Patients randomized into the liposomal bupivacaine group will receive anesthesia and undergo standard posterior spinal fusion surgery. The local infiltration would occur in a single stage, after instrumentation and correction maneuver is performed, just prior to closure of the deep fascial layer. The dose would be injected via multiple small volume injections into the paraspinal musculature, spaced approximately 1 cm apart.

Patients randomized into the 0.25% bupivacaine with epinephrine group will receive anesthesia and undergo standard posterior spinal fusion surgery under the same condition as the intervention group with one exception: the local infiltration will be made up of equal volume of 0.25% bupivacaine with epinephrine. The equal volume of 0.25% bupivacaine with epinephrine will be used in the exact same administration technique as the liposomal bupivacaine group, involving multiple small-volume injections to the paraspinal musculature spaced approximately 1 centimeter apart.

EXPAREL is a milky white too off-white aqueous suspension available as single-dose vials. Each mL contains 13.3 mg of bupivacaine, which is contained in multivesicular liposomes.

Total amount of morphine equivalents per kilogram during the first 72 hours postoperatively.

The average Numeric Rating Scale pain score (on a scale of 0-10) during the first 72 hours postoperatively will be computed from at most six values typically obtained every four to six hours following surgery. The higher the score, the higher the experienced pain of the individual.