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In extracorporeal suturing, a long suture is required, with 75 cm (30 in.) the minimum and 90 cm (36 in.) being ideal in a large breed dog. A knot pusher is also required (Figure 2.22) The needle is introduced into the body cavity, while the end of the suture is secured outside the cannula. If the valves cannot hinder CO₂ leak with the suture in place, an introducer is necessary. Needle introduction, suture bite, and needle removal are performed as described in intracorporeal suturing. Importantly, the needle end of the suture is exteriorized through the same cannula as it was introduced through (Figure 2.21). When both ends of the suture are available at equal length, a slip knot is tied by hand. The knot is cinched down using a knot pusher (Figure 2.22), while the surgeon maintains tension on one or both ends of the suture, depending on knot type. Knot pushers are available with either a slotted (“open”) end or a closed end. The disadvantage with a slotted design is that they may disengage from the suture during cinching. Closed end designs need to be threaded onto the post suture, which can be a disadvantage.

The knot type used depends on the indication for using an extracorporeal knot. If paucity of intracorporeal space is the main reason, regular square throws can be tied extracorporeally, with each throw being cinched with a knot pusher while both suture ends are secured outside the body. These throws should be applied with proper one‐handed technique to avoid that identical half hitches are placed, resulting in granny knots. However, if a stronger starting knot is needed to overcome tension, a more complex slip knot is needed. With few exceptions, these slip knots need additional throws for security if they are to be placed in tissues under tension.

Figure 2.18 Knot tying in a vertical plane: the Rosser technique. (A). A suture bite is taken from right to left. (B). The left instrument is used as a “pulley” to gently pull the suture through, forming a C‐shaped loop in a vertical plane. A short tag, 2–3 cm, is left on the contralateral incision side. (C). The right instrument is positioned above the left and wrapping the suture close to the needle around the shaft of the left, in a clockwise direction, twice for a surgeon's throw. This is in contrast to open suturing in which the instrument often is rotated around the suture to form the throws. (D). Ensure 2 complete throws around the instrument. (E). The two instruments are moved together toward the loop end (the short tag). Make sure to not tighten the throws while moving (F). The two throws are slid off the left‐hand instrument before tension is applied to the two ends in order to not get stuck in the box lock. The most tension is applied on the needle end in order to not pull the loop end longer. If so, the tag will lengthen, which makes the remainder of the knot more challenging. (G). The right instrument is wrapping the suture material in a counter‐clockwise direction. (H). Tension is applied to both ends, and the right instrument path crosses over the left at this time. (I). The third and final single throw is wrapped in clockwise fashion. (J). Tension is applied, without crossing of instruments.

Figure 2.19 Clockwise and counter‐clockwise wrapping of suture. (A). Clockwise wrapping around the left instrument. (B). Counterclockwise wrapping around the right instrument.

Figure 2.20 Knot tying with horizontal C‐loops, as described by Szabo [14]. (A). A suture bite has been taken from right to left. The left instrument is used as a “pulley” to gently pull the suture through, forming a horizontal C‐shaped loop. (B). A horizontal C‐loop has been formed on the left side, and the left instrument is placed on top of the C‐loop close to the needle. (C). The right‐hand instrument has wrapped the suture twice around the shaft of the left instrument in a counter‐clockwise fashion. The two instruments move together to pick up the short loop end with the left instrument. (D). Tension is applied, with care taken to not pull hard on the short end and thus lengthen the tag. The tag should remain 2–3 cm throughout. (E). The left instrument picks up the needle and forms a reversed horizontal C‐shaped loop, and the right instrument is placed on top of the loop close to the needle end. (F). The suture is wrapped around the right instrument once in clockwise direction, the wraps are moved over the needle driver. (G). tension is applied to the suture bilaterally. Note that crossing of instrument paths is not occurring with this technique. (H). The third and final throw is applied similar to the first, but only a single throw is required, in counter‐clockwise direction. (I). Tension is applied.

Figure 2.21 (A). Extracorporeal suturing requires suture material to enter and exit the cavity through the same cannula. (B). A slip knot is tied extracorporeally. (C). A knot pusher is used to cinch the knot. (D). A slip‐knot is stronger than a double throw and can overcome more tension than an intracorporeally tied knot.

Figure 2.22 Extracorporeal knot tying requires the use of a knot pusher. (A). These can be of open type, as depicted here, ore closed‐and thus threaded onto the suture. (B). By advancing the knot pusher while applying tension on the suture end, the knot is cinched.

Complex slip knots do not accept any tension placed on the loop end while being cinched, and it is more practical to cinch them into the abdomen along the post end of the suture, with a short loop end, and the remainder of the throws are placed with intracorporeal technique.