Tying different knots: what forces do we use?

Abstract

A study was performed to determine differences in applied interaction force between conventional open surgery and laparoscopic surgery during suturing in a non-clinical setting. In a laparoscopic box trainer set-up, experts performed two intracorporeal and two extracorporeal sutures on an artificial skin model. They also performed two instrument-tie knots and two one-hand square knots in a similar conventional training set-up. The force exerted on the artificial tissue (mean force, mean non-zero, maximum, and volume) and the time to complete a task were measured. For analysis purposes, sutures are divided in a needle driving phase (Phase 1) and knot-tying phase (Phase 2). Phase 1: Force values in laparoscopic suturing are significantly higher than in conventional suturing, except for the force volume during extracorporeal suturing versus the one-hand square knot. Phase 2: The mean force non-zero and maximum force during the intracorporeal knot are significantly higher than during the instrument-tie knot. The mean and maximum force during the extracorporeal knot are significantly higher than during the one-hand square knot. Furthermore, laparoscopic suturing takes longer time than conventional suturing. Expert surgeons apply significantly higher force during laparoscopic surgery compared to conventional surgery even though the same strategy is used. Aspects such as the limited visual and haptic feedback, and movement possibilities hamper surgeons' ability to assess the applied interaction force. Therefore it can be useful to provide additional force feedback about the applied interaction force during training in non-clinical settings.