The most superficial wounds such as superficial burns and abrasions will heal by epithelialisation alone without scar formation. In these circumstances adnexal structures are preserved and the epithelium regenerates from these structures. This may leave alterations in keratinisation, texture or pigmentation of the healed area, but not scarring as such. A scar is the inevitable consequence of wound repair. The final phase of wound repair is the process of remodelling and scar maturation (Fig. 3.1). The fibroblasts, capillaries, glycosaminoglycans, and immature collagen of granulation tissue and the newly healed wound are replaced by relatively acellular, avascular scar tissue composed of mature collagen with scattered fibroblasts. This biological process is manifested by a change in appearance of the scar from a red, raised, firm, contracting, perhaps itchy nodule to a pale, flat, softer, static, symptomless plaque of mature scar. The rate at which any given scar passes through this process can vary widely depending on the age of the individual, the site of the wound, the time the wound took to heal, the direction of the scar and the tension across it (Fig. 3.13). In general, scars in younger patients with wounds on the trunk that heal slowly, perhaps with infection or dehiscence, and scars that have a lot of tension across them will take much longer to mature than scars in older people, in thin-skinned areas, that heal rapidly by first intention and that have minimal tension across them (Table 3.2). It is important to be aware of this variation in the natural history of scar maturation in order to counsel patients regarding the likely progress and outcome of their scar, advise those having elective surgery what the consequences in terms of scarring will be, and to recognise the various types of adverse scarring which can occur. One of the most frequent types of adverse scar, a hypertrophic scar, is one that remains red, raised, itchy and tender for longer than might generally be expected.
There are many types of adverse scar (Table 3.3), many of which can be avoided or prevented by correct incision planning and adequate wound management. Some types, however, cannot be prevented and are unpredictable in their occurrence. The appearance of some scars can be improved by surgical or other means, but scars can never be removed totally. The types of adverse scar will be discussed and suggestions for avoidance or management made.
Incisions that pass along ideal lines are more likely to leave acceptable scars. There are many types of ‘lines of election’ for incisions, most of which pass along skin wrinkles or along relaxed skin tension lines (that is a line along which maximal skin tension passes when the part is in a relaxed position). These lines have minimal tension across the wound edges. A scar which crosses these lines will have a greater tendency to stretch or become hypertrophic, and even if not hypertrophic will usually appear more conspicuous than one which follows a relaxed skin tension line. Other ideal positions for scars are at junctions between anatomical areas such as the nose and the cheek, the cheek and the ear or the junction between a hairy and hairless area
Poor alignment of features
Where a scar crosses the junction between distinct anatomical features, such as the vermillion of the lip, it is essential that these features are accurately realigned. Such misalignments result in conspicuous adverse scars.
Scars from excisional wounds on the trunk and limbs often stretch. It has been shown that the width of a scar depends on the tension across the wound at the time of wound closure. In general, steps to avoid excessive tension across the wound will be rewarded with narrower scars. Where tension cannot be avoided there is evidence that prolonged wound support with buried nonabsorbable or long-term absorbable sutures can minimise scar stretching.
The process of wound contraction continues in the remodeling phase of scar maturation such that a scar will always be shorter than the incision from which it results. Where a linear scar crosses a flexor surface this shortening may result in a scar contracture which may prevent full extension of that part. This will occur on the flexor surface of a finger if a straight-line incision is used. Curved or zigzag incisions will avoid this problem. Where scarring is extensive such as burn scars then scar contractures may be inevitable. Linear scar contractures can be corrected by realignment of the scar; there are various techniques to do this including Z-plasty and multiple Y—Vplasty. More extensive contractures will require release and introduction of additional skin by means of grafts or flaps.
The new epidermis of a scar will often not have the same degree of pigmentation as surrounding unscarred areas. Most scars are hypopigmented, but hyperpigmentation can also occur. The only ways to deal with this problem are cosmetic camouflage or tattooing.
Where wound edges are not anatomically aligned in the vertical plane or where a bevelled cut is not repaired accurately there is a risk of contour irregularity in the healed scar. This can usually be avoided by accurate wound repair, if necessary excising bevelled edges to restore even vertical edges for repair. A variation of this problem occurs when a curved laceration heals, in that the scar shortens and that portion of skin within the concavity of the curved scar tends to become raised. This problem is known as trapdooring or mushrooming. It will often improve with time, but scar revision is sometimes indicated to correct it.
In traumatic wounds it is possible for particles of grit, dirt or soot to become implanted in the wound as it heals. Thisresults in tattooed scars where the particles of foreign material show through as blue or black discoloration of the scar. Adequate primary wound management can avoid this. Abrasions with ingrained dirt should be scrubbed with a stiff brush; more deeply tattooed wounds should be excised. Late correction of tattooed scars can be very difficult.
If skin sutures are left in place for more than 7 days then scars from the stitch marks will usually result. This problem can be avoided by using subcuticular sutures wherever possible, removing skin sutures before 7 days and, where prolonged wound support is needed, supplementing skin sutures with subcuticular sutures allowing early removal of the skin sutures. Adverse scars due to prominent stitch marks can rarely be improved by scar revision.
In some circumstances scars remain in the remodelling phase for longer than is usual. These hypertrophic scars are more cellular and more vascular than mature scars, there is increased collagen production and collagen breakdown, but the balance is such that excess collagen is produced. Clinically these scars are red, raised, itchy and tender (Fig. 3.14). Such scars will eventually mature to become pale and flat, and it is this spontaneous resolution which distinguishes hypertrophic scars from keloid scars. Hypertrophic scars typically occur in wounds where healing was delayed, perhaps where complications such as infection or dehiscence occurred. They are more common in children and where skin tension is high such as the tip of the shoulder or any scar that runs across relaxed skin tension lines.
The risk of developing a hypertrophic scar can be minimised by ensuring quiet primary healing. Where hypertrophy does occur patience is usually rewarded by improvement with time. Massage of the scar with moisturising cream or the application of pressure to the remodelling scar can accelerate the natural process of maturation. Patients with hypertrophic bum scars are supplied with custom made Lycra pressure garments that promote acceleration of scar maturation. Revision of hypertrophic scars is appropriate where they cross skin tension lines or where a specific wound healing complication occurred. In the absence of these factors scar revision should be avoided as it will usually be met with recurrence.
In some situations there is an extreme overgrowth of scar tissue that grows beyond the limits of the original wound and shows no tendency to resolve. Keloid scars are biologically identical to hypertrophic scars that fn turn are an extension of normal scar behaviour. Whilst it is usually possible to make the distinction between these scar types, they are best regarded as a spectrum of scar behaviour (Table 3.4). Keloid scars are more frequent in Afro-Caribbean and oriental racial groups (Fig. 3.15).They often occur in wounds that healed perfectlywithout complications. They are more common in certain sites such as the central chest, the back and shoulders and the ear-lobes. Many keloid scars are untreatable and surgical treatment as a single modality will usually be met with recurrence. Some keloid scars will improve with the application of pressure. Intralesional injections of steroids such as triamcinolone can be helpful. The best cure rates are achieved with a combination of surgery and postoperative interstitial radiotherapy.
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