Lumbar interbody fusion (LIF) is a surgical procedure used to treat conditions affecting the lumbar spine (lower back) such as degenerative disc disease, spondylolisthesis, or spinal instability.

During a lumbar interbody fusion, the surgeon accesses the spine through an incision in the lower back and removes the damaged disc or discs between two adjacent vertebrae. Once the disc is removed, the space between the vertebrae is typically filled with bone graft material, which promotes the fusion, or joining together, of the vertebrae.

In addition to bone graft material, the surgeon may also use implants such as cages, spacers, or rods to stabilize the spine and maintain proper alignment during the fusion process. Lumbar interbody fusion aims to relieve pain, restore stability, and maintain proper alignment of the lumbar spine.