Microsurgical techniques were first used to build a breast mound in 1975, when a group in Japan used a gluteus maximus myocutaneous flap to create a new breast in a patient with Poland syndrome (1). The following year, the same team reported using a gluteus maximus myocutaneous flap to perform the first postmastectomy microsurgical breast reconstruction (2). The gluteus maximus myocutaneous free flap went on to undergo multiple modifications in its use for breast reconstruction (3,4,5,6,7). At the same time, however, the abdomen became a popular donor site for breast reconstruction since it provided the surgeon with tissue that was easier and more convenient to use (8,9,10). When compared to the abdomen, however, the buttock had multiple disadvantages as a donor site: The vascular pedicle was short, the donor-site defect was deforming, and a long operative time was needed to reposition the patient for harvest and inset.

In the mid-1990s, the superior gluteal artery perforator (SGAP) flap was developed (11,12). The SGAP flap was significant because it preserved the gluteus maximus muscle at the donor site while leaving a longer vascular pedicle with the flap. The technique made the microsurgical anastomosis and flap inset much more straightforward. The advances seen in the SGAP flap led to the development of the inferior gluteal artery perforator (IGAP) flap (13,14). Although the SGAP flap was more commonly performed than the IGAP flap, the upper buttock donor site was occasionally noted to have a “scooped-out” appearance. This led to the development of the in-the-crease IGAP flap, which is an excellent option for women who have a “saddlebag deformity.” By borrowing excess skin and fat from the inferior buttock, there is an improvement in buttock shape. Furthermore, the scar is almost completely hidden in the crease (12,15,16). For women requiring bilateral breast reconstruction, both the SGAP and the IGAP can be performed as a bilateral simultaneous operation, which shortens operative time (17).

With the establishment of the SGAP and the IGAP flaps, the buttock became a much more viable donor site for microvascular breast reconstruction. Even so, until recently the GAP flap has been our second choice of donor site, reserved for patients who are not candidates for the use of abdominal tissue. For women with prominent saddlebags, however, we have come to realize that the best aesthetic results may come from harvesting skin and fat from the inferior buttock. The scar ends up almost imperceptibly hidden within the buttock crease, and the patient ends up with a tighter, lifted buttock. Furthermore, the scar does not migrate inferiorly over time, as sometimes occurred with cosmetic buttock lift procedures. Thus, we now choose the IGAP flap as a first choice in selected cases.

The in-the-crease IGAP is harvested using the same microsurgical, muscle-sparing techniques as the deep inferior epigastric artery perforator, superficial inferior epigastric artery, and SGAP flaps. The advantage is that there is almost always adequate volume to make an appropriate-sized breast, the donor site is often improved by the operation, and the scar is completely concealed within the inferior buttock crease. Older operations that used the lower buttock took both fat and muscle. Despite the excellent cosmetic results, this operation was abandoned because of occasional problems with the sciatic nerve in the back of the leg. By taking only the skin and fat and leaving the muscle undisturbed, injury or exposure of the nerves is not a problem. The nerves run underneath the muscle and are completely protected by it. Excess tissue is taken from the lower buttock to create a new breast. Ample tissue is always left for comfort when sitting. Patients report few problems with sitting postoperatively. In fact many of the IGAP patients have remarkably little or no pain.

Any woman who has undergone mastectomy and wishes to be reconstructed with autologous tissue is a potential candidate for the IGAP flap. The ideal candidate is someone with a large buttock (“pear-shaped” body type) and a B size breast. In the right candidate, the in-the-crease IGAP can give an excellent breast reconstruction with a minimally noticeable donor site. In addition, women who cannot use their abdomen as a donor site either due to previous abdominoplasty or liposuction or who have more excess tissue in the buttock area than in the abdomen are also good candidates. The buttock has a high fat-to-skin ratio, whereas the abdomen has a high skin-to-fat ratio. Thus, patients who require mostly fat and little skin may also be good candidates for IGAP flaps. A significant amount of tissue may be harvested, and the average final inset weights of the IGAP flaps may be slightly greater than weights of the mastectomy specimens.

Contraindications specific to IGAP flap breast reconstruction include previous liposuction at the donor site or active smoking within 1 month prior to surgery. Liposuction of the buttock is rare, but liposuction of the saddlebag area can affect IGAP flap viability.

The inferior gluteal artery is a terminal branch of the anterior division of the internal iliac artery and exits the pelvis through
the greater sciatic foramen. Landmarks can also be used to identify the location of the emergence of the inferior gluteal artery outside the pelvis. A line is drawn from the posterior superior iliac spine to the outer part of the ischial tuberosity; the junction of its lower third with its middle third marks the point of emergence of the inferior gluteal and its surrounding vessels from the lower part of the greater sciatic foramen. The artery accompanies the greater sciatic nerve, internal pudendal vessels, and the posterior femoral cutaneous nerve. In this subfascial recess, the inferior gluteal vein will receive tributaries from other pelvic veins. The inferior gluteal vasculature continues toward the surface by perforating the sacral fascia. It exits the pelvis caudal to the piriformis muscle. Once under the inferior portion of the gluteus maximus, perforating vessels are seen branching out through the substance of the muscle to feed the overlying skin and fat. The course of the inferior gluteal artery perforating vessels is more oblique through the substance of the gluteus maximus muscle than the course of the superior gluteal artery perforators, which tend to travel more directly to the superficial tissue up through the muscle. The length of the inferior gluteal artery perforator and the resultant pedicle length for the IGAP flap is 7 to 10 cm (Fig. 67.1).