Fig. 1

An example of US-guided L4 thoracolumbar fascia injection. The upper right corner showed the patient’s posture diagram, the placement direction of the ultrasound probe was shown by the blue icon. The needle tip was advanced to the apical part of transverse process using the in-plane approach. The anatomical structures are shown in the figures in the figure: 1. L4 spinous process; 2. L4 vertebral body; 3. L4 transverse process; 4. L4 superior articular process; 5. erector spinae muscle; 6. quadratus lumborum muscle; 7. psoas major muscle