Shan R. Baker, MD

The relatively recent advent of tissue expansion for medical purposes precludes the availability of extensive knowledge concerning the physiologic and histologic changes that occur during controlled expansion of the skin. This paper reviews the basic science and clinical research that has been conducted to investigate the changes and summarizes the findings. It can be concluded that flaps harvested from skin previously expanded have an improved survival rate compared to similar flaps developed in nonexpanded skin. Increased vascularity to either the skin, the capsule that forms around the expander, or both probably in some way accounts for the improved survival. Controlled expansion of the skin results in the creation of additional new skin at the expense of thinning the dermis and subcutis. This thinning is associated with an overall decrease in tensile strength of the expanded skin. The increase in surface area gained from skin expansion probably varies according to the type of skin expanded and the underlyingtissues that serve as a foundation for the expander. HEAD & NECK 1991;13:327433

It is amazing to realize that for thousands of years, skin expansion has been occurring. Because it was such a natural event, it was overlooked by the medical profession. The simplest example is the expansion of the abdominal wall of a pregnant woman in response to a growing uterus. Likewise, during pregnancy, the breasts increase their volume 3 or 4 times normal, while

From the Department of Otolaryngology-Head and Neck Surgery, Universify of Michigan Hospitals, Ann Arbor, Michigan. Address reprint requests to Dr. Baker at the Department of Otolaryngology-Head and Neck Surgery, University of Michigan Hospitals, 1500 E. Medical Center Drive, Box 0312, Ann Arbor, MI 48109-0312. Accepted for publication December 10, 1990. CCC 0148-b103/91/040327-07 $04.00 0 1991 John Wiley & Sons,Inc.

Fundamentals of Expanded Tissue

the overlying skin accommodates this expansion maintaining normal appendages and thickness. Tissue expansion has been used for centuries by various cultures to enhance their concept of beautification. African women of certain tribes place large plates in the lower lip to greatly enlarge this structure. Women in Burma place rings around the neck to enhance linear growth. Tissue expansion for medical purposes was first reported in 1905 by Codvilla, who attempted to lengthen the femur.' Magnuson in 1908 noted no functional damage after attempts to experimentally lengthen bones and soft tissue of the leg.' In 1921 Putti also reported on efforts to lengthen the leg.' Neuman was the first to expand skin using an inflatable balloon.2 The expander was buried beneath the skin above the ear. Gradual inflation allowed sufficient expansion of the skin of the side of the head to allow coverage of a cartilage graft used to reconstruct a subtotally avulsed auricle.2 The success of Neuman apparently had no impact on the medical community because it was not until 19 years later that another report concerning this technique surfaced when Radovan successfully expanded an arm flap using a temporary tissue expander. The flap was used to resurface an adjacent defect of the arm following removal of a l e ~ i o n In . ~ 1982 Radovan reported his experience in 68 patients in which he performed breast reconstruction after mastectomy using a temporary tissue e ~ p a n d e rAt . ~ the time of his report, the late William Grabb commended Dr. Radovan for his innovativeness and predicted that tissue expansion would have a major

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impact on reconstructive ~ u r g e r y .Dr. ~ Grabb's prediction has come true. Tissue expansion has opened a whole new frontier in reconstructive surgery and is now part of the surgical armamentarium of most plastic and reconstructive surgeons. Since Radovan's early attempts, a number of scientific papers have been presented describing tissue expansion techniques for reconstruction of a variety of bodily deformities. Tissue expansion is particularly suited for reconstruction of the head and neck because this region of the body has such a wide variety of distinctive types of skin, each distinguished by specific color, texture, subcutaneous fat, hair-bearing qualities, and innervation. In instances where local tissue of similar quality is insufficient to reconstruct a cutaneous defect of the head and neck, tissue expansion provides a valuable reconstructive option, because it enables the surgeon to expand like tissue. The relatively recent advent of tissue expansion for medical purposes precludes the availability of extensive knowledge concerning the physiologic and histologic changes that occur during temporary controlled expansion of the skin. The purpose of this paper is to review what is known about these changes. This review will provide the clinician interested in using tissue expansion for reconstructing cutaneous defects of the head and neck a fundamental knowledge of the histologic and physiologic manifestations of expanded skin. VASCULARITY OF EXPANDED SKIN

Cherry et a1.6 attempted to determine if randompattern flaps elevated in expanded skin of the pig survived to the same or greater length than acutely raised random-pattern flaps. They also compared the survival of flaps elevated in expanded tissue to delayed flaps. The expanded flaps had a mean increase in surviving length of 117% over controlled flaps, which was statistically significant. The delayed flaps had an increase in survival of 73% over controlled flaps, which was also statistically significant. There was no significant difference in survival between expanded flaps and delayed flaps. Morphologic studies using radiographic techniques on 1 pig demonstrated increased vascularity with tissue expansion. Cherry and colleagues concluded that, in addition to providing increased surface area with controlled expansion, flaps raised in expanded

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skin have a significantly augmented surviving length. They postulated that the mechanism for this increased survival length was enhanced vascularity. These vascular changes may be related to physical forces associated with expansion acting as a stimulus for angiogenesis. Sasaki and Pang7 also studied skin vascularity after expansion in a pig model. Total capillary blood flow was significantly higher in delayed and expanded random-pattern flaps as compared to acute random skin flaps. Leighton et al.' studied the vascularity of axial pattern cutaneous and musculocutaneous flaps raised from expanded tissue of pigs. Similar to those findings by Cherry et a1.6 and Sasaki and Pang7 for random-pattern flaps, Leighton and colleagues demonstrated enlargement of the vascular system of both types of axial flaps.' They demonstrated angiographically and histologically increased vascularity of expanded skin. The expanded capillary network was histologically most evident in the capsules surrounding the expanders and in the dermal layer of both expanded cutaneous and musculocutaneous flaps. Capillary counts were highest in the papillary dermis decreasing into the reticular dermis. The muscular layer of expanded musculocutaneous flaps showed an expanded vascular tree by angiography, but no increase in the density of vessels was seen histologically. Sasaki and Krizekg studied blood flow in expanded skin by use of microsphere perfusion studies. They also found enhanced blood flow in the dermis of expanded skin, as well as marked vascularity of the capsule surrounding the expander. Because of the rich blood supply to the capsule, Sasaki recommends leaving the capsule intact as much as possible following deflation of the expander and use of the expanded skin for reconstruction. However, as much capsule as necessary should be resected if the capsule retards advancement, transposition, or adequate unfurling of the expanded skin (G.H. Sasaki, personal communication). The mechanism for the cutaneous vascular changes observed in expanded skin is unknown. Some researchers have suggested the mechanism may be the same as that which occurs with the delay phenomenon by realignment ,of vessels, closing of arterial venous shunts, neovascularization, or the depletion of neurohumoral vasoactive substances." However, the mechanism and physiologic forces influencing cutaneous blood flow are totally different between the phenome-

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non of delay and expansion. The vascular changes that occur with tissue expansion and with delay may overlap but should be considered separately until each is better understood." PHYSIOLOGY O F EXPANDED SKIN

Austad et a1.12 demonstrated that no thinning of the epidermis took place in the skin of guinea pigs undergoing tissue expansion by means of a self-inflating implant. This study provided circumstantial evidence that tissue expansion results in a net increase in donor tissue. This stimulated Austad et al.13 t o measure the epidermal mitotic activity of guinea pig skin during tissue expansion using tritiated thymidine and other confirmatory techniques. Inflation of the tissue expander resulted in a threefold elevation of epidermal mitotic activity within 24 hours, followed by a gradual return to normal baseline over 2 to 5 days. Conversely, deflation of the expander caused a transient decrease in epidermal mitotic activity. Moreover, using autoradiographic methods and the Feulgen technique, the authors showed that expansion of the epidermis caused a marked increase in DNA syntheses in keratinocytes paralleling a proportional increase in mitotic figures in these cells. The above 2 studies led Austad et al.13to conclude that tissue expansion in their experimental model represented a dividend derived from the ability of the epideral cell to replicate. Based on their considerable clinical observations they believe a similar phenomenon occurs in humans where it is not just a matter of stretching skin, but the actual formation of additional new skin which has all of the attributes of the original tissue. The authors postulate that tissue expansion causes a decrease in cell density in the basal layer of the skin and that cell density may regulate skin mitotic activity. A lower cell density results in a greater cell proliferation, resulting in the growth of additional skin. The concept of creating additional skin has been supported by Johnson et al., who studied dermal and epidermal response to skin expansion in the pig.14 They expanded skin over a 6-week period and studied the skin with respect to surface area, thickness, histologic changes, and collagen content. Epideral thickening and dermal thinning were observed. Dermal thinning persisted 36 weeks after expansion. Dermal collagen content decreased, although collagen density remained unchanged. Overall, collagen content of the skin increased. The clinicians con-

Fundamentals of Expanded Tissue

cluded that their data supported a theoretical gain in the dermal layer, as well as epideral layer in response to tissue expansion. The thinning of tissue, particularly observed over the center of an expander probably accounts for the decrease in tensiometric properties observed in experimentally expanded skin. Schneider et al.15 evaluated the tensile properties of expanded skin of guinea pigs. They observed that skin located centrally over the expander demonstrated significantly weaker stress strain values than nonexpanded skin. They observed a 67.4% reduction for tensile strength between expanded and nonexpanded skin. No statistically significant difference in tensile strength was seen for skin located peripheral to the center of the expander compared to nonexpanded skin. Overall, expanded skin demonstrated an average of 35% reduction in tensile strength.15 The maximum amount of additional skin obtained from prolonged tissue expansion has not been studied, but is probably related to the rate and duration of the expansive process and to the intrinsic tensile strength of the expanded skin. Machida et a1.16 produced a mean increase in skin surface area of 135% by expanding guinea pig skin over a 6-week period. Van Rappard et al.17 studied the increase in surface area of actual expanders (in vitro) as well as expanding pig skin (in vivo) with the help of a mathematic approach. They recorded the increase in surface area on full expansion of a number of expanders of different size and shape. They found that the in vitro increase in surface area as actually measured from the expander nearly (range 97% to 99%) approaches that expected mathematically. However, the measured increase in skin surface area when implanted beneath pig skin (in vivo) was only about 35% of the mathematically expected increase in surface area. This was probably related in part to sinking down of the base of the implant, since the expanders were p€aced over the gluteus maximus muscle rather than bone. In addition, the implants were located beneath very thick skin with considerable subcutaneous fat, which prevented the skin from accurately conforming to the expander. These researchers also observed a clear difference between the surface area gain for differently shaped tissue expander^.'^ They found that for expanders with a round base, the in vivo gains were 25% of the average of the calculated gains. For rectangular and crescentic expanders, these percentages were 38% and 32%, respec-

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tively. The authors concluded that in the clinical situation the appropriate size expander should be one in which the surface area of the expander base is 2.5 times as large as the defect to be closed when using rectangular or crescentic expanders. In the case of round expanders, this correction factor of 2.5 holds true for the diameter of the expander base rather than the area of the base. Lee and colleagues" have shown in animals that use of smooth muscle relaxants injected into the space around the expander may facilitate the rate of expansion; however, this technique has not yet been applied to humans. Similarly, Osetinsky and colleague^'^ evaluated the effects of collagenase and the hormone relaxin on skin expansion in the pig. A dermajet was used to inject these drugs into the skin overlying tissue expanders. After daily administration of the drugs, the expanders were inflated to an internal pressure of 100 mm Hg each day for 7 days. Sites treated with each of the drugs showed significant increase in total volume of expansion over that observed in saline-treated control sites. Histopathologic examination of the skin showed no obvious difference between saline-treated sites and relaxin-treated sites, but collagenase-treated skin exhibited areas of collagen fiber disruption and microhemorrhage. HISTOLOGY OF EXPANDED SKIN

Pasyk et al. performed a quantative analysis of the thickness of human skin and subcutaneous tissue following prolonged expansion." They observed that the epidermis of expanded skin underwent significant thickening after 5 weeks to 5 months of expansion. In contrast, the dermis and subcutaneous tissue were significantly thinner after expansion. This phenomenon has also been observed in prolonged expanded animal skin. The dermis rapidly becomes thinner within the first few weeks of expansion. Later, the rate of thinning slows considerably. Capsules surrounding the expanders were observed to form in all cases of skin expansion. Capsules were thickest after 2 to 2.5 months of expansion. Expanded tissue was studied in 1 patient 2 years after cessation of expansion. The skin was noted to have similar thickness as nonexpanded tissue and had no remnant of fibrous capsule. There was complete restoration of previously atrophic adipose tissue in the subcutis. The researchers noted similar observations in 3 guinea pigs, when 1 year after removal of the expander no residual fibrous capsule was found."

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Fundamentals of Expanded Tissue

In a similar vein, Leighton et a1.8 studied the histologic changes which occurred to expanded axial cutaneous and musculocutaneous flaps in the pig. Experimentally, there was observed to be a differential thinning of all tissue layers except the epidermis. The adipose layer was most effected, being 30% to 50% thinner than in controlled flaps. Less thinning of the muscle layer was noted. The epidermal thickness remained unchanged, and minimal dermal thinning occurred. The greatest thinning occurred over the dome of the expander, where intraluminal pressure vectors were applied to the overlying soft tissue at a right angle. The amount of thinning decreased toward the periphery of the expansion zone, where less direct pressure vectors were applied by the underlying expander. The histology of expanded skin has also been studied at an ultrastructural level. Prolonged expansion of guinea pig skin is associated with a reduction of the intracellular spaces of all layers of the expanded epidermk'l Intracytoplasmic tonofilaments are noted to be larger than normal, forming tonofibrils within the cells of the epidermis. The expanded dermis contains large bundles of compacted collagen, especially in the reticular dermis; however, the structure of elastic fibers remains unchanged. These large bundles of collagen fibers represent abundant quantities of immature collagen synthesized by the observed elevated numbers of fibroblasts within the dermis. Similar to other researchers, Pasyk et al.'l found a paucity of adipose tissue in the subcutaneous tissues following expansion. In addition, thickened collagen fibers in the interlobular fat spaces were observed. Pasyk et al.'l also studied the histology of the capsule forming around expanders and the ultrastructural changes that take place in the muscle beneath the expanded skin. They found the capsule to be composed of very compacted fibrous connective tissue that contained abundant collagen fibers and active fibroblasts. In the skeletal muscle beneath expanders, they observed marked changes. Sarcomeres were abnormally arranged and myofilaments were irregularly dispersed. The number and size of mitochondria were increased compared to normal muscle. Larger amounts of sarcoplasm in relationship t o myofibrils was also observed. Many researchers studying the histology of skin expansion have noted the lack of inflammatory response to tissue expanders. In the absence

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of infection an unusual number of acute or chronic inflammatory cells are not found in either the epidermis, dermis, o r in the capsule surrounding the implant.'l IMMEDIATE TISSUE EXPANSION

There is minimal information available concerning the physiologic and histologic changes that take place during rapid or immediate expansion. Immediate mechanical stretching changes the elasticity of skin by the phenomenon called creep. The physiologic changes coinciding with creep are (1) dehydration of tissue by the displacement of fluids and mucopolysaccharide ground substances, (2) microfragmentation of elastic fibers, (3) alignment of random positioned collagen fibers into a more parallel orientation, and (4) migration of tissue in the direction of the force Cyclic loading, that is stretching followed by relaxation as opposed t o continual stretching, appears to be the most effective method of recruiting extra ti~sue.'~ Rapid intraoperative tissue expansion is another method of exerting cyclic mechanical tension on the skin, which appears to be more effective than simply applying tension to the skin using skin hooks or other methods of directly applying traction. Sasaki" has studied the blood flow and histologic changes to skin of the head and neck undergoing immediate serial expansion. Using laser Doppler, blood flow was noted to decrease rapidly during expansion but recovered to near-normal levels within a minute following the deflation of the expander. No significant histologic changes in the epidermis, dermis, dermal appendages, adipose tissue, or muscle were observed. Special collagen and elastin stains demonstrated a slight degree of alignment of collagen fibers but no evidence of microfragmentation.22 Marks et al.25evaluated cutaneous blood flow in skin rapidly expanded over 5 days. Blood flow was measured 3 days later using radiolabeled microspheres. Blood flow to skin flaps harvested from the expanded skin was significantly greater than a similar skin flap developed from skin overlying a noninflated expander. Goding et a1.26 performed a study on pigs by using the dermofluorometer t o assess the effects of rapid tissue expansion on cutaneous blood flow, but without creating a pedicled flap. They observed an increase in blood flow of expanded skin compared to nonexpanded skin, but only after deflation of the tissue expander. The increased blood flow returned within 6 days to the

Fundamentals of Expanded Tissue

level measured prior to deflation of the expander.26 By day 6 following deflation, Goding and colleagues noted that the nutrient blood flow of the expanded skin was significantly less than in skin elevated without placement of an expander.26This finding suggests no long-term increase in the cutaneous blood flow resulting from rapid skin expansion. It also suggests that more rapidly expanded skin has less enhancement of vascularity compared to slower, more prolonged expansion. These authors suggested that the reason for the observed increase in flap survival in rapidly expanded skin is related to the temporary increase in blood flow to the expanded skin after removal of the tissue expander. This temporary increase in vascularity may be sufficient to allow increased flap survival. Machida et a1.16 and Sasaki (personal communication) quantitatively evaluated the effects of prolonged and immediate expansion and simple traction (load cycling) on guinea pig skin. Intraoperative immediate expansion consisted of rapid expansion for 3 minutes followed by deflation of the expander for 3 minutes. This was repeated for 3 cycles. Prolonged controlled expansion consisted of expanding skin over a 6-week period by weekly injections. They found that prolonged expansion produced a mean increase in skin surface area of 135%,whereas rapid expansion resulted in a 30% increase. Load cycling resulted in an almost negligible amount of skin increase. All 3 techniques exhibited some immediate postexpansion stretch back of equal proportions, but this was not quantitated. Clinical work on the part of this author, as well as G.H. Sasaki (personal communication), has noted strength back of both rapidly expanded and prolonged expanded skin to be approximately 20% to 30% of the surface area gained by the expansive process. To assist in retarding stretch back, it is helpful t o replace any missing skeletal framework at the time of transposing or advancing expanded skin over a defect. In addition, placing strategically located dermal sutures beneath the expanded skin flap in a quilt-like fashion may be helpful (G.H. Sasaki, personal communication). There appears to be a real gain in tissue through the use of immediate or rapid tissue expansion. Clinically, Sasaki has marked a 1-cm grid on the skin overlying a noninflated expander and has shown that each 1-cm square of skin overlying the dome of the rapidly inflated expander will increase in dimension from

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1.3- 1.5 cm (G.H. Sasaki, personal communication). Following deflation and reconstruction, each of the squares maintained an increase in their dimensions of from 0.3-0.5 cm (G.H. Sasaki, personal communication). The combination of increased wound tension and perhaps increased mitoses in the basal layers of the skin, over and above that expected as a result of trauma from surgery, has been postulated as the reason for this persistent gain in surface area (G.H. Sasaki, personal communication). Although in the clinical situation from 1-3 cm2 of additional skin surface area can be achieved by immediate tissue expansion, much more surface area can be gained by the use of prolonged expansion. The marked differences in skin surface area gained by various techniques of applying mechical forces to the skin have led Machida et a1.16 to conclude that immediate intraoperative expansion is effective primarily for limited expansion and closure of small defects, whereas prolonged tissue expansion provides the greatest amount of skin augmentation compared to other techniques. CONCLUSION

Before the process of tissue expansion can be fully understood, there must be additional basic science research exploring the physiologic and histologic changes that take place. The effects of expansion time, rapidity of expansion, expander

shape and volume, location of expanders, age of the skin expanded, and a whole host of other factors which may influence physiologic and histologic changes in tissue are unknown. It can be concluded, however, that flaps harvested from prolonged expanded skin have an improved survival rate compared with similar flaps developed in nonexpanded skin. Increased vascularity t o either the skin or the capsule that forms around the expander, or both, probably in some way accounts for the improved survival. There is also probably enhancement of blood supply of rapidly expanded skin, but to a markedly lesser degree than more slowly expanded skin. It can also be concluded that prolonged expansion of skin results in the creation of additional new skin at the expense of thinning of the dermis and subcutus. This thinning is associated with an overall decrease in tensile strength of the skin. The increase in surface area gained from skin expansion probably varies according to the type of skin expanded, how rapidly the skin is expanded, and the underlying tissues that serve as a foundation for the expander. Controlled, prolonged skin expansion produces larger surface area gains than immediate or more rapidly expanded skin. Discontinuation of the expansion process apparently results in a “normalization” of the skin with the thickness of the dermis and subcutaneous tissue slowly returning t o that of nonexpanded tissue.”

REFERENCES

1. Versaci A, Balkovich M. Tissue expansion: history. In: Habal M, ed. Advances in plastic surgery, Vol. 1. Chicago: Year Book Publishers, 1984:95. 2. Neuman CG. The expansion of an area of skin by progressive distention of a subcutaneous balloon. Plast Reconstr Surg 1957;19:124. 3. Radovan C. Adjacent flap development using expandable silastic implant. Presented at the Annual Meeting of the American Society of Plastic and Reconstructive Surgeons. Boston, Massachusetts, 1976. 4. Radovan C. Breast reconstruction after mastectomy using the temporary expander. Plast Reconstr Surg 1982;69:195- 208. 5. Grabb W. Discussion of breast reconstruction after mastectomy using the temporary expander by Chedomir Radovan. Plast Reconstr Surg 1982;69:207. 6. Cherry GW, Austad E, Pasyk K, McClathcey K, Rohrich ELI. Increased survival and vascularity of randompattern skin flaps elevated in controlled, expanded skin. Plast Reconstr Surg 1983;72:680-685. 7. Sasaki GH, Pang CY. Pathophysiology of skin flaps raised on expanded pig skin. Plast Reconstr Surg 1984;74:59. 8. Leighton WD, Russell RC, Feller AM, Eriksson E, Mathur A, Zook EG. Experimental pretransfer expan-

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sion of free-flap donor sites: 11. Physiology, histology, and clinical correlation. P l a t Reconst Surg 1988;82: 76-84. 9. Sasaki GH, Krizek TJ. Functional blood flow and skin viability in random skin flaps constructed in expanded skin: delay phenomenon in action. Presented at the Plastic Surgery Research Council, Durham, North Carolina, May 19,1983. 10. Leighton WD, Russell RC, Marcus DE, Eriksson E, Suchy H, Zook EG. Experimental pretransfer expansion of free-flap donor sites: I. Flap viability and expansion characteristics. Plast Reconstr Surg 1988;82:69- 75. 11. Van Beek AL, Adson MH, Discussion: Experimental pretransfer expansion of free-flap donor sites: I. Flap viability and expansion characteristics. Plast Reconstr Surg 1988;82:85-87. 12. Austad ED, Pasyk KA, McClatchey KD, Cherry G. Histomorphologic evaluation on guinea pig skin and soft tissue after controlled tissue expansion. Plast Reconstr Surg 1982;70:704. 13. Austad ED, Thomas SB, Pasyk K. Tissue expansion: dividend or loan? Plast Reconstr Surg 1986;78:63-67. 14. Johnson PE, Kernahan DA, Bauer BS. Dermal and epidermal response to soft-tissue expansion in the pig. Plast Reconstr Surg 1988;81:390- 395.

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15. Schneider MS, Borkow JE, Cruz IT, Marangoni RD, Schaffer J , Grove D. The tensiometric properties of expanded guinea pig skin. Plast Reconstr Surg 1988;81:398-403. 16. Machida BK, Liu-Shindo M, Sasaki GH, Chandrasoma P, Rice DH. Immediate vs chronic tissue expansion. Presented a t the Fifth International Symposium on Facial Plastic and Reconstructive Surgery. Toronto, Canada, June 1989. 17. van Rappard JHA, Molenaar J , van Doorn K, Sonneveld GJ, Borghouts JMHM. Surface-area increase in tussue expansion. Plast Reconstr Surg 1988;82:733837. 18. Lee P, Squire CA, Bardach J. Enhancement of tissue expansion by anticontractile agents. Plast Reconstr Surg 1985;76604-610. 19. Osetinsky GV,Marion MS, McCaffrey TV. Modification of collagen in tissue expansion. Surg Forum 1988;39:559-561. 20. Pasyk KA, Argenta LC, Hassett C. Quantitative analysis of the thickness of human skin and subcutaneous tissue

Fundamentals of Expanded Tissue

following controlled expansion with a silicone implant. Plast Reconstr Surg 1988;81:516-523. 21. Pasyk KA, Austad ED, McClatchey KD, et al. Electron microscopic evaluation of guinea pig skin and soft tissues expanded with a self-inflating silicone implant. Plast Reconstr Surg 1982;70:37-45. 22. Sasaki GH. Intraoperative sustained limited expansion (ISLE) as an immediate reconstructive technique. Clin Plast Surg 1987;14:563-573. 23. Gibson T. The physical properties of skin. In: Converse JM, ed. Reconstructive plastic surgery, Vol. I. Philadelphia: WB Saunders, 19775’0-77. 24. Gibson T,Kenedi RM, Craik JE. The mobile microarchitecture of dermal collagen: a bioengineering study. Br J Surg 1965;52:764-770. 25. Marks MW,Burney RE, Mackenzie JR, et al. Enhanced capillary blood flow in rapidly expanded random pattern flaps. J Trauma 198626913-915. 26. Goding GS, Cummings CW, Trachy RE. Tissue expansion and cutaneous blood flow. Laryngoscope 1988; 98919-922.

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Fundamentals of expanded tissue.

The relatively recent advent of tissue expansion for medical purposes precludes the availability of extensive knowledge concerning the physiologic and...
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