**Region:** Groin and Gluteal # Inferior Gluteal Artery (IGAP) Flap ## Anatomy - Pedicle: inferior gluteal artery (branch of the anterior division of the internal iliac artery) with accompanying vein. At origin the artery caliber is around 2 mm and the vein around 3.5 mm. The pedicle length is typically 7–10 cm. The artery descends via the greater sciatic foramen, often in close relation to the sciatic nerve, and gives perforators to the lower buttock that penetrate the gluteus maximus to supply overlying fat and skin (sources: IGAP chapter; Blondeel). - Course: the IGA exits the pelvis below the piriformis and descends superficial to the piriformis and gluteus maximus, then continues into the posterior thigh. Perforators arise in the lower half of the gluteus maximus and may continue into the posterior thigh. - Perforator pattern: typically between two and four perforators from the inferior gluteal artery are located in the lower half of the gluteus maximus. Perforators closer to the medial buttock have short intramuscular courses; laterally placed perforators travel obliquely through the muscle and give longer pedicle lengths. Inclusion of two perforators is often advised to improve venous drainage and reduce congestion risk. - Venae comitantes and superficial/descending veins: the inferior gluteal venous anatomy continues with the pedicle and into posterior thigh venous channels. (Numerical diameters and pedicle length above.) - Nerves: the posterior femoral cutaneous nerve courses near and can accompany the IGA into the thigh; it provides sensory innervation to the posterior thigh and perineum. The sciatic nerve lies deep and inferior to the pedicle and must be protected; the posterior femoral cutaneous nerve is at risk at the inferior margin of the flap. - Included tissues: skin, subcutaneous fat and fascia (gluteus maximus fascia). The flap is harvested as a perforator flap preserving the gluteus maximus muscle (muscle spared by spreading fibers rather than dividing). Typical flap length parallels the gluteal fold and is commonly about 18 cm; other sources report IGAP flap length ranges up to 20–26 cm with typical width values around 7 cm (Blondeel). Mean flap weight reported ~400 g (range ~200–600 g). The IGAP flap is firmer/denser than lower abdominal tissue and thus may be less pliable for breast shaping. - Arc of rotation / reach: as a free flap used for breast reconstruction, the IGAP pedicle length (7–10 cm) generally provides sufficient reach to chest recipient vessels after patient repositioning; pedicle length and perforator selection determine inset options for pedicled transfers (perineal, posterior thigh). - Common variants/anomalies: occasional looping or proximity of the posterior femoral cutaneous nerve around the artery; rare significant anatomic variants of the IGA trajectory (Blondeel). Perforator number and location are variable — preoperative imaging aids selection. ## Dissection Steps 1. Positioning, markings, landmarks. - Preoperative markings done with patient standing. Mark gluteal fold and design flap with inferior limit 1 cm inferior and parallel to the gluteal fold; superior limit approximately 7 cm cephalad to the inferior limit. The flap length typically parallels the gluteal fold and is commonly approximately 18 cm (IGAP chapter, Fig. 31.2). - Identify posterior superior iliac spine (PSIS), ischial tuberosity and palpate/visualize buttock bulk. Mark adipose to be beveled at cephalad and caudal aspects to recruit extra soft tissue. - Use preoperative CTA or MRA to map perforators when available; confirm perforator locations with hand-held Doppler with patient in the surgical position. - Positioning: lateral decubitus for unilateral breast reconstruction (flexible; some teams use lateral to avoid multiple repositioning), supine required for initial mastectomy/recipient vessel preparation and again for microvascular anastomosis and inset after harvest; prone or lateral/semilateral may be used for bilateral harvests (IGAP chapter). 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Incise skin and carry incision through subcutaneous fat; bevel outward at cephalad and caudal aspects to recruit bulk and allow the flap to include tissue down to the gluteus maximus fascia. - Elevate flap in a subfascial plane from lateral to medial in a perpendicular direction to the fascial septa arising from muscle fibers (this preserves perforators within septa). Early dissection identifies perforators where they emerge from the muscle. - Identify perforators with Doppler and visually at the deep surface. Prefer to incorporate two perforators when feasible (improves venous drainage). For smaller or single dominant perforator cases, careful intramuscular dissection and pedicle tracing are required. 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - After identification of adequate perforator(s), spread muscle fibers along their orientation and dissect the perforator(s) back through the gluteus maximus toward the inferior gluteal artery until adequate vessel diameter and pedicle length are obtained (typically seeking artery ~2.0–2.5 mm and vein ~3.0–4.0 mm when possible for chest anastomosis). - Take care with deep dissection: the pedicle lies in close relation to the sciatic nerve (usually not exposed) and posterior femoral cutaneous nerve — avoid pressure or traction on nerve structures. Preserve side-branches as needed until final control to avoid inadvertent premature ligation. - Once pedicle length and vessel caliber are adequate, ligate and divide pedicle at appropriate level for free transfer. For pedicled uses, preserve required continuity and mobilize flap into defect ensuring no kinking/twisting of pedicle. - Transfer/inset: for free breast reconstruction, transfer the flap to chest; microsurgical anastomosis to chosen recipient vessels is performed after repositioning to supine. For pedicled reconstructions (perineal/posterior thigh), rotate/advance flap into defect ensuring pedicle is untwisted and not kinked. - Perfusion checks: intraoperative clinical assessment of flap color, capillary refill and bleeding from flap edges is used; the texts do not prescribe a specific monitoring device or numerical perfusion thresholds. 4. Donor-site closure techniques. - Undermine skin and subcutaneous tissues suprafascially both superiorly and inferiorly to allow layered approximation and minimize contour deformity. - Close in layers over closed-suction drains; approximate fascia and muscle with interrupted/figure-of-eight absorbable sutures, then superficial fascia and skin with deep dermal and skin sutures. - Hide scar within gluteal crease; avoid transgressing into medial ischial fat pad (can produce sitting discomfort). If tension-free primary closure is not possible, plan for skin grafting. - Protect donor site from early postoperative pressure (many centers institute a sitting-avoidance protocol during initial healing to reduce dehiscence risk). ## Indications and Contraindications - Indications: - Free flap breast reconstruction when abdominal donor sites are unavailable or undesirable; particularly suitable in patients with adequate gluteal tissue and smaller breast size. Mean flap weight reported ~400 g (range ~200–600 g). - Pedicled reconstructions: perineal defects, posterior thigh and sacral/perineal/pelvic dead-space filling. - Secondary option for patients wanting to avoid abdominal donor-site morbidity. - Contraindications / limitations (as stated in the source material): - Insufficient gluteal soft tissue or unfavorable buttock contour for adequate flap harvest (IGAP is best in pear-shaped habitus with relatively large buttocks and small breast size). - Relative increased operative time and complexity (position changes, tedious pedicle dissection) — may make IGAP less desirable in patients who cannot tolerate prolonged anesthesia or complex positioning logistics. - Donor-site factors increasing risk of wound complications (patients unable to comply with sitting restrictions; poor soft tissue quality at gluteal donor site). - The texts do not give strict absolute vascular contraindications (e.g., peripheral vascular disease or prior pelvic vessel sacrifice are not explicitly enumerated in these chapters), so preoperative imaging and individualized assessment are recommended. ## Postoperative Care - Monitoring: clinical monitoring of flap perfusion (color, turgor, capillary refill, bleeding on needle prick) is the operative standard described; specific monitoring devices or schedules are not mandated in the source chapters. - Drains and wound care: closed-suction drains placed beneath flap and in donor site; wounds closed in layers. Drains removed per routine volume criteria (not numerically specified in the sources). - Positioning / activity: - Avoid pressure on donor site during initial healing; some centers institute protocols that limit or avoid sitting in the early postoperative period to reduce risk of donor-site dehiscence (Blondeel; IGAP chapter). - For free-breast reconstruction, patient repositioning is required intraoperatively (harvest in lateral/ prone, inset and anastomosis in supine). Postoperative positioning should protect both donor and recipient sites (no specific timelines provided). - Antithrombotic practice / warming / analgesia / diet: - Specific antithrombotic regimens, warming protocols, analgesic plans and diet orders are not detailed in the referenced chapters; follow institutional microsurgical and perioperative protocols. - Mobilization: - Early mobilization with avoidance of direct pressure on the donor site as above; timing individualized. - Return-to-OR thresholds and time windows: - No explicit numerical thresholds or time windows are provided in the sources; clinical deterioration (loss of flap color, absent bleeding on needle prick, progressive venous congestion or arterial insufficiency) would prompt urgent re-exploration per standard microsurgical practice (not numerically specified in these texts). ## Complications (rates & management) - Reported/common complications (sources describe frequency qualitatively; no consistent numeric rates provided in these chapters): - Donor-site wound dehiscence — emphasized as the most distressing donor-site complication; associated with sitting/pressure on the wound. Management: prevention by avoiding early sitting; if dehiscence occurs, manage with local wound care, drainage control, and operative revision as needed. - Sensory disturbance / posterior thigh paresthesia — injury to the posterior femoral cutaneous nerve at the inferior margin of the flap can produce paresthesia of posterior thigh and leg; prevention by careful dissection and nerve preservation; management is symptomatic and may be permanent. - Sciatic nerve neuropraxia — related to excessive retraction or pressure during pedicle dissection; prevention by avoiding pressure on the nerve and careful retraction; management is supportive and may require neurologic follow-up. - Donor-site contour deformity / asymmetry — unilateral harvest may create asymmetry; secondary correction with liposuction or fat grafting may be required. - Flap shaping/contour issues — gluteal fat is firmer and denser than abdominal flaps and may require secondary fat grafting to improve breast contour. - Venous congestion / arterial thrombosis / partial or total flap loss — specific incidence figures and stepwise thrombolysis/leeching protocols are not provided in the referenced chapters. The texts recommend harvesting two perforators when possible to improve venous drainage and reduce congestion risk. - Gluteal thigh flap–specific notes (related anatomy and complications): flap pedicle mean arterial caliber reported 1.33 mm (gluteal thigh chapter). Flap dimensions up to 12–15 cm width and up to 30 cm length are described for gluteal thigh flaps; distal extent can approach within 8 cm of popliteal fossa. These are distinct but related pedicled-flap data (useful when planning perineal/posterior-thigh reconstructions). - Management algorithms: - The chapters emphasize prevention: select adequate perforators (pre-op imaging + Doppler), harvest two perforators when feasible, meticulous intramuscular dissection, protect nerves and avoid prolonged pressure on donor site post-op. - For donor-site dehiscence: early recognition, drainage, local wound care, and operative closure when indicated. - For suspected pedicle compromise intra- or postoperatively: prompt surgical exploration to assess and revise anastomoses or pedicle geometry (specific time windows and numeric success rates are not provided within the cited chapters). ## Key Clinical Pearls - Mark the gluteal fold with patient standing; inferior flap limit 1 cm inferior and parallel to the fold; superior limit ~7 cm cephalad; flap axis parallel to the fold — typical flap length ~18 cm (IGAP chapter, Fig. 31.2). - Prefer harvest of two perforators when possible to improve venous drainage; when only a single dominant perforator is used, meticulous dissection and postoperative vigilance are essential. - Expect pedicle length typically 7–10 cm; plan recipient-vessel exposure and intraoperative position changes accordingly (lateral harvest with supine anastomosis is common). - Vessel diameters to target for chest anastomosis: artery typically ~2.0–2.5 mm and vein ~3.0–4.0 mm when available (IGAP chapter). - Mean flap weight is approximately 400 g (range ~200–600 g) — useful when planning for breast-volume match. - Preserve and protect the posterior femoral cutaneous nerve at the inferior margin of the flap — injury results in posterior thigh/leg paresthesia which may be permanent. - Avoid incision into the ischial fat pad medially — this can cause prolonged sitting discomfort; close donor site in layers over suction drain and institute early sitting precautions to minimize dehiscence risk. - Be prepared for longer operative time because of position changes and detailed intramuscular pedicle dissection; preoperative imaging (CTA or MRA) and hand-held Doppler mapping reduce harvest time and improve perforator selection.