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To make secure surgical knots on a consistent basis, surgeons must be aware of the variations in suture material they use. As you learned in the previous topic, there are numerous types of suture material available, and the composition of the suture has a direct impact on its handling during knot tying. Let us take a closer look at some common types of suture material and the number of throws required to create a secure knot.
Most multifilament suture materials should have three interlocking square knots, made with four squarely created throws. In actuality, only three throws are required for security. However, if one of the three throws is incorrectly formed, the knot could lose security. For this reason, most surgeons like to add an extra fourth throw for peace of mind.  
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Most multifilament suture materials should have a minimum of 4 squarely formed throws, or two separate square knots, to be considered secure.
When placing a continuous suture line, special consideration must be given to knot security. In a continuous suture pattern, a knot is placed at the beginning of the line and a knot at the end of the line (called the penultimate loop because the surgeon must create a doubled stranded “loop” to provide an opposite strand end for knotting). Thus, the security of an entire continuous suture line depends on only two square knots. If one of these crucial knots unravels, catastrophic failure of the line will occur with potentially life-threatening results. Therefore, when using continuous suture patterns on tough tissues under tension or on body wall closures, most surgeons recommend a minimum of 6 throws.
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Knots Made with Multifilament
Knots Made with Monofilament
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Knotting a Penultimate Loop
Tighten Third Throw
Tighten Fourth Throw (Square Knot 2)
First Throw
Fourth Throw
Second Throw (Square Knot 1)
Final Knot
Third Throw
Tighten Third Throw
Final Knot
Knot Stack
Begin
Additional Throws
First Throw
Second Throw Knot
Second Throw