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Perforator flaps have revolutionized the field of reconstructive plastic surgery by allowing novel therapeutic options with minimal functional cost to the patient. Despite initial resistance, perforator flaps are now preferentially accepted as the gold standard in autogenous reconstruction in situations where muscle transfer is not necessary. The superior gluteal artery perforator (SGAP) flap constitutes the descendant of the gluteus maximus myocutaneous flap. Although possessing all of its predecessor's advantages, the SGAP flap generates much less donor-site morbidity. Indications for use are multiple, spanning locoregional use as a pedicled flap to free-tissue transfer in breast reconstruction. In this article, we will review the technique of flap harvest with emphasis on some useful tips to achieve an optimal outcome. Typical indications for the flap will be illustrated and specific advantages/disadvantages will be discussed.
It is well accepted that autogenous breast reconstruction can provide the most natural and long-lasting results. Nowadays, the abdomen constitutes the primary donor site because it often harbors an abundant amount of well-vascularized tissue. However, it can sometimes be unavailable, for example, when excessive abdominal scarring is present or in very thin patients. In these cases, the gluteal region offers a valuable alternative source of autogenous tissue.
The microsurgical transfer of a gluteal myocutaneous flap for breast reconstruction was first described by Fujino and colleagues in 1975.1 Despite initial enthusiasm, the use of this flap was plagued by difficult dissection of the donor vessels, a short pedicle, and significant donor-site morbidity. The advent of the perforator flaps in the early 1990s marked a major breakthrough in reconstructive surgery. Koshima et al initially described a pedicled gluteal perforator flap in 1993 but it was based on short parasacral perforating vessels.2 Shortly thereafter, Allen and Tucker reported the use of the superior gluteal artery perforator (SGAP) flap as a free-tissue transfer for breast reconstruction.3 Blondeel further refined the operation in 1999 by demonstrating the use of the SGAP as a sensate flap.4 Around the same time, Verpaele and colleagues published their experience with the pedicled SGAP in the treatment of sacral pressure sores.5 This time, the flap was pedicled on a single perforator of the superior gluteal artery (SGA), allowing for a much greater mobility.
The SGAP flap eventually proved to possess distinct advantages over the older gluteal myocutaneous flaps. Although the SGAP flap can provide top-quality soft tissue reconstruction, donor-site morbidity is minimized by avoiding unnecessary resection of an important locomotion muscle. Further, pedicle length is maximized, resulting in greater flexibility in flap insetting. In fact, the SGAP flap represents the ultimate upgrade of the gluteal myocutaneous flap. It constitutes our second choice for autogenous breast reconstruction after the deep inferior epigastric artery perforator (DIEAP) flap and our preferred choice for sacral coverage in its pedicled version.
In order for the flap harvest to be safer and more time-efficient, it is crucial that the preoperative investigation include a proper study of the gluteal vascular anatomy. This is especially important in cases where alterations in the blood supply to the buttock can be present, for example, after liposuction of the gluteal region. Unidirectional Doppler flowmetry can easily be used to detect and map important musculocutaneous perforators before the operation.6 Usually four or five adequately sized perforators can be found in the territory of the SGA. A large SGAP flap is normally perfectly perfused by harvesting only one good perforator. The Doppler device has the advantages of being ubiquitous, portable, cheap, and straightforward to use by the surgeon. However, it only provides approximate information on perforator location and subjective evaluation of the vessel size. It also tends to generate false-positive and false-negative signals, thereby reducing its reliability.
We recently started using multidetector computed tomography scans in preoperative planning of perforator flaps. This modality has marked advantages over Doppler or duplex imaging. It can provide a highly detailed depiction of the perforating vessels including their intramuscular portion (Fig. 1). Caliber can be assessed as well as the subcutaneous branching patterns. A precise operative plan can thus be devised in consideration of the best perforator and its alternatives, reducing the risk of intraoperative errors and minimizing operating time. Choosing the most remotely located perforator from the SGA pelvic exit point will provide a longer pedicle, which will ease flap insetting and shaping.
The patient is positioned in ventral decubitus. The site where the SGA enters the buttock is identified at the junction of the proximal and middle thirds of a line connecting the posterior superior iliac spine (PSIS) to the apex of the greater trochanter of the femur (Fig. 2A). A line is then drawn between the PSIS and the coccyx. The position of the piriformis is located by joining the middle of the PSIS-coccyx line to the superior edge of the greater trochanter. As the SGA supplies the suprapiriform portion of the gluteus maximus, perforators located cranial to the piriformis and lateral to the SGA exit point will be considered. The position of the relevant perforators is identified and marked on the skin (Fig. 2B).
Next, the flap design is drawn (Fig. 2C). It should be centered over the selected perforator as much as possible. Although the skin island can be oriented in any way, for breast reconstruction we use a fusiform shape oriented parallel to the bikini line. The incision ends medially with a fishtail design to avoid dog-ear formation. The oblique orientation of the flap results in a well-concealed scar and minimizes deformity upon donor-site closure. Flap dimensions can be up to 30 cm in length and 13 cm in width. If a large volume of tissue is needed, the flap is preferentially extended medially to avoid lateral contour deformities.
Positioning of the patient is either in lateral or ventral decubitus, depending on the indication for surgery. The flap harvest should be done under loupe magnification, proceeding with patience and with the utmost care. A dilute epinephrine-containing local anesthetic is injected along the incision line. The skin ellipse is first incised laterally. The subcutaneous fat is dissected carefully with the needle electrocautery, taking care to bevel mostly on the caudal side of the flap as this will ensure an even closure while recruiting extra tissue volume. After the superficial fascia has been opened at the cranial edge of the flap, the nervi clunii superiores can be identified in the fat above the muscle fascia. In the case of a free SGAP, if these nerves are of adequate size for microanastomosis, they can be dissected and included to obtain a sensate SGAP flap.4 They can later be anastomosed to the anterior ramus of the lateral branch of the fourth intercostal nerve to restore sensation to the reconstructed breast.
The gluteus maximus fascia is then opened. At this point, the patient should be completely paralyzed to avoid any jerking movements during the dissection of the perforator, which could potentially result in avulsion damage to the vessel. Perfect hemostasis is mandatory to prevent staining the areolar tissue and obscuring the planes of dissection. The dissection proceeds from lateral to medial at the subfascial level. The multiple perimysial septations between the muscle fibers are sequentially divided while looking for the chosen perforator. These intramuscular septae are attached to the muscle fascia and carry the perforating vessels (Fig. 3).
Once the selected perforator has been identified, it should be observed for pulsatility and for the presence of an adequately sized vein (more than 1 mm). Next, the muscle is split longitudinally between its fibers, revealing the more proximal part of the perforator running in the septum (Fig. 4). It has to be emphasized that wide exposure is key in understanding three-dimensional anatomy of the perforator and its side branches. The surgeon should not hesitate to open the muscle along the septum over a significant distance. The dissection will be much simplified and the risk of technical error will be minimized. The perforator is freed by a combination of blunt and sharp dissection. Side branches to the muscle are ligated and cut one after the other. The perforator should be frequently irrigated to prevent desiccation. Likewise, overzealous traction on the flap should be avoided to preclude noxious intimal tears.
When the deepest portion of the gluteus maximus is reached, the anterior fascia of the muscle is encountered. In the case of a pedicled SGAP, the dissection can stop here if sufficient flap mobility is obtained. After the thick fibrous sheath is opened, the subgluteal fat pad is exposed, thus unveiling an intricate vascular network (Fig. 5). Multiple important side branches lay in a stellar configuration, and it may not always be easy to determine where the origin of the pedicle is located. Again, broader exposure will help to decipher the situation by understanding the three-dimensional relationships. Veins in the subgluteal fat pad tend to be fragile and may lead to important hemorrhage that can be difficult to control. Therefore, dissection should proceed very carefully in this area. If the pedicle length achieved by the intramuscular portion alone is sufficient, dissection in the subgluteal plane can be avoided. However, in breast reconstruction it is often advisable to obtain a longer pedicle so as to have more freedom in flap insetting. Two to 3 cm can be gained by following the pedicle in the subgluteal space. Typical SGAP pedicle length varies between 6 and 10.5 cm. Diameter of the artery is 2.0 to 3.0 mm and the vein is 2.5 to 4.5 mm.
After pedicle dissection, the rest of the flap is detached from the gluteus muscle. At this point, it can be done in the suprafascial plane to minimize seroma formation. Next, the pedicle is sectioned and the donor site closed. To reduce tension on closure, the lower skin flap is undermined and the hip is extended. Undermining over the iliac crest and trochanter is avoided because this will interrupt important periosteum-to-skin ligaments. Suction drains are inserted then the superficial fascia and the dermis are closed with separate sutures of resorbable material. The skin is sealed with Dermabond® (Ethicon Inc., Somerville, NJ).
The SGAP flap constitutes a valuable second choice for autologous breast reconstruction after the DIEAP flap.3,4,7,8,9,10 It is indicated for total or partial breast reconstruction in cases where the abdominal donor site is unavailable (Fig. 6). Contraindications to harvesting a DIEAP flap include patients who had a previous abdominoplasty, asthenic individuals with insufficient abdominal volume, or patients presenting excessive abdominal scarring. The SGAP flap has also been used for autogenous breast augmentation as an alternative to implants.11
During unilateral breast reconstruction with the SGAP flap, one intraoperative position change is necessary. The patient is first placed in the lateral decubitus position and the ipsilateral upper extremity is freely draped. The breast is reconstructed using the ipsilateral buttock to allow simultaneous flap harvest and recipient site preparation. Once the flap is harvested, it is transferred to the chest wall and microanastomosis takes place with the patient still in lateral decubitus. The donor site is closed simultaneously. After completion of the microanastomoses, the recipient site is protected with an occlusive dressing and the patient is placed in supine position, prepped, and draped again. The flap is inset and symmetry is verified by placing the patient in a sitting position. Bilateral breast reconstruction with double SGAP flap is feasible but it entails two position changes and is a fairly lengthy procedure.12,13,14
The internal mammary artery and vein constitute our preferred recipient vessels. They allow medial placement of the flap and avoidance of vascular grafts. The level of the third rib is favored so as to obtain better-caliber vessels and avoid multiple smaller venous branches, often seen at the level of the fourth rib. Occasionally, large perforators from the internal mammary vessels are present at the second or third intercostal space and can be used as recipient vessels.15 This obviates the need for cartilage resection and thus, morbidity is further decreased. Although the internal mammary artery and the SGA are of comparable caliber, the superior gluteal veins can often be somewhat larger than the recipient veins. Therefore, the microanastomotic technique sometimes needs to be adapted to account for venous size mismatch.
After the flap is reperfused, shaping is the next important step. Different flap positions can be tried to select the one giving the best aesthetic result. The pedicle should be checked to make sure it is not twisted or kinked. The area of skin to be kept is determined and the rest of the flap is de-epithelialized. If a volume resection is necessary, it should be done from the deep aspect of the flap to preserve perfusion through the subdermal plexus. The flap is usually suspended like a hammock by attaching it to the pectoral fascia in the superolateral quadrant. It is also important to obtain a good definition of the inframammary fold and the anterior axillary line. Sutures can be placed between the dermis of the flap and the chest wall to recreate those important landmarks.
The SGAP flap constitutes an excellent tool for coverage of locoregional defects.2,5,9,16,17,18 It is particularly suited for reconstruction of large midline sacral wounds. The SGAP flap is an especially appealing option for nonplegic patients because the gluteus maximus muscle is spared. Even in paralyzed patients, the preservation of an intact gluteus maximus makes it possible to use it later as a muscle flap, should a recurrence occur.
When the SGAP flap is used for coverage of a sacral defect, the upper incision can be designed similarly to an imaginary rotation flap.5 The dissection should proceed caudally from that line, under the muscle fascia, in search of an appropriate perforator. If a dissection error is made or no adequate perforator is found, the operation can be converted into a fasciocutaneous rotation flap to allow closure of the sacral defect. This approach adds an additional safety factor and makes the pedicled SGAP flap a good learning model for surgeons who have limited experience with perforator flap dissection.
Once a suitable perforator has been identified, intramuscular dissection proceeds as previously described. The inferior incision is made and the flap is completely islanded on one perforator (Fig. 7). By widely splitting the muscle along the septum where the perforator is located, impressive flap mobility can be achieved. In pressure sore treatment, this allows transfer of healthy tissue located away from the chronically inflamed wound. The donor site is closed primarily.
Wounds of the lumbar area can also be elegantly treated by the pedicled SGAP.16,17 By extending the flap design laterally and splitting the gluteus maximus muscle cranially, the flap can provide coverage up to T12–L1. The pedicled SGAP flap can also reach the trochanteric and ischial areas,18 although other surgical options may be preferable for those regions.19,20
At the beginning of the 1990s, the popularization and wide acceptance of laparoscopy completely changed the way general surgery was practiced. Formerly an invasive operation, cholecystectomy eventually became a same-day procedure because the avoidance of muscle transection led to a quicker rehabilitation for the patient. Similarly, the development of perforator flaps over the last decade is resulting in a major breakthrough in plastic surgery. Instead of sacrificing an irreplaceable muscle, it is now possible to offer patients high-quality autogenous soft tissue reconstruction with negligible impact on donor-site muscle function. Muscle preservation is probably best exemplified by the first and best known perforator flap, the DIEAP flap. A prospective study comparing DIEAP and transverse rectus abdominis myocutaneous (TRAM) flaps clearly demonstrated that saving the rectus abdominis muscle during flap harvest reduced the donor-site morbidity to an absolute minimum.21 However, to achieve preservation of a functional muscle, adequate anatomical knowledge and meticulous surgical technique is needed to ensure protection of both motor innervation and collateral blood supply to the muscle.
Although a similar study on donor-site morbidity has not been done for the gluteal donor site, it appears logical that more muscle function will be preserved if the muscle is left intact. We feel strongly that the gluteus maximus should be spared, given the fact that it is an important and nonexpendable locomotion muscle. This argument is even more justified in younger women presenting for breast reconstruction. Because the abdominal area may not necessarily be sufficient in those patients, the gluteal region constitutes an excellent second choice as it harbors a constant volume of adipocutaneous tissue. Selecting the SGAP flap ensures that those younger patients can return as quickly as possible to their active lifestyle.
When compared with the gluteus maximus myocutaneous flap, the SGAP flap has similar intrinsic qualities. It is autogenous tissue and it can achieve highly aesthetic and long-standing results in breast reconstruction. The gluteal fat has a firm consistency due to a developed reticular system, and it is easier to obtain breast projection than with the more flaccid abdominal flaps. Even if it is based only on one musculocutaneous perforator, the SGAP flap displays vigorous blood supply, and the size of the flap is limited only by the ability to close the donor site. The possibility of a sensate flap is a bonus that can be exploited in selected cases.
Furthermore, the SGAP flap has several advantages over its myocutaneous counterpart. The intramuscular dissection results in a longer pedicle, which obviates the need for vein grafts in breast reconstruction. The absence of muscle in the flap allows for more flexibility in how the flap is inset and shaped. Flap harvesting itself is rendered easier by improved visualization of subgluteal neurovascular structures through wide muscle splitting. Because the muscle is not resected, bony prominences and important nerves will not become exposed. The absence of muscle harvest leads to less postoperative pain, a shorter hospital stay, and therefore reduced costs. Donor-site closure results in a well-concealed scar and minimal distortion of the buttock.
Perforator flaps have been criticized for having a steep learning curve. Although it is true that it can initially take the novice surgeon a longer time to perform a perforator flap than a myocutaneous flap, this difference will vanish as experience grows. Perforator flap dissection is more about good judgment and patience than about special skills. All plastic surgeons with microsurgical training possess the basic abilities for harvesting a perforator flap. Basic surgical principles of wide exposure, bloodless dissection, and delicate tissue handling should be applied at all times.
Concerning microsurgical reconstruction of total breast defects, the DIEAP flap has been favored by the senior author for over 12 years now.22 A few reasons explain why the SGAP flap comes in as a good second choice, after the DIEAP flap. The lower abdomen is the anatomical region that can provide the greatest amount of skin and fat in the body, especially in parous females. A bilateral breast reconstruction can be performed comfortably using the lower abdomen, whereas the SGAP flap can provide just enough tissue for one breast. If a large area of skin is needed for the reconstruction, the surgeon should make sure that it can be harvested from the buttock while still allowing primary closure. Another option would be to use preoperative skin expansion to reduce the quantity of skin needed during the eventual SGAP flap reconstruction.23 One more drawback of the SGAP flap is that it has a shorter vascular pedicle than the DIEAP flap. This can translate into less flexibility with flap insetting. As stated earlier, the gluteal fat has a firm texture, which can make breast shaping more difficult. A secondary revision procedure is frequently required to obtain the desired final shape. If asymmetry of the donor site is present, a contralateral buttock lift is occasionally desirable. Another advantage of the DIEAP over the SGAP flap is that the flap harvesting, microsurgical anastomosis, and breast shaping can all be done in one position, thus keeping operative time to a minimum. Finally, the SGAP flap requires a technically more demanding dissection, especially in the subgluteal fat pad, a “no-man's-land” that often needs to be penetrated to gain extra length on the pedicle.
The present period in medicine is marked by a tendency toward procedures with high therapeutic efficacy but with reduced “collateral damage.” In this era of minimally invasive procedures, perforator flaps take their own position and provide new solutions for complex wounds with the least possible donor-site morbidity. The SGAP flap is a useful and versatile adjunct to the contemporary surgeon's armamentarium both as a free flap and a pedicled flap.