remains of an absorbable suture knot

[rjlittlefield]

Recently I had some skin surgery for which the incisions were closed with a single-strand running stitch of absorbable suture.

Of course I got curious about the technique, so I harvested a few of the knots just before they would have fallen off naturally.

Shown here is one knot that caused me to scratch other parts of my head, wondering how it came to be.

Transparent version, immersed in fluid:
(stereo pairs are crossed-eye)




Opaque version, photographed dry:




In the opaque version, it's easy to see that at the bottom of the knot there are three degraded monofilament strands. Those are places where the strands descended into skin and were absorbed, while the knot stayed above the surface, protected by an oily ointment.

Meanwhile, in the transparent version you can see that two of the three strands run essentially straight through the knot, with the third strand locked around them in a series of hitches.

At the other end of the knot, outside the frame of these photographs, each strand of monofilament terminates in a cleanly cut end.

I encourage you to stop at this point and carefully think about the situation: the stitch is made with a single strand of suture, but the knot incorporates three strands, each strand buried in skin below the knot and cut off cleanly above the knot, giving a total of 6 ends.

How and why was the knot made this way??

If you have been trained in suturing, the answer is probably obvious, although six ends may still give pause to think.

But if you have not been trained in suturing, then you may ponder long and hard and never come up with a plausible explanation. At least I hope that's the case, because that's certainly what I did.

While you consider the question, let me show you how the knot appeared a day or two before it came off.



Yep, three strands at the outer end of the knot, cleanly clipped. Presumably the other three strands dive back into the skin at the other end of the knot, but no details of that can be seen.

In the old days, I do not know how I would have solved this mystery, short of asking the surgeon.

But these days we have the internet, and once I found the right search string (youtube how to tie off a running suture), numerous videos appeared from which the answer could be gleaned.

Spend 20 seconds at the following URL, and you'll see the process as it is explained at 12:30-12:49 of the Duke Suture Skills Course: https://www.youtube.com/watch?v=TFwFMav_cpE&t=750s

In case that went by too fast, here's the schematic version showing various stages.





There's another bit of a different knot that I'm still unclear about, but I'll leave that for another day.

I hope you find this at least slightly as interesting as I did.

--Rik

Technical: high mag photos with Mitutoyo M Plan Apo 5X with Raynox DCR-150 on short extension giving 4.04X (5.5 mm field width on Canon R7, 22.8 mm sensor), continuous illumination with Jansjö LED. The fluid for immersion was Ronsonol lighter fluid, which was the first gentle solvent that would remove the oily ointment. Ethanol and acetone wouldn't touch the stuff. The in-situ macro shot was done with a 100 mm macro lens on the Canon R7, on tripod and tethered to my computer so I could see what I was doing to fly my head for framing and focus. That one is flash illumination, a 2-frame stack with extensive retouching to compensate for slight shift in view point.

[ap]

hey rik - im actually in the surgical field and that's exactly how its done with a single running suture. most likely was tied with an instrument (i.e. needle holder). the half throws are done one way and then another to prevent slippage. very cool pics!
andy

[ap]

btw how do you like your R7?

[rjlittlefield]

btw how do you like your R7?

It's working very well -- I'm happy with the purchase. I selected the Canon R7 because it's compatible with all my current glass, adapters, and workflow, plus it has full electronic shutter and a lot more pixels than what I had before. I was surprised and pleased by how much better the auto-focus works. Lenses that in the past would obviously go through an iterative process now just lock in almost instantly in one smooth movement. I am not pleased that the R7 still will not sync with flash at any speed in full electronic shutter, but it seems there's a good workaround for that using its synthetic "click" at beginning of exposure. So far the only unexpected downside is that in one extreme case -- with a long exposure and LOTS of sharpening in a deep stack with PMax -- I saw what looked like some systematic pattern of noise buildup that resulted in faint horizontal streaks in the final image. But I have not seen that in any subsequent work, so I'm not very concerned.

--Rik

[rjlittlefield]

im actually in the surgical field and that's exactly how its done with a single running suture. most likely was tied with an instrument (i.e. needle holder). the half throws are done one way and then another to prevent slippage. very cool pics!

Excellent -- I glad to see this makes sense to somebody in the field.

Now, perhaps you can explain that one "bit of a different knot" that I said I was still unclear about.

As best I recall, this was something that I idly scratched off about a week after surgery, when I was expecting bits and pieces to start coming off. Location would have been near the end of an incision, same place as the knot shown above but on the other eye.

Here it is:



To summarize: one strand, curled in the middle, with two cleanly cut ends, showing no sign of absorption at any point.

This makes no sense to me. At first I thought this thing was just the curl that was left over from an ordinary knot, after the other straight strand(s) had pulled out of the center.

But that would leave one end degraded from being embedded in tissue, like we see with the knot shown earlier.

This combination of curl with two clean ends looks like something that in other contexts could make a sliding stopper, but what is it for here?

--Rik

[ap]

hi rik
what do you mean by 'using a synthetic click"?
i think maybe the knot was prefabricated as part of the suture in order to anchor it though im not sure

[rjlittlefield]

what do you mean by 'using a synthetic click"?

See the discussion at https://www.photomacrography.net/forum/ ... 94#p284494 . If not clear, then ask there so the context will be better.

i think maybe the knot was prefabricated as part of the suture in order to anchor it though im not sure

Please say more about this possibility. I notice that the short end is purple, which is also unique among the stuff I collected.

--Rik

[J_Rogers]

Rik, I was curious about that second knot as well & so I sent the image to a family member who is a trauma surgeon. Funny thing is, he wasn't entirely sure how it was tied either. Said if it wasn't actually cut, then maybe it was intended to be a barbed tie off point - indicated by the thinner spot below the purple end. But ultimately didn't see any surgical reason why it would be done that way.

He did send me these if you want to know what was used:
https://www.jnjmedtech.com/en-US/produc ... one-suture
https://www.jnjmedtech.com/en-US/produc ... 910-suture

[rjlittlefield]

I had a follow-up today, so I talked to the surgeon about the mysterious bit of debris.

He had never seen photos like these before, so it took him a while to get his bearings also. Then he explained (as I heard it) that he stitches the eyelid incision using a sort of "belt and suspenders" approach, with one long running suture to close the incision, plus a number of individual single stitches to hold the edges exactly where he wants them. He says the picture looks to him like one of the individual stitches managed to get worked loose and pulled out of the skin before it had a chance to degrade very much.

To illustrate what I think I heard, I have done some crude reworking of the photograph to show what the stitch would have looked like as tied.



I forgot to explicitly ask about the suture material, but someplace in the discussion he mentioned "gut".

--Rik

[allanwalls]

Thanks for the most interesting followup, Rik.
It is not an uncommon practice in oculoplastics, or plastic surgery in general, to augment a primary, running closure of the eyelid with some individual reinforcing stitches at key points along the wound. This would be especially true if the "gut" mentioned by the surgeon was "plain gut", as opposed to the chromium impregnated "chromic gut" favored by other specialties. Plain gut loses its integrity so quickly in normal subcutaneous tissue that it is hardly ever used to close the skin except in situations like your own, where gentle approximation is the intent. Interestingly, because it is so rapidly broken down in the milieu of an acute surgical inflammatory change attending intestinal resection, chromic gut is an excellent material for creating the inner running, closure during intestinal anastomosis. This is the layer of suture that closes the inner mucosal and submucosal layers, preventing leakage of bowel content into the peritoneum, while a much more durable, braided, though still absorbable material, polyglactin (Vicryl) is used to close the muscular and serosal layers, providing structural integrity to the closure. Both types of suture are rapidly absorbed with the inner chromic knots likely being sloughed into the intestinal lumen within days. The eyelid is so well vascularized, that a clean wound, even following blepharoplasty, where a sizable gap may be left, would most likely heal quickly and uneventfully by secondary intention.
Allan Walls