Surgery

Fernando Soares Vannucci Braz*
Angelo Bustani Loss*
Ricardo Miguel Japiassú*

Wound Healing and Scarring - Sutures

Introduction

The evolution of wound care and antisepsis in the 18th and 19th centuries changed surgery as dramatically as the discovery of anesthesia. Even so, poor healing, infection and excessive scarring continue to be leading causes of morbidity and mortality.

Nowadays, a detailed knowledge of the basic mechanisms of healing and scarring allows surgeons to influence it, and prevent problems of incomplete or excessive repair.

Wound Healing and Repair

Just after a surgical incision, a number of epithelial cells and connective tissue cells die and the basement membrane is disrupted. This clean and uninfected injury is enough to target an inflammatory response that will be absolutely necessary for the wound healing. Immediately after the incision, the wounds covered with clotted blood containing fibrin and blood cells. This fibrin clots receives within 24 hours an amount of neutrophils, attracted by inflammatory factors locally released. At this time, we also have mitotic activity of the basal layer of the epidermis. By the day 3, macrophages are the most common cells in the tissue, instead of neutrophils. The main feature at this moment is the granulation tissue, that consists of fibroblasts and new capillary with amorphous substance all around. By the 5th day, granulation tissue and neovascularization are maximal. Collagen fibrils are present and begin to bridge the incision, following the epithelial migration. After 1 week there is still connective tissue proliferation, but inflammatory features have virtually disappeared. At the end of the first month, the scar is completed within an intact epithelial layer, covering a new cellular connective tissue net, devoid of inflammation.

In some instances, the wound (not surgical ones) has a large loss of cells and tissues, which makes the normal healing event impossible. In this case, we have the healing by second intention. This is characterized by a more complicated process with much more inflammation and granulation tissue. The original architecture is never attained and the main feature of the phenomemon is called “wound contraction”. The wound contraction is caused, at least in part, by the presence of myofibroblasts ¾ altered fibroblasts that have ultrastructural characteristics of smooth muscle cells.

As noted, the disposition of connective tissue matrix, specially collagen, its remodeling into a scar and the acquisition of wound strength are the ultimate effects of the repair.

The wound healing process is influenced by many systemic and local host factors. Nutrition state of the patient is very important. Protein deficiency and particularly ascorbic acid deficiency inhibits collagen synthesis and impairs healing. Glucocorticoids therapy, by its anti-inflammatory aspects, retards healing. Patient’s age is also an systemic factor that plays a role. Local infections are important causes of complicating and delaying healing process. Hemorrhagic factors, such as ischemia, play a role and foreign bodies, such as sutures and/or other fragments constitute impediments to healing.

The healing process may occur abnormally. There are many aberrations of growth, but the most common is called keloid. Keloid is a tumoral scar resulted from accumulation os excessive amounts of collagen. The reasons for keloid formation still remain unknown, but is known that it’s more common in afro-caribbeans.

Healing of Specialized Tissues

NERVES: The brain largely through connective tissue scar formation in which glial and perivascular cells seem to differentiate into fibroblasts. When a peripheral nerve is severed, the distal nerve degenerates. The axon then regenerates from the nerve cell through the rejoined sheaths, but unfortunately, individual neural sheaths don’t seek out their original distal ends, reconnecting randomly. Recent advances in growth factor technology and the ischemic nature of wounds suggests that something may be done to improve nerve regeneration.

INTESTINE: Anastomosis of the colon and esophagus are precarious and likely to leak, whereas leakage of stomach or small intestine are rare. Intestinal anastomosis usually regain strength rapidly. However, the surrounding intestine participates in the reaction of the injury, losing a large portion of its collagen by lysis, and consequently loses strength, for this reason, leakage is about as likely to occur a few millimeters from the anastomosis. Local infections, which often occurs near esophagus and colonic anastomosis, promotes lysis and delay synthesis, thus increase the likelihood of perforation.

Adhesions are assumed to be an almost inevitable consequence of abdominal surgeries. The most powerful stimuli are ischemic, abscesses and foreign bodies. All attract macrophages which are activated to generate a fibrotic process. Peritoneum normally produces plasminogen activator factor, which quickly leads to fibrin lysis, decreasing the occur of adhesions.

BONE: Unlike healing of soft tissues, bone healing has features of degeneration, and bone often heals without leaving a scar. Once the fracture has been bridged by new bone, it remodels in response to the mechanical stress against it, with restoration to normal or near normal strength. However, it cannot correct deformities of angulation or rotation in misaligned fractures. Careful and correct fracture reduction is still necessary.

Bone repair can be manipulated by electrical stimulation, growth factors and distraction osteogenesis are three promising new tools for this purpose. The Ilizarov technique of distraction osteogenesis can lengthen bones, transport bones across a defect, or correct defects of angulation. An external fixator is attached to the bone through metal pins or wires, creating a surgical break, slowly pulling the bone apart or reangulating it.

Gene Therapy in Wound Healing

Gene therapy will have, in a very near future, an important impact in the wound healing process, specially on the area of plastic and reconstructive surgery procedures that encompass skin grafting, nerve and muscle repair and vessel anastomosis. It has the potential for significantly improving the clinical outcome in this areas by selective expressing genes of interest at sites of injury. This approach involves the transfer of growth factor genes to cells, which can result in localized and continuous expression of their recombinant proteins.

Applications of gene therapy to wound healing can take two general approaches. The first is to use genetically engineered keratinocytes or fibroblasts to over express growth factor genes (PDGF, TGF-b, platlet factor 4 and others). These cells can then be re-implanted back to the wound area, expressing factors for a prolonged time. This method may have applications in enhancing skin regeneration after burn injury and for the treatment of genetic skin disease. Other possibility is to transfer DNA directly into skin. This can be accomplished by using the gene gum or by direct subcutaneous injection of DNA into skin.

Chronic Wounds

The first principle in managing chronic wounds is to diagnose and treat any underlying circulatory disease. The second principle is never to allow open wounds to dry. A third principle, but not less important, is to control any infections with adequate care of the lesion and systemic antibiotics. Finally, its also necessary to recognize that chronically scarred tissue is usually poor perfused. Debridement of unhealthy tissue, often followed by skin grafting, may be required for healing.

Sutures

The ideal suture material should be flexible, strong, easily tied and securely knotted. It would excite little tissue reaction and would not serve for nidus for infection.

STAINLESS STEEL WIRE: is inert and maintains strength for a long time. It does not harbor bacteria.

SILK: animal protein, relatively inert for human tissue, loses strength over long periods. Silk sutures are multifilament and provide a potential haven for bacteria.

CATGUT: from the submucosa of the bovine intestine, eventually resorb. It excites considerable inflammatory reaction and tends to potenciate infections. It loses strength rapidly and it’s of little use in modern surgery.

SYNTHETIC NONABSORBABLE SUTURES: generally inert and retain strength longer than wire. They must usually be knotted at least four times because of their poor handling characteristics, resulting in retained foreign bodies.

SYNTHETIC ABSORBABLE SUTURES: strong, with predictable rates of loss of tensile strength, incite a minimal inflammatory response and may have special usefulness in gastrointestinal urologic and gynecological surgeries.

TAPES: skin closure of choice for clean or contaminated wounds, with minimal probability of infections. They cannot be used in actively bleeding or complex surface wounds.

Wound Closure

The ideal closure of small wounds in healthy patients is with fine interrupted sutures placed loosely and coveniently close to the wound edge. In abdominal wounds, the peritoneum need not to be sutured but posterior and anterior fascia are sutured with nonabsorbable or slowly absorbable sutures.

Unfortunately, surgeons often must operate on patients who have impaired wound healing capacity. In this cases, sutures must be stronger enough to avoid deluscence. Sutures placed too tightly and too close together obstruct blood supply to the wound, causing ischemia in this area.

Problems of Scar Formation

Surgeons confront the consequences of excessive scar formation daily. Skin incisions heal scar, and sometimes pathologic process such as keloid and hipertrophic scars are the unanticipated sequelae (see Table 1). Abdominal surgery invariably leads to intraperitoneal fibrous adhesion and mechanical intestinal obstruction can result. Stricture occurs at anastomotic sites like bowel, blood vessels, trachea, ureter, or bile duct.

An understanding of fetal wound healing may lead to therapeutic strategies to help avert scarring and fibrosis. Healing without scar will have a tremendous impact on both medical and surgical practice. Probably in the future, gene therapy, as explained above, will become the standard treatment of enhancing wound healing.

Bibliography

1. Current; Surgical Diagnosis & Treatment; 10th ed.; Chap. 7; 80-94.

2. Gene therapy for plastic and reconstructive surgery; Clinics in Plastic surgery; vol. 23; number 1; January 1996; 157-68.

3. Robin’s; Pathologic Basis of Disease; 5th ed.; Chap. 3; 51-92

4. Sabinston’s; Textbook of Surgery; 15th ed.; Chap. 12; 207-22

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