The aim of this dissertation is to improve perioperative management of adolescent patients undergoing posterior spinal fusion surgery. Posterior spinal fusion surgery is one of the most common major surgical procedures in adolescents. It is the main surgical procedure performed in adolescents with adolescent idiopathic scoliosis, Scheuermann kyphosis, or spondylolisthesis.

The first part of this thesis was a randomised, double-blinded, and placebo-controlled clinical trial of 64 patients. The purpose of the first study was to determine whether perioperative pregabalin reduces the persistent pain in adolescent patients after posterior spinal fusion for spinal deformities compared to placebo. The second and third part of this thesis were retrospective analyses of a prospectively collected paediatric spine register. In the second study, 159 consecutive adolescent idiopathic scoliosis patients undergoing posterior spinal fusion were screened to determine the predictors of postoperative urinary retention. The third part of this thesis included 158 adolescent idiopathic scoliosis, 19 Scheuermann kyphosis, and 36 spondylolisthesis patients undergoing posterior spinal fusion surgery, with the aim of evaluating the predictors of acute and chronic pain. In our first study, we showed that pregabalin did not affect the chronic postoperative pain two years after surgery, and there is no reason to combine pregabalin to a multimodal treatment protocol in adolescents undergoing posterior spinal fusion. In our second study, we revealed that postoperative opioid consumption after posterior spinal fusion was associated with an increased risk of postoperative urinary retention in adolescent idiopathic scoliosis patients, and multimodal pain management to reduce the opioid amount may be beneficial. The third publication of this thesis demonstrated that after posterior spinal fusion, acute postoperative pain was associated with more extensive tissue trauma (adolescent idiopathic scoliosis and Scheuermann kyphosis), and chronic pain was related to the disease pathology (spondylolisthesis). Multimodal analgesia may reduce the persistent pain, but an optimal treatment protocol is still not established, and more studies are needed.