The deep inferior epigastric perforator (DIEP) flap can be used to cover large defects of the proximal lower extremity, abdominal wall, perineum, vulva, and buttock. Pre-expanding DIEP flaps cause a possible delay phenomenon improving vascularity, decrease donor site morbidity, and increase the area that can be covered. Pre-expansion requires staged procedures, has risk of extrusion and infection, causes temporary contour deformity during the expansion process, and requires a longer course. Pre-expanded DIEP flaps can be a useful flap with proper patient selection and planning.
Key points
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Advantages of the pre-expanded deep inferior epigastric perforator (DIEP) flap include increased vascularity, primary closure of donor site, decreased donor site morbidity, local tissue use, and no need for microsurgery.
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Disadvantages include staged reconstruction, protracted timeline for serial expansion, and risks/complications associated with tissue expansion.
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During pre-expansion, make the incision according to final flap design, fixate the tissue expander in the subcutaneous plane, and wait a minimum of 4 weeks between final expansion and flap harvest.
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During flap harvest and inset, discard the lateral one-third of the flap, implement intraoperative Doppler monitoring throughout, and perform a pinch test prior to circumferential incision.
Introduction
The perforator flap has become an essential tool in the plastic surgeon’s reconstructive armamentarium since its introduction by Kroll and Rosenfield in 1988. Although initially described for lower posterior midline defects, perforator flaps have since been designated for use throughout the body. Understanding the vascular anatomy and dominant perforator location has increased flap selection options and improved customization for patients.
Taylor and Palmer mapped skin and cutaneous vascular anatomy in 1987, identifying an average of 374 major perforators per subject and introducing the concept of the “angiosome.” Perforator mapping laid the foundation for the “perforasome” theory, outlined by Saint-Cyr and colleagues, which encompasses the arterial vascular territory of a single perforator. Its characteristics and relationship to neighboring vascular territories were studied, and optimal surgical techniques were conjectured based on those principles. Clinical application of this knowledge allows for more predictable and dependable results in perforator flap surgery ( Fig. 1 ).
This article aims to delineate the anatomy, treatment goals, preoperative planning, operative principles, postprocedure care, and clinical results of the pre-expanded DIEP flap.
Introduction
The perforator flap has become an essential tool in the plastic surgeon’s reconstructive armamentarium since its introduction by Kroll and Rosenfield in 1988. Although initially described for lower posterior midline defects, perforator flaps have since been designated for use throughout the body. Understanding the vascular anatomy and dominant perforator location has increased flap selection options and improved customization for patients.
Taylor and Palmer mapped skin and cutaneous vascular anatomy in 1987, identifying an average of 374 major perforators per subject and introducing the concept of the “angiosome.” Perforator mapping laid the foundation for the “perforasome” theory, outlined by Saint-Cyr and colleagues, which encompasses the arterial vascular territory of a single perforator. Its characteristics and relationship to neighboring vascular territories were studied, and optimal surgical techniques were conjectured based on those principles. Clinical application of this knowledge allows for more predictable and dependable results in perforator flap surgery ( Fig. 1 ).
This article aims to delineate the anatomy, treatment goals, preoperative planning, operative principles, postprocedure care, and clinical results of the pre-expanded DIEP flap.
Anatomy of deep inferior epigastric perforator flap
First characterized by Koshima and Soeda in 1989, the DIEP flap is a transverse lower abdominal flap perfused by perforators of the DIEA. Nuances of DIEP flap anatomy are complex and variable; however, recent anatomic studies have elucidated major principles to optimize its use. The DIEA is the most significant artery supplying the skin of the anterior abdominal wall, and its pedicle ranges from 7.5 cm to 20.5 cm in length and 3.3 mm ± 0.4 mm in diameter, with 2 accompanying venae comitantes. Although there are anatomic variations, there are most commonly 2 main branches giving off medial and lateral row of perforators in the medial and lateral third of the rectus abdominis muscle, respectively. The most robust perforators are typically in the periumbilical region (see Fig. 1 ; Fig. 2 ).
Schaverien and colleagues used 3-D and 4-D CT angiography (CTA) and venography to study the arterial and venous anatomy of the DIEP flap. Their anatomic study determined that all perforators were located within 10 cm of the umbilicus. They found a mean of 5.3 perforators (range, 2 to 8) perforators greater than or equal to 0.5 mm in diameter per specimen. Perfusion occurred mostly through recurrent flow through the subdermal plexus, with horizontally oriented perforator complexes at the suprafascial level. Branches of the medial row perforators were seen to communicate with the medial row perforators across the midline at the level of the subdermal plexus as well as perfusing lateral row perforators bilaterally, with extension to zone IV (of Hartrampf zones of perfusion [ Fig. 3 ]). Lateral perforator vasculature, however, directed laterally with no visible perfusion of zone IV.
Wong and colleagues also expounded on the difference between medial and lateral row perforators in terms of DIEP flap vascular flow in their anatomic study. They determined that zone II perfusion was greater in medial perforators compared with lateral perforators, and zone III had greater perfusion from lateral perforators. Whereas medial perforators perfused zone II prior to zone III, the sequence of perfusion in lateral perforators was reversed.
Treatment goals and planned outcomes
Pre-expansion of the DIEP flap allows it to attain reconstructive goals, including coverage of large defects, primary closure of the donor site, and minimizing morbidity. Well known for its role in autologous breast reconstruction as a free flap, the DIEP flap also has been described in its pedicled form to repair defects of the proximal lower extremity, abdominal wall, perineum, vulva, and buttock. Despite its versatility and reliability, local donor tissue availability may limit its utilization for large defects. Through use of tissue expansion, the pre-expanded DIEP flap can now cover large defects in those regions. Tissue expansion is a principle of reconstructive plastic surgery in which mechanical stress applied to skin provides additional cutaneous tissue with the added benefit of improved vascularity through mechanical and biologic creep. Pre-expansion has routinely been performed with traditional flaps and only more recently utilized in perforator flaps. Pre-expansion of the pedicled DIEP flap allows for reconstruction of a variety of defects in select cases, maximizing the benefits of tissue expansion and pedicled perforator flaps while minimizing patient morbidity.
Preoperative planning and preparation
As with any major surgical procedure, it is imperative that surgeons optimize patients to the best of their ability and ensure that patients are able to withstand the rigors of surgery and the postoperative course. This includes preoperative work-up of patient comorbidities, especially those that might compromise healing or vasculature. Additionally, the use of CTA to assist in identification of perforators has become an integral step in preoperative planning ( Fig. 4 ). Imaging allows a surgeon to identify major perforators and thus the ability to reduce operating time. Keys and colleagues note that although it can be extremely useful, clinical judgment is ultimately the deciding factor in determining which perforator to isolate and use; therefore, surgeons cannot solely rely on preoperative imaging for perforator selection.
Patient positioning
Patient positioning for tissue expander placement can be successfully performed for the most part with supine positioning and sterile preparation to the lateral flanks bilaterally. Positioning for the flap harvest and inset depends on the location of proposed reconstruction. Supine is sufficient for upper abdominal and anterior proximal lower extremity defects; however, lithotomy may be required for vulvar/perineal defects and frog leg position for the medial proximal lower extremity.
Procedural approach
Expander Placement and Expansion Process
Tissue expander selection is dictated by anatomic site as well as amount of tissue needing to be expanded. Shapes include round, rectangular, and crescent as well as anatomic for breast pocket expansion. Expanders are also available to be customized with regard to final fill volume.
In designing the pre-expanded DIEP, ideally the incision line should be placed within the incision design of the flap and oriented along the long axis of the expander. A transverse skin paddle design accommodates this nicely. A subcutaneous plane is chosen because it has the advantages of precise pocket creation, has a lower risk of seroma, and allows for a faster expansion process postoperatively. It is important to have the expander placed over an area in the abdomen where it can be against a bony structure, such as ribs or the iliac crest. This not only provides more control of the projection of expansion but also decreases patient discomfort. The final position of the expander should be beneath perfusion zones I and II of the flap. Fixation of the expander is important to reduce the risk of migration or rotation of the expander. Ports can be integrated within the expander itself or be connected by customizable length tubing, which is outside of the body. Selection of the port is at the discretion of the surgeon; an incorporated port has the risk of expander compromise if the port is missed during filling, but an exteriorized port has the risk of introducing bacteria via the tubing.
Postoperatively, drains are placed to reduce the risk of seroma formation for the first 5 to 7 days, and prophylactic antibiotics are imperative as long as the drains remain in place. The expansion process does not move forward until the incision site is well healed, which can potentially be within 7 days as long as the skin flaps appear well perfused and healthy. Expansion can occur once per week every 2 to 3 weeks depending on local tissue laxity, patient comfort level, and anticipated final volume. There is a minimum of 4 weeks between final expansion and flap harvest.
Flap Harvest/Inset
Pedicle flaps offer the advantage of no microsurgery, which can theoretically decrease operative time. Surgeons must always remain cognizant of certain crucial details. Once the perforator has been identified and dissected, care must be taken to ensure it does not become twisted or kinked during the inset. Additional perforator length can be obtained to prevent kinking or twisting, with curvilinear pedicle inset. Doppler signal of the selected perforator should occur regularly through the dissection, prior to any mobilization, and after inset. Arterial and venous Doppler signal, capillary refill, and signs of venous congestion should be assessed. The superficial inferior epigastric vein may be harvested and anastomosed when additional venous outflow is needed. It is also imperative to perform a pinch test of the tissue prior to any final circumferential excisions, to ensure adequate tissue laxity for closure. Minimizing the degree of rotation decreases flap complications; flap rotation should ideally be 90° from its native position. Lastly, the lateral one-third of the flap has the highest risk for ischemia and, thus, should be discarded.
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