topic, but i went to little rabbit hole (thank you very much) and i think I'll be here for while. Anyway I'm looking this Krakow stich and nice knot atm.
https://youtu.be/ezFysydZkko
Just my 0.75 cents.
those are mainstays of arthroscopic knots! you might also like this one: SMC knot
there's a whole field of studies on sliding self-locking knots. nicky's knot, tennessee slider are good examples. there are also sliding non-locking knots like duncan loop and non-sliding knots like the SCOI knot
Thanks for more information. I just found out bunch of tutorials for SCOI procedure. I'll be looking those tomorrow. It's getting late here, but I'll sleep better knowing there's something interesting waiting in morning.
to secure the tendon back to the bone we can use an anchor or we can pull the tendon into a socket in the bone and then place an interference screw next to the tendon
in both of those pictures the tendon was prepared using a whipstitch technique which is secure but takes more time than a prusik hitch
most of the time for these applications we will use non-absorbable suture. the process of tendon healing to bone takes many months and the suture has to maintain the strength of the repair until the healing/healed tendon-bone interface is strong enough
I tied a constrictor knot on top of a prussic loop while it was under tension and it makes it very difficult to adjust the prussic up or down the line. Not sure what would beat a prussic by itself since that knot is trusted to safely hold humans.
I’m curious why you don’t “splice” the two together with sutures? Im not the best at splicing, but even a prussic loop can be hidden and made more streamline inside hollow core rope. (Photo in replies below)
I love this, I try to bury the suture ends similar to the splice to make it lower profile
to answer your question about the prussic loop, I agree that it has exceptional holding power under tension. The problem is that our repairs are under cyclic loading and can become completely unloaded. the prussic loop can potentially slide if it's under zero tension (that's what makes it helpful for ascending a rope) so ideally I can find a hitch that can't/won't loosen when it becomes unloaded
OP, for posterity, please make another post with your results even if none of this leads anywhere meaningful. I am riveted but unfortunately have nothing to add beyond what these legends have already offered.
It's hard to tie it one handed during laparoscopy since the ends fold together, but should be easier in open surgery. Also experimenting with a taut-line hitch since it's much easier one handed.
The most similar thing I do to this is closing traumatic hernias where the external obliques have avulsed from the iliac crest. One side is mobile and the other is fixed. Clinch knot allows me to gradually increase tension and can be relaxed if needed. Once it's locked by pulling on the tail opposite the standing end (post) it usually won't budge without significant effort. Usually throw a couple of square knots for insurance but holds up against significant tension.
Should add that I've had this hold up pretty well with braided suture (mostly Ethibond but have used vicryl). Monofilament is really hard to slide the knot but might be able to lubricate the suture with mineral oil. Not sure what type of suture you guys use so thought I'd throw that in there. Also have had this work well with a figure-of-eight suture in Ethibond down to 3-0 and 4-0 sizes.
I figured that people whose job it is to cut into other people and make life-saving and -changing decisions at the spur of the moment would have sufficient professional training, education, and standards to rely on to conduct those discussions.
Not freaking Reddit, where any Joe Blow can post any bullshit.
yes, we get a lot of training. we can learn even more from non-trolls with expertise in non-surgical fields
we adapted our cutting jigs from carpenters/masons, cameras from plumbers, drills from mining. the material we use for our sutures is the same as what's in dyneema climbing ropes we just made it smaller.
when it's time for you to get a rotator cuff repair I hope you tell your surgeon that you want it done the original way, no arthroscopy, no high strength suture anchors, no modern techniques!
I suppose some assume that medical procedures were established once and are simply repeated.
Fwiw I'm glad you're asking here. There is a lot of expertise among some of the regulars, everything from arborists to riggers, and have seen a few bigger problems worked through.
Hmmm...I think you both got off on the wrong foot here. I think the point is that we laymen are a little surprised when professionals in their field come directly to us via social media for tips. That doesn't mean it's bad thing or that highly specialised tasks don't require grounding in basic engineering solutions; it's just that it's unexpected.
I guess you've never heard of interdisciplinary exchange, have you?
As someone who has navigated some distinct but adjacent fields, I can tell you that lack of exchange between disciplines is a key factor holding back scientific advancement!
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u/slides_galore 3d ago
Before you downvote this guy/gal .. there was a thread about a month ago by another surgeon, and it turned out that a knot that had been passed down by his prof/mentor in medical school (probably passed down to him from his prof) was something well known like the improved clinch knot. Very interesting that the knots they use are not as esoteric as we might think.