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

Inclusion Criteria: * Aged 18 to 90 years, regardless of sex. * Scheduled to undergo an eligible elective orthopedic surgical procedure at the First Affiliated Hospital of Chongqing Medical University. * Expected to remain hospitalized for at least 48 hours after surgery. * Conscious before surgery, with sufficient understanding and communication ability to understand and complete the 0-10 Numeric Rating Scale for pain. * Able and willing to provide written informed consent before any study-specific data collection. Exclusion Criteria: * Younger than 18 years or older than 90 years. * Emergency surgery, unplanned surgery, or a surgical procedure outside the prespecified orthopedic surgical scope of the study. * Unable to reliably understand the study or complete the Numeric Rating Scale because of impaired consciousness, severe cognitive impairment, psychiatric disorder, persistent deep sedation, mechanical ventilation, severe hearing impairment, language or communication difficulties, or similar conditions. * Lacks full capacity to provide valid informed consent. * Concurrent participation in another clinical study that may affect pain assessment, analgesic treatment, or study outcomes. * Expected discharge or transfer within 48 hours after surgery, or inability to complete the main study observation because of clinical circumstances. * Any other condition that, in the investigator's judgment, makes the patient unsuitable for participation in the study.