It is the second time I learn something about arthroscopic knots - the first was at the thread about the Dines knot :
http://igkt.net/sm/index.php?topic=3659 I had thought of this : What will happen if we use arthroscopic knots that can be capsized easily when tied on the common material we use, as slide-and-grip adjustable hitches ?
We usually consider that the capsizing of a knot is a bad thing that should be avoided - with the possible exception of the Carrick bend. However, any capsizing changes the path of the lines that penetrates the knot s nub in an unpredictable way, but in a way that we can exploit nevertheless. If the capsizing knot swallows a straight line that goes through it, and chews it in a curvilinear form, the curved segment of this form, acting like a collar ( and a collar that is also nipped along its path inside the knot s nub by the surrounding shrinking volume of the knot ), can resist any further pulling. The knot will "lock", and the adjustable hitch would be transformed into a fixed one.
I have examined all the arthroscopic knots that are in current medical use. I have seen that only a fraction of them can capsize easily when tied on ropes, and only three of them capsize in a compact and tight form, that remains compact and tight even when they remain unloaded. They are the Dines knot, the Weston knot, and the Tennessee slider.
I have seen that the capsized form of the Weston knot is a better knot, as a fixed loop knot, than the capsized Dines knot. Also, the Weston knot has two lines of defence : When the first capsized form would itself be capsized, under extreme loading, there emerges a second capsized knot, as a second line of defence against slippage, that is also stable. Basedupon this we can argue that the capsized Weston knot is safer than the capsized Dines knot, when they are used as hitches.
We can also tie the "Inversed Weston knot", the final capsized form of the Weston knot, where the straight and the convoluted live ends had changed roles. It is also a great advantage of this triply-capsized Weston knot the fact that even this form it can be locked by a pulling of the now straighten end - a third line of defence !!!
I have also seen a disadvantage of the capsized Dines knot : the second leg of the formed collar is not nipped hard enough, so the whole collar remains loose, and we need to pull its other end to tighten the knot in a compact form. In the Weston knot, the pulling of the one end is enough to entangle the other, straight line leg, and tighten the knot completely at the same time.
Last, but not least, I have examined the Tennessee slider. I was delighted by its symmetry - in the sense that there is an initialof this knot form from which one can pull the one or the other leg -whatever he chooses at that moment - and the knot locks both of them at the same time. Which is this form ? The ABoK#1060 forgotten loop knot, used as a hitch. The reader should tie the most symmetric ABoK#1060 as a hitch around a pole, and then pull the one or the other leg, to capsize the knot, and see what happens ! The locked knot can be secured even further with the use of half hitches, as it is the common practice with all arthroscopic sliding knots.
( See the attached pictures for the Weston and the Dines knots, and their capsized forms ).
P.S.
The so-called " Dundee knot", is but the quick tying method of the "Eskimo" bowline - so I am not going to say anything more about it here.
Another knot that has similar characteristics, is the Pretzel knot :
See : " The Pretzel knot: a new simple locking slip-knot "
http://link.springer.com/article/10.1007%2Fs00167-009-0984-9?LI=true#page-1http://rd.springer.com/article/10.1007/s00167-011-1788-2/fulltext.htmlA fine article on surgical knots :
Locking, Jamming, and Ratchet Mechanisms of Sliding Surgical Knots Topologically Revisited
Journal of the American College of Surgeons
Volume 205, Issue 5 , Pages 717-723, November 2007
http://link.springer.com/article/10.1007/s00268-008-9904-2/fulltext.html
