Comparing Ways to Freeze the Nerve That Provides Thigh Sensation

For the neurostimulation nerve injection technique, the initial puncture site will be located medial to the anterosuperior iliac spine, just caudal to the inguinal ligament \[7\]. The 22-gauge insulated needle will be connected to a stimulator set at a current of 1.5 mA, a pulse width of 300 ms and a frequency of 2 Hz. A paresthesia referred to the lateral aspect of the thigh at a minimal stimulatory threshold of 0.6 mA (0.3ms) will be sought prior to the injection of local anesthetic \[7\]. A total of 5cc of 2%Xylocaine will be injected for the nerve injection/anesthesia.

For the ultrasound nerve injection group, after skin disinfection, the inguinal region of patients will be scanned using a high-frequency (6 to 13 MHz) linear array transducer covered with a sterile plastic cover. An ultrasound image showing the inguinal ligament and anterior superior iliac spine (ASIS) will be obtained. Using an out-of-plane technique, a 22-gauge nerve block needle will be inserted 1-2 cm medial to ASIS. The needle will be advanced until its tip rests under the inguinal ligament, immediately ventral to the iliopsoas muscle \[6\]. A total of 5cc of 2%Xylocaine will be injected for the nerve injection/anesthesia.