Suture knot security

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. 

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. 

Although coating of suture materials facilitates easy passage through tissue, it frequently results in poor knot security. For example, Dexon Plus and coated Vicryl require four or hve square throws to form secure knots, while the uncoated Dexon and Vicryl sutures form secure knots with only two throws (1 = 1) (Rodeheaver et ah, 1981, 1983). Water-soluble coating materials like poloxamer 188, found on Dexon Plus, do not suffer from the adverse effects of water-insoluble coating materials on knot security. 

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