Extreme lateral interbody fusion or XLIF (pronounced X-lif), also is a minimally invasive spine surgery designed to permanently fuse or join two levels of the lower spine by approaching the spine from the side. The same surgery is also known as Lateral Lumbar Interbody Fusion (LLIF) or Direct Lateral Interbody Fusion (DLIF). The surgery typically involves the removal of the problematic disc, and placement of a spacer such as a cage filled with bone graft into the disc space to promote fusion. XLIF is considered only after non-surgical treatments have failed.