The Lumbar Artery Perforator Free Flap as an Alternative Option for Breast Reconstruction in Low BMI Patients: Analysis of CT Angiography of Donor Sites Across BMI

Casey et al, J Reconstr Microsurg, 2025. PMID: 39362641

Key takeaways

• In 300 DIEP candidates, lumbar fat thickness was ≥2.5× abdominal in low‑BMI women (20 mm vs 47 mm; ratio 2.53).

• Lumbar‑to‑abdominal thickness ratio fell with rising BMI (2.53 → 1.85; p < 0.001).

• Fourth lumbar perforator lies consistently 6.4–9.5 cm lateral to the spinous process (mean 7.7 cm), independent of BMI.

• Findings support the lumbar artery perforator (LAP) flap as a volume source when abdomen and thighs are lean.

Background

Low‑BMI patients often lack sufficient abdominal or thigh donor fat for standard autologous breast reconstruction. Clinical observation suggests lumbar fat persists even when BMI is low.

Objective

Quantify lumbar vs abdominal subcutaneous thickness across BMI strata and map lumbar perforator location to evaluate LAP flap feasibility in thin patients.

Methods

• Design: Retrospective cohort, CT angiography analysis (Level III).

• Setting: Royal Marsden Hospital, London; DIEP database 2012‑2019.

• Participants: 300 women split into three equal cohorts of 100 each—low BMI (<22 kg/m²), normal BMI (22–24 kg/m²), and high BMI (>30 kg/m²)—scheduled for DIEP reconstruction; mean age 52 y.

• Measurements: Subcutaneous thickness at the level of the umbilicus and the L4-5 interspace; in addition, the distance of the fourth lumbar perforator was recorded.

• Endpoints: Ratio of lumbar‑to‑abdominal thickness (primary); perforator coordinates (secondary).

• Statistics: One‑way ANOVA for group comparisons; significance p < 0.05.

Results

• Thickness: Low‑BMI abdominal 20 mm vs lumbar 47 mm (ratio 2.53); normal 2.12; high 1.85. 

• Skeletal landmark: Fourth LAP consistently lay 7.7 ± 0.7 cm lateral to the spinous process across BMI groups (p = 0.09). 

• Surface landmark: Midline‑to‑LAP distance expanded with BMI (8.6 cm low vs 10.7 cm high; p < 0.001), reflecting greater soft‑tissue girth. 

Conclusion

CT data confirm that even very thin women retain proportionally greater lumbar subcutaneous fat relative to abdominal fat and have reliable perforator anatomy, justifying the LAP flap as a primary autologous option when abdominal or thigh tissue is insufficient.

Strengths & limitations

• Large imaging cohort with equal BMI distribution.

• Objective CTA measurements and statistical rigor.

• Retrospective; no actual LAP reconstructions or clinical outcomes measured. 

• Volume extrapolated from 1‑D thickness; true flap weight not calculated.

• Single‑center UK cohort of DIEP candidates—generalizability limited.

Future directions

Prospective studies should correlate CTA‑predicted lumbar volume with harvested LAP flap weight, refine patient selection algorithms, and report surgical/esthetic outcomes.

Clinical relevance

When a low‑BMI patient lacks abdominal or PAP donor volume, pre‑operative CTA should include lumbar imaging; a LAP flap can reliably yield autologous tissue with acceptable donor contour.