Page 27 - Arthroscopic Knot Tying: An Instruction Manual

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Post Switching

It is important to prevent the loop and the post limbs from becoming entangled during post switching
(Figs. 13 , 14 ). If a knot becomes twisted during the tying process the knot will not lie flat. When this
occurs, tension is not maintained within the knot and the knot can loosen and fail (Fig. 14C ). When post
switching, it is important to know which limb is the post and which limb is the loop at all times. Some
surgeons place a clamp at the distal end of the post to identify the post limb. Others use a two-hole knot
pusher to identify and prevent limb twisting. During post switching, if the surgeon transfers the limbs
between hands, it is important that the surgeon untwists the post and the loop limbs with the
arthroscopic knot-tying device while seating the knot. Limb twisting can also be avoided if the limbs are
not transferred between hands while post-switching. For example, if the surgeon is initially holding the
post limb in the left hand while tying half hitches with the loop limb in the right hand, upon post
switching the surgeon should use the right hand to hold the “new” post while throwing a half hitch with
the loop limb in the left hand.

FIGURE 13. A. Parallel loop and post limbs. B. Parallel loop and post limbs with a “flat” knot.

FIGURE 14. A. Twisted loop and post limbs. B. When tying a knot with twisted post and loop limbs,
the knot does not lie “flat.” C. The final knot configuration will loosen if the knot is tied when the
loop and post limbs are twisted.
Chan and Burkhart (8 ) described a technique in which the arthroscopic surgeon can switch the post limb
after each throw without having to rethread the arthroscopic knot pusher. This technique may increase
the speed of the knot-tying process and also help limit twisting of the suture limbs. One can “flip” a half
hitch by releasing tension on the post limb and pulling on the loop limb. When the post is switched, the
direction of the half hitch is also reversed. The authors of this technique report that it is easier to flip
half hitches using monofilament because it more readily converts to a flat knot, but it can also be done
with braided suture.