Knot Security of 5 Metric (USP 2) Sutures: Influence of Knotting Technique, Suture Material, and Incubation Time for 14 and 28 Days in Phosphate Buffered Saline and Inflamed Equine Peritoneal Fluid.

This research studies the stability of different types of knots tied in three commonly used suture materials when incubated in various fluids. The researchers found that the mechanical properties of suture materials greatly affect knot security, and that certain knot types provide better stability in some materials.

Study Design

• The researchers conducted an in vitro, or lab-based, mechanical study to evaluate the knot security of three types of knots created with three commonly used suture materials. The suture materials used were a glycolide/lactide copolymer, polyglactin 910, and polydioxanone.
• The knots were tied around a 20 mm rod, then tested for stability after being tied and after incubation for 14 and 28 days in two types of fluid. One was a representative physiological fluid (phosphate buffered saline or PBS) and the other a pathological fluid (inflamed peritoneal fluid).

Testing and Results

• The knots were tested to failure in distraction, with the force required to break the suture and the mode of failure recorded. Additionally, the researchers compared the results for differences across knot types, suture materials, and incubation times and conditions.
• They found that for polydioxanone sutures, there were significant differences in the force needed to break square knots compared to surgeon’s knots or triple knots. However, there was no significant difference between the force required to break surgeon’s knots and triple knots.
• The force required to break all types of knots increased after incubation in PBS.
• In contrast, with a glycolide/lactide copolymer, there was no difference in force required to cause knot failure across knot types.
• For polyglactin 910 sutures, a significant difference was noted between square knots and triple knots.
• The study also found that incubation in inflamed peritoneal fluid caused a larger and more rapid decrease in the force required to cause knot failure compared to incubation in PBS.

Conclusions

• The researchers concluded that the mechanical properties of suture materials significantly affect knot security.
• The square knot was deemed insufficient to create a secure knot with polydioxanone.
• Additional wraps above a surgeon’s knot may provide extra stability in some materials, but the study suggests this increase might not be justify the extra effort or be clinically relevant.
• Out of the materials tested, glycolide/lactide copolymer demonstrated excellent knot security.