This is a prospective observational study conducted at the trauma center of Città della Salute e della Scienza of Turin. The aim of the study is to compare two local regional anesthesia techniques in multimodal analgesia for spine fusion: Intrathecal Morphine (IM) and the Erector Spinae Plane Block (ESPB). The effectiveness of these techniques is to be understood in terms of improved intraoperative and postoperative pain management.

Primary outcome:

● Assessment of postoperative pain upon awakening using the NRS score (T0). The secondary outcomes are aimed at investigating whether one technique is more effective than the other in terms of reducing postoperative opioid consumption and therefore improving pain control in the first 24 hours. Any side effects and complications related to the two techniques will also be analyzed.

Patients are enrolled by signing an informed consent form before surgery. At the time of surgery, an anesthesiologist experienced in locoregional techniques performs one of the two techniques (only those who have been specially trained can perform ESPB). A shared multimodal analgesia protocol is followed intraoperatively. In the postoperative period, standard analgesic therapy is set up and in the first 24 hours parameters, pain (NRS), any rescue medications administered and side effects and complications are recorded.

Inclusion Criteria:

• Age >=18 years
• Patients with surgical indication for thoracolumbar spinal fusion with posterior access.
• ASA I, II, III

Exclusion Criteria:

• Patient refusal
• Emergency surgery
• Chronic use (>12 weeks) of opioids in the preoperative period
• Drug addiction
• Contraindication to drugs contained in the protocol
• Contraindications to performing a subarachnoid puncture or fascial block

Patients with presenting surgical indication for thoracolumbar spinal fusion with posterior access. The patients enrolled are being treated at the CTO (Trauma and Orthopedic Center) hospital in Turin.