Tightening and Knotting

Tying the Knot

Like the bolts that fasten steel beams framing a skyscraper, knots bind and hold tissues, begin and end each suture line, and secure the effort expended in an anastomosis. Knots can be tied with fluidity and a flourish, or with flailing and frustration. Just as the bite was broken down into a four-step cycle that repeats in a suturing rhythm, the knot can be broken down into a four-step cycle that repeats in a tying rhythm: tail length, loop length, wrap, and grasp (Table 11.1).

The cycle begins by setting the “tail length” because a short tail makes knotting much easier. After the bite, the suture is pulled steadily through the wall, with the microforceps holding the suture down near its exit site and acting as a pulley to keep it from cutting into the arterial wall (Fig. 11.1A). The free end of suture must be spotted before it passes through the suture line, either by lowering the microscope’s magnification or preferably by staying at high zoom and watching for the wagging tail as it lurches side to side approaching the suture line. The pull is slowed until only a 2- to 3-mm tail remains; a shorter tail risks losing the stitch if the suture slips through the wall, and a longer tail leaves excess that must be chased with the microforceps or might create “double loops” in the tail when tying the knot. Once the tail length is set, the needle is parked on the stage within the field of view for a quick reload after the knotting.

The “loop length” is the length of suture that will form the loop of the knot, equal to three times the length of the tail, or approximately 1 cm (Fig. 11.1B). Grasping the long end with a microforceps in the dominant hand, or what was the driver hand, sets the loop length. With this grasp, the long end is brought back around to the tail on the side of the needle’s entry site, creating an open loop that opens toward the entry side (Fig. 11.1C). A tying forceps in the other hand hovers inside the loop right above the tail to shorten its travel to the tail later when grasping to complete the knot. Positioning the tying forceps at this spot centers the knotting optimally.

Now, the “wrap” is a full revolution of suture around the tips of the tying forceps made with microforceps in the dominant hand (Fig. 11.1D,E). Alternatively, the tying forceps in the nondominant hand can loop around the suture while the microforceps in the other hand stabilizes the suture, resulting in the exact same wrap of suture. More often, looping is a combination of wrapping suture and looping the tying forceps. One wrap is used for a standard knot, and two for a surgeon’s knot. The wrap of suture is kept from sliding off of the tying forceps by touching the tips of the microforceps to the shaft of the tying forceps, or by pulling the wrap up the shaft of the tying forceps slightly.

Finally, the tying forceps reaches out (Fig. 11.2A) and grasps the end of the tail (Fig. 11.2B) in order to pull it through the wrapped loop. A properly positioned tying forceps that hovers over the tail throughout only requires a short advance into the suture loop and an easy grab, but an errant tying forceps must chase the tail and fumble for a grasp. Short tails are more likely to stand upright, whereas long tails stick to tissues, hide, or get flattened by the surface tension of irrigant. A tail that keeps sticking to tissues or hiding can be bent with both forceps into a kink that can be grabbed easily. With the tail in its grasp, the tying forceps retracts through the suture loop, and the long and short ends are drawn tightly to throw down the first half-knot (Fig. 11.2C). The first throw is an easy pull to the sides with uncrossed instruments, snugging the tissues without burying suture in the walls. The grasping step is really two actions that grasp and pull, but they occur naturally together.

The tail should be grasped at its end, not its middle. Grasping the middle and pulling the tail through the wrap creates the dreaded “double loop” (Fig. 11.2D,E), which is an extra loop in the tail that gets tied into the knot, confuses the tail, and makes it more difficult to grasp during subsequent throws. Corrective efforts to tease out the double loop and free the end delay the throw and interrupt the rhythm.

The second half-knot is made with another four-step cycle, but with the same hold on the suture with the microforceps, without releasing the suture. Therefore, the first two steps of the second knotting cycle (tail length and loop length) are already done, and we progress to the third step (the wrap). Another open loop of suture is made, this time facing the opposite direction with the loop opening toward the exit side (Fig. 11.3A). After the first throw, the tail relocates to this exit side and when the long end is brought around to the tail, the suture often doubles back on itself to form an S-curve instead of the simple line of the first half-knot. This S-curve folds nicely on itself to form the loop, either by dragging the suture over the tying forceps or by turning the hand from pronation to supination (Fig. 11.3B). Then, with a wrap of the suture or loop of the tying forceps, the suture is wrapped around the tying forceps (Fig. 11.3C) to form the half-knot’s loop. This wrapping in the second half-knot is different from the simple spiral formation in the first half-knot, and leads some surgeons to transfer the long end of the suture to the other hand and reorient the loops for the second half-knot. This extra transfer step is less efficient and not usually used.