Arthroscopic Knot-Tying Techniques

Fig. 5.1

Post limb (black thread) and loop limb (red thread)

Interference: The relationship between the loops of the knot and the loops of the post limb. This is a parameter showing the strength of the knot. A knot made with opposite loops and changing the post limb in sequence has the property of the best interference.

Symbols: When stating the knot in international terminology, the number of wraps included in the loop and the sequence of parallel or opposite loops are taken as the basis. With the number of wraps, parallel loops are stated as ‘=’ and opposite loops as ‘×’. In sliding knots, for each loop, the letter ‘S’ is used instead of a number. If the fixed limb is changed, the ‘//’ sign is used (Table 5.1 and Fig. 5.2).

Table 5.1

Knots symbols

	Symbol
Examples of open non-sliding knots
Granny knot	1×1
Square knot	1=1
Surgeon knot	2=1
Examples of sliding knots
Post limb and loops are the same	S=S
The same post limb and different loops	S×S
Different post limbs and the same loops	S//S
Different post limbs and different loops	S//×S

Fig. 5.2

Granny (a), square (b) and surgeon knot (c)

Granny knot and square knot are formed from two consecutive loops with single wraps. The basic difference differentiating the two is that the sequence of loops is not opposite. In a surgeon knot, a double-wrapped loop follows a single-wrapped loop which is not opposite. The numbers included in the sequence of loops state the number of wraps. The signs between the numbers state whether the loops are opposite or not. In sliding knots, the letter ‘S’ is used instead of numbers. The other signs are the same. If the post limb is changed, this is indicated with the sign, ‘//’.

In a square knot (1=1), rather than applying equal tension to both limbs, if tension is applied to only one limb, it becomes a sliding knot formed of an overhand and underhand half hitch loop (S×S). The reverse is also possible; in other words a sliding knot formed of an overhand and underhand half hitch loop can be changed to a square knot by applying tension to both limbs (Fig. 5.3).

Fig. 5.3

Transforming a square knot (a) to a sliding knot (b)

Post flipping can be performed in two ways. The post limb is loosened by tightening the loop limb, and the post limb can be changed when it is felt that the loop limb has passed over. To facilitate the passing over of the loop, the post limb can be oriented towards the front of the loop when applying this procedure. With this passing over, an overhand half hitch loop becomes an underhand half hitch loop. In other words, with the changing of the limbs, the loops also change. The post flipping procedure can be made easily by first choosing the post limb before the loop is prepared. In all knot configurations, the most important step which provides knot security is the stage of changing the post limb.

Knot security is stated as the resistance of a knot to sliding. Friction and interference play important roles in knot security.

Friction: This is the resistance shown by the suture thread when the knot is formed. Therefore, the suture material used is the basic determinant of friction. In monofilament thread, friction is low, the risk of tissue damage is low, but it is difficult to manipulate, and there is a greater risk of gaps between loops, which cause loosening. Another two reasons for gaps between loops are crossing the limbs over each other and pastpoint (constriction by passing a newly made loop over a previously settled loop). Braided multifilament threads have high friction and a high risk of tissue damage but can be easily manipulated and form tight knots.

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