Which usg guided position is the most ideal for the popliteal nerve block?

Introduction and Purpose: Peripheral nerve blocks, one of the regional anesthesia techniques, show their effect by temporarily blocking the sensory, motor and sympathetic functions of the targeted nerve. These methods, which are frequently used for both anesthesia and postoperative pain control during surgical interventions, have become more reliable with the advancement of ultrasonography technology and the increase in training programs. Popliteal nerve block, one of these blockage techniques, is performed by blocking the sciatic nerve located in the popliteal fossa behind the knee. The sciatic nerve is responsible for the sensory and motor innervation of a large part of the lower leg region. For this reason, popliteal block is frequently preferred in surgical procedures below the knee, foot and ankle operations. Three different approach methods can be used when applying popliteal nerve block: posterior, medial and lateral. The most commonly used methods in clinical practice are posterior and lateral approaches. Popliteal block can be applied by placing the patient in the supine, prone or lateral position. The aim of this study is to compare measurements made in different patient positions with the help of ultrasonographic imaging; to determine the most comfortable and appropriate position for both the operator and the patient by determining the nerve points closest to the skin surface. Method: This study was conducted prospectively in the Department of Anesthesiology and Reanimation, Harran University Faculty of Medicine. Approval decision was obtained from the Harran University Faculty of Medicine Clinical Research Ethics Committee (09.09.2024 Date and 13th Session, Decision No. 30). Healthy volunteers between the ages of 18 and 65 who had no movement restriction in the lower extremities, no trauma, surgical procedure, burn scar in the study area, no active infection, and with a body mass index (BMI) <35 and who agreed to participate in the study were included in this study. The study was conducted with a total of 100 cases, 50% (n=50) female and 50% (n=50) male, at Harran University Faculty of Medicine Hospital between September and December 2024. The individuals' ages, genders, and xiii BMI (body mass index) were recorded and the measurements were evaluated by the same person and the same ultrasound device. After imaging the knee capsule and popliteal artery with the linear probe of the ultrasound from the knee region while the patient was in the prone position, the popliteal nerve at the 12 o'clock position, the patient in the prone position with the knee at 45 degrees of flexion, the popliteal nerve at the 12 o'clock position, the patient in the lateral decubitus position with the knee in full extension, the popliteal nerve at the 12 o'clock position, the patient in the lateral decubitus position with the knee at 30 degrees of flexion, the popliteal nerve at the 12 o'clock position, the patient in the lateral decubitus position with the knee at 45 degrees of flexion, the distances of the reference points to the skin in different positions were measured and recorded. The clarity of the image from the measured areas was evaluated as (poor: 1, medium: 2, good: 3). Findings: No poor image quality was encountered according to the position given to the patients. However, it was observed that the number of patients with medium (39) and good (61) quality was equal in each group. According to the position given to the patients, the distance of the politeal nerve to the skin was found to be statistically significant (p=0.036*). However, there was no change in the image quality of the patients according to the position. In good image quality, patients with normal weight were in majority (%83.6), but patients with medium image quality were overweight (%71.8) or obese (%28.2). The BMI values of the patients were found to be statistically significant (p<0.05) on the image quality (p=0.000*). The effects of the BMI values of the patients on the image quality were examined. Accordingly; the statistical difference between the image quality and BMI in the position was found as p=0.0007 at 0 O LTRL, p=0.001 at 30 O LTRL, and p=0.000 at 45 O LTRL. The statistical difference between the image quality in the position and BMI was found as p=0.007 in 0 O PRON, p=0.000 in 30 O PRON and p=0.004 in 45 O PRON. It was determined that the BMI values of the patients were effective on the image quality of all positions. In addition, the mean BMI value of the patients with moderate image quality was 28.74±2.41 and it was seen that they were overweight or obese. The mean BMI value of the patients with good image quality was 22.46±2.16 and it was seen that they were of normal weight or underweight. It was determined that the BMI values of the patients affected the image quality. It was observed that there was a statistical significance between the distance of the politeal nerve to the skin in the 0 O LTRL position (1.37±0.43) and the distance of the politeal nerve to the skin in the 0 O PRON position (1.69±1.97) and that the distance was greater in the 0 O PRON position. In the 30 O LTRL position, there was a statistical significance between the distance of the politeal nerve to the xiv skin (1.25±0.39) and the 0 O PRON (1.69±1.97) positions, the 30 O PRON (1.40±0.38) positions and the 45 O PRON (1.46±0.38) positions. It was observed that the 30 O LTRL position had a shorter distance than the other positions (0 O PRON, 30 O PRON and 45 O PRON). In the 45 O PRON position, there was a statistical significance between the distance of the politeal nerve to the skin (1.46±0.38) and the 30 O LTRL (1.25±0.39) positions and the 45 O LTRL (1.30±0.36) positions and it was observed that the distance of the 45 O PRON position was greater than the other positions (30 O LTRL and 45 O LTRL). Conclusion: In our study, it was seen that different positions given to the patient and different angles given to the leg did not affect the image quality. It was seen that the image quality was negatively affected as the BMI of the patients increased. In all positions between the distance of the reference points to the skin and the image quality among the image groups, it was seen that the image was of medium quality when the distance of the politeal nerve to the skin was greater than the position given to the patients, but in good image quality, the distance of the politeal nerve to the skin was less. Keywords: popliteal block, peripheral nerve block, knee surgery