The effect of six knotting methods on the biomechanical properties of three large diameter absorbable suture materials.

Objective: To evaluate the effect of 6 different knotting methods on the mechanical properties of 3 large absorbable suture materials used in large animal surgery.

Study Design: In vitro mechanical study. Sample Population- Knotted suture loops (n=15 per group).

Methods: Suture loops were created between two low-friction pulleys with either 2 polydioxanone, 2 polyglactin 910 or 3 polyglactin 910. Strands were tied using 1 of 6 knotting technique: square knot, surgeon knot, clamped surgeon's knot, sliding half-hitch knot (HH), Delimar knot and self-locking knot (SLK). A single cycle to failure test was performed on each suture loop with a distraction rate of 100 mm/min. Failure modes were evaluated and breaking strength, elongation to failure and stiffness were compared.

Results: All loops except two HH failed at the knot by acute breaking. The double-stranded SLK was both stronger and stiffer than all other knots for each suture material. Clamping the first throw of the surgeon knot decreased load to failure significantly (143.11 +/- 8.64 N) compared with not clamping (159.21 +/- 6.14 N) for polydioxanone. Stiffness and elongation to failure were respectively lower and increased for 2 polydioxanone compared with both polyglactin 910 materials for all knotting techniques.

Conclusions: Knotting techniques do influence structural properties of suture loops. The double strand loop conferred stiffer and stronger properties to the SLK CLINICAL RELEVANCE: Clamping the first throw of polydioxanone should be avoided when tying a suture under tension even using large diameter suture materials. Using a SLK might be considered as a useful alternative when excessive tension is present.