The present study is a systematic review on the results and complications of intrathecal morphine injection in posterior fusion surgery of patients with idiopathic scoliosis. Scoliosis is a lateral curvature of the spine. Considering that complications after surgery are common in these patients, the present study was conducted with the aim of investigating the complications after posterior fusion surgery with instruments in adult patients with scoliosis of unknown cause. Most studies administered morphine under direct administration at the end of the procedure and before wound closure. In the present study, we administered morphine in the operating room before surgery and demonstrated the possibility of prophylactic analgesia through ITM at a dose of 0.3 mg. In a double-blind trial investigating prophylactic analgesia with low-dose intra spinal morphine in multilevel posterior-lumbar inter body fusion surgery, Wang et al. showed that prophylactic analgesia with intra spinal morphine led to a significant improvement in postoperative pain control and a reduction in the use of intrathecal analgesia. The vein is under the control of the patient after the operation, without increasing side effects. Patients undergoing lumbar spine surgery may experience significant pain in the early postoperative period, and poor pain control after multilevel lumbar spine fusion surgery is often associated with multiple complications and delayed hospital discharge. Posterior spine surgery can result in severe postoperative pain due to the extensive soft tissue incision and muscle dissection required to obtain adequate exposure of the laminae, facet joints, and transverse processes.