Suture Material

Published on 26/02/2015 by admin

Last modified 26/02/2015

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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