Effect of Diameter and Type of Suture on Knot and Loop Security.

The loop and knot securities of two polyfilament and two monofilament sutures of four diameters (3.0, 2.0, 0, 1) were evaluated with a tensiometer for four four-throw knots, known to be secure with a 2.0 polyfilament suture. Loop security of Monocryl 1 is low, being 14.7 ± 3.0 Newton (N) for a three-throw half-knot (H3) and 15.4 ± 2.4 N and 28.3 ± 10 N for two (SSs) and four (SSsSsSs) symmetrical sliding half-hitches. This is lower than 18, 24, and 46 N for similar knots with Vicryl. Polyfilament sutures have excellent knot security for all four diameters. Occasionally, some slide open with slightly lower knot security, especially for larger diameters, although this is not clinically problematic. Knot security of monofilament sutures was unpredictable for all four knots, especially for larger diameters, resulting in many clinically insecure knots. A secure monofilament knot requires a six-throw knot with two symmetrical sliding half-hitches or two symmetrical half-knots secured with four asymmetric blocking half-hitches. In conclusion, with polyfilament sutures, four- or five-throw half-knot or half-hitch sequences result in secure knots. For monofilament sutures, loop and knot security is much less, half-knot combinations should be avoided, and secure knots require six-throw knots with four asymmetric blocking half-hitches.

What is the Best Surgeon's Knot? Evaluation of the Security of the Different Laparoscopic Knot Combinations.

STUDY OBJECTIVE: To investigate the security of various knot combinations in laparoscopic surgery. DESIGN: Prospective nonrandomized trial (Canadian Task Force classification II). SETTING: Storz Training Centre, Sao Paulo, Brazil. INTERVENTION: Different knot combinations (n = 2000) were performed in a laparoscopic trainer. Dry or wet 2.0 polyglycolic acid or dry 2-0 poliglecaprone 25 was used. The tails were cut at 10 mm, and the loops were tested in a dynamometer. The primary endpoints were the forces at which the knot combination opened or at which the suture broke. Resulting tail lengths were measured. MEASUREMENTS AND MAIN RESULTS: Surprisingly, the combination of a 2-throw half knot (H2) and a symmetric 1-throw half knot (H1s) (a surgical flat knot) opened at <1 Newton (N) in 2.5% of tests and at <10 N in 5% of tests. This occasional opening at low forces persisted after 1 or 2 additional H1s knots. A sequence of an H2 or a 3-throw half knot (H3) followed by a H2, either symmetric or asymmetric (H2H2 or H3H2), resulted in 100% secure knots that never opened at forces below 30 N. Other safe combinations were H2H1s followed by 2 blocking half hitches, and a sequence of 5 half hitches with 3 blocking sequences. CONCLUSION: A traditional surgical knot (H2H1s) occasionally opens with little force and thus is potentially dangerous. Safe knots are H2H2 and H3H2 combinations, a sequence of 5 half hitches with 3 blocking sequences, and H2H1s together with 2 blocking half hitches.

Different Blocking Sequences Performed by Laparoscopy.

STUDY OBJECTIVE: To demonstrate the application of different knot blocking sequences in laparoscopic surgery. DESIGN: A step-by-step demonstration of different blocking sequences performed by laparoscopic surgery (Canadian Task Force classification III). SETTING: Private hospital in Curitiba, Paraná, Brazil. INTERVENTION: The correct placement of one knot over the other is rarely taught in the surgical literature. Laparoscopic knot-tying techniques may be performed using one hand (monomanual technique) or alternating both hands (bimanual technique). Rotation of the needle holders around the thread (clockwise or counterclockwise rotation) is very important to have a symmetric or an asymmetric configuration of the knot, which affects the stability of the entire knot sequence. The monomanual knot-tying technique needs to alternate the rotation of the needle holder, and the bimanual technique does not when performing half knots (square or flat knots). The half hitch is an asymmetric knot that is obtained when the surgeon makes asymmetric traction on one thread (passive thread) and place the knot using the other thread (active thread). To block 2 half hitches, the surgeon needs to change the active and the passive threads. Beginners in laparoscopy commonly make mistakes tying knots, leading to an insecure knot sequence that may slip and/or open under minimal forces. In this video, we demonstrate different types of blocking sequences performed by laparoscopy applied in different surgical procedures. Ethics Committee approval was obtained for this video. CONCLUSION: Knot-tying is a basic surgical skill that must be mastered by all laparoscopists.