Knot Security in Gynecologic Surgery: Why Technique Matters as Much as Material

INTRODUCTION: Suture failure contributes significantly to surgical morbidity, with vaginal cuff dehiscence occurring in 0.14–4.1% of hysterectomies and 67% of cases resulting in bowel evisceration requiring emergency intervention. Despite the fundamental importance of knot security to surgical outcomes, there remains a paucity of data on the optimal pairing of suture material with tying technique. While previous studies have compared knot configuration or instrumentation exposure, no investigation has systematically examined how the three primary open surgical tying techniques (one-handed, two-handed, and instrument tying) affect tensile strength and failure mechanisms across the spectrum of suture materials commonly used in gynecologic surgery. Understanding these material–technique interactions is critical for surgical education and evidence-based practice. OBJECTIVE: To evaluate how different open surgical knot-tying methods (one-handed, two-handed, and instrument tying) affect the tensile strength at failure and mode of failure across seven suture materials commonly used in gynecologic surgery. METHODS: Seven 0-gauge suture materials were tested: polydioxanone, polyglactin 910, silk, chromic gut, poliglecaprone 25, polypropylene, and polyester. A single investigator tied each material 20 times using one-handed, two-handed, and instrument tie techniques in 2=1=1=1 configuration (420 total knots). The order of ties was randomized within each technique to mitigate performer bias. Knots were secured on a standardized jig (50-mm separation) and tested on a Mark-10 tensiometer at a rate of 3 mm/minute until failure. Failure was defined as suture breakage or knot slippage >3 mm. Peak tensile force (Newtons) was recorded. One-way ANOVA compared techniques within each suture type, while a two-way 7×3 ANOVA evaluated joint effects. Chi-square tests assessed the associations between technique and failure mode. Bonferroni correction controlled family-wise error. RESULTS: Two-way ANOVA revealed significant effects for both suture material (F=7.07, p<0.01) and tying technique (F=15.01, p<0.01), with a critical suture×technique interaction (F=6.56, p<0.01) indicating that optimal tying technique depends on suture material. Four sutures showed significant technique-dependent differences: polyester (p<0.01), polypropylene (p<0.01), silk (p<0.01), and polyglactin 910 (p<0.01). Polyester and polypropylene demonstrated the weakest tensile strength with instrument ties (25.80±17.65 N and 19.90±14.80 N, respectively) but exceeded 60 N when hand-tied (p<0.01 for both). Conversely, polydioxanone achieved the strongest tensile strength with instrument ties (59.50±26.63 N) versus one-handed (35.52±23.55 N, p=0.01). Polyglactin 910 one-handed knots demonstrated the highest mean strength overall (64.65±36.92 N), significantly exceeding instrument (28.82±22.58 N, p<0.01) and two-handed (33.65±23.86 N, p<0.01) techniques. Failure mechanism analysis revealed instrument ties were disproportionately prone to slippage rather than breakage: 100% of polyester, 95% of polypropylene, 95% of silk, and 90% of polyglactin 910 instrument-tied knots failed by slippage versus 30–55% of hand-tied knots (p<0.01 for all comparisons). Hand-tied knots typically failed by breakage at higher tensile forces. Chromic gut and poliglecaprone 25 showed consistently low tensile strength (25–40 N) across all techniques without significant differences. CONCLUSIONS: No single tying technique proved universally superior across all suture materials. The significant material–technique interaction demonstrates that optimal knot security requires matching the tying method to specific suture properties. Braided sutures (polyester, silk, polyglactin 910) and certain monofilaments (polypropylene) showed marked vulnerability to slippage with instrument ties, while polydioxanone performed optimally with this technique.