**Region:** Lower Extremity # Sural Artery Flap ## Anatomy - Pedicle: - Named artery and venae comitantes: superficial sural artery (axial component along sural nerve) with retrograde perfusion via septocutaneous perforators from the peroneal (fibular) artery; venous drainage via the superficial sural vein/lesser saphenous vein and peroneal venae comitantes (Shaterian; Hanasono; Shridharani). - Typical vessel calibers/lengths (reported): - Medial sural artery pedicle (proximally based sural flap): ~1.4 mm diameter; pedicle length ~4–6 cm reported for the medial sural pedicle (Hanasono). - Peroneal (fibular) artery perforators: mean arterial caliber <1.5 mm (text summary) and reported peroneal perforator diameters ~0.8 ± 0.3 mm with 5 ± 2 perforators in the lateral leg territory (Blondeel). - Course: - Superficial sural vessels run in the subfascial/deep subcutaneous plane along with the sural nerve from the mid-posterior calf to the lower leg; perforators from the peroneal artery anastomose with the superficial sural axis in the distal tibiofibular region and provide retrograde arterial inflow when the flap is raised distally based (Masquelet / Shaterian; Hanasono). - A constant distal anastomosis / pivot-perforator is typically located ~4–5 cm proximal to the tip of the lateral malleolus (multiple sources: 5 cm / three fingerbreadths proximal to lateral malleolus) — preserve this as the vascular pivot (Shaterian; Hanasono; Shridharani). - Perforator pattern: - Dominant supply to reverse sural flap is through septocutaneous perforators from the peroneal artery that anastomose with the superficial sural axis. - Typical number/location: four to eight peroneal perforators in the lower leg territory; large perforator(s) consistently located approximately 4–7 cm proximal to the lateral malleolus (Shridharani; Shaterian; Blondeel). - Perforator superficial length: variable; peroneal perforators run through septum and have superficial pedicle length on the order of few centimeters (Blondeel). - Choke vessels / adjacent angiosomes: - The flap depends on anastomotic chains between the peroneal perforators and the superficial sural artery; choke/anastomotic vessels allow retrograde flow but limit maximal safe length; flap reliability decreases with more distal pivot points (Taylor angiosome concept; Masquelet; Blondeel). - Nerves: - Sural nerve (medial and lateral sural cutaneous components) accompanies the superficial sural artery and the lesser saphenous vein in the pedicle — usually included in the fasciocutaneous pedicle (sensate flap option) (Hanasono; Shaterian; Shridharani). - Posterior femoral cutaneous nerve may be encountered in proximal dissections in popliteal fossa when raising proximally based variants (Shridharani). - Expected sequela: sensory loss over donor site and lateral foot common due to sural nerve sacrifice (Shaterian). - Included tissues: - Components: skin, subcutaneous fat, deep fascia (fasciocutaneous), sural nerve, lesser saphenous vein, superficial sural artery; adipofascial variants (islanded adipofascial pedicle + skin graft) are described (Hanasono; Shaterian; Shridharani). - Thickness profile: typically thin-to-moderate; can be harvested as adipofascial (thinner) or full fasciocutaneous skin island (thicker). Adipofascial harvest allows skin graft over pedicle base and reduces bulk for foot/ankle reconstructions (Hanasono; Shridharani). - Arc of rotation: up to 180° rotation on distal pivot (Hanasono). Arc limited by pedicle length and avoidance of kinking at pivot; longer pedicle/dissection into popliteal fossa increases reach (Shridharani). - Common variants/anomalies: - Fasciocutaneous pedicle vs adipofascial pedicle; delayed two-stage elevation; supercharged (venous anastomosis) modifications; proximally based sural (anterograde) flap and free peroneal perforator–based variations (Hanasono; Shridharani; Shaterian). - Provide numbers only if present in the attached PDFs: - Typical distal perforator cluster: 2–5 perforators located 5–7 cm proximal to lateral malleolus (Masquelet / Shaterian). - Flap maximal dimensions often reported: up to 15 cm length × 12 cm width; reliable length-to-width ratio of pedicle ~4:1 (Shaterian). - Pedicle/adipofascial cuff: commonly 2–3 cm on either side of nerve/vessels during dissection; some authors recommend pedicle width ≥4 cm to improve venous outflow (Hanasono; Shaterian). - Expected donor-site closure: primary closure feasible when flap width <3 cm (Hanasono; Shridharani). - Outcomes: meta-analysis reported 82% of reverse sural artery flaps heal without flap-related complications (Shaterian). ## Dissection Steps 1. Positioning, markings, landmarks. - Position: prone is standard; lateral decubitus or supine with the limb free are acceptable depending on defect location (prone best for heel/Achilles; lateral for anterior/lateral ankle) (Shaterian; Shridharani). - Landmarks/axis: - Draw line from midpopliteal point to midpoint between lateral malleolus and lateral border of Achilles tendon — this defines vascular axis of flap (Hanasono; Shridharani). - Mark pivot point: place at ~5 cm proximal to tip of lateral malleolus (three fingerbreadths) — corresponds to most distal peroneal perforator anastomosis with superficial sural artery (Hanasono; Shaterian; Shridharani). - Map lesser saphenous vein and peroneal perforators with a handheld Doppler preop (Shaterian; Shridharani; Hanasono). - Template recipient defect and center on axis; ensure proximal flap limit does not extend proximal to junction of gastrocnemius heads (Hanasono; Shridharani). 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Elevation plane: subfascial (deep fascia included) elevation of skin island is the standard; adipofascial pedicle includes deep fascia and subcutaneous cuff without skin along pedicle for islanded transfers (Hanasono; Shridharani). - Perforator identification: - Confirm pivot perforator(s) and trace axis with handheld Doppler; identify lesser saphenous vein as axis guide (Shaterian; Shridharani). - Dissect subdermal/subfascial plane to expose sural nerve, superficial sural vessels and lesser saphenous vein at proximal margin prior to division in single-stage or as part of delay strategy (Hanasono). 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Initial incision: incise along marked skin paddle and along pedicle axis; elevate proximally to distally in subfascial plane (Shirdharani; Hanasono). - Identify and preserve the sural nerve, superficial sural artery, sural vein and lesser saphenous vein within pedicle. Include adipofascial cuff ~2–3 cm each side of nerve/vessels; maintain pedicle width — authors recommend at least 2–3 cm; consider 4 cm if venous drainage is a concern (Shaterian; Hanasono; Shridharani). - At proximal margin of flap: ligate and divide proximal sural nerve and vessels when elevating as distally based/ islanded flap (Hanasono; Shaterian). - Continue elevation distally to pivot point, carefully freeing pedicle (do not skeletonize beyond safety — preserve cuff to reduce venous compromise) (Shridharani). - Division/transfer: - Mobilize pedicle at pivot point and transpose flap to recipient site via wide subcutaneous tunnel or by excising skin bridge; incise skin bridge if tunnel constrictive to avoid pedicle compression (Shaterian; Hanasono). - Avoid excessive rotation/torsion and kinking at pivot; longer pedicle or more proximal dissection (into popliteal fossa) increases reach but increases complexity (Shridharani). - Perfusion checks: - Clinical assessment (color, capillary refill) is primary. Doppler to confirm flow along lesser saphenous if available (Hanasono; Shaterian). - Consider supercharging (venous anastomosis) or exteriorization of the proximal lesser saphenous vein if congestion observed or in high-risk reconstructions (Shaterian). 4. Donor-site closure techniques. - Primary closure possible when flap width <3–4 cm; larger defects require split-thickness skin grafting (Hanasono; Shridharani). - Skin graft pedicle base if skin bridge left open for pedicle; place drains in donor site as needed (Shridharani). - Apply nonadherent dressings and well-padded posterior splint with window for flap monitoring (Shaterian). ## Indications and Contraindications - Indications: - Soft-tissue defects of distal third of leg: posterior heel and Achilles tendon, anterior and lateral ankle, dorsum of foot, lateral hindfoot, anterior crest of lower third of leg (Shaterian; Hanasono; Shridharani). - Moderate-size defects where thin pliable tissue needed and free flap risk is high; useful for coverage of exposed tendon, hardware, bone (Shaterian; Hanasono). - Flap size reach: reported up to 15 × 12 cm; primary donor closure when width <3 cm (Shaterian; Hanasono). - Sensate reconstruction: include sural nerve for neurosensory flap when indicated (Hanasono). - Variants: delayed flap for vascular comorbidity; supercharged flap (venous anastomosis) for problematic venous drainage; free peroneal-perforator or medial sural perforator free flap variants for alternate needs (Hanasono; Shaterian). - Contraindications: - Absolute: absence/occlusion of the peroneal artery in many centers (most consider peroneal artery occlusion to preclude reverse sural flap) (Shaterian). - Relative: peripheral arterial disease, diabetes mellitus, venous insufficiency, prior surgery or scarring in pedicle path, heavy smoking, severe lower-extremity edema — all increase flap necrosis risk; these patients commonly recommended for staged delay or alternative reconstructions (Shaterian; Hanasono; Shridharani). - Occluded anterior or posterior tibial artery is not absolute contraindication, but caution advised (Shaterian). ## Postoperative Care - Monitoring schedule/method: - Immediate clinical monitoring: frequent visual checks of flap color, turgor, capillary refill; use audible handheld Doppler on lesser saphenous/superficial sural pedicle as adjunct (Hanasono; Shaterian). - Keep window in posterior splint for direct monitoring; many groups remove dressings at 5–7 days for full assessment of flap and graft viability (Shaterian). - Implantable Doppler or continuous monitoring not specifically detailed in provided texts; use clinical plus Doppler as described in the sources. - Warming/antithrombotic practice: - Strict limb elevation and avoidance of direct pressure on flap for immediate postop period (first 5 days emphasized). Antithrombotic protocols not standardized in provided PDFs — follow institutional protocols (Shaterian). - Positioning/splinting: - Posterior padded plaster splint with window for monitoring; strict elevation for first 5 days; prolonged splinting beyond first week discouraged unless orthopedic needs dictate (Shaterian). - Drains: - Place small closed-suction drain in donor defect if large; skin graft donor sites managed per standard practice (Shridharani). - Mobilization, diet/analgesia: - Non–weight-bearing for 1–2 weeks; restricted weight-bearing for 4–6 weeks until flap healed (Shaterian). - Standard analgesia and diet per perioperative protocols (not specified in texts). - Return-to-OR thresholds and time windows: - Early re-exploration indicated with signs of arterial insufficiency or progressive congestion not responding to bedside measures — sooner rather than later (first 24 hours favored in microsurgical practice; specific time windows not numerically specified in provided PDFs). - Venous congestion management window: attempts at bedside measures (release skin bridge, remove constricting dressings, elevate limb) followed by leech therapy or operative venous supercharging/exteriorization if persistent (Shaterian). ## Complications (rates & management) - Frequencies (from attached sources): - Overall: meta-analysis reported 82% of flaps heal without flap-related complications — implies overall flap complication incidence ~18% (Shaterian). - Patients with vascular comorbidities (diabetes, venous insufficiency, PAD) show a 5–6× increase in complication rate compared with healthier patients (Shaterian). - Age >40 associated with higher failure risk in literature syntheses (Shaterian). - Common complications and reported management: - Venous congestion: - Common failure mechanism. Prevention: wider pedicle (≥4 cm recommended in some series), delayed elevation in high-risk patients, avoid skin bridge constriction, consider supercharged venous anastomosis (Shaterian; Hanasono). - Management: urgent assessment; release constricting tissue (open tunnel or skin bridge), leech therapy for superficial venous congestion, exteriorize proximal segment of lesser saphenous vein for intermittent drainage, or perform microsurgical venous anastomosis (supercharge) to recipient vein if available (Shaterian). - Arterial thrombosis / ischemia: - Presents with pallor, coolness, absent Doppler signal — requires immediate return to OR for pedicle exploration and revision. - Partial/total flap necrosis: - Variable rates reported in literature; manage conservatively for small necrosis with debridement and regrafting; larger areas may require reoperation or alternate flap (sources report ranges but not a single pooled percentage in provided PDFs). - Infection, hematoma, delayed healing, wound dehiscence, skin graft loss: standard management — antibiotics, operative drainage, debridement, regrafting as needed (Shaterian; Hanasono). - Donor-site complications: - Sensory loss over donor site and lateral foot (expected). - Need for skin graft and scar contour deformity common when flap width >3–4 cm; donor-site primary closure usually possible for widths <3 cm (Hanasono; Shridharani). - Seroma/hematoma: place drains and evacuate if required. - Management algorithms (what, when, how): - Suspected arterial insufficiency: immediate return to OR for pedicle exploration and revision of arterial inflow (standard operative urgency — no precise hour-window specified in provided PDFs). - Progressive venous congestion despite bedside measures: consider leech therapy short-term; if persistent, perform venous supercharging (microanastomosis of proximal lesser saphenous vein to recipient vein) or exteriorize proximal vein for controlled drainage; if necessary, re-explore pedicle to release constriction or revise pedicle design (Shaterian). - Delayed flap: 1–2 week staged elevation described to improve longitudinal blood flow in high-risk patients (Shaterian). - Supercharged flap: microsurgical augmentation by anastomosing the proximal lesser saphenous vein to recipient site vein to improve outflow (Shaterian). ## Key Clinical Pearls - Mark the pivot point at ~5 cm (three fingerbreadths) proximal to the tip of the lateral malleolus — this reliably corresponds to the distal peroneal perforator/pivot (Hanasono; Shaterian). - Preop Doppler mapping of peroneal perforators and lesser saphenous vein is essential — confirm pivot/perforator and axis before incision (Shaterian; Shridharani). - Maintain a pedicle adipofascial cuff; avoid skeletonization — include at least 2–3 cm width of soft tissue around nerve/vessels; consider ≥4 cm pedicle width when venous drainage is a concern (Hanasono; Shaterian). - Avoid acute kinking/torsion at pivot — a longer pedicle or further proximal dissection into popliteal fossa increases reach while minimizing tension (Shridharani). - If tunnel is tight, incise the skin bridge rather than forcing the pedicle through — closure of skin bridge can be done secondarily or pedicle skin-grafted (Hanasono; Shaterian). - Use a staged delay in patients with vascular comorbidity (smoking, diabetes, PAD, severe edema, age >70/older) — raise flap subfascially without dividing proximal skin for 1–2 weeks to augment longitudinal perfusion before final transfer (Shaterian; Hanasono). - If venous congestion is anticipated or observed, plan for venous augmentation: widen pedicle, consider venous supercharging to a recipient vein or exteriorize the proximal lesser saphenous vein for temporary drainage (Shaterian). - Donor-site planning: keep flap width ≤3 cm for primary closure when possible; otherwise prepare for split-thickness graft and counsel patient about expected sural nerve-related sensory loss and donor scar (Hanasono).