**Region:** Chest and Shoulders # Intercostal Artery Flap ## Anatomy - Pedicle: named artery (typical diameter/length if present), venae comitantes; course from origin to flap/skin paddle; perforator pattern (number, location, intramuscular vs septocutaneous), choke vessels/adjacent angiosomes. - Source arteries - Posterior intercostal arteries (paired branches from descending aorta) supply intercostal spaces 3–11 via posterior branches; subcostal artery corresponds to T12 (see Intercostal Artery Perforator Flaps). (38 Intercostal Artery Perforator Flaps) - Anterior intercostal branches arise from the internal thoracic artery (spaces 1–6) and the musculophrenic (≈7–9); anterior branches anastomose with posterior intercostals anteromedially. (Angiosomes of the Torso; Intercostal chapter) - Internal mammary (internal thoracic) artery and its perforators (IMAP) run ~1.5 cm lateral to the sternal border; dominant IMAP usually in the second intercostal space. Mean IMAP perforator diameters reported: 1st space ~1.50 mm (range 1.0–2.2 mm), 2nd ~1.83 mm (1.3–2.4 mm), 3rd ~1.47 mm (1.3–1.7 mm). Clinical IMAP arteries at 2nd space ≈1–1.5 mm; perforator veins ≈1.5–2 mm. (10 Internal Mammary Artery Perforator Flap) - Course and segments (posterior intercostal) - Vertebral segment: aorta → posterior angle of rib; gives dorsal (medial/lateral), nutrient (to rib), and collateral branches. Dorsal branches supply erector spinae and overlying skin. (38) - Costal groove segment: travels in costal groove to midaxillary line (~12 cm); gives dorsolateral musculocutaneous and lateral cutaneous branches that perforate in midaxillary/midscapular regions. (38) - Intermuscular segment: between transversus abdominis and internal oblique; musculocutaneous branches; variable length. (38) - Rectus segment: through rectus abdominis posteriorly, anastomoses with superior/inferior epigastric systems and supplies musculocutaneous perforators to anterior abdomen. (38) - Perforator pattern and typical locations - Dorsal branches: medial branches usually 1–5 cm from midline; lateral branches ~5–8 cm from midline posterior. (38) - Dorsolateral perforators (DLICAP): cluster near midscapular line (~10–12 cm from midline), commonly in lower thoracic spaces (8–11). (38) - Lateral intercostal perforators (LICAP): emerge at the midaxillary line, often dominant in 4th–6th spaces for lateral-breast applications; a dominant lateral perforator present in ~94% and most located in 5th–8th spaces in series cited. (38) - Anterior intercostal perforators (AICAP / IMAP overlap): strongest in 2nd–4th interspaces; internal thoracic perforators form important cutaneous supply medial to sternum and toward nipple region. (10; 38; Angiosomes) - Subcostal perforator (SCAP): consistent perforator near the anterior border of latissimus/external oblique inferior to 12th rib; source artery mean diameter ~2 mm; territory covers subcostal/lumbar skin. (38) - Intramuscular vs septocutaneous - On the torso most perforators are musculocutaneous (pass through muscle), fewer are septocutaneous; course must be traced through muscle layers when dissecting. (Angiosomes; 38) - Angiosomes / choke vessels / neighboring territories - Posterior intercostal angiosome spans back and lateral trunk; typical skin territory width ~4 intercostal spaces; rich choke/true anastomoses exist between intercostal levels and with internal thoracic, lateral thoracic, thoracodorsal systems allowing capture of adjacent territories (delay phenomenon applies). (Angiosomes Chapter) - Internal thoracic (IMAP) perforators dominantly supply chest skin (esp. 2nd–4th ICS) and anastomose with thoracoacromial and lateral thoracic systems. (IMAP; Angiosomes) - Nerves: sensory and motor branches relevant to flap harvest and sensate reconstruction. - Lateral cutaneous intercostal nerves accompany lateral perforators (LICAP) and may be included for sensate flaps. (38) - Dorsal cutaneous branches travel with dorsal perforators supplying back sensation. - Long thoracic nerve (C5–C7) is relevant when harvesting serratus/adjacent flaps (serratus chapter): preserve when harvesting serratus slips; sacrifice risks scapular winging. Thoracodorsal nerve accompanies thoracodorsal pedicle when performing latissimus-related dissection. (Serratus chapter) - Included tissues: skin/subcutaneous/fascia/muscle; thickness profile; arc of rotation; common variants/anomalies. - Tissue components: purely fasciocutaneous or musculocutaneous islands (muscle often preserved unless needed); anterior perforators may require splitting pectoralis or rectus; lateral perforators require splitting serratus anterior/latissimus fibers. (38; Serratus chapter) - Thickness: variable by donor site; LICAP and IMAP provide relatively thin, pliable tissue suitable for breast/lower chest/neck resurfacing. (IMAP; 38) - Arc of rotation: DICAP/DLICAP can be rotated as propeller flaps to reach midline back or spine defects; LICAP has maximal arc to reconstruct lateral breast (4th–6th ICS ideal). Pedicle lengths: DLICAP mean integument→intercostal pedicle ≈4.6 ± 0.4 cm; LICAP pedicle length typically 3–5 cm adequate; additional length gained by intrathoracic/intercostal dissection if needed. (38) - Variants/anomalies: perforator presence and size are highly variable; IMAP dominant at 2nd ICS; prior internal mammary harvest (LIMA for CABG) precludes IMAP use. Posterior intercostal perforator anatomy varies by level—10th/11th have longer intermuscular segments. (10; 38; Angiosomes) ## Dissection Steps 1. Positioning, markings, landmarks. - Positioning - LICAP/IMAP/AICAP/SCAP: supine or supine with slight roll as required for chest/epigastric access (IMAP harvest supine). (IMAP; 38) - DICAP/DLICAP: prone or “sloppy lateral” to allow lateral/ posterior access; lateral decubitus for serratus/latissimus exposure if needed. (38; Serratus chapter) - Markings / landmarks - Identify ribs and interspaces (IMAP: 2nd–3rd ribs at sternal border; superior border just above 2nd rib). (IMAP) - Use handheld Doppler to map perforators along expected axes: midline/back (dorsal), midscapular line (dorsolateral), midaxillary line (lateral), and 1–3 cm lateral to sternum (anterior). (38; IMAP) - For LICAP plan place grid centered across midaxillary line and inframammary fold to record coordinates if CTA used. (38) 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Initial incision and exploratory approach - Make small exploratory incision over planned superior border (IMAP method: superior incision first to locate perforator quickly). (IMAP) - Elevate skin and subcutaneous tissue to fascia; identify perforator with loupe magnification and Doppler. (38) - Plane - Dissect in suprafascial/subfascial plane depending on perforator depth; commonly elevate skin island above muscular fascia once perforator identified. For musculocutaneous perforators, expect to dissect through muscle fibers (serratus, pectoralis, rectus) to obtain pedicle length. (38; Serratus) - Perforator assessment - Confirm arterial pulsation and venous caliber; IMAP second-space arteries ≈1–1.5 mm and veins 1.5–2 mm when present. (IMAP) - Use CT angiography or duplex when anatomy uncertain or prior surgery present. (IMAP; 38) 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Exposure and skeletonization - Follow perforator retrograde toward source vessel in costal groove or intercostal space. Split muscle fibers along their direction (serratus/latissimus/pectoralis/rectus) rather than transecting indiscriminately to reduce bleeding and preserve nerve function. (38; Serratus) - To gain extra length dissect along costal groove and divide intercostal muscle at rib inferior border; protect neurovascular bundle and pleura; periosteum may be elevated to visualize pedicle. (38) - For free IMAP with longer pedicle include internal mammary vessel: remove rib cartilage over perforator as needed to access main IMA trunk. (IMAP) - Control/division - Preserve venous outflow and avoid pedicle kinking; if pedicle must be lengthened, skeletonize further toward source vessel. (38) - Divide small lateral/lower perforators encountered laterally if not part of chosen pedicle (IMAP technique). (IMAP) - Transfer/inset - Rotate/propel flap into defect ensuring gentle arc, no torsion, and no tension on pedicle; LICAP/propeller designs commonly require up to 180° rotation. (38) - Perfusion checks - Confirm viability by active bleeding from skin edge, capillary refill and observation (intercostal flaps characteristically show initial hyperemia that often resolves in 24–48 hours). (38) - Use handheld Doppler to confirm flow at donor pedicle after inset; for free transfers standard microsurgical protocols apply (anastomosis patency checks). 4. Donor-site closure techniques. - Primary closure typical for small–moderate harvests; LICAP/IMAP donor usually closed primarily if width limited (IMAP recommended width 5–8 cm for primary closure; clinically limited 6–8 cm). (IMAP; 38) - Larger donor defects may require local flap (thoracodorsal/TDAP) or skin graft. (IMAP) - Place drains for dead-space when significant muscle/fascia dissection performed (serratus/latissimus exposures). (Serratus; 38) ## Indications and Contraindications - Indications: common reconstructive scenarios; size limits; need for thin vs bulky; sensate needs. - Dorsal/Dorsolateral (DICAP/DLICAP): midline and posterior trunk defects, spine wound coverage, posterior thorax soft-tissue reconstruction. (38) - LICAP: partial mastectomy/lower outer–lateral breast defects, lateral chest and flank reconstruction, soft-tissue defects lateral to midline. (38) - AICAP/IMAP: sternal, lower neck, upper chest, tracheostoma reconstruction (IMAP excellent color match for neck); IMAP useful as pedicled flap for lower neck/tracheostoma and as small free facial resurfacing flap. (IMAP; 38) - SCAP: dorsolumbar and lumbar defects. (38) - Size and configuration: IMAP donor width usually 5–8 cm for primary closure; a single IMAP (2nd ICS) can support a narrow (6 cm) by long (≈20 cm from perforator) paddle that may extend 2–3 cm beyond anterior axillary fold. (IMAP) - Sensate reconstruction: include lateral/anterior cutaneous intercostal nerve with LICAP/AICAP when nerve preservation desired. (38) - Contraindications: vascular disease, prior surgery/radiation (relative/absolute), comorbidity risks. - Prior LIMA harvest for CABG precludes use of ipsilateral IMAP (internal mammary harvested). (IMAP) - Prior radiation or extensive anterior chest wall surgery may mandate CTA/Duplex preop; scarring may disrupt perforator pathways. (IMAP; Angiosomes) - Severe peripheral vascular disease affecting intercostal/internal thoracic systems is relative contraindication (consider alternative donor). (Serratus/Angiosomes chapters) ## Postoperative Care - Monitoring schedule/method (clinical, Doppler, implantable probe), warming, antithrombotic practice, positioning/splinting, drains, mobilization, diet/analgesia. - Monitoring: frequent clinical checks for color, capillary refill, and active bleeding at skin edge; handheld Doppler to confirm continued arterial signal postinset. (38; IMAP) - Early hyperemia: expect transient hyperemia in intercostal perforator flaps that typically resolves 24–48 hours—monitor for progressive congestion rather than transient perfusion changes. (38) - Drains: place in donor site when larger dissection/serratus/latissimus exposure performed. (Serratus; 38) - Positioning/mobilization: avoid pressure on pedicle/inset; early mobilization as tolerated but avoid stretching chest/torso that increases tension across pedicle. (general surgical principles; Serratus) - Antithrombotic practice: follow institutional microsurgery protocols for free transfers; for pedicled flaps standard DVT prophylaxis and optimization of hemodynamics recommended. - Return-to-OR thresholds and time windows. - Re-exploration indicated for progressive signs of arterial insufficiency or venous congestion not resolving with conservative measures; early re-exploration provides best chance of salvage (standard microsurgical principles). (general microsurgery principles; not numerically detailed in provided texts) - For intercostal flaps, allow for short initial hyperemic period (24–48 hours) before declaring failure unless progressive ischemia/venous compromise evident. (38) ## Complications (rates & management) - Venous congestion, arterial thrombosis, partial/total loss, infection, fat necrosis; include percent/frequency if present. - Reported numeric rates are not provided in the assigned texts for these specific intercostal flaps. The intercostal chapter notes initial hyperemia is common and typically resolves within 24–48 hours. (38) - Donor-site issues (seroma, hematoma, contour deformity, hernia/weakness) with typical frequencies when reported. - IMAP donor: usually minimal morbidity; donor site typically closed primarily for widths ≤6–8 cm. (IMAP) - Serratus/latissimus exposures: retain at least 3–4 serratus slips (and their innervation) when harvesting to avoid scapular winging. (Serratus) - Management algorithms (re-exploration, leeching, thrombolysis): what, when, how. - Immediate re-exploration for progressive ischemia or congestion remains the standard; if venous congestion of a harvested pedicled flap occurs early and is judged venous, local remedies (surgical revision of inset/tension relief) are preferred; leech therapy is used in venous congestion scenarios in reconstructive practice though not detailed numerically in these PDFs. (38; Angiosomes—delay/vascular dynamics discussed) - Surgical delay (planned staged ligation) may be used when raising a flap spanning multiple angiosomes to allow choke vessel dilation (Angiosomes chapter discussion of delay phenomenon and staged transfers). ## Key Clinical Pearls - Map perforators preoperatively with handheld Doppler; confirm with CTA/duplex when prior chest surgery or radiation history exists (IMAP/LICAP planning). (IMAP; 38) - The second intercostal IMAP is most often dominant for IMAP flaps; IMAP artery lies ≈1.5 cm lateral to sternal border; expect IMAP diameter at 2nd space ≈1–1.5 mm and accompanying vein ≈1.5–2 mm. (IMAP) - Limit IMAP donor width to approximately 5–8 cm to permit primary closure; a single 2nd-space IMAP can support a narrow (6 cm) long (≈20 cm from perforator) paddle that may extend 2–3 cm beyond anterior axillary fold. (IMAP) - On the posterior trunk, identify dorsal (1–5 cm medial) vs lateral dorsal (≈5–8 cm) perforators. DLICAP perforators lie near the midscapular line and can be harvested as pedicled or free flaps; expect mean pedicle length from skin to intercostal bundle ≈4.6 ± 0.4 cm for DLICAP. (38) - For LICAP (breast/lateral chest) plan flaps in 4th–6th interspaces; split serratus/latissimus fibers in line with fibers to expose and preserve the perforator bifurcation—pedicle length 3–5 cm will usually permit rotation. (38) - When extra pedicle length is required, skeletonize retrograde in the costal groove and divide intercostal muscle at the inferior rib border; protect periosteum and pleura. (38) - Preserve long thoracic nerve/upper serratus innervation when dissecting serratus region—leave at least 3–4 inferolateral slips innervated to avoid scapular winging. (Serratus chapter) - Expect transient hyperemia after inset of intercostal perforator flaps; allow 24–48 hours for stabilization unless there are signs of progressive ischemia or venous compromise—then re-explore promptly. (38)