Tegileridine for Postoperative Pain After Adolescent Scoliosis Surgery

The goal of this clinical trial is to see if a new pain medicine called Tegileridine is at least as effective as morphine (the standard treatment) for pain relief after spinal surgery in teenagers with scoliosis. This type of study is called a "non-inferiority" trial. The study will also carefully compare the safety of both medicines. The main questions it aims to answer are: Is Tegileridine no worse than morphine at controlling pain in the first 24 hours after surgery? How do the side effects (like sleepiness or nausea) of Tegileridine compare to those of morphine? Researchers will compare two different doses of Tegileridine against morphine. Neither the participants nor the doctors assessing them will know which medicine is being given. Participants in this study will: Receive one of the three pain medicine options through a pump (called a PCA pump) that they can control themselves after surgery. Use the pump for up to 48 hours. Regularly rate their pain levels using a simple number scale. Have their health closely monitored by the study team during this time.

Inclusion Criteria: * Aged 10 years to less than 18 years. * Scheduled to undergo posterior spinal fusion (PSF) surgery for scoliosis under general anesthesia. * American Society of Anesthesiologists (ASA) physical status classification I to III. * The participant and their parent or legal guardian voluntarily provide written informed consent prior to any study-related procedures. Exclusion Criteria: * History of difficult airway, severe respiratory depression (SpO₂ \< 90%), acute or severe bronchial asthma. * History of severe cardiovascular or cerebrovascular disease, such as myocardial infarction, unstable angina, second-degree or higher atrioventricular block, NYHA Class III or higher heart failure, or stroke. * Known or suspected gastrointestinal obstruction, including paralytic ileus. * Known hypersensitivity to opioids or any component of the study drug formulation. * History of psychiatric disorders (e.g., schizophrenia, depression) or cognitive impairment. * Diagnosis of neuromuscular scoliosis or presence of any other chronic pain condition that may interfere with postoperative pain assessment. * Chronic use of opioid analgesics or use of any analgesic medication within 48 hours prior to surgery. * Planned postoperative admission to the intensive care unit (ICU). * Any other condition deemed by the investigator to be inappropriate for participation in the study.