Knot Tying

New instruments and implants are constantly being introduced to facilitate shoulder arthroscopy. However, there is no good substitute for the ability to tie an arthroscopic knot (Box 17-3). This skill adds flexibility to the surgeon's ability to address most shoulder pathology.

Knots can generally be divided into two broad types. These are sliding and nonsliding knots. Nonsliding knots can be referred to as locking knots. A third type of knot is the sliding locking knot. A surgeon should be able to tie at least one slid-

Box 17-3 Knot Tying

• Surgeon should know one sliding knot and one nonsliding knot.

• Sliding knots require a suture to slide through tissue and the suture anchor.

• After the initial locking knot, three half hitches with alternate posts back it up.

Figure 17-4 A skin bridge is maintained between the two anterior portals. (From Gartsman G: Shoulder Arthroscopy. Philadelphia, WB Saunders, 2003.)

ing and one nonsliding knot to successfully complete most procedures.

A sliding knot may only be thrown if the suture can slide through the tissue and anchor. This knot is used first to bring the repaired tissue in close apposition with the suture anchor or with other tissue. Locking knots prevent the sliding knot from sliding away from the tissue and losing tension of

Figure 17-5 Spinal needle used to localize the position of the lateral portal. (From Gartsman G: Shoulder Arthroscopy. Philadelphia, WB Saunders, 2003.)

the repair. We generally use a half hitch followed by square knots for most procedures.5 The sliding knots are reserved for occasions when we may be tying a knot blindly such as in a closure of a portal.

The first important premise in tying knots is understanding the concept of post and nonpost strands. When a half hitch is created, the two strands of suture may have one of three relationships. In the first two relationships, one suture is wrapped around the second suture (Fig. 17-7A). This is the most common event. The third relationship occurs when each suture is under the same tension and neither suture is wrapped around the other (see Fig. 17-7B). The first two events result in a half-hitch knot (see Fig. 17-7C). The last relationship results in a flat throw designated as half of a square knot (see Fig. 17-7D). If the two sutures are under unequal tension, the suture wrapped around the second suture is designated as the nonpost strand and the other suture is the post strand. The post strand is under more tension than the nonpost strand. The post strand may change at any point in passing the suture by simply altering the tension on each suture. The tension may be manipulated either by pulling on one strand with a hand or using the knot pusher. The post strand is not defined by which strand is manipulated by the knot pusher.

This concept is important because certain configurations of knots have been shown to be biomechanically superior and resist unraveling. Generally, it has been shown that once the tissue is apposed with an initial locking knot, three half hitches with alternate posts and directions of the throw are sufficient to prevent the knot from unraveling and maintaining tissue apposition.7,8

We prefer to place the knot pusher on the strand that comes directly from an anchor and does not pass through any tissue (Fig. 17-8A). The initial post strand is the second suture. Two half hitches are thrown sequentially in the same direction while maintaining tension on the post strand (see Fig. 17-8B). As tension is placed on the post strand, the two half hitches will

Figure 17-7 Rope and a practice board used to demonstrate knot tying concepts. A, Two strands under unequal tension. The knot pusher is on the post strand. B, Both strands under equal tension. C, Two half hitches in same direction posted on the white strand. This can slide down the post before it is locked.

Figure 17-7—Cont'd D, Strands under equal tension result in a square throw.

V.

not lock. However, if tension is lost on the post strand, the half hitches will prematurely lock, resulting in poor tissue apposition. Once the tissue is apposed, the knot pusher is pushed past the knot to equalize tension and lock the knot in place. Alternatively, a sliding or sliding locking knot may be used on the initial throw. Several of these knots have been published in the literature.8 This initial knot should be backed up with three more knots. These knots are thrown in alternate directions. Once thrown, the tension should be manipulated to either change post strands on each throw or to equalize the tension. Changing the tension results in a pattern of knots with alternating directions and posts. This is biomechanically sound. However, we prefer to alternate directions and equalize the tension to create sequential square knots (see Fig. 17-8C).

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