MLX/XLX ACR Expandable Lumbar Interbody Implants

Inclusion Criteria: 1. Patients who were ≥18 years of age at the time of surgery 2. Underwent spine surgery using either MLX or XLX ACR interbody implant (NuVasive, Inc., San Diego, CA) at: 1. One or two adjacent thoracic and/or lumbar levels for degenerative disc disease or degenerative spondylolisthesis, or 2. Any number of thoracic and/or lumbar levels for degenerative scoliosis (defined as \>10º coronal curve) 3. Interbody fusion with autograft and/or allograft (i.e., cancellous and/or corticocancellous allograft bone) 4. NuVasive supplemental internal fixation cleared by the applicable regulatory body for use in the thoracolumbar spine Exclusion Criteria: 1. Use of any bone graft with the associated interbody implant that is not FDA-cleared for use within interbody implants. Examples of these include: 1. Bone morphogenetic protein (BMP) (e.g., Infuse (Medtronic)) 2. Synthetic bone graft extenders (e.g., AttraX (NuVasive), Formagraft (NuVasive), Mastergraft (Medtronic), Vitoss (Stryker), Actifuse (Baxter), nanOss (RTI Surgical), Fibergraft (Prosidyan/Depuy Synthes), ChronOs (Depuy Synthes)) 3. Demineralized bone matrices (DBM) regulated as medical devices by the FDA (e.g., Grafton Putty/Gel (Medtronic), DBX (MTF/Depuy Synthes), Accell Evo3 (IsoTis), Propel Putty/Gel (NuVasive)) 4. Peptide enhanced bone graft (e.g., iFactor (Cerapedics)) 2. Previous lumbar fusion surgery at the currently treated level(s) (adjacent-level surgery is acceptable) 3. Systemic or local infection (latent or active) or signs of local inflammation documented at the time of surgery 4. Patient was involved in active litigation relating to the spine during the surgical/postoperative period (worker's compensation claim is allowed if it is not contested) 5. Inadequate bone stock or bone quality documented at the time of surgery 6. Known sensitivity to materials implanted documented at the time of surgery