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.