Randal W. Swenson

Introduction

During the past three decades, many reconstructive surgical procedures have been developed or improved, providing a functional and an aesthetic benefit. Among these, tissue expansion offers a unique potential to preserve both form and function. One of the major benefits of tissue expansion for correction of cutaneous defects is the ability to use tissue optimally matched in color, texture, thickness, and hair-bearing qualities. It may also obviate the need for multiple flaps or grafts and avoids creation of a second defect at a distant area to correct the primary deformity. Expansion of tissue is a dynamic process producing a dividend of tissue available for flap transfer. A basic understanding of the physiologic changes that occur with skin expansion and the techniques of expansion is imperative for any surgeon performing reconstructive procedures of the head and neck. Other than rapid intraoperative tissue expansion, the term tissue expansion is used in this chapter to refer to the prolonged expansion of skin during an interval of days to weeks.

History

Tissue expansion can be a natural physiologic process encountered in normal life, pregnancy and obesity being the most obvious examples. This process has been used for centuries in certain cultures to modify facial features as illustrated on the pages of National Geographic magazine. Modern use of tissue expansion was first introduced in the early 1900s. A technique was described that used progressively larger objects to expand tissue with multiple operations required.¹ Because of the number of procedures required and the high morbidity, the procedure was abandoned. The practical application of tissue expansion was not possible until the introduction of plastic materials later in the century. In 1957, Neumann published “The Expansion of an Area of Skin by Progressive Distension of a Subcutaneous Balloon.” This article described the use of a latex balloon to expand the skin for reconstruction of an ear.² He placed the balloon above the ear in a subcutaneous tissue pocket and brought a polyethylene tube out through an independent skin incision. He gradually injected air into the implant through a stopcock. His procedure was a success, but the potential impact of his work was not recognized at the time. No other work was performed on tissue expansion for almost 20 years.

In the early 1970s, Radovan and Austed independently began studying the use of tissue expansion to repair soft tissue defects. Radovan’s early expanders consisted of a balloon and two separate tubing systems for injection and removal of saline. The entire system was placed under the skin.³ His first experiments were performed in 1976 and were met with skepticism when his results were presented to the medical community later that year. This was most likely because of his unscientific methodology. He was not discouraged by the skepticism and continued his clinical trials. The results of Radovan’s experiments met wider acceptance 3 years later accompanied by Austed’s work using an osmotically driven, self-inflating expander.⁴ Austed, unaware of Neumann’s and Radovan’s work, first suggested the idea of implanting a device beneath the skin to induce tissue expansion in 1975. His work established the basis for understanding of the tissue response to expansion. His early laboratory experience and histologic studies confirmed that tissue expansion is safe and effective.⁵

Physical Properties and Morphologic Changes

It is important for surgeons performing tissue expansion to understand the physiologic and morphologic changes associated with the process. This knowledge will help the surgeon understand the potential benefits, limitations, and complications of this procedure. When the technique of tissue expansion was first introduced, the unanswered question was whether skin is stretched or new skin is created. If skin is simply stretched, a permanent gain in terms of surface area would not occur. Gibson⁶ studied the properties of skin and described its inherent extensibility. He noted that skin could stretch beyond its inherent extensibility and called this mechanical creep. The beneficial effects of mechanical creep are attributed to displacement of interstitial fluids and mucopolysaccharide ground substance, parallel alignment of randomly oriented collagen fibers, and migration of tissue into the field by the stretching force.

He referred to biologic creep as the gradual stretching of skin overlying a slowly expanding subcutaneous structure. This is not simple stretching because the skin is affected by metabolic activity, including the creation of epithelium, blood vessels, nerves, lymphatics, collagen, and elastin fibers. All of this occurs during sustained prolonged expansion of the skin.

The first experimental studies of skin expansion were performed by Austed et al⁵ and Pasyk et al⁷ using guinea pigs. They used self-inflating expanders, causing gradual uninterrupted expansion. Unlike humans, guinea pigs have loose skin, allowing it to move freely over the muscle beneath and to be picked up in large folds. These qualities make the guinea pig model less than ideal for understanding the effects of expansion on human skin. However, even with these limitations, their studies provided valuable information about tissue expansion. Because pig skin lacks a well-developed panniculus carnosus and has elastic tissue comparable with that of humans, it has been used in place of guinea pig skin for subsequent laboratory studies of skin expansion.

Tissue Expansion Devices

Because nearly every part of the body has been considered for tissue expansion, a wide variety of expander styles, sizes, and shapes have been introduced (Fig. 25-5). Custom-made expanders can also be used for irregular defects or unusual areas. The standard Radovan expander is composed of a Silastic reservoir, a self-sealing injection port, and connecting tubing. This design remains the most commonly used system. Expanders with self-contained injection ports are useful in some situations, but the injection port may be more difficult to identify, leading to a greater risk of damage to the expander during inflation. The necessary multiple percutaneous injections may also traumatize the expanding skin, leading to a greater risk of complications.

A directional expander has been developed for breast reconstruction. Becker²⁰ developed a permanent expander prosthesis for the same purpose. Manders and Friedman²¹ introduced a differential expander for the treatment of male pattern baldness. Despite many manufacturers’ modifications, the high technical standards for the devices have persisted. Their durability has been thoroughly tested, and their safety is well established.

Hallock22,23 was the first to study durability of expanders in a scientific way. He demonstrated in vitro that expanders can be overinflated at least 15 times the amount recommended by the manufacturer before rupture occurs. From in vivo studies, he concluded that expanders in the body could be safely overinflated to at least twice the amount recommended by the manufacturer without risk of rupture. However, the greater the pressure within the expander, the greater is the risk for leakage from the injection port. Nordstrom found that the average pressure necessary for leakage of the injection port is 32 mm Hg. This may explain reports of volume loss of saline injected into some expanders. To avoid such leakage, it is recommended to use the largest expander that can reasonably be inserted beneath the planned expansion area.

Expander Selection

Skin of the head and neck is unique because of its variety of texture, color, and hair-bearing characteristics. This presents a challenge when replacement of large areas of skin is necessary. Because the skin of the head and neck is always visible to the observer, optimal aesthetic reconstruction of a cutaneous defect is important. Tissue expansion can increase the availability of local matching tissue for reconstruction rather than relying on distant flaps and grafts that may be aesthetically incompatible.

When the shape of an expander is selected, the area to be reconstructed should be considered. For breast reconstruction, a round, pear-shaped, or directional expander is most helpful. For covering a large defect on the head or neck area, a rectangular expander is preferred. A crescent-shaped expander has been advocated for reconstruction of round defects. van Rappard et al²⁴ compared the three most commonly used expander shapes (i.e., rectangular, round, and crescent) for their effectiveness. By mathematic calculations, rectangular expanders provided the most effective gain of surface area in expanded skin. In clinical situations, the gain in surface area compared with the area of the expander base is 38% for rectangular expanders, 32% for crescent-shaped expanders, and 25% for round expanders.²⁴ Compared with conventionally shaped expanders, Brobmann and Huber²⁵ found that less expansion is required to gain sufficient skin for repair when custom-made expanders are used for reconstruction of irregularly shaped defects.

In determining the appropriate size of an expander, Radovan²⁶ initially suggested that the expander base be the same size as the defect to be reconstructed. It was thought that the surface area of expanded skin would be twice the area of the base of the expander used. However, with clinical experience, van Rappard demonstrated that only a fraction of the expected surface area is actually gained.²⁴ Gibney²⁷ recommended that the expander base be 2.3 to 3 times the surface area of the defect to be closed. This ratio of base size to expected increase in skin surface area is the generally accepted guideline and has been supported by van Rappard et al.²⁴

In addition to the size of an expander, there are other factors that influence the amount of skin gained from expansion. These factors, described by Gibson⁶ and Sugihara et al,²⁸ include the amount of undermining performed and the inherent extensibility of the skin. The response of skin to expansion differs according to the area of the body expanded and between individuals.

Technique

Tissue expanders can often be implanted with local anesthesia consisting of 1% lidocaine with epinephrine (1 : 100,000 epinephrine concentration). For larger expanders, general anesthesia is occasionally required. The importance of preoperative planning of the incision site and orientation of the implanted expander cannot be overemphasized. Preferably, the access incision for implanting the expander is in an area adjacent to the area to be reconstructed. For small areas of planned resection and for scars, the expander can be placed directly beneath or adjacent to the same area. Inappropriate incisions may limit the options for reconstruction after skin expansion. The incision for insertion of the expander is made with careful consideration of the anticipated flap design and with respect for preservation of the vascularity and motor and sensory nerve innervation of the area. Access incisions are usually made at the junction of normal tissue with the tissue to be replaced. However, incisions should not be placed in areas of reduced vascularity, such as in healed skin grafts or burn scars, because there is a high risk of dehiscence of the incision during expansion.

In developing the subcutaneous tissue recipient pocket for placement of an expander, it is important not to compromise the overlying tissue, which may lead to an increase in risk of tissue breakdown and extrusion of the expander. In the face and neck, the implant is placed beneath the subcutaneous tissue layer of the skin on muscle or bone. It may also be placed deep to the platysmal muscle when the skin is thin or when more bulk is required for the purpose of reconstruction. For scalp expansion, the expander is placed in a subgaleal pocket, leaving the pericranium intact.

It is important to create a sufficiently large subcutaneous tissue pocket to accommodate the implant without causing folds in the expander. The ridges made by folds may compromise the overlying tissue by creating focal points of increased pressure, leading to implant extrusion (Fig. 25-6). If these folds are noticed during inflation, it is recommended to gently manipulate them to dissipate the folds. If the area for expansion cannot accommodate the ideal-sized expander, a smaller expander can be used and overinflated to compensate for the smaller size.

The injection port of the tissue expander is placed through the same incision used for insertion of the expander. A separate subcutaneous tissue pocket several centimeters removed from the pocket created for the expander is developed to accommodate the port. Placement should be sufficiently removed from the expander so that the port can be easily palpated and accessible for saline injections. Placement must be such that inflation of the expander will not result in the expander’s covering the port, preventing further injections. The port should be placed in an area where the overlying tissue has sufficient thickness to avoid breakdown from repeated injections. The postauricular skin area over the mastoid should be avoided. The skin in this area is thin, and there is a high incidence of tissue breakdown and extrusion when the port is placed beneath this skin (Fig. 25-7).

The access incision for implanting a tissue expander is closed in layers with a strong permanent suture for the deep wound closure. This assists with counteracting wound closure tension on the incision line during tissue expansion. After closure of the incision, the expander may be injected with saline to obliterate the remaining dead space in the subcutaneous pocket. The volume injected should not create tension on the suture line. To allow sufficient healing, inflation of the expander is commenced 2 weeks after implantation. Injections of isotonic saline are performed every 1 to 7 days, depending on the volume injected and the response of the tissue. Too rapid inflation may thin the tissue and potentially compromise the final reconstruction.⁸ Because the goal of expansion is to create additional skin, sufficient time is required for proper tissue response.

In a sterile manner, a 23-gauge or smaller needle is used to inject saline through the injection port. The larger the needle, the greater is the risk for leakage. Injection of saline is usually continued until the skin overlying the expander feels tense or the patient complains of discomfort. If blanching is noted and it does not resolve after a few minutes, it is recommended that a few milliliters of saline be removed until blanching disappears. Skin perfusion over the expander may be tested by finger pressure to check capillary refill. Relaxation of the skin over a recently inflated expander usually begins within 24 hours of injection. Periodic inflation of the expander is continued until sufficient skin is generated to allow reconstruction. This generally takes 6 to 12 weeks once the expansion process is started.

When large defects are reconstructed with the aid of tissue expansion, it is usually required to advance expanded skin in the form of a flap over a convex surface area of the head or neck. When this is the case, a significant amount of flap length may be lost when the skin is advanced because of the convexity. Sufficient skin must be created to raise a flap that will close both the donor site and the defect. It is wise to continue skin expansion to a point at which more skin is available than is necessary. This is especially true for scalp expansion. The width of the anticipated area to be reconstructed is measured and skin expansion is continued until the length of the planned skin flap is three times this measurement. Expanded skin is measured from the base of the expander across the dome to the opposite side of the base in the direction of the linear axis (length) of the planned advancement flap.

The second surgical stage is performed when sufficient additional skin has been created. Expanded skin appears to act like a delayed flap, so use of epinephrine should be avoided in removing expanders and proceeding with reconstruction. This recommendation is based on studies by Reinisch and Myers,²⁹ who studied the effect of epinephrine on delayed and nondelayed random pattern flaps. The authors found that when 1 : 200,000 concentration of epinephrine was used in dissecting a flap, the surviving length of nondelayed flaps was unaffected, whereas that of delayed flaps was significantly reduced.

The expander is inflated with saline immediately before removal because it aids in undermining of the tissue in the process of developing a skin flap. Capsulotomies and sometimes capsulectomies are necessary to increase the mobility of the flap. It is still uncertain how much the capsule contributes to the vascularity of the flap, so limited resection of the capsule is recommended to avoid vascular impairment. It is important to ensure that sufficient expanded skin is available to resurface the anticipated defect. This is confirmed by advancing the expanded skin into position before removal of any tissue at the recipient site. In the event of insufficient skin, the deflated expanders can be replaced in their subcutaneous pockets, the flaps advanced beyond the expanders as much as possible, and the appropriate amount of tissue removed at the recipient site. Inflation of the expanders is commenced after a few weeks of healing. Expansion progresses until sufficient skin is available for coverage of the remaining area to be removed at the recipient site.

Scalp Expansion

The scalp is unique because of its density and the presence of hair. Defects of the scalp secondary to burns, those due to avulsion-type injuries (Fig. 25-8), and those resulting from cancer or tumor removal have often been difficult to correct. The scalp is well suited for expansion because of its vascularity and thickness. The abundant vascularity of the scalp allows expedient healing and a low rate of complications from expansion. Large defects of the scalp have traditionally been reconstructed with skin grafts or flaps with little or no hair-bearing skin. Although this provides coverage of the area, it results in an unacceptable aesthetic appearance (Fig. 25-9). Tissue expansion has enabled the correction of such defects with hair-bearing skin and has revolutionized scalp reconstruction, offering results that were previously impossible to achieve (Figs. 25-10 and 25-11). Defects or deformities of up to half of the surface area of the scalp can be reconstructed with expansion of the remaining scalp. Serial expansion is sometimes necessary. In such instances, the expander is immediately replaced in a subgaleal pocket and the expansion process continued after an appropriate time for the wounds resulting from the most recent procedure to heal.

Incisions for implantation of scalp expanders are best placed at the margin of the area planned for resection so that the incision eventually is at the advancing edge of an expanded scalp flap. The incision can also be placed within the area to be resected if the tissue is healthy. When possible, a radial incision is made at right angles to the long axis of the expander pocket to prevent tension on the incision line during expansion. The recipient site for the expander should be created at an adequate distance from the access incision to prevent tension on the suture line and possible tissue breakdown. The expander is best placed deep to the galea and superficial to the pericranium. This is a relatively avascular plane that dissects easily during creation of a pocket. This level of dissection prevents traumatizing of the overlying tissue and preserves its vascularity.

Kabaker et al³⁰ described the use of expanders for the treatment of male pattern baldness. They described a technique for implanting expanders and design of expanded flaps that created a double Y-shaped wound closure (Fig. 25-12). This procedure can offer dramatic results (Figs. 25-13 and 25-14). Other authors have also described their successful results with this technique, but proper patient selection is imperative.³¹ A minimum of 6 weeks to 2 months of scalp expansion is required before the transfer of expanded advancement flaps. The patient must understand the interval required for use of this method and the physical appearance during the expansion process.

Forehead Expansion

The expander is placed in the subfascial plane, deep to the frontalis muscle and superficial to the periosteum of the frontal bone, when the skin of the forehead is expanded. The anatomic location of the temporal branch of the facial nerve is considered in planning the incisions for placement of the expander and the design of the subsequent flap used for reconstruction.

Forehead skin can tolerate expansion well because of its thickness and vascularity. However, expansion of the forehead usually produces more pain than expansion of other areas of the head and neck. This limits the rate at which expansion can be performed. Expansion of the forehead and scalp often creates a depression or “bathtub” deformity in the underlying soft tissue and bone because of pressure from the expander and the effect of the capsule. Resorption of bone with thinning of the outer layer of the calvarium is sometimes observed, creating a depression after removal of an expander. This deformity resolves with time (Fig. 25-15).

Figure 25-16 shows a patient who was reconstructed with use of tissue expansion in multiple surgical stages for excision of a skin graft on the lateral forehead, temple, and superior cheek. The skin graft was deforming and had a poor color match with adjacent facial skin. The patient was also troubled with breakdown of the graft, resulting in recurrent ulcerations and poor tissue healing. Initially, two 250-mL rectangular expanders were implanted, one beneath the skin of the forehead and one beneath the parietal scalp. During the expansion process, the expander under the scalp became exposed because of a fold in the expander (see Fig. 25-6). Because of this, the scalp expander was removed prematurely, but sufficient scalp expansion had been achieved to enable the anterior advancement of the parietal scalp to restore a normal-appearing temporal hairline. The forehead expander was left in place and expansion continued to complete the expansion process. A total of 300 mL of saline was injected into the expander. The expander was then removed and an advancement flap was created and used to cover the left side of the forehead after removal of the skin graft.

The forehead and scalp expanders were effective in providing sufficient skin to enable the removal of the skin graft covering the left side of the forehead and to restore a normal temporal hairline. The patient still had a skin graft covering the zygomatic area. A third tissue expander was placed beneath cheek skin to create an expanded cheek advancement flap. The cheek flap was used to resurface the zygomatic area, enabling the complete resection of the skin graft covering the area. A similar case is shown in Figure 25-17, in which a large skin graft was excised from the temple aided by expanded forehead and scalp flaps.

Face and Neck Expansion

Expanders can be used to expand skin of the face, neck, and chest.³² The expander is generally placed in a more superficial tissue plane in the face and neck than it is in the scalp and forehead. Because many of the deformities to be corrected are large scars from burns and other trauma, dissection can be difficult when expanders are implanted and advancement flaps are created from the expanded skin. In the region of the cheek, extreme care is required to avoid damage to the facial nerve during dissection. The expander may be placed directly over the vicinity of the facial nerve and expansion performed without nerve impairment. When possible, incisions are placed in natural creases to allow the best long-term aesthetic results. When the skin of the cheek or neck is expanded, a periauricular facelift-type incision is often used for implanting the expander (Fig. 25-18).

Because the expander is placed more superficially in the face and the neck compared with the forehead and because the skin is thinner in these areas, the expanded skin may become very thin during the process (Fig. 25-19). The more rapid the expansion, the thinner the skin becomes and the greater the risk of tissue breakdown. The expander may be placed deep to the platysmal muscle in the neck. The author has not encountered problems when placing tissue expanders over vital structures such as the carotid artery, trachea, or larynx, but the surgeon is still obligated to observe patients closely for possible signs and symptoms of complications (Fig. 25-20).

Tissue expansion has been used to reconstruct traumatic defects of the mandible.³³ Successful bone grafting of the mandible has been used in conjunction with expanded neck flaps and expanded oral mucosa to provide an improvement in the form and function of the reconstructed mandible . The patient in Figure 25-21 sustained a gunshot wound to the face, resulting in the loss of the anterior mandible and overlying soft tissue in addition to a portion of the tongue, maxilla, and nose. Before the author’s care of this patient, he had multiple reconstructive procedures including skin grafts, myocutaneous flaps, and bone grafts, many of which failed because of poor vascularity of the traumatized tissue. Tissue expansion of the neck skin was recommended for the purpose of replacing the traumatized tissue and to add additional skin and soft tissue to the area of the chin. Two 250-mL rectangular expanders were implanted on either side of the neck through postauricular incisions. The expanders were placed superficial to the platysmal muscle, and expansion was continued for 2 months. Each expander was inflated to a total volume of 300 mL of saline. Once expansion was completed, the expanders were removed, advancement flaps were developed, and the deformity was reconstructed with the expanded tissue. At the time of repair, a small expander was inserted in a soft tissue pocket in the area of the missing section of the mandible. The expander served as a “spacer” preserving a cavity for subsequent placement of a bone graft. The expander also served as a stimulus to create additional soft tissue as a vascularized recipient site for the bone graft. Two previous bone grafts had failed because of poor vascularity and lack of sufficient soft tissue coverage of the grafts.

In anticipation of using an iliac crest bone graft for mandible reconstruction, titanium implants were placed into the crest concurrently with implantation of the last tissue expander. The implants became integrated with the iliac crest bone. The implants served to anchor a permanent denture after reconstruction. The implants were transferred with the bone graft to the anterior mandible.

The expander in the area of the chin was left in place for 8 weeks, serially inflating it to a volume of 30 mL of saline. After completion of expansion, the expander was removed and an iliac crest bone graft placed in the pocket created by the expander. The expanded soft tissue in the area of the chin and lower lip provided a thick capsule to protect the bone graft from exposure. To ensure survival of the bone graft, the patient was also treated with several sessions of hyperbaric oxygen. He did well and experienced no problems with infection or tissue breakdown. Permanent dental implants were eventually inserted, and the patient was able to eat foods of all types. He continues to do well 16 years after reconstruction.

The patient shown in Figure 25-22 was a 12-year-old girl with a giant pigmented hairy nevus covering the left side of her face. She was referred to the author after having laser treatment, dermabrasion, and electrolysis. It was elected to use tissue expansion before attempting surgical excision. A 500-mL crescent-shaped expander was inserted beneath the cheek skin through a facelift-type incision. A crescent-shaped expander was selected because it allowed maximum skin expansion across the central portion of the expander and minimized expansion at the ends of the expander. This reduced the size of standing cutaneous deformities after advancement of expanded skin. The crescent-shaped expander is most useful for repair of round defects, and the pigmented nevus was circular in configuration. The injection port was placed externally behind the ear (Fig. 25-23). The patient was frightened of needles and lived 2 hours in traveling time from the office. To relieve the patient from traveling such long distances for inflation of the expander, her father was instructed in how to perform sterile injections of saline through the external port. The external port provided an easy access for her father to inflate the expander and avoided the need for percutaneous needle injections. The patient tolerated tissue expansion well and was checked periodically to ensure that infection had not occurred.

The expansion process required a 10-week interval, injecting a total volume of 750 mL of saline. When the expanded skin measured four times the size of the anticipated defect, the expander was removed and an expanded skin flap advanced into position to assess whether the nevus could be completely removed. The expanded skin was sufficient to enable the resection of the entire nevus without excessive wound closure tension.

Expanders for Nasal and Ear Reconstruction

Myocutaneous flaps remain the preferred method for reconstruction of large deformities in which bulk and coverage of an open wound are required. Such is the case when nasal defects require a paramedian forehead flap. Expanders can be used as an aid to nasal reconstruction when forehead flaps are required.²¹ Forehead skin expansion provides the advantage of increasing the availability of skin and the ability to close the donor site without wound closure tension.

Tissue expanders have also been used for ear reconstruction.³⁴ In fact, the first use of an expander was for reconstruction of an auricle. The expander is usually inserted beneath the postauricular skin. Skin is expanded until there is sufficient tissue to cover a framework for the ear.

External Injection Port

Most surgeons have been hesitant to use external injection ports when expanding skin because of concerns of infection. For years, arteriovenous shunts, indwelling intravenous lines for nutrition or chemotherapy, fracture stabilization pins, and dental implants have been successfully used without the devices becoming infected. There are several advantages to use of an external injection port. A subcutaneous pocket for the port is not required, and this can reduce the complexity of the procedure and lessens the risk of hematoma or tissue breakdown in the area of the port. The port can also be easily replaced if it leaks. One of the most important advantages, especially for children, is that pain is avoided because there are no percutaneous injections. It is also easy to train nonmedical personnel to perform injections through the port.

The first reported series using external ports showed no increased risk of infections.³⁵ Subsequently, other authors have reported infections, but the incidence appears to be statistically the same for internal and external ports. An external injection port should not be used when the expander is replaced by prostheses such as breast implants.

Intraoperative Skin Expansion

In 1987, Sasaki reported his experience with the use of rapid intraoperative skin expansion.³⁶ Expansion is performed at the time of the surgery rather than leaving the expander implanted for a prolonged time. Sasaki first observed that with long-term expansion, intraoperative expansion just before removal of the expander created an additional 1 to 3 cm of available skin for construction of a flap. He also observed that this rapid expansion produced no adverse effect on the chronically expanded flap. These observations led to the use of rapid expansion for immediate closure of smaller defects.

Intraoperative expansion has been used in all areas of the body, and the amount of skin gained from these procedures varies. In 295 cases, Sasaki found that up to 2.5 cm of skin could be gained by intraoperative expansion. The skin of the scalp, nasal tip, and back is thicker and more resistant to immediate expansion than skin on the face, neck, or extremities. Sasaki suggested that more skin could be gained by using more than one expander placed beneath the skin surrounding the defect.

The technique of intraoperative tissue expansion consists of developing a subcutaneous pocket to accommodate the expander adjacent to the defect to be closed. The expander is inserted, and a series of inflations are performed. Repetitive inflation allows cyclic loading of the tissue as described by Gibson.⁶ Gibson noted that when tension is placed on skin, the initial stretch of skin is from displacement of fluid and ground substance in the dermis. The maximum amount of stretch obtained does not occur on the first stress load but after serial repetitive expansions of the tissue. After three or four load cyclings, microfragmentation of elastin fibers occurs, and collagen fibers realign in a more parallel orientation. The expander is inflated for 2 to 3 minutes with sufficient saline to cause tissue pallor and firmness. The expander is then deflated for 2 to 3 minutes. With each subsequent cycle, more saline can be injected and the measurement across the dome of the expander increases. After completion of intraoperative expansion, the expander is removed and the skin is advanced for a trial closure. It is important to observe bleeding from the edge of the expanded skin before creating a flap and transferring it. This ensures that tissue ischemia has not occurred from the expansion.

Laser Doppler flow studies of skin undergoing intraoperative skin expansion reveal a rapid decrease in blood flow during expansion. However, blood flow returns to nearly normal levels within 1 minute after deflation of the expander. Skin ischemia from expansion is observed more often in the distal extremities and can be avoided if the expanded flap is trimmed of skin until bleeding is observed before the flap is transferred. The highly vascularized skin of the head and neck areas makes ischemia from intraoperative expansion a rare problem.

The histologic changes in the skin associated with prolonged expansion leading to biologic creep (described earlier in this chapter) are not observed with intraoperative expansion. On histologic evaluation, there are no significant changes in the epidermis, dermis, subcutaneous tissue, or muscle. The origin of additional skin gained by intraoperative expansion is not known. Hayden³⁷ suggested that it is not a true gain. He suggested that the gain is from a more efficient undermining of the skin provided by expansion than is provided by simple subcutaneous dissection alone.

Complications

The rate of complications associated with tissue expansion is high, but most are minor. Manders et al³⁸ studied the rate of complications in patients undergoing tissue expansion to treat a wide variety of deformities. They defined a major complication as one that required specific treatment and altered the planned procedure. By use of these criteria, 25% of patients suffered major complications. Antonyshyn et al³⁹ reported an overall complication rate of 48%. However, sufficient tissue was generated to complete the planned reconstruction in 70% of the patients.

Erosion of the overlying skin is the most common complication associated with tissue expansion. This usually occurs at the incision site used for insertion of the expander but may occur in any area of the expanded skin. An access incision that is radial in relation to the axis of the anticipated defect reduces the risk of dehiscence. Antibiotic coverage is advised with any exposure of an implant. Exposure of an implant does not necessarily lead to failure of the procedure because significant skin expansion has usually occurred by the time this complication develops. If the exposure is at the injection port, expansion can usually proceed without interruption.

Rapid tissue breakdown usually occurs when exposure of an expander occurs in the center of the area of expanded skin. In such instances, the expander should be removed and the surgeon should proceed with the planned reconstruction. If necessary, re-expansion can be performed at a later time once the skin has healed adequately. When exposure at the incision site for insertion of the expander occurs and expansion is not complete, the expander can be partially deflated to reduce wound closure tension and the dehiscent incision surgically closed. The deflated expander is left in situ and re-expansion commenced once the dehiscent site has healed.

Infection associated with tissue expanders is rare in the head and neck area because of the abundant blood supply of facial skin.³⁸ Perioperative antibiotics are recommended when an expander is implanted initially and at the first sign of infection. If infection occurs during the expansion process and is not quickly controlled, the expander should be removed and the infection treated before re-expansion of the skin is attempted.

Mechanical failure of the expander is rare and is usually associated with physician error. The expander can be accidentally punctured when the expander is inserted or when sutures are placed during closure of the access incision. The most common problem is leakage of the tubing attaching the expander to the injection port when the tubing has been shortened with a connector to adjust the length. It is important to tie a suture on both sides of the connector used to shorten the tubing to ensure a tight seal and to prevent leakage. Leakage does not always necessitate removal or replacement of the expander. Several surgeons have reported successful expansion despite leakage from the expander.⁴⁰

Postoperative bleeding may lead to hematoma or seroma formation after expander implantation. Meticulous hemostasis and immediate partial inflation of the expander at the time of implantation assist with obliteration of dead space and provide internal compression. This reduces bleeding in the subcutaneous pocket. If hematomas do occur, careful serial aspirations may be necessary.

Expanding irradiated, scarred, or acutely traumatized skin may lead to failure. These skin conditions are not absolute contraindications for tissue expansion but may increase the risk of expander extrusion before adequate skin gain has occurred to complete the planned procedure. However, when it is used with caution, expansion has been shown to be successful under these conditions.⁴¹

The patient’s mental condition must be considered before the use of tissue expansion is recommended. Patient selection is important because of the change in appearance and length of time required to complete the expansion process. The surgeon should use this procedure with caution in a psychologically unstable patient. Even mentally stable patients may undergo psychological stress leading to a wide range of reactions, making it difficult to complete the expansion process.⁴² All patients must thoroughly understand the temporary deformity that expansion will cause as well as the risks and complications of skin expansion.

Summary

When Radovan first introduced the use of tissue expanders in 1976, the concept was met with skepticism because of the concern for infection and erosion of expanded skin. Fortunately, there were several surgeons who realized the tremendous potential of this procedure. It was this potential that led investigators to study the histologic and biologic response of skin to prolonged expansion. Tissue expansion has proved to be a useful addition to the surgeon’s armamentarium of reconstructive procedures. Despite the frequency of complications, the benefits far outweigh the risks in appropriate patients. Tissue expansion is the only reconstructive procedure that currently offers the capability of increasing the number of cutaneous cells available for incorporation into a skin flap. Skin expansion should be considered whenever other reconstructive surgical procedures will not provide an acceptable result and where skin expansion is likely to ensure a far superior functional or aesthetic result.

References