Tissue expansion

TISSUE EXPANSION PRINCIPLE AND APPLICATION

1. TISSUE EXPANSION PRINCIPLE AND APPLICATION Dr. Amit Kumar Choudhary SR Plastic and Reconstructive Surgery RIMS,Imphal Moderator-Dr. AK. Ibohal Singh

2. HISTORY OF TISSUE EXPANSION Neumann induced soft tissue growth with a subcutaneously implanted balloon in an attempt to reconstruct an external ear deformity. Radovan and Austad simultaneously evolved the concept of purposeful soft tissue expansion with use of an implanted silicone balloon . Radovan's device contained a self-sealing valve through which saline was periodically injected to increase size of the prosthesis . Austad's prosthesis was devised as a self-inflating device using osmotic gradients driven by salt placed within the expander.

3. BIOLOGY OF TISSUE EXPANSION

4. Epidermis Early after placement of the prosthesis, significant thickening of the epidermis is evident. Within 4 to 6 weeks, epidermal thickness generally returns to initial levels, but some increase in thickness persists for many months. Hair follicles and accessory skin structures are compressed but no evidence of degeneration. Animal studies demonstrate that there may be an increase in number of hairs and density proportional with expansion. Melanocytic activity is increased during expansion but returns to normal within several months after completion of reconstruction

5. Dermis The dermis decreases rapidly in thickness over the entire implant during expansion. Dermal thinning persists at least 36 weeks after expansion is completed . A dense fibrous capsule is formed around the implant, which becomes less cellular over time. The capsule is thickest at 2 months of expansion . Progressive collagenization with well-organized bundles develops during 3 months. Dystrophic calcification may occur when a hematoma resolves or when the prosthesis is repeatedly traumatized. Expanded tissue demonstrates a quantitative increase in collagen content of the dermis . After expansion, the relative proportions of type I and type III collagen are not significantly changed in the dermalepidermal or subcutaneous-capsular interface. Mitotic activity in the capsule fibroblast is maximum about 96 hours after expansion. The application of a constant pressure beyond 96 hours results in progressive decrease in mitotic activity

6. Muscle Muscle atrophies significantly during the process of expansion, whether the prosthesis is placed above or below a specific muscle . The effects on human muscle after expansion have demonstrated occasional histologic ulceration . Focal muscle fiber degeneration with glycogen deposits and mild interstitial fibrosis have been noted. Some muscle fibers show disorganization of the myofibrils in the sarcomeres . Expansion of skeletal muscle is not a stretching process but rather a growth of the muscle cell accompanied by an increase in the number of sarcomeres per fiber.

7. Cranial Bone There is a decrease in bone thickness and volume in cranial bone beneath the expander, but bone density is unaffected. An increase in bone volume and thickness occurs predominantly at the periphery of the expander. Osteoplastic bone resorption occurs beneath expanders, and a periosteal inflammatory reaction is seen at the periphery of the expander. Cranial bone appears to be significantly more affected than long bone is. Long bone remodeling begins within 5 days after removal of the expander, and the long bone is completely normal within 2 months.

8. Vascularity of Expanded Tissue It has been clinically and histologically demonstrated that a large number of new vessels are formed adjacent to the capsule. The content of collagen fibers in existing vessels initially decreases after expansion . Elastic fibers in existing blood vessels initially increase , probably as a response to mechanical stress. Angiogenesis probably occurs secondary to ischemia of the expanded tissues. C ells expressing vascular growth factor is significantly increase.

9. SURVIVAL Flaps elevated in expanded tissue have significantly greater survival areas compared with acutely raised and delayed flaps.

10. Ultrastructure of Expanded Tissue The epidermis demonstrates a reduction of intercellular distance and a significant decrease in the undulation of the basal lamina . The dermis displays large, compact bundles of collagen fibers oriented in parallel fashion over the implant surface. Active fibroblasts are found in the expanded dermis . Myofibroblasts develop in the deep dermis adjacent to the capsule . Skeletal muscle demonstrates pressure atrophy with increased mitochondria and abnormal rearrangement of sarcomeres .

11. Molecular Basis for Tissue Expansion Intracellular tension and cell structure are maintained by a system of microfilaments within the cytoplasm. These microfilaments act to transduce signals to adjacent cells and play a critical role in initiating transduction cascades within the cell. Protein kinase C plays a pivotal role in signal transduction. Mechanical strain on cell walls activates inositol phosphatase , phospholipase A2, phospholipase D, and other messengers.

12. Activation of these components results in protein kinase C activation. Protein kinase C is associated with nuclear proteins, intracellular signals can be transmitted to the nucleus. Many growth factors, including platelet-derived growth factor and angiotensin II, play a role in strain induced cell growth. Platelet-derived growth factor has a effect of stimulating cutaneous cell proliferation. Transforming growth factor-β production has also been demonstrated in stretch in vitro models and has been implicated in extracellular matrix products.

13. The Source of Increased Tissue from Expansion The increase in skin surface area over the expander includes normal skin brought in from adjacent areas as well as new skin generated by increased mitosis. Increased mitotic activity in the epidermis directly overlying the expansion.Serial inflations of the prosthesis result in serial increases in tritiated thymidine uptake. With deflation of the implant, a significant decrease in the rate of the epidermal mitosis below normal baseline occurs.

14. IMPLANT TYPES

15. Radovan's expander Radovan's expander consisted of a silicone prosthesis with two valves, each connected to the main reservoir by silicone tubing. One valve was used for injection; the other was used as a means to withdraw fluid. Technologic improvements resulted in a single valve for both purposes. The filling reservoir may be incorporated directly into the prosthesis. Such devices have the advantage of avoiding the remote port. The valve in the integrated prosthesis can be difficult to palpate. Breast reconstruction with these prostheses has become popular. .

16. Expanders with distal ports Remote filling ports. Advantage of minimizing the risk of implant puncture during inflation. The distal , self-sealing injection port and inflation reservoir are connected to the prosthesis by a length of tubing. This allows the injection port to be placed away from the expander pocket. It is also possible to move the inflation port of a distant reservoir to the exterior of the body; this location facilitates inflation, particularly when the expansion is accomplished by family member.

17. DISTAL PORT

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

19. Self-inflating expanders Self-inflating expanders have become available largely through Europe. These contain osmotic hydrocolloids that cause migration of extracellular water through the silicone membrane of the device. The first such expander was devised by Dr. Austad and was used experimentally. It was not approved by the Food and Drug Administration

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

21. Incision planning and implant selection The proposed type of flap – advancement - rotation - Interpolation The simpler the flap, the less the potential for complication. planning (1) incisions are incorporated into tissue that will become one margin of the flap (2) aesthetic units are reconstructed (3) scars are in minimally conspicuous locations (4) tension on suture lines is reduced.

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

23. The size of the implant The size of the implant selected should closely relate to the size and shape of the donor surface. An implant equal to or slightly smaller than the donor area is selected. In general, the use of multiple small expanders is better than the use of one large expander. Inflation of multiple prostheses proceeds more rapidly and complications are fewer. Multiple expanders also allow the surgeon to vary the plan for reconstruction after expansion An integrated valve and a distal inflation port should be considered on a case-by-case basis.

24. Implant and distal port positioning If a remote filling port and reservoir is chosen,it must be placed superficially in subcutaneous tissue ,where even an extremely small port is easily palpable under stable skin. To minimize discomfort, it is occasionally possible to position a filling port in an area that is relatively less sensitive. The port should be placed in a location that will not be subjected to pressure . Bony prominences are avoided

25. Implant inflation strategy and technique Implants should be partially inflated immediately after wound closure. This allows closure of “dead space” to minimize seroma and hematoma formation. It also smoothes out the implant wall to minimize risk of fold extrusion. Enough saline is placed to fill the entire dissection space without placing undue tension on the suture line. Serial inflation usually starts 1–2 weeks after initial placement. Inflation reservoirs seal best when a 23-gauge or smaller needle is used. A 23-gauge butterfly intravenous needle is especially useful.

26. Frequent small-volume inflations are better tolerated and are physiologically more suited to the development of adequate overlying tissue than are large infrequent Inflations inflations proceed until the patient experiences discomfort or blanching of the overlying skin. Devices such as pressure transducers and oxygen tension monitors are available to help determine proper inflation. An objective inspection of the patient’s response is usually a reliable indicator of appropriate inflation. Serial inflations proceed until an adequate amount of soft tissue has been generated to accomplish the specific surgical goal.

27. Tissue expansion in special cases

28. Burns Reconstruction should be carried out after all burns have and scars have matured. Planning is particularly important in these cases so that a minimum number of suture lines is produced and that these suture lines do not cross aesthetic units. Significant late distortion and contracture may result in excessive scars placed in burned tissue, particularly in the facial area

29. Tissue expansion in children Skin and soft tissue are always thinner in children than in adults. These tissues are probably better vascularized but less resistant to trauma. Tissue expansion has a higher complication rate in children than in adults. Major complication risk – particularly extrusion – is more common at the second, third, and fourth serial expansion. This is particularly true in the head and neck (with the exception of the scalp). Small-volume inflation at frequent intervals is especially useful in children because the amount of pain generated is considerably less.

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

31. Myocutaneous flaps such as the latissimus dorsi and pectoralis can be expanded to almost double their surface area, allowing coverage of almost any defect on the abdomen or thorax. Expanders of up to 1000 Ml can be placed beneath such flaps and rapidly expanded.

32. Expanded full-thickness skin grafts Donor defect is usually created by harvesting full-thickness grafts. The placement of a large tissue expander beneath the donor site can result in a large full-thickness graft that is particularly useful in resurfacing large areas . The best color matches are generated when the full thickness graft is expanded and harvested as close as possible to the recipient site. The periorbital area and the area around the mouth are particularly well suited to reconstruction with expanded full-thickness grafts harvested from the supraclavicular area. Expanded full-thickness grafts are very helpful in reconstructing defects of the forehead . A single full-thickness graft can be harvested from the supraclavicular area or from under the breast fold.

33. The full-thickness graft is approximately 10–15% larger than the recipient area. Expanded full-thickness skin grafts require more immobilization than split thickness. A bolster dressing or, ideally, a VAC sponge dressing is required. The graft is sutured in place and a VAC sponge placed over the graft; 125 mmHg of negative pressure is maintained for 4 days.

34. APPLICATION OF TISSUE EXPANSION

35. HEAD AND NECK The skin of the face can be subdivided into five tissue specific areas : 1. The scalp 2. The forehead is a continuation of the scalp, but it is distinguished from the scalp by its thick skin, large number of sebaceous glands, and lack of hair. 3. The nose is embryologically related to the forehead, so it closely mimics the forehead in color, texture, and sebaceous gland content. 4 . The lateral cheek areas, neck, and upper lip have fewer sebaceous glands; the skin is thinner, and the hair-bearing pattern is significantly different in quality and quantity from that on the remainder of the body. 5. The skin of the periorbital areas is extremely thin and pliable, containing a minimal number of sebaceous glands

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

37. The darker the hair, the more visible the thinning is. Individuals who have large defects and require extreme expansion may achieve better results by lightening the hair with dyes. Advancement or rotation flaps achieve the best results, particularly when the anterior hairline is reconstructed.

38. Forehead The forehead is anatomically and histologically identical to the scalp except for its different numbers of sebaceous glands and hair-bearing follicles. Reduction or increase of the surface area of the forehead by 20–25% is not usually readily apparent after appropriate hair styling . By expanding the scalp in conjunction with expanding the forehead, better symmetric brow positioning is achieved while maintaining the normal hairline. Expansion of the forehead is useful in many craniofacial anomalies with low hairlines. Expansion of the remaining forehead is accomplished and moved into a cephalad direction. The intervening hair-bearing scalp is excised

39. Lateral face and neck The type of skin on the lateral facial areas and neck is essentially the same. A large Mustardé expanded rotation flap can be developed on the neck for use in facial reconstruction. In children, there is a higher risk of extrusion problems in the expansion of this area of the face . Adults, such reconstruction can be accomplished with relative ease. The flap is based inferiorly and medially.

40. Nose Reconstruction of major defects of the nose, including total nose reconstruction, may be facilitated by pre expanding the forehead skin . when total nose reconstruction is performed, expansion of the entire forehead with a 400–600-mL prosthesis generates an adequate number of large, well- vascularized flaps to accomplish both total nose reconstruction and closure of the donor site . Because the color and texture of the forehead are ideally suited to reconstruction of the nose, this procedure makes reconstruction of any nasal defect possible.

41. A cranial bone or rib graft is taken to reconstruct the dorsum of the nose. This is either secured to the remaining nasal bone or attached by a plate to the skull. The nasal cartilage is reconstructed bilaterally with cartilage from the conchal bowl.

42. Ear Most cases of microtia and traumatic ear deformities can be reconstructed without expansion. Expansion is helpful when skin and soft tissue are insufficient for reconstruction. As with all ear reconstructions, a child should be approximately 7 years of age before reconstruction is begun.

43. Periorbital area with expanded full-thickness grafts The periorbital area contains skin that is soft and pliable. Little tissue in the periorbital area can be expanded or move easily. When large areas require reconstruction, fullthickness skin grafts from expanded donor sites are recommended. Replacement of aesthetic units – the entire periorbital area or the upper or lower lid – gives the best result .

44. Reconstruction in the breast, chest, trunk, and extremities Tissue expansion was introduced by Chemar Radovan in 1982 to facilitate breast reconstruction in post mastectomy patients because these patients were found to have insufficient chest wall tissue for placement of the implant.

45. The hypoplastic breast Tissue expansion has played an important role in the reconstruction of both acquired and congenital breast hypoplasia . Management of the deformity depends on the degree of breast asymmetry, the nature of the deformity, the quality of the chest wall soft tissue, and the age of the patient at presentation.

46. The immature breast Management of young adolescents presenting with breast asymmetry. Adolescence is a critical time that is characterized by intense social pressures and self awareness of a developing physique, so failure to address the problem of breast asymmetry can result in psychological problems. These patients do not need full maturity for reconstruction.

47. Correction of Poland syndrome Poland syndrome involves - abnormal development of the breast - thoracic wall deformities - deformities of the upper extremity - vertebral anomalies. Poland syndrome exhibits a uniform absence of the sternal head of the pectoralis major muscle. Abnormalities in the anterior ribs and costal cartilages and deficiencies of the muscles of the scapular area, including the latissimus dorsi . Other findings include deficiency of subcutaneous tissue; hypoplasia , aplasia , or malposition of the nipple–areola complex; and deficiency of breast tissue.

48. Expansion of the trunk The trunk and abdomen are well suited to tissue expansion in individuals of all ages. Because of the large adjoining surface area from which tissue can be recruited, large prostheses can be placed and flaps quickly expanded. Large deformities, such as burns, giant hairy nevi, and other congenital anomalies, the expanders are inflated maximally and the flaps are advanced. The prostheses are left in place and re-expansion is carried out in the subsequent weeks. In the abdomen, two or three serial expansions are usually well tolerated.

49. Expansion in the extremities Skin and soft tissues of the extremities tolerate tissue expansion well. The capsule that develops adjacent to the expander has a resilient surface that can be transposed over joints and tendons to decrease adhesions.

50. COMPLICATIONS

51. IMPLANT FAILURE Despite design improvements, the use of an excessively large needle or the inadvertent puncture of the implant can lead to implant deflation. To maximize sealing of the valve, the implant reservoir should be entered at a 90° angle. If there is any question about the location of the inflation reservoir, radiologic or sonographic techniques may be helpful.

52. INFECTION The introduction of bacteria to the wound in the perioperative period is the most common cause of early infection. Areas susceptible to lymphedema , such as traumatized lower extremities, carry a significantly higher rate of infection. An area of copious lymphatic drainage, such as the neck or the groin, also tends to accumulate lymphatic fluid around a prosthesis and is more susceptible to infection. If infection occurs late in the course of expansion, the prosthesis can be removed and the expanded tissue advanced after irrigation of the infected cavity.

53. IMPLANT EXPOSURE Implant exposure can occur both early in the postoperative period and after a protracted course of expansion. Treatment of the exposed implant depends on the timing of exposure. Exposure early after placement is usually related to inadequate dissection or use of an excessively large prosthesis that abuts on wound closure. If the prosthesis becomes exposed soon after placement, it is best to remove it and reoperate 3–4 months later. Late exposure is usually related to excessively rapid or overzealous inflation. If minimal or late exposure occurs during the course of expansion, the procedure can continue with the use of antibiotic creams on the exposed area: In this situation, multiple, rapid fillings are done to generate adequate tissue. Reinforcement of the compromised overlying skin with paper tape is sometimes helpful. Most flaps survive and

54. COMPROMISE AND LOSS OF FLAP TISSUE To ensure vascularity,one should attempt to maintain a major axial vessel in the expanded tissue.

55. Thank you