Position and anatomical landmarks
The patient is placed in a supine position with his hands under his head. The inguinal ligament and femoral artery are located and palpated. The insertion site is marked laterally to the femoral artery and 2.5 cm into the inguinal ligament.
The surrounding area is disinfected and covered with sterile drapes. A needle (22-G) is inserted (under ultrasound guidance). The thermocouple is connected to the needle. The location of the nerve is confirmed when the patient experiences reproducible paraesthesia in the upper leg by means of stimulation with 50 Hz, 0.5 V. Thereafter, a 45-V pulsed radio-frequency current lasting for 120 seconds is administered with no preceding local anaesthetic. The maximum temperature should not exceed 42°C, but if this occurs the output should be reduced. If necessary, a second treatment period of 120 seconds can be administered if the impedance is above 500 Ω, prior to injection of 1 ml NaCl 0.9% solution.
- The most serious complication after the injection is infection.
- Small subcutaneous bleedings may result in a temporary increase in pain after the injection.