Author Topic: Capsized arthroscopic knots as adjustable hitches.  (Read 11422 times)

X1

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Capsized arthroscopic knots as adjustable hitches.
« on: October 30, 2012, 10:39:01 PM »
  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-1
http://rd.springer.com/article/10.1007/s00167-011-1788-2/fulltext.html

A 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
« Last Edit: November 03, 2012, 01:17:47 PM by X1 »

X1

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Capsized arthroscopic knots as adjustable hitches (II)
« Reply #1 on: October 30, 2012, 10:41:43 PM »
   Pictures of the capsized Weston knot and the tighten Inversed Weston knot,

X1

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Re: Capsized arthroscopic knots as adjustable hitches.
« Reply #2 on: November 03, 2012, 01:47:28 AM »
   The Tennessee slider, and its capsized form, the ABoK#1060. Although in this form the straight leg is not deformed as much as in the other locking sliding knots, the tightened knot is symmetric, and this might be usefull in some applications.
   The Dines knot, the Tennessee slider and the Pretzel knot are very simple and very similar, in their initial form and in their capsizing /  locking mechanism as well. Their strength and security is measured and evaluated by the orthopedic surgeons, but we are mainly interested in their capsized form, not in their gripping power before they capsize - and I am not aware of any article on this.
« Last Edit: November 03, 2012, 10:23:26 AM by X1 »

X1

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Re: Capsized arthroscopic knots as adjustable hitches.
« Reply #3 on: November 03, 2012, 02:01:50 AM »
   The Pretzel knot. (1)-(2) Although I had tied this knot hundreds of times ( because of the series of bowlines based on the Pretzel nipping loop), it had never crossed my mind to see what happens when it capsizes... because we were used to believe that capsized knots are knots that have failed to function as they were disigned to do. Here the knots are supposed to capsize, and capsize easily, because this deforms the straight leg of the bight that penetrates them, bends it, and enable the shrinking knot to lock around it.

1. http://link.springer.com/article/10.1007%2Fs00167-009-0984-9?LI=true#page-1
2. http://rd.springer.com/article/10.1007/s00167-011-1788-2
« Last Edit: November 03, 2012, 02:03:23 AM by X1 »

X1

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Re: Capsized arthroscopic knots as adjustable hitches.
« Reply #4 on: November 03, 2012, 06:02:57 PM »
  More pictures of the capsized Weston knot.
  Although the loop knot by itself is not a knot we would choose for an end-of-line loop ( a crossing knot bowline-like loop knot, where the continuation of the eye-leg-of-the-bight is not tangled within the rest of the knot as effectively as it could),  the way it is tied makes it very interesting. The knot at the attached pictures is tied on a 12.5 mm / 1/2 inch nylon kernmantle rope, and was loaded with alternating loading up to 250 kg, yet it did not show the slightest sign of capsizing even further. As I had explained in the first post, even if it had capsized, it would had locked when it it would had reached its second line of defence - which is also a stable, secure knot.
   One may ask : Why use this knot, and not the standard or the "Eskimo" bowline, tied with the quick tying methods ( ABoK#1014)(ABoK#1987-1988-1989) ? After all, those knots are tried for centuries and they are proved to be secure knots, while the capsized Weston knot is not.
   The answer is that the Weston knot will grip the straight leg even if it will not capsize, for whatever reason : too much friction or stiffness of the rope, insufficient pull of the straight leg, interference with other objects at the vicinity of the knot, etc. On the contrary, the knot bases used for the quick tying methods of the standard and the "Eskimo" bowlines can not grip the stright leg at all, without first being capsized. That is the advantage of the arthroscopic knots examined in this thread : they can used as adjustable gripping hitches / nooses, and/or as fixed 1-wrap hitches / end-of-line loops.
 
« Last Edit: July 16, 2013, 06:43:27 PM by X1 »

X1

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Re: Capsized arthroscopic knots as adjustable hitches.
« Reply #5 on: December 08, 2012, 09:28:48 PM »
   I had not been able to find a (free  :) ) copy of the original paper, where Weston presented the Weston knot - till today...
 
Obstet Gynecol. 1991 Jul;78(1):144-7.
A new clinch knot.
Weston PV.
Department of Obstetrics and Gynecology, Southwest Texas Methodist Hospital, San Antonio.
 
www.iuga2012.com/program/syllabus/syllabus24_knot.pdf   

   The moment I downloaded the paper and looked at the images, I realized that I had seen this knot... in the ABoK !
   It is funny that I had tied the knot many times, I had taken pictures of it, I had even tried to figure out a method to memorize its tying procedure ( no luck...), but I had to see the sequence of movements presented by Weston himself to understand the should-have-been obvious fact : the Weston knot and the ABoK#1991  "Jam Hitch" are identical. So much about the ability of human mind to remember knots...
   Now, nobody had told me this - which suggests one or two things :
   First, that nobody reads what I write, or, even if he reads it, he does not pay any attention to it ( not very good, for me...)
   Second, that the people who had read this thread do not remember what they have read in the bible ( it happens...), or they have not read the bible ( it should not happen...), or they do not wish to help a "fellow" knot-tyer correct a mistake or omission of his ( I know that it should had not happened, but I also know that it happens...)( very bad, for everybody...) 
   However, it turns out that everything has two ends, the bitter end, and the sweeter one... :) I wonder how many " knot enthusiasts ", in the last quarter of a century, had noticed that the Weston knot, presented at 1991, is the same as the ABoK#1991 knot, presented three quarters of a century ago... :)

   

xarax

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Re: Capsized arthroscopic knots as adjustable hitches.
« Reply #6 on: June 07, 2014, 01:43:30 PM »
   The "left-handed" capsized Pretzel knot is a very secure simple eye-not, too. It looks like a wrongly tied "Eskimo" bowline, but it seems it is well-balanced and stable. Although the Tail End is not immobilized/locked by the Standing Part s first curve ( it is not in a direct contact with it, as it happens in the "right-handed" version, shown in Reply#3), the fact that the returning eye-leg is following this L-shaped path as it enters into the nipping loop ( and this is why it resembles the "Eskimo" bowlines more than the "right-handed" version ), is a very good first line of defence against slippage : we have seen this efficient "handle" in many fixed and adjustable eye-knots. and it is always beneficial regarding security.
   So, when somebody, in the distant future, will test the four "Eskimo" bowlines, it would be great if he will test those two "Pretzel" collapsible knots, too - and It would be even greater if he e-mails his results in the real Greenland, where I will be at that time... :)

P.S. A recent article ( Nov 2013 ) on the original ( right-handed ) "Pretzel knot" - with numbers:) :
http://bvsalud.org/portal/resource/en/mdl-22139407
« Last Edit: November 01, 2014, 06:30:11 PM by xarax »
This is not a knot.

Luca

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Re: Capsized arthroscopic knots as adjustable hitches.
« Reply #7 on: June 07, 2014, 11:32:16 PM »
Hi xarax(I take the occasion to thank you for your replies),

The "left-handed" capsized Pretzel knot is a very secure simple eye-not, too. It looks like a wrongly tied "Eskimo" bowline, but it seems it is well-balanced and stable.

My experience is that,just loading it lightly,is sufficient to end up with a "pretzel shaped" Cow hitch around the standing part: although here there is a loop, and then the first leg of the loop bears 50% of the load, and the load in this configuration is  "crossed"with respect to how  are normally loaded the ends of one of the two links of a Reef knot to do so to obtain a Cow hitch around a straight line,loading this loop is easy to get a similar result, although it seems that one can have a pretty founded hope that nothing happens of "catastrophic" ...

                                                                                                                    Bye!

xarax

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Re: Capsized arthroscopic knots as adjustable hitches.
« Reply #8 on: June 08, 2014, 12:51:27 AM »
   The second picture is of an already heavy-loaded, very tightly locked knot ! Moreover, after this stage, I had loaded the shown knot even more, to the limits of this rope s strength : it became even more compact, many segments were flattened a lot, but its overall shape had not changed further. So, I concluded that this was the "final" form, if one starts pulling the Standing End of an already tightly woven "Pretzel" loose knot. With another, more slippery rope, and if the shrinking of the initial "Pretzel" starts from a more loose state, the knot can capsize even more, as you describe. However, those subsequent forms do not seem to me as stable and well-balanced as the ones shown... I do not think that it is a matter of "loading it slightly" [more] than I had loaded it, as you say. Simply, which is the "final" form depends much on the initial one - and this may be regarded as a disadvantage, indeed. Notice that I had not suggested that any of those two "Pretzel knots" could "replace" any of the four "Eskimo" bowlines, in any way ! I was just impressed by their unexpected stability, because, if I had not tried them, I would had thought that, as they resemble wrongly tied, odd-looking "Eskimo" bowlines, they should be very unstable...     
This is not a knot.

Luca

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Re: Capsized arthroscopic knots as adjustable hitches.
« Reply #9 on: June 08, 2014, 01:39:53 AM »
OK, you have built the loop as configured in your first photo, obtaining the result shown in your second picture loading it. In fact I have acted differently, not fully understanding your experiment.I have capsized the loop in the first photo manually, in order to obtain the configuration shown in your second photo (but obviously much more loose), and only after this manual operation I loaded it:this leads to a different result;acting like you,did I see that I get a result similar to yours...
« Last Edit: June 08, 2014, 01:53:34 AM by Luca »

Urfin

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Re: Capsized arthroscopic knots as adjustable hitches.
« Reply #10 on: August 21, 2015, 09:00:59 PM »
xarax, thank you very much for posting about Weston knot, it seems very interesting.

For those who come to this thread and want to read Weston's paper the new link seems to be http://2012.iuga.org/program/syllabus/syllabus24_knot.pdf

xarax

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Re: Capsized arthroscopic knots as adjustable hitches.
« Reply #11 on: August 21, 2015, 09:24:58 PM »
   A new comparative study :
   In Vitro and In Situ Characterization of Arthroscopic Loop Security and Knot Security of Braided Polyblend Sutures: A Biomechanical Study
   Am J Orthop. 2015;44(4):176-182.
   Lucas C. Armstrong, MD, Alexander Chong, MSAE, MSME, Ryan W. Livermore, MD, Daniel J. Prohaska, MD, Amanda N. Doyon, BS, and Paul H. Wooley, PhD

   http://www.amjorthopedics.com/the-publication/past-issue-single-view/in-vitro-and-in-situ-characterization-of-arthroscopic-loop-security-and-knot-security-of-braided-polyblend-sutures-a-biomechanical-study/70bfd110bc9d681c849669e82edf37ee.html
« Last Edit: August 21, 2015, 09:34:27 PM by xarax »
This is not a knot.