**Region:** Chest and Shoulders # Serratus Anterior Flap ## Anatomy - Pedicle: codominant vascular supply. - Lateral thoracic artery (branch of the axillary artery) supplies the superior portion of the muscle; accompanies a single vein. - Serratus branches of the thoracodorsal artery (originating from the subscapular/thoracodorsal system) supply the inferior slips; the thoracodorsal gives a single serratus branch that divides into 2–5 smaller branches before entering the latissimus dorsi region. These arteries are posterior on the thorax relative to the lateral thoracic pedicle. - Course: serratus branches arise from the thoracodorsal system and travel to the lateral chest wall to supply individual rib-based slips; lateral thoracic artery runs anterolaterally on the superficial surface of the muscle. - Pedicle length/diameter facts (operative relevance): - Typical island free-flap pedicle length when harvested on serratus branches: maximal pedicle length 6–8 cm. - If thoracodorsal and subscapular vessels are included (dissected proximally), a pedicle up to ~15 cm can be obtained. - Perforator pattern: - Each leaflet/slip of serratus anterior arises from a separate rib (first eight or nine ribs). - Muscle slips are supplied segmentally; the thoracodorsal serratus branch divides into multiple branchlets that supply the lower slips (commonly 3–5 slips used for flap harvest). - Skin perforators suitable for a skin paddle are frequently musculocutaneous from intercostal sources and often do not communicate with the serratus branch; therefore skin island reliability is variable. - Angiosomes/cross-flow: - The serratus flap is a Mathes and Nahai type III muscle (two dominant pedicles — lateral thoracic and serratus branches of thoracodorsal). Adjacent intercostal perforators and collateral branches exist; reliance on single perforator for a skin paddle is less predictable. - Nerves: - Motor: long thoracic nerve (C5–C7) innervates serratus anterior slips; courses on the superficial surface of the muscle and joins the thoracodorsal pedicle regionally (at approximately the level of the fifth or sixth rib). - Sensory (to overlying skin): segmental intercostal nerves (T2–T4) supply cutaneous sensation over the lateral chest. - Included tissues: - Muscle: individual slips (leaflets) of serratus anterior (thin, broad muscle on lateral chest wall). Typical harvest includes the lower three to five slips for most reconstructions. - Fascia-only (serratus fascia) can be harvested when thin pliable coverage is required. - Composite options: myo‑osseous flap including the fifth or sixth rib (rib left attached to the muscle slip), or inclusion of the scapular tip via the angular branch (osteoflap). - Skin paddle: possible but challenging — skin perforators are often intercostal in origin (variable), and skin design may be bulky in obese patients or distorted by the lateral breast in women. - Thickness/arc of rotation: thin, pliable tissue suitable for small-to-medium defects; pedicled arc reaches chest wall, shoulder, axilla and intrathoracic defects; free transfer can reach distant sites. Typical free-flap harvest size reported as up to 20 × 15 cm (more commonly the size of the patient’s palm). - Common variants/anomalies: - Fascia-only serratus flap (preserve long thoracic nerve). - Myo‑osseous serratus–rib flap (5th or 6th rib most commonly). - Composite latissimus–serratus chimeric flap on the thoracodorsal pedicle. - Scapular-tip inclusion via the angular branch (variable origin: angular arises from thoracodorsal or from a serratus branch). ## Dissection Steps 1. Positioning, markings, landmarks. - Patient: lateral decubitus (complete lateral or “sloppy lateral”) with affected side up; place beanbag and axillary roll. Prep entire ipsilateral upper extremity into field to permit intraoperative changes in arm position. - Landmarks: - Anterior border of latissimus dorsi (posterior axillary line) and lateral border of pectoralis major (anterior axillary line). - Tip of scapula (posterior border of serratus), costal margin, planned rib level (5th–6th if rib planned). - If skin paddle planned: use handheld Doppler (or CT angiography if available) to mark perforators in region of interest; expect perforators often 1.5–6.5 cm lateral to midline and within the medial half of rectus territory above the mid‑xiphoid–umbilicus horizontal in similar territories (note: those specific metric locations were reported for epigastric perforators; with serratus, expect variability and typical skin perforators to be intercostal in origin). - Incision options: oblique lateral chest wall incision or vertical incision between latissimus and pectoralis major. 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Dissect through subcutaneous tissue to expose thin serratus fascia and muscle surface. If harvesting fascia-only, perform suprafascial dissection and identify vascular perforators. - Identify the latissimus dorsi lateral edge and elevate partially to visualize serratus superficial surface and the location of vascular pedicles and long thoracic nerve. - Use handheld Doppler pre- and intraoperatively when planning a skin paddle; be aware many skin perforators are intercostal and may not communicate with serratus pedicle. 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Identify the vascular pedicles early — the lateral thoracic artery runs on the anterolateral superficial surface (supplies upper slips), and the serratus branches arise from the thoracodorsal artery posteriorly (supply lower slips). Preserve both when planning codominant harvest as needed. - For a standard serratus flap based on thoracodorsal serratus branches: - Identify and isolate the serratus branch(es) arising from thoracodorsal pedicle. - Harvest the lower three to five muscle slips; detach slips from their rib origins anterior→posterior, leaving attachments intact if including rib. - If rib included: leave muscle attachment to the selected rib (5th or 6th) and perform careful subperiosteal elevation/osteotomy of rib; protect parietal pleura. - To increase pedicle length for free transfer: dissect proximally on the thoracodorsal/subscapular system; including thoracodorsal + subscapular vessels can yield a pedicle approaching ~15 cm. - Nerve management: - Identify the long thoracic nerve where it courses with/near the thoracodorsal pedicle (joins at ~5th–6th rib level). Preserve motor branches to slips retained; divide the long thoracic nerve only at the superior limit of the harvest when needed (and if functional loss is acceptable). Preserve at least three to four slips (and their innervation) to avoid scapular winging. - Free-flap specifics: - Typical free flap size up to ~20 × 15 cm (commonly palm-sized). Expect pedicle length of 6–8 cm on native serratus branches unless subscapular/thoracodorsal included. - Verify flap perfusion before division (capillary refill, bleeding edges); take a slightly longer pedicle than strictly necessary to avoid tension/torsion at inset. - Pedicled/intrathoracic inset: - May require removal of one to two ribs to create window and prevent pedicle compression when passing the flap into the thorax. - Consider the lung in inflated state — inset should account for potential compression/stretch after reinflation. 4. Donor-site closure techniques. - Primary closure is usually possible; even with a small skin paddle the lateral chest donor site typically closes without tension. - Place closed-suction drains to manage dead space. - If rib harvested, single rib defect generally acceptable with minimal morbidity. - Avoid skin grafting of donor site if possible; when required, ensure adequate bed (no exposed rib/fascia) for graft take. - Quilting/progressive tension sutures and drains are recommended to minimize seroma formation. ## Indications and Contraindications - Indications: - Intrathoracic defects after tumor resection, repair of tracheoesophageal or bronchopleural fistula, coverage for bronchopleural defects. - Chest wall and xiphoid/epigastric region coverage. - Breast reconstruction for partial defects and chest wall defects (pedicled). - Axillary defects and regional coverage of shoulder/upper chest. - Oro‑mandibular, maxillary, and orbital floor reconstruction as alternative to free fibula in select cases (when myo‑osseous rib or scapular-tip composite needed). - Thin pliable coverage for small–medium extremity defects (free transfer) — dorsal hand/foot coverage with fascia-only option. - Free functional muscle transfer (facial reanimation), using long thoracic nerve for neurotization. - Patients with peripheral vascular disease who cannot undergo lower-extremity donor-site harvest (serratus–rib can substitute for osseous reconstruction). - Contraindications: - The serratus flap is not optimal when a reliable skin paddle is required in obese patients or in women with lateral breast tissue (skin paddle design is challenging and may be bulky; consider alternate flaps). - When preservation of serratus motor function is mandatory and harvesting would require sacrificing multiple slips or their innervation (risk of scapular winging). - Extensive prior surgery or scarring in the lateral chest that has compromised serratus vascular branches (relative contraindication—assess intraoperatively). - Absence or injury of donor pedicle (thoracodorsal/ lateral thoracic) or long thoracic nerve in ways that preclude safe harvest should be considered on a case-by-case basis. ## Postoperative Care - Monitoring schedule/method: - Treat free serratus transfers as microsurgical flaps — vigilant monitoring of flap color, turgor, capillary refill, and bleeding from a pinprick. - Avoid tight dressings; postoperative swelling may compress the pedicle. - For inseted pedicled flaps, monitor for signs of pedicle compression at tunnels/windows. - Warming/positioning: - Avoid external compression of the pedicle; ensure the arm and chest are positioned to avoid stretch or kink of the pedicle. - When involving intrathoracic inset, avoid excessive respiratory or positional stresses on the pedicle during early reinflation and chest physiotherapy. - Antithrombotic practice: - No specific protocol is prescribed within the source text for anticoagulation; standard institutional microvascular thrombosis prophylaxis may be applied per microsurgical protocols. - Drains/mobilization: - Place closed-suction drains in donor site; remove when output acceptable. (Related chest wall flap experience suggests drain removal when output is low and clinically acceptable.) - Early mobilization permitted; restrict heavy use of ipsilateral arm/shoulder until wound and neurovascular healing is secure. Preserve shoulder function by maintaining slips/innervation where possible. - Diet/analgesia: - Standard postoperative analgesia and diet as per reconstructed site and institutional protocols. - Return-to-OR thresholds and time windows: - Any sign of flap ischemia (progressive pallor, loss of capillary refill, increasing congestion) in a free flap calls for urgent re-exploration per microsurgical principles — treat serratus free flaps the same as other free flaps. - For pedicled flaps, signs of compromised perfusion or compression at the pedicle tunnel warrant immediate assessment and revision. ## Complications (rates & management) - Flap-specific complications (reported considerations; numerical rates not provided in source): - Partial flap loss/necrosis: related to unreliable skin perforators when skin paddle chosen; minimize by preoperative Doppler/CT angiography and intraoperative confirmation of perforator adequacy. - Venous congestion/arterial compromise: manage as for other muscle or perforator free flaps — urgent return to the operating room for exploration and salvage when clinical signs indicate compromised inflow or outflow. - Fat necrosis/infection: standard wound-care and debridement as indicated. - Donor-site complications: - Seroma/hematoma: place drains; manage postoperative seroma with aspiration and compression; refractory seromas may require operative capsule excision and re-closure. - Contour deformity: possible but typically modest with primary closure. - Scapular winging/weakness: risk if insufficient slips/innervation are preserved; preserve at least three to four slips and their motor innervation to avoid winging. - Pleural injury/pneumothorax when including ribs: avoid by careful subperiosteal dissection; if pleural breach occurs, treat per thoracic surgery/standard chest-tube management. - Management algorithms: - Vascular compromise (free flap): urgent re-exploration — inspect anastomoses, relieve kinks/twists, revise thrombosed vessel, consider systemic/local thrombolysis per institutional microsurgical protocols if indicated (these are general microsurgical rescue steps referenced by microvascular practice in the source texts). - Venous congestion without technical anastomosis problem: consider immediate revision of inset, relieve compression, leech therapy only when indicated and after specialist consultation (not specifically detailed in the source). - Donor-site seroma: needle aspiration and compression; if recurrent, operative drainage and capsule excision. ## Key Clinical Pearls - Identify and protect both codominant pedicles early: lateral thoracic artery (superior slips) and serratus branches of the thoracodorsal system (inferior slips); both lie superficially on the muscle surface. - Preserve the long thoracic nerve branches to slips retained; the nerve commonly joins the thoracodorsal pedicle at about the fifth or sixth rib — to avoid scapular winging, maintain at least three to four innervated slips. - Typical harvest: lower three to five slips for most serratus flaps; include the 5th or 6th rib for a myo‑osseous flap when bony reconstruction is required. - Expect native serratus branch pedicle length ~6–8 cm for free flap; if additional length is necessary, dissect proximally to include thoracodorsal/subscapular vessels to achieve pedicle lengths approaching ~15 cm. - Skin paddle reliability is variable: use handheld Doppler or CT angiography preoperatively and be cautious designing skin islands in obese patients or women with lateral breast tissue. - When using intrathoracic or pedicled inset, remove 1–2 ribs to create a non-compressive window and account for lung reinflation to prevent pedicle stretch or compression. - Fascia-only serratus flaps are ideal for thin, pliable coverage (dorsal hand/foot); harvest the fascia suprafascially and preserve the long thoracic nerve. - Use closed-suction drains and consider quilting/progressive tension closure to minimize donor-site seroma; primary closure is usually possible and preferable.