**Region:** Lower Extremity # Lateral Circumlex Femoral Artery (TFL and Vastus Lateralis) Flaps ## Anatomy - Pedicle: named artery (typical diameter/length if present), venae comitantes; course from origin to flap/skin paddle; perforator pattern (number, location, intramuscular vs septocutaneous), choke vessels/adjacent angiosomes. - Lateral circumflex femoral artery (LCFA) system — descending branch supplies the anterolateral thigh (ALT / LCFA–vastus lateralis) flap; LCFA usually arises from the profunda femoris artery and is slightly larger than the medial circumflex femoral artery (LCFA ~4 mm at origin vs MCFA ~3 mm in typical descriptions) (Anatomy chapter). The descending branch that becomes the ALT pedicle commonly tracks deep to rectus femoris along the septum between rectus femoris and vastus lateralis (ALT chapter). - Typical pedicle caliber and length: LCFA/descending branch arterial caliber ~2–3 mm (ALT chapter); pedicle length for ALT often ≈8 cm but variable with perforator choice (ALT chapter). TFL perforator pedicle length typically reported 7–8 cm (TFL chapter). CTA of TFL region reported mean skin‑vessel pedicle length 8.3 cm (TFL chapter). - Venae comitantes: two venae comitantes accompany LCFA branches and drain to profunda/ femoral venous system (Anatomy chapter). - Perforator pattern: - ALT (LCFA–vastus lateralis): perforators most commonly musculocutaneous (≈80%) with septocutaneous perforators more often proximally; average reported LCFA perforator counts ~10 ± 5 per thigh supplying the anterolateral territory (diameter ~0.7 ± 0.3 mm, superficial length ~33 ± 15 mm, area ~362 ± 121 cm2; musculocutaneous:septocutaneous ratio ~3:1) (Anatomy table, ALT chapter). The principal “B” perforator is typically at the midpoint of the line ASIS→lateral patella, often 1.5 cm posterior to midpoint; “A” and “C” commonly about 5 cm proximal and distal to “B,” respectively (ALT chapter). - TFL (ascending branch LCFA → TFL perforator flap): skin perforators cluster medial→lateral; CTA/MRA series report mean 2.5 skin vessels per TFL, 66% septocutaneous and 34% musculocutaneous (TFL chapter). TFL skin vessel size on CTA reported mean ≈3 mm (TFL chapter). - Choke vessels/angiosomes: distal LCFA communicates with superior lateral genicular circulation around the knee; long anastomotic chains exist between profunda, genicular and tibial systems (Anatomy chapter, ALT chapter). - Nerves: sensory and motor branches relevant to flap harvest and sensate reconstruction. - Lateral femoral cutaneous nerve (L2–L3) supplies cutaneous sensation in the anterolateral thigh region and emerges from deep fascia ~10 cm below ASIS (ALT chapter; Anatomy chapter). When sensate flaps are desired, branches of this nerve may be preserved or coapted. - Motor nerves: branches to vastus lateralis accompany the descending branch and may be encountered during intramuscular perforator dissection (ALT chapter). The motor nerve to TFL lies adjacent to the ascending branch; avoid injury if goal is to preserve muscle function (TFL chapter). - Included tissues: skin/subcutaneous/fascia/muscle; thickness profile; arc of rotation; common variants/anomalies. - ALT (LCFA–vastus lateralis): fasciocutaneous perforator flap is typical; can be harvested myocutaneously (include portion of vastus lateralis) or chimerically with rectus femoris/TFL; can include fascia lata for tendon reconstruction or muscle for bulk/obliteration (ALT chapter). Skin paddle width typically kept ≤8 cm to allow primary closure of donor site; larger paddles often need grafting (ALT chapter). Superthin/suprafascial variants possible; if thinned, preserve ~2 cm radius around the perforator (ALT chapter). - TFL perforator flap: fasciocutaneous flap, consistent septocutaneous perforators, limited pedicle length and somewhat smaller safe skin territory compared with ALT; useful pedicled option for trochanteric region (TFL chapter). Microdissected thin TFL flaps possible; reported practical maximum single‑perforator flap dimensions variable (see Disadvantages/Numbers) (TFL chapter). - Variants/anomalies: LCFA occasionally gives an oblique branch that can be the perforator origin; perforator origin may be from transverse/ascending branches rather than descending; absence of ALT skin perforators is uncommon but reported (~1.8% in pooled series) (Anatomy chapter; ALT chapter). TFL CTA series: ~2.5 skin vessels per thigh, though anatomy is consistent overall (TFL chapter). ## Dissection Steps 1. Positioning, markings, landmarks. - Position: supine for both ALT (LCFA–vastus lateralis) and TFL harvests (ALT and TFL chapters). Legs rotated so toes point anteriorly for accurate longitudinal markings (ALT chapter). - Landmarks: mark ASIS and lateral patella and draw line joining them (ASIS→lateral patella axis) (ALT chapter). Midpoint of that line is the classic location for the primary ALT perforator (“B”); mark 1.5 cm posterior to midpoint as likely perforator location; mark “A” ~5 cm proximal and “C” ~5 cm distal if mapping (ALT chapter). For TFL, anticipate perforators entering TFL 7–12 cm distal to ASIS; preoperative Doppler or CTA/MRA can refine locations (TFL chapter). - Preop imaging: if limb vascular disease or complex harvest planned, consider CTA/MRA or color Doppler ultrasound to map perforators (Anatomy; TFL chapter; ALT chapter). 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Use handheld Doppler to localize perforators inside the 3‑cm radius centered at the midpoint of ASIS→lateral patella for ALT; if none, extend search caudally/proximally along that line (ALT chapter). - Choice of plane: - ALT: can be elevated subfascially (easier visualization of septum and vascular pedicle), suprafascially, or using the Scarpa‑like fascial plane for thinner flaps (ALT chapter). Suprafascial harvest preserves cutaneous nerves and minimizes donor‑site trauma but makes pedicle access more demanding (ALT chapter). - TFL: initial incision slightly medial to vertical ASIS→patella line and dissect suprafascially to identify septocutaneous perforators; if absent, proceed laterally to find musculocutaneous perforators and plan intramuscular dissection (TFL chapter). - Perforator selection: favor a large caliber perforator with shortest simple intramuscular course; if perfusion risk, include two or more perforators or design multiple islands (ALT chapter; TFL chapter). 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - ALT pedicle exposure: - Make medial incision and develop subfascial plane laterally to the intermuscular septum between rectus femoris and vastus lateralis. Open septum and retract rectus femoris medially to expose the descending branch and perforators (ALT chapter). - If septocutaneous perforator present, dissect it directly; if musculocutaneous, perform intramuscular dissection through vastus lateralis to origin from descending branch; ligate branches distal to flap; preserve rectus femoris branch when possible (ALT chapter). - TFL pedicle exposure: - Identify septal or muscle perforator at TFL deep fascia hiatus; extend fascia incision and dissect intramuscularly toward the ascending branch as needed. For longer pedicle or larger caliber, retract rectus femoris and sartorius medially and skeletonize back to LCFA origin (TFL chapter). - Microdissection (Kimura technique) if thin flap desired: sharply remove deep fascia around perforators under magnification, bluntly remove surrounding fat lobules, and preserve a 2‑cm radius around perforator if thinning (TFL chapter; ALT chapter). - Pedicle handling: preserve a cuff of fascia around the perforator for traction, mark anterior pedicle surface when long pedicle tunneled or rotated to prevent twisting (ALT chapter; TFL chapter). - Division and transfer: clamp/clip distal branches, ligate distal LCFA branch if needed, divide pedicle and transfer. Confirm perfusion clinically and with Doppler/ICG as available (ALT chapter; TFL chapter recommends ICG for megaflaps). - Insetting: eccentric placement of perforator within skin paddle can extend reach; chimeric designs (separate skin/muscle/fascia islands) enable independent insetting (ALT & TFL chapters). 4. Donor-site closure techniques. - Primary closure feasible if flap width <8 cm (ALT & TFL chapters). For wider defects, options: skin graft, vacuum‑assisted dressings over graft, or local advancement/propeller perforator flaps (ALT chapter; donor‑closure notes). “Purse‑stringing” dermal running absorbable suture (2‑0/3‑0) can reduce skin defect and need for grafting (ALT chapter). Place closed suction drain in donor site when indicated (ALT chapter). ## Indications and Contraindications - Indications: - ALT (LCFA–vastus lateralis): workhorse for soft‑tissue reconstruction of head & neck, extremity, trunk, phalloplasty, perineal, scalp; thin or bulky options depending on thinning or inclusion of vastus lateralis; chimeric possibilities for composite defects (ALT chapter; Anatomy chapter). - TFL perforator: second‑line free flap or pedicled option—trochanteric pressure‑sore reconstruction, salvage when ALT perforators absent/unreliable, or to augment a thigh mega‑flap; useful when consistent septocutaneous perforators present (TFL chapter). - Chimeric combinations: include fascia lata, vastus lateralis, rectus femoris, iliotibial tract; LCFA system allows large composite or “mega” flaps when multiple branches/perforators joined (TFL & ALT chapters). - Contraindications: - Significant peripheral arterial disease / atherosclerosis without preop vascular imaging (consider CTA/angiogram) — risk of limb ischemia (Anatomy chapter; ALT chapter). - Prior surgery, trauma, or radiation that has destroyed perforators in donor region (relative/absolute per clinical judgement — absent perforators reported ~1.8% overall) (Anatomy chapter). - Medical comorbidities that preclude long operations or microsurgery (standard surgical contraindications; explicit periop antithrombotic protocols not specified in these chapters). ## Postoperative Care - Monitoring schedule/method: - Clinical checks and handheld Doppler for skin paddle monitoring as standard (ALT/TFL chapters). Use ICG angiography intraop for large/conjoined flaps to assess perfusion when available (TFL chapter). - For buried/osteocortical components (e.g., MFC), consider chimeric skin paddle as sentinel monitor (MFC chapter). - Warming/positioning: - Standard limb warming and avoidance of external compression over pedicle. Specific protocols for warming not detailed in provided chapters. - Antithrombotic practice: - No standardized protocol provided in the reviewed chapters; follow institutional microvascular protocols. - Drains, mobilization, diet/analgesia: - Closed suction drain commonly placed in donor site for ALT; vacuum dressing over skin grafts for donor site if needed (ALT chapter). Early mobilization per recipient site and fixation stability (MFC grafts often require protection/nonweightbearing until consolidation) (MFC chapter). - Return‑to‑OR thresholds and time windows: - Immediate re‑exploration for signs of vascular compromise (e.g., rapidly worsening color, loss of Doppler signal, tense hematoma). Institutional re‑exploration rates and salvage outcomes cited for ALT series: success 96.58%, re‑exploration 7.47% with 56% salvage of compromised flaps in one series (ALT chapter). No rigid time windows stated in the source chapters — standard microvascular principle: re‑explore promptly when compromise suspected. ## Complications (rates & management) - Venous congestion, arterial thrombosis, flap compromise: - ALT institutional data (example series in chapter): overall flap success ~96.58%; re‑exploration rate ~7.47%; of compromised flaps, ~56% salvaged upon re‑exploration (ALT chapter). - Management algorithm for inadequate/absent skin vessel intraop (ALT chapter): search medially for alternative perforator; convert to musculocutaneous flap (include vastus lateralis) if intramuscular dissection not feasible; perform freestyle search for other thigh perforators; if none workable, abandon donor and select alternative donor site. - Partial/total loss, infection, fat necrosis: - No pooled percentages for general infection/fat necrosis reported in the focused chapters; use standard flap management (debridement, antibiotics, re‑exploration as indicated). - Donor-site issues (seroma, hematoma, contour deformity, hernia/weakness) with typical frequencies when reported: - Thigh donor primary closure usually straightforward if flap width <8 cm; otherwise skin graft or local flap. Donor‑site morbidity after ALT harvest generally low; pooled analyses show measurable strength deficit mainly if rectus femoris included (ALT chapter; pooled donor morbidity systematic review referenced). - MFC donor complications: iatrogenic femoral fracture and knee dysfunction are uncommon but reported — quoted MFC donor‑site morbidity figures: fracture 0.8%, knee dysfunction 0.4% in pooled data (MFC chapter). - Management algorithms (re‑exploration, leeching, thrombolysis): what, when, how. - Re‑exploration for arterial or venous compromise should be immediate — inspect anastomosis for technical issues, evacuate hematoma, relieve pedicle twist/compression, consider thrombectomy or revision of anastomosis; leeching described where venous congestion cannot be otherwise relieved (general microsurgery practice; re‑exploration statistics cited in ALT chapter). Specific pharmacologic thrombolysis protocols not detailed in these chapters. ## Key Clinical Pearls - Mark the ASIS→lateral patella line and expect the principal ALT perforator (“B”) near the midpoint (often 1.5 cm posterior to midpoint); check “A” and “C” ~5 cm proximal/distal to augment options (ALT chapter). - Expect ALT perforators to be mostly musculocutaneous (~80%); septocutaneous perforators are more likely proximally but are present overall less often (Anatomy; ALT chapters). - Typical safe donor closure: plan skin paddle width ≤8 cm for primary closure; wider paddles usually require grafting or local closure maneuvers (ALT chapter). - Preserve a 2‑cm radius around any perforator when thinning a flap (superthin/suprafascial technique) — do not thin to the perforator margin (ALT & TFL chapters). - Use a cuff of fascia around the perforator/pedicle during dissection and mark the anterior pedicle surface to prevent inadvertent twisting/torsion when inset or tunneling (ALT chapter). - TFL flap: expect a relatively short pedicle (≈7–8 cm) and consistent septocutaneous anatomy; CTA/MRA or Doppler can identify ~2.5 vessels per thigh and guide harvest (TFL chapter). - If the descending genicular/ostearticular branch is planned for an MFC corticocancellous flap, preserve and confirm the DGA; if absent, the superior medial geniculate artery may supply the MFC and must be preserved until anatomy clarified (MFC chapter). Pack MFC donor site with cancellous graft when possible to reduce long‑term cortical defect (MFC chapter). - Anticipate anatomical variants: the oblique LCFA branch exists and can supply TFL/ALT territory; absence of reliable skin perforator is uncommon but possible (~1.8% reported); have an alternate donor plan (Anatomy; TFL; ALT chapters).