Basic Concepts in Wound Repair

Definitions

• Primary closure is defined as the surgical closure of a wound in one or more layers, within hours of its occurrence. Most surgical incisions and traumatic lacerations are closed primarily.
• Delayed primary closure is the surgical closure of a wound, days to weeks later. The granulation tissue is excised, the edges of the wound are freshened and the wound is closed. An example of this technique is the closure of a fasciotomy incision.
• Skin grafting is indicated when a defect is too large to close primarily, and creation of flaps is not desirable or feasible. It can be performed immediately following the injury or in a delayed manner. The indications and principles of skin grafting are discussed elsewhere in this book.
• Surgical flaps allow the recruitment of local or distant tissue for wound coverage. They are discussed in detail in an upcoming chapter.
• Healing by secondary intention is the choice a surgeon is left with when a wound cannot be surgically repaired. This doesn’t mean that the surgeon can leave the wound to heal on its own; daily care and a long-term commitment by the patient and the care-givers are required. The wound must be kept clean and bacterial colonization should be minimized by daily washing, debridement of necrotic tissue and antibiotics when indicated. Healing by secondary intention involves the wound’s progression through granulation tissue formation, epithelialization and contraction.

Suturing Techniques

The commonly used suturing techniques are illustrated in Figure 2.1 and described below. Some important points are applicable to all the techniques. The tissue should be entered as close to 90° as possible. The path of the needle should follow its curve. The suture should be pulled forward through the tissue as gently as possible. These steps will help minimize trauma to the tissues.

• Simple interrupted sutures are used to achieve optimal wound edge alignment. This technique is quick and easy to master. It is ideal for most traumatic lacerations. Nylon sutures are commonly used. Knots should never be tied tightly since the tissue can swell and undergo pressure necrosis under the suture.

• Continuous running (over and over) closure is the most rapid suturing technique; however it is difficult to achieve precise edge alignment when tension is present. In tension-free regions it can be used with a good cosmetic result. It is useful for achieving hemostasis (e.g., in scalp lacerations). If additional hemostasis is required, the stitch can be locked.
• Vertical and horizontal mattress sutures provide good wound edge eversion. They are an excellent choice for use in the hands and feet, or in areas of high skin tension.
• Half-buried mattress sutures are useful for closing V-shaped wounds. The mattress portion is horizontal, and the buried portion is placed in the dermis of the tip in order to prevent necrosis of the tip of the V.

• Subcuticular sutures are running, intradermal sutures that can provide an excellent cosmetic result by eliminating any surface sutures and the potential epithelial tracking that can result in a permanent suture mark. PDS or other absorbable sutures with low reactivity can be used if suture removal is problematic, such as in young children. If suture removal is an option, Prolene is a good choice since it has minimal tissue reactivity and should be left in place for 2-4 weeks.

• Buried, deep dermal sutures are used to decrease skin-edge tension and to allow the superficial closure to be done as tension-free as possible. Generally, absorbable sutures such as Vicryl are used in an interrupted manner to close the deep dermis.

• Staples are useful for closing wounds in a variety of situations, such as lacerations or incisions of the scalp. The main advantage that staples offer is that they provide the quickest method of incision closure, and they produce minimal tissue reactivity if removed within a week. However, if left in place too long, staples will produce a characteristic “railroad-track appearance” due to migration of epithelial cells down the tract created by the staples. In addition, precise wound edge alignment is difficult to achieve with staples. Therefore, staples should not be used on visible sites such as the face and neck. They are appropriate for use in reconstructive cases in which precise wound closure is of lesser importance. They can be removed as early as 7 days in straightforward, tension-free closures, or they can be left in place for several weeks if suboptimal wound healing is expected.

Choice of Suture Material

A number of factors should be taken into consideration when choosing suture material:

• Absorbable or nonabsorbable. An absorbable suture will lose at least half its tensile strength by 60 days. This half-life can range from 7 days for catgut to 4 weeks for PDS. The absorption of plain and chromic catgut is very unpredictable. Synthetic, absorbable sutures have a more predictable absorption length, ranging from 80 days for Vicryl to 180 days for PDS. With few exceptions, sutures should not be left in the skin permanently unless they are absorbable. Table 2.1 summarizes some of the commonly used sutures and their characteristics.

• Tensile strength. The strength of a suture is determined by the material of which it is comprised and by its diameter. Among the nonabsorbable sutures, polyester sutures are the strongest, followed by nylon, polypropylene and silk. For absorbable sutures, the order is polyglycolic acid, polyglactin and catgut. Suture diameter is indicated by the USP rating which gives a number followed by a “zero,” with the higher number indicating a thinner suture. Although a larger diameter suture is stronger, it will also cause greater tissue reactivity and leave a more noticeable scar. Therefore, the thinnest suture that is of adequate strength should be used.

• Mono- or multifilament. Monofilament sutures, such as Prolene, are smooth and pass easily through tissue. They cause the least tissue reactivity and trauma and are more difficult for bacterial adhesion. The drawback is that they are difficult to handle compared to multifilament sutures such as silk. In addition, knot security, which is proportional to the coefficient of friction of the suture, is usually greater in multifilament sutures, especially those that are braided. The lower the knot security, the more throws are required to create a secure knot.

• Needle types. There is no uniform nomenclature that describes the characteristics of the needles. A simplified approach is to classify needles as tapered, cutting or reverse-cutting. Tapered needles minimize trauma to the tissue. They are used to suture tissue that is fragile and can tear easily. Examples include cartilage and bowel wall. Cutting and reverse-cutting needles are typically used in closing dermis, with the latter being more commonly used due to the creation of a tract that is less likely to tear through the skin.
• Suture removal. The optimal timing for removal of sutures varies widely from surgeon to surgeon. Sutures that are left in place too long can lead to epithelial tracking down through the skin along the length of the suture. This may result in punctate scars left from the sutures themselves. In cases in which impaired wound healing is expected and cosmesis is of secondary importance, sutures can be left in place for weeks or even months. The following is a guideline for the timing of suture removal:

Eyelids → 3-5 days Face → 5-7 days Breast → 7-10 days Trunk → 7-10 days Hands → 10-14 days Feet → 10-14 days

Considerations in Wound Healing and Scar Formation

Important factors that contribute to a worsened scar outcome include:

• Tension on the closure
• Infection
• Delayed epithelialization
• Imprecise alignment of the wound edges
• Impaired blood flow to the healing scar
• Genetic factors beyond control

By minimizing these factors, an incision will heal more rapidly and the resulting scar will be more cosmetically acceptable.

• Tension on the closure should always be minimized. Closure of the deeper dermis with absorbable sutures will help reduce tension. Whenever possible, incisions should be placed in lines of election. These are the natural creases of minimal skin tension corresponding to wrinkle lines. They are also known as relaxed skin tension lines (RSTL). In the face they usually lie perpendicular to the direction of pull of the muscles of facial expression. If the edges of a wound cannot be brought together without undue tension, undermining or creation of a flap is required. Undermining of the wound edges should be performed with extreme care in order to avoid compromising blood supply. Techniques for creating surgical flaps are discussed in detail elsewhere in this book.

• Infection is of greatest concern in areas of poor vascularity such as the extremities. The face and scalp, in contrast, rarely become infected due to their robust blood supply. In general, wounds older than 12 hours should not be closed. This rule can often be violated when dealing with uncontaminated facial lacerations. Grossly contaminated wounds, such as human bites, are at high risk of developing an infection and are not usually closed primarily. Devitalized tissue should always be debrided from all wounds since it will become a nidus for infection. Pulse lavage of wounds is probably the single most effective method for decreasing bacterial count. Either normal saline or an antibiotic solution can be used. Systemic antibiotics should be used with care. A single dose of preoperative antibiotics is usually indicated. In routine clean cases, there is little evidence to support the use of antibiotics beyond the first 24 hours postoperatively. A patient who presents to the emergency department with a wound requiring surgical repair should probably receive a dose of intravenous antibiotics and his tetanus status should be determined.

• Delayed epithelialization has been shown in many studies to delay overall wound healing and to worsen scar outcome. The presence of a foreign body will interfere with epithelialization; therefore all wounds should be explored carefully prior to closure. Infection will also delay epithelial migration. Finally, there is mounting evidence that moist wounds epithelialize faster and heal better. A moist healing environment is achieved by occlusion of the incision with a semi-permeable, occlusive dressing such as a Steri-strip®. Such a dressing should be used for the first week postoperatively. Under optimal circumstances, an incision will epithelialize within the first 24 hours.

• Improper wound edge alignment occurs during primary closure. It can be minimized by ensuring that the suture traverses the dermis on each side of the incision at the same depth. Once the wound is completely closed, the edges should appear tightly apposed and maximally everted. In irregular wounds, such as stellate-shaped lacerations, one must take care to properly match the two sides. Initial closure of the apex of the laceration can help the pieces properly fall into place.

• Impaired blood flow will prevent the wound from receiving adequate oxygen, nutrients, growth factors and the essential cells involved in the wound healing and scarring process. Little can be done to improve blood flow during primary closure; however a number of factors will worsen it. Smoking has been shown to worsen ischemia in healing wounds by vasoconstriction. External pressure on the wound greater than capillary perfusion pressure (>35 mm Hg) must be avoided. Care should be taken whenever placing circumferential bandages, compression dressings or casts. In addition, sutures that are placed too close to one another can also create areas of ischemia. Other factors that have an unclear effect on scarring, but will impair wound

healing, include elevated blood glucose levels, poor nutritional status, venous and lymphatic insufficiency, chronic corticosteroid use, and a variety of comorbid conditions. Finally, genetics play a definite role in scarring as illustrated by the fact that certain ethnic groups and families have a predisposition to hypertrophic scarring and keloid formation.

The “Dog-Ear”

In certain instances, misaligned closure of a wound can result in a bunching or outpouching of skin termed a “dog-ear.” This will commonly occur when closing oval or circular defects. The “dog-ear” can be excised at its base; however this will result in a scar that is longer than the length of the original defect (Fig. 2.2). In some cases a “dog-ear” will settle with time or can be treated at a later time if it becomes bothersome to the patient.

Z-Plasty

The Z-plasty is a technique that can be used to help prevent scar contracture, or more commonly, as a method of treating scar contracture. Essentially, two interdigitating triangular flaps are transposed resulting in: (1) a change in the orientation of the common limb of the Z; and (2) a lengthening of the common limb of the Z (Fig. 2.3). The change in orientation can be used for managing wounds, in which direct closure may result in undue tension and distortion of nearby structures, such as in the face. The gain in length can be used for treating contracted scars.

Both the length of the transverse limbs and their angle with the common limb can be varied. First, the greater the angle, the greater the amount of lengthening that will occur. A 45° angle will lengthen the common limb up to 50%, and a 60° angle up to 75%. The angles should generally not exceed 60° since excessive transverse shortening and tension will occur. Second, the limb length is determined by how much tissue is available on either side: the more tissue is available, the longer the limbs can be.

Planning the Z-Plasty

When releasing scar contracture, the Z-plasty is created as follows:

1. The common limb of the Z is drawn along the length of the scar. The parallel, transverse limbs are drawn at 60° to the common limb.
2. The skin is incised along the Z shape, and any contracted scar is also incised.
3. Vascularity to the tips of the triangles must be maintained, since they are at the highest risk of necrosis. This is achieved by maintaining a broad base to the triangles, keeping the flaps as thick as possible, avoiding undue transverse tension and handling the tissue with care.
4. The triangles are transposed, resulting in a reorientation of the transverse limbs

and a lengthening of the common limb. When reorienting the direction of a facial scar, the Z-plasty is created as follows:

1. The common limb of the Z is drawn along the length of the scar. The new direction of the common limb is planned so that it will lie in a natural skin crease such as the nasolabial fold.
2. The parallel, transverse limbs should extend from the ends of the common limb up to the skin crease in which the new common limb will lie.
3. The skin is incised along the lines of the Z and the triangles are transposed. If the blood supply to the tips of the flaps is robust, such as in the face, tip necrosis will not occur and angles more acute than 60° can be used.

Patient Selection

The ideal candidate is one with a pronounced wrinkle pattern. In such individuals, the scar can be reoriented to lie in a pronounced line of election. Children, with their lack of wrinkles are not good candidates for Z-plasties on the face. If the original scar is markedly hypertrophic, the use of a Z-plasty is questionable. Scars that cross a hollow (bridle scars), such as the angle of the jaw, are also amenable to Z-plasty.

Multiple Z-Plasties

A single Z-plasty is limited by the transverse shortening resulting from reorientation of the transverse limbs of the Z. This creates lateral tension that is concentrated most heavily at the apices of each triangle. The use of multiple Z-plasties can provide the same degree of scar lengthening while significantly limiting the amount of transverse shortening. In addition, when a scar is very long and would require enormous transverse limbs, multiple Z-plasties with shorter limbs may be more appropriate. In practice, multiple Z-plasties are usually performed with their common limbs as one continuous unit.

Pearls and Pitfalls

The choice of wound closure technique and suture material vary widely. The goal remains the same: achieving a tension-free closure with clean skin edges that are well approximated. The following questions are useful to address before attempting to repair most types of lacerations, especially in the acute-care setting:

1. Are there other potential life-threatening injuries that must be dealt with first?
2. When did the wound occur and what was the mechanism? Is there gross contamination, or is the risk of infection too great to allow primary closure?
3. Has the patient received prophylactic antibiotics and a tetanus shot (when indicated)?
4. Has all devitalized tissue been excised and have all foreign bodies been removed?
5. Can the wound be closed primarily without excess tension? Is there a role for undermining or creation of a flap?
6. What suture material should be used and which suturing technique should be chosen?
7. Which points match up in order to recreate the pre-injury anatomy?
8. Have the wound edges been adequately approximated?
9. Will the dressing provide adequate occlusion? Is it too tight or will it be too tight if postoperative swelling occurs?
10. Has the patient received proper postoperative counseling (how to keep the wound clean, when to get it wet, which activities to avoid, when to follow up, and what the signs of a wound infection are)?
11. When should the sutures be removed?
12. Long-term: Is the final outcome acceptable? Is scar revision necessary?

Suggested Reading

1. Furnas DW, Fisher GW. The Z-plasty: Biomechanics and mathematics. Br J Plast Surg 1971; 24:144.
2. Karounis H, Gouin S, Eisman H et al. A randomized, controlled trial comparing long-term cosmetic outcomes of traumatic pediatric lacerations repaired with absorbable plain gut versus nonabsorbable nylon sutures. Acad Emerg Med 2004; 11(7):730-5.
3. McGregor AD, McGregor IA, eds. Fundamental Techniques of Plastic Surgery, and Their Surgical Applications, 10th ed. New York: Churchill Livinstone, 2000.