PRINCIPLES, TECHNIQUES, AND BASIC SCIENCE
CHAPTER 10 TISSUE EXPANSION
ASHLEY K. LENTZ AND BRUCE S. BAUER
Tissue expansion provides additional cutaneous tissue, allowing the surgeon to optimize contour and color match in a given reconstructive effort. Careful planning and follow-through are necessary to achieve the desired outcome and minimize complications.
Although the genesis of modern-day tissue expansion is credited to Radovan1 and Austad,2 the technique takes some of its roots from early lessons in distraction osteogenesis. Bone traction with either internal or external devices at the turn of the 20th century paved the way for the concept that mechanical stress on tissue leads to lengthening. In the mid-1950s, Neumann3 became the first surgeon to use an expansile implant when he used a latex balloon to enlarge periauricular skin for a traumatic ear deformity. Despite these early efforts, it was not until 20 years after Neumann’s report that tissue expansion was revisited. Charles Radovan,1 a resident at Georgetown, reintroduced the concept of expansion when he inserted a contemporary device with an internally placed port. Shortly thereafter, Eric Austad2 produced a self-inflating device. In 1982, the first National Tissue Expansion Symposium was sponsored by the Plastic Surgery Educational Foundation. This marked the recognition of a new advance in reconstructive surgery. Since that time, expansion has been applied to a multitude of reconstructive problems, with applications demonstrated in both local expansion and distant expansion for subsequent graft and flap transfer. Better understanding of expansion has allowed modifications in flap design, increasing its value as a reconstructive option.4
When mechanical stress is applied to skin over time, two phenomena occur: mechanical creep and biologic creep. The former is based on morphologic changes that occur on a cellular level in response to the applied stress. Mechanical creep is essentially cellular stretch. However, biologic creep is a cellular proliferation that results from the disruption of gap junctions and increased tissue surface area. Growth of the tissue by cellular proliferation restores resting tension of the stretched tissue to baseline.5 The epidermis gets thicker with concurrent thinning of the dermis and alignment of collagen fibrils. These effects are maximized at 6 to 12 weeks post-expansion. On a molecular level, various cytokines are induced in response to expansion.6
The vascularity of an expanded flap is superior to its nonexpanded counterpart in both number and caliber of vessels.7 Moreover, angiogenic factors such as vascular endothelial growth factor are expressed in expanded tissue at a significantly higher level when compared with nonexpanded controls. This augmentation in blood flow is attributable to the capsule that forms around the prosthesis. Because of the similarity between expanded and delayed flaps in vessel caliber, tissue expansion is regarded as a form of the delay phenomenon. An expanded flap, therefore, is a delayed flap.
Tissue expanders differ in size, shape, and type of filling valve. Expanders can be standard, customized to the donor site (breast), or can be designed to fill differentially to provide tapering of tissue. In terms of shape, they follow three basic patterns: round, rectangular, and crescent. The more commonly used include the round and rectangular types. The crescent-shaped prostheses were originally designed in an effort to minimize dog-ears at the donor site, but have fallen out of favor. It has been recognized that the rectangular expanders allow for additional expanded tissue, thereby increasing the possible choices for flap design (Figure 10.1).
Expander volumes have a wide range and the choice varies according to the anatomic site of expansion and need for gained tissue. Round and rectangular expanders range in size from less than 100 cc to greater than 1,000 cc in volume. Sterile technique is used to deliver saline to the valve port, which may be integrated into the expander device or attached to the expander via silicone tubing of customized length. An integrated system is favorable if only one single pocket is undermined; however, the implant may be more prone to rupture during expansion. Remote ports avoid the danger of inadvertent prosthesis rupture, but have their own set of complications including flipping or migration of the device in vivo, as well as tube obstruction. In an effort to avoid these complications, the port tunnel should be conservative in size and the port should be placed over firm supportive tissue and secured with sutures if needed.
One aspect cannot be overemphasized: The design for flap expansion should be planned prior to surgery. Consideration for the incisions, expander placement, flap movement in relation to the defect, and postoperative scars require appreciable preoperative planning. Thorough discussions with the patient and family are critical for successful reconstruction. If home tissue expansion is planned, then we suggest a separate clinic session devoted to education of the patient and family with regard to the goals of expansion, expansion technique, and the need for keen observation of the skin throughout the process.
FIGURE 10.1. Rectangular tissue expanders. Size 350 and 500 mL tissue expanders with rectangular shape, thicker base plate, tubing, and a small and large remote filling port.
Donor site choice plays an important role in expansion as the surgeon strives to provide a good match for color, texture, and contour for an optimal aesthetic and functional outcome. Infection, unstable scars, and traumatized tissue of the donor site may lead to implant failure or extrusion. When placing expanders, attention is paid to the location of the incision. If the purpose is removal of a lesion, we recommend placing the incision within the lesion borders. Gentle handling of the skin flaps is mandatory, as rough or aggressive retraction of the flaps can lead to skin edge necrosis. The port should be placed in a region of firm skeletal support, such as rib, iliac crest, or anterior thigh. Partial fill of the expander at the time of placement (approximately 10% to 20% of its listed volume) assures that the expander is properly positioned and without surface folds. Soft, flexible expanders should be used and the redundant expander should be folded underneath the expander in order to avoid future interference with the port during filling. Large expanders measuring greater than 250 mL prove more effective and we routinely use 500 mL or larger expanders. We recommend the use of larger ports for even the smaller expanders in order to avoid flipping of the port and easier palpability. Small closed suction drains are used to close the potential dead space. In most cases, the expander pocket incisions are closed in a watertight fashion with 4-0 clear Nylon sutures and 4-0 Prolene running continuous sutures. Skin flaps are dressed with Bacitracin and Xeroform gauze followed by soft 4 × 4 fluffs. Patients may or may not require overnight admission for pain control and monitoring of the skin flaps for potential compromise or hematoma formation.
Serial expansion begins 7 to 10 days post-insertion, provided that the skin flaps are in excellent condition. Drains are removed within 10 days of surgery. After detailed training and education, pediatric patients participate in a home expansion protocol directed by the parent or guardian. It has been demonstrated that home expansion is safe and equivalent to office expansion with regard to successful outcome.8 Expansion should render the skin tense, but one should not expand until it is extremely painful to the patient or cause skin compromise. Both suggest overly aggressive expansion. The home expansion protocol typically lasts 8 to 12 weeks in preparation for transfer of the expanded tissue.
Although early dogma of tissue expansion emphasized expansion as a means of generating large advancement flaps, experience demonstrates that expanded transposition and rotation flaps are frequently preferable. Clearly, the increased vascular supply of the expanded flap places little limitation on the ingenuity of the surgeon in designing flaps unique to the varied recipient defects. Although requiring more planning and forethought, transposition of the flap provides greater versatility in flap design and range.4,9
HEAD AND NECK
Large areas of the scalp can be reconstructed using tissue expansion to replace the defect with hair-bearing scalp. The scalp is also the second most common site of reconstruction using tissue expansion as well as the area with which surgeons have the most familiarity. Scalp reconstruction is warranted in three scenarios: large congenital melanocytic nevi, scar and skin graft alopecia (Figure 10.2), and traumatic or iatrogenically caused craniofacial abnormalities. It has been thought that scalp tissue expansion may permanently affect cranial vault morphology; however, this is not the case. Temporary cranial molding occurs, but corrects within 3 to 4 months. In the treatment of congenital melanocytic nevi, larger expanders are placed serially in order to distribute the expansile forces evenly over the hair follicles. The scalp can double in size without causing obvious alopecia. When inserting the expanders, they should be placed in the subgaleal plane above the periosteum. Flaps should be designed with careful attention to the dominant vessels of the scalp, including the superficial temporal, postauricular, and occipital arteries and contributions from the supraorbital arteries. Finally, port placement in the preauricular region produces the least migration.
Expanded flap reconstruction of the forehead provides some of the most challenging cases because of the potential morbidity and disfigurement of the brow and hairline. One must have great respect for the aesthetic subunits to avoid late complications. We reported an aesthetic complication rate of 24% in forehead tissue expansion, including brow asymmetry, brow ptosis, altered hair direction, and anterior hairline asymmetry.10 Over the years, principles have been developed to minimize these complications: (a) bilateral expansion of normal forehead tissue is often successful for midforehead lesions; (b) serial expansion of the forehead is often required for hemi-forehead nevi; (c) supraorbital and temporal nevi are managed using a transposition of expanded normal skin medial to the nevus; (d) with minimal involvement of the temporal region, expanded parietal skin can be advanced to reconstitute the hairline; and (e) in cases of brow elevation, the abnormal brow can be returned to its preoperative position by interposing non–hair-bearing forehead skin.
Face and Neck
Once again, strict adherence to the aesthetic subunit principles is required to achieve optimal results. Careful planning for expander placement and flap incision will ensure that the final scars are “hidden” in natural creases such as the nasolabial fold. Undue tension on the middle and lower third of the face can result in lower lip droop, oral incontinence, and an asymmetric smile. The advancement of cervical skin flaps has an exceptional tendency to result in these complications. Therefore, we prefer to expand transposition and rotation flaps from the lateral cheek or neck and postauricular region. The use of multiple prostheses and overexpansion is recommended in order to further minimize these complications.
Expansion may also be applied to donor sites in preparation for full-thickness skin grafting.11 This technique eliminates the size of the graft as a limitation for reconstruction. A portion of the expansion provides for the graft tissue, while the remainder serves to allow for primary closure of the donor site. Expansion of the abdomen results in aesthetic wound closure with the ability to hide the donor site scars. The supraclavicular skin is ideal for grafts on the face due to the excellent color and texture match. Once expanded, these full-thickness grafts have the same characteristics as their unexpanded counterparts in terms of durability, texture, contraction, and growth.
Beyond the obvious indications for breast deformities, tissue expansion has multiple applications on the trunk for treatment of giant congenital nevi, vascular malformations, and contour defects.
The lower abdomen may be the most easily expanded anatomic site. It can be used for full-thickness graft donor sites, as mentioned above, or as donor tissue for transposition flaps for coverage of the anterior thigh. Expansion may also be used to expand free tissue transfers. We have successfully used the expanded free transverse rectus abdominis musculocutaneous (TRAM) flap to treat shoulder defects as well as those of the upper extremity below the elbow.13 While the lower abdomen can be successfully used as a donor site, the upper abdomen and anterior trunk must be cautiously regarded, as there exists the unwanted potential for breast distortion.
FIGURE 10.2. Cranial defect after a train accident. A. Right cranial defect. B. Multiple expanders were placed. C. Elevation of scalp flaps after expansion. D. Placement of titanium mesh. E. Postoperative result.
Expansion of the posterior trunk is the preferred modality for the treatment of congenital nevi of the back and buttock (Figure 10.3). Whether advancing the skin caudally or cephalad, serial expansion is frequently required for excision of extensive lesions. Expansion can begin as early as 6 months of age for treatment of pediatric nevi and proves easier in early childhood as compared with later age. The lower back may be expanded to develop large transposition flaps for coverage of the buttock. The use of large expanded transposition flaps has allowed the excision and reconstruction of giant nevi with fewer procedures and more aesthetic and functional positioning of the final scars.13
Expanders and expandable implants are used in breast surgery for postmastectomy reconstruction and treatment of congenital anomalies.
Implant-based breast reconstruction remains the most common choice after mastectomy (Chapter 59). The relative ease and rapidity of subpectoral expander placement make it a highly requested surgical option among women. Tissue expanders are typically placed under the pectoralis muscle superiorly, while a sling of acellular dermis or serratus anterior muscle covers the expander inferiorly. Exchange of the expander for a permanent prosthesis may be performed after the patient has undergone serial outpatient expansion to a desired breast volume. This topic is covered in detail in Chapter 59.
Expanders have been used as spacers during “delayed primary” breast reconstruction. The expander placed at the time of mastectomy preserves the skin envelope while awaiting final pathology results. If radiation is warranted, the expander holds the original skin envelope until delayed reconstruction can be performed. If no postmastectomy radiation is indicated, then the patient may proceed with either implant-based or autologous breast reconstruction.
Tissue Expansion in the Treatment of Congenital Breast Anomalies
Expanders can be helpful as “spacer” in the correction of congenital breast anomalies. Requests for breast habilitation come from patients with breast agenesis associated with Poland syndrome, idiopathic unilateral breast hypoplasia, and iatrogenic breast asymmetry as a consequence of juvenile breast bud damage. Traditional wisdom has been to wait for maturity prior to correcting breast asymmetries. This strategy assures that the surgeon knows what needs to be matched on the opposite side. Although this solution may have been acceptable previously, today’s adolescent female has problems with changing in locker rooms, participating in sports activities, and wearing fashionable clothing. Questions of developing self-esteem, body image, and sexual identity further compound the issue of waiting. Expanders can function as an intermediate solution. This topic is covered in Chapter 64.
Many young women are happy with breast volume symmetry so that they appear normal in a bra. With this goal in mind, an expander can be placed as early as the opposite breast begins to develop and can be expanded over time. Aesthetic surgeons also use this trick to adjust breast size over time. Use of either an expander or an expander-implant in these cases may constitute an off-label use for these devices. Expanders are not constructed for prolonged use (i.e., over the 6 to 8 years of breast development). Postoperatively adjustable permanent implants are designed for longer term use but are supposed to have their ports removed promptly after complete fill to prevent implant deflation. As such, a discussion of these possibilities needs to occur prior to placement. The postoperatively adjustable implants come in sizes, shapes, and volumes particularly suited to use in this situation. Depending on how much native breast exists, these expanders can be placed subglandularly or submuscularly.
Once the patient reaches maturity, the expander can be replaced with a permanent implant and balancing procedures to match breast shape can be performed on the opposite breast for “out-of-a-bra” symmetry. In the case of a patient with Poland syndrome with significant infraclavicular soft-tissue deficiency, a latissimus dorsi flap can be transferred or a custom permanent implant manufactured at the time of definitive reconstruction.
Classically, the extremity is viewed as an unfavorable donor for an expanded flap. Complication rates in the limb are higher than those compared with other sites, and simple expansion does not provide a large amount of surface area with which to work. These facts have led us to find alternative options and creative methods for successful reconstruction of the extremity. Additionally, extremity expansion should be avoided in unstable or infected wounds.
A useful algorithm for complex defects has been devised for upper limb reconstruction.12,13 Based on our experience, successful contour and color match of the upper extremity comes from approaching it in thirds (proximal to elbow; midforearm; and the hands, web spaces, and fingers) and from whether or not the lesion is circumferential or noncircumferential. For proximal noncircumferential defects, expanded transposition flaps from the back or shoulder serve the purpose well. If the lesion is large and circumferential, covering the majority of the proximal arm, expanded free TRAM flaps are the method of choice. Distally, for large circumferential mid- or lower forearm lesion, expansion of the flank creates a pedicled carrier “sling” through which the forearm can be placed for 3 weeks prior to pedicle division (Figure 10.4). As previously reported, expanded full-thickness skin grafts from the abdomen or the groin remain the treatment of choice for reconstruction of fingers, webs, and hands.
Skin of the lower extremity lacks flexibility and requires complex solutions for wound closure. We have developed an algorithm for the treatment of congenital nevi of the lower extremity.14 This algorithm takes into consideration the size and location of the defect, as well as the age of the patient. Creative approaches for wound closure include expanded free flaps, expanded local transposition flaps (Figure 10.5), serial excision, and full-thickness skin grafts.
As mentioned above, site-specific complications may occur. Major complications include infection, implant exposure, and flap ischemia. Traditional dogma suggests that an early postoperative infection requires expander removal. However, an infection occurring late in the expansion course can occasionally be salvaged with antibiotic therapy.15 Exposure of the implant may be treated the same way, especially if the expander is located in a dependent portion of the open wound. Local wound care and oral antibiotics may be administered until the wounds close secondarily.
FIGURE 10.3. Giant congenital nevus of the back and buttock. A. Preoperative appearance. B. Expander placement. C. Multiple stages of expansion were required. D. Postoperative result.
Minor complications with expansion include transient pain during the expansion process, seroma formation, dog-ears at the donor site, and widening of the scars. The majority of these complications resolve in time or with minor surgical revision.
FIGURE 10.4. Congenital giant nevus of the upper extremity. A. Preoperative appearance. B. Expansion of the flank. C. Removal of the upper extremity nevus. D. Pocket created to cover the upper extremity defect. E. Postoperative result.
FIGURE 10.5. Lower extremity nevus. A. Posterior thigh tissue expansion. B. The expander was removed, the nevus was excised, and the posterior thigh flap was used to anchor the leg in a position of flexion in order to cover the defect. C. After flap division and inset.
1. Radovan C. Adjacent Flap Development Using Expandable Silastic Implants. Paper presented at the Annual Meeting of the American Society of Plastic and Reconstructive Surgeons, Boston, MA, September 1976.
2. Austad ED, Rose GL. A self-inflating tissue expander. Plast Reconstr Surg. 1982;70:588.
3. Neumann CG. The expansion of an area of skin by progressive distention of a subcutaneous balloon. Plast Reconstr Surg. 1957;19:124.
4. Bauer BS, Margulis A. The expanded transposition flap: shifting paradigms based on experience gained from two decades of pediatric tissue expansion. Plast Reconstr Surg. 2004;114:98-106.
5. DeFilippo RE, Atala A. Stretch and growth: the molecular and physiologic influences of tissue expansion. Plast Reconstr Surg. 2001;109(7):2450-2461.
6. Takei T, Mills I, Arai K, et al. Molecular basis for tissue expansion: clinical implications for the surgeon. Plast Reconstr Surg. 1998;102(1):247-258.
7. 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.
8. Mohmand MH, Sterne GD, Gower JP. Home inflation of tissue expanders: a safe and reliable alternative. Br J Plast Surg. 2001;54:610-614.
9. Bauer BS, Vicari FA, Richard ME. The role of tissue expansion in pediatric plastic surgery. Clin Plast Surg. 1990;17(1):101-113.
10. Bauer BS, Few JW, Chavez CD, et al. The role of tissue expansion in the management of large congenital pigmented nevi of the forehead in the pediatric patient. Plast Reconstr Surg. 2001;107(3):668-675.
11. Bauer BS, Vicari F, Richard ME, et al. Expanded full thickness skin grafts in children: case selection, planning and management. Plast Reconstr Surg. 1993;92:59-69.
12. Margulis A, Bauer B, Fine N. Large and giant congenital pigmented nevi of the upper extremity: an algorithm to surgical management. Ann Plast Surg. 2004;52:158-167.
13. Bauer BS. Commentary on Gosain AK et al. Giant congenital nevi: a 20 year experience and an algorithm for their management. Plast Reconstr Surg. 2001;108:632-636.
14. Kryger ZB, Bauer BS. Surgical management of large and giant congenital pigmented nevi of the lower extremity. Plast Reconstr Surg. 2008;121:1674-1684.
15. Adler N, Dorafshar AH, Bauer B, et al. Tissue expander infections in pediatric patients: management and outcomes. Plast Reconstr Surg. 2009;124:484-489.