Purpose: Surgical knots are particularly challenged by high-strength suture material. It was hypothesized that sutures in a double-stranded looped configuration present mechanical advantages.
Methods: This in vitro biomechanical study repeatedly tested 12 different knots with a static distraction material testing machine with a constant tensile speed. The cow hitch, its altered version, and conventional half hitches were also tested on bovine tendon. Suture material was braided polyblend non-bioresorbable polyester. Primary outcome was knot security (stiffness) at clinical failure (≥3mm displacement). Secondary outcomes were knot size and loop security.
Results: Double-stranded looped knots were up to three times stronger than one and a half- and single-stranded knots. The cow hitch was stiffest (mean 185 [95% CI 172-197]Newton per millimeter [N/mm]) (p<0.001), followed by the Nice knot (169 [154-183]N/mm). It was stiffer than half hitches (65 [53-78]N/mm). These findings remained in tendons (82 [77-86] and 40 [32-49]N/mm, p<0.001). The cow hitch (7.6mm3) and Nice knot (6.1mm3) were smaller than half hitches (9.5mm3). Loop security did not differ between the cow hitch and Nice knot, but was higher in the cow hitch than half hitch (158 [120-196]N and 85 [57-113]N, p<0.001).
Conclusions: Double-stranded knot configurations with a loop on one side are mechanically stronger and stiffer, less bulky, and preserve applied tension during tying better than conventional knots. The best performing and technically most simple knots best suited to exploit enormous mechanical capabilities of modern high-strength suture material are the cow hitch and Nice knot.
Level of evidence: Not applicable due to the biomechanical nature of the study.
Keywords: Cow hitch (Lark's head); Half hitch; Knot; Knot security (stiffness); Loop security (tension); Size.
Copyright © 2018. Published by Elsevier Masson SAS.