Current status of sutures
Since the 1950s, many scholars and experts in surgery and chemical engineering have worked together to create many synthetic sutures to meet the clinical needs of surgical procedures. There are synthetic non-absorbable sutures such as Nylon, Polyester, and Polypropylene, as well as synthetic absorbable sutures such as polyglycolic acid (PGA) and polyglycolic lactic acid (PGLA).
Most surgeons have a basic “suture routine”, a preference for using a particular suture material unless the situation requires otherwise, and by using the same suture material repeatedly, they become more skillful and agile. Therefore, a surgeon’s in-depth knowledge of the physical properties of various sutures is essential.
The ideal suture
The ideal suture material for clinical application should meet the following conditions: universal, sterile, non-electrolytic, non-surface tension, non-allergenic and non-carcinogenic, easy to handle, not conducive to bacterial growth, securely knotted without abrasion or cutting, resistant to contraction within the tissue, and absorbed by the tissue with minimal reaction after the purpose of the suture has been achieved. However, the ideal universal suture does not yet exist, so surgeons need to select and apply it when appropriate.
Introduction to the application of mainstream sutures
- Absorbable PGA thread (polyglactin 910, polyglactin 910) sutures meet the requirements for smoother synthetic absorbable sutures. After 14 days of suturing, the tensile strength of the suture is retained at about 75%, and the suture is hardly absorbed within 40 days, and after 60 to 90 days the suture is basically absorbed out. The surface coating is polyglycolic lactic acid 370 and calcium stearate coating treated sutures are more fluent, with smooth knotting and accurate positioning, which can reduce the degree of tissue cutting, and these sutures can also be used for suturing infected wounds. The coating also includes a high purity triclosan compound to form a three-dimensional antibacterial zone, which can effectively inhibit the growth of bacteria such as Staphylococcus aureus, Staphylococcus epidermidis, drug-resistant Staphylococcus aureus, drug-resistant Staphylococcus epidermidis, and Escherichia coli.
- PDSII single-stranded fiber suture, with high tensile strength and long tension maintenance time, can retain about 80% of tensile strength 14 days after suturing, and the suture is almost not absorbed within 90 days after surgery, so it has a wide range of applications. Since bile, pancreatic fluid and intestinal fluid are strong alkaline liquids, they have significant degradation effect on polyglycolic acid and polyglycolic lactic acid sutures, but have almost no effect on the degradation of PDS sutures, so PDSII sutures are especially suitable for lumen with alkaline digestive fluid, such as biliary-intestinal anastomosis and pancreatic-intestinal anastomosis, etc.
- The raw material of silk thread is the continuous protein silk produced by silkworms, which is animal protein, and the medical silk thread is a multi-strand suture woven or woven by silkworms after wax coating. Because of its good flexibility, knotting safety and high tensile strength, silk thread is often used by surgeons to evaluate the operating characteristics of other sutures and is currently used for vascular ligation, gastrointestinal surgery and fascial suturing. However, silk sutures have their own drawbacks. Once a wound becomes infected, a sinus tract can form that will not heal until the knot is completely removed. If used for suturing contaminated or infected wounds, it is more likely to cause wound infection or abscess formation. If used for sutures in the urinary tract or biliary tract, it can easily lead to stone formation. In addition, silk sutures do not retain tension in the tissue for long periods of time, with the tension strength dropping to 1/3 of the initial strength within 6 months, and in recent years, many controlled clinical studies have shown that the surgical complications associated with the use of silk sutures in surgery are significantly higher than those associated with absorbable sutures.
- Metallic sutures are monofilament or braided sutures of varying thickness made of silver, stainless steel, etc. Their basic characteristics include high tensile strength, easy sterilization, low tissue reaction, and almost complete inertness. As long as the suture does not break, there is very little loss of tensile strength in the tissue. Therefore, it is the ideal suture material for abdominal wall wounds that require high strength sutures, especially for infected abdominal wall incisions that are re-sutured. In addition to the commonly used non-absorbable sutures such as silk and metal sutures widely used in clinical practice, there are other types of synthetic non-absorbable sutures that are often used in clinical practice.
- Nylon thread is a chemically synthesized polyamide polymer nylon suture, which is particularly suitable for hypotonic sutures and skin sutures because of its good elasticity.
- Polyester thread is a multi-stranded fiber suture made of untreated polyester fibers (polyethylene terephthalate) tightly woven. It is stronger than natural fibers, has a mild tissue reaction, and is particularly suitable for the repair of synthetic vascular materials.
- Polypropylene thread is a linear hydrocarbon polymer of balanced crystalline stereoisomers as the raw material of polypropylene suture, not easily degraded or weakened by tissue enzymes. It has been widely used in general surgery, vascular surgery and plastic surgery for surgical closure.
- Principles of suture selection for clinical application
Depending on the choice of the surgical incision, the patient’s own factors, the nature of the surgery, and the suture tissue, the surgeon should appropriately select sutures that can maintain their strength and withstand the suture tension until the suture tissue is fully healed. In addition, the surgeon should also be aware of the physical properties of the suture material that may cause biochemical reactions in the body after surgery, especially in the first week after surgery. Most suture materials cause only minor tissue reactions, and synthetic materials tend to have less of a tissue reaction than natural fibers. We usually use the thinnest sutures that match the natural strength of the suture tissue and choose to apply nonabsorbable sutures or longer-lasting absorbable sutures to slow-healing tissues, such as fascia and tendons. Absorbable sutures are used to close tissues that grow and heal quickly, such as the stomach, colon, and bladder. For potentially contaminated tissues, multi-stranded fiber sutures should be avoided in favor of single-stranded fiber sutures and absorbable sutures that are less susceptible to bacterial attachment, especially antibacterial absorbable sutures. For areas with special emphasis on cosmetic effects, the finest inert single-stranded suture materials such as nylon sutures and polypropylene sutures should be considered, and subcutaneous tissues should be sutured as much as possible to avoid skin suturing alone. If the situation permits, consider using sterile skin suture tape to ensure tight skin edge alignment. Absorbable sutures should be used for urological and biliary procedures because the presence of foreign bodies in solutions containing high concentrations of crystals may cause precipitation and stone formation.
- Principles of suture selection for clinical application
The ideal surgical suture needle for clinical application is made of high quality stainless steel. It should be as thin as possible without affecting the strength. It can be held securely by the needle holder. The damage caused by guiding the suture through the tissue is minimized. Sharp enough to pass through the tissue with minimal resistance. The perfect balance of stiffness and toughness that resists bending without breaking. Sterile and resistant to corrosion, preventing the entry of microorganisms or foreign bodies into the wound. Surgical sutures are available in different thicknesses, and suture needles are available in different shapes, both of which are important for their versatility. The size and physical characteristics of the needle must match the thickness of the suture in order to work in harmony. The most important thing in the selection of the ideal surgical suture is that the damage caused by suturing the tissue should be as small as possible. Round needles are often used for suturing tissue that is easy to pass through, while angled needles or other special needles are more often used for suturing tough, hard-to-pass tissue. The length, diameter and curvature of the needle should be selected according to the specific requirements of the suture site.
- Principles of knot tying and knot tying techniques in surgery
Stable and accurate knot tying technique is also an important part of good suturing technique during surgery. The choice of the type of knotting depends on the sutures used, the depth and position of the incision and the size of the postoperative wound under tension. The knot must be tied slowly and carefully; tying it too quickly will result in poor suture positioning. The size of the tension applied to the wound must also be taken into account, leaving room for the formation of postoperative tissue edema. At present, the general principles of knotting suitable for various sutures are:
- The knot must be firm and cannot slip off, and the simplest knot is the most desirable within the specifications and characteristics of all suture materials.
- On the premise of ensuring a strong and safe knot, it is recommended to apply a small size of knot to minimize the excessive tissue reaction to absorbable sutures and to minimize the foreign body reaction to nonabsorbable sutures. It has even been suggested that intraoperative intradermal sutures should be closed with small “self-locking knots” instead of traditional square knots, in the hope of reducing tissue reactions and ensuring good healing.
- Avoid rubbing sutures between tissues and avoid damaging sutures when using surgical instruments to tie knots.
- Avoid excessive tension to pull the sutures and cut the tissues.
- Too many knots do not increase the strength of the appropriate knot, but only make the knot larger. The coefficient of friction of the knot directly affects its strength, the greater the coefficient of friction, the stronger the knot. Comparatively speaking, multi-strand fiber stitches are easier to handle and knot than single-strand fiber stitches.
- Common suturing techniques
Continuous sutures are a series of sutures made with a single needle and thread, in which the suture is knotted or looped at each end itself, including simple continuous sutures, continuous lockstitch sutures, etc. Continuous sutures are fast and their strength comes from the evenly distributed tension throughout the suture. However, care must be taken to apply steady tension rather than tight tension to avoid tissue strangulation. Excessive suture tension and instrument damage should be avoided to prevent suture breakage and complete release of the continuous suture. If the incision to be closed is contaminated, continuous sutures may spread the contamination along the entire suture line, and interrupted sutures with a single strand of suture material are recommended. Interrupted sutures are used to close the incision with multiple sutures and include simple interrupted sutures, interrupted vertical mattress sutures, interrupted horizontal mattress sutures, etc. Depending on the needs of the surgical operation and the nature and location of the sutured tissues, suturing techniques such as internal and external suturing are applied. Each suture is tied and cut separately, which makes the suture stronger, and even if one suture breaks, the rest of the sutures can still make the incision edges close together. Interrupted sutures should be used in the presence of contaminated incisions. A purse-string suture is a continuous suture around the lumen and the embedded tissue, which can be tightened and turned over like a drawstring. The purse-string suture is mainly used to embed appendiceal stumps, intestinal tube breaks, etc. It is also commonly used to secure fistulas and drainage tubes. The subepidermal suture is a continuous suture of the subcutaneous tissue located under the epithelial layer, the suture is parallel to the incision and is a short suture along the lateral edge of the entire incision. When the sutures are tightened, both the distal and proximal ends are secured in the same manner. The penetrating hypotonic suture is a suture that is placed intra-abdominally through all layers of the abdominal wall, including the peritoneum. When sutures are used to close the abdominal wall, non-absorbable suture materials such as hypotonic sutures should be applied in a timely manner if there is a risk of sudden stress on the sutures due to the increased intra-abdominal pressure in the patient, and care must be taken to avoid strangulation and necrosis of the organs at the suture site due to excessive pressure. After the factors of increased intra-abdominal pressure have been eliminated, the hypotonic sutures should be removed as soon as possible.