SUTURES

In medical terminology, sutures are meant either a joint between the skull bones with typical irregular and finely serrated fusion lines or thread-like materials, that in surgery are used to hold tissue disruption, intentional or otherwise, together. There is an ambiguous similarity in the usage of the terms suture and stitching. However, it should be understood that stitching is the actual process of helping sutures to be used for binding two objects or a disrupted object together.

History tells us about the use of a similar process with the use of a binding object, either for making clothes or an expression of one’s creative self by simply sewing or embroidering art forms. From about 30,000-60,000 years B.C., surgical use of sutures was adopted just to hold or rather tie when possible, the outward visible tissues back to the previous physical form. Later, at around 3000 years B.C., physicians of that time realized that this expedited healing. Needles were there, as in other forms of sewing, made of bones earlier and metals later, to guide the thread through the tissue. Literature shows that even in the early times, eyed bone needles were available to guide the thread through material. Tissue joining, human or otherwise, did not need any extra skill. Threads like linen, bamboo and hemp fibres, leather strips, or cotton were at hand at that time and a sincere effort was made to keep the tissue in one piece by binding them together. The earliest known suture was described in the 15-foot-long Edwin Smith Papyrus. This, even in the early times, quoted “If thou findest that wound open and it’s stitching loose thou shouldst draw together for him the gash with two strips of linen”. Hair, tendons, muscle strips, arteries, and nerves have also been used. In the earliest times, the belief was acceptance of naturally available materials, as these were, and these were believed to be absorbed. Soon catgut, derived from sheep intestine became popular as the preferred suture material. Catgut was an incorrect and ungrammatically derived term. ‘Kitgut’ (a three-stringed German musical instrument where the strings were made from sheep intestinal serosa) was the actual word from which it was adopted. The fact that the strength of the thread remained till natural healing occurred and absorbed thereafter made these materials desirable. In history, we find that the oldest known suture is in a mummy from 1100 BC and around 500 B.C. The Indian sage and physician, Sushruta documented the use of ant heads with intact hook-like, curved spiny claws for holding the approximated tissue in place. The giant ant Eciton burchelli was used. Cleanliness, irrigation (with wine), and control of bleeding points with sutures available at that time were stressed.

Silk threads were used soon after. Threads are constructed from the commonly found silkworm Bombyx mori. The flexibility and thinness of the silk fibres and the fact they were naturally produced made them ideal for use in surgery. Also, the fact that thicker gauges could be created by simply gathering together and braiding individual fine strands.

Use of drawn, twisted, and similarly naturally produced threads from animal intestines followed. These had the added advantage of being absorbable after the healing is complete. Later studies showed 'catgut' to be collagen, which is bountiful in the body and nature.

Obviously, during the early times, there was a preference for naturally available products, and most often biological materials were sought after. Human nature and intellect made one realize the importance of cleanliness in handling open gashes and wounds. The first written document on this subject can be found in the writings of Sushruta. His ‘Samhita’ not only tells us about sutures with threads but also is revered for the innovative methods of dealing with amputations, anal fistulas, and the Indian method of rhinoplasty. The last is still a talking point in the parlours of plastic surgery. This was 500 years B.C. and in different countries or regions, around the same period, Hippocrates, Galen, and Celsus (who were considered the inspirational demigods of modern medicine) were of a similar opinion. Cornelius Celsus was a pioneer and he introduced the concept of braided sutures. He was also responsible for the terms calor, rubor, tumour, and dolor. Cleanliness, irrigation (with wine), and control of bleeding points with multiple suture ligatures, by twisting the thread, used for a knot, was suggested by Galen.

It was understood that surgery was an integral part of the treatment process. During the early times, it was a usual practice to adhere to the problems of temperature, pus, bleeding, and pain. There was not much development from the Hippocratic times (and principles) to the time of the Industrial Revolution, and healers could not overcome the problems of bleeding and pain. During this period, the only reference to surgery, parallel to which sutures were developed was by Ambroise Pare, a 16th-century French physician. Surgery, he stated, is “To eliminate that which is superfluous, restore that which has been dislocated, separate that which has been united, join that which has been divided and repair the defects of nature."

Another interesting aspect is the knots. Most of the time common sense was applied and the intricate sailor knot was avoided. Simple knotting techniques were employed. The only exception was that a reef knot or square knot was employed most of the time just to make sure that accidental loosening or untying did not happen. The suture material imbibes the surrounding water and the knot will have a natural tendency to become loose. This was borne in mind constantly, and the memory of the thread, whether it tended to revert to the packaged configuration, had to be taken into account. The number of knots increased when the memory was apparent. Whether the knot was made with hand, fingers or instruments, was immaterial.

Marion Sims, a pioneer in gynaecological surgery, is credited with the introduction of thin stainless steel wires as suture material. This material was unabsorbable and incited the least tissue reaction.

The introduction of polyethene, polypropylene, other polyesters, poly-galactones, and poly-caprones is recent. These are industrial research products and each has a claim of uniqueness and superiority over similar products. One should remember that the choice of the suture is surgeon-oriented and following a time-tested material is always the norm.

Sutures may be natural or synthetic. Again they may be absorbable or non-absorbable and an algorithm helps in understanding sutures used in surgery today ------

BIOLOGICAL/NATURAL SYNTHETIC

ABSORBABLE NON-ABSORBABLE

catgut

cotton

linen

stainless steel wires

nylon or polyamide

poly-ethylene

polypropylene

hexafluropolypropylene

poly-ester

poly-tetrafluroethylene (PTFE)

SYNTHETIC ABSORBABLE

poly-galactones -- irradiated and non-irradiated forms

poly-glecaprones

poly-dioxanones

copolymers of polyglyconates

Sutures can again be monofilament or braided. Braiding of basically monofilament suture materials strengthens the product. However, these are notorious for harbouring microbial spores, which may multiply and become virulent in the right atmosphere. The choice of the right suture material for a particular type of tissue is always a difficult proposition, but the use of strong non-absorbable material can be done in all situations provided reaction and fibrosis are less and biological acceptance is there. Absorbable materials are weak and have specific indications for specific tissues and methods. It is important to know the method of absorption of sutures and the degree of fibrosis a suture causes. Ideally, a suture should be least reactive and absorbed. There should be no residual weakness or effect attributable to the suture. Hydrolytic disintegration appears to be the usual method of assimilation of suture materials into the body. Residual fibrosis occurs in the healed tissue. Knowledge of the tensile strength of the absorbable material and the period after which it starts losing strength is important.

The naturally available collagen sutures, catgut, and fascial strips are notorious for the fact that they incite a stronger fibrotic reaction and chromicisation increases its strength. They have been mostly replaced by the recently available absorbable synthetic materials. The commonest question asked is 'How long is the strength retained?' and this is answered by the fact that, unless something untoward incident like an infection occurs, assimilation into the body starts by the time the least strong and fastest suture material loses tensile strength.

The following are the desired characteristics of a surgical suture:--

The non-absorbable sutures remain lifelong. These are used in situations where the surgeon is unsure of the strength of the underlying tissue, a durable repair, joining dead tissue and the skin. Only after a long time, phagocytic macrophage action and skip granulomas showing inclusion bodies resembling the suture used may be seen.

Knots are important and help in holding the tissue together with sutures. Knots also affect the tensile strength, e.g. --

Lastly, one should employ common sense and never veer from basic scientific foundations when selecting a suture for a particular tissue and function.