The goal of this cadaveric study is to learn about the distribution of contrast agent in ultrasound-guided sacral ESPB. The main questions it aims to answer are

1. Which nerves are affected by this block.
2. Which approach is the best for optimal analgesia in human

4 embalmed cadavers will be divided into groups of 2 and sacral ESPB will be made with 2 different methods. The cadavers will be removed from the solution 48 hours before and will be placed in the prone position, there will be no history of trauma or surgery in the sacral region of the cadavers, and no dissection will be performed from the sacral regions.

In the median approach, the probe will be placed on the cadaver, which was previously placed in the prone position, using a 12-18 megahertz high-frequency linear probe with ultrasound to form a right angle to the sacral crest. After being placed parallel to the sacrum and observing the median crest, a 50 mm echogenic needle will be inserted by advancing the implant towards the second sacral level. After touching the crest, the distribution will be observed by retreating 1mm and making 1 cc of serum physiologic. Then all 40 ml of methylene blue and radiocontrast solution will be given. In the intermediate approach; From the second sacral level, 20 ml of red acrylic dye and a solution containing radiocontrast will be given to the right and left by entering the sulcus between the median and intermedian crests with the same technique, using the same technique, under the guidance of ultrasound. After the procedure, sacral tomography will be performed on the cadavers. The spread of radiocontrast material will be observed and their reconstruction will be performed. Later, anatomical dissection will be performed on the cadavers and the spread of the dyes given will be observed. Which of the sacral intervention methods is more effective in clinical practice will be evaluated.

Estimated durations of the study;

1. Removing the cadavers from the solution 48 hours before, performing the block, going to the radiology and performing the CT scan, coming to the anatomy laboratory and performing the dissection: 3 days
2. Reconstruction and interpretation of radiology images: 1 week
3. Interpretation of anatomical dissection: 1 week
4. Evaluation and writing of the study: 1 month

Inclusion Criteria:

• Embalmed cadaver

Exclusion Criteria:

• None of the cadavers had a history of trauma or surgery in the sacral region