Scars resulting from an adequate pathophysiologic response of the skin

Depending on the location and depth of destructive changes, scars can have different clinical manifestations. Thus, a scar that is flush with the skin and does not cause deformation of the skin and underlying tissues is called normotrophic. This is the most common type of scar. Scars of a small area, linear in shape, formed after cut wounds, abrasions, as a rule, have a normotrophic character.

When the injury is located on the surface of the body where the hypodermis is practically absent (the anterior surface of the shin, the back of the feet, hands, the upper part of the anterior chest wall, the temple), a thin, flat, strophic scar with translucent vessels appears, similar to atrophic skin. This type of scars could be classified as normotrophic, since they are also located flush with the surrounding normal skin. However, they are still singled out as a separate group, due to the peculiarities of treatment.

If the injury (burn, inflammation, wound) was located on the surface of the body with a sufficiently developed layer of subcutaneous fat and was deeply destructive, the scar may take the form of a retracted, hypotrophic scar due to the destruction of the hypodermis. Hypotrophic scars are retracted scars that create a depression in the skin relief or the so-called minus tissue (-) tissue. They are formed as a result of deep destructive inflammation or injuries that destroy the mesodermal and hypodermal layers of the skin. They can be single after furuncles, dermatoses with the formation of nodular elements, animal bites, ulcers, unsutured wounds. More often, dermatocosmetologists encounter multiple hypotrophic scars, for example, after deep conglobate acne, chickenpox.

The structure of this group of scars

In the event that a normal physiological scar is formed as a result of the healing of a wound defect, it will have a different histological picture at different stages of its existence. Thus, it can be said that the structure of a group of adequate pathophysiological scars is a dynamic concept. It changes depending on the duration of their existence, the depth of the lesion, the area and localization. This is of significant importance for the appointment of therapeutic measures, since at different stages of maturation of scar tissue, the optimum of their effectiveness will be different.

At the first stages of existence of a scar that has arisen at the site of an injury that heals by secondary intention, it is a loose connective tissue formed from granulation tissue covered with a layer of epidermis. Accordingly, such a scar will contain a large number of cellular elements (leukocytes, lymphocytes, plasma cells, monocytes, fibroblasts, mast cells, etc.), vessels, and intercellular substance. The intercellular substance is represented by glycoproteins, proteoglycans, and glycosaminoglycans. Collagen, elastin, and argyrophilic fibers are present in small quantities. The epidermis in scars of a small area or in scars at the site of a shallow lesion with preservation of skin appendages is thickened due to actively multiplying keratinocytes. It can consist of 15-20 layers of cells, of which the share of awl-shaped cells accounts for the largest number of layers. The stratum corneum is thin - 1-2 layers of cells. The basement membrane is absent. Such thickening of the epidermis occurs due to the release of epidermal growth factor by macrophages and keratinocytes, stimulating the proliferative activity of keratinocytes.

In large-area scars formed at the site of a deep injury that caused the destruction of skin appendages, the epidermis will be dystrophically changed, basal keratinocytes may have a polygonal shape or elongated along the line of connection with granulation tissue. The number of epidermal layers may be significantly reduced. Self-epithelialization of such wounds is often difficult. In this regard, such patients require skin or multilayer keratinocyte grafting. The basal membrane is absent. Scar tissue, along with an abundance of cellular elements, vessels and intercellular substance, may contain a greater number of collagen fibers in the lower parts of the scar.

Incised or postoperative, uninfected wounds heal, as a rule, without complications with thin scars, the epidermis of which, due to the overlap from the edges of the wound, can have a normal thickness. The spectrum of cellular elements is shifted towards macrophages and fibroblasts. Already at the initial stages of scar tissue formation, fibrogenesis processes prevail over fibrolysis, therefore, in the deep sections of the scar, a loose network of collagen fibers is observed.

As the average physiological scar ages, the number of cellular elements, interstitial substance and vessels decreases, while the number of fibrillar protein structures (collagen fibers) of fibronectin increases. The epidermis can gradually acquire normal thickness with a newly formed normal basement membrane. Fibroblasts predominate among the cellular elements, which are the main functional element of connective and scar tissue.

It is believed that scar tissue matures within 6 months. During this time, the loose scar, rich in vessels, cellular elements and intercellular substance, turns into a dense connective tissue structure. This is, in fact, nothing more than a connective tissue "patch" on the skin, but of a smaller area than the previous injury. The reduction in the scar area occurs gradually due to a decrease in its moisture capacity, a decrease in the number of vessels, intercellular substance and contraction of collagen fibers. Thus, the "old" mature physiological scar consists mainly of tightly packed, horizontally located collagen fibers, among which are fibroblasts elongated along the longitudinal axis, single lymphocytes, plasma and mast cells, intercellular substance and rare vessels.

Accordingly, the histological picture changes depending on the age of the scar, its appearance also changes. All young scars, with a lifespan of up to 6 months, have a bright pink color, which gradually fades to white or the color of normal skin over several months.

[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ], [ 7 ], [ 8 ]