Fig. 1

Axial E12 plastinated sections (a, c) and schematic illustrations (b, d) at approximately L1 (a, b) and L4 (c, d) highlighting anatomical structures at these vertebral levels. b, d Dotted lines and shading, Green - psoas major muscle; Blue – quadratus lumborum muscle; Purple – erector spinae muscles; Red – spinotransverse muscles. b round white dotted regions (bilateral) denote 12th rib. d square dotted box surrounds enlarged inset; round dotted circle indicates morphological feature of interest (ILB fatty ‘tent’). Legend: A – aorta; ES – erector spinae muscles; ESA – erector spinae aponeurosis; ILB – iliocostalis – longissimus boundary and indentation; ISL – interspinous ligament; IT – intertransversarii muscle; IVC – inferior vena cava; K – kidney; L – liver; P – psoas major muscle; QL – quadratus lumborum muscle; SAF – superior articular facet; SP – spinous process; SPC – spinal canal; SPT – spinotransverse muscle group; ZJ – zygapophysial joint