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Ophthalmology Emphasizing Corneal and Refractive Issues

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Slip Knot Technique

The slip knot (figure A) is an invaluable technique in providing a small knot which is easier to bury and holds against pressure. Elastic monofilament suture such as 10-0 nylon is ideal to tighten a slipknot as it’s smooth regular surface does not have the tendency to bind during adjustment. Once the desired tension is achieved, the knot is simply tied off with two overhand throws.

There are several methods used to form the slipknot. The method used depends on the the orientation of the long end (with needle) and the short end of the suture (figure B). The slip knot has been previously described by Charleaux and Terry but their techniques were cumbersome and sometimes  resulted in premature locking of the knot. Three methods of tying the knot are described but the long and short ends described can be re-arranged if desired to tie the knot in the most comfortable tie for the surgeon.

The simplified slip knot is used when the short end is to the right of the long end (with the needle). In the figure to the right this often occurs on the left side of a cornea transplant but can be arranged in any surgery. Using the instrument in the left hand, go under the long end to grasp the short end and pull it under the long end forming a loop. Using the instrument in the right hand  enter the loop and sweep right allowing the tip of the instrument to be exposed outside the loop. Bring the short end in the left hand to the tip of the right instrument and grasp with the right instrument. Pull the right instrument out to form the slipknot. Note that pulling on the short end will loosen the knot and pulling on the long end will tighten. Click  here or on figure C to the right to see the complete set of figures to illustrate tying this knot.

The single slip knot is used when the short end is to the left of the long end (with the needle). Grasp the short end with the left forceps and bring the right forceps under the long end and over the short end. Sweep the right forceps to the right carrying the short end under the long end and creating a loop to the right of the long end. Bring the left instrument (holding the end of the short end) over the top and transfer the short end to the tip of the right hand forceps (outside the loop). Pull the right instrument out to form the slipknot. These descriptions my seem intimidating but a review of the figures combined with re-reading of the text and a little practice will make tying these throws second nature. Click here or on figure D to the right to see the complete set of figures.

The final technique is used when the ends are twisted together. Grasp the short end with the left forceps and sweep to the right under both ends with the right forceps. Bring the short end grasped with the left forceps over the top and transfer to the tip of the right forceps. Pull the right instrument out to complete the slipknot. Note that this technique makes it a little harder to find the long end which can be grasped with the left forceps to stabilize as the right forceps is pulled out to complete the slipknot. Click here or on figure E to the right to see the complete set of figures.

    

Click on any of the figures above to see the complete set of figures associated with the slipknot

Simplified
Single
Twisted
A
B
C
D
E