Role of Perineural Catheter in Pain Control and Opioid Consumption After Major Amputation of Lower Limb

The goal of this randomized controlled clinical trial is to evaluate the effectiveness of postoperative bupivacaine infusion through a perineural catheter in managing postoperative pain and to determine the opioid consumption among patients undergoing major lower-limb amputation surgery. The main questions it aims to answer are: * Does postoperative bupivacaine infusion through a perineural catheter provide better postoperative pain control as compared to intravenous opioid analgesia alone? * Does postoperative bupivacaine infusion through a perineural catheter reduce intravenous opioid consumption within the first 48 hours after surgery compared with intravenous opioid analgesia alone? * Does the postoperative Bupivacaine infusion through perineural catheter help in reducing the phantom pain at 6 months follow-up?