Prospective External Validation of an Early Prediction Model for Adverse Postoperative Pain Trajectories After Orthopedic Surgery

This prospective observational study will externally validate a previously developed and locked prediction model for identifying adult patients at risk of adverse postoperative pain trajectories after elective orthopedic surgery. Approximately 400 patients will be consecutively recruited at the First Affiliated Hospital of Chongqing Medical University. Postoperative pain will be assessed during the first 48 hours after surgery using the 0-10 Numeric Rating Scale. Pain scores will be organized into eight consecutive 6-hour time windows to determine each participant's postoperative pain trajectory according to prespecified rules. Clinical information available at the predefined prediction time point will be entered into the locked prediction model to calculate each participant's predicted probability of an adverse pain trajectory. The study will evaluate the model's discrimination, calibration, overall prediction performance, and potential clinical utility. The model will not be modified or retrained using data from this validation cohort. Individual prediction results will not be provided to patients or treating clinicians and will not be used to guide treatment during the study.