Randomization and blinding
RECRUITMENT
A computer-generated random allocation sequence was created by an independent investigator using SPSS Statistics (version 24.0, IBM Corp., Armonk, NY, USA) with a 1: 1 allocation and random block size. Recruitment was performed by the same investigator. After providing written informed consent, the participants were randomized to the FICB group and control group, using sealed opaque envelopes to reveal the treatment arm on the morning of surgery.None of the patients, anesthesiologists responsible for injection under the subfascial iliaca, or data collectors were aware of the grouping. Only one staff (Dr. Shen) among the researchers was aware of the grouping. Her task was to recruit and randomize patients and to assign study drugs to anesthesiologists based on the grouping.