Tensile strength of a surgeon's or a square knot

Objective: To test the integrity of surgeon's knots and flat square knots using 4 different suture materials.

Study design: Chromic catgut, polyglactin 910, silk, and polydioxanone sutures were tied in the 2 types of knot configurations. For all sutures, a 0-gauge United States Pharmacopeia suture was used. Knots were tied by a single investigator (J.B.). The suture was soaked in 0.9% sodium chloride for 60 s and subsequently transferred to a tensiometer where the tails were cut to 3-mm length. We compared the knots, measuring knot strength with a tensiometer until the sutures broke or untied.

Results: A total of 119 throws were tied. We found no difference in mean tension at failure between a surgeon's knot (79.7 N) and a flat square knot (82.9 N). Using a chi(2) test, we did not find a statistically significant difference in the likelihood of knots coming untied between surgeon's knots (29%) and flat square knots (38%).

Conclusions: Under laboratory conditions, surgeon's knots and flat square knots did not differ in tension at failure or in likelihood of untying.