The present invention relates to stable fixation of spine segments, allowing for fusion in, e.g., skeletally mature patients. More particularly, the invention relates to a bone fixation device that can be affixed to vertebrae of a spine to provide reduction (or enlargement) capabilities and allow for fixation in the treatment of various conditions, including, e..g., spondyloslisthesis, degenerative disc disease, fracture, dislocation, spinal tumor, failed previous fusion, and the like, in the spine. The invention also relates to a method for delivering and implanting the bone fixation device.