Comparison of Median and Intermediate Approach in the Ultrasound-Guided Sacral Erector Spinae Plane Block: A Cadaveric and Radiologic Study

Abstract Backgrounds: Erector spinae plane block (ESPB) has become very popular for post-operative and chronic pain management. ESPB applications sacral area procedures have been named 'sacral ESPB’. This study is aimed to conduct a cadaveric study to determine how local anesthesia was distributed at median and intermediate approaches of the sacral region ESPB procedures. Materials and Methods: Four cadavers were grouped into two groups; median and intermediate approaches. An ultrasound-guided ESPB was performed with a mixture of radiocontrast and dye. After the distribution of the solution was observed by computed tomography, cadavers were dissected in order to observe the dye spread in the groups. Results: CT Images of the median group demonstrated subcutaneous pooling of contrast agents between S1 and S5 horizontal planes. Contrast agent passing from the sacral foramina to the anterior of the sacrum via spinal nerves was also observed between S2-S5. In the intermediate group contrast distribution was observed along the bilateral erector spinae muscle between L2-S3 horizontal planes, and no anterior transition was detected. Dissection findings in the median group, methylene blue spread was observed in the subcutaneous tissue area between the S1-S5 horizontal planes. There was no methylene blue solution spread under the superficial fascia or the muscle plane. In the intermediate group, the red-colored radiocontrast solution was detected between the L2-S3 intervertebral levels in the erector spinae muscle group. Conclusion: Radiocontrast dye was detected at superficial and erector spinae compartments respectively at median and intermediate cadaver groups both radiological and anatomically. The anterior transition of the radiocontrast was detected in only the median cadaver group. Clinical Trial: Karadeniz Technical University Ethics Approval No: 2022/229, ClinicalTrials.gov ID: NCT05716061