The effect of knot geometry on the strength of laparoscopic slip knots

Abstract

To evaluate and compare the strength of six different knot geometries used in laparoscopic slip knots. The strength of six extracorporeal slip knots used in laparoscopic surgery was measured using a tensiometer. Two multiple-throw laparoscopic square knots (the intracorporeal two-turn flat square knot and the extracorporeal sliding square knot) were used as controls. Each knot type was tied five times, and each type was tied in random order by the same primary and assisting surgeons using a laparoscopic pelvic surgery training model. One-way analysis of variance was performed to detect significant differences in knot strengths, and the variability in knot strength for each knot type was determined by Tukey's multiple comparison test. A statistically significant effect for knot geometry was identified. The mean knot strengths +/- standard deviation (SD), measured in newtons, from strongest to weakest, were: 4S knot (28.01 +/- 11.45), fisherman's knot (22.45 +/- 6.89), modified Roeder knot (19.86 +/- 9.30), Roeder knot (15.77 +/- 7.02), Weston knot (7.28 +/- 7.96), and Duncan knot (6.55 +/- 0.95). The mean knot strengths for the multiple-throw control square knots were as follows: intracorporeal two-turn flat square knot (41.21 +/- 2.69) and extracorporeal sliding square knot (27.81 +/- 16.27). The intracorporeal two-turn flat square knot (control) was significantly stronger (P < .05) than all slip knots except the 4S and fisherman's knot. The 4S and fisherman's knots are the strongest laparoscopic slip knots and are the only slip knots similar in strength to multiple-throw square knots.