Sagittal cadaver anatomic section showing the relation of the lumbar plexus to the transverse process (TP) and the psoas muscle (PM). The reference marker of the Java application, seen in this figure as a green cross-hair, is over the L3 nerve of the lumbar plexus (same as in Fig. 8-7). The L3 nerve of the lumbar plexus is seen in a fat-filled “intramuscular compartment,” that is, the psoas compartment between the thick fleshy anterior and a thin posterior part of the psoas muscle between the L3 and L4 TP. ESM, erector spinae muscle. Source: Sonoanatomy Relevant for Ultrasound-Guided Lumbar Plexus Block, Atlas of Sonoanatomy for Regional Anesthesia and Pain Medicine Citation: Karmakar MK, Soh E, Chee V, Sheah K. Atlas of Sonoanatomy for Regional Anesthesia and Pain Medicine; 2018 Available at: https://accessanesthesiology.mhmedical.com/DownloadImage.aspx?image=/data/books/2220/karmakar_fig-12-08.png&sec=171517430&BookID=2220&ChapterSecID=171517418&imagename= Accessed: October 14, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved