Basics of Wound Closure and Healing
Wayne W. LaMorte, M.D., Ph.D., M.P.H.
There are many circumstances in which sutures are used to repair tissue and facilitate healing. The techniques that you use, the suture material you use, and the specific type of needle you use will vary depending on whether you are closing a simple laceration on the foot, a complex laceration on the face, a gastrointestinal anastomosis, a vascular anastomosis, or closing a median sternotomy.
Tissue Response to Injury: Three Phases of Healing
- Hemostasis and Inflammation
- Wound Maturation
There is considerable overlap among these phases.
Phase I – Hemostasis and Inflammation
Illustration from the Ethicon Wound Closure Manual
With vascular disruption there is transient vasoconstriction, followed by vasodilatation and increased capillary permeability. Contact of platelets with collagen and ground substance causes activation and aggregation of platelets. The intrinsic and extrinsic coagulation cascades are triggered, and chemotaxis attracts inflammatory cells.
Neutrophils, which are the first nucleated cells to come into play, initiate phagocytosis and antimicrobial defense, but by the 3rd or 4th day macrophages have replaced the neutrophils as the dominant cell type.
Macrophages play a central role in wound healing. They remove microbes and cellular debris through phagocytosis and enzymatic breakdown of the extracellular connective tissue matrix, and they elaborate cytokines which stimulate angiogenesis and fibroplasia.
Phase II – Fibroplasia
The inflammatory response abates as the inflammatory stimuli are removed, and the fibroplastic phase is usually well established by the 5th day. There is fibroblast migration and proliferation that is mediated by a variety of chemotactic factors and growth factors (e.g., fibronectin, C5A, PDGF, and FGF). As fibroblasts populate the wound, they begin to synthesize and secrete proteoglycans, collagen, and elastin.
There is then a gradual decrease in the size of the wound as a result of wound contraction. In response to angiogenic stimuli, new capillaries invade the wound and enlarge. At the same time, epithelial cells behind the wound edge proliferate and there is migration of the epithelial cells across the collagen and ground substance at the surface of the wound.
Phase III – Maturation
The maturation phase involves remodeling of the wound as a result of an interplay between matrix synthesis and degradation. Cross-linking of collagen also occurs, and over time there is a progressive increase in tensile strength.
- At 2 weeks the wound has achieved about 20% of its pre-wound strength.
- By 5 weeks it is at about 50%.
- By 10 weeks it is at about 80% of pre-wound strength.
- Remodeling and maturation of the scar will continue for a year or more.
The Principles of Wound Closure are Dictated by the Biology of Healing
- Minimize bacterial contamination: Bacterial contamination can be reduced by irrigating the wound with large amounts of sterile saline or Ringer’s solution under moderate pressure. One method is to use a 50 cc syringe with a 16 or 18 gauge needle. Sterile saline can be aspirated, and a pulsatile irrigating stream can be created by depressing the plunger with force. Small wounds with little contamination can be irrigated with 100-200 cc of saline, but larger volumes should be used for larger or more contaminated wounds. Generally, antiseptics should not be used to irrigate wounds, because they impair wound healing.
- Remove foreign bodies & devitalized tissue.
- Achieve hemostasis (blood is a culture medium).
- Handle tissue gently. Use fine-toothed forceps such as an Adson forceps; do not use smooth forceps, since these crush tissue because they require greater pressure to grasp.
- Approximate; don’t strangulate. The wound edges should just be approximated. Sutures that are too tight accentuate cross-hatching and cause ischemia of the wound edges, increasing the risk of infection.
Handle Tissues Gently!
The goal of wound closure is to achieve healing with:
- No infection
- Normal function
- An excellent cosmetic result
These goals are facilitated by handling tissues gently. As early as the 1500s a barber- surgeon named Ambroise Paré demonstrated the importance of gentle handling of tissue.
Ambroise Paré (1520-1590)
Paré was an astute observer and brought many innovations to surgery and wound care. One of the most important concepts he introduced was that wounds should be treated gently to reduce inflammation and promote healing. For a significant part of his career Ambroise Paré was a barber surgeon in the army of the king of France. He abandoned the traditional treatment of cauterizing wound after his experience in the battle of Turin in 1536, when the French fought the Italians.
Paré doubted the appropriateness of pouring boiling oil into a gunshot wound, but when he had polled the other surgeons, he found that they all used the method of Vigo, and he began using this method himself. However, there were many wounded in the battle of Turin, and Paré ran out of oil. Consequently, he dressed the remaining wounds with a salve that he made with egg yolks, oil of roses, and turpentine.
In Paré’s words:
“In this conflict there were many wounded on both sides with all sorts of weapons, but chiefly with bullets. I will tell the truth, I was not very expert at that time in matters of surgery; neither was I used to dressing these wounds made by gunshot. Now I had read in John de Vigo that wounds made by gunshot were poisoned … [and] for their cure, it was expedient to burn or cauterize them with scalding hot oil, with a little Treacle [theriac] mixed in.”
“I could not sleep all that night, for I was troubled in mind, and the dressing of the precedent day (which I judged unfit) troubled my thoughts; and I feared that the next day I should find them dead, or at the point of death by the poison of the wound … [those] I had not dressed with the scalding oil. Therefore I rose early in the morning, I visited my patients, and beyond expectation, I found such as I had dressed with [the salve] only … to have had a good rest, and that their wounds were not inflamed, or tumified; but on the contrary the others that were burnt with the scalding oil were feverish, tormented with much pain, and the parts about their wounds were swollen. When I had many times tried this in diverse others … , I thought that neither I nor any other should ever cauterize any wounded with gunshot.”[from “The Apology and Treatise of Ambroise Paré”]
As a result, Pare became a champion of treating wounds gently. Paré said, “I dress the wounds, God heals them.”
Most sutures come as a single piece, with the suture material swaged onto the base of the needle. The needle should be grasped in the tip of the needle holder about 2/3 of the way back from the point. Grasping further back at the swaged end tends to weaken the needle and its attachment to the suture, and you are likely to bend the needle.
There are many different needle types, but the chief distinction to be made here is the difference between taper or “smooth” needles in contrast to cutting needles. Taper needles do just what their name implies: they gradually taper to the point, and a cross-section anywhere along the shaft would reveal a round shaft, as shown in the inset. Taper needles are used for tissue that is easy to penetrate, such as bowel or blood vessels.
In contrast, the tip of cutting needles is triangular in shape, and the apex forms a cutting surface, which facilitates penetration of tough tissue, such as skin. Cutting needles make it much easier to penetrate tough tissue. Penetrating skin with a taper needle is very difficult and causes excess trauma to the skin because of difficulty in penetration and the need to grasp the skin edge very tightly with forceps. Consequently, you should never use taper needles to suture skin.
The reverse cutting needle is similar to a conventional cutting needle, except that the cutting edge faces down instead of up. This may decrease the likelihood of sutures pulling through tissue in some cases.
Non-absorbable sutures are made of materials that are not readily broken down by the body’s enzymes or by hydrolysis. There are naturally occurring non-absorbable materials e.g., silk, cotton, and steel) and synthetic non-absorbable materials (e.g., nylon and Prolene, Mersilene). In some cases they are left in place indefinitely (e.g., when used to close the abdominal fascia), and in other cases they are removed after adequate healing has occurred (e.g., nylon sutures to close a superficial laceration).
Absorbable suture materials are those that are broken down. The original absorbable suture materials were plain and chromic “cat gut,” which actually consisted of processed collagen derived from the submucosa of animal intestines. Plain gut is broken down enzymatically after about 7 days. Chromic gut is collagen treated with chromium salts to delay break down. Chromic gut typically loses its strength after 2-3 weeks is completely digested after about 3 months. Now there are many synthetic absorbable materials made from polymers (e.g., Vicryl and Monocryl). These materials are broken down non-enzymatically by hydrolysis; water penetrates the suture filaments and causes breakdown of the polymer chain. As a result, synthetic absorbables tend to evoke less tissue reaction than plain or chromic gut.
[Graphic taken from the Ethicon Wound Closure Manual]
Vicryl retains 75% of its original tensile strength at 2 weeks and retains 50% at 3 weeks. Monocryl retains 60-70% of its strength at 1 week and 30-40% at 2 weeks. PDS II is a soft, pliable monofilament material that retains about 50% of its strength at 4 weeks after implantation.
Monofilament versus Multifilament:
It should also be noted that some of these suture materials consist of a single smooth strand (monofilament) and others consists of multiple fibers woven together (multifilament). Characteristically, multifilament suture material (e.g., silk or Mersilene) tends to be easier to handle and tie, and knots in multifilament material are less likely to slip. On the other hand, monofilament materials (e.g., nylon or Prolene) are less traumatic, since they glide through tissues with less friction, and they may be associated with lower rates of infection.
Since monofilament materials are more likely to slip, one generally ties knots with 5 or 6 “throws” when using monofilament materials (in contrast to 3 throws with silk or Mersilene). Despite the greater number of knots required, monofilament materials such as nylon are generally preferred for skin closure because they stimulate less tissue reaction, are less traumatic, may have less likelihood of infection, and provide a better cosmetic result.
Among the absorbable suture materials, Vicryl is a multifilament material, but there is also a coated Vicryl that provides decreased drag through tissue. For this reason, coated Vicryl is used by some surgeons for the interior layer of bowel anastomoses. Monocryl is an absorbable monofilament material, but has excellent pliability and provides easy handling and good knot security.
Basic Skills: Use of Forceps and Needle Holder
Surgical Skills Lab for first and second year medical students.
The most commonly used scalpel blades are the #10 and the #15 blade. The #10 blade is better for long, straight incisions, and is held with the shaft of the scalpel in the palm of the hand with the index finger on top of the blade.
The smaller #15 blade is well suited for short, tortuous incisions; for this type of incision holding the scalpel as if it were a pencil may facilitate control.
For skin closure use a fine-toothed forceps, such as an Adson forceps. The forceps should be held so one arm is an extension of thumb and the other is an extension of your index finger. The base of the forceps should rest on the dorsal surface of the web space between the thumb and index finger.
Use only forceps with teeth. Use the arm with a single tooth to gently elevate the skin edge. Avoid crushing the skin edges with the forceps. This further traumatizes the wound edge and impedes healing.
The forceps allow you to create counter traction and control the position of the skin edge to facilitate passage of the needle perpendicularly through the skin.
The forceps should also be used to grasp the needle when repositioning it in the needle holder. You should never touch the needle with your fingers.
Instead of using forceps, the skin edges can also be controlled using skin hooks, which have the advantage that they do not crush the skin edge.
There are several techniques for holding the needle holder. The most common method is to place the thumb and ring finger slightly into the instrument’s rings. This allows you to pronate and supinate and to open and close the jaws of the needle holder. Avoid inserting your fingers far into the rings of the instrument, since this will tie up your fingers and impede your mobility. Some surgeons do not put their fingers into the rings at all and simply grasp the rings and body of the needle holder in the palm of their hand.
Remember to create right angles:
The ideal skin suture should form a rectangle, penetrating the epidermis and dermis perpendicular to the skin surface, then turning at a right angle to traverse the depth of the wound parallel to the skin surface, and then turning again to emerge from the opposite skin edge perpendicular to the skin surface.
The distance between the skin edge and the emerging suture should be the same on both sides of the wound. When tied, a suture placed in this fashion will form a rectangle and will provide optimal approximation of the wound edges.
Getting the suture path to follow the rectangular course described above may seem counterintuitive, since the needle is curved. However, a rectangular path can be achieved by taking advantage of the needle’s curvature and rotating the needle in such a way that the body of the needle stays perpendicular to the skin. Think of the skin as the tangent to the arc formed by the needle; in this case, the tangent is stationary and the arc rotates.
Coordinated use of the forceps and needle holder:
Efficient and atraumatic placement of sutures which follow the rectangular path described above requires coordinated use of the forceps and needle holder. One can best take advantage of the natural curvature of the needle by alternately pronating and supinating the hand with the needle holder.
The tip of the needle holder should grasp the needle about 2/3 of the way back from the point. The needle holder and needle should be roughly perpendicular.
The far skin edge is elevated with the forceps in the left hand, while the right hand is pronated to “cock” the needle in preparation for taking the first “bite”. The tip of the needle should penetrate the skin perpendicularly about 5-10 mm from the wound edge, and the needle should be rotated all the way through the epidermis and dermis by supinating the right hand to rotate the needle through its arc.
A Key Maneuver:
The tip of the needle should now be seen protruding into the wound from the subcutaneous tissue. At this point, it is important to maintain the position of the skin edge using the forceps. A common error here is to release the forceps from the skin edge, but this allows the skin to retract, and the needle may move and retract beneath the skin edge.
The key is to maintain the position of the skin edge while releasing the needle from the needle holder. This will maintain the position of the needle tip. After the needle is released from the needle holder, the right hand should be fully pronated before regrasping the needle. The “bite” can then be completed by supinating the right hand in order to complete the rotation of the needle through the skin.
If it is necessary to reposition the needle in the needle holder before taking the second “bite,” the needle should be grasped with the forceps, not with your fingers.
The forceps then elevate the near skin edge in preparation for the second “bite.” Once again, the right hand is cocked by pronating it, and the needle is passed upward through the near skin edge by supinating the right wrist in order to keep the body of the needle perpendicular to the tissue it is passing through at all times. The needle should emerge about 4-5 mm from the wound edge (equidistant on both sides of the wound).
Scissors are generally held with the thumb slightly in one ring and the ring finger in the other. The index finger stabilizes the instrument by resting on the shaft.
When cutting sutures, some recommend sliding the tips of the scissors down the strands to the point where they will be cut, but it probably makes more sense to simply move the tips of the scissors directed to the point where the cut will be made. For external non-absorbable sutures it is important to leave 4-5 mm “ears” to facilitate suture removal.
- Face: 3-4 days
- Scalp: 5 days
- Trunk: 7 days
- Arm or leg: 7-10 days
- Foot 10-14 days
Many patients are very apprehensive about suture removal, so the first step is to reassure the patient that the procedure is not painful. The skin should be cleansed. Hydrogen peroxide is a good choice for gently removing dried blood and exudate.
Then grasp one of the “ears” of the suture with a forceps to elevate the suture just enough to slip the tip of a small scissor under the suture in order to cut it. This should be done close to the skin edge in order to minimize the amount of contaminated suture that will be dragged through the stitch path. The suture is then gently removed by pulling with the forceps. It is frequently a good idea to reinforce the wound with Proxi-Strips. These are narrow adhesive strips that are placed perpendicularly across the wound at intervals.