A lumbar laminectomy with arthrodesis without instrumentation is a surgical procedure that involves removing portions of bones (vertebral segments) in the spine, and then using bone grafts to create a solid bony fusion across the unstable vertebral segments.
In patients with little or no instability, where the vertebrae, discs, and surrounding tissues fit tightly together, adding instrumentation is not necessary and the bone grafts can sufficiently stabilize the spine.