**Region:** Chest and Shoulders # Pectoralis Major Flap ## Anatomy - Pedicle: pectoral branch of the thoracoacromial artery (dominant). Mean arterial caliber: 2.0 mm; paired venae comitantes mean caliber: 3.0 mm; pedicle length to muscle entry ≈ 4 cm (effective reach can be increased by designing the skin paddle more distally) (Shokrollahi et al., Flaps ch.32). - Course: thoracoacromial trunk arises inferior to the middle third of the clavicle and divides into pectoral, clavicular, acromial and deltoid branches; the pectoral branch enters the deep surface of pectoralis major and supplies the muscle. The pectoral branch supplies small perforators to overlying skin but dissipates at about the level of the fourth rib (Hanasono et al.). - Secondary/segmental pedicles: internal mammary perforators (1st–6th interspaces) — mean arterial caliber 0.5–0.8 mm, venous comitantes 1.0–1.5 mm, length 1–2 cm; pectoral branch of lateral thoracic artery — arterial caliber 1–2 mm, venous 2.0–2.5 mm, length 3–4 cm; lateral perforators from 5th–7th anterior intercostal arteries — arterial calibre <0.5 mm, length 1–2 cm. These perforators anastomose with thoracoacromial system via choke vessels that permit reliable distal skin paddles when centered over intercostal perforators (Shokrollahi et al.; Hanasono et al.). - Important relationships: lateral thoracic vessels run lateral to thoracoacromial vessels; internal mammary perforators lie medially. Identification of the pedicle is best performed on the deep (undersurface) of the muscle early in dissection (Hanasono; Shokrollahi). - Nerves: motor — lateral and medial pectoral nerves. Lateral pectoral nerve (from lateral cord) enters the muscle on its deep surface approximately 3 cm medial to the medial pectoral nerve (Hanasono). The nerves are usually divided during harvest to prevent contraction and to maximize arc of rotation; flap is not typically harvested as a sensate flap. Sensory innervation to overlying skin is segmental from 2nd–7th intercostal nerves (Shokrollahi et al.). - Included tissues: muscle (sternocostal and clavicular heads); optional skin paddle (myocutaneous), possible osteomyocutaneous extension (fifth rib or lateral sternum) in specific variants. Skin paddle thickness variable (often bulky in obese patients and women); thinner skin paddle options include centering over internal mammary perforators (third interspace) or raising muscle-only with split/full-thickness graft coverage (Hanasono). Skin paddle reliably centered over fourth intercostal perforators for maximal reach; should not extend more than a few centimeters beyond muscle border (Hanasono). - Arc of rotation / variants: pedicled flap reaches lower face, neck, hypopharynx, sternal and thoracic defects; can be turned over (turnover flap) or advanced (myocutaneous advancement). Variations include osteomyocutaneous pectoralis (including ribs/clavicular bone), split-muscle flaps, double flaps (pectoralis and lateral thoracic–based), and designs harnessing internal mammary perforators for a more medial, thinner paddle (Hanasono; Shokrollahi). ## Dissection Steps 1. Positioning, markings, landmarks. - Position: supine with shoulder abducted to 90° and arm extended on an arm board. If planning midline advancement/closure, be prepared to adduct the arm during closure (Shokrollahi et al.). Mark sternal notch, xiphoid, midline chest, clavicle, coracoid process, and lateral axillary fold. Mark the course of pedicle by a line from coracoid to xiphoid or acromion to xiphoid as an estimate of thoracoacromial axis. Design skin paddle over lower medial muscle (center over 4th intercostal perforator for maximal reach; consider 3rd interspace medial design in obese/large-breasted patients) (Hanasono; Shokrollahi). 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Incision options: inframammary or along inferior border of pectoralis in men; oblique/paramedian or deltopectoral corridor for head & neck uses. When raising myocutaneous flap, incise skin island first and elevate surrounding skin off underlying muscle fascia. Do not undermine skin paddle excessively if relying on its perforators. Hand-held Doppler useful if designing a medial internal mammary–based skin paddle (Hanasono). - Dissection plane: elevate adipocutaneous flaps off muscle fascia (suprafascial) leaving skin paddle attached if myocutaneous flap planned; otherwise elevate overlying skin widely for turnover. Preserve musculocutaneous perforators to skin when intended; ligate (not cauterize) intercostal perforators that communicate with skin paddle during muscle elevation to avoid thermal injury (Hanasono). 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Identify the thoracoacromial pedicle on the deep surface of the muscle early and protect it. For turnover flaps: disinsert humeral attachment (divide tendon) to allow medial rotation into sternum/mediastinum. In situations where internal mammary perforators are preserved, medial myotomy can be placed to preserve their supply for advancement flaps (Shokrollahi). - When maximal arc required: skeletonize pedicle proximally, ligate lateral thoracic branches if they impede rotation, divide medial & lateral pectoral nerves. If needed, segmental ostectomy of middle third clavicle can lengthen and straighten pedicle path for head/neck inset (Shokrollahi; Shridharani). - Deliver muscle through a wide subcutaneous tunnel or midline sternotomy defect. For turnover into anterior mediastinum place a large drain/chest tube first to protect space; inset muscle to obliterate dead space and cover vital structures with absorbable sutures (Shokrollahi). Myocutaneous advancement: raise composite flap off chest wall and advance medially; confirm pedicle perfusion to skin paddle before final inset. - Perfusion checks: visual assessment of muscle/paddle colour and bleeding; preserve perforators and avoid cautery of musculocutaneous perforators to maintain skin paddle flow (Hanasono; Shokrollahi). (No implantable probe or monitoring schedule is specified in the sources.) 4. Donor-site closure techniques. - Close in multiple layers; place 19‑French round channeled drains (donor-site) and secure exit through separate stab incision. If donor site cannot be primarily closed (large skin paddle >5 cm or very long flap), perform split-thickness skin grafting; skin grafts over ribs/cartilage may heal slowly (Hanasono; Shokrollahi). Minimize proximal cuff of muscle around pedicle to reduce supraclavicular/neck bulk. ## Indications and Contraindications - Indications: - Head and neck: cutaneous neck/lower face defects, oral/oropharyngeal defects, hypopharyngeal reinforcement or patch, salvage after free flap loss (Ariyan/Hanasono/Shokrollahi). - Thoracic/sternal: sternal wound coverage, intrathoracic coverage (turnover for mediastinum), axillary/shoulder defects, pacemaker coverage. - Oral cavity/mandible reconstruction: osteomyocutaneous variant for mandibular defects when free transfer not feasible (Shokrollahi). - Choice considerations: muscle-only with skin graft for thin coverage; myocutaneous when skin required. Skin paddle placement affects thickness and reach (Hanasono; Shokrollahi). - Contraindications: - Disruption of dominant pedicle or perforators (e.g., prior ipsilateral thoracoacromial disruption or harvest of internal mammary perforators on that side) that would compromise vascularity — turnover flap contraindicated if internal mammary perforators are sacrificed and no alternative pedicle present (Shokrollahi). - Relative: large-breasted or obese patients where skin paddle is excessively bulky — consider muscle-only with skin graft or medial internal mammary–based paddle (Hanasono). Significant comorbidity limiting operative time may favor simpler local options but are not explicitly quantified in the sources. ## Postoperative Care - Monitoring and drains: - Place donor-site drains (19‑French round channeled) and, for mediastinal insets, an anterior mediastinal chest tube/large drain as described; remove per routine when outputs acceptable (Shokrollahi). No detailed numeric monitoring schedule provided in texts. - Positioning / mobilization: - For routine cases: supine recovery; progressive arm and shoulder movement is expected and important; for midline advancement closures be prepared to adduct the shoulder/arm for closure (Shokrollahi). Early progressive mobilization of shoulder encouraged (Shokrollahi notes necessity of progressive early postoperative arm and shoulder movement). - Wound coverage: - If muscle-only inset without skin, consider split-thickness grafting at the time of closure if no dermal coverage of inset muscle (Shokrollahi). - Analgesia / diet / antithrombotic practice: - Specific regimens not provided in the referenced chapters; follow institutional ERAS/analgesia and VTE prophylaxis protocols. - Return-to-OR thresholds/time windows: - The sources do not provide a numeric re-exploration window or criteria; re-exploration would be indicated for compromised perfusion of inset tissue, unresolving hematoma/infection, or exposed vital structures — manage per clinical judgment and institutional practice. ## Complications (rates & management) - Flap-related complications reported in literature referenced but percentages are not provided in the chapter extracts used here — therefore the following lists are descriptive (no rates given in the provided texts). - Venous congestion / arterial compromise: not specifically quantified; general principle — identify and protect pedicle during dissection; if suspected ischemia/venous congestion, urgent return to theatre for exploration and pedicle assessment is standard surgical practice (texts emphasize careful pedicle handling and early identification). The supplied chapters do not provide formal algorithms for leeching or thrombolysis. - Partial skin paddle loss / fat necrosis / bulkiness: skin paddle reliability depends on location — distal paddles rely on choke anastomoses; place paddle over 4th intercostal perforators for most reliable distal reach, or over 3rd intercostal internal mammary perforator for thinner paddle in women/obese patients (Hanasono). If donor-site closure tension or skin paddle necrosis occurs, consider grafting or local revision. - Infection / wound breakdown: addressed by adequate debridement (sternal debridement back to bleeding bone for sternal wounds), drains, and muscle inset to obliterate dead space (Shokrollahi). Chronic infection may require further debridement and flap revision. - Donor-site complications: - Seroma/hematoma and contour deformity discussed generally; specific frequencies are not presented in the pectoralis chapters. Closure in layers and placement of drains recommended; split-thickness grafting if primary closure not possible (Hanasono; Shokrollahi). - Management algorithms (as described in sources): - Preservation and early identification of pedicle on deep muscle surface to avoid inadvertent injury (Hanasono; Shokrollahi). - If pedicle tethering or insufficient reach: options include medial myotomy preserving internal mammary perforators (advancement), clavicular segmental ostectomy to increase arc, skeletonization of pedicle (intramuscular dissection) to thin pedicle and increase length — all described as maneuvers to increase reach (Shokrollahi; Shridharani). - If internal mammary perforators were harvested (e.g., prior CABG), turnover flap based on internal mammary is contraindicated; plan myocutaneous advancement or alternative flap (Shokrollahi). ## Key Clinical Pearls - For maximal distal reach of a PMMC myocutaneous flap center the skin paddle over the fourth intercostal perforators (reliable choke anastomoses to thoracoacromial pedicle) — consider third intercostal internal mammary perforator (superomedial paddle) in obese or large-breasted patients for a thinner flap (Hanasono). - Identify and protect the thoracoacromial/pectoral pedicle early on the deep surface of the muscle; skeletonize proximally if additional length is required (Hanasono; Shokrollahi). - Mean calibers and pedicle lengths to anticipate during dissection: pectoral branch ~2.0 mm artery with 3.0 mm venae comitantes; pedicle enters muscle ≈4 cm from surface entry — plan clamps/ligation and instruments accordingly (Shokrollahi). - Ligate musculocutaneous intercostal perforators rather than cauterize where they supply the chosen skin paddle to avoid thermal injury to paddle blood supply (Hanasono). - Divide medial and lateral pectoral nerves when maximal arc or to prevent muscle contraction; expect loss of some pectoralis function and inform the patient preoperatively (Shokrollahi; Hanasono). - When donor-site skin paddle >5 cm expect substantial undermining; if donor site cannot be closed primarily, be prepared for split-thickness grafting — skin grafts over costal cartilage may heal slowly (Hanasono; Shokrollahi). - In sternal/mediastinal reconstructions place a large drain/chest tube in anterior mediastinum prior to muscle inset to protect space and manage effusion/bleeding (Shokrollahi). - If additional arc is needed for head/neck inset consider segmental clavicular ostectomy in subperiosteal plane to avoid pedicle tethering; stabilize the resulting osseous defect with a spanning plate (Shokrollahi).