The following report is a systematic review of the indications and outcomes of lumbar spinal fusion used for either degenerative disc disease (DDD) and/or facet degenerative disease (DJD), leading to axial or mechanical low back pain, instability of the spine (including spondylolisthesis), spinal stenosis (leading to radicular leg pain or neurogenic claudication), and combinations of these symptoms with special attention to data from older adult populations, particularly those over 65 years of age.