Principles of Aseptic Rodent Survival Surgery: General Training in Rodent Survival Surgery - Part II
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Simple Suture Patterns for Rodent Surgery [1]
If you are inexperienced with suturing techniques, reviewing this unit with some practice suture and instruments in hand will be helpful. Practice models, such as the "home-made" ones shown in Fig. 1, work well to simulate the look and feel of suturing.
Figure 1. Practice models for suturing.
Instrument Square Knot
For most incisions, an instrument square knot can be used. To begin suturing, the needle is passed through the far edge of the tissue first and then the near edge. The needle holder is placed between the far or tail end of the suture, shown as blue, and the near or needle end of the suture, shown as white. A loop is formed around the needle holder in the near strand. The far or tail end of the suture is grasped in the needle holder. The needle holder remains parallel to the incision while the throw is placed (Video 1).
Video 1 - 1.3 Mo - Initial placement of the needle holder and first throw of the square knot. To view video click on icon
The left hand shown wearing a blue glove and the right hand shown wearing a cream glove are reversed in position so that the tail is now on the opposite side. Even tension is applied as the throw is tightened just enough to appose the skin edges (Video 2). Over-tightening can result in excessive swelling of the wound edge. A half-hitch will result if hands are not reversed (Video 3). Avoid making the tail too long and do not grasp the suture at the base of the tail. This will not allow completion of the knot (Video 4). Care should also be taken to keep the ends of the suture on the sterile surgical field to avoid contamination.
Video 2 - 1.8 Mo - Tightening the first throw of the square knot. To view video click on icon
Video 3 - 0.6 Mo - A single half hitch. To view video click on icon
Video 4 - 2 Mo - Mistakes to avoid: making the tail too long and/or grasping the base of the suture. To view video click on icon
To begin the second throw a loop is formed with the needle end of the suture. Grasp the tail end of the suture with the needle holder (Video 5). The strands are tightened under even tension as they are held close to the incision (Video 6). A correct square knot will have a small space between the first and second throws to allow for tissue swelling (Fig. 2). Placement of the needle holder between the two strands for one throw and exterior to them for the second throw will result in a granny knot (Video 7). Failure to take the tail end to the opposite side for each throw will result in a double half-hitch that can easily slip and result in failure of wound closure (Video 8).
Video 5 - 0.5 Mo - Beginning the second throw. To view video click on icon
Video 6 - 0.9 Mo - Tightening the second throw. To view video click on icon
Figure 2. A correct single square knot.
Video 7 - 0.9 Mo - A granny knot. To view video click on icon
Video 8 - 0.5 Mo - A double half hitch. To view video click on icon
Begin the third throw by placing a loop from the needle end around the needle holder and grasping the tail to take it to the opposite side. To complete the knot, the needle holder crosses the incision to the opposite side (Video 9). It is important to remember to apply even tension while tightening the knot and to keep the needle holder parallel to the incision while the throw is being placed. A fourth throw is made in the same manner as for previous throws. This will complete the double square knot (Video 10). Cutting the ends of the suture too close to the knot or failing to place the correct number of throws may cause the knot to unravel.
Video 9 - 1.8 Mo - The third throw of a square knot. To view video click on icon
Video 10 - 1.3 Mo - Completing the double square knot. To view video click on icon
Instrument Surgeon’s Knot
For incisions under tension, an instrument surgeon’s knot can be used. The instrument surgeon’s knot is tied in much the same fashion as the instrument square knot, but a double loop is placed around the needle holder for the first throw. The tail end is grasped in the needle holder. The hands are crossed and even tension is applied (Video 11). This knot, when tightened, will not slip as readily as the square knot.
Video 11 - 1.8 Mo - Beginning the instrument surgeon’s knot. To view video click on icon
The second loop is made in the same manner as the square knot. A single loop is made around the needle holder, which is always placed between the two strands (Video 12). The knot is completed by placing one to two more single loop throws (Fig. 3).
Video 12 - 1.3 Mo - The second throw of the surgeon’s knot. To view video click on icon
Figure 3. Completing the surgeon’s knot.
1. Knecht CD, Algernon RA, Williams DJ, et al, eds. Fundamental Techniques in Veterinary Surgery, 3rd Edition. 1987. Philadelphia: WB Saunders Co, 1987; 44-47. - Available from amazon.com -
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Affiliation of the authors at the time of publication
1Office of Animal Care and Use, Office of Intramural Research, National Institutes of Health, Bethesda, MD, USA.2National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.
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