Radical mastectomy is currently the mainstream surgical treatment for breast cancer. Patients often experience significant postoperative pain, and some may develop chronic pain. General anesthesia is commonly used, with remifentanil being the most frequently used intraoperative analgesic. However, prolonged high-dose use of remifentanil can induce opioid-induced hyperalgesia (OIH). Previous studies have shown that serratus anterior plane block can reduce acute postoperative pain after radical mastectomy, but it remains unclear whether it can reduce postoperative pain sensitization and the incidence of chronic pain. Liposomal bupivacaine is a new long-acting local anesthetic with an effect lasting up to 72 hours. This study aims to investigate the effect of liposomal bupivacaine serratus anterior plane block on postoperative pain sensitization and chronic pain in patients undergoing radical mastectomy, providing a reference for clinical treatment. The study includes 120 participants. A tactile measurement kit is used to measure the mechanical pain threshold around the surgical incision preoperatively and at 24 and 48 hours postoperatively, as well as postoperative persistent pain scores at 7 days, 1 month, 3 months, and 6 months. The data will then be analyzed to draw conclusions.