Source Clinics in Plastic Surgery Volume: 25 Number: 2 April 1998

The Superior Gluteal Artery Preforator Flap

Robert J. Allen, MD, FACS

As breast reconstruction becomes more of an expected rather than merely accepted addition to cancer therapy, the number of options available to the surgeon increases. In the case of autogenous tissue reconstruction, the most common donor site used today is the lower abdomen.!' 4, 6 Occasionally, patients in whom the lower abdomen is not available as a donor site present desiring autogenous tissue reconstruction. Reasons for the unavailability of this tissue vary from thinness and nulliparity to the presence of scars from previous abdominal operations and resulting uncertainty of vessel location. In such cases, an-other choice for the donor site is the gluteal region. Although myocutaneous free flaps using this area have been described, their use has been complicated by the short vascular pedicle that they provide, the problems arising from exposure of the sciatic nerve, and the recipient vessel size discrepancy that has been noted.9 10

Another option that makes use of this do-nor region involves the harvest of free flaps based on dissection of the myocutaneous perforators using microsurgical technique. This allows the use of overlying skin and fat alone, which are ideal for breast reconstruction, and avoids any muscle sacrifice and resultant functional deficits. The authors used the superior gluteal artery perforator (S-GAP) free flap for autogenous breast reconstruction in patients without adequate lower abdominal tissue.2 This flap provides a long pedicle based upon the superior gluteal artery. Ad-vantages of GAP flap reconstruction include:

Avoids exposure and retraction of the sciatic nerve
Ample amount of skin and fat Natural permanent result
Avoids muscle loss
Long vascular pedicle
Easily concealed donor scar Brief hospitalization
No fat necrosis

Indications for GAP flap reconstruction include:

Lower abdomen not suitable
Patient refuses muscle loss
Patient refuses implants
Failure of other methods
Patient preference

Anatomy

The blood supply to the gluteal region has been described in detail. The superior gluteal artery and the inferior gluteal artery, both branches of the internal iliac artery, are the dominant pedicle of the gluteus maximus muscle. The first perforator of the profunda femoris artery and intermuscular branches of the lateral circumflex femoral artery are minor pedicles of this muscle. Twenty to 25 cutaneous perforators, the larger of which originate from the superior and inferior gluteal arteries, supply the skin and fat overlying the muscle. Koshima7 notes that larger perforators vary from 3 cm to 8 cm in length and 1.0 mm to 1.5 mm in diameter. Superior gluteal artery perforators reach the superolateral region of the buttock, whereas the inferior gluteal artery sends perforators to the inferomedial and inferolateral regions. The fourth lumbar artery, the lateral sacral arteries, and the internal pudendal arteries also provide cutaneous perforators to the parasacral area.

The author's own cadaver studies identified multiple perforators in each buttock with at least three main perforators originating from the superior gluteal artery. These perforators averaged 8 cm in length when dissected down to their origins at the superior gluteal vessels. Average superior gluteal artery diameter was 3.5 mm, and its two vena comitantes typically were found to be 2 mm to 4 mm in diameter.

Surgical Technique

Preparation and Preoperative Marking

The patient is placed in the lateral decubitus position, allowing a two-team approach. Pneumatic compression ankle devices are used for deep venous thrombosis prophylaxis. The location of the superior gluteal vessels is marked based on known anatomic landmarks. Specifically, this vessel often can be found one third down a line drawn from the posterior superior iliac spine to the greater trochanter. Once this is done, a Doppler probe is used to identify the vessel's cutaneous perforators, and their positions are marked.l2 With these landmarks in mind, a skin island is drawn over the perforators in an elliptical fashion. With proper planning, the resultant scar can be hidden easily in a swimsuit (Fig. 1A).

Flap Dissection

Once the skin island has been incised through the skin and subcutaneous tissue down to the muscle, dissection is begun from the lateral to the medial aspect using loupe magnification and careful technique. It is

helpful to dissect below the fascia because this allows quicker identification of perforators. When very small perforators are encountered, they should be coagulated with the bipolar. Larger perforators on which the flap will be based should be located in the vicinity of the Doppler-guided preoperative markings. Because selected perforators travel within single muscle fiber planes, complete muscle sparing is possible. As the muscle is divided in the direction of its fibers to facilitate further dissection of the perforators, any small branches of the vessels are ligated or clipped as they are encountered (Fig. 1B). The advantage of this meticulous technique is that it creates an almost bloodless field. Just above the pyriformis muscle, multiple perforating branches of the superior gluteal artery must be identified to avoid ligating the pedicle. Upon reaching the superior gluteal vessels, the dissection is complete, and the pedicle length should measure approximately 8 cm in length, with an arterial diameter of 3 mm to 4 mm. One or two veins accompany the artery; these should be separated before ligation of the flap. Once this has been completed, the flap is removed and weighed (Fig. 2A).

Recipient Vessel Dissection

While the first team harvests the S-GAP flap, the second team prepares the recipient vessels. The internal mammary artery is an excellent recipient vessel, with a diameter of approximately 3 mm.3 Isolation of this vessel starts with identification of the third costar cartilage. This is followed by dissection of the pectoralis major muscle from the sternocostal margin, exposing the third rib cartilage, which is then removed. One artery and one or two veins are found at this level. The larger vein diameter varies from 2 mm to 4 mm and is always adequate. These are dissected for a distance of approximately 3 cm to 4 cm under loupe magnification and prepared for anastomosis. Once dissection is completed, the wound is closed with staples and a clear, occlusive dressing is placed before repositioning the patient.

Donor Site Closure

Before microvascular anastomosis is begun, the donor site is closed. Once homeostasis is ascertained, a drain is placed. If necessary, undermining is performed to facilitate wound closure in two layers. Deep layer closure using 2-0 absorbable is followed by subcuticular skin closure with 3-0 absorbable (Fig. 1C). Once sterile dressing has been applied, the patient is returned to the supine position, and a compression garment is applied.

Figure 1. Skin island location of the S-GAP flap (A). The superior gluteal vessel courses through the divided gluteus maximus muscle (B). Postoperative view (C).

Figure 2. Once freed, the S-GAP flap typically has a lengthy pedicle (A). The S-GAP flap inset with anastomosis between the internal mammary artery and the superior gluteal artery (shaded) (B).

Figure 3. A 34-year-old patient post modified radical mastectomy (A), and 2 years postoperatively after GAP-flap reconstruction (B). Donor site marked preoperatively with patient in lateral decubitus position (C), and donor site at 2 years follow-up (D).

Figure 4. A 55-year-old patient 27 years post augmentation mammoplasty with severe capsular contractures (A). Donor site marked within swimwear line for bilateral autogenous augmentation with S-GAP flaps; Perforators marked using Doppler (B). Calcified capsule with ruptured silicone gel prosthesis (C).

Figure 4 (Continued). One year postoperative follow-up of autogenous augmentation (D), oblique view (E), and donor site with improved contour and buttock lift (F).

Vessel Anastomosis

With the patient in the supine position, the chest wall dressing is removed and prepped with betadine. The flap is transferred to the chest and sutured to the skin for stability during microvascular anastomosis. The above preparations result in an easily tolerable flap ischemia time of approximately 40 minutes. Pharmacologic agents routinely are not needed for control of vessel spasm or anticoagulation. The gluteal perforators usually match quite well with the internal mammary vessels.

Breast Mound Creation

Once the microvascular anastomosis is complete, the patient may be placed in a more suitable position for flap insetting and con-touring. Intraoperative Doppler scanning identifies the locations of the perforators relative to the skin surface. Marking these locations on the skin facilitates postoperative flap monitoring by the nursing staff. The previously elevated pectoral flap is brought down to cover the anastomosis to prevent a palpable defect in the chest wall. The flap is first contoured and then sutured to the pectoral fascia or inframammary fold. One drain is placed under the flap and in the axilla. Next, the skin is closed with a running, subcuticular, absorbable suture (Fig. 2B). A temperature strip is placed centrally on the flap, and a control strip is placed over the sternal skin. A clear, occlusive dressing is applied.

Discussion

The S-GAP flap is an ubiquitous autogenous tissue flap that should be considered if the lower abdomen is not available. The amount of tissue in the superior gluteal region has proven a good match with the amount needed for reconstruction because patients with larger breasts tend to have more

tissue in this area and vice versa. As an added benefit to the patient, the scar is easily concealed by a swimsuit. In the author's series of 70 S-GAP flaps, no flap loss was experienced and reconstruction for a variety of indications was performed (Table 1). On four occasions, bilateral, simultaneous S-GAP flap reconstruction were performed. In addition, 12 staged bilateral breast reconstructions using two S-GAP flaps were done. The inferior gluteal artery perforator (I-GAP) flap was used for six reconstructions. Donor site morbidity has proven minimal. Patients are ambulatory on the first postoperative day and are discharged on the second or third postoperative day.

Skin island size has varied from 8 x 22 cm to 12 x 32 cm. The vast majority of flaps have been elevated based on one perforator, the rest on two. Because the flap provides a long vascular pedicle with vessel diameters compatible with that of the internal mammary vessels, there has been no need for vein grafts. In addition, the use of the internal mammary vessels allows for medial placement of the flap, avoiding excessive lateral fullness. In very thin patients, the costar cartilage defect may be palpable; however, the pectoralis muscle has been used, as described previously, to obliterate this space.

The gluteus muscle is a powerful extensor and lateral rotator of the thigh. It is important for running, climbing, and jumping. Al-though previous studies have reported no loss of function if half of the gluteus muscle remains intact, use of the S-GAP flap avoids the possibility of any functional loss by taking no muscle. Also important is that no major nerves are exposed during the procedure.

Early in the author's series, donor site seroma was a common complication. By using compression garments, the incidence of this unwanted occurrence was greatly decreased. No significant fat necrosis has occurred in any of the flaps. Flap tissue has been adequate in all patients, and there has been no need for implants to provide additional volume.

Table 1. GAP FLAP INDICATIONS IN A SERIES OF 70 PATIENTS
Prescription Post mastectomy Implant replacement Breast augmentation Poland's syndrome Pectu's excavatum	n 47 10 10 2 1

 

Figure 5. An 18-year-old patient with pectus excavatum and right breast hypoplasia (A). Donor site marked within swimwear line (B). Lateral view of hypoplastic breast preoperatively (C), and reconstructed breast postoperatively (D). Oblique view postoperatively of S-GAP flap beneath right breast (E). Normal buttock contour, 7 months postoperatively (F).

Figure 6. A 25-year-old patient with Poland's syndrome has absent left breast tissue and partially absent pectoralis major muscle (A). B. Donor site left buttock. C, Note thickness of buttock fat. Initial flap weight was 467 9. Plaster mold of normal right breast was 350 cc. Final flap weight was 394 9. Three years postoperatively after left S-GAP flap breast reconstruction (D), oblique view (E), and donor site left buttock (F).

Conclusion

As many as 25% of patients do not have adequate lower abdominal tissue available for autogenous breast reconstruction. In such cases, the gluteal artery perforator flap should be considered a reliable and worthy substitute. Figures 3 through 6 present a series of case studies illustrating the use of the S-GAP flap for autogenous breast reconstruction.

Acknowledgement

The author wishes to thank Ksenija Gagic for preparation of the manuscript.

References

1. Allen RJ, Treece P: Deep inferior epigastric perforator flap for breast reconstruction. Ann Plast Surg 32:32, 1994

2. Allen R. Tucker C Jr: Superior gluteal artery perforator free flap for breast reconstruction. Plast Reconstr Surg 95:1207, 1995

3. Dupin CL, Allen RJ, Glass CA, et al: The internal mammary artery and vein as a recipient site for free-flap breast reconstruction: A report of 110 consecutive cases. Plast Reconstr Surg 98:685, 1996

4. Friedman RJ, Argenta LC, Anderson R: Deep inferior epigastric free flap for breast reconstruction after radical mastectomy Plast Reconstr Surg 76:455,1985

5. Fujmo R. Harashina R. Enomoto K: Primary breast reconstruction after a standard radical mastectomy by free flap transfer (case report). Plast Reconstr Surg 58:371, 1976

6. Holstrom H: The free abdominoplasty flap and its use in breast reconstruction. Scand J Plast Reconstr Surg 13:423, 1979

7. Koshima I, Moriguchi T. Soeda S. et al: The gluteal perforator-based flap for repair of sacral pressure sores. Plast Reconstr Surg 91:678, 1993

8. Koshima I, Soeda S: Inferior epigastric artery skin flaps without rectus abdommus muscle. Br J Plast Surg 42:645, 1989

9. Paletta CE, Bostwick J III, Nahai F: The inferior gluteal free flap in breast reconstruction. Plast Reconstr Surg 84:875, 1989

10. Shaw WW: Breast reconstruction by superior gluteal microvascular free flaps without silicone implants. Plast Reconstr Surg 72:490, 1983

11. Strauch B. Yu HL: Atlas of Microvascular Surgery New York: Thieme Medical Publishers, 1993, p 104

12. Taylor GI, Doyle M, McCarten G: The Doppler probe for planning flaps: Anatomical study and clinical applications. Br J Plast Surg 43:1, 1990