**Region:** Groin and Gluteal # Singapore Flap ## Anatomy - Pedicle: superficial perineal artery (branch of the internal pudendal vessels) with accompanying venae comitantes. The superficial perineal vessels interconnect with branches of the deep external pudendal artery and the medial circumflex femoral artery (from the profunda femoris). Course: vessels originate from the internal pudendal system and supply the proximal medial thigh skin in the region of the thigh crease; perforators to the skin are present but are not subjected to routine individual perforator dissection for this flap (Hanasono et al.). - Perforator pattern: multiple cutaneous perforators exist in the proximal medial thigh territory; the flap is elevated including the deep fascia to maximize perfusion and innervation. No specific perforator counts or fixed intramuscular/septocutaneous ratios are given in the source; special perforator skeletonization is not required. - Choke vessels / adjacent angiosomes: the superficial perineal arterial territory communicates with external pudendal and medial circumflex femoral systems; explicit choke vessel details are not provided in the cited chapter. - Nerves: sensory supply relevant to flap harvest and potential sensate reconstruction includes posterior labial branches of the pudendal nerve and perineal branches of the posterior cutaneous nerve of the thigh. Motor branches are not described as part of the flap (sensory innervation emphasized) (Hanasono et al.). - Included tissues: skin, subcutaneous fat, and deep (adductor) fascia are included routinely to maximize perfusion and preserve innervation. The flap is characteristically thin (even in obese patients) and does not provide substantial bulk. - Thickness profile / arc of rotation: thin fasciocutaneous profile; arc of reach is regional — posteriorly based flaps are tunneled under or transposed across the vulva to reach posterior/lateral vaginal and vulval defects. Flaps may be islanded and tunneled or transferred without islanding depending on local anatomy and perfusion needs. - Common variants/anomalies: unilateral or bilateral designs; posteriorly based (superficial perineal vessels) and anteriorly based variants (perfused by external pudendal vessels) exist; the posterior skin may be left intact (non‑island) to avoid tunneling and maximize perfusion. Typical planned maximum dimension reported: up to 15 cm length × 6 cm width (adjusted to donor laxity and ability to close donor site) (Hanasono et al.). ## Dissection Steps 1. Positioning, markings, landmarks. - Position: lithotomy for most applications. - Landmarks/markings: medial border of flap placed lateral to the hair-bearing vulva within the thigh crease; posterior skin margin marked at the level of the posterior fourchette. Mark flap length and width according to defect and donor laxity (documented examples up to 15 × 6 cm); tailor width to permit primary donor-site closure without undue tension (Hanasono et al.). 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Plane: incise through skin and subcutaneous tissue and include the deep fascia over the adductor musculature; elevate in the subfascial plane from anterior distal toward proximal. - Perforator identification: routine perforator skeletonization is not required. Preoperative imaging is not routinely required for this flap; intraoperative handheld Doppler or visual assessment may be used, and capillary refill/clinical assessment suffices for many cases. If desired, intraoperative fluorescent angiography (indocyanine green) or Doppler testing may be used to assess perfusion (Hanasono et al.). 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Exposure/control: elevate from distal to proximal in the subfascial plane; identify proximal vascular region but avoid aggressive dissection or skeletonization of perforators when not necessary. - Division: flap is a pedicled transfer — do not divide the pedicle; if tunneling is planned, ensure adequate pedicle length and avoid kinking. - Transfer/inset: secure the distal extent of the flap to the recipient defect first to confirm reach and lack of tension; if transposition is tight, lengthen posterior incision and/or make a back-cut. If bilateral flaps are used, they may be approximated to each other in the midline before final inset. Deepithelialization of distal tips may be used when tucking beneath mucosa is preferred (examples in rectovaginal fistula repair). - Perfusion checks: intraoperative clinical assessment (capillary refill, dermal bleeding) is primary. Indocyanine green (ICG) angiography is cited as an adjunctive test where available. If distal perfusion appears marginal, options are: (a) trim distal poorly perfused tissue, (b) reinset to the donor site and plan a delayed transfer, or (c) delay the flap and re-elevate later (Hanasono et al.). 4. Donor-site closure techniques. - Primary layered closure is standard. Wide undermining of medial thigh skin may be necessary to mobilize tissues for direct closure. - Reapproximate deep and superficial fascial layers to reduce skin tension; use absorbable sutures for deep layers and either absorbable or permanent for skin per surgeon preference. - Drains: not used routinely; consider drain placement when fluid collection risk is high. - Postoperative limb position (thigh adduction) for 2–3 weeks is recommended to reduce tension and risk of donor- or recipient-site dehiscence (Hanasono et al.). ## Indications and Contraindications - Indications: - Posterior and/or lateral vaginal wall defects. - Rectovaginal fistula repair. - Vulvectomy and vulval reconstruction. - Perineal defects. - Penile and scrotal reconstruction (often in combination with other flaps, e.g., gracilis); suitable primarily for smaller resurfacing needs. - Best suited when a thin, sensate (partial sensory) tissue is desired rather than bulk — not ideal for large pelvic exenteration cavities where volume is required (Hanasono et al.). - Contraindications: - Absolute: prior flap harvest or resection that destroyed the regional blood supply (i.e., area of the superficial perineal vessels). - Relative: previous surgery or radiation to the donor region (may reduce perfusion), significant systemic comorbidities that impair wound healing or local perfusion. The chapter notes radiation is more commonly at the recipient site than at the donor site, which often leaves the Singapore flap viable (Hanasono et al.). ## Postoperative Care - Monitoring schedule/method: - Primary monitoring: clinical bedside assessment of flap color, capillary refill, bleeding from skin edges, and temperature. - Adjunct intraoperative/in-hospital tools: indocyanine green (ICG) angiography may be used intraoperatively for perfusion assessment; Doppler may be used but is not emphasized as mandatory in the source. - No implantable probe protocol is described for this flap in the cited chapter. - Warming/antithrombotic practice: - Specific warming protocols and antithrombotic regimens are not specified in the source material. - Positioning/splinting: - Thigh adduction for approximately 2–3 weeks postoperatively is recommended to reduce tension and lower risk of donor/recipient-site dehiscence. - Drains: - Not routinely used; consider for high-risk fluid collections. - Mobilization/diet/analgesia: - The chapter does not give prescriptive timelines for mobilization, diet, or analgesia. Case examples indicate return to activities of daily living by 3 months in uncomplicated cases; early mobilization is implied where wound closure is secure. - Return-to-OR thresholds and time windows: - Not prespecified numerically in the text. The operative decision-making described: if intraoperative or immediate postoperative perfusion is inadequate, options include trimming distal tissue, conversion to delay procedure, or reinset and delay — prompting re-operation if needed based on clinical perfusion findings (Hanasono et al.). ## Complications (rates & management) - Reported frequencies/rates: the provided chapter does not supply numeric complication rates for the Singapore flap. - Potential recipient-site complications and management (as described or implied in source): - Distal ischemia/partial loss: intraoperative assessment (capillary refill, ICG) guides whether to trim distal tissue or delay the flap; delayed transposition is an option when perfusion concerns exist. - Wound dehiscence (donor or recipient): often related to tension — prevention through tailoring flap width to permit tension‑free closure and reapproximating fascial layers; thigh adduction postoperatively may reduce risk. Re-exploration or revision closure is implied if dehiscence occurs. - Infection, hematoma, seroma: drains are discretionary when fluid collection risk is high; standard management (drainage, antibiotics) is implied but not specified. - Donor-site issues: - Contour deformity, scarring, and standing cone deformity if closure performed under tension. Primary closure and wide undermining with layered fascial repair are recommended to minimize these. - Seromas/hematoma: specific frequencies not provided. Drains recommended selectively. - Management algorithms: - Perfusion concern intraoperatively: evaluate clinically (capillary refill), consider ICG; if distal tissue marginal → trim or delay. - For tension-related donor-site problems: avoid excessive flap width; if problems occur, revise to reduce tension, consider delayed closures or small skin grafts from trimmed flap tissue (noted as a strategy in analogous flap literature; the Singapore flap chapter explicitly recommends tailoring width to allow primary closure and notes the use of deepithelialized tips when appropriate). ## Key Clinical Pearls - Typical maximum flap dimensions cited in clinical practice: design up to 15 cm length × 6 cm width, but always tailor to laxity and the ability to close the donor site primarily (Hanasono et al.). - To maximize perfusion in challenging patients, leave the posterior flap skin intact (do not island) rather than tunneling the flap; this avoids a tight tunnel and preserves blood supply. - If intraoperative assessment reveals marginal distal perfusion, convert to a planned delay or trim the distal segment rather than force a high‑risk inset. - Prefer bilateral flaps for large defects rather than overextending a single unilateral flap; bilateral flaps may be sutured together midline to reconstruct wider surfaces. - Avoid closing the donor site under significant tension — wide undermining and layered fascial repair reduce tension and standing‑cone deformity. - The flap is thin even in obese patients and often provides suitable coverage where bulk is undesirable (e.g., vaginal lining, vulvar resurfacing). - Postoperatively keep thighs adducted for approximately 2–3 weeks to reduce tension on closures and lower risk of dehiscence. - Drains are not routine; use selectively when fluid collection risk is high. Use intraoperative perfusion adjuncts (e.g., ICG) where available to guide trimming versus delay decisions.