Effects of ultrasound-guided adductor canal block at different volumes on postoperative analgesia management in patients undergoing total knee arthroplasty: a prospective clinical study

Background: Many different analgesia techniques are performed in knee arthroplasty. Adductor canal block is one of the analgesia techniques following knee arthroplasty. The aim of this study was to evaluate the effectiveness of adductor canal block performed at different volumes (20 ml, 30 ml, 40 ml) for postoperative analgesia management in patients undergoing total knee arthroplasty. Methods: This single-center prospective randomized controlled study included 90 patients, aged between 18 and 65, with ASA classification I-II-III, who were scheduled for total knee arthroplasty surgery under spinal anesthesia. Patients were randomized into three groups: Group 20, group 30 and group 40. Postoperative pain, opioid consumption, and motor block were evaluated. Statistical analysis was conducted to compare the primary and secondary outcomes between groups. Results: The difference in static NRS scores at all times except the 8th hour and in dynamic NRS scores at all times was found to be statistically significant. Group 40 had significantly lower opioid consumption and additional analgesic requirements compared to Group 20, but no statistically significant difference was found compared to Group 30. Group 40 had a statistically significantly higher rate of motor block in the first 8 h compared to Groups 20 and 30. No statistically significant difference was found between Groups 20 and 30 in terms of motor block at all times. Conclusions: The findings of our study showed that the optimal volume of adductor canal block to provide effective analgesia and preserve muscle strength functions in the postoperative period after total knee arthroplasty was 30 ml. Clinical trial registration number: NCT06084403.