Comparison of the Distance of the Erector Spinae Muscle from the Skin at Different Thoracal Levels and Different Positions Under Ultrasonography

Background: The erector spinae plane block can be executed at various thoracic levels and in different positions. Our study aimed to determine the optimal distance of the erector spinae muscle from the skin and to identify the best ultrasonography imaging quality across different thoracic levels and positions. Materials and Methods: The erector spinae muscle was located using a high-frequency 10-15 MHz linear ultrasound probe at distinct thoracic levels (T1-T2, T5-T6, T11-T12) and in various positions (lateral, sitting, and prone). Results: The proximity of the erector spinae muscle to the skin was found to be significantly closer at the T5-T6 level compared to the T1-T2 and T11-T12 levels (p = 0.001; p < 0.01). In the prone position, the distance of the erector spinae muscle to the skin was significantly lower than in the lateral and sitting positions (p = 0.001; p < 0.01). Conclusions: In an ESPB to be applied at the T5-T6 thoracal level and in the prone position, the erector spinae muscle is closer to the skin, and the ultrasound image is better.