This is a phase IV post-marketing study for MagnetOs Putty. MagnetOs Putty is a synthetic bone graft extender product that is routinely used by surgeons as a treatment for patients with leg pain and/or back pain and undergoing spinal fusion surgery.

In this study, MagnetOs Putty will be used according to the latest U.S. Instructions For Use, specifically as a bone graft extender mixed with autograft in a 1:1 vol.% in the posterolateral spine.

In this study, following a screening period of a maximum of 30 days, 30 patients will undergo up to a three-level instrumented posterolateral fusion (PLF) procedure. Prior to surgery, each patient will be randomized to receive MagnetOs Putty on the assigned side of the spine and local autograft bone on the other at the diseased levels. They will be followed up at discharge, Week 2, Week 6, Month 3, Month 6, and Month 12. An interim analysis will be performed once 15 patients have completed their Month 6 visit and have measurements for the endpoints available to measure effectiveness. The primary endpoint will be analyzed at Month 12.

In this study, MagnetOs Putty will be applied according to the latest Instructions for Use approved in the United States. Specifically, MagnetOs Putty will be used as a bone graft extender mixed with autograft in a 1:1 vol.% in patients with with leg pain and/or back pain requiring up to three-level instrumented posterolateral lumbar fusion procedure. The fusion procedure (PLF) will be left to the surgeon's discretion.

Radiographs will be obtained at Screening, Day 0, Week 6, Month 3. CT scans will only be obtained at Month 6 and Month 12.

Inclusion Criteria:

1. Patient is able to read/be read, understand, and provide written informed consent and has signed the Investigational Review Board (IRB) approved informed consent.
2. Male or female patient ≥ 18 years old.
3. Patients with leg pain and/or back pain requiring up to three-level instrumented posterolateral lumbar fusion (L2 - S1).
4. 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:

1. Requires > three-level fusion or expected to need secondary intervention within one year following surgery.
2. To treat conditions in which general bone grafting is not advisable.
3. 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).
4. In case of significant vascular impairment proximal to the graft site.
5. In case of severe metabolic or systemic bone disorders (e.g., osteogenesis imperfecta or Paget's Disease) that affect bone or wound healing.
6. In case of acute and chronic infections in the operated area (soft tissue infections; inflammation, bacterial bone diseases; osteomyelitis).
7. When intraoperative soft tissue coverage is not planned or possible.
8. Undergoing any procedure that allows MagnetOs to come in direct contact with the articular space.
9. Receiving treatment with medication interfering with calcium metabolism.
10. Women who are or intend to become pregnant within the next 12 months.