A comparison of the strength of knots tied by hand and at laparoscopy

The strength of knots tied at laparoscopy was compared with that of hand-tied knots.

The force needed to undo or break eight types of knots that were tied in fresh postmortem human stomachs was measured. The knotting performance of nylon, polyglactin 910, braided silk, polytetrafluoroethylene, braided polyester fiber, braided polyester suture, polyamide 66, and polydiaxone was also compared.

Measurements of knot strength of two to six half hitches (hand tied) showed that four half hitches were necessary to tie a secure nonslipping knot with most monofilament threads (nylon, polytetrafluoroethylene, braided polyester suture, and polyamide 66), while three half hitches were adequate to secure a knot when polyglactin 910, braided polyester fiber, silk, and polydiaxone were used. Additional throws did not increase knot strength once the knot no longer slipped (p = NS). Some commonly tied knots, three half hitches and surgical knots at laparoscopy were weaker than the same hand-tied knots (p < 0.05) but an additional throw increased knot security (p < 0.01). Differences between laparoscopic and hand-tied knot strengths were greater for monofilament than multifilament threads. There was a wider distribution of strengths for laparoscopically tied than hand-tied knots. Four half hitches were the most secure configuration for laparoscopically tied knots and were significantly stronger than three half hitches and surgical knots (p < 0.01). The extracorporeally tied slipknot (Roeder loop) was significantly less secure than four half hitches (p < 0.05).

This study demonstrates that laparoscopically formed knots may be weaker than those tied by hand and shows that improvements in knot strength at laparoscopy can be achieved by choice of optimal knot configuration for different suture materials.