The effect of nalbuphine combined with ropivacaine on the analgesic duration of iliac fascia block in total knee arthroplasty under ultrasound guidance

INTERVENTION: Group N:Perform FICB under ultrasound guidance. The local anesthetic used is 30 ml of 0.33% ropivacaine plus 10 mg of nalbuphine injection.;Group R:Under ultrasound guidance, FICB was performed using 30 ml of 0.33% ropivacaine as the local anesthetic.; CONDITION: Osteoarthritis of knee PRIMARY OUTCOME: The sensory effect time of the femoral nerve and the lateral femoral cutaneous nerve;Duration of sensory perception of the femoral nerve and the lateral femoral cutaneous nerve;The total amount of 24h patient‐controlled intravenous analgesia pump used;Resting VAS score and passive movement VAS score were measured at 8h, 12h, 16h, 20h, 24h and 48h after surgery; SECONDARY OUTCOME: The first time to press the patient‐controlled intravenous analgesia pump;VAS scores at 8h (T1), 12h (T2), 16h (T3), 20h (T4), and 24h (T5) after completion of block;Number of cases requiring remedial analgesics within 24 hours after block (cases);HSS scores before operation, at 1 day and 5 days after operation;Time to get out of bed for activities; INCLUSION CRITERIA: 1. Patients diagnosed with knee osteoarthritis and scheduled for total knee arthroplasty (TKA) surgery; 2. Age between 65 and 85 years old, regardless of gender; 3. Body Mass Inde X(BMI) ranging from 18.5 to 30 kg/m^2; 4. American Society of Anesthesiologists (ASA) classification of grades I to III; 5. Voluntary and have signed the informed consent form.