Blinding Method
Experienced anesthesiologists who had performed at least 100 ultrasound-guided femoral nerve block combined with sciatic nerve block using a high-frequency (6 to 13 MHz) ultrasound probe (Sonosite, Inc., USA) were responsible for performing all blocks. The procedural data was recorded by an independent investigator. The performers and the investigator did not further participate in the study. An independent observer evaluating the sensory and motor block was absent in the operating room during block placement and was blinded to the concentration of local anesthetic injected. The same observer followed up the patients postoperatively within the first 24hs.