**Region:** Trunk and Lower Back # Lumbar Artery Flap ## Anatomy - Pedicle: lumbar segmental arteries (L1–L4) with accompanying veins/venae comitantes. Mean caliber of the lumbar artery/vein at origin reported approximately 2.1 to 2.8 ± 0.3 mm (origin diameter ~2.1 ± 0.5 mm in some series). Pedicle length is relatively short; pedicle length decreases from L1 → L4 (mean L1 ≈ 6.3 cm; mean L4 ≈ 5.5 cm). (Blondeel et al.) - Course: lumbar arteries arise posterolaterally from the abdominal aorta at the upper four lumbar vertebral levels; they run posterior to psoas major/lumbar plexus, cross the quadratus lumborum (upper three posterior to QL, L4 may pass anterior to QL), pierce the posterior aponeurosis of transversus abdominis, travel anteriorly between transversus and internal oblique, sometimes have an intramuscular course through erector spinae, then pierce the thoracolumbar fascia to enter the subcutaneous fat of the "love-handle"/flank. Skin island territory is innervated by the superior cluneal nerves (can be included for sensate reconstruction). (Blondeel et al.) - Perforator pattern: - Typical skin entry points 5–9 cm lateral to midline; ~85% of lumbar perforators enter skin at 7–10 cm lateral to midline. They are often located just over the iliac crest or 1–4 cm cranial to it. (Blondeel et al., Kiil et al., Sommeling et al.) - Two principal types: musculocutaneous perforators (pass through quadratus lumborum or erector spinae) and septocutaneous perforators (between erector spinae and quadratus lumborum). Perforators of the fourth lumbar artery are more frequently septocutaneous than those of L1–L3. (Blondeel et al.) - Number: lumbar arteries supply multiple perforators; mean perforators per lumbar artery reported ~6 ± 2 in one anatomical series. Primary territory per single lumbar artery ~45 ± 23 cm2; total flank skin territory attributable to lumbar arteries reported ~160 ± 50 cm2. Perforator diameter tends to increase from L1 → L4; mean perforator diameter reported ~0.7 mm with supplied surface area ~30 cm2 (range 14–64 cm2) in other studies. (Blondeel et al., Offman et al., Lui et al.) - Presence/variability: perforators may be absent in a subset—reported absence rates for individual levels: L1 ~14.3%, L2 ~9.3%, L3 ~23.8%; L4 perforators are most consistently present. (Kato et al.; cited in Blondeel et al.) - Nerves: superior cluneal nerves supply the cutaneous island and may be included for a sensate flap. Posterior cutaneous branches and adjacent lumbar plexus structures are deep to the pedicle—take care during deep dissection. (Blondeel et al.) - Included tissues: skin, subcutaneous fat, thoracolumbar fascia; flap often bulky (even in thin patients), making it suitable for volume reconstruction (e.g., breast). A caudal subcutaneous/gluteal extension can be incorporated to augment upper-pole volume for breast reconstruction. - Arc of rotation / mobility: the pedicle is short and the flap bulky; mobility is limited. As a pedicled flap it is most useful as an islanded rotation flap (not a large advancement). Intramuscular dissection into the quadratus lumborum can mildly increase arc for L1–L3 perforators; L4 typically lies more anterior to QL limiting this. For free transfer, routine use of an interposition graft is commonly necessary because native pedicle length is short. (Blondeel et al.) - Common variants/anomalies: variability in number, caliber, intramuscular vs septocutaneous course, and occasional absence of perforators at specific levels; L4 most reliable. ## Dissection Steps 1. Positioning, markings, landmarks. - Preoperative imaging: mark dominant LAP(s) on multidetector CT angiography (MDCT) preoperatively and confirm with hand-held Doppler with patient prone. (Blondeel et al.) - Patient sequence for free-breast reconstruction: supine → prone → supine (supine for recipient/IEA graft harvest, prone for LAP harvest, back to supine for anastomosis). Two-team simultaneous workflow recommended (recipient + interposition graft/acceptor; second team harvests flap). (Blondeel et al.) - Surface landmarks: midline, posterior superior iliac spine (PSIS), iliac crest, midaxillary line. Dominant perforator commonly ~8 cm lateral to midline and 1–2 cm cranial to iliac crest for the fourth LAP; in planning mark perforator and design a fusiform skin island centered on the dominant perforator with horizontal/oblique axis from posterior midline toward ASIS/midaxillary line. For breast recon, mark a caudal gluteal subcutaneous extension for upper-pole filling. (Blondeel et al.) 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Incisions and initial dissection: begin with medial incision through skin and subcutaneous tissue down to the erector spinae fascia. Proceed laterally in a suprafascial plane cautiously to avoid injuring perforators. An alternative approach is to incise the erector spinae fascia vertically to enter the loose connective tissue plane below it where perforators and sensory nerves are easier to visualize. (Blondeel et al.) - Perforator identification: identify the rounded deflection of the erector spinae before QL—large perforators typically arise here (commonly L3–L4). Confirm perforator pulsatility and size; avoid full elevation of flap until perforator adequacy is certain. (Blondeel et al.) 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Pedicle exposure: dissect the perforator through the thoracolumbar fascia; trace intramuscular course as needed. Free pedicle to a working length—authors recommend harvesting at least ~4 cm of pedicle; pedicle up to ~6–7 cm possible but further dissection risks pain/neuropraxia. Avoid dissection beyond transverse processes. Because branches may adhere to iliac crest periosteum, careful sharp dissection is required for distal branches. (Blondeel et al.) - Free-flap graft strategy: because pedicle is short, routinely harvest an interposition graft (deep inferior epigastric artery/vein) through a small (<~4 cm) incision centered at lateral border of rectus muscle; obtain graft length ~6–8 cm to reach internal mammary vessels comfortably and to match calibers. On the back table suture graft to the LAP flap with micro-sutures (9–0 or 10–0) before final inset. Avoid making the interposition graft excessively long (risk of twisting/kinking). (Blondeel et al.) - Transfer/inset: after graft anastomosis to flap, reposition patient supine, perform recipient anastomoses (internal mammary or thoracodorsal vessels), inset flap so caudal gluteal extension occupies the upper pole for natural contour. Secure orientation to avoid pedicle kinking/tension. (Blondeel et al.) - Perfusion checks: standard free-flap evaluation applies (clinical monitoring and Doppler confirmation). Given variable anatomy, confirm perfusion intraoperatively and be prepared to convert plan if perforator insufficient. (Blondeel et al.) 4. Donor-site closure techniques. - Close donor site over suction drains; use quilting sutures or vest‑over‑pants closure where appropriate to reduce dead space and seroma risk. Consider drain placement and abdominal binder postoperatively to limit donor seroma. Close in layers; skin closure per surgeon preference. (Blondeel et al.) ## Indications and Contraindications - Indications: - Free-flap autologous breast reconstruction when abdominal donor sites are unavailable or inadequate (LAP provides consistent bulk and favorable tissue consistency/shape). (Blondeel et al.) - Pedicled coverage for lumbosacral defects, spine coverage, pressure sores over posterior pelvis (islanded rotation pedicled LAP). (Blondeel et al.) - Reconstruction of deep defects requiring substantial soft-tissue volume and central projection. - Size limits / tissue character: - Flap is often bulky and provides reliable volume even in slender patients; a caudal gluteal extension may increase volume for breast upper pole. The amount of harvestable skin is dictated by pinch test and local laxity. (Blondeel et al.) - Sensate reconstruction: - Possible by including superior cluneal nerves, but not routine; may be incorporated when desired. (Blondeel et al.) - Contraindications / relative contraindications: - When a standard abdominal-based flap (DIEP/TRAM) is possible and preferable, LAP is usually a second-line option because harvest is more challenging and complication/failure rates reported higher than DIEP. - Prior flank/retroperitoneal surgery creating scar in planned pedicle course or prior radiation in the flank region that compromises vessels (preoperative CTA/Doppler required to confirm vascular anatomy). - Significant peripheral vascular disease or occlusive disease affecting aorto‑lumbar origins or recipient vessels—exercise caution (general flap selection guidance). (Blondeel et al.; Thoracic/Abdominal reconstruction text general principles) ## Postoperative Care - Monitoring schedule/method: - Hourly clinical checks of color, temperature, and capillary refill while in high-care setting for the first 48 hours; thereafter checks every 4–6 hours as protocol. Continuous Doppler monitoring as available/desired is consistent with standard free flap practice. (Blondeel et al.) - Drains / wound care: - Donor‑site drains removed when output < 30 mL/24 hours; some patients discharged with donor drains in situ. Use quilting sutures/vest-over‑pants and abdominal binder to reduce seroma risk. (Blondeel et al.) - Immobilization/positioning: - For breast reconstruction, wear a supportive (suspension) bra day/night for 2 weeks, then daytime only for weeks 3–4. Limit activities that tension the pedicle/graft until healing secure. (Blondeel et al.) - Antithrombotic practice: - Follow institutional standard microvascular antithrombotic protocols (Blondeel et al. state "standard postoperative protocol for free flaps applies"); individualization recommended. - Mobilization/diet/analgesia: - Standard post-free-flap protocols apply; early mobilization within safe limits per recipient-site and donor concerns; maintain analgesia appropriate for prone→supine positioning and donor-site discomfort. - Return-to-OR thresholds and time windows: - The first 48 hours are the highest risk—clinical deterioration or Doppler loss during this critical window typically prompts urgent re-exploration per standard free‑flap practice. (Blondeel et al.) ## Complications (rates & management) - Anatomical/harvest-related findings (numbers present in literature excerpts): - Perforator presence variability: reported perforator absence rates at levels—L1 ~14.3%, L2 ~9.3%, L3 ~23.8%; L4 perforators most consistently present. (Kato et al., cited in Blondeel et al.) - Perforator location: 85% enter skin at 7–10 cm lateral to midline; typical localization 5–9 cm from midline. (Blondeel et al.) - Vascular statistics: Offman et al. reported lumbar arteries supply a mean of ~6 ± 2 perforators to a skin territory of ~160 ± 50 cm2; mean primary territory for a single lumbar artery ~45 ± 23 cm2; Lui et al. reported mean perforator diameter ~0.7 mm and surface area ~30 cm2. (Blondeel et al.) - Flap complications and frequencies: - The chapter notes that LAP flaps have higher overall complication and failure rates compared with the DIEP in comparative series, but explicit overall percentage failure rates are not provided in the excerpt. Donor‑site seroma rates reported to be higher than for some other donor sites (qualitative). (Blondeel et al.; Opsomer et al. referenced) - Partial necrosis: the angiosome is generally reliable with relatively low partial necrosis in published series (qualitative statement in text). (Blondeel et al.) - Typical complications and management: - Venous congestion / arterial thrombosis / flap compromise: standard microvascular algorithms apply—urgent re-exploration is indicated for clinical or Doppler signs of compromise, especially during the first 48 hours. Be prepared to revise anastomoses, remove kinks, or revise grafts. (Blondeel et al.) - Pedicle shortness / need for grafts: plan routine interposition grafting (deep inferior epigastric artery/vein) for free transfer to provide comfortable reach and caliber match; harvest graft ~6–8 cm. Avoid excessive graft length (kinking/twisting risk). (Blondeel et al.) - Donor-site seroma/hematoma: use drains, quilting sutures, or vest-over‑pants closure; manage symptomatic seroma with aspiration or drain replacement as indicated. (Blondeel et al.) - Injury during deep dissection: thoracolumbar fascia is rigid—sharp dissection advised to prevent vessel damage; avoid stump or blunt dissection that may shear small vessels. (Blondeel et al.) - Inadvertent perforator absence or poor caliber: if dominant perforator inadequate intraoperatively, convert plan to alternate donor flap or consider additional perforators; preoperative CTA/Doppler reduces but does not eliminate this risk. (Blondeel et al.) - Donor-site issues: - Seroma is more common; contour changes of flank and potential discomfort when sitting if dissection extends into ischial fat pad—avoid violating ischial fat pad. (Blondeel et al.) - Neuropraxia/pain: long pedicle dissection approaching transverse processes can cause prolonged pain/neuropraxia—limit pedicle dissection to what is needed (authors recommend pedicle ~4 cm as practical). (Blondeel et al.) - Management algorithms (what, when, how): - Pedicle/graft strategy: if free transfer is planned, routinely prepare an interposition graft (DIEA/V) on back table and anastomose to the LAP before recipient anastomosis. Use 9–0/10–0 sutures for microvascular grafting. Avoid overly long grafts. (Blondeel et al.) - Re-exploration: any persistent/significant clinical compromise (loss of Doppler signal, rapid color change, progressive ischemia) during early postoperative period should prompt immediate re-exploration and correction of mechanical causes (kink, thrombosis), revision of anastomoses, or thrombolysis per institutional protocols. (Standard free-flap practice summarized in chapter.) ## Key Clinical Pearls - Use a two‑team approach for free-breast reconstruction (recipient/preparation + flap/graft harvest) to minimize ischemia time and operating time. (Blondeel et al.) - Preoperatively map LAPs with MDCT angiography and confirm intraoperatively with Doppler in prone position; expect dominant perforator most often ~7–10 cm lateral to midline (mark accordingly). (Blondeel et al.) - Begin dissection medially; the lateral deflection of the erector spinae before the quadratus lumborum is the common site to encounter a sizable perforator (L3–L4 region). (Blondeel et al.) - Do not detach the flap from the iliac crest or complete wide undermining before completing perforator/pedicle dissection—heavy flaps can be difficult to manage and risk traction injury. (Blondeel et al.) - Plan on routine interposition grafting for free transfer: harvest a deep inferior epigastric artery/vein graft through a short lateral rectus incision (aim for ~6–8 cm) to provide length and caliber match to internal mammary recipient vessels. (Blondeel et al.) - Avoid making the interposition graft too long—excess length predisposes to twist/kink once connected at the chest. (Blondeel et al.) - Pedicle dissection beyond transverse processes and periosteal branches at the iliac crest can be tedious and adherent—use sharp dissection and beware of pain/neuropraxia if extended; limit pedicle harvest to what is required for safe anastomosis (~≥4 cm practical length). (Blondeel et al.) - For pedicled uses, orient flap as an islanded rotation; intramuscular dissection into the quadratus lumborum may modestly increase arc for L1–L3 perforators (L4 typically less amenable). (Blondeel et al.)