Scar Types

The spectrum of skin scar types

Skin tissue repair results in a broad spectrum of scar types, ranging from a "normal" fine line to a variety of abnormal scars, including widespread scars, atrophic scars, scar contractures, hypertrophic scars, and keloid scars.

Widespread (stretched) scars appear when the fine lines of surgical scars gradually become stretched and widened, which usually happens in the three weeks after surgery. They are typically flat, pale, soft scars often seen after knee or shoulder surgery. Stretch marks (abdominal striae ) after pregnancy are variants of widespread scars in which there has been injury to the dermis and subcutaneous tissues but the epidermis is unbreached. There is no elevation, thickening, or nodularity in mature wide-spread scars, which distinguishes them from hypertrophic scars.

Atrophic scars are flat and depressed below the surrounding skin. They are generally small and often round with an indented or inverted centre, and commonly arise after acne or chickenpox.  

Scar contractures -scars that cross joints or skin creases at right angles are prone to develop shortening or contracture. Scar contractures occur when the scar is not fully matured, often tend to be hypertrophic, and are typically disabling and dysfunctional (fig 4). They are common after burn injury across joints or skin concavities.

Raised skin scars

Raised skin scars are described as hypertrophic or keloid scars.

Hypertrophic scars are raised scars that remain within the boundaries of the original lesion, generally regressing spontaneously after the initial injury. Hypertrophic scars are often red, inflamed, itchy, and even painful. They typically occur after burn injury on the trunk and extremities.

Keloid scars are raised scars that spread beyond the margins of the original wound

Keloids scars are thick, puckered, itchy clusters of scars that spread beyond the edges of the wound or incision and invade the surrounding normal skin in a way that is site specific . They are often red or darker than the surrounding skin. Keloids appear when the body continues to produce collagen long after the initial wound healing has taken place. 

Ear lobe keloids often grow as large lobules, central sternal keloids commonly develop a butterfly shape, and deltoid keloids tend to extend vertically. A keloid continues to grow over time, does not regress spontaneously, and almost invariably recurs after simple excision. It is difficult to apply the term keloid until a scar has been present for at least a year, although there is no precise time interval. Histologically, keloids have a swirling nodular pattern of collagen fibres.

Scars that are difficult to categorise have been termed intermediate scars. However, if a raised scar is still emerging after a year, a true keloid is a potential diagnosis, whereas hypertrophic scars should show some evidence of regression within this time. Keloids may be inflamed, itchy, and painful, especially during their growth phase. Common presentations are in the ear lobe after ear piercing, the deltoid after vaccination, and the sternum after acne, chickenpox, trauma, or surgery. Keloids are unique to humans, and there seems to be some genetic predisposition, with dark skinned races being more prone to them, though there are few large epidemiological studies. They develop predominantly in people aged 10 - 30 years, with an apparent predilection for emergence and deterioration during puberty and pregnancy.

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