How to tie dangerous surgical knots – easily. Can we avoid this?

Objective Secure knots are essential. Previous publications have concentrated on security of different knot types, but could individual technique be important? Determine whether the technique of formation of each layer of a surgical knot is important to the security of the knot formed. Design study Prospective analysis of technique on knot security Materials and methods Senior and resident surgeons, and medical students, tied knots with three techniques, using four study materials, 2/0 polyglactin 910 (vicryl), 3/0 polydioxanone (PDS), 4/0 poliglecaprone 25 (monocryl) and 1 nylon (Ethilon); a standard flat reef knot (FRK), knots tied under tension (TK), and knots laid without appropriate hand crossing (NHCK). Each knot technique was performed reproducibly, and security determined by distraction with increasing force, till each material broke, or the knot separated completely. Results 20% of flat reef knots (FRK) tied with all suture materials slipped; all knots tied with the other two techniques, with all materials, slipped, TK (100%) and NHCK (100%). The quantitative degree of slip, was significantly less for FRK (mean 6.3% 95%CI 2.2-10.4%) than for TK (mean 312% 95%CI 280.0-344.0%) and NHCK (mean 113.0% 95%CI 94.3-131.0%). The mean lengths of suture in loops held within knots, tied under tension (TK mean 17.0mm 95%CI 16.3-17.7mm), and tied without appropriate hand crossing (NHCK mean 16.3mm 95%CI 15.9-16.7mm) were significantly lower than for flat reef knots (FRK mean 25.1mm 95%CI 24.2-26.0mm). The first two types of knot may have tightened more than anticipated, in comparison to flat reef knots, with potential undue tissue tension. Conclusion Meticulous technique of knot tying, is essential for secure knots, appropriate tissue tension, and the security of anastomoses and haemostasis effected. Strengths and limitations The study design was simple, with equal numbers of knots tied for each technique, and for each material. Only a small number of participants tied knots, limiting any assessment to the effect of the knot tying technique. No inference could be drawn regarding the effect of seniority of participant. A relatively small number of knots were tied with each of the materials limiting more detailed assessment of the effect of the suture material and size on knot security, or whether material and size had any significant influence.