**Region:** Upper Extremity # Lateral Arm Flap ## Anatomy - Pedicle: posterior (posterior) radial collateral artery (branch of profunda brachii / deep artery of arm); accompanied by two venae comitantes. Reliable pedicle length ~7 cm; average arterial diameter ~1.7 mm and venous diameter ~2.5 mm (anatomical series quoted). The pedicle runs in the lateral intermuscular septum on the lateral border of the humerus and becomes more superficial toward the lateral epicondyle; small branches to the humerus permit osteocutaneous harvest (Hanasono; Neligan). - Course: origin from profunda brachii → radial collateral / posterior radial collateral branch → runs distally in the septum between biceps (anterior) / brachialis and triceps laterally → gives septocutaneous perforators to skin of lateral arm → anastomoses around elbow with radial recurrent vessels (Hanasono; Blondeel). - Perforator pattern: usually 1–3 septocutaneous perforators (termed A, B, C). Consistent perforators located approximately 7, 10, and 12 cm from the deltoid insertion along the line to the lateral epicondyle; perforators supply overlying skin and can be used to design a perforator or fasciocutaneous flap (Hanasono; Neligan). - Variants: bifurcation of radial collateral artery into anterior/posterior branches commonly located where the radial nerve passes through the lateral intermuscular septum (>50% in one series); absent anterior branch reported in ~21%; double posterior branches (two pedicles) ~8%. Radial nerve position varies and must be identified (Blondeel). - Nerves: - Lateral antebrachial cutaneous nerve commonly runs superficial to the pedicle and often requires division to mobilize the pedicle; can be harvested for a sensate flap if desired (Hanasono). - Posterior cutaneous nerve of the arm and posterior cutaneous nerve of the forearm (both derived from the radial nerve in the provided texts) lie in proximity to the pedicle; the posterior antebrachial cutaneous nerve often runs with the pedicle and passes ~2 cm anterior to the lateral epicondyle — may be preserved or included for sensate reconstruction (Blondeel; Neligan). - Radial nerve: courses in/through the lateral intermuscular septum (spiral groove → penetrates septum about 10 cm proximal to lateral epicondyle in described series); intimate relation to the anterior branch of the collateral vessels — radial nerve must be identified and protected during proximal pedicle dissection (Blondeel; Hanasono). - Numeric variant frequencies: posterior cutaneous nerve of the forearm absent in ~5%; posterior cutaneous nerve of the forearm arising from posterior cutaneous nerve of the arm reported ~5% (Blondeel). - Included tissues: skin, subcutaneous tissue, investing fascia; can be harvested as: - Fasciocutaneous or true perforator flap (skin ± fascia over septum). - Adipofascial/fascial flap (thin fascial flap + skin graft) for tendon glide. - Osteocutaneous flap including a segment of lateral humeral cortex. - Chimeric constructs including cuff of triceps muscle for bulk (Hanasono; Neligan). - Thickness / arc of rotation / common variants: - Tissue thickness: generally thinner than thigh flaps, slightly thicker than forearm-based flaps; can be tailored by choosing classical lateral arm (more proximal = thicker) versus lateral forearm/distal lateral arm (thinner) or extended designs combining both (extended lateral arm / lateral forearm flap gives thinner distal paddle and longer pedicle) (Hanasono; Neligan). - Arc of rotation: suitable for head & neck, upper extremity coverage; can be used pedicled for upper arm/shoulder/elbow (reverse designs based on recurrent vessels) or as a free flap. - Pedicle length extension: extended lateral forearm designs can increase pedicle length to >12 cm on average; case reports of pedicle lengths ~14 cm (Neligan). ## Dissection Steps 1. Positioning, markings, landmarks. - Position: supine; donor arm prepared circumferentially; donor arm often placed across torso on a single standard arm board (slight adduction, forearm pronated) to allow surgeon/assistant seating and mobility during harvest (Hanasono; Neligan). - Landmarks/marking: draw a line from deltoid insertion to lateral epicondyle → this approximates the lateral intermuscular septum and flap meridian. Perform pinch test to determine maximum width allowing primary closure (keep width ≤6 cm where primary closure is desired). Center skin paddle over one or more perforators (A, B, C at ~7, 10, 12 cm from deltoid insertion) (Hanasono; Neligan). - Tourniquet: optional; some prefer tourniquet for clearer dissection; if used, avoid complete exsanguination when distal pedicle visualization is needed (Quaba technique advises avoiding complete exsanguination for pedicled hand flaps; Neligan/Hanasono note tourniquet optional). 2. Plane (suprafascial/subfascial), perforator identification. - Initial posterior incision: incise posterior skin and dissect down to investing fascia of triceps; incise fascia and proceed in subfascial plane over triceps toward septum. Perforators should be visualized as dissection approaches lateral intermuscular septum (Hanasono; Neligan). - Perforator identification: visualize A/B/C perforators in septum and trace them to main posterior radial collateral pedicle. Doppler may be used to map perforators but experienced mapping relies on anatomical landmarks (Hanasono; Neligan). 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Trace perforators proximally through septum to main pedicle lying between biceps/brachialis and triceps. Clip and divide small vessels encountered rather than excessive electrocautery near nerve/pedicle. - Preserve lateral antebrachial cutaneous nerve until pedicle is freed; this exposes radial nerve — identify radial nerve before ligating any nerve branch. Use a no‑touch technique for pedicle; avoid traction or cautery on the radial nerve. The critical point is ~10 cm proximal to lateral epicondyle where radial nerve penetrates septum and the collateral artery often bifurcates; ligate anterior branch as indicated and continue proximal dissection to origin if additional length/caliber is required (release deltoid insertion if needed) (Hanasono; Neligan; Blondeel). - Distal control: ligate distal pedicle branches as flap is elevated from distal → proximal. If harvesting osteocutaneous, preserve small osseous branches to humerus. - Division and inset: divide pedicle after final clearance and ensure radial nerve protection. For pedicled/reverse designs, preserve appropriate recurrent anastomoses (radial recurrent / interosseous recurrent) depending on direction of flow (Neligan). - Perfusion checks: assess flap color, capillary refill; doppler may be used for free transfer monitoring (Neligan; Hanasono). 4. Donor-site closure techniques. - Inspect for hemostasis; place closed suction drain in donor site. Do not reapproximate lateral septal fascia tightly (avoid compression of radial nerve). Close skin in layers primarily when flap width permits (width typically ≤6 cm for direct closure); if larger skin paddle harvested, consider skin grafting — up to about half the upper arm circumference may be used and grafted (Hanasono; Neligan). - If extended flap included proximal forearm skin, donor closure may need additional releases or grafting; contour the scar to avoid prominent lateral arm deformity. ## Indications and Contraindications - Indications: - Pedicled coverage of upper arm and shoulder defects (axillary/shoulder/upper arm), pedicled or free transfer for elbow and forearm defects (Neligan; Hanasono). - Free flap reconstruction for head & neck defects (partial pharyngeal, floor of mouth, tongue, cheek), and for extremity coverage requiring thin, pliable tissue over exposed bone, tendon, nerve, or vessels (Hanasono; Neligan). - Fascial/adipofascial harvest for tendon gliding surfaces of the hand; osteocutaneous or chimeric constructs when bone/tendon required (Hanasono; Neligan). - Sensate reconstruction when posterior cutaneous nerve branches or lateral antebrachial cutaneous nerve are included. - Extended lateral forearm flap for longer pedicle and thinner distal skin paddle (Neligan). - Contraindications (absolute/relative as described in texts): - Local conditions that render the lateral intermuscular septum/pedicle unreliable (prior surgery or trauma that disrupts the posterior radial collateral vascular territory) — surgical judgment required (general caution in presence of local vascular compromise). - Obesity or inflammatory elbow disease (epicondylitis) may preclude practical use due to bulk or limited donor tissue mobility (Neligan). - Caution where radial nerve function is compromised; meticulous identification and protection of radial nerve required — preexisting radial nerve palsy changes operative planning (Blondeel; Hanasono). - Flap width >6 cm frequently precludes primary donor closure — need to plan for grafting or alternative donor (Neligan). ## Postoperative Care - Monitoring schedule/method: - Immediate and frequent clinical checks for flap perfusion (color, turgor, capillary refill) and continuous monitoring for donor arm hematoma/compartment issues. Handheld Doppler may be used for free-flap pedicle checks as available (Neligan; Hanasono). - Specific focus on radial nerve function and early recognition of new motor/sensory deficits — examine and document motor/sensory status frequently in the first 24–72 hours (Neligan). - Warming/positioning/splinting: - Positioning to avoid tension on pedicle; for pedicled transfers, ensure comfortable limb positioning and avoid compression. When used as pedicled elbow reconstruction, mobilize as per pedicle safety and surgeon preference. - Immobilization considerations for hand recipients follow usual protocols for inset type; keystone/locoregional references suggest short-term splinting (up to 1 week) when needed — for lateral arm-specific care, follow reconstruction-specific protocols (Hanasono; Keystone chapter general principles). - Drains: closed suction drain left in donor site; remove when output minimal per usual practice (texts recommend drain placement) (Hanasono). - Antithrombotic practice/diet/analgesia: not specified in source texts — follow institutional protocols. - Mobilization: early mobilization of noninvolved joints as permitted; avoid strenuous activity of donor arm until healing adequate. - Return-to-OR thresholds/time windows: - Any signs of pedicle compromise (rapid color change, loss of Doppler signal, tense hematoma, increasing pain or swelling suggesting compression) mandate immediate return to OR for exploration — texts emphasize early re-exploration for vascular or compressive causes (Hanasono; Neligan). - Donor-site hematoma with evolving radial nerve deficit → urgent evacuation. ## Complications (rates & management) - Types (reported and emphasized in texts): - Radial nerve injury or compression: serious concern due to close anatomical relation; can result from traction, cautery thermal injury, or hematoma compression. Prevention: no‑touch pedicle technique, meticulous hemostasis, avoid reapproximating septal fascia. Management: urgent exploration and hematoma evacuation if compression suspected; inspect pedicle and nerve integrity (Hanasono; Blondeel). - Donor-site wound issues: inability to primarily close when flap width >6 cm necessitates skin grafting; contour deformity or hypertrophic scarring on lateral arm possible. Management: grafting when required; staged revisions for contour (Hanasono; Neligan). - Flap failure/vascular thrombosis / congestion / partial loss: specific numeric frequencies not provided in the supplied texts. Management general principles (from authors’ operative guidance): early recognition, urgent re-exploration for suspected pedicle thrombosis or kinking (re-anastomosis or thrombectomy as indicated), evacuation of compressive hematoma; for venous congestion if recognized early, return to OR to assess venous outflow (Neligan; Hanasono). - Sensory deficits: numbness in distribution of sacrificed cutaneous nerves (lateral antebrachial cutaneous nerve/posterior cutaneous nerves) is common and usually well tolerated; may persist but often acceptable to patients (Hanasono; Neligan). - Donor-site hematoma/seroma/infection: histologic and clinical vigilance; drain placement and meticulous hemostasis recommended; evacuate hematoma promptly if suspected (Hanasono; Blondeel). - Fat necrosis / partial skin necrosis / wound dehiscence: standard flap wound complications — manage with local wound care, debridement, grafting as appropriate. - Reported rates: none of the supplied chapters provide consistent numeric complication rates for lateral arm flap series in the provided extracts; avoid inserting external rates. ## Key Clinical Pearls - Map the septum: draw a line from deltoid insertion to lateral epicondyle — A, B, C perforators are reliably at ~7, 10, and 12 cm from the deltoid insertion along this line (Hanasono). - Expect and protect the radial nerve: the radial nerve commonly penetrates the lateral intermuscular septum at ~10 cm proximal to the lateral epicondyle; identify it before ligating anterior branches — use a no‑touch technique around the nerve and pedicle (Blondeel; Hanasono). - Plan donor closure: keep flap width ≤6 cm where primary donor closure is required; otherwise plan for local releases or skin grafting (Neligan). - Preserve/harvest sensory nerves intentionally: lateral antebrachial cutaneous nerve or posterior cutaneous nerve branches can be preserved for a sensate flap or included as a vascularized nerve graft if required — otherwise preserve them when not needed to minimize numbness (Hanasono; Blondeel). - Deltoid insertion release for length: partial release of the deltoid insertion will increase pedicle exposure, length and caliber when extra reach is needed (Hanasono). - Avoid tight reapproximation of the septal fascia: do not reapproximate the septal fascia between biceps and triceps — this can compress the radial nerve (Hanasono). - Extended lateral forearm option: to obtain a longer pedicle and thinner distal skin paddle, plan an extended lateral arm → proximal forearm design (lateral forearm flap); pedicle length commonly increases to >12 cm (Neligan). - Hemostasis and drains: meticulous hemostasis is mandatory to avoid postoperative hematoma and potential radial nerve compression — place a closed suction drain and inspect the donor site before closure (Blondeel; Hanasono).