Strength Comparison of Melzer-Bueß and Schnelsen Laparoscopic Knots: Evaluation of Enhanced Variants

Purpose: This study compares the tensile strength of recently developed Schnelsen laparoscopic knot variants with that of the Melzer-Bueß knot to provide recommendations for clinical application. Methods: The Schnelsen knot in its original form (Schnelsen 1) and with one (Schnelsen 2) and two (Schnelsen 3) additional loops was compared with the Melzer-Bueß knot. All knots were tied in a laparoscopic training device (Lübecker Toolbox) using two types of non-absorbable suture materials (mono- and polyfilament). For each combination of knot and suture material, three surgeons each tied 10 knots (total = 240 knots). The loops were mounted on a tensile testing machine and loaded until failure, either by rupture or slippage. Knot strength was assessed by the clinical failure load, F fail , defined as the maximum load without exceeding a slippage of 3 mm. The influence of factors such as knot type or suture material on F fail was analyzed using a generalized linear mixed model (GLMM). Results: Most of the knots failed by slippage. Nevertheless, the results for monofilament material that show the established Melzer-Bueß and Schnelsen 1 have a F fail of 3.74 N and 3.05 N, respectively. The new proposed Schnelsen 2, on the other hand, shows a higher F fail with 5.15 N. According to the GLMM, the use of polyfilament material increases F fail by 97 %. Conclusion: The results show that under these conditions, the new version of the Schnelsen knot with one additional loop (Schnelsen 2) shows higher F fail compared to the Melzer-Bueß knot, while still offering the lower complexity of the Schnelsen 1 knot.