The CONSTRICTOR KNOT for Surgeons | The best ligature | Instrument tie tutorial | Dr Amanyu

The constrictor knot is one of the best knots for ligation (more secure than even the surgeon's/squre knot, RHAP, and suchlike). In this video I've demonstrated the quickest and most efficient way of tying it in surgery.
It readily tightens, meaning, it locks as soon as you tie it down (since it has 2 components - a "riding-turn" which locks on top of a "half-knot", both of which cinch down together in one go). So, unlike the surgeron's/square knot, it doesn't really need locking throws (though you can throw a couple of half-knots on top of it for added security). If you try to loosen (effectively increasing the length of) the half-knot part, it will directly cause a tightening (decrease in length) of the riding turn on the top, hence tightening it even more. So the beauty of this knot is that, any force trying to loosen this knot from within (say a pulsating artery) will only tighten it further, making it virtually impossible to pull this knot apart.
It may not be the ideal knot for every scenario, but wherever you can "clamp→(cut)→ligate", you can use technique. Comes in handy a lot especially if you don't have someone assisting, to hold the forceps for you.
It's one of the hardest knots to untie. Doesn't slide. Doesn't capsize. Fits snugly to the circumference of the vessel/duct. And given how quick and easy this knot is to tie inspite of being one of the most secure, I think we need to be teaching and employing this knot more.
Wishing you a wonderful day! :)

Some studies that evaluate the knot security/failure of the constrictor knot -
https://www.ncbi.nlm.nih.gov/pmc/arti....
https://avmajournals.avma.org/view/jo...

Here are some other ways of tying the constrictor knot (from animatedknots.com) -
https://www.animatedknots.com/constri...
https://www.animatedknots.com/constri...
https://www.animatedknots.com/constri...
https://www.animatedknots.com/constri...