Study design and population
This single-armed prospective study was approved by the Ethics Committee of the Sixth People’s Hospital of Shanghai (reference No. 2021-095-(1)) and registered with the Clinical TrialRegistry of china (http://www.chictr.org.cn/; registration No. ChiCTR2100045439; date of registration, April 15, 2021; date of patient enrollment, April 16, 2021). All patients who underwent anterior cruciate ligament reconstruction were assessed for eligibility. All eligible patients obtained written informed consent. American Society of Anesthesiologists physical status I or II patients, in the age group of 18 to 60 yr, with a body mass index between 18 and 30kg/m2. We set exclusion criteria including local infection at the block site, preexisting neuropathy or coagulopathy, allergy to local anesthetics and opioids, dementia, known history of intravenous (IV) drug abuse, preoperative chronic opioid requirements, chronic pain, psychiatric illness, patients who failed to understand the scoring systems used in the study, uncontrolled hypertension or ischemic heart disease, renal or hepatic dysfunction, pre-existing neurologic deficits.