ROLE OF EXTRACORPORIAL KNOTS IN LAPAROSCOPIC SURGERY contd...

C. Commonly used “non-sliding” (static) knots

extracorporael knot clip

Figure 7. Non-sliding (static) knots

These knots are the only knots that can be used when the suture does not slide freely through the tissue and anchoring device. These knot configurations also theoretically avoid suture damage from abrasion and tissue damage during sliding. The major disadvantage of static knots is the propensity of the loop to loosen before the second half-hitch is seated to the point that it provisionally “locks” the knot. This occurs when using a single-lumen knot pusher. One method of minimizing this effect is by using a double-diameter knot pusher which holds the tissue loop tight as it advances sequential half-hitches (Surgeon’s Sixth Finger). (55,56,57,58)

Text Box: Step2. Three rounds are taken in front of the first half knot , over  both the limb of loop.

Roeder’s Knot (59)

Step1. One half knot is taken first

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extracorporael knot clip

Text Box: Step4:  Knot is stacked properly and then slide on the long standing part of the thread

Step3: A second half knot is taken around
one side of loop

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extracorporael knot clip

Roeder’s knot ( 1:3:1, One hitch three winds and one locking hitch)

Meltzer slip knot (59)

Step2. Three rounds are taken in front of the first double half knot over both the limb of loop.

Step1. Two half knot is taken first

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extracorporael knot clip

Text Box:  Step4: Stack the knot and trim the short end. Slide the knot into place with knot pusher under  tension.

Step3: Make two half hitches on the slidingstrand of the loop.

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Text Box: used instead of the Roeder knot to tie the medial end of the cystic duct during Cholecystectomy and to fix the cystic duct drainage cannula after trans-cystic clearance of ductal stones, as catgut is no longer available. PDS is the suture material of choice for Meltzer knot.

Meltzer knot ( 2:3:2, Two hitches, Three winds, Two half locking hitches, A slide)

Text Box: Step2. Four and a half rounds are taken behind the first half knot over long standing limb of thread.

The Tayside knot (59)

Step1: A single hitch (Half knot) is taken first

extracorporael knot clip
extracorporael knot clip
Text Box: Step4: Knot is stacked any excess tail is cut and then slid with the help of push rod.
Text Box: Step3:  A locking hitch is made by passing tail through the second and third loop.
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Text Box: The Tayside knot is suitable for use with all braided sutures (2/0 or stronger) as well as dacron. It is used with Dacron for ligation of vessels such as the azygous vein, splenic artery/vein or the inferior mesenteric artery/vein.

Weston Knot (60, 61)

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extracorporael knot clip

1 2

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extracorporael knot clip

3 4

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extracorporael knot clip

5 6

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7

The Weston slip knot was initially described in the obstetric and gynecology literature and is also used in arthroscopic surgery.The advantage of this knot is that it is relatively easy to tie outside, can then slip easily into place and be tightly secured. The post strand does not move throughout the knot; the loop strand is the longer strand which is moved to make the knot. The advantage of the Weston knot is that it locks readily and is not bulky.

Pre-tied loop

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  • The loop is drawn up into the metal sleeve.
  • The tube is then introduced through an abdominal port.
  • Once inside the abdomen the loop is advanced using the push rod.
  • A grasping forceps is placed through the loop and used to grasp the tissue to be ligated.
  • The loop is delivered over the tissue and the knot and push rod positioned at the base of the tissue.
  • The loop is then tightened around the tissue by tensioning the long end and applying pressure to the knot via the push rod causing it to slide.
  • The knot is locked firmly in place.
  • The graspers are removed and replaced by suture scissors to divide the long end prior to removal

Preformed loops are used to ligate tissue e.g. the base of the appendix, lung bullae, and a hole in the gall bladder during Cholecystectomy. If multiple loops are required, the push rod and introducer can be reloaded with a length of ligature and additional loops fashioned by a surgeon with knowledge of external slip knots.

A pre-formed loop can also be used to secure a divided vessel after it has been isolated by a grasper. A slight modification of this technique allows it to be used to secure smaller identified vessels. One end is clipped and the other controlled temporally by a grasper, which has already been passed through a loop. The vessel is divided and the loop slid into place and tightened before the grasper releases the vessel.

Endoloops are also useful for sealing a perforated organ if this is to be removed, e.g. perforation of the gallbladder during laparoscopic cholecystectomy where closure is necessary to prevent escape of gallstones into the peritoneal cavity. (59)

extracorporael knot clip
extracorporael knot clip

For Extracorporeal Knotting knot pushers are used. These knot pushers are of either closed jaw or of open jaw type.

Extracorporeal knot Ligation for continuous structure:

  • A push rod is threaded onto a length of ligature material approximately 1.5 m long.
  • A knot is tied at the end of the thread as it emerges from the straight end of the rod.
  • The end of the ligature emerging from the tapered end is grasped by atraumatic endoscopic grasper.
  • The grasper and catgut are then passed into an introducer tube
  • The introducer tube is then passed through an 11 mm cannula.
  • The grasper and ligature are extended into the cavity and passed to one side and behind the structure to be ligated.
  • A second grasper is introduced through a second port to grasp the ligature from the other side of the structure.
  • The first grasper releases the ligature and the takes it back from the second in front of the structure.
  • The first grasper and ligature are withdrawn from the abdomen through the introducer tube while the second is used to protect the structure from the suture.
  • An external slip knot is tied externally. The knot tied is determined by the size of vessel to be controlled and the material in use.
  • The knot is pushed into the abdomen by the push rod and positioned prior to tightening.
  • The rod is withdrawn a little and scissors introduced to cut the thread leaving a reasonably long end. (59)

Extracorporeal knotting is preferred in the following situations:

  • Ligature in continuity of large vessels
  • Suturing in areas of limited access where the working space is restricted
  • In the approximation of edges of defects where the force requires to approximate the edges is substantial (62)

Rules governing external slip knotting

  • the type of the thread must be 1.5m and the guage should be 2/0 or greater
  • The type of slip knot selected depends on the ligature material being used. Certain slip knots provide sufficient holding strength with catgut but not with other materials.
  • For any ligature material, the holding force (resistance to reverse slipping) of any surgical slip knot varies directly with its caliber. Thus the holding strength of a 1/0 slip knot is roughly twice that of the 2/0 equivalent.
  • Stiff hydrophobic monofilament material should be avoided as it exerts a lesser frictional hold and has a greater tendency to spill than braided. (62)

Suture material

A) Absorbable sutures

Catgut- Poor gliding ability

Vicryl- Good maneuverability

PDS- Excellent gliding ability, no need to follow during intracorporeal anastomosis

B) Non-absorbable sutures

Silk- it is braided and so more traumatizing

Prolene- Monofilament but has memory so makes it very tedious to use

Ethibond- Monofilament with less memory and better maneuverability than prolene (62)

Results: Most surgeons suggest becoming facile with one static and one sliding knot. However, a static knot can actually be used in all situations whereby a sliding knot can be only used if the suture slides freely through the tissue and anchoring device. For a knot to be effective it must possess the attributes of knot security and loop security. Knot security depends on 3 factors:

  1. )Friction
  2. )Internal interference
  3. )Slack between throws

Friction is greater for braided multifilament suture than for monofilament suture. Internal interference refers to the “weave” of the two suture limbs relative to each other. Internal interference can be increased by reversing the half-hitches and/or alternating posts. For compound sliding knots internal interference is increased by increasing the length of contact and the complexity of the “weave” between the two suture limbs. Slack between throws is eliminated by removing twists between the suture limbs prior to advancing a half-hitch and by past-pointing. Loop security is the ability to maintain a tight suture loop as a knot is tied, Figure (8). It is possible to have an ineffective repair in spite of good loop security if the suture loop is loose and does not adequately approximate the edges of the tissue to be repaired. Thus it is the knot which provides the best balance of loop security and knot security and can be easily and reproducibly tied. Loop security measured as loop circumference at 5 N preload. Knot security measured as maximum force to failure at 3 mm of crosshead displacement or suture breakage. (63,64,65,66,67,68,69,70,71,72,73,74)

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extracorporael knot clip

Text Box: Figure 8. (44) Evaluated loop and knot security of 6 sliding knots (Duncan loop, Nicky’s knot, Tennessee slider, Roeder knot, SMC knot, Weston knot) and 1 static knot (Surgeon’s knot).

Compound sliding knots are commonly “locked” into place by tension the wrapping limb or “flipping” the knot. Tensioning the wrapping limb, distorts the post limb, resulting in a kink in the post, increasing the internal interference and thus increasing the resistance of the knot from backing off. Sliding knots are commonly divided into non-locking and locking knots. Locking knots may be further divided into proximal locking, middle locking and distal locking knots according to where the wrapping limb deforms the post limb when it is tensioned.

Non-locking: Duncan loop

Proximal locking: Nicky’s knot

Middle locking: SMC knot, Tennessee slider

Distal locking: Weston knot, Roeder knot

Proximal locking knots are easy to lock especially when the loop tension is high. However, when locking some sliding knots, the loop tends to enlarge when “flipping” the knot. Proximal locking knots tend to cause more loop expansion (loss of loop security) than distal locking knots. Non-locking sliding knots (e.g. Duncan loop) resist slippage by the tight grip of the wrappings around the initial post. .(63,64,65,66,67,.68,69,70,71,72,73,74)

For externally tied slip knot a long length of ligature is required (100cm). It must be long enough to have the knot pusher threaded on to it, to be passed into the abdomen, round the structure to be ligated and to be brought out again and still have sufficient length for the surgeon to tie his / her knot. The knot chosen to complete the loop depends on the clinical situation and the material in use. modification of the Roeder knot was described in 1991 by Meltzer for use with PDS. The Tayside knot is safe for use with any braided material (2/0 or stronger). It supplies a degree of resistance to reverse slippage equivalent to a surgeons knot. It is used with Dacron for ligation of vessels such as the azygous vein, splenic artery/vein or the inferior mesenteric artery/vein. (59)

The holding and tensile characteristics of the extracorporeal slip-knot depend on the types of ligature material used and the types of knot applied. Slipknots tied with silk and polyamide are less secure than the equivalent knots tied with dacron, lactomer and polydioxanone. (30)

Securing A Sliding Knot

  1. ) Both static and cyclic loading studies have demonstrated that reversing post and alternating half-hitches following a base (i.e. compound sliding) knot is essential in providing both initial loop and knot security.
  2. ) Most compound sliding knots even newer knots (e.g. SMC) are more secure with RHAPs
  3. ) RHAPs can be performed by manually switching and rethreading posts or by flipping a half hitch. This can be performed with single or double diameter knot pushers.(63,64,65,66,67,.68,69,70,71,72,73,74)

Discussion: Laparoscopy is useful to treat surgical diseases, yet tying sutures in the cavity is a challenge. A knot to secure tissue approximation, which would be hand-made, secure, simple, easy, quick, reliable, and extracorporeal without extra mechanical devices constitute the essence of surgical practice because an unreliable suture knot can spoil the outcomes of an otherwise beautifully performed surgical procedure.

Surgeons are certainly not new to knotting, but they seem not to be aware of the possibilities and impact of the techniques of capsizing, flipping, and flyping. Understanding these techniques provides endoscopic surgeons an insight into the evolution of sliding knots, and a simple technique to additional improvements on the knots they use. (1)

The surgeon's knot provided the highest force to failure and the tightest loop circumference whether tied with No. 2 Ethibond (Ethicon, Somerville, NJ) or No. 2 Fiberwire (Arthrex, Naples, FL) suture. Among the sliding knots, the Roeder knot with 3 RHAPs showed the best balance of loop security and knot security when tied with No. 2 Ethibond or No. 2 Fiberwire. Sliding knots tied without RHAPs showed low force to failure and loose suture loops whether tied with Ethibond or Fiberwire. The addition of 3 RHAPs improved knot security and, in most cases, loop security of all the sliding knots. When tying a static surgeon's knot or a sliding knot with RHAPs, using No. 2 Fiberwire

increased the force to failure over comparable knots tied with No. 2 Ethibond. All knots failed by a combination of knot slippage and suture stretch. When using No. 2 Ethibond, securing most sliding knots with 3 RHAPs or tying a surgeon's knot changed the failure mechanism from knot slippage to suture stretch, suggesting that the maximum knot holding capacity of No. 2 Ethibond had been achieved when tying these knot configurations. However, even at failure forces twice that achieved with No. 2 Ethibond, suture slippage continued to occur with sliding knots with 3 RHAPs using No. 2 Fiberwire. This indicates that the maximum knot-holding capacity of No. 2 Fiberwire had not been achieved, and that further knot configurations should be tested. (75)

The modified Roeder knot (by adding a fourth loop around the standing end of the suture and a second half-hitch to the completed knot.) was significantly stronger than the standard Roeder knot. (76) The 4-S modification of the Roeder (by adding a fourth wrap around the suture loop and securing the loop in place with a square knot rather than a single half-hitch) is comparable in strength to the strongest laparoscopic multiple-throw square knots. a 2 polydioxanone and 1 polyglyconate 4S modified Roeder knot would be an acceptable alternative to the commercially available Endoloop, followed by 0 polyglyconate that exceeded the 1PDS. (77, 78, 79, 80)

Sterilization with either ethylene oxide or gas plasma of pre-tied, polyglyconate, or polydioxanone ligature loops significantly increases the in vitro likelihood of a modified Roeder knot untying. (81)

The load to ultimate failure reached plateau when 3 or more additional half-hitches were made for all knot configurations. As the number of additional half-hitches increased, the mode of failure switched from pure loop failure (slippage) to material failure (breakage). The SMC knot required a minimum of 2 additional half-hitches. The Duncan loop may need more than 3 additional half-hitches for optimal security. (82, 83, 84)

Measurements of knot strength of two to six half hitches (hand tied) showed that four half hitches were necessary to tie a secure nonslipping knot with most monofilament threads (nylon, polytetrafluoroethylene, braided polyester suture, and polyamide 66), while three half hitches were adequate to secure a knot when polyglactin 910, braided polyester fiber, silk, and polydiaxone were used. Additional throws did not increase knot strength once the knot no longer slipped improvements in knot strength at laparoscopy can be achieved by choice of optimal knot configuration for different suture materials. (85, 86)

Conclusion: A static surgeon’s knot provides the best balance of loop security and knot security within the knot configurations. A sliding knot without RHAPs has both poor loop security and knot security and should not be tied. The addition of 3 RHAPs improves knot security of all sliding knots tested and improves the loop security of most of the sliding knots tested. Loop security is a primary determining factor. The knot chosen should be the one which the surgeon can easily and reproducibly tie with good knot and loop security.

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