Fig. 2

Schematic diagram showing the variable catheter tip/needle position. A Needle on the transverse process. B Needle on the lower border of transverse process which may lead to the LA spread along the psoas muscle towards LP. EO—external oblique, ESM—erector spinae muscle, IO—internal oblique, LD—latissimus dorsi, PM—psoas muscle, QL—quadratus lumborum, TA—transversus abdominis. TLF—thoraco lumbar fascia, TP—transverse process, VB—vertebral body