The study aims to evaluate the effect of US guided bilateral Thoracolumbar Interfascial plane (TLIP) block performed at the level of the lumbar spine surgery (involving 1 up to 3 adjacent lumbar vertebrae) after induction of general anesthesia and before starting the surgery on postoperative opioid consumption by the patients during the first 24 hours postoperative.

Commonly performed spinal surgeries include laminectomies and discectomies, spinal fusions, and instrumentations, scoliosis corrections and spinal tumor excision. Conventional non-minimally invasive spinal surgeries usually involve extensive dissection of subcutaneous tissues, bones, and ligaments and thus can result in a considerable degree of postoperative pain. The severe pain typically last for at least 3 days with the highest pain scores recorded during the first 24 hours postoperative. Pain from the back originates from different tissues such as vertebrae & intervertebral discs, facet joint capsules, dura & nerve root sleeves, ligaments, fascia, and muscles, and it is directly proportional to the number of vertebrae involved in the surgery. Sensations from these structures are carried via the posterior rami of spinal nerves connected to sympathetic & parasympathetic nerves.

Adequate pain management in this period can result in improved functional outcome, early ambulation, early discharge, and preventing the development of chronic pain. Many options exist for this purpose, but each has its limitations and applications. The postoperative multi-modal analgesic approach to these patients include drugs like NSAIDs, acetaminophen, opioids, gabapentinoids and even corticosteroids, but using drugs alone for pain management in these patients can prove to be problematic due to side effects like GIT problems (NSAIDs), urinary retention, respiratory depression , nausea & vomiting (opioids), in addition, prescribing postoperative opioids will be more complicated if the patient was on prolonged preoperative opioid regimen (due to the associated opioid resistance), that's why patients on opioids prior to surgery reported more time postoperatively spent in severe pain (60% versus 38%; p=-0.002).

Multiple loco-regional techniques were explored to help supplement the multi-modal approach to decrease side effects, improve quality of postoperative analgesia, increase patient satisfaction after lumbar spine surgeries and also to be used in Enhanced Recovery After Surgery (ERAS) protocols which aims at minimizing opioid analgesics whenever possible. Via-Catheter techniques considered include patient-controlled epidural analgesia that showed promising results regarding pain control but concerns were raised due to its interference with postoperative assessment of neurological functions & voiding, in addition, it was opposed by many surgeons due to the fact of putting a catheter very near to the surgical field. Also continuous infusion of local anesthetics was explored which resulted in decreased postoperative opioid consumption but also raised concerns due to the catheter being placed very near to the wound.

Single injection methods that were explored in the literature include local anesthetic instillation of the affected nerve roots by the surgeon before wound closure, wound local anesthetic infiltration, and even a single low dose of intrathecal morphine administered by the surgeon into the intrathecal space under direct visualization at the conclusion of the surgery. But none of these methods was widely accepted due to limitations in the duration and adequacy of postoperative analgesia.

US guided Thoracolumbar Interfascial plane (TLIP) block is a novel technique first described in a pilot study on volunteers published by William R. Hand and colleagues in Nov 2015, it was designed to target the dorsal rami of the thoracolumbar nerves as they pass through the paraspinal musculature (between the multifidus muscle (MF) and the longissimus muscle (LG)), which is analogous to the Transversus Abdominis plane (TAP) block which targets the ventral rami of the thoracolumbar nerves (between the Transversus Abdominis muscle and the internal oblique muscle).

The block was performed bilaterally at the level of L3 and they reported a reproducible area of anesthesia to pinprick in a mean (SD) area covering 137.4 (71.0) cm2 of the lower back (including the midline) after 20 minutes of the block.

Multiple case reports for TLIP block in lumbar spine surgery were described afterwards, Hironobu Ueshima and colleagues described 2 cases that required no additional postoperative analgesia and no complications, then another 2 cases with nearly the same results, they conducted a cadaveric study to assess the spread of injectate within the plane between the MF and LG muscles using only 5ml of blue dye solution, they verified the spread of the dye to the transverse process of the 3rd lumbar vertebra (level of injection) in all cadavers, so they suggested that the local anesthetic's injectate into the fascial plane between the MF and LG muscles can indeed block the posterior rami of the lumbar nerves.

Finally they explored the continuous variation of the block in another 2 cases with reported pain free duration for 2 days (the duration of the study) and a pinprick anesthesia area covering from L1 to L4 level and no complications.

TLIP block has the potential benefit of blocking sensations from spinal and para-spinal structures involved in the surgical trauma up to 1 level above and below the level of the block (including deeper structures, not only skin and subcutaneous tissues, unlike simple wound infiltration), while also sparing neurological functions of the lower limb (specially the motor functions) and urinary bladder functions (Voiding).

Inclusion Criteria:

- Adult patients undergoing lumbar spine surgeries involving 1 up to 3 adjacent lumbar vertebrae (eg. laminectomy, discectomy …).

Exclusion Criteria:

• Patients on preoperative opioid regimen for more than 1 month.
• Patients with history of previous surgical operations in the lumbar region.
• Patients with spinal deformities (eg. Scoliosis…..).
• Hypersensitivity to Bupivacaine.
• Extensive Lumbar spine surgeries like large tumour excisions, scoliosis correction or more than 2 level spine fixation.
• Patients with communication difficulties.
• Lumbar spine operations that will be performed with the patient in any position other than the prone position.
• Severe neurological compromise (severe muscle weakness such as foot drop or sphincter disorders such as urinary incontinence).
• Coagulopathies with prothrombin concentration less than 60% or INR more than 1.5.
• In-ability to postpone anti-coagulation medications.
• Infection, injury or a lesion at the block site.
• ASA class 3 and 4 patients.