International Guild of Knot Tyers Forum

General => New Knot Investigations => Topic started by: Isleofgough on September 16, 2019, 06:10:18 PM

Title: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 16, 2019, 06:10:18 PM
I wanted to check if this knot has already been described. Adding an extra wrap of the suture around itself at the end of tying a double constrictor increases resistance to slippage about 50%, as measured by a tensiometer. I am thinking about including it in my book on advanced surgical knot tying as a way of securing a drain. A triple constrictor adds little, as the first and third wrap press down on the underlying wrap the same as a double constrictor and the second loop adds little (due to capstan effect). Thanks.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: SS369 on September 16, 2019, 06:37:28 PM
Good day Isleofgough.

The only thought I have on this is the fiddly-ness of drawing it all up tightly. I have no surgery experience and have a hard time imagining using small sutures in the environment it will be used.
Shouldn't a single wrap Constrictor, with your extra wrapped working end suffice?
It could be that doing some wraps before the Constrictor might do a better job of tying off/stemming flow. (?)

SS
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 16, 2019, 07:35:19 PM
SS: you are correct that a single wrap Constrictor is adequate for securing a blood vessel. A slipped Granny followed by square knots is also reliable and easy to tie. I wouldn't recommend a double constrictor for tying a blood vessel with fine suture, for the reason you mentioned.

Drains/tubes/IV lines are a different matter, where slipping longitudinally through the loop can be an issue. Tying down too tightly can also crimp the tube. Drains and tubes tend to be slippery and the suture itself is like fishing line. Multiple wraps don't really help. For example, if one did ten wraps around the tube with the suture, the tension in the middle (between the 5th and 6th wraps) would be very low. One can think of it as a double capstan. The modification of the double constrictor was compared with the standard double constrictor by placing a tensiometer on the two loops at the opposite side of the tube to see how much tension was needed before slippage. It was about 50% more.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: SS369 on September 16, 2019, 07:50:12 PM
Ahh, my misunderstanding of that application.

IMO, the increased resistance to slipping on the tube might be the Knuckle formed at the extra wrap under the overlying turns. In essence, the tube is locally deformed and pushed into that spot, as well as giving the overlying wraps more to constrict.

As far as if this knot has been described, I can't think of or remember (!) it in literature. But I have tied similar tangles, even reeving the working end through the hitch. Ends up looking like a messy Turks head knot.  ;)

ss
Title: Re: Surgeon's modification of Double constrictor knot
Post by: roo on September 16, 2019, 08:25:24 PM
I wanted to check if this knot has already been described. Adding an extra wrap of the suture around itself at the end of tying a double constrictor increases resistance to slippage about 50%, as measured by a tensiometer. I am thinking about including it in my book on advanced surgical knot tying as a way of securing a drain. A triple constrictor adds little, as the first and third wrap press down on the underlying wrap the same as a double constrictor and the second loop adds little (due to capstan effect). Thanks.
What software are you using to create those images?  They are very nice.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 16, 2019, 09:33:43 PM
I use Houdini Indie to do the illustrations, but any 3D program would work. Basically one sweeps a circle along a curve, adds texture and lighting and a camera. I chose Houdini as it is cheaper (free for the Apprentice version) and allows me to create a few points and have the program interpolate between them.

Here is how a regular constrictor would be tied to secure a blood vessel.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Dan_Lehman on September 19, 2019, 01:43:53 AM
I wanted to check if this knot has already been described. Adding an extra wrap of the suture around itself at the end of tying a double constrictor increases resistance to slippage about 50%, as measured by a tensiometer.
How does this tensiometer work, exactly?

Quote
A triple constrictor adds little, as the first and third wrap press down on the underlying wrap the same as a double constrictor and the second loop adds little (due to capstan effect).
The more turns there are,
the more tension must *travel* in order to make
the binding area tight --for the constrictor, that's
360deg roughly, and more wraps will as noted suffer
loss of tension via friction.

How about this : tie a slipped (singly) constrictor
and reeve the unslipped tail through the slip-bight
of the other, then draw the other tight down upon it.
(There is sometimes a tendency for the latter action
of tightening the slip-bight to loosen the base knot,
alas.)

Alternatively, one can follow the mistaken direction some
old knots book authors did in trying to make visual sense
of some cryptic words --misworded/omitted than imagined--
by tying off the tails with a simple "throw"/overhand crossing,
or even *surgeon*-ize that!?

A concern of extra crosses of the ends
is that they perforce are further deviated
from a tangential relation to the tied-to object
(e.g., with perfect tangent point say at 12:00,
they end up pulling away from the surface
more nearly at 10: & 2:00, and some of the
tightening pull goes to pressing *upwards*
into crossing wraps.


--dl*
====
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 19, 2019, 06:04:22 AM
The tensiometer is just a spring  system that measures tension pulled on the two loops at the opposite side from the overhand or surgical throw (6:00 position). One can pull on it until there is slippage and test the difference between a standard double constrictor and the surgeon's modification. I tested it with 2-o monocryl suture, which is similar to fishing line.

It may be that the double constrictor spreads the tension over both wraps a bit better than the single constrictor, avoiding the issue you mention of the wraps being at the 10 and 2:00 positions, rather than 12:00. In any event, for most suture and drains, the wraps will be closer to 11:30 and 12:30 positions, since suture is pretty fine.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Dan_Lehman on September 19, 2019, 10:30:15 PM
Re the tensiometer, I'm just unsure of how well it
really is measuring vulnerability to slippage; there
might be some over-time loosening not seen in a
one-time loading!?

In any case, IMO if one can arrange to further
anchor one end of the constrictor with some
U-tuck (i.e., tucking a tail after making a U-turn),
it should be highly unlikely to gradually slip out,
and I think that with one tail unslipping, the knot
will well enough stem slippage of the other --that
there is generally needed some *sympathetic*
slippage in both ... .

Or one might endeavor to set snug an overhand
stopper knot
against the constrictor --though
I admit to finding this not all so easily done, when
I'm tying whippings with small stuff : one can get
the stopper pretty close, but "snug" takes some
extra & awkward tying.  Closing with one bight-end
to draw down upon the opposite tail seems surest.


--dl*
====
Title: Re: Surgeon's modification of Double constrictor knot
Post by: agent_smith on September 19, 2019, 11:40:27 PM
Thank you for posting your surgical question in this forum Isleofgough.

Some questions if I may:

[ ] What length of time must this hitch remain effective?
That is, for what length of time is the hitch intended to be employed in its role?
Is the hitch intended to be employed only for a brief interval of time?
I'm guessing that any employed hitches/knots aren't intended to be permanent (eg they naturally dissolve over time)?

[ ] Are there any mechanical stresses acting to influence the security of the hitch during the time frame in which it is employed?

[ ] Do you need to achieve the smallest possible 'footprint' with knots/hitches employed in surgical procedures?
By 'footprint' - I am referring to the bulk/volume of the hitch - and if too large a footprint, would this have an adverse/negative impact?

[ ] Is complexity in tying balanced against the desired effectiveness of the hitch/knot? I presume that you wish to avoid overly complex knot structures - and that you are seeking to employ the least complexity to achieve the desired objective?
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 20, 2019, 03:45:31 PM
The questions about surgical knots in general are good ones. Most surgical knots originated from when suture was composed of natural materials (cotton, silk, intestine, or even wire). Most modern sutures are monofilament, like fishing line, and may or may not dissolve over time. Monofilament sutures are less reactive (less scarring and inflammation), more resistant to infection, cause less sawing through tissue, etc. But knot techniques have changed little. It is a little like a fisherman who ties on the line with a lot of square knots.

The choice of suture and knot depends on a lot of conflicting factors: ease of tying, knot security, ability to tie down tightly, cyclic loading, knot profile, resistance to breaking, etc. Most surgical knots are not tied correctly. Look at the knots tied at your next emergency room laceration repair with a magnifying glass and you will see. A study out of the Mayo Clinic found that about 80% of knots were tied wrong. Howard Taylor and Alan Grogono suggested that the constrictor knot was the best knot for thing off blood vessels (Ann R Coll Surg Engl. 2014 Mar;96(2):101-5. "The constrictor knot is the best ligature").

In Ashley's book of knots, he states that Dr. Mayo used granny knots, and Mr. Ashley had to teach surgeon's to use square knots instead. Personally, I feel Dr. Mayo was correct and Ashley, incorrect. The first two knots are often tied down as a slip knot to secure the blood vessel or appose the tissue. A slipped Granny slides down as a clove hitch, while a slipped square knot slides down as a cow hitch. The Granny slip resists back slipping better. Of course additional flat knots are needed at that point for security. The problem is that 7 or 8 flat knots is needed. That does create a bulky knot. Sometimes that does not matter, but in shoulder arthroscopy, a bulky knot is bad. For shoulder arthroscopy, self locking knots are sometimes used (similar to the the slip knot->cowboy bowline), but these loosen a bit during tying. Too loose is bad (more breakage). Too tight is bad (causes tissue to die and then falls out). Most of the time, picking the best knot is a compromise in which factor you want and what you are willing to deal with.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: agent_smith on September 20, 2019, 04:44:53 PM
Isleofgough:

In reading your last post, I am left wondering if your references to 'slipped' are in fact a noose?
The term 'slipped' has a certain meaning in knotting. A knot that is 'slipped' can be easily/rapidly untied by pulling on a tail segment.

Also, it appears that the majority of your hitches have single leg loading profile. Meaning that your hitches are tied from a linear, open ended length of cord/material. This is in contrast to tying a hitch from a circle (ie round sling). For example, #1763 Prusik hitch is tied from a circle - and thus has dual leg loading. In contrast a Blakes hitch is tied from a linear open ended length of cord and has single leg loading profile.

And, they appear to be loaded in one direction only; uni-axial loading (ie there is one SPart and one tail). Rare to see biaxial loading profile?
For example, the constrictor hitch can be biaxially loaded (2 SParts) or uni-axially loaded (1 SPart).
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 20, 2019, 05:07:38 PM
I may be using the term "slipped" incorrectly, but that is how it is usually used in surgery. Yes, it is a noose, not a a slip loop to undo a knot.

Both the double constrictor and single constrictor used in surgery have biaxial loading. In the case of tying in a tube, both ends are tied under the drain through the skin, so tension pulls on both ends. A single constrictor ligation of a vessel also has biaxial loading. The only cases of uniaxial loading are when a running suture is done. Many incorrectly tie the initial knot down flat, but that actually increases the chance of breakage. Just tying as a noose, though, can over tighten tissue leading to damage. A common way of avoiding that is to use a Revo knot (one reversed half hitch somewhere in the knot).

The advantage to tying a granny knot and then converting it to a noose is that it doesn't back slip during the creation of the knot. It is generally impossible to convert any noose/slipped knot back to a flat knot after tying in surgery, so flat knots are added to secure the noose. There are other ways of securely tying, such as the Mayo Clinic TSOL knot, which basically is a European death knot with a square knot tied on the ends to prevent loosening. The problem is that without clamping the suture (a bad thing), it is very difficult to get tight, though it is very secure.

We do have a Blake's hitch type knot that is useful in laparoscopic surgery (though it is created to reduce widening of the loop, which is opposite the forces for which a Blake's hitch or Prussik are used), called the Melzer:
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 20, 2019, 06:20:13 PM
Although it is a bit off topic, the Melzer knot actually works best as drawn above, rather than with a clove hitch for the terminal wraps. There are two other knots that are used all the time in surgery, with similar desired properties: a zip tie equivalent. Neither have names, and they both depend on perfect dressing of the knots. I would not be surprised if the company that makes the pretied version uses a drop of superglue to keep the dressing. They are described in the patent: http://www.google.com/patents/EP0477020A1?cl=en
I have never seen any discussion of their properties, but they are used all over the world every day.

For locking knots, there are over a dozen which are not even described in Ashley's book of knots: SMC, Dines, Outback, Pretzel, Weston, West Point, Gea, Mishra 1 and 2, Duncan, Tayside, Giant knot, and others.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Dan_Lehman on September 21, 2019, 01:13:11 AM
Although it is a bit off topic, the Melzer knot actually works best as drawn above, rather than with a clove hitch for the terminal wraps.
I see exactly a clove h. in the tail end of this
knotting above!?

As a general *tactic*, how might this work:
1) form a broad loop in the pulled-on part,
and
2) knot variously around this, SUCH THAT
3) this knotting of the "working" end will enable
initial tightening of the knot as desired,
AND THEN
4) the tail end can be drawn through the
"1" loop which is then drawn down upon
it to nip/hold it.

In short, IMO this is the point of the Stevedore knot
--a stopper knot knob that is hardly much bulkier
than simpler knots (for pulling through a hole),
but whose wraps can provide gripping against
the straight-through-tuns SPart whose turn
nips the tail : with tight wraps the SPart's hard
nip on the tail (which terminates those wraps)
can be sustained.
SO, in general outline, this is a tactic to try to use
for designing some of these surgical knots, it seems.

(A general way to form a stopper is to fashion
some noose and then *noose* the tail
--Ashley's stopper does this from a slip knot.)

Oh, the breadth of my conjectured initial loop
above is to leave ample real estate on that line
for gripping and pulling and setting the knot
(without tightening the loop, until ready).

--dl*
====
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 21, 2019, 01:24:43 AM
My diagram may be a bit misleading, as I show the tail off to the left, but if you look closely, it is a cow hitch in my illustration. I think it works better as a cow hitch as it was originally described: see https://www.laparoscopyhospital.com/extracorporael_knot.html and https://books.google.com/books?id=0PsEGivLBAwC&pg=PA34&lpg=PA34&dq=melzer+knot+1991&source=bl&ots=WjAmckNuIj&sig=ACfU3U1ygvf2cMCY4WQnB7jCeP8G84gekg&hl=en&sa=X&ved=2ahUKEwit7_yk0-DkAhXFpZ4KHXnBCW04ChDoATAAegQIBxAB#v=onepage&q=melzer%20knot%201991&f=false
Title: Re: Surgeon's modification of Double constrictor knot
Post by: agent_smith on September 25, 2019, 09:37:07 AM
I read your paper on extracorporial knots- very interesting.
Some of your terminology could (in my view) be aligned with the concept of chirality (handedness).

For example; in the attached diagram, one loop has Z chirality and the other loop has S chirality.
This is an improvement over descriptors such as 'under-over' and 'over-under' which could be misinterpreted if the reference frame is not clear.

I am also curious as to how some of your 'binder' hitches (eg Constrictor) are biaxilly loaded?
I understand this to mean that both SParts are loaded equally.
In your surgical contexts, maybe each SPart is not under an identical loading profile? Or is there mirrored (identical) loading on each SPart?
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 25, 2019, 09:44:40 PM
I referenced the paper (which is not mine) just to show the configuration of the Melzer knot. It is an interesting paper, and relatively little has been written comparing various knots where the tension in tying can only be in the directions away and towards yourself (which is the common denominator of  extracorporeal knots). These knots are tied outside the body and slid down through a tube into the body to secure a structure. Most of them are what you would call a noose, but a few lock into place, or added half hitches are placed to prevent unslipping. Lots of institutions and surgeons have given their own names to these types of knots, and most have little advantages over previously described knots (like the West Point knot, Wiese, Mishra, etc.). You are right that the terminology can be confusing. I changed the term "slip knot" in my book to "noose" based on the comments on this thread. What you describe as chirality reminds me of enantiomers in organic chemistry. They can be difficult to depict with a two dimentional diagram.

I personally only teach one knot that is similar to a zip tie: the Melzer. I show only one locking knot: the Outback knot. For nooses, I describe the differences between a converted square and granny knot as well as show how to tie a Nicky knot (which is a noose converted from a granny version of a surgeon's knot). The other knots don't have much to offer over these few.

But back to biaxial loading, a drain is tied to the skin, but in such a way that the skin is not pinched and the drain doesn't lie immediately adjacent to the tube. The advantage of a constrictor or double constrictor over the usual way of tying this knot is that it is self tightening and functions a bit like a Prussik to prevent sliding of the tube. What I proposed is tying the constrictor knot first around the tube and then suturing with a loose knot to the skin. There will be biaxial loading, but since the double constrictor is not symmetric, it will tighten a bit more in response to tugging on one side versus the other. The standard way of tying in a tube looks somewhat like this:
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Dan_Lehman on September 25, 2019, 11:08:40 PM
Some of your terminology could (in my view) be aligned with the concept of chirality (handedness).

For example; in the attached diagram,
one loop has Z chirality and the other loop has S chirality.

Except that the images are wrongly labelled :
the "Z" & "S" belong on each other's image.
(Looking down at the respective turns, the
"Z" should --like Z-laid rope-- turn to the right,
and so on.)


--dl*
====
Title: Re: Surgeon's modification of Double constrictor knot
Post by: agent_smith on September 26, 2019, 03:17:50 AM
Quote
Except that the images are wrongly labelled :
the "Z" & "S" belong on each other's image.

Are you sure?
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 26, 2019, 09:35:59 PM
I am no expert, but it would seem that direction of rotation would be hard to  determine with that small diagram, since you don't know the reference point. Are you supposed to be looking from the back or front of the knot? Is the knot supposed to be upside down with the loop at the top?

I am reminded of sheep herding, where one does not give "right" or "left" commands but clockwise or counterclockwise rotation with the reference point of the dog facing the sheep. (and 'walk up' and 'get out' for towards and away from the sheep)  Depending on the position, left to the handler might be clockwise or counterclockwise. If one was looking from the ground upwards, the direction or rotation would be reversed.

Similarily, chirality has to have a x, y, and z axis, and if you are looking from the negative z to the positive z direction, rotation will be opposite from looking from the positive to negative z direction. So you need a reference point. I would think it would be from a directional curve from what has been tied to what additional wraps are being created (in 3D, ordered numbering of points along a curve). I know how it is defined in organic chemistry for four ordered atoms, but I think chirality just would be confusing to someone trying to learn to tie a knot. Why not just define directions from the perspective of the person tying the knot looking downwards?

Here is the same diagram (but reversed based on Mr. Lehman's comment) looked at from the bottom, top, front, and back (I did not change the labels, so they are either all correct or all incorrect). I think this would be confusing.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: agent_smith on September 27, 2019, 12:04:44 AM
I would comment that chirality is the logical way to describe a loop.

A loop will be either S or Z chirality (ie handedness).

It is like your left hand and your right hand...in that your right hand will always be your right hand - you cant flip your hand over and turn it magically into a 'left' hand.
Same goes with gloves - one will always be 'left' and the other 'right'.

Bowlines are another example of where chirality plays a role (see attached images).

I have attached some images to explain.

I think if you are writing or presenting a technical paper on knots - the concept of chirality should feature in your explanation!

EDIT NOTE: Yes - your images in red are all reversed...the S should be Z; and the Z should be S.
It shouldn't be confusing...a quick rule of thumb is to apply what I refer to as the 'right hand rule' (same as it applies to direction of magnetic fields in physics).
If you hold your hand hand in front of you - point your thumb up - then curl your fingers. This will create a right chirality twist.
You can apply the right hand rule to any loop - it is universal in its application.
When applying the right hand rule, if loop doesn't match the curl of your fingers, then it must be the opposite chirality (ie left).
A loop is always one or the other...it cant be both!
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 27, 2019, 01:34:04 AM
I see what you mean based on your diagram. The figure in the article would be confusing, as the loop is actually going downward despite the free end being shown lower. It is one of the reasons I think 3D diagrams are a lot more helpful than a figure from Illustrator or equivalent.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: agent_smith on September 27, 2019, 05:35:58 AM
It really shouldn't be confusing...but, yes - if the image is not clear, then it may be hard to ascertain the chirality.
That's more of an accuracy issue... in that the illustrator needs to take care when drawing the knot structure...

I've added an image of the Constrictor hitch to show how chirality plays a role.
A Constrictor can only be built from 2 loops that have the same chirality.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 27, 2019, 09:31:20 AM
You may be right that it is an important concept that I should include in my book, since I emphasize the benefits of a granny noose over a square knot noose. The Granny would have the same chirality of both loops, whereas the square knot noose has reversed chirality. The physics principle would be that reversed chirality would be additive for frictional force, whereas same chirality is exponential (based on the Capstan equation).
Title: Re: Surgeon's modification of Double constrictor knot
Post by: agent_smith on September 27, 2019, 04:16:43 PM
You definitely should address the concept of chirality in your book - without which, your book would not be authoritative.
It would be instructive to introduce the Constrictor hitch to your readers, showing both S/S and Z/Z chirality forms.

Also, I would recommend that you carefully define what a 'turn' is.

Xarax has done a lot of work on hitches - it may be worthwhile to run some of your ideas past him.
He has devoted much of his time and energy to discovering and exploring a vast array of hitches.

Xarax convinced me to be careful when describing a 'turn'.
At the very least, use terms such as:
[ ] U turn = 180 degrees (Pi radians - 3.1415926 radians)
[ ] Turn = 360 degrees or 2 Pi radians
[ ] Round turn = 540 degrees or 3 Pi radians (9.42478 Pi radians)

And the term 'riding turn' should also be defined - as it plays an important role in how hitches work.

Sounds like you have a good handle on the capstan effect and capstan equation.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Isleofgough on September 28, 2019, 07:56:35 PM
Regarding creating a slip knot within a slip knot: there is a surgical knot that is used to end a continuous suture that does that. It is called the Aberdeen knot. It is like crocheting.
Title: Re: Surgeon's modification of Double constrictor knot
Post by: agent_smith on September 29, 2019, 03:24:09 AM
For the 'Aberdeen knot' I found this paper:
Link: https://www.researchgate.net/publication/5886805_The_Ultimate_Aberdeen_Knot

Looking at the images in that paper - it appears to be constructed from 2 inter-linked #206 Crossing hitches (aka Munter hitches).
Interesting concept.

Hope Xarax will look at this?
Title: Re: Surgeon's modification of Double constrictor knot
Post by: Dan_Lehman on October 01, 2019, 06:26:26 PM
Quote
Except that the images are wrongly labelled :
the "Z" & "S" belong on each other's image.

Are you sure?

In a way, yes :: the "way" is the direction of the turn
at the (first) deviation from *straight*.  Look at your
bowline examples : IFF you continue the nipping
loop's SPart-first turn into a helix, it runs off to the right,
"Z"-like.  OTOH, if you form the nipping loop and then
rotate some nipped object within it so as to render the
nipping loop into a pure helix, ... left-/S-handed.
.:. IMO, the greater significance (i.p., for laid rope)
is the initial turn, not what follows.

Perhaps the better case to address is that of a rolling hitch,
where the direction shows so well & repeatedly in its
coils, contrasting with its initial turn.

--dl*
====