27 Principles and applications of tissue expansion

Synopsis

Tissue expansion is a time-tested, proven, simple technique to generate tissue to reconstruct defects.

The technique stretches skin and soft tissue that have the same color and texture as the adjoining skin where expanded tissue is needed.

In the breast, expansion is particularly useful in stretching existing anatomy to accommodate a permanent prosthesis.

Use of the tissue expansion technique can be encouraged.

Introduction

The plastic nature of the human integument can be witnessed whenever the skin must allow for growth underneath it. The surgeon can take advantage of this plasticity when either medical need or aesthetic surgery would benefit from the creation of new, autogenous skin. Tissue expansion can be observed in a variety of developmental, medical, and cultural concepts. For example, basic methods of tissue expansion can be seen in some tribal practices in which wooden and metallic rings are purposely and gradually used to increase the size of lips and earlobes. Just as development of a fetal brain will cause the overlying skull to grow, growth of the skeleton will cause all normal skin and soft tissues that envelope bone to respond and expand. Similarly, the growth of other structures inside the body will cause skin and subcutaneous tissues to expand, as shown by the serial growth of the abdomen with successive pregnancies. Whether the growth is caused by benign or malignant tumors under histologically normal skin or is experienced in the gravid abdomen, there is a clear response to nongenetic stimuli for the necessary growth to accommodate underlying structures.

The benefits of this strategy have caused a significant evolution of therapeutic techniques since the early 1980s: donor tissue can be generated in situ and used for reconstruction without compromise of innervation, vascularity, or external physical appearance.

There are various methods for expansion of skin, bone, and other tissues. Placement of a prosthesis under soft tissues allows the surgeon gradually to add saline and expand subcutaneous and cutaneous tissues. External hardware is used by surgeons to expand fractured bone gradually through the application of distraction force. The techniques have been applied to the craniofacial skeleton as well as to most of the long bones of the body.^1,² Vacuum-assisted closure (VAC) uses this principle of applying force to the cells surrounding a wound to stimulate the induction of new tissue that will subsequently close the wound.³

Knowledge advances in tissue expansion principles are discussed below.

Historical perspective

In 1905, Codvilla applied the principles of using an external, distractive force to encourage tissue expansion in bone.⁴ Bone tissue regeneration was later documented in 1970 by Ilizarov and others, who provided roentgenographic and morphologic data from experimental distraction epiphysiolysis.² Shortly thereafter, Matev reported the expansion of bony tissue after amputation of the thumb at the metacarpophalangeal joint.⁵

In the meantime, physicians began to recognize the induction of new soft-tissue growth adjacent to the bony structures undergoing gradual lengthening. In 1957, Neumann implanted a subcutaneous balloon to induce soft-tissue growth purposefully for the reconstruction of an external ear deformity.⁶ Unfortunately, his report was considered anecdotal, so progress in surgical, soft-tissue expansion was delayed until the 1982 reports of using implanted silicone balloons to expand overlying soft tissue were published.

Radovan ⁷ and Austad and Rose⁸ simultaneously developed the concept of implanting silicone balloons as expanders. Austad’s prosthesis was a self-inflating device that used osmotic gradients driven by salt placed within the expander. His largely experimental work was critical to elucidating the physiology of tissue expansion.⁹

Radovan’s device contained a self-sealing valve through which saline was periodically injected to increase the size of the expander. His work was initially greeted with skepticism. Despite this, Grabb’s enthusiastic acceptance of Radovan’s technique stimulated its rapid and wide application to create new horizons in reconstructive surgery.¹⁰^–¹⁵ Large studies subsequently confirmed the safety and efficacy of this technique.

Biology of tissue expansion

Extensive information is available regarding the biology of tissue expansion. After animal experiments were completed,^9,¹⁶ studies on human tissue examined the process of tissue expansion that occurs both during the period of expansion and postoperatively.¹⁷ Studies of the effects of tissue expansion on nerve, muscle, and bone have also been published.

Skin

Statistical analysis of multiple sites over the implant and its periphery has revealed a significant increase in epidermal thickness during the process of expansion. Early after placement of the prosthesis, significant thickening of the epidermis is evident. This is also seen in sham controls and may represent, in part, postoperative edema. Within 4–6 weeks, epidermal thickness generally returns to initial levels, but some increase in thickness persists for many months.

The increased area of skin over the expander includes not only normal skin recruited from adjacent areas but also new skin generated by increased mitosis.¹⁸ Hair follicles are not reproduced in humans, so individual follicles are distracted during expansion. Distractions between follicles are less noticeable in blonds than in dark-haired individuals. Melanocytic activity is increased during expansion but returns to normal levels within several months after completion of the reconstruction. Although hair follicles and accessory skin structures are compressed by tissue expansion devices, they show no evidence of degeneration.

During expansion, the dermis decreases rapidly in thickness over the entire implant. Thinning is most pronounced in the first several weeks after implant placement and persists for the entire period of expansion. Dermal thinning persists at least 36 weeks after expansion is completed in human tissue.¹⁹

Capsule

A dense fibrous capsule that becomes less cellular over time forms around the implant. The capsule is thickest at 2 months of expansion. Progressive collagenization with well-organized bundles develops over 3 months. Molecular studies have demonstrated upregulation in the wingless signaling pathway in the pathogenesis of fibroproliferation in the capsule; this proliferation may contribute to the capsular contracture seen after radiation therapy in breast cancer patients. Such increases have not been demonstrated in nonirradiated tissue. No evidence of dysplastic changes or loss of normal cell maturation has been observed. Dystrophic calcification may occur when a hematoma resolves or when the prosthesis is repeatedly traumatized. The capsule resolves after the prosthesis is removed and little clinical or histologic evidence of it remains over time. Histological examination of capsular tissue demonstrates an extensive vascular plexus within collagen. The capsule itself can be harvested as a local flap because of this induced vascularity.

Muscle

Muscle atrophies greatly during the process of expansion, whether the prosthesis is placed above or below a specific muscle. The effects on human muscle after expansion during breast reconstruction have shown occasional histologic ulceration. Focal muscle fiber degeneration with glycogen deposits and mild interstitial fibrosis has been noted. Some muscle fibers show disorganization of the myofibrils in the sarcomeres.²⁰ Animal studies on the histomorphologic changes in skeletal muscle suggest that the expansion of skeletal muscle is not a stretching process but is rather a growth process of the muscle cell accompanied by an increase in the number of sarcomeres per fiber. Expanded skeletal muscle repairs normal muscle architecture, vasculature, and function after the prosthesis is removed.²¹ Muscle mass returns to normal levels after removal of the device in humans.

Bone

The effect of expansion on underlying cranial bone has been studied in the animal model.²² Decreases in both bone thickness and volume in cranial bone are evident beneath the expander, where osteoplastic bone resorption occurs. In contrast, there is an increase in these predominantly at the expander periphery, where a periosteal inflammatory reaction is seen. Bone density is unaffected.

Expansion over the cranium in children under a year of age should be done judiciously and slowly. An unclear association between craniosynostosis and expansion over the anterior skull has been seen in one patient. Depression of cranial bone during expansion may occur before 1 year of age, but usually corrects itself once the expander is removed. Cranial bone appears to be measurably more affected in thickness than long bone is. Long-bone remodeling begins within 5 days after removal of the expander, and the long bone is completely normal within 2 months. Remodeling in cranial bone is complete in 2–3 months.

Vascularity of expanded tissue

The robust vascularity of expanded tissue was clinically in evidence long before laboratory work measured it (Fig. 27.1). It has been clinically and histologically demonstrated that a large number of new vessels are formed adjacent to the capsule.²³

Fig. 27.1 Transillumination of expanded human skin that shows an intense increase in arterioles and venules as well as a dense, interconnecting capillary bed. The proliferation of capillary bed renders the overlying skin erythematous.

The content of collagen fibers in existing vessels initially decreases after expansion, while elastic fibers in existing blood vessels initially increase in response to mechanical stress.

Angiogenesis occurs in response to induced ischemia of the expanded tissues. The number of cells expressing vascular growth factor is significantly higher in expanded tissue than in nonexpanded, similar tissue.²² Expanded fascial flaps show a measurable increase in vascularity between the fascia and subcutaneous tissue. Increased perfusion to the distal and peripheral areas of the flap also increases the robustness of the flap²³ and the possibility of harvesting a larger flap. Similar studies on prefabricated, expanded, pedicled flaps have shown increased vascularity within the pedicle, as well as in the surrounding, adjacent, random area.

The increase in vascularity affords the expanded tissue important functional benefits. Animal studies have shown that flaps elevated in expanded tissue have significantly greater survival areas than acutely raised and delayed flaps (Fig. 27.2).²⁴ Similar studies employing labeled microspheres have demonstrated an increase of flap survival, as well as increased blood flow in the expanded tissue.¹⁵

Fig. 27.2 Barium-injected radiograph of vessels in a random-pattern skin flap in a pig (A) and an expanded flap in the same animal model (B). A dramatic increase in the vascularity of the expanded flap is evident.

(From Cherry GW, Austad E, Pasyk K, et al. Increased survival and vascularity of random-pattern skin flaps elevated in controlled, expanded skin. Plast Reconstr Surg 1983;72:680–687.)

Cellular and molecular basis for tissue expansion

The application of mechanical stress to living cells affects various cell structures and signaling pathways that are highly integrated (Fig. 27.3).^25,²⁶ These closely integrated cascades are theorized to explain the generation of new tissue through mechanical stimulation.²⁶ Several in vitro stretching systems have been used to understand better the molecular events that occur.²⁷

Fig. 27.3 Effects of tissue expansion on surrounding tissue. Strain-induced responses are mediated by growth factors such as platelet-derived growth factor (PDGF) that are known to stimulate cutaneous cell proliferation. Other growth factors such as transforming growth factor-β (TGF-β) may stimulate extracellular matrix production. Membrane-bound molecules including protein kinase play a key role in regulating intracellular signaling cascades. EGF, epidermal growth factor.

(Adapted from Takei T, Mills I, Arai K, et al. Molecular bases for tissue expansion: clinical implications for surgeon. Plast Reconstr Surg 1998;102:247–258.)

Mechanical deformation forces involve several cellular mechanisms including the cytoskeleton system, extracellular matrix, enzyme activation, secondary messengers, and ion channels. The cytoskeleton plays a critical role in mediating the transformation of extracellular mechanical force to intracellular events. A system of microfilaments within the cytoplasm not only maintains intracellular tension and cell structure but also transduces signals to adjacent cells and initiates transduction cascades within the cell (Fig. 27.4).²⁶

Fig. 27.4 Schematic of possible signal transduction pathways induced by mechanical strain. Transduction pathways are activated by numerous strain-induced signals transmitted through various membrane receptor or membrane ion channels. Terminal enzymes that are activated by these intracellular cascades transduce these signals into the nucleus. cAMP, cyclic adenosine monophosphate; DAG, diacylglycerol; IP₃, inositol 1,4,5-triphosphate; JNK, c-Jun amino-terminal kinase; MAPK, mitogen-activated kinases; MEK, MAPK kinase; MEKK, MAPK kinase; PGE₂, prostaglandin E₂; PKA, protein kinase A; PKC, protein kinase C; PLC, phospholipase C.

Protein kinase C plays a pivotal role in signal transduction. Mechanical strain on cell walls activates inositol phosphatase, phospholipase A₂, phospholipase D, and other messengers. Activation of these components leads to activation of protein kinase C, which is, in turn, associated with activation of proteins; presence of this protein activation cascade suggests that intracellular signals can be transmitted to the nucleus. Protein kinase C activation has been noted in human cells subjected to strain in vitro.²⁶

Many growth factors, including platelet-derived growth factor and angiotensin II, play a role in strain-induced cell growth.²⁸ Extensive laboratory studies now underway are attempting to quantify and determine the interrelationships of these two, complex molecules. Downstream of the cellular membrane molecules, several common pathways are activated by expansion via both growth factors and mechanical strain; these pathways affect both the cytoskeletal system and protein kinase families.

Implant types

A wide variety of off-the-shelf and custom implants of any shape is available from manufacturers. Radovan’s initial expander consisted of a silicone prosthesis with two valves, each connected to the main reservoir by silicone tubing. One valve was used to inject fluid; the other was used to withdraw fluid. Technologic improvements produced a single valve that serves both purposes. There are also expanders that have integrated valves and those that self-inflate, a technology that has received renewed interest since biologically safe hydrocolloids became available.

Expanders with distal ports

Remote filling ports have the advantage of minimizing the risk of implant puncture during inflation. The distal, self-sealing injection port and inflation reservoir are connected to the prosthesis by a length of tubing. This allows the injection port to be placed away from the expander pocket and is advantageous when the overlying skin and soft tissues are thin or when the pocket is too tight to hold an expander with an integrated valve safely.

It is also possible to move the inflation port of a distant reservoir to the exterior of the body; this location facilitates inflation, particularly when the expansion is accomplished by ancillary help or family. Concerns about colonization risk can affect both selection of an implant and management of complications.

Early implants carried a high risk of various types of failure, but improvements in the design of expanders and associated ports have significantly reduced the incidence of mechanical failure.

Expanders with integrated ports

The inflation reservoir may be incorporated directly in the prosthesis. Such devices have the advantage of avoiding the remote port and its associated mechanical problems. However, the risk of inadvertent perforation of the prosthesis during inflation is higher with integrated valves because the valve and integrated prosthesis can be difficult to palpate. Magnetic and ultrasonic devices can be useful when the valve is difficult to locate and metal finding devices have been designed. Expander prostheses with integrated valves are particularly popular for breast reconstruction where adequate soft tissue and pocket can accommodate the added projection of the injection port.

Self-inflating expanders

Self-inflating expanders have become available largely through Europe; these contain osmotic hydrocolloids that cause migration of extracellular water through the silicone membrane of the device. The first such expander was devised by Dr. Austad and was used experimentally; however, it was not approved by the Food and Drug Administration and is not available in the US.⁸

An osmotically active hydrogel expander has been developed and used in expansion of the orbit for management of microphthalmia and anophthalmia.²⁹ Chummun and associates recently reported their experience using the osmotic tissue expander in patients. Their implant draws sufficient water from the adjacent tissues, spontaneously expanding the prosthesis up to 10 times its original volume.³⁰

These devices have the theoretical benefit of continuous slow inflation of the prosthesis. Further benefits may include reducing the number of office visits, lessened pain, and more rapid expansion. Such prostheses have the downside of potential continued expansion even if overlying tissue becomes compromised.

Prosthesis shape, texture, and surface treatment

Prostheses that expand differentially into any specific shape, rather than the usual round, are available. Differential expanders have found the most use in reconstruction of the breast, where ptosis and projection are desired. Low-profile implants that accordion on themselves were designed to eliminate fold-flaw erosion early in the expansion process.

Attempts have been made to incorporate surface textures and geometrics on the expander surface to immobilize the expander and to decrease capsular contracture. Textured silicone expanders have the theoretical advantages of allowing less capsule formation and achieving more rapid expansion. New expanders with surface-bound macromolecules are in development and will attempt to speed expansion by minimizing adjacent scar formation; these will probably become available in the future. Molecules that will form a bacteria-hostile environment are also being devised. These will decrease the development of “slime” around implants in which bacteria live, thus decreasing microbial ability to resist systemic antibiotics.

Basic principles

Tissue expansion is a protracted procedure that may involve temporary, but very obvious, cosmetic deformity. In general, emotionally stable patients of all ages tolerate tissue expansion well. Noncompliant or mentally impaired patients are poor candidates. Smokers have a higher risk of complications. Tissue expansion is generally best performed as a secondary reconstructive procedure rather than in the acute trauma period. Expansion can be performed adjacent to an area of an open wound before definitive closure, but such a procedure carries the risks of infection, extrusion, and less-than-optimal results. Tissue expansion is best suited to those patients who require definitive, optimal coverage when time is not of the essence.

Incision planning and implant selection

The key to successful expansion is meticulous planning before any incision is made. The proposed type of flap – advancement, rotation, or interpositional – that is to be expanded should be carefully planned: the simpler the flap, the less the potential for complication. Ideally, planning is done so that: (1) incisions are incorporated into tissue that will become one margin of the flap; (2) aesthetic units are reconstructed; (3) scars are in minimally conspicuous locations; and (4) tension on suture lines is reduced. The length and position of resultant scars play a major role in determining the overall cosmetic postoperative result. Careful planning allows the prosthesis to be placed through an incision that will both minimize the risk of compromise during flap development and optimize cosmetic reconstruction.

Incisions should be planned to minimize tension on the suture line and risk of extrusion. Tension from the initial inflation on the suture line will be greater when incisions are parallel to the direction of expansion than when they are perpendicular to it. Undermining of the prosthesis should be sufficient enough that the prosthesis can be easily accommodated and the wound can be closed in multiple layers. The inflation valve and tubing should be maintained at a site away from the incision.

Choice of an implant with an external distal port may affect surgical planning. Cultures of implants with external valves revealed that 82% of these prostheses had colonized the expander capsule and had some infection present; this constitutes an infection risk that is slightly higher than that of totally buried prostheses.³¹ Although patients tolerate this colonization well and experience few complications, externalized ports are contraindicated when a permanent prosthesis or bone grafts are to be used after expansion is complete.

The size of the implant selected should closely relate to the size and shape of the donor surface. An implant equal to or slightly smaller than the donor area is selected. Because there is minimal risk in hyperinflating the prosthesis to several times the manufacturer’s designated volume, less importance is placed on the implant’s specific volume than on its overall base size. On occasion, a custom-fabricated implant may be necessary.

In general, the use of multiple small expanders is better than the use of one large expander. Inflation of multiple prostheses proceeds more rapidly and complications are fewer. Multiple expanders also allow the surgeon to vary the plan for reconstruction after expansion has been achieved.

Because of the variety of functional, medical, and surgical considerations, the choice between an integrated valve and a distal inflation port should be considered on a case-by-case basis, without neglecting plans for infection control and the possible need for nonmedical personnel to inflate the implant.

Implant and distal port positioning

If a remote or distal filling port and reservoir is chosen, it must be placed superficially in subcutaneous tissue, where even an extremely small port is easily palpable under stable skin. To minimize discomfort, it is occasionally possible to position a filling port in an area that is relatively less sensitive. The port should be placed in a location that will not be subjected to pressure when the patient is lying in a position that could put direct pressure immediately over the fill port. Bony prominences are avoided.

Care must be taken to avoid kinking of the tubing so that the injected saline will flow readily to the prosthesis. The prosthesis tubing should avoid the incision through which the implant is placed and should not traverse joints. If placement of an external valve is chosen, the connecting tubing should be tunneled a significant distance from the prosthesis.

Expanders are usually placed beneath the skin and subcutaneous tissue above fascia. When the subcutaneous tissue is thin or the risk of extrusion is significant, prostheses may be placed under muscle.

Implant inflation strategy and technique

Implants should be partially inflated immediately after wound closure. This allows closure of “dead space” to minimize seroma and hematoma formation. It also smoothes out the implant wall to minimize risk of fold extrusion. Enough saline is placed to fill the entire dissection space without placing undue tension on the suture line.

Serial inflation usually starts 1–2 weeks after initial placement, although inflation schedules can be individualized to the specific case and the tolerance of the patient. Inflation reservoirs seal best when a 23-gauge or smaller needle is used. A 23-gauge butterfly intravenous needle is especially useful; it allows the patient to move slightly without dislocating the needle.

Frequent small-volume inflations are better tolerated and are physiologically more suited to the development of adequate overlying tissue than are large infrequent inflations. For practical purposes, most prostheses are inflated at weekly intervals. On occasion, accelerated inflation schedules may be followed.³² In children who have devices with external ports, small-volume inflation at 2–3-day intervals is well tolerated. Individual inflations proceed until the patient experiences discomfort or blanching of the overlying skin. In hypoesthetic areas, objective changes in flap vascularity must be evaluated with particular care. Although a variety of devices such as pressure transducers and oxygen tension monitors are available to help determine proper inflation; an objective inspection of the patient’s response is usually a reliable indicator of appropriate inflation. Serial inflations proceed until an adequate amount of soft tissue has been generated to accomplish the specific surgical goal.

Tissue expansion in special cases

Burns

The use of tissue expansion in reconstruction of burns, particularly about the scalp and face, has revolutionized the treatment of burn patients. Because there is almost always inadequate tissue after burns, reconstruction should be carried out after all burns have thoroughly healed and scars have matured. Planning is particularly important in these cases so that a minimum number of suture lines is produced and that these suture lines do not cross aesthetic units. Significant late distortion and contracture may result in excessive scars placed in burned tissue, particularly in the facial area.

Skin that has suffered a partial-thickness burn or that has been scarred by adjacent burns is attenuated and is more amenable to expansion.³³ Incisions can be placed in previous scars, but the scar should be mature and relatively thick so that extrusion does not occur. Using an access incision within normal tissue that is peripheral to the burned area further minimizes the risk of extrusion. The principle of using multiple, smaller-volume prostheses is especially appropriate in burn patients. Perioperative antibiotics and meticulous preparation are always used because the incidence of infection is higher in burn patients.

Tissue expansion in children

Skin and soft tissue are always thinner in children than in adults. These tissues are probably better vascularized but less resistant to trauma. Tissue expansion has a higher complication rate in children than in adults.³⁴ Rather than using excessively large prostheses or expanding tissue aggressively, accomplishing serial repeated expansions may be helpful in children. This is done with the understanding that major complication risk – particularly extrusion – is more common at the second, third, and fourth serial expansion.³⁵ This is particularly true in the head and neck (with the exception of the scalp). Expansion of the facial areas and neck can be particularly difficult.

After age 5, most children are able to cooperate adequately, so complication rates decrease. In many children, an external reservoir is used to minimize the amount of emotional trauma caused by injections. Application of EMLA to the skin over the buried injection port is also helpful in minimizing discomfort. Small-volume inflation at frequent intervals is especially useful in children because the amount of pain generated is considerably less.

As in all cases, planning should be meticulous so that the flaps generated will result as much as possible in reconstruction of anatomic units. With growth, contracture may occur, particularly about the mouth and around the orbits, and revision will be required.

Expansion of myocutaneous, fascial, and free flaps

Myocutaneous flaps are the standard of care for the treatment of large defects, particularly when bone and vital structures are involved. The territories of standard flaps are well described. These territories can be considerably enlarged by placing an expander beneath the standard myocutaneous flap, and an extremely large flap can be developed over a short period. Expansion increases the vascularity of the flap and allows a large, adjacent random area to be carried with the original flap.³⁶ The vascular pedicle of such flaps remains intact and may in fact be elongated, thus allowing flaps to be transferred farther.

Myocutaneous flaps such as the latissimus dorsi and pectoralis can be expanded to almost double their surface area, allowing coverage of almost any defect on the abdomen or thorax.³⁷ Expanders of up to 1000 mL can be placed beneath such flaps and rapidly expanded. For example, bilateral latissimus dorsi myocutaneous flaps can be expanded and moved to the midline to cover large meningoceles or the vertebral column. The expansion prostheses in these cases are placed under the latissimus dorsi muscle through incisions in the lateral margin of the muscle.

In the procedure one edge of the myocutaneous flap is selected for implant placement, and care is taken not to injure the vascular pedicle. The expanded myocutaneous flap generated can then be transferred as either a pedicled flap or a free flap. Such expanded flaps not only provide coverage of other donor defects but also preserve the function of the muscle.

Fasciocutaneous flaps can be expanded either before or after transposition. When flaps are expanded before transfer, it is best to keep the prosthesis as far away from the pedicle as possible, thus preferentially expanding the random area of the flap. Within 6 months of transfer of these flaps, the random blood supply is usually sufficiently established to allow placement of the expander anywhere under the flap.³⁸

Total facial reconstruction with an extraordinarily large flap has been accomplished using a pre-expanded bilateral parascapular free flap. Use of this strategy allows one large aesthetic unit to be moved.^39,⁴⁰

Expanded full-thickness skin grafts

Because a donor defect is usually created by harvesting full-thickness grafts, their use is infrequent. The placement of a large tissue expander beneath the donor site can result in a large full-thickness graft that is particularly useful in resurfacing large areas of the face or the entire hand or foot. Expanded full-thickness grafts are extremely resilient and have been shown to grow in children over time. The rate of contracture is significantly less than that of split-thickness grafts.

The best color matches are generated when the full-thickness graft is expanded and harvested as close as possible to the recipient site. The periorbital area and the area around the mouth are particularly well suited to reconstruction with expanded full-thickness grafts harvested from the supraclavicular area. Expanded full-thickness grafts are very helpful in reconstructing defects of the forehead that encompass more than 70% of its surface area. A single full-thickness graft can be harvested from the supraclavicular area or from under the breast fold. Care must be taken that hair-bearing tissue is not transferred to an area that normally has no hair.

Expanders with a surface area equal to that of the donor site are placed through peripheral incisions. The prosthesis is then inflated to an adequate volume. After sufficient donor tissue is generated, a template is made of the recipient site and transferred to the expanded donor area. The full-thickness graft is harvested so that it is approximately 10–15% larger than the recipient area, allowing for some contracture. The prosthesis is then removed, leaving the capsule intact, and the donor site closed primarily. Closing of the donor site should be done so that the resulting scar is as innocuous as possible. In the recipient site, expanded full-thickness skin grafts require more immobilization than split-thickness skin grafts do. A bolster dressing or, ideally, a VAC sponge dressing is required. The graft is sutured in place and a VAC sponge placed over the graft; 125 mmHg of negative pressure is maintained for 4 days. Successful take of such grafts placed with this technique is extremely high.

Reconstruction in the head and neck

The head and neck area contains many specialized tissues that must be matched appropriately to achieve optimal aesthetic reconstruction. Aesthetic reconstruction is maximized by mobilization of adjacent local tissues rather than by transfer of distant tissues with poor match of color, texture, or hair-bearing capability. Tissue expansion therefore allows optimal aesthetic reconstruction by use of a similar adjacent tissue area to reconstruct a defect without creation of a donor site.^11,⁴¹

The skin of the face can be subdivided into five tissue-specific areas:

1. The scalp is unique in that it contains specific hair-bearing qualities that cannot be mimicked by any other tissue of the human body.

2. The forehead is a continuation of the scalp, but it is distinguished from the scalp by its thick skin, large number of sebaceous glands, and lack of hair.

3. The nose is embryologically related to the forehead, so it closely mimics the forehead in color, texture, and sebaceous gland content.

4. The lateral cheek areas, neck, and upper lip have fewer sebaceous glands; the skin is thinner, and the hair-bearing pattern is significantly different in quality and quantity from that on the remainder of the body.

5. The skin of the periorbital areas is extremely thin and pliable, containing a minimal number of sebaceous glands.

There is a limited amount of tissue on the human face, so procedures must be planned carefully and reconstruction accomplished correctly at the first attempt. Correct planning should take into consideration the area and shape of the defect, quality of the remaining tissue of the aesthetic unit, pre-existing scars, and reconstructive needs of other areas of the head and neck. Because of the risk of complications, it is prudent to plan alternative reconstructive strategies before any prostheses are placed. If there is a chronic infection, the presence of fistulas, or the need to reconstruct facial mass, other reconstructive alternatives may achieve a better final result.

Scalp

Tissue expansion is the ideal procedure for the reconstruction of scalp defects (Fig. 27.5).⁴² Expansion of the scalp is well tolerated and is the only procedure that allows development of normal hair-bearing tissue to cover the areas of alopecia. The amount of scar and deformity generated is considerably less than with previous procedures such as serial reduction and complex multiflap procedures.