6 – Identification of the shamrock and needle insertion

The transducer is moved dorsally keeping the transverse orientation until the QL muscle is identified with its attachment to the lateral edge of the transverse process of the L4 vertebral body

With the psoas major muscle (PM) anteriorly, the erector spinae muscle (ESM) posteriorly and the QL muscle adherent to the apex of the transverse process, a well recognizable pattern of a shamrock with three leaves can be seen:

The transverse process of vertebral body L4 is visualized as the stem of the shamrock. The three leaves are the muscles: quadratus lumborum, psoas major, and the erector spinae muscle.

The needle is inserted in-plane to the transducer (lateral edge) and the tip of the needle is advanced through the QL muscle, penetrating the ventral proper fascia of the QL muscle and LA is finally injected between the QL and PM