**Region:** Lower Extremity # Anteromedial Thigh Flap ## Anatomy - Pedicle: rectus femoris branch of the descending branch of the lateral femoral circumflex artery (LFCA) when clinically useful — provides a pedicle similar in length and diameter to the ALT pedicle (descending LFCA; LFCA caliber ≈ 2–3 mm). Perforator origin and course: - Typical origin: branch to rectus femoris from the descending branch of the LFCA; pedicle emerges medial to rectus femoris in the proximal thigh between rectus femoris and sartorius, then continues distally between rectus femoris and vastus medialis (AMT territory). - Alternate origin: directly from the superficial femoral artery (SFA). SFA-derived perforators are more distal and short (reported length 3–5 cm) and generally render the AMT flap clinically unusable for a long pedicle. - Perforator pattern: most thighs with adequate AMT perforators have a single usable perforator. When present and usable it typically splits into branches before entering rectus femoris, emerging as septocutaneous perforators between rectus femoris and sartorius/vastus medialis or as musculocutaneous perforators through rectus femoris. - Surface location: on the AP line (line connecting ASIS to superomedial border of patella), the AMT B-perforator averages 3.2 cm medial to the AP line; A and C perforators (if present) are located approximately 5 cm proximal and 5 cm distal to the B perforator on that axis. (Quantitative data from anatomic series.) - Reciprocal/compensatory anatomy: there is reciprocal dominance between ALT and AMT perforators — in thighs lacking usable ALT perforators there is a near 100% chance of adequate AMT perforators; when only one ALT perforator is present, a usable AMT perforator exists in ~75% of those thighs. - Pedicle length/diameter: when AMT perforators arise from the rectus femoris branch the resultant pedicle provides length and diameter comparable to ALT pedicles (ALT pedicle length ~8 cm; LFCA caliber ≈ 2–3 mm for comparison). - Venous drainage: venae comitantes accompany the arterial pedicle (as with LFCA-derived thigh pedicles). - Choke/linking vessels: linking vessels connect adjacent perforasomes; AMT perforators have communicating choke vessels with adjacent thigh territories (relevant for multipaddle or extended designs). - Nerves: - Motor: branches to rectus femoris and surrounding muscles run adjacent to the pedicle; care to preserve or repair if divided. - Sensory: the anteromedial skin territory itself is not routinely raised as a sensate flap in the same way as ALT (LFCN for ALT), and specific sensory nerve inclusion is not routinely described for AMT; however nerve branches to muscle may be encountered and are deep to vessels. - Included tissues: - Skin, subcutaneous tissue, and fascia overlying the anteromedial thigh; flap may be harvested as fasciocutaneous, myocutaneous (with rectus femoris), or chimeric with adjacent ALT/rectus components. - Thickness profile: similar to ALT territory; thickness varies with patient habitus — if thigh subcutaneous fat >2 cm a different flap may be preferable for thin resurfacing needs. - Typical skin paddle characteristics: donor-site primary closure usually possible when width ≤ 8–9 cm; wider paddles typically require split-thickness skin grafting. - Common variants/anomalies: AMT perforators may arise from SFA (short, distal, 3–5 cm) — these are generally unsuitable; AMT perforators associated with rectus femoris branch in ~51% of thighs in series; most usable AMT flaps will have a single perforator. ## Dissection Steps 1. Positioning, markings, landmarks. - Position: supine with thighs adducted and hips internally rotated; secure feet to maintain rotation. - Landmarks: anterior superior iliac spine (ASIS) and superomedial patella border; draw the AP line connecting ASIS to superomedial patella. - Perforator mapping: - Mark midpoint of AP line (B point). Provisional AMT B-perforator location is on the midpoint and on average 3.2 cm medial to the AP line. A and C perforators lie ~5 cm proximal and distal to B, respectively, if present. - If preoperative imaging is used (CTA) it accurately predicts thigh perforator location and course relative to muscular anatomy and should be considered when peripheral vascular disease or complex multipaddle design is anticipated. - Skin island design: medial (AMT) territory lies directly medial to ALT territory; initial anterior incision typically planned 1.5–2 cm medial to AP line to permit exploration of ALT and AMT through same approach. 2. Plane and perforator identification. - Initial incision: make a straight anterior incision parallel to AP line ~1.5–2 cm medial; begin suprafascial dissection to explore ALT territory perforators first (this allows reciprocal planning). - Perforator identification: use handheld Doppler to localize signals at predicted B (and A/C) locations; assess perforator size, location (septocutaneous vs musculocutaneous), and intramuscular course. - If no adequate ALT perforator is found, extend dissection medially and enter intermuscular space between rectus femoris and sartorius/vastus medialis to identify AMT perforators. - Confirm origin: trace candidate AMT perforator proximally; clinically useful AMT perforators should connect to the rectus femoris branch of the descending LFCA (as opposed to short SFA perforators). 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Once a suitable AMT perforator is chosen, incise posterior border of skin island and elevate medially toward perforator. - For musculocutaneous perforators: perform careful intramuscular dissection through rectus femoris to the rectus femoris branch of the descending LFCA; avoid damage to the rectus femoris branch you intend to preserve. - For septocutaneous perforators: preserve plane in septum and skeletonize perforator along its subfascial course. - Pedicle skeletonization: trace perforator to its source (rectus femoris branch and then to common trunk where it arises from the descending LFCA/profunda origin) to gain pedicle length comparable to ALT. - Control and division: clip or ligate distal branches as needed; preserve LFCA branch to rectus femoris if possible; if nerve branches to vastus/rectus are divided, consider primary neurorrhaphy at closure if indicated. - Perfusion checks: clinical assessment of flap color, capillary refill, and bleeding from flap edge intraoperatively; if uncertain, consider leaving additional perforators or choosing ALT territory if available. - Transfer/inset: once pedicle is divided at planned point, transfer as pedicled flap (regional) or prepare for microvascular anastomosis (free) per reconstruction plan; design eccentrically around perforator to increase reach when needed. 4. Donor-site closure techniques. - Primary closure: possible when flap width ≤ 8–9 cm; conservative suprafascial undermining medially/laterally may facilitate tension-free closure. - Purse-string dermal plication (ALT technique applicable): absorbable running dermal 2–0 or 3–0 suture to reduce skin defect and potentially avoid grafting. - Drains: place closed-suction drain(s) in donor site — imperative to reduce seroma formation. - Skin grafting: required for wider defects; consider vacuum-assisted closure over graft interface when used. - Avoid overzealous tension to prevent muscle ischemia, soft tissue necrosis, or compartment syndrome. ## Indications and Contraindications - Indications: - Primary: used when ALT perforators are absent, inadequate, or when multipaddle design requires separate medial skin paddle; regional pedicled use possible for groin, mons, thigh, knee; free-flap use for head & neck, upper and lower extremity, and elsewhere where ALT is not feasible. - Specific scenarios: when reciprocal dominance favors AMT (i.e., absent/insufficient ALT perforators — near 100% chance AMT present), or when a second skin island is needed and only one ALT perforator is present (~75% chance an AMT perforator will be usable). - Tissue requirements: similar donor-site morbidity and cutaneous thickness to ALT; can be harvested as thin fasciocutaneous flap or myocutaneous inclusion of rectus femoris for added bulk/chimeric designs. - Contraindications: - Absolute/relative: - Perforators arising from SFA (short 3–5 cm) — generally not suitable (insufficient pedicle length). - Thigh subcutaneous fat >2 cm when a thin resurfacing flap is required — consider alternative donor sites. - Prior surgeries or scars in the medial thigh that interrupt vascular anatomy; prior harvest of adjacent thigh pedicles (evaluate preoperatively). - Peripheral vascular disease affecting donor limb — consider preoperative CTA or alternative donor site. - Technical limits: donor-site width >8–9 cm typically requires skin grafting, which may alter candidacy for some patients. ## Postoperative Care - Monitoring and drainage: - Routine placement of closed-suction drains at donor site is recommended; remove per usual drain criteria (not specified in sources). - Flap monitoring: clinical monitoring (color, capillary refill) is standard; specific monitoring schedules or implantable Doppler recommendations are not detailed in the provided sources. - Wound management: - If split-thickness graft used at donor site, consider vacuum-assisted closure over interface dressing (described for ALT donor management). - Positioning and mobilization: - Supine positioning is standard immediately post-op for most AMT harvests; mobilization and physiotherapy depend on reconstruction but specific timelines are not provided. - Antithrombotic practice / antibiotics / analgesia: - Not specifically described in the AMT or related chapters included. - Return-to-OR thresholds and time windows: - Not specifically detailed in the provided sources; re-exploration principles follow standard microsurgical and pedicled flap care (not specified here). ## Complications (rates & management) - Anatomical frequency data (relevant to planning; reported in sources): - 4.3% of thighs have no ALT perforators. - 26% of thighs have only one ALT perforator. - In thighs lacking ALT perforators, there is nearly a 100% chance an adequate AMT perforator is present. - In thighs with only one ALT perforator, ~75% have a usable AMT perforator. - AMT perforators arise from the rectus femoris branch in ~51% of thighs in series. - ALT perforators are musculocutaneous in ~80% of cases (for comparison when planning ALT vs AMT). - If AMT perforators arise from SFA they are short (3–5 cm) and more distal. - Donor-site primary closure usually possible for widths ≤ 8–9 cm (thresholds reported). - Reported flap- or donor-site complication rates: specific rates of venous congestion, arterial thrombosis, partial/total flap loss, infection, fat necrosis, seroma, hematoma, contour deformity, hernia/weakness are not quantified in the provided AMT chapter. - Management algorithms (as described or implied in sources): - If dominant ALT perforators are absent or inadequate intraoperatively, convert to AMT exploration via the same anterior incision rather than abandoning thigh donor site (reciprocal dominance principle). - If AMT perforators originate from SFA (short), do not rely on them for a long-pedicle flap; either convert to ALT/myocutaneous variant (include rectus femoris) or choose alternate donor site. - Donor-site seroma prevention: place closed-suction drains; consider limited undermining and layered closure; if seroma develops standard drainage and wound care recommended (specific algorithms not provided). - Avoid over-tight closure to prevent muscle ischemia and compartment syndrome — if closure is tight, revise to graft rather than tensioned primary closure. - Notes: Specific microsurgical salvage strategies (re-exploration timing, leeching, thrombolysis) are not described in the AMT chapter material provided. ## Key Clinical Pearls - Reciprocal dominance: always map both ALT and AMT territories preoperatively (handheld Doppler or CTA when indicated). If ALT perforators are absent or inadequate, AMT is very likely usable (near 100% when ALT absent). - Perforator mapping landmarks: - Draw AP line from ASIS to superomedial patella; B-perforator is at midpoint; AMT perforators average 3.2 cm medial to this line; A/C perforators ~5 cm proximal/distal to B (if present). - Incision strategy: initial anterior incision 1.5–2 cm medial to AP line allows exploration of ALT first and, if needed, AMT through the same approach — saves time and avoids separate exposure. - Useful origin criterion: clinically useful AMT perforators should trace to the rectus femoris branch of the descending LFCA; if they come from the superficial femoral artery (short, 3–5 cm), expect inadequate pedicle length. - Donor closure thresholds: design flap width ≤ 8–9 cm when primary closure is desired; plan for skin grafting if wider. - Preserve rectus femoris: attempt to preserve LFCA branch to rectus femoris where possible; if nerve branches to vastus/rectus are sacrificed and significant, consider primary repair during closure. - Preoperative imaging indications: use CTA when peripheral vascular disease or complex multipaddle planning is anticipated — CTA accurately predicts perforator location and course. - Avoid overzealous donor closure: do not force tension to avoid a skin graft — excessive closure can lead to muscle ischemia, necrosis, or compartment syndrome; drains and modest undermining are safer.