Methods
postoperative pain
This randomized controlled study was carried out in a single institution and was approved by the Medical Ethics Committee of our hospital (KY2021PJ067). It was registered at 
Flow chart of the participantsStandard monitoring consisted of a 5-lead electrocardiogram (ECG), pulse oxygen saturation (SpO
Ultrasound image of anterior QLB. The arrow indicates the trajectory of the needle. QL, quadratus lumborum; PM, psoas major; ESM, erector spinae muscles; TP, transverse processAfter that, all patients were subjected to spinal anesthesia in the lateral position. An epidural needle was inserted at L2–L3 or L3–L4 intervertebral space. After reaching the epidural space, a spinal needle was inserted into the subarachnoid space through the epidural needle. A 0.75% ropivacaine (Naropin, AstraZeneca AB Company, Södertälje, Sweden) (1.1–1.8 mL) was administered to achieve a sensory block to the level of T10 dermatome. Then, a catheter was placed in the epidural space. Routine perioperative care was provided to all patients in the operating room. Parecoxib sodium (40 mg) was administered intravenously 15 min before the end of the surgery for postoperative analgesia. Intravenous patient-controlled intravenous analgesia pump with 7 mg/mL tramadol and 0.1 mg/mL tropisetron was administered to all patients. Other routine postoperative pain management consisted of parecoxib sodium (40 mg) twice daily. An intravenous dezocine (5 mg) was used for rescue analgesia if the VAS scores ≥ 4.