Posterior multi-level lumbar spinal instrumentation surgery is one of the most common surgeries performed for the treatment of leg and back pain. Pain management is especially important for these patients since chronic pain often occurs after surgery. Severe pain may occur at postoperative period in patients following spinal instrumentation operation. Postoperative effective pain treatment provides early mobilization and shorter hospital stay, thus complications due to hospitalization such as infection and thromboembolism may be reduced.

Opioids are one of the most preferred drugs among the analgesic agents. Parenteral opioids are generally performed for patients after surgery. However opioids have undesirable adverse events such as nausea, vomiting, itching, sedation and respiratory depression (opioid-related adverse events).

Various methods may be performed to reduce the use of systemic opioids and for effective pain treatment. US-guided interfascial plane blocks have been used increasily due to the advantages of ultrasound in anesthesia practice. TLIP block is one of these nerve blocks performed under US guidance and defined by Hand et al. in 2015. In this technique, local anesthetic solution is injected between the multifidus and logissimus muscles nearly at the level of the 3rd lumbar vertebra and targets the dorsal rami of the thoracolumbar nerves. However, the visualisation of this technique may be difficult under ultrasound (US) guidance. Therefore, Ahiskalioglu et al. defined modified-lateral technique of TLIP (mTLIP) block as a new approach. Ahiskalioglu et al. have reported that this approach has some advantages. Firstly, sonographic visualisation is more easily than the classical technique. Secondly, insertion of the needle from medial to lateral direction reduces the risk of possible neuraxial injection. It has been reported that this technique provides effective analgesia after lumbar spinal surgery.

The ultrasound (US) guided erector spina plane block (ESPB) is a novel interfacial plan block defined by Forero et al. at 2016 The ESPB contains a local anesthetic injection into the deep fascia of erector spinae. This area is away from the pleural and neurological structures and thus minimizes the risk of complications due to injury. Visualization of sonoanatomy with US is easy, and the spread of local anesthesic agents can be easily seen under the erector spinae muscle. Thus, analgesia occurs in several dermatomes with cephalad-caudad way. Cadaveric studies have shown that the injection spreads to the ventral and dorsal roots of the spinal nerves. ESPB provides thoracic analgesia at T5 level, abdominal analgesia at T7-9 level, and lumbar analgesia at T10-12, L3 level. In the literature, it has been reported that ESPB provides effective analgesia after lumbar spine surgery.

The aim of this study is to evaluate US-guided mTLIP block and ESPB compared to no intervention control group for postoperative analgesia management after multi-level (two or three level) lumbar spinal instrumentation surgery. The primary aim is to compare perioperative and postoperative opioid consumption and the secondary aim is to evaluate postoperative pain scores (VAS), motor blockade, the mobilization time, adverse effects related with opioids (allergic reaction, nausea, vomiting).