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In this topic, we will examine a number of important terms utilized to teach knot-tying techniques.  Understanding these terms is the first step in learning to tie secure surgical knots. Let us take a minute to learn these important terms.

Suture Strands (2 of 3) Suture strands with needles have three main components. The junction where a needle is fused to the suture strand is termed the “swage”. The portion of the strand opposite the end connected to the needle is called the “free” or working strand. The portion of the strand on the end connected to the needle is termed the “fixed” or nonworking strand

Free Strand

Suture Strands EndFragment

Swage

Fixed Strand

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In this topic, we will examine a number of important terms utilized to teach knot-tying techniques. Understanding these terms is the first step in learning to tie secure surgical knots. Let us take a minute to learn these important terms.

Throws & Knots

Suture Loop

Square Knot

Knot Ears

Intrinsic Suture Tension

Suture strand with an attached needle. EndFragment

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Suture strand without an attached needle, also known as a free tie.EndFragment    

Suture Strands (1 of 3) There are two basic types of sutures available to surgeons, those with needles attached to a suture strand and those without needles. A suture without a needle is often called a “free tie”. Free ties are useful when ligating vessels and pedicles. Sutures with needles are frequently used when the surgeon must bring the edges of tissue into apposition or during the placement of “stay” sutures to hold tissue in position during surgery.

Suture Strands (3 of 3) It is important to understand these terms, because proper suture strand set-up is crucial to safe and consistent knot creation. When a knot is placed, the free/working end (without the needle), rather than the fixed/nonworking end (with a needle), is drawn through the suture loop. If possible, the fixed or nonworking strand connected to the needle should not be pulled through the loop when creating a throw, since this action can inflict injury to the surgeon or the patient.

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Free end

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Throws & Knots “Throw” is a term used to describe a complete twist of the two opposing strands of suture. A completed throw forms an enclosed loop. A completed “knot” usually consists of at least two tight throws, laid one on top of the other in a specific configuration.

Starting Position

First Throw

Completed Knot

Second Throw

Suture Loop A “suture loop” is the part of the stitch or ligature that contains tissue. The suture loop, completed by the knot, maintains approximation of divided wound edges or provides occlusion of a vascular structure. The orientation of the suture loop is important to understand, particularly when applying tension to the two strands to complete a knot. Ideally, for most knots performed in surgery, the surgeon pulls the strands in opposite directions and in-line or parallel with the orientation of the suture loop. 

Click or tap the video icon to view a demonstration of this technique.

Video example of the first throw, demonstrating tensioning and orientation of suture loop.

Square Knot A “square knot” is the most commonly used knot in surgery because it is one of the least complex and most secure knots a surgeon can make. On the first throw of a square knot, the surgeon is merely twisting one strand of suture around the other, with the suture ends exiting in opposite directions of the loop. On the next throw, the surgeon reverses the cross of the strands, with the suture ends positioned in the opposite direction, to create the square knot.   It is important to understand that minor technical changes during the process of knot tying can transform a secure square knot into a less secure variation of the square knot. 

Square Knot (1 of 3)A “square knot” is the most commonly used knot in surgery because it is one of the least complex and most secure knots a surgeon can make. On the first throw of a square knot, the surgeon is merely twisting one strand of suture around the other, with the suture ends exiting in opposite directions of the loop. On the next throw, the surgeon reverses the cross of the strands, with the suture ends positioned in the opposite direction, to create the square knot.   It is important to understand that minor technical changes during the process of knot tying can transform a secure square knot into a less secure variation of the square knot. Next you’ll learn about two common variations in square knots that novice surgeons sometimes make when trying to tie a knot. 

This video demonstrates the procedure of creating a square knot.

Knot Ear When a knot is completed, the suture ends are cut with scissors, creating what is referred to as “knot ears”. The length of the knot ear is an important factor in secure knot creation. Ears that are cut too short tend to unravel. However, ears that are left too long tend to induce tissue reaction. The term “stiff ears” is sometimes used to describe knot ears that produce significant friction-induced inflammation, as the loose tissue moves across the ends of the prickly knot. Stiff ears are a function the type of suture, its gauge, and the length of the ears. The surgeon must keep these factors in mind when deciding what length to cut the knot ears.

Knot ears cut to 3 mm in length to minimize tissue irritation. 

Knot  ears

The surgeon applies ample suture tension  in order to crush the tissue to achieve hemostasis.

Intrinsic Suture Tension (1 of 3) A stitch is created when a bite of tissue is taken with a needle though one side of a wound to the other, and the loop is tightened to appose the cut edges. A ligature is when suture material is passed around a structure to provide occlusion or intentional crushing of the structure. The amount of tension created in the tissue gathered within this loop is termed the “intrinsic suture tension”. 

Intrinsic Suture Tension (2 of 3) The intrinsic suture tension will vary depending on the needs of the surgeon. For example, a ligature designed to crush down a spermatic cord to achieve hemostasis during castration should have high intrinsic suture tension to prevent blood leakage. 

Click or tap the video icon to view a demonstration.

This video demonstrates the use of high intrinsic suture tension on a spermatic cord.

Intrinsic Suture Tension (2 of 3) The intrinsic suture tension will vary depending on the needs of the surgeon. For example, a ligature designed to crush down an ovarian pedicle to achieve hemostasis during ovariohysterectomy should have high intrinsic suture tension to prevent blood leakage. 

Intrinsic Suture Tension (3 of 3) Sutures designed to gently appose skin or delicate viscera have relatively low intrinsic suture tension. It is important to understand that it is the surgeon’s knot tying technique that ultimately dictates the intrinsic suture tension within the suture loop required to appose tissue edges or control bleeding in a vascular pedicle. 

This video demonstrates the use of a low intrinsic suture tension on a skin closure.