Surgical Knots Questions - Slip vs square knot?

[Decimus]

Ok, I am exposing my utter lack of knowledge in surgery…but here it goes:


First, my understanding of these knots is:

· Square-knot: Alternating throws laid flat

· Slip-knot: Two consecutive throws slipped down, followed by a third opposite direction throw laid flat


My questions: In surgery, then do you use a slip-knot vs. square-knot?


I guess I just don’t understand the advantage of one over the other…

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[Kahreek]

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[Decimus]

Thanks! But, I'm still wondering if you can give me specific examples of when a surgeon would use one vs. another?

Are slip-knots really used for monofilament?
Is this purely preference?

I guess the real question I'm trying to ask is: When a surgeon asks me (a student) to tie something, should I be going through some sort of algorithm in my head to decide what knot to use...or just use what I'm more comfortable with...

 

[SouthSideSteve]

I always do a slip. With silks I do 2 throws in the same direction then lock it on the third throw.

When tying down aortic purse strings, I usually do 3-4 throws in one direction then alternate the next 4.

 

[thyroidectomy]

Slip knot- will tighten your knot without locking (i.e. helps to avoid air knots).
Square knot- will lock your knot (i.e. theoretically secures your knot) (i.e. if you have an air knot it will now stay an air knot no matter what you do).

The first throw of any knot is often an air knot (to varying degrees) by the time you throw your second knot. Therefore, it's helpful to throw the 2nd knot in the same direction (slip knot) to tighten the knot. After 2 throws, the knot will typically stay tight without spontaneously becoming an air knot. You can then safely throw a square knot in order to lock the knot in a tightened (non air knot) position.

That principle can be used with any suture type. Suture type, however, dictates how many times you need to square off a knot. For example, a monofilament is more likely to "slip," so, after locking on the 3rd throw, you should continuing squaring for another 4 knots or so.

 

[SLUser11]

I guess the real question I'm trying to ask is: When a surgeon asks me (a student) to tie something, should I be going through some sort of algorithm in my head to decide what knot to use...or just use what I'm more comfortable with...

Don't do any calculations. Just tie a square knot. Trust me. Great stuff from the other posters, but just tie a square knot.

 

[dienekes88]

Oddly enough, if you do a one-handed tie and keep a really good post, then it will usually slip even if you alternate the directions. Most of whether it lays square is in how you lay the knot down and the management of suture tension in the two free ends.

If I were you, I'd start with a two handed tie, square knot.

As you progress, you will notice that sometimes the kind of knot you tie will end up being dictated by the anatomy. Some knots are just better tied one-handed left-handed, and others are better tied one-handed right-handed.

 

[mimelim]

From a student perspective I will echo @SLUser11 ...

#1 Learn how to tie a good two handed square knot.
#2 Learn how to tie a good slip knot and pay attention to why it may be adventageous
#3 When in doubt, ask. Or simply say, "I'm going to tie a square knot and do 3 throws." with inflection indicating that you are asking someone to check you.
#4 If nobody is around, or there is any question, default to tying a square knot.

 

[JayDoc06]

From a strength standpoint, a slip knot or even a series of them is weaker. Think about it- one string wrapped around the other stationary strand a bunch of times puts much stress on the straight string increasing the chance of failure. Btw a bunch of slip knots or "half-hitches", for the scouts in the room, looks good but is weak. Tie square knots. When practicing, look at the knot, if it ugly it is correct (assuming no air knots of course), if it is pretty then it is a bunch of slip knots. Also- not needing a slip knot probably means your tissues are lying nice and loose together and not under tension...

 

[filter07]

The only times I found a square knot necessary is when tying a short stump that will bleed or cause a tie to slip off, or when tying under some tension. In these cases I place a two handed square knot and maintain tension. In every other instance I prefer the two slip knots in the same direction to cinch down a knot.

People are taught different things that don't make sense. Like tying square knots while maintaining a post. Making a knot that doesn't loosen as you maintain a post. I wish there were some master techniques videos rather than intern level tie techniques online. I think most people find something that works as PGY-1 or 2 and don't make much progress in technique afterwards. We should have coaches like athletes to refine our techniques