Revising Large Scars
Large scars in the head and neck are often the cause of significant emotional distress to patients, and often present unique challenges to the plastic and reconstructive surgeon undertaking their revision. The primary goal of scar revision is to eliminate compromise of function that may have resulted from scar contracture; a secondary goal is to improve the appearance of the scar. Special techniques for the revision of large scars include serial partial excision, rapid intra-operative or prolonged tissue expansion, split- and full-thickness skin grafting, regional flaps and free microvascular tissue transfer. Recent research has investigated the use of artificial skin and autologous fat grafting for large scar revision.
Large scars may be long, linear scars, scars that are excessively wide, hypertrophic or atrophic, or scars that cover large surface areas. Mechanisms of injury include ablative surgery, flap failures, trauma, assault, animal bites, gunshots, infection, and burns. Such scars are often the cause of significant emotional distress to patients, and often present unique challenges to the plastic and reconstructive surgeon undertaking their revision. The techniques chosen for revision of a scar must address the specific problems caused by the scar in question.1
The ideal of simple scar revision is to hide, or near completely camouflage, scars. With regards to the revision of large scars, this ideal is often unattainable. Large scars in the head and neck may result in significant morbidity given the relatively close proximity of many vital structures. The goals of large scar revision in the head and neck are twofold. The primary goal is to eliminate or improve compromise of function that scaring and associated contracture has inflicted on nearby structures. A secondary goal is to improve the appearance of the scar; patients should be accordingly counseled. Above all, scar revision should cause no additional harm. The final functional and aesthetic results of large scar revision will depend upon the interplay of many factors, including the original mechanism of tissue injury, the size of the scar, its location and relationship to functional components of the head and neck, surgical technique, the patient’s ability to heal, and the occurrence of post-operative complications.
Scar maturation is classically felt to be complete at one year. Waiting one year from the time of initial injury allows the scar to approach stability prior to revision. Scar revision may be considered sooner than one year, however, if functional compromise, such as ectropion, entropion, or lagophthalmos emerges. Revision of large scars can be difficult, and in some cases may only result in minimal improvement despite one’s best efforts. It is important to consider each scar individually and to balance the patient’s desires with the surgeon’s desire for improved scar appearance.
Techniques for Revising Large Scars
Various simple scar revision techniques and adjunct topical, laser, and dermabrasion treatments are discussed elsewhere in this issue. These techniques are certainly applicable to large scars and, in many cases, may be sufficient to both improve function and cosmesis to an acceptable degree. For example, a large neck-dissection scar that has contracted, formed an obvious scar band, and impaired cervical function may most simply and efficiently be revised with multiple z-plasties that lengthen the scar and distribute tension (figure 1). Similarly, a large linear facial scar may be acceptably revised with a geometric broken-line closure (figure 2). In many cases, large scars are associated with significant loss of tissue and may cover large surface areas; it is in these instances that simple revision techniques must be augmented.
Serial Partial Excisions
If a scar is too large to allow primary skin closure in a single stage, serial partial excisions may be performed. The initial incision is placed within the scar at one margin. The wound edges are then undermined and a portion of the scar is excised after advancement. Care is taken to excise as large a portion of scar as possible, while allowing the remaining scar tissue and skin to be closed with minimal tension. After 8-12 weeks, additional excisions may be performed in the same manner, resulting in smaller and smaller areas of scar with each serial excision. In the last surgery, the residual scar tissue is excised and normal skin margins are re-approximated in the final closure. Depending upon the location and orientation of the ultimate scar, straight-line closure, broken-line closure or w-pasty may be chosen.
The technique of serial scar excision takes advantage of the ability of the skin to stretch after wound closure. If the area of scar to be excised is amenable, serial partial excisions can be performed in the same sitting, using the principles of biologic creep. If the scarred area is larger, serial excisions can be staged with 8-12 weeks between procedures depending upon patient and tissue factors.
The advantage of serial excision is that it allows for the reconstruction of defects using adjacent, like tissue, while giving the surgeon the opportunity to reorient scars, or move scars to nearby sights that may provide better camouflage, such as into hair-bearing areas, along hairlines, along relaxed skin tension lines or to the junctions of aesthetic units. The primary disadvantage is the need for repeat surgical procedures. If more than two serial excisions are required, tissue expansion may be used as an adjunct to reduce the number of surgical procedures. 2
Tissue expansion is similar to serial partial excision in that it too takes advantage of skin’s ability to respond dynamically to mechanical forces and to stretch with time. Like serial partial excisions, tissue expansion has the advantage of allowing for the replacement of lost or damaged tissue with neighboring tissue that is of similar thickness, quality, color, texture, innervation, and hair-bearing capacity, and obviates the need for a remote donor site and its associated morbidity.3 Large scars amenable to revision via tissue expansion are those that involve a substantial area of scarring, rather than long linear, or irregular scars. For example, a scalp scar resulting from split thickness skin grafting to a hair bearing area is ideally revised with use of a tissue expander to create a flap of nearby hair-bearing scalp that permits excision of the alopecic skin graft (figure 3).
Tissue expansion may be performed during surgery, or may be prolonged using an implanted tissue expander. Rapid intra-operative tissue expansion relies on mechanical creep. Gain in flap length via mechanical creep has been attributed to displacement of interstitial fluid and mucopolysaccharide ground substance, re-alignment of collagen fibers from randomly oriented to parallel, microfragmentation of elastic fibers, and migration of tissue into the surgical field by the force of stretching. A number of intra-operative expansion techniques and devices have been described from simple hooks, to balloon expanders similar to those used for prolonged expansion, to specially designed intra-operative skin-stretching devices.4-5 When using a balloon expander, at the time of scar revision, the expander is placed under the skin flap to be stretched. Expansion takes place by inflation of the expander with saline injected through the injection port. Studies have shown that cyclic stretching followed by relaxation results in the recruitment of more tissue than continued expansion. In contrast to prolonged expansion, where maximum inflation of the device is accomplished in 6 to 8 weeks by weekly injections, rapid tissue expansion is performed in one sitting, and at the same time as scar revision surgery.6 Rapid tissue expansion consists of inflating the expander over a few minutes, maintaining the inflated expander for three minutes, deflating the expander and repeating this process for a total of three cycles. Intra-operative tissue expansion can gain an additional one to three centimeters of length.3 While this technique does not produce as much additional flap length as prolonged expansion, there are cases of smaller volume scar revision where rapid expansion may be sufficient. In such cases, intra-operative expansion can allow scar revision in a singe surgery and can avoid the morbidity associated with prolonged expansion.
Biologic creep is the net gain of tissue that results from the process of prolonged tissue expansion. Multiple changes occur in the tissue overlying expanders that result in the generation of new skin. Studies show that the thickness of the epidermis either increases or remains unchanged, and that the active basal layer of the epidermis increases in thickness. The basal layer normally contributes 10% of the total epidermal thickness. During tissue expansion, this contribution increases to 40%, and the mitotic rate in the stratum basale increases. The mitotic rate eventually returns to baseline, but remains elevated for as long as 2 months after expansion. The dermis decreases in thickness with expansion, with greater thinning noted with more rapid expansion. Activated fibroblasts are observed throughout the dermis overlying expanders. Overall, expanded skin has a net accumulation of collagen. Thick, compact bundles of collagen are formed and are oriented parallel to the expander surface. Collagen fibers are incapable of returning to their relaxed convoluted form once they have been stretched. Melanin production increases, which may lead to temporary hyperpigmentation of the skin with expansion. The thickness of the subcutaneous tissue decreases as much as 50% with associated decrease in number of fat cells. After 12 months, fat cells return to baseline and after 2 years, slight increase in subcutaneous tissue is noted. Hair follicle density decreases with expansion as the number and morphology of follicles remains stable. Temporary alopecia can be seen as hairs are shifted to telogen. Should this occur, patients should be counseled that hair will return following expansion. Muscle responds to expansion with thinning and weakening. Expanded flaps have increased vascularity similar to delayed flaps, and expansion improves flap survival. The survival length of expanded flaps is actually significantly greater than that of delayed flaps, which in turn is significantly greater than that of acutely raised flaps. A fibrous capsule forms around the expander, and myofibroblasts are noted on histologic examination.7
In the face and neck, expanders are generally placed beneath the subcutaneous tissue and on top of muscle or bone. They may be placed beneath the platysma when a more bulky flap is required for reconstruction. In the scalp, expanders are placed beneath the galea and above the periosteum. Placement of expanders must be carefully planned. The incision made to implant the expander should ideally be adjacent to scar tissue to be excised, such that multiple nearby incisions are avoided. The injection port for the expander should be placed through the same incision used to implant the expander.
Inflation is begun 2 weeks after placement. Injections of isotonic saline are performed once or twice a week depending on local tissue and patient factors. Each inflation is carried out until the skin over the expander is firm, or the patient is uncomfortable. If blanching of the skin is seen, some saline should be withdrawn. Full inflation generally requires 4 to 8 weeks. The three most common expander shapes are crescent, round and rectangular. A round expander results in 25% gain in tissue, crescent-shaped 32%, and rectangular 38%. Prior to removal, the tissue expander may be briefly over inflated with saline. This over inflation aids in flap elevation and helps to disrupt the fibrous capsule around the expander. Some authors advocate excision of the fibrous capsule prior to reconstruction in effort to debulk the flap, and to minimized flap contracture after scar revision.3 Three-Dimensional technology is becoming more accessible, and may prove a useful tool for preoperative planning and expansion in the future.8
The advantages of tissue expansion are previously discussed. Disadvantages are the need for at least two surgical procedures (one to place the expander and one to revise the scar), the pain associated with expansion, cosmetic deformity while the expander is in place, need for repeated visits to the doctor and injections, and the risk of complications of expansion including infection, extrusion, and necrosis.
Skin grafts can be used for large scar revision when surrounding tissue is not amenable to expansion. The main advantages of skin grafting are the relatively low technical difficulty and the abundance of donor tissue.
Split-thickness skin grafts include only part of the dermis, while full-thickness skin grafts contains the entire dermis, including hair follicles. The amount of dermis included with the graft determines both the likelihood of survival and the level of contracture. Split-thickness grafts are able to survive with less host vascularity, but undergo more contracture and are more likely to heal with a whitish pale color. Full-thickness grafts require a more robust vascular bed for survival, but undergo less contracture and maintain the color of the donor site skin.9 See table 1.
When considering donor sites, the best choice for scar revision is skin from a donor site that resembles the recipient site in terms of color, texture, thickness and hair-bearing capacity. Donor sites for full-thickness skin grafts must be closed primarily, or a split-thickness skin graft from another site must be applied. Split-thickness skin grafts may be taken from any area of the body, including the scalp. Although donor sites for split-thickness grafts are able to heal spontaneously (adenexal structures necessary for re-epithelialization are preserved in the dermis), donor sites are frequently scarred or discolored when healed. If the patient is amenable to hair shaving, split-thickness grafts can be harvested from hair-bearing regions, such as the scalp. The scarring and discoloration resulting from harvest can be hidden in the hair when hair regrows at the donor site. In addition, re-epithelialization is faster, because of the remaining rich hair follicles. When taking a graft from a hair-bearing region, it is important to take a thin graft, because thicker split-thickness grafts can contain undesired hair follicles and eventually lead to hair in the graft and hair loss in the donor site.9
Particularly in the revision of large burn scars, in some cases the area of tissue injury is so large, or the compromise in function resulting from scar contracture is so great that regional pedicled flap or microvascular free flap reconstruction is required in order to provide sufficient vascularized tissue to the injured area. While the specifics of regional pedicled and microvascular free flap reconstruction are beyond the scope of this chapter, their use should be considered in cases of severe contracture or exposed vital structures.10-12
Integra Artificial Skin
Integra is a biosynthetic porous dermal matrix of cross-linked bovine tendon collagen, glycosaminoglycan, and a semi-permeable polysiloxane. Stiefel et al performed a study examining the use of Integra in the surgical treatment of postburn scars in adolescents and children. In this study, 17 patients underwent complete excision of large area hypertrophic scars or keloids with implantation of Integra for defect closure. Split thickness skin grafting of the Integra-derived neodermis was performed three weeks after implantation. Comparison of pre- and post-operative findings revealed a significant functional improvement in all patients and a considerable cosmetic improvement in all but two patients. The obvious advantage of using Integra is its unlimited availability and its applicability to almost anywhere on the body. The combination of Integra and a very thin split-thickness skin graft seems to allow for the regeneration of skin with minimal scarring.13
Autologous Fat Grafting
The regenerative potential of adipose stem cells has been recognized over the last decade. Via yet unclear mechanisms, autologous fat grafting has been shown clinically to improve the quality of overlying tissue and of scars. Specifically, clinical improvement of hypertrophic burn scars has been noted following autologous fat grafting beneath the burn site.14 In a recent study, Sultan et al endeavored to examine the effect of fat grafting in a controlled experiment using a model of murine fat grafting in conjunction with a previously described murine model of thermal injury. The group compared markers of neovascularization and fibrosis in fat- and saline-treated mice at two time points following thermal injury. Serial photography demonstrated improvements in coloration and texture in the scars of fat-grafted animals when compared with saline-grafted controls. Enzyme-linked immunosorbent assay (ELISA) analysis in fat-grafted animals demonstrated significant increase in vascular endothelial growth factor (VEGF) at four weeks, and decrease in fibrotic markers at eight weeks.15 Though these findings have yet to be tested in larger animals or in humans, fat grafting may prove applicable to the treatment of large scars in the future.
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