Which USG guided position is the most ideal for the Infiltration Block between the Popliteal Artery and Capsule of Knee (IPACK) ?

Ipack block aims to affect the deep knee branches of the sciatic nerve by local anesthetic injection between the posterior knee capsule and the popliteal artery. With this block, the motor functions of the knee are preserved and pain is reduced. In our study, we aimed to determine the most ideal position for the block by making USG measurements in prone, supine and frog leg (flexion, abduction) positions, and to determine the image quality in these positions. Method: Our research was approved by the Ethics Committee of Harran University Faculty of Medicine, session no. 01 dated 09.01.2023 and decision numbered HRÜ 23.01.12. This study included 100 healthy volunteers between the ages of 18 and 65 who had no movement restrictions in the lower extremities, no trauma, surgical procedures, burn scars and active infections in the area to be studied, and a Body Mass Index (BMI) <35, and patients who agreed to participate in the study was done. Volunteers were given prone, supine and frog-leg (flexion, abduction) positions, and the distance of the popliteal artery and knee capsule to the skin was measured and recorded using USG. Image quality was divided into five categories: very bad, bad, mediocre, good and very good and recorded. Measurements were made by the same researcher. xi Results: In our study, our popliteal artery distance measurement was closest to the skin in the prone position. In our knee capsule distance measurements, the frog leg position was measured closest to the skin. The best quality image was detected in the prone position. Additionally, as BMI increased in our study, our measurement distances increased in all positions, as expected. We detected a weak negative relationship between BMI and image quality. We did not detect a significant relationship between age and image quality. Conclusion: In line with the data we obtained from our study, we determined that the prone position for IPACK block is the most appropriate position in terms of popliteal artery distance and image quality. Different positions may be preferred due to patient-specific conditions and the need for additional block application. Large and further studies are needed with different USG probes and positions.