Knot Security: How Many Throws Does It Really Take?

Abstract

The purpose of this study was to determine the minimum number of throws needed for knot security for square knots using 5 common suture materials and 3 common sizes by in vitro single load to failure biomechanical testing. The hypothesis was that each suture combination studied would share a common minimum of at least 5 throws to guarantee security. Five suture materials (FiberWire [Arthrex, Inc, Naples, Florida], Monosof, Surgipro, Maxon, and Polysorb [Covidien, Mansfield, Massachusetts]) with varying suture sizes (#5, #2, 0, 2-0, and 4-0) were tied in vitro, varying the number of square knot throws (3, 4, 5, and 6). Twenty knots for each combination were statically loaded to failure in tension; whether the knot failed by fracture or slippage and the tensile strength at knot failure was determined. For the tested materials, at least 5 flat square throws should be used to confer knot security based on a binomial proportion score 95% confidence interval (CI) 0.84 to 1.0 or at least 4 throws for a 95% CI of 0.76 to 0.99. FiberWire requires 6 flat square throws per knot for security at either 95% CI level. Unless a surgeon has specific knowledge of experimental evidence that fewer throws are necessary for a specific application, the default should be a minimum of 4 throws, with 5 conferring additional security in most situations, and FiberWire requiring 6 throws.

Comparison of tensile strength among simple interrupted, cruciate, intradermal, and subdermal suture patterns for incision closure in ex vivo canine skin specimens

“…5 In the present study, the number of throws (n = 5) applied to each knot was standardized in accordance with recommendations for continuous suture patterns given the type of suture material used provided in other studies. 12,13 Generally, the knots for most interrupted skin sutures are nonabsorbable and consist of only 3 to 4 throws. 14 The fact that all knots in the present study consisted of 5 throws might have inflated the time required to place the interrupted and cruciate patterns, compared with that typically required in clinical practice.…”

The Miller׳s knot as an alternative to the surgical knotting? Characterization of the mechanical behavior

“…blood vessels, muscles, tendons or ligaments) may show different biomechanical properties between individuals and for the same individual. Marturello et al (2014) and Tidwell et al (2012) have demonstrated that the knot security and tensile strength are directly conditioned by the number of throws added to the knot. Nevertheless, in the present study these factors were assessed in the main knot only, without any throws.…”

“…Overall, a medium or low strength is required to achieve complete closure of the knot, allowing correct tissue apposition or blood vessel hemostasis, without the knot being ruptured. Nevertheless, the strength should be increased on throws to ensure the knot is secure (Neuhofer et al, 2013;Tidwell et al, 2012). Furthermore, excessive force on the main knot could produce tear, rupture or local ischemia of the blood vessels or tissue, which would delay or prevent healing (Welch, 2007).…”

“…Although previously known, these are sometimes difficult to control. However, other factors such as the type of suture material and its characteristics, the suture pattern or the knot type used are also important and can be extensively characterized from their mechanical study (Marturello et al, 2014;Muffly et al, 2010;Tidwell et al, 2012).…”

Comparison of volume, security, and biomechanical strength of square and Aberdeen termination knots tied with 4–0 polyglyconate and used for termination of intradermal closures in canine cadavers

“…1,2 Surgeons pay particular attention to knot construction during surgery, given that holding strength of the completed knot is vital for appropriate closure. 4 However, 4 to 6 throws are recommended to create a consistently secure square knot, [5][6][7][8] and this produces a knot that can be bulky, particularly when large-size suture materials are used. 4 However, 4 to 6 throws are recommended to create a consistently secure square knot, [5][6][7][8] and this produces a knot that can be bulky, particularly when large-size suture materials are used.…”