The surgical instrument tie is a foundational skill in many medical procedures, representing an efficient method for creating a secure, permanent suture closure. This technique is valuable for working deep within a surgical field or when suture ends are too short for a manual, two-handed tie. Utilizing instruments allows a practitioner to achieve a flat, strong knot quickly. The instrument tie is designed to create a square knot, the most reliable configuration for maintaining tissue approximation until healing is complete.
Essential Equipment and Setup
The primary tool for this technique is the needle holder, often referred to as a needle driver, which acts as an extension of the hand to control the suture material. A common and secure method for holding this instrument is the thumb and ring finger grip, where these two digits are inserted into the rings of the handle. The index finger rests near the instrument’s hinge to guide the tip, providing fine motor control and stability. This grip allows for the necessary wrist movements (supination and pronation) that drive the knot-tying action.
Before initiating the tie, the suture material must be managed properly, leaving a short end (tail) of approximately one to two inches at the wound site. Maintaining slight, consistent tension on the long end of the suture, held in the non-dominant hand, is important throughout the process. This tension prevents the first throw from loosening prematurely. The needle driver should be positioned centrally, directly over the incision or structure being ligated, creating a clear “V” shape with the two suture strands.
Executing the Basic Instrument Tie (The First Throw)
The first throw of a standard instrument-tied square knot begins by wrapping the long suture strand around the needle driver. The needle driver is placed horizontally between the two suture ends. The long strand is wrapped once over the top of the instrument, moving toward the side holding the short tail. This single wrap creates the foundational loop for the initial half-hitch.
After the single wrap is complete, the jaws of the needle driver are opened and used to grasp the short end of the suture material. This grasp should be firm and near the tip of the short tail to maximize the length of the suture available. With the short end secured, the needle driver is pulled back through the loop created by the wrap. As the instrument is drawn through, the long end of the suture, held in the non-dominant hand, is simultaneously pulled in the opposite direction.
This dual, opposing pull cinches the initial loop down against the tissue, forming the first half of the square knot. It is important to maintain even, horizontal tension on both strands to ensure the knot is laid down flat, which is required for a secure closure. Uneven or vertical pull can cause the knot to deform or slip entirely. The first throw temporarily secures the tissue edges and sets the stage for the throws that will lock the knot permanently.
Throughout this initial throw, the practitioner must avoid excessive friction or “sawing” of the suture material. Friction can compromise the structural integrity of the suture, especially monofilament materials, which are prone to damage. The goal is to slide the knot down gently and flatly until it achieves the desired tissue approximation. Tying the first throw too tightly can cause tissue strangulation, potentially leading to necrosis, so a balance of security and appropriate tension is necessary.
Securing the Knot and Introducing Variations
To complete the secure square knot, a second throw must be executed immediately after the first, utilizing a single wrap in the opposite direction. This second throw is performed by placing the needle driver over the suture strands and wrapping the long end once, mirroring the first throw but in reverse orientation. The instrument grasps the short end, which is pulled through the new loop to lay the throw down flatly, reversing the hand position from the previous throw. Alternating the direction of the throws “squares” the knot, ensuring the final configuration is stable and resistant to slippage.
Failing to alternate the wrap direction on the second throw results in a less secure granny knot, which is prone to loosening under tension. Once the second throw is correctly laid down, a third throw, using a single wrap and alternating direction, is commonly added for enhanced security. While a two-throw square knot is technically complete, adding a third or more throws is standard practice, particularly with monofilament sutures that have a lower coefficient of friction and require additional throws to resist unraveling.
A primary variation is the Surgeon’s Knot, employed in areas of high tissue tension or when using slippery suture materials. The key difference lies in the first throw, where the long end of the suture is wrapped twice around the needle driver instead of once. This double wrap significantly increases friction within the initial loop, preventing the first throw from loosening or slipping back while the second throw is prepared. Following this double-wrapped first throw, the knot is completed with subsequent single-wrap throws in alternating directions, just like the standard square knot, to ensure the final structure is secure and flat.