Why Scars Form
Why Scars Form
Scars result after substantial injury to the skin such as after deep cuts and scrapes, abrasions, moderate to severe burns, animal bites, skin blemishes or infections, surgical procedures and more. Scars can cause both cosmetic and functional concerns for a patient, prompting a desire for revision.
The type of scar that results after injury depends on many factors, including how the wound heals, the area of the body on which the scar is found, the direction in which the scar lies, the age of the person with the scar, and if that person has a history of a scarring disorder.
How the wound is treated (or not)
First, how the wound is treated (or not) will affect how it heals and eventually the quality of the scar that results. Wounds can heal by either primary or secondary intention.
Primary intention occurs when the wound edges are closely brought together usually by stitches or sometimes medical tape or glue. The skin edges touch, allowing fast healing of the area as skin cells from either side migrate across to the other side and seal the wound in about 24-48 hours. This relatively narrow area will become the scar tissue, but can stretch and widen or thicken over time due to many factors.
Healing by secondary intention occurs when wound edges are not or cannot be physically brought together such as in untreated deep gaping cuts, areas of tissue loss, or in deeper abrasions and burns. Because of this, the healing process is delayed as the normal skin edges work to contract in making the wound area smaller while skin cells migrate inward over time to eventually cover the entire surface of the wound creating a healed scar. Although the healed area is usually smaller than the original wound size, the scar tissue is often fragile with color and texture differences from the surrounding skin.
Surgical techniques can work to cut back to healthy skin edges after tissue injury. They can maximize the strength of wound closure by using a layered method with buried sutures as needed, allow healing by primary intention, and can help improve the long term healed appearance of a scar. In pediatric patients, larger areas of open wounds that cannot be closed often heal by secondary intention with surprising efficiency and results. Depending on the depth, size, and location of an open wound injury, techniques such as skin grafting may be recommended to speed healing and minimize scar complication.
Different areas of the body
Different areas of the body will scar differently due to both the tension found at the area and the movement across it. Notoriously, areas such as the mid chest, upper shoulders and back tend to display more widening and thickening of scars than other areas.
The direction of the scar
The direction of the scar also plays a large role in how it appears. Scars that are aligned with natural relaxed skin lines will remain much thinner and less noticeable than scars that travel across those skin lines. In addition, scars that can be placed at the edges of the aesthetic units of the face (such as along the eyebrow or side of the nose), will be much less noticeable than those that fall within them.
A patient’s age
A patient’s age also affects the appearance of scars. Because of the robust healing response in children, scars often heal somewhat thicker and usually maintain their dark pink color longer than those of an adult. Due to tension on the skin with natural growth, healed scars often widen a bit over time than those in adults.
Genetics can play a role in how nicely a scar heals, especially if person has a history of scarring disorders such as keloids or hypertrophic scarring.
Keloids can occur in up to 10% of people, and are more common in people of darker skin color and result from excessive and continued production of collagen during and after wound healing. This causes a raised, nodular appearance to the scar that grows beyond the edges of the original wound. Keloids often form in a delayed fashion. At times they start many months after even small tissue injuries such as an ear piercing or a pimple, and continue to grow larger over extended periods of time sometimes reaching tumor-like proportions. After treatment by excision alone, keloids have a very high recurrence rate (some sources quote over 90%) and therefore treatment by multiple strategies is strongly recommended. Therapies include injection of corticosteroid, silicone sheeting or pressure therapy, and sometimes radiation treatments.
Hypertrophic scars are different from keloids in that they may be thickened and widened, but do not extend beyond the original borders of the wound. They are found more evenly across all ethnic groups and often form in response to delayed healing. This can happen when there is an infection, when deep tissue injury is allowed to heal over an extended time by secondary intention alone, or in response to excessive tension across a wound such as over joints. These scars are often more responsive to conservative treatment such as steroid injections and silicone taping, and do not usually recur after excision as long as the healing conditions are maximized (uncomplicated primary healing under reduced tension).
Despite these factors, with proper scar management and possible revision procedures, aesthetic long term results can be achieved after growth of the scar is complete.
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Regardless of how they heal all scars go through a well defined period of change and maturation which can last over a year. After initial healing, scars begin a process of thickening and contraction as the body replaces and reorganizes the structure of the initial soft tissue fibers (collagen). This process starts around 3 weeks after injury and peaks around 3-6 months, and can cause a scar that was initially subtle to appear darker, thicker, and shortened. Eventually, as reorganization is completed, the scar tissue softens and fades in color as the excess blood vessels in the scar disappear. Mature scars do not usually have equal pigmentation of the normal surrounding skin, and can appear either white or more darkly pigmented (especially in darker skin). Protecting the area from sun exposure, especially during the first year of healing, is important to minimize permanent dark discoloration.
During initial healing, it is important to keep the wound moisturized by either applying either antibiotic or moisturizing ointment 2-3 times a day unless tape strips are covering the wound. Gentle cleansing with hydrogen peroxide and cotton swabs can be used to remove excess blood or crusting. In order to protect the area from repeated trauma, activity restrictions (no sports or gym class) and quieter activity are usually recommended for 3 weeks. As mentioned, new scars are especially sensitive to sun damage, and vigilant protection by avoiding prolonged exposure and using sunscreen and protective clothing is strongly recommended.
In order to quicken the process of scar maturation, and avoid/minimize the period of thickening and contracture, scar massage should be regularly performed usually starting 3 weeks after injury. Short but regular bouts of firm pressure massage to the scar stimulates the body to more efficiently perform scar maturation, avoiding excess tissue firmness, edema, and quicker fading of the pink color. In order to be effective, massage must be firm causing blanching (whitening) of the scar once pressure is removed with total massage time lasting at least 30 minutes every day broken up into short increments (no less than 10 minutes, 3 times/day) during the entire period of active scar remodeling (usually 3-6 months) so the scar is more constantly stimulated. A small amount of moisturizing ointment should be used during massage to keep the tissue lubricated and avoid irritation.
At times, your surgeon may advise not performing scar massage if the incision is in an area difficult to effectively massage or in a region more prone to scar widening than thickening. Although it may take more time for the color of the scar to fade, an experienced pediatric plastic surgeon will make this recommendation in order to minimize the width of the final scar and improve long term outcome. Sometimes, pressure taping of the scar can be used in place of massage and should be kept on continuously, day and night, as much as possible, with replacement after bathing as long as there is no adverse reaction of the surrounding skin. Any unusual appearance or excessive thickening of the scar during healing should prompt a return checkup to allow early diagnosis and treatment of pathologic processes such as hypertrophic scarring or keloid formation.
Before scar revision is undertaken, it is usually important to wait at least one year to allow for complete maturation of the scar. Exceptions may occur when scarring is so severe it decreases the mobility of a joint or threatens protection of a vital structure such as the eye. Although there is no way to remove an existing scar, an experienced pediatric plastic surgeon will often choose from a combination of different surgical techniques to treat your child’s specific scar issues and attempt to improve the overall appearance. Below is a quick description of some of the more common procedures used during scar revision:
Re-excision can be used to remove an area of thickened, widened, or depressed scar and repair it in layers to allow more ideal healing by primary intention. At times, the surgeon will attempt to reorient the direction of the scar into a more favorable direction at the same time. This may require changing the shape of the scar from a line to multiple small zigzags called a W-plasty. This causes the scar to break up with more of it lying along the relaxed skin lines. As it fades it will become less noticeable than the original line.
Linear scars with shortening and tension across them such as those restricting the motion across a joint may require a Z-plasty to reorient the line of the scar and increase its length. By cutting triangular flaps of skin from either side of the scar line and transposing them (switching their position), the overall scar line is broken up and lengthened. This allows for better motion across the area and reduced tension which prevents and treats existing scar hypertrophy.
Excision and replacement
At times, the area of scarred tissue is so extensive it requires excision and replacement to achieve an improved result. Methods such as split or full thickness skin grafting or local flaps with or without tissue expansion can be used to replace an area of skin and tissue, improving the appearance and function of the area. More complex methods of tissue replacement can be used if necessary.
Wound healing and scar revision are complex processes well known to the experienced pediatric plastic surgeon. By using the right combination of techniques from initial care of the wound to scar management and revision, we can work to minimize the disfigurement and functional limitations created by scarring and improve the physical and psychological health of your child.
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