Investigation of Two Double Throws and Three Single Throws Square Surgical Knots – A Preliminary Experimental & Computational Study on Knot Integrity

Abstract

In this study, the objective was to compare the knot integrity and efficiency between the two most commonly utilized surgical knots – the two double throws (2DT) and three single throws (3ST) knots via experimental testing and computational modelling. A single suture material Polyglactin 910 (Vicryl; Ethicon, Inc) was selected for this study and all sutures were of a 4-0-gauge size. 12 knotted suture samples (n=12) were prepared for each of the two surgical knot configurations. A tensile testing machine a load cell of 100N was utilized. The knots were loaded via a crosshead movement rate of 1mm/s throughout the test until knot failure, either by suture rupture at the knot or knot slippage. To test knot strength, assuming slippage does not occur, 3D scaled computational models of the 2DT and 3ST knots were created in SOLIDWORKS, and exported to a finite element analysis (FEA) software ABAQUS. The sutures were subjected to increasing static forces until the yield stress within the suture was achieved. Preliminary results suggest that the 3ST knot has a higher construction time and is more vulnerable to suture rupture when it fails at a value half that of what is required in a 2DT knot, but is more resistant to knot slippage. The 2DT surgical knot, while more vulnerable to slippage, appears to possess relative acceptable strength, with its yield only initiating at a force double of what is observed in a 3ST knot. Therefore, the 2DT knot may be more appropriate in cases where efficiency and resistance to suture rupture is prioritized due to the lower construction time and its higher load at yield. Conversely, where wound dehiscence via slippage carries a high risk, the 3ST that is more resistant to slippage is encouraged, despite the additional time required to construct.