MagnetOs Flex Matrix Compared to Trinity Elite Mixed With Local Autograft in Patients Undergoing up to Four-level Instrumented Posterolateral Fusion

Inclusion Criteria: * Patient is able to read/be read, understand, and provide written informed consent and has signed the Investigational Review Board (IRB) approved informed consent. * Male or female patient ≥ 18 years old. * Patients with leg pain, and/or back pain requiring up to four-level instrumented posterolateral lumbar/thoraco-lumbar fusion (T11 - S1) * Failed conservative treatment (physical therapy, bed rest, medications, spinal injections, manipulations, or transcutaneous electrical nerve stimulation) for a minimum period of 3 months prior to study enrollment. Exclusion Criteria: * Requires \> four-level fusion or expected to need secondary intervention within one year following surgery. * Had prior PLF fusion or attempted PLF fusion at the involved levels * Had previous decompression at the involved levels. * Women who are or intend to become pregnant within the next 12 months * To treat conditions in which general bone grafting is not advisable. * In conditions where the surgical site may be subjected to excessive impact or stresses, including those beyond the load strength of fixation hardware (e.g., defect site stabilization is not possible). * In case of significant vascular impairment proximal to the graft site. * In case of severe metabolic or systemic bone disorders (e.g., osteogenesis imperfecta or Paget's Disease) that affect bone or wound healing. * In case of acute and chronic infections in the operated area (soft tissue infections; inflammation, bacterial bone diseases; osteomyelitis). * When intraoperative soft tissue coverage is not planned or possible. * Receiving treatment with medication interfering with calcium metabolism. * Had leg pain, and/or back pain related to a benign or malignant tumor. * Had history or presence of active malignancy. * Has known substance abuse, psychiatric disorder, or condition which, in the opinion of the investigator, may influence the healing or ability to comply with protocol requirements. * Is involved in active litigation relating to his/her spinal condition. * Has participated in an investigational study within 30 days prior to surgery for study devices.