**Region:** Groin and Gluteal # Superior Gluteal Artery Perforator (SGAP) Flap ## Anatomy - Pedicle: superior gluteal artery (superficial branch perforator → superficial branch → possible dissection to SGA). Reported arterial diameters: 1.5–2.0 mm (small) and 2.0–4.5 mm (range reported across series); venous caliber 2.5–4.5 mm. Reported total pedicle length: mean ~9.8 cm (range 6.0–15.5 cm) and commonly 8–12 cm; perforator (intramuscular) length reported 3–8 cm (individual studies report mean 5.33 cm, range 3–11 cm). (Weichman; Kocak & Tiwari; Blondeel/Shokrollahi) - Course: originates from the posterior division of the internal iliac artery → exits pelvis through the greater sciatic foramen superior to piriformis → divides into superficial and deep branches. The superficial branch enters the deep surface of gluteus maximus and gives multiple perforators that traverse gluteus maximus to supply skin/subcutaneous tissue. - Perforator pattern: multiple perforators (mean reported 7.2, range 5–10 in one cadaveric/clinical study). Lateral perforators typically have a longer intramuscular course (reported 3–5 cm or up to 6 cm) and thus provide greater pedicle length; medial perforators tend to have shorter intramuscular course and shorter pedicle. One adequately sized perforator is often sufficient to perfuse the entire flap. (Weichman; Kocak & Tiwari; Blondeel) - Angiosome/adjacent choke zones: angiosome is superolateral gluteal region; flap perfusion depends on single dominant perforator with interconnections to adjacent gluteal angiosomes—lateral perforators give longer intramuscular run and better reach. (Blondeel/Shokrollahi) - Nerves: - Sensory: superior cluneal nerves supply skin of upper buttock and may be identified at superior incision margin. Described origins include terminal branches of the dorsal rami of lumbar nerves L1–L3 (Weichman) and predominantly L2–L3 in other series (Blondeel). When a sizable branch is encountered it can be dissected centrally for a sensate flap and coapted (preferred recipient: fourth intercostal for breast sensate reconstruction). (Weichman; Blondeel/Shokrollahi) - Motor: gluteus maximus motor innervation (inferior gluteal nerve) is encountered deep — dissection should preserve muscle fibers and motor supply by splitting along fibers rather than transecting. - Included tissues: - Skin and subcutaneous tissue (fasciocutaneous flap). Muscle is preserved (no routine muscle harvest). - Thickness profile: buttock fat tends to be firmer/denser than abdominal fat (less pliable, may give greater projection but more difficult to shape). (Kocak & Tiwari; Neligan) - Typical flap dimensions: reported up to 30 cm length × 12–13 cm width; commonly width 6–13 cm and length 20–25 cm (design based on tissue laxity and closure tension). Flap weights reported for SGAP 210–820 g in clinical series. (Weichman; Kocak & Tiwari) - Arc of rotation: limited by pedicle length; lateral perforators extend reach; pedicle length commonly 8–12 cm so plan recipient exposure/positioning accordingly. (Blondeel; Shokrollahi) - Common variants/anomalies: venous plexus deep to the sacral fascia can be complex and variable; significant variation in number, size, and intramuscular course of perforators between patients. (Neligan; Blondeel) ## Dissection Steps 1. Positioning, markings, landmarks. - Positioning: - Unilateral free SGAP: lateral decubitus (facilitates two-team approach: mastectomy/recipient vessel anterior, flap posterior). - Bilateral free SGAP: prone for harvest (may require repositioning to supine for anastomosis) or staged approach with two teams. (Weichman; Shokrollahi) - Surface markings: - Mark posterior superior iliac spine (PSIS), apex of greater trochanter, coccyx. - Draw line from PSIS → greater trochanter (Line 1) and divide into thirds; SGA emerges near junction of proximal and middle thirds. Draw PSIS → coccyx line and midpoint→greater trochanter line (piriformis surface landmark). Perforators commonly lie superior to the piriformis line and within a ~3‑cm radius of the SGA emergence point; majority near medial two-thirds / lateral one-third junction of PSIS–GT line. (Weichman; Kocak & Tiwari; Blondeel) - Preoperative imaging/ Doppler: - CTA or MRA in prone position is strongly recommended to map dominant perforators (describe exit point from deep fascia and intramuscular course). - Confirm perforators with handheld Doppler (authors recommend 5–8 MHz probe) and mark skin; prefer laterally located perforator when possible for longer pedicle. (Weichman; Kocak & Tiwari; Shokrollahi) 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Make only superior and lateral skin incisions first; begin dissection suprafascially above gluteus maximus toward the marked perforator(s). - Incise gluteal fascia over target region and continue in subfascial plane toward perforator. Bevel skin incisions outward 1–2 cm if additional bulk desired, but beware donor-site contour depression with overbeveling. (Weichman; Shokrollahi; Neligan) - Identify perforators at fascia perforation; inspect perforator arterial caliber (Shokrollahi recommends arterial caliber ≥1 mm) and presence of two venae comitantes. Select dominant perforator (single large perforator is usually sufficient). (Shokrollahi) 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Intramuscular dissection: - Split gluteus maximus fibers longitudinally in direction of fibers/septum rather than transecting muscle; follow perforator through muscle with bipolar and fine scissors under loupe magnification (or microscope for anastomosis). (Weichman; Shokrollahi) - Proceed medially/upward toward sacral fascia and piriformis. Use Gelpi retractors in piriformis/gluteus medius region for exposure. Avoid excessive traction on piriformis to prevent traction on sciatic nerve and postoperative neuropraxia. (Weichman; Shokrollahi) - Deep dissection / pedicle length: - Open sacral (posterior) fascia at deepest point; subgluteal fat pad contains fragile veins and multiple branches — meticulous hemostasis required. - If adequate length obtained prior to entering subfascial fat pad, consider stopping; otherwise dissect through fatty subfascial plane for additional 2–3 cm or more (reported gain ~2–3 cm). Total pedicle length commonly 8–12 cm; individual series report mean ~9.8 cm (range 6–15.5 cm). (Weichman; Shokrollahi) - Control & division: - Secure pedicle in pelvis with clips or ties as indicated; place two clips on SGA proximally if ligating for safety (caveat: ligated SGA may retract into pelvis). Place back-table ice and irrigation for free-flap ischemia time management. - Transfer/inset & perfusion checks: - Reposition patient as needed (to supine for chest work). Microsurgical anastomosis to chosen recipient vessels (internal mammary vessels commonly preferred because anterior location and calibre match; veins often larger). Perform perfusion checks clinically and with transcutaneous Doppler/ViOptix as available. Inspect skin paddle and ensure perforator is not kinked; the dense subcutaneous buttock tissue at perforator entry can act as inflexible pivot—tailor inset to avoid torsion/compression. (Shokrollahi; Blondeel; Weichman) 4. Donor-site closure techniques. - Close in layered fashion: deep muscle/fascia with interrupted figure-of-eight sutures; approximation of superficial fascial system; subcutaneous closed-suction drains placed deep and superficial to muscle; skin closed with deep dermal and skin sutures. - Avoid excessive undermining over iliac crest and greater trochanter to preserve periosteal skin ligaments and avoid contour deformity. Consider beveling and undermining to optimize closure without tension; large suction drains may be kept for up to 2 weeks in some protocols to reduce seroma. (Weichman; Blondeel; Shokrollahi) - Final checks: ensure no dog-ear over gluteal crease (orient skin island 45° cranial slant medially; fishtail medial run-out into gluteal crease to avoid medial dog‑ear). (Weichman) ## Indications and Contraindications - Indications: - Autologous breast reconstruction (immediate or delayed), including unilateral, bilateral, and stacked flaps when abdominal donor site is unavailable or unsuitable (prior abdominoplasty, insufficient abdominal tissue, patient preference). (Weichman; Kocak & Tiwari) - Pedicled applications: sacral pressure sore closure, lumbosacral and pelvic defects, pelvic dead-space filling (mobilized pedicled SGAP). (Shokrollahi; Blondeel) - Flap size/volume: flap dimensions up to ~30 cm length and 12–13 cm width have been used; flap weights reported 210–820 g (SGAP) — suitable for moderate to large reconstructions when abdominal tissue unavailable. (Weichman; Kocak & Tiwari) - Contraindications / relative limitations: - Major vascular disease of internal iliac / gluteal system (poor perforators or prior pelvic vessel injury) is a relative contraindication. - Prior gluteal surgery or scarring that destroys perforators or alters anatomy may preclude harvest. - Short pedicle limits reach — may preclude use when long arterial/venous reach is required without vein grafts (IGAP may have longer pedicle in some patients). (Neligan; Kocak & Tiwari) - Recent radiotherapy to donor region — delay and careful imaging; authors prefer waiting 6 months after breast/chest wall radiation before delayed reconstruction when applicable. (Weichman) ## Postoperative Care - Monitoring schedule / method: - Clinical + transcutaneous Doppler; adjuncts include ViOptix (tissue oximetry). Example monitoring schedule reported: q15 minutes × 2 hours, q30 minutes × 1 hour, q1 hour × 48 hours, then q2 hours until discharge. (Weichman) - Inspect skin paddle, turgor, capillary refill; Doppler signal and ViOptix trends. - Warming, antithrombotic practice: - Maintain normothermia; DVT prophylaxis with TED stockings/standard perioperative measures. Authors report routine postoperative aspirin for 30 days in one series; institutional antithrombotic protocols vary. (Weichman; Blondeel) - Positioning/splinting: - Avoid pressure on flap/donor site. For pedicled sacral reconstructions avoid direct pressure; some centers institute sitting restrictions early to reduce donor-site dehiscence (IGAP experience). (Blondeel; Neligan) - Drains: - Closed-suction drains placed at donor site; remove when output <30 mL/24 h per one protocol. Large suction drains at donor site for ~2 weeks reported in some series to reduce seroma. (Weichman; Blondeel) - Mobilization, diet/analgesia: - Sitting may begin POD1; ambulation POD1–POD2 depending on patient and repair. Foley typically removed POD2. Multimodal analgesia; intraoperative long-acting local (e.g., bupivacaine Exparel) + scheduled NSAIDs/ketorolac reported. (Weichman) - Return-to-OR thresholds and time windows: - Most vascular complications present within first 24–48 hours; prompt return to OR for suspected arterial or venous compromise is mandatory (time-critical — immediate evaluation and revision). (Weichman; Shokrollahi) ## Complications (rates & management) - Flap survival / loss: - Overall reported successful reconstructions with SGAP ~93%–97%. Estimated total flap failure rates reported between ~5% and 8% in some series. (Weichman; Guerra series cited) - Vascular events (largest series cited): arterial thrombosis 3.7%, venous thrombosis 3.7%, both arterial+venous 3.7%. Prompt takeback required for revision of arterial or venous anastomosis; most present in first 24–48 hours. (Weichman; Shokrollahi) - Donor-site complications: - Seroma: incidence reported up to 13.5%; suprafascial dissection may reduce seroma. Large drains and pressure garments recommended (1 month to 6 weeks reported). (Weichman; Blondeel) - Hematoma: 1%–3% reported. - Wound healing problems (dehiscence, infection): 4%–6% reported. - Contour deformity / asymmetry: may require revision fat grafting or contralateral liposuction; avoid excessive beveling and undermining to reduce donor depression. (Weichman; Neligan) - Fat necrosis: - Reported in SGAP flaps in range ~3%–6% (similar to other fasciocutaneous flaps). Management includes excision, liposuction, or fat grafting as augmentation. (Weichman) - Management algorithms: - Suspected arterial or venous insufficiency: urgent clinical assessment → immediate return to OR for exploration → revise anastomosis, evacuate hematoma, relieve kinking/torsion, consider thrombectomy/flush; institution-specific use of thrombolysis is not detailed in these sources — primary recommendation is surgical exploration. (Weichman; Shokrollahi) - Venous congestion of pedicled/remote flaps (sacral): consider release of constriction, re-establish drainage; in superficial venous congestion adjunctive measures (e.g., medicinal leeches) are sometimes used in reconstructive practice though not explicitly detailed in these chapters. (Blondeel/Shokrollahi — general principle: re-explore if concern) - Seroma: aspiration, prolonged suction drains, compression garments; minimize by suprafascial plane when feasible. (Weichman; Blondeel) - Donor-site dehiscence: conservative wound care vs. reclosure depending on size; avoid early sitting pressure. (Neligan) ## Key Clinical Pearls - Marking: find the SGA at the junction of the proximal and middle thirds of the line PSIS → greater trochanter; perforators concentrated within a ~3-cm radius of this point — plan flap centered over the chosen perforator. (Weichman; Kocak) - Perforator selection: a laterally placed perforator generally provides the longest pedicle but requires longer intramuscular dissection; inspect for arterial caliber ≥1 mm and adequate venae comitantes before committing. (Shokrollahi; Kocak) - Dissection technique: split gluteus maximus fibers in the direction of the fibers (longitudinal septal split) rather than transecting muscle; use bipolar cautery and loupe magnification for perforator dissection to preserve muscle function. (Weichman; Shokrollahi) - Deep plane hazard: the venous plexus beneath the sacral fascia is intricate and fragile — meticulous hemostasis; two proximal clips on SGA recommended if ligating for safety; be aware that ligated SGA may retract into pelvis and intrapelvic bleeding can be difficult to control. (Blondeel; Shokrollahi) - Incision strategy and closure: make superior and lateral incisions first; perform suprafascial dissection until periperforator area, then incise fascia; close donor site in layers over closed-suction drains and avoid undermining superiorly/laterally to prevent contour depressions and periosteal disruption. (Weichman) - Monitoring & timing: perform intensive flap checks early (example schedule: q15 min ×2 h, q30 min ×1 h, q1 h ×48 h) — vascular complications usually occur within first 24–48 hours; have a low threshold for takeback. (Weichman) - Postoperative adjuncts: use compression garments (authors report 1 month to 6 weeks) and consider prolonged suction drainage protocols (some groups report drains ~2 weeks) to minimize seroma. (Weichman; Blondeel) (Inline source hints: Weichman et al., "Superior Gluteal Artery Perforator Flap — Breast Reconstruction" (Chapter); Kocak & Tiwari; Shokrollahi/Blondeel/Shokrollahi et al. chapters in supplied PDFs.)