Evaluation of Fusion Rate Using K2M VESUVIUS® Demineralized Fibers With K2M EVEREST® Spinal System

Inclusion Criteria: * Diagnosis of non-cervical spinal stenosis; spondylolisthesis (grade 1 or 2); and/or degenerative disc disease (DDD) with one or two contiguous levels requiring surgical intervention between L1-S1. Qualified patients will be confirmed for inclusion by patient history and radiographic studies * Willing and able to comply with the requirements of the protocol including follow-up requirements * Willing and able to sign a study specific informed consent * Skeletally mature and I 18 years old at time of enrollment Exclusion Criteria: * Previous spine surgery at the index level * Previous posterior spine surgery (e.g., posterior decompression) that destabilizes the lumbar spine * Active systemic infection or infection at the operative site * Co-morbid medical conditions of the spine or upper/lower extremities that may affect the lumbar spine neurological and/or pain assessment * Metabolic bone disease such as osteoporosis and osteopenia that contradicts spinal surgery * History of an osteoporotic fracture * History of an endocrine or metabolic disorder (e.g., Paget's disease) known to affect bone and mineral metabolism * Taking medications that may interfere with bony/soft tissue healing including chronic steroid use * Known allergy to titanium or cobalt chrome * Rheumatoid arthritis or other autoimmune disease or a systemic disorder such as HIV, active hepatitis B or C, or fibromyalgia * Insulin-dependent type 1 or type 2 diabetes * Medical condition (e.g., unstable cardiac disease, cancer) that may result in patient death or have an effect on outcomes prior to study completion * Pregnant, or intends to become pregnant, during the course of the study * Severe obesity (Body Mass Index \> 40) * Physical or mental condition (e.g., psychiatric disorder, senile dementia, Alzheimer's disease, alcohol or drug addiction) that would interfere with patient self-assessment of function, pain, or quality of life. * Involved in current or pending spinal litigation where permanent disability benefits are being sought * Incarcerated at the time of study enrollment * Current participation in an investigational study that may impact study outcomes