IV Methadone Vs EXPAREL Erector Spinae Plane Blockade in Pediatric Subjects Undergoing Idiopathic Scoliosis Correction

Inclusion Criteria: * Subjects whose parent(s) or guardian(s) has/have signed and dated the informed consent form (ICF) for the subject to participate in the study * Patients with a diagnosis of juvenile idiopathic scoliosis (JIS) or adolescent idiopathic scoliosis (AIS) who will have posterior spinal fusion surgery * Male or female patients 11 to less than 18 years of age on the day of surgery. * American Society of Anesthesiologists (ASA) Class 1-2. * Able to adhere to the study visit schedule and complete all study assessments. Exclusion Criteria: * Body mass index ≥35 at the time of screening * Contraindication to regional anesthesia (e.g., abnormal coagulation, infection at site) * Current opioid use at the time of screening * Current diagnosis of chronic pain * Allergy, hypersensitivity, intolerance, or contraindication to any of the study medications * Administration of liposomal bupivacaine (LB, Exparel) * Subject/parent/guardian primary language other than English or Spanish * Inability of patient to verbally express symptoms such as pain and side effects (as in moderate to severe developmental delay) * A prolonged QTc on preoperative EKG (QTc longer than 450 milliseconds) * History of Torsades de Pointes * Renal or hepatic impairment * Diagnosed active seizure disorder * Any other condition that causes patient to be ineligible for surgery, i.e. pregnancy.