A convex ultrasound probe (frequency 2-5 MHz) was positioned at the patient's inguinal ligament, with one end directed toward the anterior inferior iliac spine (AIIS), clearly visualizing the bony prominences of the iliopubic eminence and the AIIS. The needle tip was directed medially toward the pectineus muscle. Upon reaching the space between the pectineus muscle and the pubic bone, and after confirming the absence of blood on aspiration, 30 ml of 0.375% ropivacaine was injected.

An ultrasound probe was positioned at the inguinal ligament, with the needle inserted parallel to the long axis of the probe. After confirming no blood upon aspiration, 15 ml of 0.375% ropivacaine was injected into the fascial plane between the adductor brevis and adductor magnus, as well as into the midportion of the adductor longus and adductor brevis muscles.

A convex ultrasound probe (frequency 2-5 MHz) was positioned at the patient's inguinal ligament, with one end directed toward the anterior inferior iliac spine (AIIS), clearly visualizing the bony prominences of the iliopubic eminence and the AIIS. The needle tip was directed medially toward the pectineus muscle. Upon reaching the space between the pectineus muscle and the pubic bone, and after confirming the absence of blood on aspiration, 30 ml of 0.375% ropivacaine was injected.

The percentage increase in adductor strength from preoperative to postoperative measurements divided by preoperative adductor strength is larger, reflecting a better nerve block effect and superior obturator nerve reflex inhibition.

Obturator nerve reflex grading system: No response in the adductor muscle group of the thigh; mild muscle twitching in the adductor muscle group of the thigh; severe contraction of the adductor muscle group of the thigh

Grading:

Excellent (1 point) Good (2 points) Fair (3 points) Poor (4 points) Higher scores indicate superior inhibition of obturator nerve reflex and better block efficacy