The needle penetrates the external and internal abdominal obliques and the posterior tail of the transversus abdominis in order to place the needle tip on the anterior side of the aponeurotic posterior extension of the tranverse abdominis that connects to the quadratus lumborum
When local anaesthetic is injected in this position it spreads across the aponeurosis to cover the anterior side of the quadratus lumborum where it blocks the subcostal and iliohypogastric nerves before the lateral cutaneous branches branch off
Needle (red), transverse abdominis (cyan asterix), internal and external abdominal obliques (green and yellow asterixs), quadratus lumborum (red asterix), retroperitoneal fat (magenta asterix), transversalis fascia (blue arrows)
