Proximal Junctional Kyphosis Following Long Instrumented Spinal Fusion: The Effect of Implant Selection

Inclusion Criteria: * Adult patients with degenerative spondylolisthesis with objective evidence of neurologic impairment, kyphosis, and failed previous fusion (pseudoarthrosis) requiring treatment with an instrumented posterior fusion from the thoracolumbar junction (T10-L1) to the sacrum * At least 18 years of age and maximum 70 years of age * Ability to provide Informed Consent for study participation and patients to return for all follow-up visits Exclusion Criteria: * Presence of systemic or localized infection * Previous fusion attempt at the involved level(s) * More than three previous open, posterior, lumbar spinal surgical procedures at the involved level(s) * Trauma at the levels to be fused * Previous documentation of osteopenia or osteomalacia * Diagnosis of a condition or requires postoperative medication(s), which may interfere with bony/soft tissue healing * Presence of a disease entity or condition which totally precludes possibility of bony fusion (e.g. metastatic cancer, HIV, long term use of steroids, etc.) * Immunosuppressive disorder * Pregnancy * History of alcohol and/or drug abuse * Any known allergy to a metal alloy * Mentally incompetent or prisoner * Currently a participant in another study * Preoperative structural deformity in the thoracic spine (kyphosis \>60 degrees, Coronal curve \>40 degrees) * Circumferential fusion above L1