Decoding quadratus lumborum blocks: Fascial pathways and analgesic coverage—A narrative review

Quadratus lumborum blocks extend abdominal wall analgesia by engaging thoracoabdominal and lumbar pathways, yet outcome variability persists because fascial continuities, neural trajectories, and sonographic-anatomic correlations are emerging. This narrative review synthesises foundational anatomy, cross-sectional relationships, and ultrasound correlations to explain injectate spread and to guide precise techniques. Drawing on cadaveric dissections, radiologic studies, and live sonoanatomy, we map the three-dimensional interplay of muscles, fascial planes, and nerves across the T12-L1 transition. These insights clarify why anterior/transmuscular approaches more reliably reach paravertebral and lumbar plexus corridors, whereas superficial or lateral techniques chiefly provide somatic flank coverage. We also dispel common misconceptions propagated by oversimplified schematics. Framing the quadratus lumborum block within a continuous fascial network-linking thoracolumbar, transversalis, psoas, and endothoracic fascia-supports more accurate target selection, rational volume planning, and improved safety. The review offers a practical framework for matching block variants to surgical indication, enhancing reproducibility, and achieving more predictable, opioid-sparing analgesia clinically.