Acute postoperative pain begins with surgical trauma and decreases with tissue healing. Untreatable postoperative pain is one of the most important problems due to the increase in respiratory, cardiac and thromboembolic complications. Lumber disc surgery is widely performed, and patients often complain of postoperative pain.

Preventing and managing postoperative pain after lumber disc surgery is very important for anesthetists. For this purpose, non-steroidal anti-inflammatory agents, intravenous opioids, preemptive analgesia methods, intravenous patient controlled analgesia methods and regional anesthesia techniques are used within the multimodal analgesia strategy.

Regional anesthesia techniques are becoming increasingly widespread due to their efficiency and increased applicability thanks to the use of ultrasonography. Regional anesthesia techniques used in lumber disc surgery include paravertebral block, local anesthetic infiltration, epidural analgesia, and erector spina plan block and modified thoracolumbar interfacial plan block in recent years.

The erector spina plane block was first described in 2016, and the thoracolumbar interfacial plane block in 2015, and its modification was developed in 2017. Although they vary depending on the level of application, they offer analgesic activity in a wide range. Although there are publications about the use of these blocks for postoperative analgesia after lumber surgeries, which block is more effective has not been investigated.

This study may contribute to the development of new options for pain management after lumber disc surgery by comparing erector spina plane block and modified thoracolumbar interfacial plane block, which have recently been used for postoperative pain treatment, with limited research, with each other and the standard technique, intravenous patient controlled analgesia, can add new applications to multimodal analgesia methods, increase patient satisfaction and contribute to the early recovery process.

The objective is to compare the erector spina plane block and modified thoracolumbar interfacial plane block in patients undergoing lumber disc surgery with intravenous patient-controlled analgesia in terms of analgesic efficacy.

Hypothesis The erector spina plane block and modified thoracolumbar interfacial plane block may decrease the postoperative pain scores, opioid consumption and time to first analgesic requirement compared with intravenous patient controlled analgesia.

Patients undergoing lumber disc surgery will be randomised into 3 groups. To receive either Erector spina plane block (ESP) or Modified thoracolumbar interfacial plane block (MTI) or Intravenous patient controlled analgesia IV-PCA.

Patients in the ESP and MTI groups will receive the blocks before anesthesia induction in the preoperative holding area.

All patients will receive IV-PCA with tramadol. Postoperative analgesia will be evaluated with a numeric rating scale at postoperative recovery room admittance, postoperative 1st , second, 4th, 12th and 24th hours both at rest and during movement.

Postoperative tramadol consumption and time to first tramadol demand will be determined.

Inclusion Criteria:

• Patients undergoing elective lumber discectomy or laminectomy
• Adults
• Aged 18-65
• America Society of Anesthesiologists physical status I-III

Exclusion Criteria:

• Emergency surgery
• Chronic pain condition
• Allergic to study drugs
• Recurrent surgical cases

Postoperative pain will be assessed by an anaesthesiologist unaware of group assignment