Surgical Ligatures and Sutures

SURGICAL LIGATURES AND SUTURES

The use of strands of material to tie off blood or other vessels (ligature) and to stitch wounds (suture) is an essential part of surgery. Both absorbable and nonabsorbable materials are available for this purpose.

A)    Sterilized Surgical Catgut

This consists of absorbable strands of collagen derived from mammalian tissue, particularly (despite its name) the intestines of sheep. Because of its source, it is particularly prone to bacterial contamination, and even anaerobic spores may be found in such material. Sterilization is therefore a particularly difficult process. As collagen is converted to gelatin when exposed to moist heat, autoclaving cannot be used. The official method is to pack the ‘plain’ catgut strands (up to 350 cm in length) on a metal spindle in a glass or other suitable container with a tubing fluid, the purpose of which is to maintain both flexibility and tensile strength after sterilization. Probably the most suitable method is to expose the material to gamma radiation. There is minimal loss of tensile strength and the container can be overwrapped before sterilization to provide a sterile container surface for opening aseptically. The alternative method involves placing the coiled suture immersed in a tubing fluid (commonly 95% ethyl alcohol with or without 0.002% w/v phenylmercuric nitrate) and storing for sufficient time to ensure sterilization. The outer surface of the vial must be sterilized before opening to avoid contamination of the suture when removed. Therefore the vial is immersed in 1% w/v formaldehyde in ethanol before use. It cannot be heated. A non-official method of sterilization is to immerse the catgut in a nonaqueous solvent (naphthalene or toluene) and heat at 160 °C for 2 hours. The catgut becomes hard and brittle during the process, and is aseptically transferred to an aqueous tubing fluid to restore its flexibility and tensile strength.

Catgut is packed in single threads up to 350 cm in length of various thicknesses related to tensile strength in single-use glass or plastic containers that cannot be resealed after use. Any remaining material should be discarded. Hardened catgut is prepared by treating strands with certain agents to prolong resistance to digestion. If hardened with chromium compounds, the material is known as chromicized catgut.

B)   Non-Absorbable Types

Sutures and ligatures are also made from many materials not absorbed by the body tissues. These consist of uniform strands of metal or organic material that will not cause any tissue reactions and are capable of being sterilized. Depending on the physical stability of each material, they are preferably sterilized by autoclaving or gamma radiation. They are packed in single-dose sachets, either dry or surrounded by a preserving fluid with or without a bactericide. The different materials are described in the British Pharmacopoeia (2010); they include linen (adversely affected by gamma rays), nylon (either monofilament or plaited), silk and polypropylene.