The goal of this clinical trial is to compare two different medications used to reduce pain during lower back fusion surgery. The main questions this study aims to answer are:

1. Can liposomal bupivacaine, when included in a regional anesthesia technique called the Erector Spinae Plane block (ESPB), reduce opioid use post-operatively compared to the standard medication typically used in an ESPB (bupivacaine with stabilizing agents)?
2. Do patients report lower pain and better satisfaction with their surgery when they receive liposomal bupivacaine in the ESPB compared to those that receive the standard medication?

Participants will be randomized to into two groups one that receives liposomal bupivacaine and one group that receives bupivacaine with stabilizing agents. Other than the randomization all patients will follow current standard of care at our hospital, and will not be asked to complete any additional study forms in addition to forms currently asked of all patients as per standard of care.

The purpose of this study is to improve pain management for patients having spine fusion surgery. This aim will be achieved by evaluating how well liposomal bupivacaine (LB), an FDA approved numbing medication that can provide pain relief for up to 72 hours after surgery, works when used as a single dose in a regional block known as Erector Spinae Plane block (ESPB). ESPB is a regional anesthesia technique used to control pain after surgery by injecting numbing medication around the patient's back bones on both sides. The study will compare how well LB in ESPB works compared to the standard practice procedure, which involves administering the traditional numbing medication (bupivacaine) through the ESPB. These two medications will be evaluated in reducing postoperative opioid medication need to control postoperative pain, as the primary goal. This study seeks to understand whether an ESP block either with bupivacaine and stabilizing agents or using liposomal bupivacaine, reduces the total amount of opioid medication used postoperatively, reduces pain scores, and leads to better patient reported outcome scores, patient satisfaction, and reduced recovery time in the PACU. Should the investigator find that liposomal bupivacaine is not superior to bupivacaine with stabilizing agents, this information would prove useful in regards to analgesic options for this patient population and could lead to a substantial cost savings.

Inclusion Criteria:

• Lumbar pathology requiring a single or two level elective posterior based (i.e. posterior or transforaminal approach) spine fusion with or without an interbody device.
• Surgical approach through either a midline or paramedian incision
• Primary fusion surgery, previous decompression surgery is acceptable
• American Society of Anesthesiologists (ASA) score of 1,2,or 3.

Exclusion Criteria:

• Patients currently on narcotic pain medication for pain management
• Patients with a history of illicit drug use
• Patients with neuromuscular disorders or neurological deficits (i.e. post polio or myasthenia gravis)
• Patients confined to a wheelchair for over 6 months
• Patients with fibromyalgia or other chronic pain disorder
• Patient with contraindications for use of the ESP block (i.e. local skin infection over the area of needle entry, or anaphylactic reaction to bupivacaine)
• Non-invasive surgical approaches
• Repeat or revision surgery
• Non-posterior spine surgical approaches (i.e. lateral, oblique, anterior, anterior and posterior approaches)
• Staged procedures
• Adjacent segment surgery
• Patients with a weight less than 40kg to avoid local anesthetic systematic toxicity.

No individual participant data will be shared as part of this study.

The patient, orthopedic surgeon (investigator or care provider), and outcome assessor performing data analysis will be blinded to this study. The regional anesthesia block is performed prior to surgical incision without the surgeon present, and thus the surgeon will be blinded to which formulation was provided. The patient will be informed that they are receiving a block but will not be informed until data collection is complete at the 3 month mark as to which group they were part of.

Non-blinded Parties: Due to differences in the physical appearance it is impossible to blind the anesthesia team (attending and fellow) performing the block, as the standard block is clear while the Exparel formulation is milky. However, after the regional block has been performed the regional team will have no further contact with the patient as per standard practice, and thus maintaining a separation between those blinded and not.