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However, when tied, this knot typically has a cross-sectional area significantly larger than its accompanying needle tract. As a result, a surgeon may have difficulty burying the knot into the corneal stroma or limbal tissue. The force required to bury this knot may exceed the tensile strength of the suture, leading to suture breakage. Some alternatives, such as the “3-1”, the “2-1-1” square knot, the “1-1-1” slip knot, and “1-1-1-1” modified slip knot, have been used.
However, these knots tolerate significantly less tensile force. For instance, in one study, the modified slip knot tolerated 0.64 N before breakage and 0.37 N before slippage, whereas the surgeons knot tolerated 0.71 and 0.48 N, respectively.
Herein, we present an alternative technique for tying a 3-1-1 square knot, reducing its cross-sectional area while burying the knot, thus reducing the likelihood of suture breakage.
A 10-0 nylon suture is placed across the wound (Video 1). The first throw comprises 3 loops and may be adjusted to the desired tension (Fig. 1A,B). The second throw uses 1 loop in the opposite direction to the first throw. This creates a locking square knot (Fig. 1C,D). The knot is buried (Fig. 1C,D). The third and final throw is a single loop that is tied in the opposite direction to the second throw to lock the knot securely (Fig. 1E). The ends of the sutures are then trimmed using a 75-blade. The final step pulls the knot from its buried position but may be buried once again with relative ease (Fig. 1F).
In the traditional 3-throw, 3-1-1 technique, the initial loops limit the suture from slipping, permitting the appropriate tension to be maintained during the second and third throws, each of which secures the knot further. This ultimately results in a strong knot that is resistant to breakage and unravelling. However, this technique has its disadvantages, including appropriate tensioning and its large size, making it more difficult to bury.
Attention must be made to bury all corneal and limbal knots to reduce corneal irritation. For these reasons, smaller knots have been developed (e.g., 3-1, 2-1-1 square knots, the 1-1-1 slip knot, and 1-1-1-1 modified slip knot). Each of these techniques produces a smaller knot that requires less force when burying.
The slip knot and modified slip knot in particular offer the additional benefit of tension adjustment until after the third throw. The trade-off, however, is that these alternatives produce sutures with reduced tensile strength compared with the traditional 3-1-1 technique.
In the 3-1-bury-1 technique, the cross-sectional area of the knot is smaller after the second throw than that of the standard 3-1-1 knot. This reduced cross-sectional area allows the knot to be more easily rotated into the corneal stroma. This initial burying of the knot enlarges the suture needle tract. During the subsequent throw, the knot retracts from the corneal stroma but is easily rotated back into the previously widened path, thus minimizing the potential for suture breakage. Ultimately, this may limit the need to replace sutures, decrease operating time, and reduce associated complications.
Footnotes and Disclosure
Adam P Deveau: none; Mark E Seamone: none; Darrell R Lewis: none; R. Rishi Gupta: none.
Video 1. The video demonstrates the 3-1-bury-1 suturing technique. The video begins after the suture passed from cornea to sclera. Next, the first throw is made with tying forceps between the 2 ends of the suture with 3 loops made in the same manner as the traditional 3-1-1 technique. The short end of the suture line is then pulled through the loops in the opposite direction and the knot set to the desired tension. The second throw is made with a single loop and tightened to lock the knot. Using forceps, the knot is rotated and buried. The final throw is made with 1 loop. This will unbury the knot, which is then reburied.
Practice patterns of Canadian Ophthalmological Society members in cataract surgery: 2011 survey.