Parasagittal approach of ultrasound transforaminal injection. Pink box, Loizides et al. [12], Kim et al. [15]a): Curvilinear probe; placed to view ITL at PAP. Needle was inserted IP and needle tip was advanced barely in ITL. Red box with black outline, Kim et al. [15]b): Curvilinear probe; placed to view ITL at PAP, probe was tilted at 20°–25° medially (PSO). Needle was inserted IP, and needle tip was advanced barely through ITL. Blue box, Wan et al. [17]c): Curvilinear probe, placed at edge of zygapophyseal joints. Needle was inserted OOP, and needle tip was between adjacent facets. TP, transverse process; FJ, facet joints; SP, spinous process; IAP, inferior articular process; SAP, superior articular process; ITL, intertransverse ligament; PAP, pararadicular aditus plane; PSO, parasagittal oblique; IP, in plane; LF, lateral facet; OOP, out of plane.