Chapter 41: Wound Closure

The major goal of wound closure is to restore the skin's integrity in order to reduce the risk of infection, scarring, and impaired function. This may be achieved by one of three methods: primary, secondary, and delayed closure. With primary closure, the wound is immediately closed by approximating its edges, with the main advantage being a reduction in healing time in comparison with other closure methods. Primary wound closure also may reduce bleeding and discomfort often associated with open wounds. Secondary wound closure, in which the wound is left open and allowed to close on its own, is particularly well suited for highly contaminated or infected wounds as well as in patients at high risk of infection. Although this method may reduce the risk of infection, it is relatively slow and uncomfortable and leaves a larger scar than primary closure. With delayed (or tertiary) closure, the wound is initially cleansed and then packed with dry sterile gauze covered by a sterile covering. The dressing is left undisturbed unless signs of infection—fever, purulent exudate, or spreading cellulitis—develop. After 4 to 5 days, the dressing is removed, and the wound edges can be closed if no infection has supervened. This approach may be useful for highly contaminated wounds and animal bites, and while commonly described and recommended, there is little evidence documenting the effectiveness for traumatic wounds seen in the ED.¹

Lacerations may be closed by one of five commonly available methods or devices: sutures, staples, adhesive tapes, tissue adhesives, and hair apposition. Each method has advantages and disadvantages (Table 41-1). Choice of the wound closure method and timing should take into account both patient and wound characteristics.² Cosmetic outcome is more closely related to practitioner technique and the patient's own healing characteristics than to any specific closure method or device. Many of the principles discussed in this chapter are based on experience and observation rather than on controlled trials.

One of the most important considerations when choosing a wound closure method is the amount of tension on the wound, both static (at rest) and dynamic (with motion). Linear lacerations subject to little tension can usually be closed by any one of the five closure methods. For low-tension lacerations, consider patient characteristics and preferences such as compliance, the availability to return for follow-up and device removal, and overall level of patient anxiety. With low-tension irregular lacerations, sutures may be the best alternative, allowing the greatest degree of precision for accurate wound edge approximation. Conversely, some small lacerations that would typically be closed may not actually benefit from primary closure. For example, simple (<2 cm) uncomplicated hand and finger lacerations, when treated with antibiotic ointment and gauze dressing, heal as fast and with no notable differences in appearance or function as those closed primarily with sutures.³ But note that this technique is limited to small, superficial hand lacerations; it cannot be recommended for larger lacerations and in other sites.

With lacerations subject to high tension (static and/or dynamic) one can relieve the amount of tension on the wound in order to avoid early dehiscence or gradual widening of the scar. Relief of tension is best achieved by careful undermining, placement of deep dermal sutures, and wound immobilization (when appropriate). After placement of deep, tension-relieving sutures, the superficial epidermal layer may be closed by any of the aforementioned closure methods. Reinforcement with adhesive skin tape is useful when the skin is thin, as in pretibial lacerations.^4,5,6

With patients at risk of keloid formation, it makes logical sense to relieve tension and minimize the amount of foreign material introduced into the wound. Skin tapes or tissue adhesives, instead of sutures, can minimize the amount of foreign material and inflammation that may increase the likelihood of excessive scar formation.

Sutures are the strongest of all the closure devices and allow the most accurate approximation of the wound edges, regardless of their shape or configuration. However, sutures are the most time-consuming and operator dependent of all wound closure methods and have the risk of inadvertent needle-stick injury. Using forceps to handle the needle during suturing can reduce this risk. A needle-catcher device is reported to be useful in reducing needle-stick injury during skin suturing.^7,8,9

Sutures may be classified as absorbable and nonabsorbable. Nonabsorbable sutures retain their tensile strength for at least 60 days. They are most often used to close the outermost layer of the skin (where they can be removed) or for repair of tendons (where prolonged strength is necessary due to very high tension). In general, nonabsorbable sutures are avoided in deep vascularized tissues where their presence stimulates a foreign body response with fibroblastic proliferation. Nonabsorbable sutures are differentiated by their origin and structure (Table 41-2). Due to their strength, handling, and relatively low tissue reactivity, synthetic monofilament sutures (such as nylon or polypropylene) are preferred. Polybutester sutures have the ability to elongate in response to external forces and possess elasticity to return to the original size once the load is removed. This property may be useful in wounds where swelling is anticipated. Less distensible sutures, such as nylon or polypropylene, cannot expand, and instead may lacerate the wound edges as the tissue swells.

Absorbable sutures lose most of their tensile strength in less than 60 days. As a result, they are well suited for closure of deep structures such as the dermis and fascia (Table 41-3). Poliglecaprone 25 has handling characteristics that are similar to nonabsorbable sutures (such as nylon) and is particularly useful for intracuticular or subcuticular closure. Due to its rapid absorption, poliglecaprone 25 should probably be limited to relatively low-tension wounds. With high-tension wounds, a suture with more sustained tensile strength is preferred. Absorbable sutures that incorporate the antibacterial agent triclosan are also available and may be especially indicated in contaminated wounds.^10,11 Rapidly absorbing sutures can also be used to close the superficial skin layers, especially when avoidance of suture removal is desirable.^12,13,14,15

For most ED use, the choice between absorbable and nonabsorbable material for percutaneous sutures is clinically irrelevant.^12,13,14,15 The cosmetic outcomes and complications of traumatic lacerations and surgical incisions closed with absorbable or nonabsorbable sutures have similar short- (infection, dehiscence) and long-term (cosmesis) outcomes.¹⁶ Absorbable sutures, like rapidly absorbing gut, are especially useful for skin closure in children who are not candidates for wound repair with skin tapes or tissue adhesives.

Suture material is categorized by the U.S. Pharmacopeia gauge size. The larger the suture size number, the thinner the suture, so that, for example, a 6-0 suture is thinner than a 5-0 suture. A general principle is that larger-diameter material produces more damage to the tissues and leaves larger holes in the skin, so generally thinner suture material is used whenever possible. Because smaller-diameter material has less strength, the trade-off is that more individual sutures closer together are sometimes needed to close a wound. Where cosmetic appearance is important, as on the face, smaller-diameter material is preferred (Table 41-4).

Improper tissue handling further traumatizes the tissues and results in an increased risk of infection and poor scarring.¹⁷ Gentle tissue handling using either skin hooks or the open limb of fine forceps is encouraged (Figure 41-1). Magnifying lenses such as surgical loupes can assist in accurate placement of sutures. While there are many types of surgical loupes available, a version useful in the ED is a magnifying power of 2.5× with the Keplerian lens system, which will provide a bright, clear image out to a field of view of 10 cm. Hemostasis is best achieved by direct pressure. Topical vasoconstrictors (such as epinephrine) applied to the wound edges and bed or mixed with the local anesthetic injected into the wound may help control bleeding in traumatic lacerations treated in the ED. With bleeding from vessels >2 mm in diameter, careful and selective placement of a ligature tie is often necessary. Electrocautery increases the risk of wound infection and scarring.¹⁷ The technique requires training and policies for its use, to ensure patient and healthcare professional safety.

The best cosmetic outcome is achieved by carefully matching each layer of the wound with its corresponding counterpart on the opposite side, ensuring eversion of the wound edges and minimizing the amount of tension on the wound. As the wound heals and the swelling subsides, the wound will eventually flatten, becoming flush with the surrounding skin surface. Inadvertent inversion of the wound edges may result in an unsightly depressed scar. A variety of suture techniques can be used to handle wounds of nearly all shapes, irregularities, and depths (Table 41-5).

SIMPLE INTERRUPTED PERCUTANEOUS SUTURES

Individual simple interrupted percutaneous sutures are the most basic and most commonly used approach to close lacerations. Introduce the needle through the outer layer of the skin, and exit at the level of the dermis on one side of the wound. Then, reinsert the needle through the opposite wound edge starting at the level of the dermis and exit superficially (Figure 41-2). In order to ensure proper wound edge eversion, the needle should enter and exit the skin at equal distances from the wound and at an angle of 90 degrees. Wound edge eversion is achieved by taking a larger bite through the depth of the wound than through the more superficial layers (Figure 41-3).

The entrance and exit of the suture should be close enough to the wound edges that they are not puckered when the knot is tied but far enough away to allow the suture material a firm hold on the tissue. Sutures are tied using square knots, and, generally, the number of knot ties should correspond to the suture size (i.e., four ties for a 4-0 suture, five ties for a 5-0 suture, etc.). Additional ties do not increase the strength of a properly tied square knot; they only add to its bulk. The extra ties are to increase knot security and prevent unraveling. Once the knot is completed, it should be moved to one side of the wound so as to not rest directly over the edges. For simple linear lacerations, a useful approach is to place the first suture in the middle of the wound, creating two smaller segments that are sequentially bisected into smaller segments until adequate coaptation of the edges is achieved.

CONTINUOUS (RUNNING) PERCUTANEOUS SUTURES

The major advantage of this method is its rapidity, as the entire wound is closed before any of the suture material is cut. This technique is most appropriate for long linear lacerations. Because it does not allow for precise wound edge apposition, it should be avoided in irregularly shaped lacerations. With this method, the first suture is placed at one end of the laceration similarly to an interrupted percutaneous suture. After the knot is tied, the suture material is not cut, and the needle is reintroduced into the skin on the opposite side, pulling the suture across the wound at a 65-degree angle (Figure 41-4). The needle then crosses the depth of the wound in a circular motion perpendicular to the wound, exiting on the opposite side approximately 3 to 5 mm from the wound edge. This process is repeated as needed until the entire wound is approximated and a second knot is tied.

BURIED DERMAL SUTURES

Deep dermal sutures are used to reduce tension on the wound and to close dead spaces. Placement of buried dermal sutures requires judgment because the benefits for nongaping small wounds are unproven and their presence may increase the risk of infection in contaminated wounds.^18,19 Sutures through adipose tissue do not hold tension, are unnecessary in clean surgical cases, and only promote infection in contaminated wounds.^19,20

With buried dermal sutures, the needle is first inserted at the level of the mid dermis on one side of the wound and then exits more superficially below the dermal–epidermal junction (Figure 41-5). The needle is then introduced below the dermal–epidermal junction on the opposite wound side and exits at the level of the mid dermis. Thus the knot becomes buried in the depth of the tissue when tying of the suture is completed. The first suture is placed at the center of the laceration, followed by additional sutures that sequentially bisect the wound. The number of buried sutures should be minimized.

CONTINUOUS SUBCUTICULAR SUTURES

The continuous subcuticular suture is one of the more complex methods of wound closure. The major advantage of this method is that it results in fairly good wound approximation, often without requiring any percutaneous sutures. For this technique, after anchoring the absorbable suture at one end of the wound, sequential, horizontally oriented "bites" are taken immediately below the dermal–epidermal junction, working toward the other end until the wound is adequately approximated (Figure 41-6). The second knot is tied with the tails cut short so as to remain buried.

VERTICAL MATTRESS SUTURES

Vertical mattress sutures combine some of the advantages of deep and percutaneous sutures. They also result in excellent wound edge eversion. Vertical mattress sutures are particularly useful in very thin or lax skin and in areas where the deep subcutaneous tissues are too fragile to be used for anchoring tension-reducing sutures (e.g., over the shin). After taking a large, deep bite from both sides of the wound ("far to far"), the direction of the needle is reversed, and a smaller superficial bite is taken from both sides ("near to near") of the laceration (Figure 41-7). Vertical mattress sutures may result in excessive tension on the more superficial skin edges, which reduces blood supply to the skin and may result in necrosis of the wound margins.

A modification of the standard vertical mattress suture is the shorthand version. In this approach, the first throw is close to the wound edges ("near to near"); the suture is then grasped and pulled away from the wound, elevating the wound edges while a second throw is performed farther away from the wound ("far to far") (Figure 41-8).²¹ This shorthand version can be performed in less time with the same outcome; however, blind placement of the larger bite may injure underlying structures.

HORIZONTAL MATTRESS SUTURES

The horizontal mattress is a good suture technique to close wounds with poor circulation to the wound edges because no percutaneous punctures that could further disrupt skin perfusion are placed close to the wound edges. This suture also reduces tension at the wound edges and reduces the potential for subsequent local necrosis. Horizontal mattress sutures can close a wound with fewer individual stitches because each stitch encases more tissue than other techniques (Figure 41-9). This suture is useful on the volar surfaces of the hands and fingers, because these delicate skin areas may swell but the skin edges are not easily cut due to the placement of the skin punctures far from the wound. The main disadvantage of the horizontal mattress stitch is the skill required to place the suture to achieve wound eversion.

HORIZONTAL HALF-BURIED MATTRESS SUTURES

Horizontal half-buried mattress sutures are particularly well suited for closing the tip of skin flaps and stellate lacerations because they minimize strangulation of the blood supply to the tip. The key to this stitch is that the needle and suture pass through the dermis of the tip and not the epidermis. The needle is introduced percutaneously through one side of the wound, then horizontally through the tip at the level of the dermis. The suture is completed by exiting the skin through the other side and tying the knot (Figure 41-10).

The major advantages of staples are their speed and relative ease of use.^{22,23,24,25,26} They are also cost-effective, especially when devices containing fewer staples are used in the ED, where most lacerations are relatively short. However, of all closure techniques, staples allow the least precision in wound approximation. As a result, their use should be limited to linear, nonfacial lacerations. Staples are particularly useful for scalp lacerations because the hair does not require clipping and staples are easier to locate than sutures for removal.^22,23,24,25 However, deep sutures may be required to close lacerations of the galea aponeurotica, whereas percutaneous sutures are always desirable when hemostasis is difficult. In appropriate patients, staples have infection rates and cosmetic outcomes similar to sutures. Staple removal is more painful than removal of sutures.²⁷

Although a variety of stapling devices are commercially available, there are few practical differences between them from the standpoint of the emergency practitioner. The key principle is to approximate the wound edges and align the centerline indicator of the head of the stapler so that the legs of the staple will straddle the wound an equal distance on each side (Figure 41-11). Touch the stapler lightly to the skin so that the staple comes out and pinches the wound edges together with eversion. Pressing firmly downward can cause depression of the wound edges. After the staple is set, pull the stapler slightly backward to disengage. New stapling devices that allow placement of deep staples are available, but they have not been studied in the ED.

Adhesive tapes are the least reactive and most cost-effective of all wound closure devices.²⁸ Their application is simple, painless, and rapid, and they also do not require formal removal. However, adhesive tapes tend to slough off when exposed to any tension or moisture. As a result, their use is limited to very low-tension simple wounds or for closure of fragile skin subject to low tension, like superficial skin tears. They are also of little use in noncompliant patients because they are so easy to remove.

In order to increase their adhesiveness, skin tapes should be used in conjunction with an adhesive adjunct, such as tincture of benzoin or Mastisol^®, that is gently painted on either side of the wound edges and allowed to dry until tacky. Because these adhesive adjuncts are toxic to wounds, avoid their introduction into the wound itself.

The tapes should be placed perpendicular to the wound edges approximately 2 to 3 mm apart. With long lacerations, the first strip of tape should be placed across the center of the wound followed by additional strips on either side of the wound center (Figure 41-12). To reduce the possibility of skin blistering or premature dislodgement, additional strips should be placed over the ends of the other strips, parallel to the laceration.

Simple skin tapes may also be used to reinforce lacerations after suture or staple removal. The cosmetic results and dehiscence rates after closure of small (<4 cm) and superficial facial lacerations with tapes are similar to those with cyanoacrylate tissue adhesives.²⁹ A version of skin tape comprised of two independent parts, each with an adhesive underside and multiple interlocking filaments attached to pulling ends, is useful for simple wound closure (Steri-Strip^™ S Surgical Skin Closure; 3M, St. Paul, MN; Figure 41-13).^30,31

The cyanoacrylate tissue adhesives are liquid monomers that polymerize into a stable bond when they come into contact with moisture.³² The adhesive is applied topically to the epidermis across the apposed wound edges, forming a strong bridge that holds the wound closed. The adhesive is sloughed off in 5 to 10 days as the skin renews itself. The tissue adhesives offer many advantages over other wound closure methods. They may be applied rapidly and painlessly to any easily approximated laceration. Because they slough off spontaneously, they do not require removal. The cyanoacrylates form an occlusive dressing that serves as a barrier to microbial penetration. They have antibacterial effects in vitro and reduce infection rates in experimental contaminated wound models in animals.³³

The cyanoacrylate tissue adhesives are similar in strength to 4-0 poliglecaprone subcuticular sutures, but weaker than staples.³⁴ Tissue adhesives should not be used alone for high-tension wounds nor should they be used for wounds subjected to varying dynamic tension, like over a moving joint. However, they can be used in conjunction with deep dermal sutures and/or immobilization aimed at reducing wound tension. A variety of octyl- and butyl-based cyanoacrylate adhesives are now commercially available. The tensile strength and surface characteristics of octyl- and butyl-cyanoacrylate differ (Table 41-6).³⁵ Octyl-cyanoacrylate is generally stronger and more flexible than butyl-cyanoacrylate, allowing its use on irregular surfaces and long lacerations. The mechanical characteristics of the adhesive are also determined by a number of additives such as chemical initiators and plasticizers.

Wound closure with the tissue adhesives is faster than with other wound closure methods, is cost-effective compared with sutures, and has comparable rates of infection and ultimate cosmetic appearance.^{36, 37, 38, 39, 40, 41} Patient-reported pain scores and physician-reported procedure time are lower with tissue adhesives.^42,43 However, there is a small increase, about 4%, in wound dehiscence using tissue adhesives, emphasizing the need to limit the use of adhesives to low-tension wounds.

Few studies have directly compared the various cyanoacrylate tissue adhesives against each other. For closure of short, simple facial lacerations in children, comparable results are seen with either type of cyanoacrylate.⁴⁴ For closure of pediatric operative wounds, octyl-cyanoacrylate had a lower wound dehiscence rate.⁴⁵

To ensure optimal results, tissue adhesives should only be used when laceration edges are easily approximated with the practitioner's hands, forceps, or tape. An assistant can maintain constant and meticulous wound edge apposition while the adhesive is applied. With octyl-cyanoacrylate, the adhesive is carefully expressed through the tip of the applicator and gently brushed over the wound surface parallel to the wound edges in a continuous, steady motion (Figure 41-14A). The adhesive should cover the entire wound and extend 5 to 10 mm on either side of the wound edges. After allowing the first layer of the adhesive to polymerize for 30 to 45 seconds, apply a second layer of adhesive. With butyl-cyanoacrylate, the adhesive is applied from the tip of the applicator in discrete drops along the wound edges, similar to "spot welds" (Figure 41-14B), or as a thin single layer.

With long or complex lacerations, adhesive tape can be used to approximate the wound edges, making closure with an adhesive easier (Figure 41-15). Application of a tissue adhesive on top of adhesive tape also results in greater wound-bursting strength than either device alone.⁴⁶ A combination of a mesh tape and tissue adhesive has recently become available and may be especially useful on very long lacerations.⁴⁷ Care in application will reduce some of the common problems associated with tissue adhesives (Table 41-7).

Simple scalp wounds, without contamination or active bleeding, may be closed via the hair apposition technique.^48,49 This technique is an efficient alternative to more traditional methods of closure, with potentially fewer complications, less pain to the patient, and less overall cost.^50,51,52 Contraindications to hair apposition closure include large lacerations (e.g., >10 cm), grossly contaminated wounds, uncontrolled bleeding, wounds that gape open and cannot be closed without significant tension, and hair strands adjacent to the wound that are less than 3 cm in length.

After wound irrigation and control of bleeding, select and twist together three to seven stands of hair at least 3 cm in length that lie close to the edge on one side of the wound. Repeat this process directly opposite on the other side of the wound. Then twist these two hair bundles in a full 360-degree revolution and secure the intertwined hair bundles by applying a few drops of tissue adhesive. Repeat this process as needed to close the full length of the laceration (Figure 41-16). The patient will not need routine return because the tissue adhesive will flake off and the hair will unravel in about a week.