Tie the Constrictor Knot with Howard Instrument Method
Pass the suture twice around the vessel so that the second turn crosses over the first. Insert the forceps under the second turn. Twist the forceps around the standing end to create the half knot. Pick up the end with the forceps and draw it back through the knot. Tighten and cut the ends.
Constrictor Knot Tied Using Howard Method
Uses: The Constrictor Knot (ABOK # 1188, p 216.) is uniquely suitable for use as a surgical ligature: it has superior binding properties, tightening smoothly and holding tight. The Howard Instrument Technique may be the best way to facilitate tying it.
Options: Four ways of tying it in surgery are compared: Howard Instrument Tie; Retrieving the End; Tied Around the Forceps; and, Sliding the Constrictor Down the Forceps.
Research on the Constrictor Knot: Howard Taylor, a veterinary surgeon in Salisbury, England pioneered the use of the Constrictor knot to ligate the uterine pedicle in a canine hysterectomy and prefers his Instrument Technique. For our research we used a modification of his test bench to confirm that the Constrictor is the most secure ligature by a large margin because of its ability to stay tight1. Our paper has generated interest and, as a result, the Royal College of Surgeons has kindly made it Available On Line.
Disadvantages: The Constrictor requires two passes around the vessel or pedicle and the knot itself requires learning. This particular technique requires threading the forceps accurately to create the correct knot.
Advantages: The additional pass around the vessel enhances the constriction effect. In contrast to the double throw of the Surgical Half knot, the Constrictor tightens more readily and is less prone to slip. This particular technique quickly becomes a convenient instrument tie.
Undoing it: Undoing a ligature is not anticipated – which is fortunate because the knot can be very hard to undo - cutting the knot is often the only option. If this were necessary, the binding strand should be cut over the other constrictor strands to protect underlying tissue.
Reference: 1 Taylor H, Grogono AW. The constrictor knot is the best ligature. Ann R Coll Surg Engl. 2014 (96): 101-105.
