Breast Reconstruction with the Superior Gluteal Artery Perforator (S-GAP) Flap

Aldo Guerra, M.D.,1
Robert J. Allen, M.D., F.A.C.S.,1 and
Charles L. Dupin, M.D.1

ABSTRACT
Breast reconstruction with autogenous tissue has become increasingly popular during the past several decades. Reconstruction has been successful using many donor sites, but the abdomen remains the overwhelming choice. However, it is estimated that, in 15 to 20% of patients who undergo mastectomy, the abdomen is not suitable as a donor site. The back, buttocks, and thighs can serve as alternative donor sites in those cases. Our group previously described the superior gluteal artery perforator (S-GAP) flap for breast reconstruction.1 Since 1993, this flap has been used at our institution as a first-line alternative in patients where the abdomen is judged to be inadequate as a donor site.

Based on our success with the deep inferior epigastric perforator artery2 flap, harvesting only fat and skin from the abdomen, we became interested in applying perforator techniques to the gluteal region. Dissection of the vascular structures out of the muscle proved to be advantageous by providing a much longer pedicle and a much easier dissection of the parent vessels when compared with the gluteal myocutaneous flap.3 In this article we present our 8-year experience with 127 S-GAP flaps. Flap survival was 98%, with an overall complication rate of 17%. Patient satisfaction of the reconstructed breast and donor site has been excellent. Although the technique is not an easy one to learn, it does provide a reliable flap and an excellent esthetic reconstruction.

When the abdomen is not available, the authors feel strongly that the S-GAP flap should be used as an alternative site before considering other options for breast reconstruction.

KEYWORDS
Superior gluteal artery perforator flap, deep inferior epigastric perforator artery flap, gluteal flap

Patients presenting for autogenous breast reconstruction are attracted to these techniques for a number of reasons. They prefer the permanence of results, the ability to match the opposite breast in both feel and look, and the avoidance of alloplastic materials.Many patients will have a history of radiation to the chest wall, making implant reconstruction more difficult and likely to result in failure.4

The goal of the reconstructive surgeon is to provide the most esthetic result with the least amount of morbidity and functional loss at the donor site. Autologous tissue reconstruction allows the creation of a soft, symmetrical, and esthetically pleasing breast mound. The donor site receives a significant insult and may be predisposed to considerable postoperative morbidity. This is particularly true when using the abdomen as a donor site. Patients undergoing reconstruction with myocutaneous flaps from this area may be affected by postoperative hernias or weakness in the abdominal muscles. The highest risk occurs in patients who donate both rectus abdominus muscles for their reconstruction. 5 Techniques that preserve the underlying muscle units allow for better functional results and less risk of herniation. The recovery from a perforator flap is associated with less discomfort, a speedy return to work, and an earlier hospital discharge. 6 In the gluteal region the donor site complications differ from those of the abdomen.

However, the principles of perforator-based surgery remain unchanged, and preservation of the gluteus maximus muscle allows the patient to recover with less pain and discomfort. The muscle is split, therefore preserving its innervation. This muscle serves an integral function in ambulation, and most patients are walking on postoperative day 1 and can be discharged home by postoperative day 4.6 A much longer pedicle is obtained by freeing the intramuscular segment of the perforator. Performing the microsurgical anastomosis with a pedicle of adequate length avoids the need for vein grafts and is the major advantage over the gluteal myocutaneous flap. The insetting and shaping of the breast are also improved as the longer pedicle gives the surgeon freedom to manipulate the flap into a more esthetic shape.

Other problems seen with flaps from the gluteal area (superior3 and inferior7 gluteal myocutaneous flaps) such as sciatica are largely avoided. The superior dissection allows the surgeon to avoid exposing the sciatic nerve. The limited muscle dissection allows for more reliable coverage of the underlying structures so that chronic pain syndromes are avoided. The contour in the area is also improved by leaving the entire muscle unit in the donor site. None of our patients have requested donor site augmentation or reported any long-term discomfort. The superior scar is also more easily concealed under the bathing suit. The incidence of seroma has decreased significantly after the routine use of large suction drains and compression garments.

PATIENTS AND METHODS
All patients who underwent breast reconstruction with the superior gluteal artery perforator (S-GAP) flap between 1993 and 2001 were included in this study. A total of 127 patient charts were reviewed. The goal was to analyze the series for operative time, length of stay, weight of flap, size of flap, blood loss, blood transfusion requirement, return to the operating suite, fat necrosis, and overall flap survival. There was no patient mortality in this series. The reasons for choosing the gluteal site were given.

PATIENT SELECTION
The reasons for selecting the gluteal flap versus the abdominal donor site are listed in Table 1.

The most common reason was a patient with a thin, nulliparous abdomen. These women tend to be tall and thin with an average body mass index of 21 for this series (Fig. 1). The most common indication for surgery was postmastectomy reconstruction (Table 1). The average age of patients undergoing S-GAP flap reconstruction in this series was 46, range 32 to 60. Twenty-seven percent of the patients received radiation therapy before undergoing S-GAP flap reconstruction. Only 10% of the patients gave a history of cigarette smoking at the time of surgery.

ANATOMY
All truncal skin and fat is supplied from axial vessels, the vast majority of which emerge from below the muscles, transit through the muscles (myocutaneous perforators), or between them (septocutaneous perforators) to perfuse the overlying skin. In some cases, the perforator vessels travel directly to the skin. These perforating vessels irrigate the fat and skin in myocutaneous and septocutaneous flaps and can be separated from the underlying muscle and fascia. This is the basis of perforator flaps, which allow maximal preservation of the donor muscle and other underlying structures while creating a reliable skin–fat flap. Both the superior and inferior gluteal arteries are terminal branches of the internal iliac artery. They pass out of the pelvis above and below the piriformis muscle, supplying the upper and lower halves of the muscle, respectively.

As the superior gluteal artery passes the greater sciatic foramen it divides into a superficial and a deep branch. The deep branch travels in between the gluteus medius muscle and the iliac bone. The superficial branch goes onto supply the gluteus muscle and the overlying skin territory. It is this superficial branch that is the basis for the S-GAP flap. One usually finds three perforators arising from this vessel with a pedicle length between 3 and 8 cm.8

FLAP DESIGN
Markings are placed on the patient in the operative position. The posterior superior iliac spine is palpated and marked, as is the greater trochanter. A line is drawn connecting these two points. The artery emerges from the edge of the sacrum about one-third the distance from the posterior iliac
spine along the previously marked line (Fig. 2). Perforators may be identified along this point with a Doppler ultrasound probe. The orientation of the flap can vary from angled down along the line or perpendicular to the line. A flap designed as in Figure 2 produces a more favorable scar. As long as a perforator is within the flap, the actual skin orientation becomes irrelevant. The average width of the flap has been 10 cm, but up to 12 cm may be closed in this area without undue tension. The length of the flap is usually between 24 and 26 cm (Table 2).

TECHNIQUE
The S-GAP flap can be harvested with the patient either in the lateral decubitus or prone position. The lateral decubitus position is preferred because it allows a two-team approach. With immediate reconstruction the mastectomy can be done followed by recipient vessel preparation while flap dissection is progressing. Flap dissection is usually begun laterally. Here the flap may not be over the gluteus maximus muscle at all but rather over the tensor fascia lata, so dissection can proceed rapidly.When the fascicles of the gluteus muscle are encountered, dissection proceeds more carefully, incising the perimesyum as it inserts into the fascia overlying the muscle.

Perforators with a clearly definable artery measuring 1 mm and accompanied by two venae commitante are followed through the fascia (Fig. 3). Occasionally, a second large perforator can be found as the dissection on the fascia proceeds medially. It can also be included if it easily joins the first perforator. Regardless, the flap will survive nicely with a single adequate perforator. The dissection proceeds toward the sacral fascia. Once the fascia is encountered, it must be opened to reveal the fatty subfascial recess, which contains multiple communicating veins and arterial muscle branches. Here dissection becomes tedious in an effort to ligate multiple branches carefully.
The dissection is continued until the superior gluteal artery and vein are reached (Fig. 4). The pedicle length at this time is usually between 8 and 10 cm (Table 2). Once an adequate cuff of pedicle has been dissected, the flap can be harvested. The assistant carefully supports the flap while dissection proceeds. The insertion of the pedicle into the flap is delicate and care in handling is a must so as not to shear this vessel. Once the flap is passed off the field the wound is closed in multiple layers.

A large suction drain is left in the defect to prevent postoperative seroma. This is supplemented with a surgical girdle, which is worn for 2 to 3 weeks. At this point, the patient is repositioned supine and the previously dissected recipient vessels are exposed. The microvascular anastomosis is done in the usual fashion, often using the coupler device for the venous anastomosis. We prefer the internal mammary vessels as the recipient vessels of choice for our reconstructions.9 The vessel match at this level is very good, and the increase in pedicle length allows plenty of room to perform a comfortable anastomosis as well as increased flexibility in shaping the breast flap.

RESULTS
Overall flap survival was 98%. Two flaps were lost during the 8-year period this clinical series comprises. One flap was avulsed during surgery, irreversibly damaging the vascular pedicle. This led to the use of the opposite gluteal region during the same procedure for a second S-GAP flap that did survive. A second flap was lost due to thrombosis at the arterial anastomosis after the patient was discharged home on postoperative day 3. There were seven vascular complications (Table 3). Five of seven flaps went on to survive. Other reasons to return to the operating room included breast hematoma evacuation5 and one donor site hematoma evacuation. The average blood loss was 300 ml. Thirty-six percent of patients received autologous blood transfusion during their hospitalization, with only one patient receiving banked blood during our entire series.

The overall takeback rate for the series was 6%, with an overall complication rate at 17%. A single perforator vessel irrigated the flap in over 90% of cases. The S-GAP flap has a robust blood supply and no watershed regions that are predisposed to ischemia, unlike the more common abdominal flaps. Only two patients experienced partial tissue necrosis, which required debride- ment. Both patients had received radiation therapy and were smokers but eventually healed their wounds with conservative management. Patient satisfaction of the newly reconstructed breast and donor site has been excellent. In conclusion, the gluteal region offers a reliable flap, which can be used to create an esthetic breast (Figs. 5–13). This region can an average of 450 g of fat and skin, even in thin patients. It is a ubiquitous donor site, which, with the use of perforator- based techniques to harvest the flap, is only minimally altered (Figs. 7, 13).

REFERENCES
1. Allen R, Tucker C Jr. Superior gluteal artery perforator free flap for breast reconstruction. Plast Reconstr Surg 1995; 95:1207–1211
2. Allen RJ, Treece P. Deep inferior epigastric perforator flap for breast reconstruction. Ann Plast Surg 1994;32:32–38
3. Shaw WW. Breast reconstruction by superior gluteal microvascular free flaps without silicone implants. Plast Reconstr Surg 1983;72:490–501
4. Spear SL, Onyewu C. Staged breast reconstruction with saline- filled implants in the irradiated breast: recent trends and therapeutic implications. Plast Reconstr Surg 2000; 105:930–942
5. Mizgala CL, Hartrmapf CR Jr, Bennett GK. Assessment of the abdominal wall after pedicled TRAM flap surgery: 5 to 7 year follow-up of 150 consecutive patients. Plast Reconstr Surg 1994;93:988–1004
6. Kaplan JL, Allen RJ. Cost-based comparison between perforator flaps and TRAM flaps for breast reconstruction. Plast Reconstr Surg 2000;105:943–955
7. Paletta CE, Bostwick J III,Nahai F. The inferior gluteal free flap in breast reconstruction. Plast Reconstr Surg 1989; 84:875–883
8. Koshima I, Moriguchi T, Soeda S, et al. The gluteal perforator- based flap for repair of sacral pressure sores. Plast Reconstr Surg 1993;91:678–683
9. Dupin CL, Allen RJ, Glass CA. The internal mammary artery and vein as a recipient site for free-flap breast reconstruction: a report of 110 consecutive cases. Plast Reconstr Surg 1996;98:685–691

References