Knot security

The suture materials used were silk (Ethicon) Mersilene , uncoated polyester (Ethicon) Polydek , Teflon-impregnated polyester (Deknatel)  

9 Effect of number of throws on the knot holding force in the dry loop tests of Mersilene (M) and silk (S) sutures of sizes 1-0 to 4-0.  

10 Effect of the number of throws on knot holding force in the dry straight tests of three polyester sutures of size 2-0, all braided but finished differently. 

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Since the shock of a single strand of primacord is not powerful enough to detonate most explosives, a knot must be tied at the end to concentrate explosive force within the charge to be detonated. A properly tied knot, securely buried, is sufficient to detonate plastic explosives. 

A surgeon considers the following factors while choosing a suture (a) knot security, (b) tensile strength and its lifetime, (c) minimal tissue drag and inflammation, (d) handling, (e) size, (f) inhibition of infection, and (g) potential of allergenic reaction. 

The moisture regain of a typical sUk fiber is about 9.9% due to the high concentration of polar side groups in amino add residues. Water molecules absorbed by silk fibers would reside in the amorphous domains and compete with the amino adds in the amorphous chain segments for inter- and intramolecular interaction (Robson, 1985). SUk sutures also have very good handling properties with exceUent knot security. 

Key words knot security, knot strength, shppage, knot factors, role of friction, secure knot model, behavior in dynamic tests, knot and adhesive, knot and laser. 

Friction in sutures and friction-based hypothesis of knot security... 

Based on the finding that friction had played the primary role in governing knot security, a friction-based hypothesis of a secure knot can be proposed. A suture is looped around cut vessels or tissues, the ends pulled tightly together and tied with a knot. The tissues exert outward pressure on the loop tending to expand its size (Fig. 12.13) and as a result exert a tension... 

A knot is a weak place whose strength in general is only about 50-80% of the suture strength. The rupture usually occurs at a point just outside the knot. It is important, therefore, that during exposure, the laser beam only touches the area within the knot, not the portions outside it. This will be particularly important if greater heat than the threshold value was required to make the knot secure. 

Ideally, a knot should not only be secure but also small. One way to achieve this objective is to couple the energy from an auxiliary source with the restraint obtained from the mechanical interlacing of a small knot. In limited work involving thermal energy from a CO2 laser or chemical energy from a cyanoacrylate tissue adhesive, it has been shown that the KHF of a small (two- or three-throw) knot could be enhanced. While benefits were noted in most materials, in some they tended to be optimum. As knot security and strength continue to be very important parameters in sutures, further work using techniques such as these should be pursued. 

Gupta, B. S. and Postlethwait, R. W., An analysis of surgical knot security in sutures , in Biomaterials 1980 (Winter, Gibbons and Plenk, Eds), John Wiley and Sons, 1982,661-668. 

Herrman, J. B., Tensile strength and knot security of surgical suture materials . Am. Surg., 37,1971,209-217. 

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