**Region:** Lower Extremity # Superior Lateral Genicular Artery Flap ## Anatomy - Pedicle: superior lateral genicular artery (SLGA) — typical origin ~4–6 cm proximal to the knee joint from the popliteal artery (may originate from sural artery in ~20% of cases). At origin the SLGA diameter reported as 1.8 ± 0.4 mm; accompanying vein(s) usually >1 mm. The SLGA divides at the lateral intermuscular septum into superficial and deep branches; the deep branch supplies the lateral femoral condyle while the superficial branch supplies patellar/skin branches. - Perforator pattern: usually 1–3 septocutaneous perforators that pierce the deep fascia at the lateral intermuscular septum between vastus lateralis and the short head of biceps femoris. Distance from knee joint to fascia penetration: 30–80 mm (mean ≈ 50 mm). Perforator-level metrics (from cadaver series): number 2 ± 1; superficial (pedicle) length 39 ± 22 mm; perforator diameter 0.8 ± 0.2 mm; total cutaneous territory ~100 ± 24 cm2; area per perforator ~55 ± 38 cm2 (Table data). - Course: perforators run superolaterally from the popliteal region, pass between vastus lateralis and biceps femoris, may give branches to vastus lateralis, biceps femoris and iliotibial tract, then arborize radially in the subcutaneous tissue and rete around the lateral patella. Perforators anastomose with lateral profunda perforators, popliteal/patellar rete, and descending branches of the lateral circumflex femoral artery. - Choke vessels/adjacent angiosomes: rich anastomoses to adjacent perforasomes (patellar rete, lateral profunda perforators, LCFA-descending) permit extension of the functional perforasome proximally into the midthigh and laterally across mid‑axial lines. - Nerves: no named motor or sensory nerve must routinely be sacrificed for flap harvest. If a cutaneous nerve accompanies the chosen perforator it can be included to create a sensate flap; otherwise the flap is typically non-sensate. Care around the intermuscular septum avoids injury to branches to vastus lateralis or short head of biceps femoris. - Included tissues: skin and subcutaneous tissue ± fascia lata; flap can be raised as fasciocutaneous perforator flap. The SLGA vascular axis can also supply periosteum/cortex of the lateral femoral condyle (lateral femoral condyle [LFC] flap) permitting chimeric constructs with bone/osteochondral components. Flap thickness: inherently thin (favorable for periarticular resurfacing). Arc of rotation: adequate for lateral/anterior peri‑patellar and proximal lateral knee defects; limited reach to medial/distal knee without chimeric/free transfer. Common variants/anomalies: SLGA absent or few perforators; superficial branch sometimes absent; origin from sural artery in ~20% of cases; proximal vascular connections variable. ## Dissection Steps 1. Positioning, markings, landmarks. - Position: supine with knee slightly flexed and externally rotated (figure-of‑four or slight bolster under ipsilateral hip as needed). - Landmarks: superolateral patella, lateral femoral condyle, anterior margin of short head of biceps femoris, posterior margin of vastus lateralis. Perforator-rich triangular zone formed by superior margin of lateral femoral condyle, posterior margin of vastus lateralis, and anterior margin of short head of biceps femoris. - Preop perforator localization: handheld Doppler commonly used; color duplex sonography or selective angiography recommended if available (Doppler has false-positives). Scatter/mapping guidance: highest perforator density ~3–7 cm proximal to joint line and ~5–8 cm lateral to a line joining ASIS to superolateral patella. - Flap design: provisional design centered on the selected perforator; axis parallel to lateral mid‑axial line. For propeller/local flaps design is eccentric to allow rotation; for free flap design centralizes perforator. 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Initial incision along anterior border of planned flap; dissect in loose areolar plane superficial to deep fascia to locate perforators. Confirm audible/visual perforator(s); mark best perforator(s). - Preserve all perforators encountered until pedicle chosen; do not divide secondary perforators until pedicle fully mobilized. 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Incise fascia lata to expose perforator entry. Retrograde dissection from superficial plane into intermuscular septum between vastus lateralis and short head of biceps femoris. - Carefully dissect perforator pedicle retrograde into the lateral intermuscular septum to gain length (reported superficial pedicle length ~39 ± 22 mm at perforator level). Identify SLGA main trunk and branches in the septum; preserve venae comitantes. - If pedicle length adequate for pedicled transfer, rotate flap (propeller up to 180° possible) and inset avoiding kinking/torsion. If performing free transfer, divide pedicle and perform microvascular anastomoses to chosen recipient vessels. - If harvesting chimeric LFC component, identify osteoarticular branch of SLGA/branch to lateral condyle in the same dissection corridor and mobilize with bone/periosteum as required. - Perfusion checks: visual capillary refill, bleed from flap edges; adjunctive intraoperative indocyanine green angiography has been used to confirm perfusion after inset (documented in clinical series). 4. Donor-site closure techniques. - Assess pinch test before harvest. Donor-site primary closure feasible in most cases when flap width ≤ 10 cm; if wider, consider skin graft for donor site. - If fascia lata included, place drains to reduce seroma risk; layered closure. Avoid compressive dressings over pedicle. ## Indications and Contraindications - Indications: - Local/pedicled coverage of soft-tissue defects around lateral and anterior knee, peripatellar region. - Free flap transfer for distal upper‑ or lower‑extremity soft tissue defects where a thin fasciocutaneous flap is needed. - Chimeric reconstruction combining skin + fascia lata, muscle, cartilage or vascularized lateral femoral condyle bone/osteochondral component for complex multi‑tissue defects. - Aesthetic/functional reconstructions requiring a thin pliable flap with minimal donor‑site morbidity. - Size limits (anatomic data): - Cutaneous territory of SLGA perforators: total ~100 ± 24 cm2; area per perforator ~55 ± 38 cm2 (cadaver metrics). Donor width for primary closure generally targeted ≤ 10 cm. - Contraindications: - Prior surgical trauma or scars in the lateral thigh that have likely sacrificed perforators or reduced skin reservoir. - Absent or inadequate perforator on preoperative mapping. - Patients unwilling to accept a lateral thigh scar or in whom primary donor closure cannot be achieved and skin graft donor is unacceptable. - For local pedicled use: defects located medially or distally beyond flap arc of rotation (limited reach). ## Postoperative Care - Monitoring schedule/method: - Early postop clinical monitoring frequently in the first 24–48 hours (capillary refill, color, turgor). - Adjunct intraoperative or immediate postoperative perfusion imaging (indocyanine green angiography) has been used intraoperatively and post‑inset in case series to confirm perfusion. - Warming/positioning: - Immobilize knee in neutral position for pedicled transfers; keep limb elevated to reduce edema and promote venous return. Avoid compression of pedicle pathway. - Drains: - Place drains when fascia lata is included to mitigate seroma formation; remove per local protocol when output minimal. - Antithrombotic practice: - No SLGAP‑specific protocol provided in the cited material; follow institutional microvascular thromboprophylaxis standards. - Mobilization: - Early mobilization as permitted by implant/bone stability if chimeric bone component included; otherwise limit tension on inset and avoid positions stressing pedicle. - Return-to-OR thresholds and time windows: - Not specified in the available texts; standard microsurgical practice applies — urgent return for signs of arterial or venous compromise. ## Complications (rates & management) - Anatomic/harvest-related: - Absence or paucity of perforators (SLGA or perforator may be absent or superficial branch absent) — described as an anatomic variant; preop mapping recommended to avoid intraoperative surprises. - Donor‑site seroma when fascia lata harvested — anticipated; drains and tight dressing reduce incidence. - Flap failure / vascular events: - Typical microsurgical risks (arterial thrombosis, venous congestion) are possible; specific frequency data for SLGAP not reported in the attached material. - Management principles (general microsurgery): urgent return to theatre for exploration if arterial/venous compromise suspected; correct mechanical causes (kinking/compression), revise anastomosis if thrombosed, consider leech therapy only for venous congestion when indicated (not specifically cited in provided texts). - Donor-site morbidity: - Primary closure possible for widths ≤ 10 cm; skin graft required otherwise — aesthetic concern especially in women. - If chimeric harvest includes lateral femoral condyle (osteous) component, potential donor‑site risks for bone harvest are highlighted in related literature (see medial/LFC discussions) — iatrogenic fracture risk and functional implications reported in separate MFC/LFC references (not SLGAP‑specific). Always limit bone harvest dimensions and consider prophylactic measures (e.g., packing defect with cancellous graft). - Infection, fat necrosis, partial flap loss: - Not quantified in the SLGAP chapter; standard wound care and early intervention recommended. ## Key Clinical Pearls - Preoperative mapping is essential: use handheld Doppler as screening but employ color duplex or angiography if uncertainty exists — SLGA perforators cluster ~3–7 cm proximal to the joint line and ~5–8 cm lateral to the ASIS–superolateral patella line. - Perforator anatomy metrics to plan harvest: expect 1–3 perforators; perforator skin‑penetration distance 30–80 mm (mean ≈ 50 mm); perforator pedicle superficial length ≈ 39 ± 22 mm; perforator diameter ≈ 0.8 ± 0.2 mm — plan pedicle dissection into the intermuscular septum for length. - Initial exposure: make an anterior exploratory incision and dissect in the loose areolar plane over deep fascia; preserve all perforators encountered until one optimal pedicle is chosen. - Pedicle dissection corridor: work retrograde into the lateral intermuscular septum between vastus lateralis and short head of biceps femoris to identify SLGA trunk and obtain pedicle length — avoid muscle branch injury. - Donor closure planning: perform a pinch test pre‑incision; aim for donor width ≤ 10 cm for primary closure; if fascia lata harvested, anticipate and drain to prevent seroma. - Chimeric use: SLGA can supply an LFC (lateral femoral condyle) osteo/periosteal component — enables bone/osteochondral chimeric constructs from same pedicle for complex reconstructions. - Intraoperative perfusion confirmation: indocyanine green angiography has been used successfully to confirm perfusion after inset.