BACKGROUND: Lumbar spondylolisthesis is a relatively common cause of low back and lower extremity pain. The most common type, degenerative lumbar spondylolisthesis (DLS), is a disease that causes stenosis of the spinal canal. Two surgical methods of treatment are widely accepted, namely posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF). MATERIALS AND METHODS: Between 2015 and 2017, the fi ndings of 333 consecutive DLS patients who underwent surgical decompression with instrumented fusion were analyzed in a prospective study at the