Page 14 - Arthroscopic Knot Tying: An Instruction Manual

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FIGURE 6. Square knot configuration.

Sliding knots, like the Duncan loop (27 ), are useful in opposing tissue under tension. While tying a sliding
knot, the post strand is held under tension while the loop strand is tied around it. Because the post strand
is not incorporated into the structure of the knot, the knot, once tied, can easily move down the post
resulting in a sliding knot instead of a flat knot such as the square knot. Tension is applied to the post
limb while using the knot pusher on the post to push the knot configuration down to the tissue. Once the
sliding knots are seated, they are often locked with a series of half hitches. Some sliding knots
preferentially slide in only one direction. These sliding knots are referred to as ratchet knots because
they easily slide down the post, but resist loosening once the knot configuration is pushed into place.

A locking knot is a modification of a sliding knot. A simple sliding knot can loosen before a series of half
hitches are thrown to “lock” the sliding knot in place. Thus, locking knots (also known as flip knots) have
been developed to maintain initial loop security that does not loosen when tension is removed (19 ). Once
this variety of sliding knot is properly placed and the tissue is tensioned, applying appropriate tension to
the loop limb causes the knot configuration to change. The post strand “flips,” converting the loop strand
into the new post strand and locking the knot into place. An example of a locking knot is the SMC knot
(19 ). Some authors suggest that locking knots do not need to be supplemented with a series of half
hitches. This may be advantageous by reducing the amount of inflammatory reaction of the local tissues
due to the smaller volume of suture material. However, the authors of this manual have found locking
knots without reinforcing half hitches to be inferior in tensile strength to knots reinforced with three
reversed half hitches on alternating posts (unpublished data).

Locking and sliding knots can be advanced into the joint just by pulling on the post. This can cause
tension at the repair site, which can damage the tissue being apposed. Tension at the repair site can be
minimized by pushing the knot ahead with the knot pusher while simultaneously pulling on the post limb.