The strength of surgical knots involves a critical interplay between friction and elastoplasticity

Abstract

Knots are the weakest link in surgical sutures, serving as mechanical ligatures between filaments. Exceeding their safe operational limits can cause fatal complications. The empirical nature of present guidelines calls for a predictive understanding of the mechanisms underlying knot strength. We identify the primary ingredients dictating the mechanics of surgical sliding knots, highlighting the previously overlooked but critical effect of plasticity and its interplay with friction. The characterization of surgeon-tied knots reveals the relevant ranges of tightness and geometric features. Using model experiments coupled with finite element simulations, we uncover a robust master curve for the target knot strength versus the tying pre-tension, number of throws, and frictional properties. These findings could find applications in the training of surgeons and robotic-assisted surgical devices.

Intracorporeal vs. extracorporeal open and closed knot tying techniques in laparoscopy: A randomized, controlled study

“…Knot tying is crucial in surgical procedures, in which knots serve as mechanical ligatures between filaments [ 1 ]. While various laparoscopic knot types exist, the flat square knot remains the most popular and reliable, given that slip knots are generally significantly weaker [ 2 ].…”

“…Although knot tying for open surgical procedures can be easily taught, trained, and performed, it is considerably more challenging in laparoscopic surgery [ 5 , 6 ]. Knot tying during open surgery permits greater exposure of the surgical field, provides superior tactile sensation, and permits the use of all six degrees of freedom compared to laparoscopic surgery [ 1 , 4 , 5 , 7 , 8 ]. In laparoscopic surgery, however, the surgeon must confront various obstacles, including indirect visualization, loss of freedom of movement, fixed port positions, and limited working space [ 4 ].…”

“…In laparoscopic surgery, however, the surgeon must confront various obstacles, including indirect visualization, loss of freedom of movement, fixed port positions, and limited working space [ 4 ]. Even experienced laparoscopic surgeons often consider knot tying to be difficult [ 1 , 5 , [7] , [8] , [9] , [10] ].…”