Tissue Rearrangement Techniques and Regional Flaps




BACKGROUND



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Extirpative gynecologic cancer surgery may result in partial or full-thickness defects of the abdominal wall. Although minor defects can be repaired primarily, large or composite defects present a significant challenge requiring careful planning to obtain a successful reconstruction. A multidisciplinary team, including gynecologic oncology, urology, general, and plastic surgery, may be required for treatment of the patient with gynecologic cancer. Goals of abdominal wall reconstruction in these patients are to restore structural integrity of the abdominal wall musculofascial system and provide stable wound coverage.



Repair of complex abdominal wall defects can be divided into 2 main modalities: autologous tissue or nonautologous (prosthetics or biomaterials). Depending on the clinical situation, either or both modalities may be required. This chapter delineates preoperative and anatomic considerations that factor into reconstructive decision-making, with an emphasis on techniques of autologous tissue repair. Prosthetics and biomaterials are discussed in Chapter 20.




INDICATIONS AND CLINICAL APPLICATIONS



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Functions of the abdominal wall include protection of intra-abdominal organs, provision of dynamic support for respiration and upright posture, and assistance in Valsalva for coughing, urination, and defecation. Difficulty performing these functions due to abdominal wall discontinuity will not only impact function, but health-related quality of life as well. Gross herniation of intra-abdominal contents can create ­obvious difficulty in social situations. By contrast, small ­hernias, while not as visible, are at greater risk for incarceration and strangulation. Indications for reconstruction of abdominal wall defects thus range from functional to aesthetic.



Few absolute contraindications to abdominal wall repair exist. Hemodynamically unstable patients can be temporarily closed using negative pressure wound dressings or large intravenous bag coverage with definitive closure performed at a later date. In patients desiring elective repair of chronic ventral hernias or wounds, thorough preoperative evaluation and counseling must be performed. These patients often have significant medical comorbidities; thus, the benefits of major abdominal surgery must be weighed before undertaking repair. Such procedures can cause significant cardiopulmonary embarrassment both intraoperatively and postoperatively, particularly for chronic ventral hernias with a significant loss of domain. Asymptomatic, high-risk medical patients at low risk for incarceration may be managed conservatively with observation.



Defect Etiology



Abdominal wall defects requiring reconstruction may result from tumor extirpation, incisional hernia, abdominal wound infection, or a combination thereof. Malignant pelvic tumors extending to the anterior abdominal wall may require wide resection of myofascial structures, subcutaneous tissue, and/or skin, depending on the extent of tumor invasion. Incisional hernia following prior laparotomy has a reported incidence of 2% to 11%.1,2 Risk factors for developing this complication include elderly age, morbid obesity, malnourishment, immunosuppression, and previous abdominal surgery. Medical conditions such as connective tissue disorders and those associated with increased intra-abdominal pressure (eg, chronic cough, constipation, ascites) also predispose to incisional hernia development. Soft tissue infections of the abdominal wall may follow laparotomy or prior mesh repair. Mesh infection often necessitates removal with staged or delayed reconstruction.




ANATOMIC CONSIDERATIONS



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Assessing the Wound



1. Wound bed status


The extent and timing of reconstruction depends in part on the level of bacterial contamination of the wound bed. Otherwise healthy patients with clean, stable wounds ­following tumor resection can have definitive reconstruction performed immediately. By contrast, if a wound is infected or heavily contaminated, or if additional abdominal surgeries are planned, then definitive reconstruction is delayed. Infected or contaminated wounds should undergo multiple irrigation and débridements until clean, at which point they can be ­temporarily closed. Frequently used techniques for wound temporization include applying absorbable Vicryl mesh, negative pressure wound dressings, or both followed by split-­thickness skin grafting over the granulated bowel. Once the wound is epithelialized or the skin graft has matured, delayed reconstruction with hernia repair can be entertained. It is best to allow at least 6 months before reconstruction begins in order to permit resolution of local inflammation and scar maturation.



Special consideration should be given to wounds in areas with prior irradiation or extensive scar tissue following previous surgery. These wounds share in common poor vascularity with atrophic and nonpliable soft tissues. Attempts to obtain closure with local tissue advancement through undermining have a high likelihood of failure. Treatment with vascularized flaps from outside the region is required to optimize healing.



2. Characteristics of the defect


The next factor to evaluate is the extent of the skin/soft tissue deficit and the fascial defect size. Small defects of the skin and subcutaneous tissue (< 5 cm) can usually be closed primarily if undermining of the skin permits tension-free reapproximation. Larger defects require additional tissue in the form of local or regional flaps, or skin grafting. It is also important to differentiate between relative and absolute tissue deficits. Subacute or chronic wounds suffer from retraction of local tissues, whereas tumor resection results in absolute tissue loss. Knowing the etiology of the defect is helpful when planning reconstruction because a small or moderate relative tissue deficiency can often be overcome with local advancement, whereas an absolute deficiency requires additional tissue recruitment to close the defect.



Fascial and composite defects involving both skin and fascia require restoration of fascial continuity to prevent herniation of intra-abdominal contents. Small fascial defects (< 3–5 cm) can be closed primarily if the repair is tension free. Larger fascial defects require formal reconstruction using prosthetic mesh, components separation, or autologous flaps. Regardless of the reconstructive method chosen for either the skin or fascial component, the most important principle is a tension-free closure. Tension predisposes to wound dehiscence, hernia development, and abdominal compartment syndrome.



3. Position of the defect


A final aspect to consider is the location of the defect on the abdominal wall. Central defects are often amenable to closure with local skin advancement and fascial components separation from both sides. By contrast, lateral defects are more challenging to close because abdominal wall skin or fascia can only be released for advancement from one side. Defects adjacent to the costal margin or iliac crest are hindered by the rigidity of these fixed structures.




PREOPERATIVE PREPARATION



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Box 19-1 KEY SURGICAL INSTRUMENTATION




  • General plastic surgery trays and set-ups, including electrocautery, bipolar cautery, a variety of hand-held retractors, and fine dissecting instruments such as McIndoe forceps and tenotomy scissors are sufficient for most procedures



  • Dermatome if skin grafting is planned



  • Doppler probe and machine if an axial pattern flap is planned




History and Physical Examination



As with all surgical candidates, preoperative assessment of the patient should begin with a thorough history and physical examination. Patients with cardiopulmonary disease or diabetes should undergo evaluation by specialists for medical optimization and clearance prior to surgery. Malnourished patients should be nutritionally optimized to promote adequate wound healing postoperatively. Smokers may be referred to smoking cessation programs and should be encouraged to quit smoking at least six weeks prior to surgery, if possible, in an effort to prevent wound healing complications.



Physical examination should take note of the patient’s general condition, body habitus, and body mass index. Palpate the abdomen to identify hernias or a rectus diastasis. Knowledge of the patient’s prior surgeries is helpful, as well as identifying existing scars on the trunk, abdomen, and legs. Such information is critical in determining available tissue donor sites for reconstruction. In patients with multiple prior abdominal wall scars, the vascular supply to the existing skin needs to be considered when designing additional incisions. Previous incisions can be incorporated into the design of the reconstruction to limit scar burden and minimize potential watershed areas.



Imaging Studies



For patients who have had prior abdominal procedures or chronic ventral hernias, it is helpful to obtain preoperative imaging to assist in reconstructive planning. Computed tomography (CT) scan is the preferred modality. It is helpful in evaluating the patient’s intestinal anatomy, the location and size of fascial defects, and extent of prosthetic material placed during previous surgeries. CT scans obtained with intravenous contrast can clarify the presence and patency of vascular pedicles, which may be important for flap reconstruction.



Key Surgical Instrumentation



In the operative suite, general plastic surgery trays and instruments should be readily available, including standard electrocautery, bipolar cautery, a variety of handheld retractors and find dissecting instruments such as McIndoe forceps and tenotomy scissors. If a skin graft is planned as part of the procedure, then a dermatome should be made available. Similarly, if an axial pattern flap is going to be performed, then a Doppler probe and machine will help assess vascularity.




SURGICAL PROCEDURES



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Box 19-2 MASTER SURGEON’S PRINCIPLES




  • Thorough preoperative planning is essential



  • Have a backup surgical plan available




Attempts to formulate an algorithm for abdominal wall reconstruction are difficult because of the numerous variables involved. A more useful method is to climb the reconstructive ladder starting with the simplest surgical options before proceeding to the more complex. The best reconstructive plan is one that provides a reliable, durable closure with the least potential morbidity. The surgeon should always have a secondary option planned in the event that the first option fails or is unavailable due to extended extirpation.



Reconstruction cases often benefit from coordination with other services in the event that further abdominal wall manipulation is required such as a urinary conduit or colostomy creation. The plastic surgeon may help plan skin incisions at the commencement of a major extirpative procedure to aid reconstruction and preserve flap vascular pedicles.



Repair of Fascial Defects



1. Primary closure


The simplest method of fascial repair is primary closure, which can be attempted in defects smaller than 3 to 5 cm.3 It is recommended that the fascia is closed with nonresorbable monofilament suture in continuous fashion.4 The benefit of continuous suture is that the tension is distributed evenly over the length of the defect, which is in contrast to interrupted or figure-of-8 sutures. The surrounding tissues should be mobilized to ensure the fascia could be reapproximated in a tension-free manner. Repairs preformed under tension result in fascial strangulation with necrosis and are more likely to fail. Large, full-thickness abdominal wall retention sutures are not a means to compensate for a tight fascial closure and contribute to both skin and fascial necrosis.



Incisional hernias repaired with hernia sac excision and primary suture closure demonstrate recurrence rates ranging from 25% to 63%, even for small defects less than 5 cm in size.5,6 Therefore, if the fascial closure is tight, then there should be a low threshold for use of prosthetic mesh.



2. Prosthetics and bioprosthetics


Since the late 1980s, the use of prosthetic mesh for abdominal wall reconstruction has dramatically increased and has since become the standard of care for incisional hernia repair.7 For abdominal wall defects resulting from tumor resection, the use of synthetic mesh represents a simple and readily available method of fascial replacement. Additional advantages include the absence of donor site morbidity and its ability to result in a tension-free closure. Significant disadvantages of mesh include mesh extrusion, infection, bowel adhesions, and enterocutaneous fistula formation. Its use also provides static—rather than dynamic—support for the abdominal wall, potentially leading to respiratory embarrassment. Synthetic mesh is contraindicated in infected and heavily contaminated wounds, and it should be used with caution in cases with tenuous overlying soft-tissue coverage. It is best reserved for clean wounds with fascial defects not amenable to either primary closure or component separation (discussed below).



The potential morbidity of synthetic mesh-related complications spurred the development of more biocompatible prosthetics. A variety of biologic meshes have been introduced which have gained popularity for use in many facets of reconstruction. Derived from human or animal sources, these bioprosthetic consist of a decellularized collagen-based extracellular matrix, which acts as a scaffold for host tissue ingrowth and regeneration once implanted in the body. This affords biologic mesh distinct advantages over synthetic mesh, namely the ability to resist infection and be used in contaminated fields. Disadvantages include increased expense and higher rates of hernia recurrence secondary to matrix attenuation over time.8 High-level studies evaluating acellular dermal matrices in abdominal wall reconstruction have not yet been published, which makes their role difficult to define. At this time, the main utility of these matrices appears to be in cases where synthetic mesh is contraindicated such as in infected or heavily contaminated fields. A more detailed discussion of prosthetics and bioprosthetics is given in Chapter 20.



3. Free fascial graft


An alternative to synthetic or biologic mesh is the use of autologous fascial grafts to repair abdominal wall fascial defects. The most commonly used fascial graft is the tensor fascia lata (TFL), initially described by Kirschner in 1913.9 The fascia lata graft is strong, versatile, and easy to harvest. Harvest is performed through a longitudinal incision along the lateral aspect of the thigh. The skin and subcutaneous tissue are elevated over the area of fascia to be harvested. Care should be taken not to injure the underlying muscle while incising and elevating the graft. The entire fascia lata can be harvested save for the posterior condensation of the iliotibial tract, which should be preserved to prevent lateral knee instability. To repair the abdominal wall, the graft is sutured in place using an inlay technique with the smooth deep surface of the fascia lata oriented toward the viscera. The graft must be covered with local or regional skin flaps for it to revascularize. Studies have demonstrated that fascial grafts retain the parallel orientation of collagen fibrils10 and become revascularized11 after implantation.



With the advent of synthetics and bioprosthetic meshes, use of autologous fascial grafts has fallen out of favor. The limited quantity and need for a donor site can make autologous grafts a less attractive option than readily available off-the-shelf prosthetics. Conversely, the ease of graft harvest and minimal donor site morbidity of grafts such as the fascia lata make them appealing in situations in which synthetics are contraindicated or components separation is not possible. The autologous nature of the grafts makes them a useful biocompatible tool for contaminated cases or when prior synthetic meshes have failed.



4. Components separation


A method of fascial repair that restores dynamic abdominal wall function is the components separation technique. First described by Ramirez in 1990,12 this technique involves medial advancement of composite myofascial flaps on the abdomen, which can be performed unilaterally or bilaterally. The procedure is ideal for midline defects of the abdominal wall in which the absolute quantity of tissue loss is small, such as a chronic hernia where the abdominal musculature has retracted.

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Jan 12, 2019 | Posted by in GYNECOLOGY | Comments Off on Tissue Rearrangement Techniques and Regional Flaps
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