The present invention includes a novel procedure and corresponding medical devices for a Percutaneous Posterior Lumbar Interbody Fusion (PePLIF). In PePLIF, the surgeon performs the entire operation percutaneously without the use of a microscope, endoscope, or magnifying loupes. An adjustable retractor system is disclosed that enables the surgeon to percutaneously perform the surgery through accessing the facet joint (and later disc space) that was created by said retractor system. This retractor system provides the surgeon a safe area to work and operate without fear of damaging nerves, blood vessels, or other tissue. An expanding trial may be inserted into and removed from the disc space through the interior of the retractor system to determine the proper size for the expandable cage. The retractor system also enables the expandable cage to be inserted into the disc space.