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Radiographs. (A) Sagittal plane of the lumbar MR image showed stenosis of the L4-5, L5-S1 left intervertebral foramen (red arrows). (B) Axial plane of the lumbar MR image showed that the herniated disc of L4-5 compressed the nerve root. (C) Anteroposterior lumbar radiograph after surgery. The L4 paravertebral space was just lateral inferior to the last-but-one pedicle screw. The target of the L5 paravertebral space was just in the lateral rod terminal. (D) Lateral lumbar radiograph after surgery. The last-but-one pedicle screw and the terminal of the rod were just next to the needle paths we designed for L4 or L5 PVB. The depth of the needle from the skin to the target was measured, according to the scale.
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Magnetic resonance (MR) images revealed lumbar intervertebral disc protrusion (migrated to the left, L4-5, L5-S1) (Figure 1A and B), lumbar spinal canal stenosis, and degenerative lumbar scoliosis. Fortunately, on the X-ray film we found that the last-but-one pedicle screw and the terminal of the left rod were just next to the needle pathway we designed for the block, and might be used as markers for the puncture (Figure 1C and D).
Localization of pedicle screw and the rod. (A) The pedicle screw and the rod were identified. (B) The iliac crest, and locations of the pedicle screws and the rods were marked on the skin. Two lines perpendicular to the spine were drawn, at the caudal side of the last-but-one pedicle screw and the terminal of rod.
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With the probe sliding upward, the pedicle screws and the rods could be identified (Figure 2).
Ultrasound and patient set-up for L4 PVB. (A) Performance of the L4 PVB using paramedian transverse oblique scanning with needle in-plane approach. (B) Sonoanatomy of L4 PVB. The vertebral body, pedicle screw, erector spinae, psoas major, and quadratus lumborum were visible. The white arrow indicates the needle path.
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After local anesthetic (2 mL lidocaine 1%) infiltration to the skin and subcutaneous tissue, a 22G 90-mm needle (TuoRen Medical Instrument Finty, Zhengzhou, China) was inserted in a medial to lateral direction, overstride the pedicle screw, and reached the outboard of the foramen intervertebral (Figure 3).
Transducer position and corresponding ultrasound image of L5 PVB. (A) Position of patient, needle, and probe of the ultrasound apparatus under the left L5 PVB. The needle is pointed cephalad-to-caudal toward the target with ultrasound guidance. (B) Transverse ultrasonographic view shows a hyperechoic area between the rod and the iliac bone. The white arrow indicates the out-plane needle path.
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After the puncture point was anesthetized with 2 mL of 1% lidocaine, the needle was inserted towards the hyperechoic area, out the plane of the ultrasound beam in a cephalad-to-caudal direction (Figure 4).