A method for intra-operative surgical treatment of spondylolisthesis by an anterior minimally invasive approach of the lumbar spine includes inserting an interbody spacer between two vertebrae, attaching an anatomically designed reduction plate to at least one of the two vertebrae, and attaching the interbody spacer to the reduction plate by a fastening means through a central borehole of the reduction plate and the interbody spacer. The interbody spacer may be attached to the anteriorly positioned vertebra by at least bone screw. The upper and lower parts may be attached to the upper and lower vertebra by at least one bone screw to stabilize the displaced vertebral segment of the spine.