Multimodal Analgesia Versus Peripheral Nerve Block for Postoperative Pain Management After Lower Limb Injury Surgery

Study Design: This study was a prospective, randomized, controlled, comparative clinical trial with both participant and clinician blinding. This trial was designed to assess both the superiority and non-inferiority of different analgesic modalities in the management of postoperative pain following lower limb surgery. The study evaluated the effectiveness of femoral nerve block, combined sciatic and femoral nerve block, lumbar plexus block, epidural analgesia, and intravenous patient-controlled analgesia for patients undergoing procedures such as total knee replacement, knee arthroscopy, patella fracture repair, and pediatric femoral shaft fracture repair. Participants were recruited from Baogang Hospital, Inner Mongolia. This study received approval from the Medical Ethics Committee of Baogang Hospital, Inner Mongolia, and was conducted in accordance with the principles of the Declaration of Helsinki and the Consolidated Standards of Reporting Trials (CONSORT) guidelines. All participants provided informed written consent.

Patients：A total of 150 patients, classified as American Society of Anesthesiologists (ASA) physical status I, II, or III and aged 2 years or older, undergoing postoperative analgesia for lower limb injuries were recruited between February 2025 and May 2025. Participants were randomly assigned to one of five study groups, with 30 participants in each group.

Randomization and Blinding：This study employed block randomization to generate the random allocation sequence. A block size of 6 was set, and the random sequence was generated using dedicated software (the blockrand package in R version 4.3.2). The allocation of the random sequence was performed by an independent third party, and allocation concealment was implemented using sequentially numbered, sealed, opaque envelopes. The research team remained blinded throughout the randomization process and was not involved in the generation or allocation of the random sequence.

Intervention： Upon arrival to the operating room, patients will be monitored with electrocardiography, blood pressure, and pulse oximetry. Patients will be placed in the prone position with their arms abducted and internally rotated. Ultrasound guidance will be used for all regional anesthesia procedures (SonoSite Edge II; Fujifilm SonoSite, Bothell, WA, USA) with a linear 13-6 MHz ultrasound probe (HFL50x; Fujifilm SonoSite, Bothell, WA, USA). For each block, a 5 mL test dose will be injected initially, followed by observation for clinical signs of a successful block. After confirming correct placement, the remaining dose of the anesthetic agent will be injected. Following administration of the regional anesthesia, general anesthesia with endotracheal intubation will be performed. Anesthesia induction will be achieved using propofol (1.5-2 mg/kg i.v.), rocuronium (1-2 mg/kg i.v.), and fentanyl (1-2 μg/kg i.v.). Anesthesia will be maintained using sevoflurane or desflurane, with inhaled concentration adjusted based on Bispectral Index (BIS) monitoring. A continuous infusion of remifentanil (0.05-0.2 μg/kg/min) will be administered, with adjustments to maintain blood pressure and heart rate within ±20% of baseline values. Following induction, patients will be mechanically ventilated in pressure-regulated volume control (PRVC) mode. The ventilator (Aestiva; GE Healthcare, Waukesha, Wisconsin, USA) settings will be: tidal volume 6-8 mL/kg, positive end-expiratory pressure 0 cm H2O, inspiratory to expiratory ratio 1:2, respiratory rate 16 breaths per minute (BPM), and fraction of inspired oxygen 41%.

Femoral Nerve Block (FNB) Group: In the femoral nerve block (FNB) group, the femoral nerve was blocked distal to the inguinal ligament and lateral to the femoral artery. Under sterile conditions and ultrasound guidance using a short-axis out-of-plane approach, a 22-gauge insulated needle was advanced adjacent to the femoral nerve. Following confirmation of correct needle tip placement, a 20 mL volume of either 266 mg liposomal bupivacaine (diluted as indicated) or 0.2% ropivacaine was injected. This was followed by a continuous infusion at a rate of 5-10 mL/hr. For pediatric patients, a continuous infusion of 0.2% ropivacaine was administered at an initial bolus of 0.2-0.5 mg/kg, followed by a continuous infusion of 0.1-0.3 mg/kg/hr.

Combined Sciatic and Femoral Nerve Block (CS-FNB) Group: In the combined sciatic and femoral nerve block (CS-FNB) group, the femoral nerve block was performed as described above. The sciatic nerve block was performed at either the gluteal region or popliteal fossa. Under sterile conditions and ultrasound guidance using either an in-plane or out-of-plane approach, a 22-gauge insulated needle was advanced adjacent to the sciatic nerve. Following confirmation of correct needle tip placement, a 20 mL volume of either 266 mg liposomal bupivacaine (diluted as indicated) or 0.2% ropivacaine was injected. This was followed by a continuous infusion at a rate of 5-10 mL/hr. For pediatric patients, a continuous infusion of 0.2% ropivacaine was administered at an initial bolus of 0.2-0.5 mg/kg, followed by a continuous infusion of 0.1-0.3 mg/kg/hr.

Lumbar Plexus Block (LPB) Group: In the lumbar plexus block (LPB) group, the lumbar plexus was blocked paraspinally within the psoas muscle. Under sterile conditions, ultrasound guidance, or with the assistance of a nerve stimulator, using either an in-plane or out-of-plane approach, a 22-gauge insulated needle was advanced within the psoas muscle adjacent to the lumbar plexus. Following confirmation of correct needle tip placement, a 20 mL volume of either 266 mg liposomal bupivacaine (diluted as indicated) or 0.2% ropivacaine was injected. This was followed by a continuous infusion at a rate of 5-10 mL/hr. For pediatric patients, a continuous infusion of 0.2% ropivacaine was administered at an initial bolus of 0.2-0.5 mg/kg, followed by a continuous infusion of 0.1-0.3 mg/kg/hr.

Epidural Analgesia: For epidural analgesia, an initial bolus of 5-15 mL of 0.5% ropivacaine was administered followed by a continuous infusion of 0.2% ropivacaine at a rate of 3-10 mL/hr. For pediatric patients, an initial bolus of 0.2% ropivacaine at 0.5-1 mg/kg was administered, not exceeding a maximum total dose of 2-2.5 mg/kg, followed by a continuous infusion of 0.1-0.3 mg/kg/hr.

Intravenous Patient-Controlled Analgesia (PCA): For intravenous patient-controlled analgesia (PCA), fentanyl was administered at a dose of 2 mcg/kg, diluted in 100 mL of normal saline. The basal infusion rate was set at 2 mL/hr, with a PCA dose of 2 mL and a lockout interval of 15 minutes.

Outcomes and measures：Participants were followed up in the ward by two specially trained research nurses who were blinded to the participants' treatment group assignments. Outcome assessments were conducted at the following time points: prior to treatment (baseline), 2 hours postoperatively, 6 hours postoperatively, 12 hours postoperatively, and 24 hours postoperatively. These assessments were performed either in person or via telephone.