The investigators aim to compare the postoperative analgesic efficacy of the classical thoracolumbar interfascial plane block and the Quadro-iliac plane block for postoperative analgesia management after lumbar disc surgery.

Lumbar spinal stenosis can lead to variable signs and symptoms such as back pain, radiating pain to the lower extremities, and reduced walking capacity. Lumbar disc surgery itself causes significant pain due to extensive dissection and muscle retraction during the procedure. A multimodal analgesic approach is preferred for postoperative pain management after lumbar spine surgery. The addition of regional anesthesia techniques can reduce opioid-related side effects and is associated with earlier mobilization, shorter hospital stay, and improved patient satisfaction.

For patients undergoing lumbar disc surgery, the classical thoracolumbar interfascial plane (TLIP) block and the Quadro-iliac plane block (QIPB) provide effective analgesia for postoperative pain control.

Inclusion Criteria:

• Patients aged 18-70 years,
• Classified as ASA physical status I-III,
• Scheduled to undergo single-level lumbar spinal surgery under general anesthesia
• Who agree to participate in the study by providing written informed consent

Exclusion Criteria:

• History of bleeding diathesis or current anticoagulant therapy
• Known allergy or hypersensitivity to local anesthetics or opioid medications
• Infection at the planned block injection site
• Previous lumbar spine surgery
• History of gabapentinoid or corticosteroid use within the last 3 weeks
• Inability to use a patient-controlled analgesia (PCA) device
• Suspected pregnancy, confirmed pregnancy, or breastfeeding
• Refusal to undergo the procedure or to participate in the study

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.