Suturing Technique and Other Closure Materials

Chapter Summary

Choice and placement of wound closure materials play critical roles in the outcome of incisional surgery.
The properties of suture materials combine to give each suture unique characteristics.
Sutures must be placed at the same vertical level across the wound to prevent step-off deformity of the incision.
Proper placement of sutures will approximate and evert wound edges.
Buried sutures are used to close dead space, redistribute tension, decrease dehiscence, and increase wound eversion.
Time to suture removal varies by location; whenever possible, sutures should be removed at the earliest point.

Introduction

A variety of suture and closure materials have been developed and it is essential that the dermatologic surgeon becomes familiar with the various physical properties in order to make educated choices that will result in an optimal scar. In addition, learning the appropriate suturing techniques and the appropriate situations in which to use them is critical.

Selection of closure material and technique is determined by lesion location, anticipated wound tension, defect size, type of repair, and patient characteristics. In general, finer-caliber sutures are used on the face, while larger sutures are used on the scalp, trunk, and extremities. Staples are often used to close wounds of the scalp and trunk. Larger-caliber sutures are required for wounds under more tension. For example, the surgeon may use absorbable sutures in patients who are unable or unwilling to return for suture removal. Similarly, needle-free tissue adhesives are commonly used to repair simple lacerations in children.

The size of the needle driver should be proportional to the size of the needle and to the size of the wound. Forceps with teeth are preferred when placing suture because the teeth hold the tissue without crushing it. In contrast, forceps without teeth are favored for grasping suture at the time of suture removal. When undermining wound edges, skin hooks are the least traumatic means of stabilizing and mobilizing the wound edges. Suture should be cut with designated suture scissors and not with delicate tissue scissors. Alternatively, special needle holders are available that incorporate a suture cutting function in their design, thereby eliminating the need for a separate pair of suture scissors and shortening the time to perform the closure. Finally, quality needle holders, skin hooks, scissors, and forceps should be used and maintained for ideal surgical results. Educating the surgical staff about these principles is important to optimize efficiency and performance and to preserve the surgical instruments.

Choosing a Closure Material

Suture

Physical properties of suture

Each type of suture has inherent characteristics which affect its handling, tying, and stability in tissue. Characteristics to be considered include: configuration, coating, capillarity, tensile strength, size, knot strength, memory, elasticity, plasticity, and flexibility. Sutures are classified into absorbable and non-absorbable categories. In a typical layered closure, both types are utilized to achieve a good cosmetic and functional result.

Configuration

The configuration of suture denotes its composition: monofilament suture is made up of a single strand, and multifilament suture is made up of several strands. Strands of multifilament suture are often twisted or braided for cohesiveness. Advantages of braiding include increased tensile strength, improved handling and knot-tying properties, and decreased fraying of cut ends. However, braided sutures have an increased propensity to retain microorganisms and encounter more resistance when pulled through tissue. Monofilament sutures have a decreased coefficient of friction and slide easily through tissue. Monofilament sutures may be useful to close contaminated wounds which may be at higher risk for surgical site infection.

Coating

Sutures may be coated with various materials to improve the coefficient of friction and thus facilitate passage through tissue. Knot strength correlates with the coefficient of friction. Coating braided sutures with silicone, Teflon (DuPont, Wilmington, DE), and wax decreases friction, allowing the suture to slide more easily through the skin. Newer innovations include suture coatings with either antibacterial or antitumor qualities. For example, polyglactin 910 has been coated with the antimicrobial agent triclosan and has been shown to prevent in-vitro colonization of Staphylococcus aureus and Staphylococcus epidermidis . However, clinically, there have been reports showing both an increase and a decrease in wound infections.

Capillarity

Capillarity denotes a suture's ability to wick fluid from an immersed end and transfer it to its dry end. Sutures with increased capillarity, such as braided sutures, are more likely to harbor bacteria.

Tensile strength

Tensile strength is defined as the weight necessary to break a suture divided by the cross-sectional area. Tensile strength is proportional to the square of the suture diameter, so larger sutures have increased tensile strength. Various factors can affect tensile strength, including twisting or braiding, which, due to shearing forces between the strands, decreases tensile strength. Knotted suture has one-third the tensile strength of the unknotted suture. Tensile strength can also be decreased by physical factors including wetness or increased age of sutures. Synthetic sutures tend to have increased tensile strength compared to sutures of natural materials. The exception is stainless steel, which has the greatest tensile strength.

Size

To allow surgeons to compare sutures made of different materials, the United States Pharmacopeia (USP) assigns a number to all commercially available sutures. This number or “size” ranks sutures according to tensile strength, represented by a number of zeros. The greater the tensile strength, the fewer the zeros. Therefore a 2-0 suture has more strength than a 6-0 suture. The strength quality inherent in the materials used to make sutures varies; thus the caliber of a 5-0 nylon will be smaller than that of a 5-0 gut because nylon is a stronger material. The smallest diameter suture required to provide adequate tensile strength should be used in wound closure.

Knot strength

Knot strength refers to the security of a tied knot and is defined by the degree of slippage that occurs in a knot. Sutures with a decreased coefficient of friction slide more easily and have lower knot strength. Sutures vary widely in their knot strength. For example, catgut suture has low knot strength while polyglycolic acid has one of the highest knot strengths.

Memory

Memory is the ability of a suture to regain its former shape after bending. Knots in sutures with increased memory, such as polypropylene and nylon, have a greater tendency to untie themselves, and the surgeon therefore should throw extra ties with these sutures. In general, sutures with increased memory are more difficult to handle (see Table 13.3 ).

Elasticity

Elasticity denotes a suture's capacity for returning to its original size and shape after being stretched. This quality may be desirable in selecting a surface suture because tissue usually swells after a trauma such as surgery. Sutures with elasticity can stretch with the tissue, and will also recoil when the swelling subsides, thereby allowing the suture to maintain appropriate tension. Polybutester is a synthetic non-absorbable suture which exhibits elasticity.

Plasticity

In contrast to elasticity, sutures such as polypropylene exhibit plasticity, and thus have the ability to retain their deformed shape rather than return to their original shape when stretched. As tissues swell, sutures that exhibit plasticity are able to stretch to accommodate the edema without cutting into the tissue. However, as swelling resolves, sutures with plasticity remain stretched, and this can decrease close approximation of tissues. Plasticity may be advantageous in knot tying because deformation of the suture may lead to a more secure knot.

Tissue reaction

All sutures exhibit at least some inflammatory response when placed in tissue, but the degree varies widely. This suture property is very important because exuberant inflammatory reactions have been shown to delay wound healing, to jeopardize wound apposition, and predispose to infection. Many factors contribute to tissue reactivity ( Table 13.1 ). The caliber of suture is directly proportional to its reactivity; thus the greater the suture diameter, the greater the chance of tissue reaction.

Table 13.1

Suture properties that affect immunogenicity

	More immunogenic	Less immunogenic
Material	Natural	Synthetic
Configuration	Multifilament	Monofilament
Absorption	Absorbable	Non-absorbable
Diameter	Large	Small

Configuration also affects a suture's ability to cause tissue reaction: monofilament sutures cause less reactivity than multifilament sutures. Synthetic sutures such as nylon or polypropylene also cause less of an inflammatory response than sutures made of natural materials such as silk and surgical gut. All absorbable sutures – synthetic and natural – induce an immune response which is responsible for their dissolution. Sutures made of natural materials (gut and silk) are degraded by proteolysis, in contrast to synthetic sutures which are degraded by hydrolysis. Proteolysis causes a more brisk immune reaction than hydrolysis. Non-absorbable sutures cause less tissue reaction because they induce a fibrous shell that coats the suture and decreases the host response.

On rare occasions, true suture allergy may occur, particularly with sutures made of gut. Allergy to gut suture may be due to the foreign collagen or to chromic salts in chromate-sensitive patients. Immediate-type IgE-mediated hypersensitivity reactions have been reported with bovine collagen materials, which may be found in gut suture. In the cases reported, presence of allergen-specific IgE was confirmed by skin-prick testing. Silk can rarely cause an extensive, destructive, suppurative, and granulomatous response, which may be a type of delayed-type hypersensitivity reaction. Such sensitivity to silk can be confirmed or predicted with an intradermal skin test.

Absorption

Absorbable sutures as a group are defined as sutures that lose the majority of their tensile strength within 60 days after placement in living tissue. Non-absorbable sutures therefore maintain their tensile strength for periods greater than 60 days. All suture materials, excluding stainless steel wire, lose integrity or are absorbed to some degree if left in the skin for long enough. Depending upon the material used, integrity may range from 6 days to 6 months, or longer. The rate of absorption depends on the suture type, the presence of infection, and site of placement. Presence of infection increases suture absorption, as does placement in locations where there is high secretion of proteolytic enzymes, such as mucosa.

Levenson and associates have demonstrated that intrinsic tensile strength of a wound is 7–10% of native strength. At 5 weeks, the tensile strength is 60% and it is unlikely that the wound will dehisce with normal activity. During this time period, absorbable sutures are used to provide tensile strength and wound edge approximation until the scar is adequate.

Commonly used sutures in dermatologic surgery

Absorbable sutures

Surgical gut

Surgical gut is the only absorbable suture made of natural materials. Derived from the intestines of sheep or cows, gut suture is a twisted multifilament suture composed mostly of collagen. Gut sutures commonly come in three varieties: plain, fast absorbing, and chromic ( Table 13.2 ). Plain surgical gut loses much of its tensile strength in 7–10 days and is completely absorbed by 70 days. Fast-absorbing gut is heat treated for more rapid degradation. This suture is used in facial wound closures or the placement of skin grafts when rapid absorption of suture is desirable. Nearly all of its tensile strength is lost within 7 days, and complete absorption takes 21–42 days. Chromic gut has been treated with chromate salts, which decrease the rate of absorption in tissue. Chromic gut maintains its tensile strength for 10–21 days and is completely absorbed after approximately 90 days. This suture may be used to ligate vessels in open wounds or to suture mucosal wounds. A history of chromate sensitivity should preclude the use of this suture. Disadvantages to gut sutures include unpredictable absorption rates, low tensile strength, and increased tissue sensitivity when compared with other absorbable sutures.

Table 13.2

Properties of absorbable sutures

Suture (brand name)	Configuration	Handling	Knot strength	Tissue reactivity	Initial tensile strength	Longevity of tensile strength	Time to complete absorption	Comments
Surgical gut, plain	Multifilament Twisted	Interm	Poor	High	Low	Lost in 7–10 days	70 days	Unpredictable absorption rates
Fast-absorbing gut	Multifilament Twisted	Interm	Poor	High	Low	Lost in 3–7 days	21–42 days	High reactivity True allergy possible
Chromic surgical gut	Multifilament Twisted	Interm	Fair	Moderate to high	Low	Lost in 10–21 days	90 days	Unpredictable absorption rates High reactivity True allergy possible to collagen or chromate
Polyglycolic acid (Dexon S) ^a	Multifilament Branded	Good	Good	Low to interm	Interm	35% strength at 3 weeks	60–90 days	Uncoated
Polyglycolic acid (Dexon II) ^a					Interm			Coated
Polyglactin 910 (Vicryl) ^b	Multifilament Branded	Good	Good	Low to interm	Quite high	50% strength at 3 weeks	56–70 days	Coated Higher tensile strength than Dexon
Polyglactin 910 (Vicryl Rapide) ^b		Good	Good	Low to interm		50% strength at 5 days	42 days
Lactomer (Polysorb) ^a	Multifilament Branded	Good	Good	Low to interm	Quite high	>30% strength at 3 weeks	56–70 days	Coated
Polydioxanone (PDS II) ^b	Monofilament	Poor	Poor	Low	High	50% at 4 weeks 25% at 6 weeks	90–180 days	High memory Very slow absorption
Polytrimethylene carbonate (Maxon) ^a	Monofilament	Very good	Very good	Very low	Very high	59% strength at 4 weeks 30% at 6 weeks	60–180 days	Has higher initial tensile strength than PDS but absorbed more quickly
Poliglecaprone 25 (Monocryl) ^b	Monofilament	Very good	Very good	Very low	Highest	30% at 2 weeks All lost at 3–4 weeks	90–120 days	Highest initial tensile strength Highest knot security of synthetic absorbable sutures
Glycomer 631 (Biosyn) ^a	Monofilament	N/D	N/D	N/D	N/D	49% retained at 3 weeks	90–110 days	Decreased coefficient of friction than Monocryl Seldom used in dermatologic surgery

N/D, no data available.

Very low—low—poor—fair—good—moderate—intermediate—relatively high—very high—very good—highest.

a Trademark of Covidien, Mansfield, MA.

b Trademark of Ethicon, Johnson & Johnson, Somerville, NJ.

Polyglycolic acid

Polyglycolic acid (Dexon S, Dexon II: Covidien, Mansfield, MA) was the first synthetic absorbable suture, first available in 1970. It is a braided multifilament suture, which creates significant drag when pulled through tissue. To alleviate this problem it is available with a polycaprolate coating; this is marketed as Dexon II. Nonetheless, some surgeons prefer the uncoated Dexon S because it has better knot security. Both coated and non-coated suture retain 65% of tensile strength 2 weeks after placement and 35% 3 weeks after implantation. It is completely resorbed between 60 and 90 days after placement. Advantages to its use include good handling and knot security and low tissue reactivity.

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