Suture Material

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5 Suture Material

Bret R. Baack, MD, Daniel L. Stulberg, MD, and Richard P. Usatine, MD

Many types of sutures are available, each with its own material properties, performance, and uses. The most useful sutures for skin surgery are described in detail in Tables 5-1 and 5-2.

TABLE 5-1 Characteristics of Absorbable Sutures

TABLE 5-2 Nonabsorbable Sutures

History

The use of sutures to close wounds is certainly not limited to the modern era. Ancient civilizations developed innovative methods to close wounds based on the materials then available. Horsetail hair threaded onto eyed needles made from bone was utilized by the Greeks as early as 5000 to 3000 B.C. An Egyptian scroll dating back to 3000 B.C. describes the use of linen as suture material.¹ South American Indians essentially created the first surgical “stapler” by using the heads of pincher ants to close wounds. The Roman physician Galen described the use of absorbable suture, specifically catgut, in 175 A.D.² Sterile suture material was formally introduced by Lister in 1869 by treating catgut with chromic acid.³ Interestingly, the benefit of using sterile sutures was discovered during the American Civil War a few years earlier (1861–1865). Due to a lack of available suture material, Confederate surgeons were reduced to using horsetail hair, which they boiled to make more pliable. This inadvertent sterilization of the suture material most likely led to the lower wound infection rate they experienced as compared to their Union colleagues.⁴

Wound Healing and Sutures

All sutures are foreign bodies and may increase the risk of wound infection if not used properly or left in place too long. The goal is to use the minimum suture required to keep the wound together until it heals. Deep (buried) or subcuticular sutures are beneficial in keeping wounds closed without leaving marks on the skin. External sutures are left in place just long enough to keep the wound closed because each extra day increases the risk of “railroad track” skin marking. Smaller sutures generally leave fewer skin marks and can lead to a better cosmetic result.

Wound healing is described by tensile strength, the force per unit area required to pull a wound apart. Studies show that a wound does not begin to gain significant tensile strength until about 3 weeks after closure at which point it has only 10% of its final tensile strength. Tensile strength increases more quickly after 3 weeks and reaches its maximum strength at around 60 days. It never returns to more than 80% of normal skin.⁵ Thus, wounds subject to any tension should usually be closed in two layers: a deeper dermal layer with suture material that will maintain significant strength for 6 to 8 weeks, and a second superficial skin suture that can be removed in 7 days or less without fear of wound disruption. A suture or staple left in the skin for more than 10 days will often allow epithelial cells to grow from the surface down into the dermis along the suture or staple tract, resulting in permanent scar tissue on each side of the incision scar itself and detracting from the final appearance of the healed wound. In addition, a suture that is tied too tight will cause necrosis and subsequent scarring of the enclosed tissue within the loop, resulting in cross-hatch marks, or “railroad tracks.” The goal of the superficial suture layer is to carefully approximate the epidermis, not to add significant strength to the closure. The deeper dermal sutures should take nearly all tension off the epidermal closure.

Suture Material Properties

Suture material is judged by several characteristics:

• Ease of handling and knot-holding ability

Ease of Handling and Knot-Holding Ability

These characteristics are generally determined by whether the suture is monofilamentous or multifilamentous. Monofilament sutures are smooth, synthetic in nature, and usually are stiffer and retain a high memory of their original shape within the package. Thus, they have a tendency to partially retain their packaging loop shape, which gets in the way of suturing and can sometimes lead to the dreaded “knot” that forms in the middle of the suture while performing a running stitch. In addition, their “slickness” makes it necessary to tie square knots (at least four ties) or use an extra tie when securing a surgical knot. However, they also tend to slide easily through tissues, cause very little tissue reaction, and do not tend to harbor bacteria on their surface. For these reasons monofilament sutures are preferred for external skin sutures. Multifilamentous sutures are twisted or braided to make them easier to tie and to improve their knot-holding ability, but the trade-off is that they have the potential to harbor bacteria between the strands, leading to an increased wound infection rate.

Absorbability and Breaking Strength

These terms are somewhat interrelated, as the absorbability of the suture correlates with the breaking strength of the suture with time. The United States Pharmacopeia (USP) officially defines absorbable sutures as those that lose breaking strength within 60 days, whereas nonabsorbable sutures retain their breaking strength beyond 60 days. See Table 5-3 for the details of strength retention and absorption in absorbable sutures. Breaking strength relates to the material used for construction of the suture as well as its diameter. The USP also defines the diameter of sutures. Sutures used for the skin usually range from 3-0 (relatively thick) to 6-0 (relatively thin). The smallest suture now available is 11-0 (about one-third the diameter of a human hair) and is utilized for the microsurgical repair of small blood vessels.

TABLE 5-3 Absorbable Sutures—Strength Retention and Absorption Profile

Visibility

Sutures range in visibility from clear, white, or light tan in color, to highly visible sutures that are blue, purple, green, or black. In general, lighter colored sutures are used as buried absorbable sutures in the dermis because a darker color could potentially be seen through the skin. Darker colored nonabsorbable sutures are used for the epidermal closure because their visibility aids in later removal. When suturing a wound in the hair-bearing scalp in an individual with dark hair, use a blue rather than a black suture to assist in suture removal. Once it was discovered that the practice of shaving hair for surgery actually increases the risk of wound infection, it became helpful to use sutures that can be distinguished from the surrounding hair. Of course, black or blue sutures will work equally well in a patient with blond hair.

Tissue Reactivity

This characteristic refers to the inflammatory response that suture material elicits in the body. Sutures derived from animal sources such as catgut and silk tend to elicit intense inflammatory reactions, whereas synthetic materials generate less of a response.

Absorbable Sutures

The absorbable sutures available in the United States are described in Table 5-1. Ethicon, a division of Johnson & Johnson, and Syneture, a division of Covidien, control 99% of the U.S. market (Ethicon, ~80%; Syneture, ~20%).⁶ Although absorbable suture is defined by its loss of strength within 60 days, the suture is not completely gone at that time. Even quickly absorbing sutures such as catgut can be found in the tissues for up to two years.⁷

Surgical Gut

Gut sutures have been used since 175 A.D. In addition to sutures, gut was also used for violin strings and bowstrings and, more recently, tennis racket strings. Gut sutures, also referred to as catgut, are derived from the intimal layer of the small intestines of sheep or cattle, and have nothing to do with cats. The origin of the name is unknown, but is thought to be derived from the word kitgut (fiddle string) with kit being the name of an Arabian fiddle with strings made from sheep intestine.⁸ Due to its heterogeneic derivation, it is highly inflammatory and is broken down quickly in vivo. Plain gut retains significant strength for only 4 to 5 days. Gut can be treated with chromic salts to essentially double its resistance to absorption. It is useful for closing oral, nasal, or vaginal mucosa where significant strength is not required beyond a week. Plain gut can be used in areas where suture removal may be difficult, such as near the lash line of the eyelids, but should not be used if the wound is under any tension. When using plain gut, five knots are necessary because it has a tendency to untie spontaneously when wetted.

As early as 1894 concerns were raised that the use of gut suture could potentially transmit anthrax bacilli and spores or other infectious material in the sheep.⁸ In the 1990s, the use of gut diminished significantly in Europe due to concerns about possible transmission of bovine spongiform encephalopathy (“mad-cow disease”), although there has never been a documented case of this occurring. Currently, the raw material is derived from herds certified free of the disease, and is highly processed. However, synthetic sutures are available that have comparable absorption profiles and handling characteristics and are less reactive, such as Vicryl Rapide™ (Ethicon) and Caprosyn™ (Syneture), that can be substituted for plain and chromic gut (see Table 5-1).

Synthetic Braided and Monofilament Sutures

These types of sutures are manufactured utilizing various polymer combinations to provide a suture with:

• Uniform chemical composition with predictable absorption patterns

• Less tissue reaction by avoiding naturally occurring organic material.

The first of these was Dexon™ (Syneture), which became commercially available in 1971.^2,⁹ It is a synthetic braided homopolymer of glycolic acid. In 1974 Vicryl™ (Ethicon) was introduced. Vicryl (polyglactin 910) is a synthetic braided copolymer of glycolide and L-lactide. These sutures are absorbed by gradual hydrolysis rather than by the host inflammatory response caused by gut. Their braided surfaces allow for easy handling and secure knots. However, the larger surface area and interstices of braided material can lead to entrapment of bacteria and possibly lead to a localized inflammation (“spitting” of the suture) (Figure 5-1) or more generalized wound infection.

FIGURE 5-1 Spitting suture.

(Copyright Richard P. Usatine, MD.)

In an attempt to decrease this risk of infection while maintaining prolonged tensile strength, synthetic monofilament sutures were developed. Their smooth surfaces diminish bacterial adherence compared to braided absorbable sutures. Examples are Monocryl™ (Ethicon) and Biosyn™ (Syneture), as well as somewhat more rapidly dissolving sutures such as PDS™ (Ethicon) and Maxon™ (Syneture). Vicryl or Dexon is recommended for interrupted deep dermal closure due to their superior knot-holding abilities and maintenance of significant tensile strength for at least 3 weeks. The absorbable monofilament sutures such as Monocryl or Biosyn are recommended for running subcuticular closures due to their lesser tendency to harbor bacteria.

When using absorbable monofilament sutures for running subcuticular closures, it is best to tie the end knots on the outside of the skin rather than burying them. This will avoid tissue inflammation and localized scarring as a result of placing a bulky knot with four to five throws below the skin. Taping down the ends with tissue tapes is another alternative. It is easy to clip off the knots at around 10 to 14 days, leaving the subcuticular portion of the suture intact.

Bioactive Sutures

In 2002, Ethicon released Coated Vicryl Plus™, an absorbable braided suture coated with triclosan, a broad-spectrum biocide used for more than 30 years in products such as toothpaste and soap. Its efficacy has been demonstrated in vivo and in animal models in which S. aureus is introduced into the wound during closure.¹⁰ Preliminary results suggest a reduction in sternal wound infections when used for closure of the sternal incision, and a reduction in shunt-infection rates when the suture is used for skin closure following the insertion of cerebrospinal fluid (CSF) shunts.^11,¹² This is the first “bioactive” suture to serve the dual purpose of closing a defect as well as decreasing the wound infection rate.

Nonabsorbable Sutures

Nonabsorbable sutures are typically used to close the epidermal layer of skin due to their low tissue reactivity and superior strength compared to absorbable sutures. They are also used for closure of fascia as well as hernia or tendon repair because they lose very little tensile strength with time. See Table 5-2 for an overview of the nonabsorbable sutures and their relevant properties.

Silk

Prior to the introduction of synthetic sutures, silk (nonabsorbable) and gut were the two sutures most commonly in use. Although classified by the USP as a nonabsorbable suture, silk does undergo phagocytosis as well as enzymatic degradation and is usually nonexistent after 2 years. Surgical silk is derived from the domesticated silkworm thread that is processed, dyed black, braided, and coated with wax or silicone to diminish tissue friction. Due to its derivation from organic substances, it is highly inflammatory, second only to gut. It is easy to handle and knots tie securely, but has low tensile strength compared to most sutures. These properties and the introduction of better synthetic sutures have made silk sutures less useful. It can be useful for the closure of oral mucosa because it is softer in the mouth than other sutures. Silk, however, needs to be removed, so chromic or plain gut is often used in the mouth as an alternative.

Nylon

The synthetic polymer Nylon 6 (Ethilon™ [Ethicon]) or Nylon 6,6 (Monosof and Dermalon™ [Syneture]) is an offshoot of synthetic materials that were developed for clothing and other commercial uses. It is uniform in consistency, and as a nonorganic substance generates much less tissue reaction than silk. It is available as either a monofilament or braided into a multifilament that feels and handles much like silk. The monofilament strand has low tissue friction, and is ideal for epidermal closure, although four to five throws are generally required for a secure knot.

Polypropylene

Polypropylene (Prolene™ [Ethicon] and Surgipro™ [Syneture]) is a synthetic monofilament suture developed in the 1970s to improve on the properties of nylon. Compared to nylon, it has greater tensile strength and less tissue adherence, making it ideal for a pull-out subcuticular suture. Even so, it is a good idea when closing a long incision with a subcuticular Prolene suture to bring out a loop of suture every 5 to 6 cm to make later removal easier. Another consideration would be to use a synthetic absorbable monofilament suture in that circumstance to avoid suture removal altogether. Polypropylene is excellent for running sutures on the face after a deep closure with buried absorbable sutures.

Needles

Surgical needles are available in a dizzying array of choices. Unfortunately, the nomenclature of needles is not standardized and depends on the manufacturer. Needles differ in shape, size, and point characteristics.

The shape of the needle can be straight, three-eighths, half circle, five-eighths, or J-hooked. The most popular skin needle is the three-eighths curved, as it is easy to manipulate in skin and superficial wounds with a slight supination of the wrist. A half circle or five-eighths curved needle is useful in confined spaces such as deep in the mouth.

Needle sizes for skin surgery usually range from 13 to 19 mm. Useful needles for skin surgery are those that are three-eighths of a circle and come in lengths of 13, 16, and 19 mm.

Needle points can be blunt, tapered, cutting, or spatulated. A cutting needle is preferred for skin surgery. Its cross section is triangular rather than round, and thus stronger and more resistant to bending. The conventional cutting needle has one pointed edge along the inside of the curve of the needle, and thus can potentially cut tissue along a wound edge. To avoid this problem, the reverse-cutting needle was created so that the third cutting edge is on the outside curve of the needle, away from the edge of the wound (Figure 5-2).

FIGURE 5-2 (A) Reverse-cutting needles. (B) Conventional cutting needles.

(Redrawn from and courtesy of Ethicon product catalog Sutures/Adhesives/Drains/Hernia Repair.)

Needles from Ethicon used in skin surgery are named with the following nomenclature:

• P or PS (plastic): fine reverse-cutting plastics needle

• PC (precision cosmetic): fine conventional cutting plastics needle

• FS (for skin): basic reverse-cutting skin needle—not as sharp as the plastics needles.

See Figure 5-3 for a comparison of the many types of three-eighths needles made by Ethicon that are used in skin surgery.

FIGURE 5-3 Needles for skin surgery.

(Adapted from Ethicon product catalog Sutures/Adhesives/Drains/Hernia Repair.)

Needles from Syneture used in skin surgery are named with the following nomenclature:

• P (plastic): fine reverse-cutting plastics needle

• DX (= PC): conventional cutting plastics needle

• C (cutaneous) (= FS): reverse-cutting skin needle.

See Tables 5-4 and 5-5 for more details about needles and sutures. Personal preferences for needles develop through experience and help clinicians choose their preferred needle in each surgical situation.

TABLE 5-4 High-Quality Needles for Skin

TABLE 5-5 Details of Recommended Sutures

Suture and Needle Selection

Suture Selection

The ideal suture would hold tissues together until they have gained enough tensile strength to heal without the risk of dehiscence. After that time, the suture material would disappear, leaving no sign that it was ever there. Although no such suture currently exists, some sutures are more appropriate for certain circumstances than others. For tissues that heal slowly such as fascia and tendon, a nonabsorbable suture is preferred. For skin, a two-layered closure is preferred, with suture size varying depending on the area of the body. Extremity and trunk skin tends to be thicker and under more tension than facial skin, and therefore larger needles and sutures are preferred. Table 5-6 is a listing of preferred suture by location. The sutures listed are manufactured by Ethicon, as they currently provide 80% of sutures in the United States. We have no ties (pun intended) to Ethicon and have found both Ethicon and Syneture sutures to be equal in performance.

TABLE 5-6 Recommendation of Suture by Location

Needle Type

A vast array of needles are available to the surgeon depending on the intended usage of the suture. Plastics needles are preferred because these are sharper than standard skin needles. Reverse-cutting needles avoid inadvertently slicing through the skin at the edge of the wound while passing the needle through the tissue. A three-eighths curvature is recommended unless one is working deep in the mouth where a half-curved needle may be easier to manipulate.

Needle Length

Needle length is chosen based on the skin thickness and the desired length of the placed sutures. When closing thin skin on the face or genital area, a 13-mm needle length is a good choice for both the absorbable and nonabsorbable sutures. When suturing the back it helps to have a longer needle such as one that is 19 mm in length. For other areas of intermediate skin thickness, a 16-mm needle length should be adequate.

Keep in mind that a larger needle allows for larger and fewer stitches when running a suture whether it is external or subcuticular. A 16-mm needle is a good length for closing a punch biopsy regardless of the location. With experience your choices may vary and be different based on personal preference.

Length of Suture

Most sutures for the skin will be 18 inches in length. One way to save money on sutures used for closing punch biopsies is to purchase a suture that is only 9 inches in length. This is adequate for one to three interrupted sutures and can be half the price of the full-length suture. Delasco sells this in 4-0 and 5-0 nylon on a plastics reverse-cutting needle of 16-mm length with three-eighths of a circle configuration.

Conclusion

The large variety of sutures available makes it difficult to decide which products are going to be right for you and your patients. Table 5-5 contains detailed information about the commonly stocked skin sutures in an office practice. To do the procedures in this book, you will need at least one type of absorbable and one type of nonabsorbable suture. The minimum starting set should probably include:

Work on Face

• Polyglactin (Vicryl), 4-0 and 5-0 with 13- and 16-mm needles (Dexon is an alternative)

• Polypropylene (Prolene or Surgipro), 5-0 and 6-0 with 13- and 16-mm needles.

Work on the Neck and Below

• Polyglactin (Vicryl), 4-0 with 16-mm needle (Dexon is an alternative)

• Nylon and/or polypropylene 4-0 and 5-0 with 16-mm needle.

Work in Deeper Wounds or Areas That Will Be Stretched with Activity or Are under Tension (Back, Shoulders, Legs)

• Polyglactin (Vicryl), 3-0 with 16- or 19-mm needle

• Nylon and/or Prolene 4-0 with 19-mm needle.

Reverse cutting is probably the best starting needle type because it will be less likely to inadvertently cut tissue. Then consider trying conventional cutting needles to see what works best in your hands.

Consider carrying some silk if you work on mucosal membranes. Silk is softer inside the mouth. Fast-absorbing sutures such as fast-absorbing gut, Vicryl Rapide, or Caprosyn can be used for patients who may not be able to return easily for suture removal and can also be used inside the mouth.

Add a monofilament absorbable suture if you will be doing subcuticular closures in which the suture will remain in place to dissolve over time. Do not buy too many sutures at first until you settle on the sutures that will be best in your practice.